Mosaic arthroplasty in equine stifle and fetlock joints

Abstract

A kit of instruments for equine mosaicplasty carried out by placing an osteochondral graft into a targeted osteochondral region, said kit comprising - a drill (5) for drilling a graft recipient cavity into the targeted osteochondral region, - a drill guide (6) having a drill guiding portion (61) — having a cylindrical guiding hole (610) — and a bone-tissue engaging portion (62), - a dilator (7) for dilating the graft recipient cavity, - a measuring adjusting device (8) for depth measurement of the graft recipient cavity as well as aiding the cutting of the graft to the measured size, - a graft insertion guide (100), - a shaping cup (110) for the shaping distal end of the graft to the desired shape.

Description

[0001] Mosaic arthroplasty in equine stifle and fetlock joints

[0002] Technical background

[0003] Subchondral bone cysts (SBCs) and defects in weight-bearing articular cartilage are common conditions in equine athletes, often limiting performance [Jackson WA et al. 2000],1SBCs, also referred to as subchondral cystic or osseous cyst-like lesions, have a multifactorial etiopathogenesis involving osteochondrosis and trauma [Young N et al. 2023],2Although they frequently occur in the medial femoral condyle (MFC), they can manifest in various locations such as the distal epiphyses of the third metacarpal (MCIII) or metatarsal (MTIII) bone, proximal phalanx, proximal epiphysis of the middle phalanx, tibia, or radius [Bodo G et al. 2004],3Proinflammatory mediators produced by the fibrous cyst lining and increased intraosseal pressure are presumed to contribute to arthritis and pain [Klein CE et al 2022],4Prognosis is influenced by the anatomical location ofthe cyst, preexisting joint pathologies, and the chosen treatment strategy [Hogan PM et al. 1997],5

[0004] In young horses, some SBCs may resolve without treatment. Nonsurgical management, particularly for MFC SBCs, involving restricted exercise and intra-articular treatment, has been reported to alleviate lameness in 45%-64% of cases, although recurrence is common [Auer JA et al. 2018],6Numerous surgical interventions have been developed to treat SBCs, with success rates varying over the past decades, with age and concurrent osteoarthritis significantly impacting prognosis [Ortved KF et al. 2012] [Smith MA et al. 2005],78For instance, corticosteroid injection into the cyst lining under arthroscopic control successfully alleviated lameness in 77% of horses with a median age of 2 years at the time of surgery [Wallis TW et al. 2008],9Additionally, in a retrospective study, arthroscopic lesion debridement alone achieved a 69% success rate in horses aged <3 years, but only 35% of older horses became sound after the procedure [Smith MA et al. 2005],8Enlargement of the cyst cavity and meniscal injury following enucleation have also been reported [Wallis TW et al. 2008][Santschi EM et al. 2015],9 10Additionally, filling the cyst cavity with compacted cancellous osteochondral graft resulted in graft necrosis and cyst enlargement in 4 out of 5 horses in an experimental study [Jackson WA et al. 2000],1However, other authors reported a 74% favorable outcome with the implantation of growth factor-enhanced chondrocyte grafts following debridement, where age did not significantly affect the outcome [Ortved KF et al. 2012],7Furthermore, the application of parathyroid hormone peptide- enriched fibrin hydrogel (15 cases) or collagen sponge impregnated with bone morphogenetic protein 2 (three cases) to fill the debrided lesion result in promising outcomes, with success rates of 73% and 100%, respectively, mostly in animals aged <3 years [Jackson MA et al. 2007][Jackson MA et al. 2012],11 12Transcondylar screw placement is believed to improve the stress environment in trabecular bone and enhance bone healing.2This procedure has resulted in an overall success rate of 58%-75%, with outcomes appearing significantly worse in animals aged >3 years[Young N et al. 2023][Santschi EM et al. 2015],2 10Composite bioabsorbable implants were used from an extraarticular approach to treat SBCs in animals aged <2 years, leading to the alleviation of lameness in 94% of cases, with 71% of horses returning to racing post-surgery [Ravanetti P et al. 2021].13In a recent study involving 107 animals aged <2 years, no significant difference was found in outcome following treatment with cyst debridement, intralesional corticosteroids, or mesenchymal stem cells (68%-84%) [Klein CE et al. 2022],4

[0005] Subchondral cystic lesions in the distal metacarpus or metatarsus are common in young horses, predominantly affecting the central weightbearing surface of the condyles [Fortier LA 2005],14In a clinical report, 12 out of 15 horses were sound for intended use 4-6 months after debridement of the cyst cavity; however, follow-up radiographic examination revealed periarticular osteophyte formation in five cases and expansion of the cyst in some cases in one case.5Surgical options such as filling the lesions with compacted bone and chondrocyte grafts or using augmented bone substitutes have been reported to improve lameness and radiographic appearance of the cysts, although experience with these techniques is still limited [Jackson MA et al. 2012][Fortier LA 2005],12 14Differences in inclusion criteria and study populations, variable definitions of success, and a lack of information regarding the recurrence of lameness makes objectively comparing the outcomes of different surgical interventions challenging, with no technique consistently resulting in a superior outcome.

[0006] Articular cartilage defects are frequently encountered during arthroscopy, leading to pain and subsequent degenerative joint issues in both humans and equine patients[Frisbie DD et al. 2015][Frisbie DD et al. 2006],15 16Due to the lack of regeneration capacity of adult hyaline cartilage, addressing chondral and osteochondral weight-bearing articular cartilage injuries presents a significant challenge in orthopedic surgery[Hangody L et al. 2008][Nixon AJ et al. 2011].17 18Autologous osteochondral grafting, also referred to as mosaicplasty or autologous osteochondral transplantation, is an extensively used surgical intervention for treating focal full-thickness cartilage or osteochondral defects on weightbearing articular surfaces in human patients [Hangody L et al. 2008]17. This procedure involves harvesting multiple cylindrical osteochondral grafts from a less-weight-bearing articular surface and implanting them in a mosaic-like pattern to replace a focal lesion and restore the diseased weightbearing articular surface [Hangody L et al. 2008]17. Remarkable outcomes, reaching up to 93%, have been reported, accompanied by minimal long-term donor-site morbidity in a clinical study involving 1097 human patients [Hangody L et al. 2008],17

[0007] Osteochondral graft transplantation has been documented in equine cases to address subchondral cystic lesions in the tarsus, yielding favorable outcomes, as well as in experimental settings involving the third carpal bone and distal metatarsus [Pearce SG et al. 2003][Hurtig M et al. 2001][Janicek JC et al. 2010],19’20’21In experiments involving graft transplantation into the third carpal bone, good adaptation of the bone component was observed, albeit accompanied by a reduction in hyaline cartilage proteoglycan concentration was observed[Hurtig M et al. 2001],20

[0008] The mosaicplasty technique was adapted to equine stifles in 1998 and has since been continually refined and employed in clinical practice to address SBCs and full-thickness cartilage lesions in the stifle and fetlock joints[Bodo G et al. 2004][Bodo G et al. 2000],3 22Successful case reports concerning allograft transplantations have also been documented, enabling the use of numerous high-quality donor tissues from young individuals and eliminating potential donor-site morbidity [Pearce SG et al. 2003] [Pal Z et al. 2023],19,23

[0009] To the best of our knowledge, autologous or allogenous osteochondral transplantation remains the sole technique capable of replacing damaged or destroyed cartilage with hyaline or hyaline -like cartilage tissue on weight-bearing joint surfaces.

[0010] Mosaicplasty procedures tailored for equine application by the present inventor and his research group have evolved significantly over the last 25 years. For example, new chisels were customized for instrumentation originally designed for human, featuring diameters ranging from 2.7 to 8.5 mm diameter and lengths between 15 and 25 mm24— dimensions not suitable for equine use.

[0011] However, the methodology still faces with several difficulties today.

[0012] The present inventors have recognized that with minor modifications on osteochondral transplantation method and tools an improved method can be achieved.

[0013] Further developing the past 25 years results of this unique press-fit joint resurfacing technique, the present invention delineates the evolution and adaptation of mosaicplasty for equine applications.

[0014] DEFINITIONS

[0015] Osteochondral - As used herein, osteochondral relates to a part of the animal body composed of bone and cartilage preferably the cartilage and the underlying bone, and may relate to any or both of these component; wherein “composed of’ does not exclude the presence of other tissues as well.

[0016] Osteochondral defects (alternatively: lesions or injuries) may concern either the cartilage or the underlying bone or both, often starting from a defect of the cartilage and resulting in a complex injury concerning also the bone.

[0017] Graft - As used herein, is a small cylindrical plug of undamaged tissue extracted from a joint, consisting of a part of cancellous bone and a part of healthy cartilage.

[0018] Preferably the graft may have a diameter of 6 to 12 mm, preferably 6.5 to 10 mm and a length of 10 to 60 mm, preferably 20 to 50 mm However, the diameter and the length is finally defined by the need of the patient.

[0019] However, the skilled person will understand that other sizes may be appropriate depending on the size of the injured site, e.g. the length may be at least 5 mm or in special circumstances longer than 50 mm e.g. 60 or 70 mm and the diameter may a few mm like at least 3 or 4 or 5 mm or even up to 14 or 15 mm e.g. at large articular joints.

[0020] Cartilage cap - The cartilage part over the cancellous bone e.g. in a graft or in the tissue.

[0021] Mosaicplasty, mosaic arthroplasty - As used herein, is a form of osteochondral autograft transfer (OAT), which comprises the reconstruction of a joint with some form of cartilage defect, such as Subchondral Bone Cysts (SBC), via the transplantation of multiple grafts, harvested from a non -weightbearing area of the joint to the site of the cartilage defect. Fetlock - A joint of the horse's leg below the knee or hock and above the hoof.

[0022] Ungulates - Ungulates as used herein relates to relates to mammals which are members of the Ungulata family having hooves, preferably members having hooves, in particular large animals, which belong to any of two orders: Perissodactyla including equines, rhinoceroses, and tapirs; and Artiodactyla including cattle, antelope, pigs, giraffes, camels, sheep, deer, and hippopotamuses, among others.

[0023] Equine - Relating to or affecting horses or other members of the horse family (Equidae).

[0024] Proximal - As used herein, is the direction away from the surgeon executing an operation on a subject and towards the joint of the subject undergoing the operation, along the longitudinal axis of an instrument used in the operation.

[0025] Distal - As used herein, is the direction towards the surgeon executing an operation on a subject and away from the joint of the subject undergoing the operation, along the longitudinal axis of an instrument used in the operation.

[0026] Comprising - The term “comprises” or “comprising” or “including” are to be construed here as having a non — exhaustive meaning and allow the addition or involvement of further elements, e.g. features or method steps or members or components to anything which comprises the listed elements. “Comprising” can be substituted by “including” if the practice of a given language variant so requires or can be limited to “consisting essentially of’ if other elements than those listed are not essential to reduce the invention to practice or “consisting of’ in no other elements may be present.

[0027] The meaning of “composed of’ is the same as “comprising”, in its broader sense, however, with an emphasis on that the components listed from which the product is composed of are essential for the formation or architecture of the product; if further components are not essential the meaning of “composed of’ may be construed as “consisting essentially of’ with the emphasis on composition as mentioned.

[0028] Indefinite article - The singular forms “a”, “an” and “the”, or at least “a”, “an”, include plural reference unless the context clearly dictates otherwise.

[0029] BRIEF DESCRIPTION OF THE INVENTION

[0030] The invention relates to a kit of instruments for equine mosaicplasty carried out by placing an osteochondral graft into a targeted osteochondral region as defined in claim 1. Various preferred embodiments of the kit according to the invention are specified by the dependent claims. The invention further relates to a method for performing equine mosaicplasty. Various preferred embodiments of the method according to the invention are specified by the dependent claims.

[0031] The invention relates to a kit of instruments for mosaicplasty of ungulates having hooves, preferably equine mosaicplasty carried out by placing an osteochondral graft into a targeted osteochondral region, said kit comprising • a drill (5) for drilling a graft recipient cavity into the targeted osteochondral region, said drill (5) extending along a longitudinal axis between a proximal end (58) and a distal end (59) having a cutting head part (51) located at the proximal end (58), the cutting head part (51) being comprised within a cylindrical geometrical envelope surface (510) of a first diameter (D5), and a coupling end part (54) located at the distal end (59) of the drill (5),

[0032] • a drill guide (6) extending along a longitudinal axis between a proximal end (68) and a distal end (69) having:

[0033] - a drill guiding portion (61) having a cylindrical guiding hole (610) of the first diameter (D5) extending along the longitudinal axis of the drill guide, the drill guiding portion (61) being configured to guide the drill (5) in translation along the longitudinal,

[0034] - a bone-tissue engaging portion (62) located at said proximal end (68) having a sharpened edged rim perpendicular to the longitudinal axis configured to abut against the surface of the surgical site,

[0035] • a dilator (7) extending along a longitudinal axis between a proximal end (78) and a distal end (79) having a dilating portion (71) located at its proximal end (78) configured to be inserted into the drilled graft recipient cavity, wherein the kit further comprises

[0036] • a measuring adjusting device (8) for depth measurement of the graft recipient cavity as well as aiding the cutting of the graft to the measured size, said measuring adjusting device (8)

[0037] • a graft insertion guide ( 100) having a body (101) extending along a longitudinal axis between a proximal end (108) and a distal end (109) having

[0038] - a positioning resting surface (104) provided at said proximal end (108) configured to abut against a surface surrounding the drilled graft recipient cavity, and

[0039] - a graft guiding hole (102) extending coaxially with said longitudinal axis into which the graft can be slidably fitted,

[0040] • a shaping cup (110) in a cartilage -saving (soft) material, preferably plastic, configured to be mounted on the proximal end (78) of the dilator (7) and having a shaping surface (112) configured to contact the cap surface of the graft inserted into the graft recipient cavity, the shaping surface (112) being formed as a concave surface fitting to the cartilage surface, wherein the minimum diameter of the shaping cup is larger than the diameter of the graft,

[0041] • wherein the drill comprises:

[0042] - a narrowed portion (52) adjacent to the cutting head part (51) having a second diameter (D52) smaller than the first diameter (D5), the narrowed portion (52) being configured to accommodate the debris of a drilling operation,

[0043] - a guiding portion (53) located between the narrowed portion (52) and the distal end (59) of the drill (5), the guiding portion (53) having a cylindrical guiding surface of a diameter equal to the first diameter (D5), the guiding portion (53) being configured to be slidably and rotatably fitted within the drill guiding hole (610) of the drill guide (6).

[0044] In an alternative, the kit comprises at least

[0045] • the graft insertion guide ( 100) having a body (101) extending along a longitudinal axis between a proximal end (108) and a distal end (109) having

[0046] - a positioning resting surface (104) provided at said proximal end (108) configured to abut against a surface surrounding the drilled graft recipient cavity, and

[0047] - a graft guiding hole (102) extending coaxially with said longitudinal axis into which the graft can be slidably fitted,

[0048] • a shaping cup (110) in a cartilage -saving (soft) material, preferably plastic, configured to be mounted on the proximal end (78) of the dilator (7) and having a shaping surface (112) configured to contact the cap surface of the graft inserted into the graft recipient cavity, the shaping surface (112) being formed as a concave surface fitting to the cartilage surface, wherein the minimum diameter of the shaping cup is larger than the diameter of the graft,

[0049] • wherein the drill comprises:

[0050] - a narrowed portion (52) adjacent to the cutting head part (51) having a second diameter (D52) smaller than the first diameter (D5), the narrowed portion (52) being configured to accommodate the debris of a drilling operation,

[0051] - a guiding portion (53) located between the narrowed portion (52) and the distal end (59) of the drill (5), the guiding portion (53) having a cylindrical guiding surface of a diameter equal to the first diameter (D5), the guiding portion (53) being configured to be slidably and rotatably fitted within the drill guiding hole (610) of the drill guide (6).

[0052] In a further alternative embodiment the kit of the invention comprises at least

[0053] • a dilator (7) extending along a longitudinal axis between a proximal end (78) and a distal end (79) having a dilating portion (71) located at its proximal end (78) configured to be inserted into the drilled graft recipient cavity, and

[0054] • a shaping cup (110) in a cartilage -saving (soft) material, preferably plastic, configured to be mounted on the proximal end (78) of the dilator (7) and having a shaping surface (112) configured to contact the cap surface of the graft inserted into the graft recipient cavity, the shaping surface (112) being formed as a concave surface fitting to the cartilage surface, wherein the minimum diameter of the shaping cup is larger than the diameter of the graft, and preferably,

[0055] • a graft insertion guide ( 100) having a body (101) extending along a longitudinal axis between a proximal end (108) and a distal end (109) having

[0056] - a positioning resting surface (104) provided at said proximal end (108) configured to abut against a surface surrounding the drilled graft recipient cavity, and - a graft guiding hole (102) extending coaxially with said longitudinal axis into which the graft can be slidably fitted.

[0057] Preferably the shaping cup (110) has a concave shaping surface (112) having a radius essentially identical with the hyaline cartilage to be treated, preferably a radius of 70 to 90 mm, preferably 75 to 85 mm, more preferably 78 to 82 mm, in particular 80 mm.

[0058] In a preferred embodiment the shaping cup is made of a plastic material which upon shaping the articular surface, preferably the hyaline surface, is useful to safely avoid any injury, e.g. scrap or break on the cartilage surface.

[0059] In a preferred embodiment the shaping cup (110) is made of a plastic material.

[0060] Preferably the plastic material is made of a material which safely avoids an injury on the cartilage surface. / / /

[0061] Preferably the kit further comprises

[0062] • a measuring adjusting device (8) for depth measurement of the graft recipient cavity as well as aiding the cutting of the graft to the measured size, said measuring adjusting device (8)

[0063] In a preferred embodiment the graft insertion guide (100) also comprises a window (103) formed in the vicinity of the proximal end (108),

[0064] In a preferred embodiment the invention relates to a kit, wherein the measuring adjusting device (8) comprises

[0065] - a measuring rod (80) extending along a longitudinal axis between a distal end (808) and a proximal end (809) provided at its proximal end (809) with an abutment surface (802) configured to abut against the bottom surface of the graft recipient cavity and a graft holding surface (804) provided at its distal end (809), the measuring rod having an outer guiding surface (803), wherein at least a portion of the outer guiding surface (803) is configured to be fitted in the drilled graft recipient cavity,

[0066] - a tubular measuring sleeve (90) extending along a longitudinal axis between a proximal end (908) and a distal end (909), the tubular measuring sleeve (90) comprising a guiding through hole, wherein a graft can be slidably fitted in at least a section of the guiding through hole extending from the distal end (909) of the measuring sleeve (90), an abutment surface (901) provided at its proximal end (908) configured to abut against a surface surrounding the drilled graft recipient cavity, and a cut guiding surface (902) provided at its distal end (909) configured to guide a cutting device for cutting the graft fitted into the measuring sleeve (90), wherein the measuring rod (80) is slidably guided within the guiding through hole of the measuring sleeve (90),

[0067] - the measuring sleeve (90) further comprising a securing means (85) for securing the measuring rod (80) at a desired position with respect to the measuring sleeve (90). In a preferred embodiment the measuring sleeve (90) of the measuring adjusting device (8) is provided with a graduated slot (903) extending from its distal end (909).

[0068] In an embodiment the invention relates to said measuring adjusting device (8).

[0069] In an embodiment the invention relates to a drill (5) for drilling a graft recipient cavity into the targeted osteochondral region, said drill (5) extending along a longitudinal axis between a proximal end (58) and a distal end (59) having a cutting head part (51) located at the proximal end (58), the cutting head part (51) being comprised within a cylindrical geometrical envelope surface (510) of a first diameter (D5), and a coupling end part (54) located at the distal end (59) of the drill (5), wherein the cutting head part (51) of the drill (5) is three-fluted, each flute being formed as a wing (511) radially extending from the longitudinal axis of the drill (5), the wing (511) having a lateral surface (512) extending between a base edge (512) and a top edge (514) inclined with respect to the longitudinal axis of the cutting head part 51 by an angle comprised between 3°and 20°, preferably comprised between 5° and 15°.

[0070] In a preferred embodiment the invention relates to a kit comprising said drill (5) and

[0071] • a drill guide (6) extending along a longitudinal axis between a proximal end (68) and a distal end (69) having:

[0072] - a drill guiding portion (61) having a cylindrical guiding hole (610) of the first diameter (D5) extending along the longitudinal axis of the drill guide, the drill guiding portion (61) being configured to guide the drill (5) in translation along the longitudinal,

[0073] - a bone-tissue engaging portion (62) located at said proximal end (68) having a sharpened edged rim perpendicular to the longitudinal axis configured to abut against the surface of the surgical site,

[0074] In a preferred embodiment in any of the kit of the invention the cutting head part (51) of the drill (5) is three-fluted, each flute being formed as a wing (511) radially extending from the longitudinal axis of the drill (5), the wing (511) having a lateral surface (512) extending between a base edge (512) and a top edge (514) inclined with respect to the longitudinal axis of the cutting head part 51 by an angle comprised between 3°and 20°, preferably comprised between 5° and 15.

[0075] Preferably, the lateral surface (512) of the wing (511) of the cutting head part (51) is a planar surface defined by the base edge (512) and the top edge (514) each being straight edges.

[0076] In a preferred embodiment in any of the kit of the invention the shaping cup (110) has a concave shaping surface (112) having a radius essentially identical with the hyaline cartilage to be treated, preferably a radius of 70 to 90 mm, preferably 75 to 85 mm, more preferably 78 to 82 mm, in particular In a preferred embodiment of the invention the drill guide (6) and the graft insertion guide (100) are each provided with a respective stylet (63,105) extending in a transverse direction with respect to the longitudinal axis of the drill guiding hole (610) and the graft guiding hole (102).

[0077] Preferably, the drill guiding portion (53) of the drill (5) is graduated.

[0078] In a preferred embodiment the kit also comprises a measuring adjusting device (8) as defined herein wherein the measuring sleeve (90) of the measuring adjusting device (8) is provided with a graduated slot (903) extending from its distal end (909).

[0079] In a preferred embodiment in any of the kits of the invention the dilating portion (71) of the dilator (7) has a dilating ratio of 0.4 mm / 9 mm, the dilating ration being defined as the ratio of the total diameter increase along the length of the dilating portion (71) to the length of the dilating portion (71).

[0080] In a further preferred embodiment the kit further comprises a tubular chisel (2) extending along a longitudinal axis between a proximal end (28) and a distal end (29), the chisel (2) having a graft accommodating portion (22) extending from its proximal end (28) and a cutting edge (21) provided at its proximal end (28), the cutting edge (21) having an inner angle comprised between 5° and 45°, preferably between 10° and 20°.

[0081] In a preferred embodiment the kit further comprises a chisel tamp (3) extending along a longitudinal axis between a first end (38) and a second end (39), and a chisel protection cup (4) extending along a longitudinal axis between a first end (48) and a second end (49), the chisel protection cup (4) being provided with a first receiving hole (41) extending from its first end (48) and with a guiding hole (42) extending from its second end (49), wherein the portion of the chisel (2) extending from its proximal end (28) is configured to be received in the first receiving hole (41) of the chisel protection cup (4) and the chisel tamp (3) is configured to be inserted and guided from its first end (38) in the guiding hole (42) of the chisel protection cup (4).

[0082] In another embodiment the invention relates to a method for performing equine mosaicplasty in a weight-bearing articular cartilage in an equine animal, using the kit of any of claims 1-12, said method comprising:

[0083] • determining a osteochondral region to be repaired,

[0084] • providing and preparing an osteochondralosteochondral graft,

[0085] • cutting the cartilage layer (cap) corresponding to said determined osteochondral osteochondral region by

[0086] - abutting the bone-tissue engaging portion (62) of the drill guide (6) perpendicularly against the surface of said determined osteochondral region to be repaired and - sinking said bone-tissue engaging portion (62) into the corresponding cartilage portion preferably thereby cutting the sharped edged rim into the cartilage layer thereof,

[0087] • drilling a graft recipient cavity of a desired depth based on the determined osteochondral region to be repaired, wherein drilling the graft recipient cavity comprising:

[0088] - fitting the drill (5) into the drill guiding portion (61) of the drill guide (6),

[0089] - driving the drill (5) into said determined osteochondral region until a desired depth,

[0090] - wherein the drill (5) is guided with respect to the drill guiding hole (610) of the drill guide (6) by the guiding portion (53) of the drill (5),

[0091] - optionally (if required) evacuating the drill waste from the cutting head part (51) of the drill (5) by transporting it toward the narrowed portion (52) of the drill (5) adjacent to the cutting head part (51),

[0092] • dilating the drilled graft recipient cavity by inserting the dilating portion (71) of the dilator (7) into the graft recipient cavity until the proximal end (78) of the dilator (7) abuts against the bottom of the graft recipient cavity, maintaining the dilating portion in this inserted state for a predetermined period of time,

[0093] • measuring the depth of the drilled graft recipient cavity by

[0094] - fitting the measuring rod (80) of the measuring adjusting device (8) into the graft recipient cavity, until the abutment surface (801) of the measuring rod (80) abuts against the bottom of the graft recipient cavity,

[0095] - engaging and sliding down the measuring sleeve (90) on the measuring rod (80) until the abutment surface (901) of the measuring sleeve (90) abuts against a surface surrounding the drilled graft recipient cavity,

[0096] - securing the measuring sleeve (90) with respect to measuring rod (80) by means of the securing means (85),

[0097] - determining the depth of the graft recipient cavity,

[0098] - removing the measuring sleeve (90) from the graft recipient cavity,

[0099] • cutting the graft at the measured length by

[0100] - fitting the graft within the measuring sleeve (90) from the distal end (909) thereof until it abuts against the graft holding surface (804) of the measuring rod (80),

[0101] - cutting the graft to size by guiding a cutting device at the cut guiding surface (902) of the measuring sleeve (90),

[0102] • inserting the graft into the graft recipient cavity by

[0103] - fitting the graft within the graft guiding hole (102) of the graft insertion guide (100),

[0104] - abutting and positioning the graft insertion guide (100) by means of its positioning resting surface (104) provided at its proximal end (108) against the surface surrounding the drilled graft recipient cavity, -guiding the graft within the graft insertion guide in translation toward the graft recipient cavity, until the graft is inserted in the graft recipient cavity in a position in which the distal end of the graft protrudes from the bone surface of a given distance,

[0105] -removing the graft insertion guide,

[0106] • positioning and shaping the protruding surface of the graft with respect to the surrounding surface by mounting the shaping cup (110) on the proximal end (78) of the dilator (7),

[0107] - positioning the shaping surface (112) of the shaping cup (110) on the protruding distal surface of the graft,

[0108] - gently hammering the graft cap into the surface by hammering the shaping cup (110) mounted on the dilator (7) until the distal surface of the graft is in flush mate with the surrounding bone surface and the graft distal end is shaped at the desired shape, wherein the distance between the graft cap and the graft insertion cavity is visualized through the window (103) of the graft insertion guide (100).

[0109] Preferably, the drill (5) is guided with respect to the drill guide (6) by the guiding portion (53) and at least a part of the cutting head part (51).

[0110] Preferably, the drill waste is stored in the space formed between the narrowed portion (52) and the surface of the drill guiding hole (610) of the drill guide (6).

[0111] In a preferred variant of the method of according to the invention, in particular according to any of the previous paragraphs, the graft is inserted into the graft insertion device (100) with the graft cap facing in the direction of the distal end (109) and then the graft is gently hammered down into the channel using the proximal end (78) side of the dilator (7) until the graft cap protrudes preferably just one mm above the surface.

[0112] Preferably, the graft is further pushed down, optionally gently hammered down, by the shaping cup (110) of a cartilage-saving (soft, preferably plastic) material, said shaping cup (110) having a shaping surface (112) configured to contact the cap surface of the graft inserted into the graft recipient cavity, wherein the minimum diameter of the shaping cup is larger than the diameter of the graft, the shaping surface (112) being formed as a concave surface fitting to the cartilage surface, thereby forming an even surface on the injured cartilage area.

[0113] Preferably, said shaping cup is configured to be mounted on the proximal end (78) of the dilator (7).

[0114] In a highly preferred embodiment, the shaping cup (110) has a concave shaping surface (112) having a radius essentially identical with the hyaline cartilage to be treated, preferably a radius of 70 to 90 mm, preferably 75 to 85 mm, more preferably 78 to 82 mm, in particular 80 mm.

[0115] Preferably said shaping cup (110) is made of plastic. In an embodiment the graft is an artificial graft having a shape essentially identical to that of the present invention.

[0116] A material with hardness similar to cartilage can be achieved through hydrogels, particularly those incorporating polymer networks like PVA or PHEMA or a PVA / PAMPS hydrogel has shown cartilage- equivalent strength and modulus in tension and compression. Also, a PHEMA / glycerol synthetic gel has demonstrated hardness close to natural cartilage. See e.g. [Ma R, et al. 2009][Yang, Feichen et al., 2020], Mostakhdemin, M et al. give a review on artificial cartilage graft materials [Mostakhdemin, M. et al. 2021],

[0117] In a further embodiment such artificial grafts are disclosed in W02023205127A1 [Grunlan, M.A. ET AL., 2023] and in US11707554B2 [Grunlan, M.A. ET AL., 2020],

[0118] BRIEF DESCRIPTION OF THE FIGURES

[0119] Figure l.A Improved instrument kit according to the invention (toolbox) (for a cavity of 8.5 mm diameter in the present example)

[0120] Figure l.B Previous prior art mosaicplasty instrument kit (for a cavity of 8.5 mm diameter).

[0121] 1 = drill guide, (1 = 50 mm, d = 9. 1 mm),

[0122] 2 = dilator, (1 = 185 mm, d = 8.5-8.9 mm),

[0123] 3 = chisel guard (chisel protection cup),

[0124] 4 = harvesting chisel, (1 = 130 mm, d = 8.5 mm),

[0125] 5 = measuring adjusting device, (1 = 120 mm, d = 9.3-8.5 mm),

[0126] 6 = delivery tamp (1 = 140 mm, d = 8.3 mm),

[0127] 7 = drill bit (1 = 88 mm, d = 8.5 mm).

[0128] Manufacturer: Metrimed Kft. 1, length; d, diameter.

[0129] Figure 2.A Chisel (tubular), side view

[0130] Figure 2.B Chisel (tubular), cross-section

[0131] Figure 2.C Chisel (tubular), enlarged cross-sectional view of the cutting edge at first end portion. Figure 3 Chisel tamp

[0132] Figures 4.A, 4.B, 4.C Chisel protection cup in a front view, cross-sectional view and perspective view Figure 5.A Drill according to the invention - Schematical 3D figure of the drill for use in cartilage and bone tissue to prepare holes for the graft.

[0133] Figure 5.B Drill according to the invention - Schematical side view of the drill for use in cartilage and bone tissue to prepare holes for the graft.

[0134] Figure 5.C Preferred embodiment of the drill according to the invention, side view, the drill being provided with a preferred embodiment of the cutting head part.

[0135] Figure 5.D Preferred embodiment of the drill according to the invention in perspective view, the drill being provided with a preferred embodiment of the cutting head part.

[0136] Figure 6 Drill guide with stylet

[0137] Figure 7. Dilator

[0138] Figures 8.A, 8.B Measuring adjusting device according to the invention

[0139] Figures 9.A, 9.B Measuring adjusting device according to the invention with freshly harvested osteochondral grafts 8.5 mm in diameter.

[0140] Figure 10.A Graft insertion guide with stylet

[0141] Figure 11 Shaping cup for graft insertion -

[0142] Figures 12.A, 12.B. Intraoperative images of Horse 8. An extensive lesion is visible on the right medial femoral condyle (A). Six grafts were implanted into the surface in a mosaic-like pattern (B). The additional holes were drilled adjacent to the first hole, and the procedure was repeated until the cyst cavity was completely filled. The implants were positioned adjacent to each other or several millimeters apart.

[0143] Figures 13.A, 13.B . Intraoperative images of Horse 6 show the medial femoral condyle exposed from an arthrotomy incision before (A) and after (B) implantation. Star-shaped opening of the cyst is visible (A).

[0144] In two cases, an attempt was made to reconstruct the focal full -thickness cartilage loss of the large (6-8 cm2) weight-bearing surfaces of the MFC. The same implantation technique was used in these patients, with numerous (six pieces) short (15-20 mm in length) osteochondral grafts inserted in a mosaic -like pattern.

[0145] Figure 14. Radiographs of the left stifle of Horse 11. Caudocranial preoperative radiograph (A) with a cystic lesion in the medial femoral condyle (white arrow). Postoperative caudocranial (B) and caudolateral-craniomedial oblique (C) radiographs taken 8 weeks (B) and 5 years (C) post-implantation, demonstrating the disappearance of the medial femoral condyle cyst.

[0146] Figure 15. Graft harvest procedure. (A) The chisel is inserted on the articular surface. (B) The chisel is driven to the desired depth. (C) Semi-circular movement of the instrument is applied to detach the graft. (D) Osteochondral graft following harvest.

[0147] Figure 16 Graft implantation procedure. (A) Subchondral bone cyst. (B) Drilling the cyst cavity. (C) Dilator tamp applied to dilate the drilled hole. Black arrows indicate force acting on the host bone during dilation. (D) Implantation of the graft to fill the drilled hole. (E) Host bone engaging the graft. Black arrows indicate force acting on the implanted graft.

[0148] DETAILED DESCRIPTION OF THE INVENTION

[0149] Significant differences exist between human and equine surgical procedures during the postoperative convalescence period. Although human patients typically undergo 4 weeks of non-weightbearing convalescence [Brittberg M et al. 2010]24, immediate loading of the transplanted site is unavoidable in horses post-recovery. This exerts extreme stress on the surgical site, necessitating the use of highly stable grafts on the host bed.

[0150] Moreover, another significant and unrecognized problem is the injury of the newly formed hyaline cartilage surface . In human mosaicplasty the grafts are easily placed and the formation of hyaline surface is not of utmost importance. Quite often the surface of the grafts lies deeper than the hyaline surface. This is not satisfactory for equine patients: not just because the load after surgery is immediate and significantly higher than in case of humans but because even minor injuries may lead to problems like cysts. in the osteochondral tissue.

[0151] ICRS classification system [Brittberg et al. 2000]

[0152] Category Description of category

[0153] ICRS 0 Normal hyaline cartilage

[0154] ICRS 1 A es B Near-normal surface, superficial lesion, soft sedimentation (A) and / or superficial crack in the hyaline cartilage surface layer (B)

[0155] ICRS 2 Abnormal cartilage surface, the depth of the lesion in relation to the thickness of the cartilage is less than 50%.

[0156] ICRS 3 Severely abnormal cartilage surface, the cartilage defect extends deeper than 50% of the thickness of the hyaline cartilage.

[0157] ICRS 4 Severely abnormal cartilage surface, the lesion extends into the subchondral bone.

[0158] Mosaicplasty procedures tailored for equine application by the last author (G. B.) and their research group have evolved significantly over the last 25 years. Over the past decades, there has been a trend towards larger individual graft sizes accompanied by a reduction in their total number to enhance stability and nutritional support. Initially, grafts measuring 6.5 mm in diameter and 30-40 mm in length were employed. Two years later, 8.5 mm grafts were introduced. More recently, grafts measuring 8.5 mm or even 10 mm in diameter have been implanted centrally, with smaller grafts added subsequently. The advantage of smaller grafts lies in their ability to produce more pieces from the same donor site, thereby resulting in smaller tissue defects and improved surface congruency. Nevertheless, larger grafts offer enhanced stability and potentially receive improved nutrition from the host bone due to their larger contact interfaces. The present inventors have experienced that grafts with an 8.5mm diameter provide excellent surface congruency. Our current protocol involves initially drilling the center of the defect, then removing any remaining cyst lining, and visualizing the drilled canal arthroscopically. Subsequently, the first large central graft is inserted. Depending on the lesion conformation, additional tunnels were drilled around the primary lesion, and extra grafts were implanted to achieve surface congruency. Typically, one large and one small graft are sufficient for insertion into smaller cysts.

[0159] The importance of precise perpendicular drilling of the joint surface during the procedure cannot be overstated.

[0160] Specifically, new chisels were customized for instrumentation originally designed for human, featuring diameters ranging from 2.7 to 8.5 mm diameter and lengths between 15 and 25 mm24— dimensions not suitable for equine use. The blade configuration at the chisel tip was specifically designed to effectively separate and detach the graft from the parent bone without causing breakage. Additionally, an innovative measuring adjusting device was integrated into the equine mosaicplasty instrument kit to prevent inadequate graft insertion.

[0161] Figures l.A / 1, l.A / B illustrate a preferred embodiment of the improved kit according to the invention.

[0162] The kit according to the invention optionally comprises a tubular chisel 2 for graft harvesting shown in figures 2.A-2.C extending along a longitudinal axis between a proximal end 28 and a distal end 29. The chisel may have a graft accommodating portion 22 extending from its proximal end 28. The chisel 2 may be provided at its proximal end 28 with a cutting edge 21. The cutting edge 21 is adapted to the high hardness of horse bone and may thus have an inner angle comprised between 5° and 45°, preferably between 10° and 20°, as shown in figure 2.C. The tubular chisel 2 may have an inner diameter at the cutting edge part higher than 8,5 mm, preferably 10 mm in diameter. The tubular chisel 2 may have preferably an inner diameter at the cutting edge part of 6.5, 8.5, or 10 mm.

[0163] The kit according to the invention may further comprise a chisel tamp 3 shown in figure 3 and a chisel protection cup 4 shown in figures 4.A-4.C. The chisel tamp 3 may extend along a longitudinal axis between a first end 38 and a second end 39. The chisel protection cup 4 may extend along a longitudinal axis between a first end 48 and a second end 49. The chisel protection cup 4 is preferably provided with a first receiving hole 41 extending from its first end 48 and with a guiding hole 42 extending from its second end 49.

[0164] In order to remove the harvested graft of the graft accommodating portion 22 of the chisel 2, the portion of the chisel 2 extending from its proximal end 28 may be received in the first receiving hole 41 of the chisel protection cup 4. The chisel tamp 3 may be inserted and guided from its first end 38 in the guiding hole 42 of the chisel protection cup 4. Figure 15 illustrate a preferred embodiment of the graft harvesting operation. Figures 5. A and 5.B depict the architecture of the drill 5 according to the invention. The kit according to the invention comprises a drill 5 for drilling a graft recipient cavity into the targeted cartilage and osteochondral region. The drill 5 is formed as anon-tubular body. The drill 5 extends along a longitudinal axis between a proximal end 58 and a distal end 59. The drill 5 is provided at its proximal end 58 with a cutting head part 51, which is comprised within a cylindrical geometrical envelope surface 510 of a first diameter D5.

[0165] The drill 5 comprises a narrowed portion 52 adjacent to the cutting head part 51 having a second diameter D52 smaller than the first diameter D5, the narrowed portion 52 being configured to accommodate the debris of a drilling operation. The narrowed portion 52 has preferably a cylindrical shape. The debris storing narrowed portion 52 thus enables an operator to avoid during drilling the necessity of a longitudinal movement for pulling out the drill 5 several times from the drilled cavity in a direction opposite to the drilling direction.

[0166] A guiding portion 53 of a cylindrical shape having a diameter equal to the first diameter D5 is provided between the narrowed portion 52 and the distal end 59. The guiding portion 53 is configured to be slidably and rotatably fitted within a drill guiding portion 61 of the drill guide 6.

[0167] The drill is provided at its distal end 59 with a coupling end 54 part of diameter d54, which may be configured to be connected to a drill driving device.

[0168] Figures 5.C and 5.D depict a preferred geometry of the respective portions of the drill 5.

[0169] The cutting head part 51 may be a three fluted cutting head as shown in figures 5 C and 5.D. Each flute of the cutting head part 51 may be formed as a wing 511 radially extending from the longitudinal axis of the drill 5. The wing 511 may have at least one lateral surface 512 comprising a base edge 513 and a top edge 514. The lateral surface 512 is preferably a plan defined by said base edge 513 and said top edge 514.

[0170] As can be seen in the side view of fig. 5C, each of the base edge 513 and the top edge 514 may be a straight edge.

[0171] As shown in figure 5.D, two adjacent flutes have a common base edge 513 and are spaced apart by a groove 515 delimited by the two adjacent lateral surfaces 512, preferably lateral planes of said adjacent wings 511 intersecting in a common base edge 513.

[0172] The cutting head part 51 may terminate at the proximal end 58 of the drill 5 in a protruding tip 516 having a conical end surface.

[0173] The cutting head part 51 is optionally a Smith and nephews type head.

[0174] The cutting head part 51 thanks to its preferred geometrical configuration as depicted in figures 5.C and 5.D guides the debris during drilling toward the narrowed portion 52.

[0175] The coupling part 54 may have a flat part 541 and a groove 542 perpendicular to the longitudinal axis. The flat part 541 may be a Schell kupplung, which may have a length of 30 mm for example.

[0176] The guiding portion 53 is preferably graduated as shown on fig. 5.C. In the example shown in figures 5.A-5.D, the cutting head part 51 has a first diameter D5 of 10 mm and a length of 17 mm, thus the guiding portion 53 has a diameter equal to 10 mm and a length of 40 mm. The narrowed portion 52 has a diameter D52 of 6 mm and a length of 30 mm. The coupling part 54 has a diameter d54 of 4.5 mm and a length of 30 mm.

[0177] As shown in figure 6, the kit according to the invention comprises a drill guide shown for positioning the drill with respect to the joint.

[0178] The drill guide 6 extends along a longitudinal axis between a proximal end 68 and a distal end 69. The drill guide 6 comprises a drill guiding portion 61 having a cylindrical drill guiding hole 610 of diameter d62 equal to the first diameter D5 extending along the longitudinal axis of the drill guide 6 for guiding the drill 5 in translation along the longitudinal axis. For this purpose, in a mounted state for drilling, the guiding portion 53 of the drill 5 is fitted within the guiding hole of the drill guide as shown in fig 16.B.

[0179] The drill guide 6 further comprises a bone-tissue engaging portion 62 located at said proximal end 68 having a sharpened edged rim of diameter d62, the rim being perpendicular to the first axis and being configured to abut against the outer surface of the bone tissue to be removed.

[0180] The drill guide 6 may be provided with an angled stylet 63 extending in a transverse direction with respect to the longitudinal axis of the drill guiding portion 61. The stylet 63 is configured to be manipulated by an operator during a drilling operation so as to precisely maintain the drill guide 6 in position, which is particularly adapted in case of operation site difficult to access.

[0181] Figure 7 shows a dilator 7 according to the invention. The dilator 7 extends along a longitudinal axis between a proximal end 78 and a distal end 79. The dilator 7 has a dilating portion 71 located at its proximal end 78 configured to be inserted into the drilled graft recipient cavity. The dilating portion 71 of the dilator 7 has a dilating ratio defined as the total diameter increase of the dilating portion 71 to the length of the dilating portion 71. In the case of graft recipient cavity of 8.5 mm, the dilating portion 71 has an initial diameter d71 of 8.5 mm and an end diameter of 8.9 mm. Thus, in this example the dilating portion 71 has a dilating ratio of 0.4 / 9 [mm / mm].

[0182] The dilator 7 may be provided with a graduated portion 72. The dilator may have an enlarged cylindrical end portion 73 arranged at its distal end 79 provided with a hammering surface 731. The end portion 73 is preferably provided with a through-hole 732 into which a stylet can be engaged to increase leverage. This arrangement facilitates the removing of the dilator 7 when it is in a tightly hammered state within the graft recipient cavity.

[0183] The kit according to the invention comprises a measuring adjusting device 8 for depth measurement of the graft recipient cavity as well as for the precise cutting of the graft to the measured size, in order to adjust precisely the graft to the graft recipient cavity. Figures 8. A and 8.B illustrate an exemplary embodiment of the measuring adjusting device 8.

[0184] The measuring adjusting device 8 preferably comprises a rod 80, a tubular measuring sleeve 90 and a securing element 85. In the exemplary embodiment shown in figures 8.A and 9.B, the measuring rod 81 extends along a longitudinal axis between a proximal end 808 and a distal end 809 and is provided at its proximal end 808 with an abutment surface 802 configured to abut against the bottom surface of the graft recipient cavity. The measuring rod 80 may have an outer guiding surface 803 of which at least a portion is configured to be fitted in the drilled graft recipient cavity as shown in figure 8. A. The measuring rod 80 may be further provided at its distal end 809 with a graft holding surface 804, against which an extremity of the graft can be abutted. Figure 8.B indicates typical values of the diameter D80.

[0185] The tubular measuring sleeve 90 may extend along a longitudinal axis between a proximal end 908 and a distal end 909. The measuring sleeve 90 may comprise a guiding through hole, into which a graft can be slidably fitted from its distal end 909 and the measuring rod 80 can be slidably guided from its proximal end 908.

[0186] The measuring sleeve 90 may be provided at its proximal end 908 with an external abutment surface 901 configured to abut against a surface surrounding the drilled graft recipient cavity and at its distal end 909 with an external cut guiding surface 902, which is configured to guide a cutting device for cutting the graft fitted into the guiding through hole of the measuring sleeve.

[0187] The measuring adjusting device 8 may further comprises a securing means 85 for securing the measuring rod 80 at a desired position with respect to the measuring sleeve 90. The securing means 85 may consist of a threaded member, for example a setscrew 851, which can be inserted into a threaded hole of an annular protruding portion 852 of the tubular measuring sleeve 90. The measuring rod 80 may have a groove 805 or a flat surface extending along its longitudinal axis against which an end surface of the setscrew 851 may abut. The measuring sleeve 90 may be provided with a graduated slot 903 extending from its distal end 909. The annular protruding portion 852 of the securing means 85 may be located at the end point of the graduated slot 903, as shown in figure 8.B.

[0188] Figures 9.A, 9.B show such a measuring adjusting device 8 during use. A freshly harvested osteochondral graft of 8.5 mm diameter is positioned at the distal end 909 of the measuring sleeve 90 against the graft holding surface 804. The channel depth of the graft recipient cavity was previously measured by the relative sliding of the measuring sleeve 90 on the measuring rod 80 inserted in the graft recipient cavity until the abutment surface 901 of the measuring sleeve 90 abutted against the surface surrounding the measured graft recipient cavity. The relative position of the measuring sleeve 90 on the measuring rod 80 was secured with the securing means 85. The freshly harvested osteochondral graft can be cut along the cut guiding surface 902 of the measuring sleeve 90 to the length of the measured channel depth.

[0189] Figures 10.A and 10. B depict an exemplary embodiment of a graft insertion guide 100 of the kit according to the invention, which differs from the previously described drill guide 6. On the contrary to the prior art kit shown in figure 1.B the kit according to the invention comprises a graft insertion guide 100 in addition to the drill guide 6. The graft insertion guide 100 comprises a cylindrical body 101 provided with a graft guiding hole 102 extending along a longitudinal axis between a proximal end 108 and a distal end 109. The graft guiding hole 102 is configured to guide in translation a slidably fitted graft. Figure 10 indicates typical values of the diameter DIO 1 of the body 101 and diameter d 102 of the graft guiding hole 102, wherein the size indication may correspond to the graft diameter. The body 101 further comprises a window 103 formed in the vicinity of the proximal end 108 of the graft insertion guide 100 for visualizing the inserted graft. A positioning resting surface 104 is provided at said proximal end 108. The positioning resting surface 104 is devoid of any outwardly protruding sharpened edge so as not to damage the surrounding surface, especially cartilage on the surface. Thus, the positioning resting surface 104 can be gently abutted against a surface surrounding the drilled graft recipient cavity.

[0190] The graft insertion guide 100 may be provided at its distal end 109 with an angled stylet 105 extending in a transverse direction with respect to the longitudinal axis of the graft insertion body 101. The stylet 105 is configured to be manipulated by an operator during graft insertion operation so as to precisely maintain the graft insertion guide 100 in position, which is particularly adapted in case of an operation site difficult to access.

[0191] Figure 11 illustrates an exemplary embodiment of a shaping cup 110 for graft insertion of the kit according to the invention. The shaping cup 110 is made of a soft material, preferably a plastic material for positioning and shaping the protruding surface of the graft with respect to the surrounding cartilage surface. The shaping cup is preferably configured to be mounted on the proximal end 78 of the dilator 7. For this purpose, the shaping cup 110 may be provided with a hole 111 having a tapered end, into which the dilating portion 71 of the dilator 7 may be inserted. The shaping cup 110 has a shaping surface 112 formed as a concave surface fitting to the cartilage surface, wherein the minimum diameter of the shaping cup is larger than the diameter of the graft.. The shaping surface 112 is configured to contact the cap surface of the graft inserted into the graft recipient cavity. The concave shaping surface 112 may have a radius essentially identical with the hyaline cartilage to be treated, preferably a radius of 70 to 90 mm, preferably 75 to 85 mm, more preferably 78 to 82 mm, in particular 80 mm.

[0192] In the past several years in the research group of the inventor data of 33 horses undergoing osteochondral graft implantation into the weight-bearing surface of the fetlock and stifle joints have been analysed to address operation methodologies of subchondral cyst-like lesions or full-thickness cartilage defects. In the long term, 64% of the patients regained soundness and were capable of athletic performance. Moreover, 88% of patients demonstrated improvement in their ability to engage in the intended activities post-surgery. In the study, the age of horses ranged from 1 to 15 years, and it did not significantly affect the outcome. This contrasts with several surgical procedures previously described as successful primarily in young individuals up to the age of 3.24 13

[0193] However, the experience regarding the quality of the operation outcome suggested that novel features of the invention increased the preciseness of the operation and helped the formation of a more even weight-bearing surface without impairment to reduce the recurrence of injuries like cysts. Thus, the invention further relates to a method for replacing carried out using the kit according to the invention, an exemplary embodiment of which is described below in the examples section.

[0194] The advantages of the kit according to the invention and the method performed using the kit according to the invention are detailed below.

[0195] It is possible to insert grafts of larger diameter (up to 10 mm diameter or more), which results in a more stable bone reconstruction, since the inserted graft is not damaged by the load of the horse (100- 700 kg) immediately after the surgical intervention . Especially in the case of a cartilage trap, the cartilage meeting the surrounding cartilage is naturally less stable than a osteochondral graft sealed in a press-fit manner at the desired depth using the method according to the invention.

[0196] Precise depth measurement and cutting to size, which steps are necessary in case of horse surgery. On the contrary, these steps are not necessary in human practice, where grafts are shorter than the recipient channel (hole), in which grafts are implanted.

[0197] The shaping cup is specifically used for precisely positioning the graft to the correct level . On the contrary, in human practice, the dilator is used to position the graft at the desired level. It is important to note that in human practice it is much easier to slide the graft in than on a horse. In case of a horse, higher force is needed. Thus use of a metal -tipped dilator alone without any shaping cup would slip on the graft cap when hammering the graft in the final stage into the recipient cavity. This would cause damage, especially fracture of the implanted hyaline cartilage layer. This is avoided by using the shaping cup according to the invention of a soft material, especially in plastic. The shaping cup has a minimum diameter larger than the diameter of the graft, typically at least 3-5 mm larger around the circumference (i.e. a tiny bit softer) and may be applied on the dilator.

[0198] The kit provides a separate drill guide 6 and a separate graft insertion guide 100. The diameter of the graft guiding hole of the graft insertion guide is dimensioned to receive a swollen graft. Thus, the diameter of the graft guiding hole is slightly larger, than the drill guiding hole and consequently the drill, especially the cutting head part of the drill. In human practice only a single guide is used both for guiding the drill and inserting the graft into the recipient cavity. In this case, the single guide has a single larger diameter. Thus, the drill bit used in human case has a diameter increasing from the drilling tip in order to precisely fit with the single guiding hole of the guide and thus avoid large clearance. In horse surgery, it is a requirement to keep drill diameter in lowest possible range due to the high hardness of the horse bone. Increasing the diameter of the drill would lead to irreversible damage in the horse bone tissue. In the case of human bone tissue, performing drilling with an increased drill diameter is not an issue, since human bone tissue has a lower hardness. This is the reason why the kit provides a separate graft insertion guide 100 for guiding the graft during insertion and a separate drill guide 6 adapted to guide the drill 5 according to the invention.

[0199] The kit according to the invention provides a new drill adapted to the horse bone, which is able to drill a hole in the cartilage with a regular edge (no jagged edge) on the articular surface using a specially adapted drill guide. It is an important requirement that the bone debris generated during drilling does not get trapped in the cutting head part of the drill, as this would lead to a quick raise of the drill temperature during drilling, causing damage, especially bone necrosis in the drilled channel, which has to accept and integrate the new graft. Therefore, drill configurations typically used in human surgery cannot be used in the same manner in horse surgery. In case of a prior art drill, it is necessary to take out the drill 4-5 times during a drilling step, clean the drill and cool it, before continuing the drilling step. Taking out the drill several times may cause minor changes in drilling direction, thus in the drilled cylindrical surface of the cavity. The resulting geometrical defect is disadvantageous for the suitable incorporation of the graft (graft) into the surrounding bone. This drawback is solve by the drill according to the invention.

[0200] In embodiments of the present invention implantation was performed using both arthrotomic and arthroscopic approaches. Although arthroscopy is preferred over arthrotomy in human surgery[Bordes M et al. 2022],25in our experience, arthrotomy offers better assessment of lesion characteristics and allows for more accurate, three-dimensional adjustment of surface congruency during plug placement. As a result, arthrotomy is currently preferred over arthroscopy. Prior to arthrotomy, a rapid intraoperative diagnostic arthroscopic examination of the recipient joint is performed to assess soft tissue structures within the joint and debride lesions if present.

[0201] Gentle insertion without damaging the cartilage cap and subchondral bone of the transplanted grafts is crucial for successful outcomes. Possible errors include striking the graft too forcefully in an attempt to sink it to the surface level, especially if it is improperly sized, or creating a proud surface, leading to damage to intra-articular soft tissues. Such errors may result in increased loading and micromotion of the plug, leading to improper incorporation and chondral and subchondral necrosis.26If a step remains on the articular surface, the protruding graft should be over drilled and replaced instead of making aggressive attempts to sink it deeper.

[0202] Surgical wound-related complications occurred in 9% (3 / 33) of patients. One horse developed seroma formation at the arthrotomy wound over the stifle, which resolved completely after drainage. Dehiscence of the arthrotomy wound occurred in two patients. The arthrotomy incision was closed in five layers for femorotibial joints and in four layers during fetlock arthrotomies. Apposing the corresponding layers separately, particularly the superficial and deep fascia, over the stifle is essential to prevent wound dehiscence. Repeated closure was performed in these two cases, resulting in no further complaints. In three out of 33 cases, complications in the recipient femorotibial joints were as follows: Horse 16 became infected during an equine herpesvirus-1 outbreak 14 days post-surgery, presenting symptoms such as high rectal temperature (40°C), unilateral corneal opacity, distention of the recipient’s right medial femorotibial joint, and severe lameness. Necrosis of two of the four grafts occurred in this case, presumably due to viral microvasculitis, leading to partial debridement of these grafts during the follow-up arthroscopic surgery. Horse 15 developed iatrogenic septic arthritis following an intraarticular corticosteroid injection in the recipient joint 4 months post-surgery. These two horses remained lame despite repeated arthroscopic lavages of the affected joints. The third intra-articular complication was graft cup breakage in one case out of two horses, where a focal, 6-8 cm2cartilage defect on the MFC accompanied by advanced osteoarthritis of the MFT joint was cured. Six pieces of osteochondral grafts were implanted in both animals with less satisfactory results. The broken cap in Horse 8 was arthroscopically removed during the second surgery, resulting in marked improvement. Horse 7 underwent a 10-year follow-up, showing no improvement during the initial 2-3 years post-surgery. Subsequently, gradual improvement was observed, reaching 1 / 5 degree of lameness 10 years postsurgery. However, this transplantation technique is much less suitable for candidates with large (>2-3 cm2) defects of the weight-bearing articular surface, as observed in Horses 7 and 8. Most likely, the unstable host bed surrounding the transplants is responsible for unfavorable outcomes. In contrast to human surgery, abrasion arthroplasty was not performed in these two cases, and the pathological subchondral bone at the ebumated area was not curetted entirely to prevent instability of the grafts.

[0203] Donor-site morbidity ranging from 5.9%— 19.6% has been reported in human patients, with complications including patellofemoral disturbances, crepitation, knee stiffness, recurrent joint swelling, painful hemarthrosis, and persistent pain.27In our patients, we did not encounter any donor-site-related complications, except mild distention of the femoropatellar joint in the early postoperative period, which dissolved within a few weeks. However, the application of larger allografts presents a promising alternative for avoiding donor-site issues. Osteochondral allografts were successfully employed in two of our cases; nevertheless, the optimal harvesting and storage conditions for osteochondral allografts are yet to be determined.23

[0204] The radiographic filling of the implantation site was assessed in 17 patients. However, differences in image quality, settings taken by field veterinarians, and radiographic positioning hindered the objective assessment of the surgical sites. Complete resolution (refer to Figure 5) was observed in nine cases, with the highest frequency noted in cases involving the fetlock joint. Conversely, in five cases, radiographic enlargement of the cyst was observed. This phenomenon could potentially be attributed to altered subchondral bone density, imperfect graft matching, and total or partial graft necrosis in horses with septic complications and substantial defects.

[0205] In this retrospective study, patient age did not significantly impact the outcome; however, horses aged <10 years tended to have a more favorable prognosis.

[0206] The limitations of this clinical study include its retrospective nature, lack of standardization of the surgical technique over time, and incomplete availability of postoperative data for all patients. Additionally, the evaluation of outcomes relied partially on observations made by owners and referring veterinarians, which could not be standardized. Furthermore, the study was limited by its small sample size.

[0207] In our experience, mosaic arthroplasty proves to be a valuable and cost-effective technique for treating SBCs. This approach involves eliminating the fibrous cyst lining, filling the cyst cavity with stable trabecular bone, and providing a hyaline or hyaline-like weight-bearing joint surface, regardless of the individual’s age.

[0208] Preferably, the shaping cup can be made of any plastic material suitable for preparing a sufficiently hard still non cartilage injuring materal, like PVA, PLA (poly-lactid acid), etc. In an other option it can be prepared from HDPE (high density polyethylene), PET (poly-ethylene tereftalate), Teflon, PEEK, etc.

[0209] Plastic materials and methodologies are listed e.g. in Harper, Charles A., HANDBOOK OF PLASTIC PROCESSES, John Wiley and Sons, 2006.

[0210] EXAMPLES

[0211] Materials and methods

[0212] 1, Study design and population

[0213] The medical records of 33 horses who underwent mosaic arthroplasty at four different institutions, overseen by the last author between 1998 and 2023, were reviewed. Data obtained from the medical records included details such as age, breed, sex, affected limb and joint, lameness severity, animal workload, surgical approach, concurrent pathology, postoperative complications, and overall outcomes. Diagnostic imaging reports, when accessible, were also included in the analysis.

[0214] 2, Preoperative procedures

[0215] During the physical examination, lameness was evaluated and scored on a scale of 0 and 5 using the grading system established by the American Association of Equine Practitioners. Perineural or intrasynovial analgesia was administered to localize the site of pain, and a minimum of two different radiographic projections were obtained to capture subchondral lucencies or osteoarthritic changes within the joints. Ultrasonography was also performed to identify cystic lesions in selected cases. Additionally, diagnostic arthroscopy was performed in some instances before implantation to detect focal cartilage damage.

[0216] Preparation of the parts of the kit is carried out by usual metal forming processes.

[0217] The forming of the shaping cup is carried out e.g. by injection moulding.

[0218] In another embodiment forming of the shaping cup is carried out by 3D printing.

[0219] 3 , Surgical technique

[0220] The horses underwent al2-h fasting period before the administration of general anesthesia. Preoperative antimicrobials were administered, consisting of either amoxicillin trihydrate at a dosage of 5.6 mg / kg IM; potassium clavulanate 1.4 mg / kg IM, and gentamicin at a dosage of 6.6 mg / kg IV or benzathine penicillin at 4,000 U / kg IM, procaine penicillin at 1,000 U / kg IM or (up to) procaine penicillin (22 000 lU / kg IM), and dihydrostreptomycin sulfate at 6.2 mg / kg IM or 15 mg / kg IM. Additionally phenylbutazone was administered at a dosage of 2.2 mg / kg IV.

[0221] After the induction of general anesthesia, which was maintained via inhalation, horses with lesions of the femoral condyle were positioned in dorsal recumbency. Conversely, those with lesions of the distal MCIII or MTIII were positioned in lateral recumbency, with the donor site positioned uppermost.

[0222] Graft harvest A various sizes of osteochondral grafts were harvested from the contralateral medial femoral trochlea using a tubular chisel of 6.5, 8.5, or 10 mm in diameter, the latter being a novel, horse -specific increased size, depending on the size of the recipient site estimated on preoperative radiographs. Special equipment was designed and manufactured at the University of Veterinary Medicine, Budapest.

[0223] The medial femoral trochlea was approached with the limbs in maximal extension. Initially, a small arthrotomy wound 30-40 mm in length, was created between the medial and middle patellar ligaments to expose the donor site. Subsequently, this method was exclusively replaced by the arthroscopic approach, which resulted in two stab incisions, consistent with an arthroscopic and harvesting portal. For femoral condyle implantation three to six pieces, and for fetlock joint implantation, one or two pieces of 25-40 mm-long cylindrical grafts were harvested approximately 5- 10 mm apart. The donor channels were left empty, and after lavage of the femoropatellar joint, the portals were closed in a routine fashion. Grafts were stored in sterile isotonic saline until implantation.

[0224] In somewhat more detail, the first graft was harvested from the proximal aspect of the medial femoral trochlea using a mallet and a tubular chisel (manufactured by Metrimed Kft., Hodmezovasarhely, Hungary) with a diameter of 6.5, 8.5, or 10 mm, depending on the recipient site. Arthroscopic guidance ensured precise chisel alignment. After driving the chisel to the required depth (25-40 mm, marked on the chisel surface) with the mallet, a semi-circular motion separated and detached the graft (Figure 6).

[0225] A preferred embodiment of the method according to the invention will be described in detail in the case of an articular surface reconstruction on horse from intra-articular exploration and subchondral cyst surgery from extra-articular exploration.

[0226] Articular surface reconstruction on horse from intra-articular exploration

[0227] As illustrated in figure 16.A, an osteochondral region to be repaired is determined. Preferably a diagnostic arthroscopy of the recipient femorotibial joint is carried out. The size and number of grafts required may be thus determined. Debridement may be applied if necessary. Preferably mapping of intra-articular lesions is performed. In this way, the cavities can be identified, and it is possible to determine exactly at which point, what diameter and how long the graft will have to be implanted.

[0228] A graft is then provided and prepared.

[0229] In an optional embodiment shown in figure 15, the method may comprise a preliminary step of taking a graft. In the present example, graft is taken of the coskisssk-teial fe -or patelk-r jomt under arthroscopic control. A standard optic portal may be used. Graft taking operation may be carried out perpendicular to the medial femoral trochlear surface in proximodistal order. The graft taking operation may comprise the preferred following steps. The graft may be harvested from the donor, preferably under arthroscopic control.

[0230] First, with the femoropatellar joint in full extension, taking the first graft through a portal under the patella apex in the most proximal safe area, then with the limb gradually flexed distally from this, taking into account the curvature of the articular surface, approximately 8- 10 mm distal to the first canal. A maximum of 4-6 6.5 mm diameter grafts can be taken from one joint, 3-4 from 8.5 mm grafts and 2-3 from 10 mm grafts.

[0231] Placing the chisel 2 through a 1-1.5 cm incision on the surface (figure 15. A).

[0232] Using the arthroscope to check the correct position of the (tubular) chisel 2 in relation to the joint surface.

[0233] Using a hammer , pushing the chisel 2 to the correct depth under arthroscopic control (figure 15.B).

[0234] Inserting a stylet through the upper bore of the chisel (“T handler”), using a sudden twisting movement to force the protrusion and then it is withdrawn from the canal or joint by twisting back and forth (figure 15.C).

[0235] Placing the chisel 2 on the operating tray with its edge facing upwards, placing a sterile swab underneath, placing the chisel protection cup 4 protecting the chisel edge on top of it, and hammering out the graft stuck in the chisel from the retrograde direction using the chisel tamp 3.

[0236] The graft is then prepared by preferably placing the harvested graft in sterile physiological saline until implantation. In the majority of cases, the articular surface to be transplanted may be excavated from a mini-arthrotomy.

[0237] The method includes a step of cutting a cartilage layer (cap) corresponding to said determined osteochondral region as shown in figure 16. B. The bone-tissue engaging portion 62 of a drill guide 6 is abutted perpendicularly against the cartilage surface of said determined osteochondral region to be repaired. The drill guide 6 is sunk into the hyaline cartilage with its bone-tissue engaging portion 62 preferably by using a hammer to cut a circle around the drill channel.

[0238] The method includes a step of drilling a graft recipient cavity of a desired depth, typically 3-6 cm based on the determined osteochondral region to be repaired, wherein drilling the graft recipient cavity comprising:

[0239] - fitting the drill 5 into the cylindrical guiding hole 610 of the drill guiding portion 61 of the drill guide 6,

[0240] - driving the drill 5 into said determined osteochondral region until a desired depth,

[0241] - wherein the drill 5 is guided with respect to the drill guide 6 by at least the guiding portion 53 provided on the drill 5, wherein the drill 5 is preferably further guided with respect to the drill guide 6 by the guiding portion 53 and at least the cutting head part 51,

[0242] - if required evacuating the drill waste from the cutting head part 51 of the drill 5 by transporting it from the cutting head part 51 toward the narrowed portion 52 of the drill 5 adjacent to the cutting head part 51, the drill waste being preferably stored in the space formed between the narrowed portion 52 and the surface of the drill guiding hole 610 of the drill guide 6. For cysts, the channel is drilled at least 5-8 mm deeper than the depth of the cyst. Preferably the first channel (hole) is drilled into the centre of the cyst or lesion using the appropriate drill guide 6. Preferably the replacement operation start with an 8.5 or 10mm graft.

[0243] Afterwards, the arthroscope may be used to review and wash out the drilled canal, clean out any fibrous tissue in the side chambers, and plan whether or not further grafting is necessary.

[0244] The method includes a step of dilating the drilled graft recipient cavity, as shown in figure 16. C. Dilating the drilled graft recipient cavity consists in inserting the dilating portion 71 of the dilator 7 into the graft recipient cavity until the proximal end 78 of the dilator 7 abuts against the bottom of the graft recipient cavity. The dilating portion is then maintained in this inserted state for a predetermined period of time.

[0245] After drilling, flushing and cleaning the channel (hole), the dilator 7 may be hammered down to the bottom of the channel. For removing the dilator 7, a stylet, for example the chisel tamp 3 of the tubular chisel 2 may be inserted into the through-hole 732 at the top end 79 of the dilater 7 to remove the stuck expander spike from the duct by twisting it.

[0246] The dilated channel may be washed one more time. Draining the fluid from the channel may be performed with a piece of infusion equipment fitted to a syringe.

[0247] The method includes a step of measuring the depth of the drilled graft recipient cavity comprising: Fitting the measuring rod 80 of the measuring adjusting device 8 into the graft recipient cavity, until the abutment surface 802 abuts against the bottom of the graft recipient cavity, by preferably hammering down the measuring rod 80 to the bottom of the channel.

[0248] Engaging the measuring sleeve 90 on the measuring rod 80, preferably with the graduated slot 903 placed on the side of the distal end 809 of the measuring rod 80 so that the markings on the measuring rod face upwards.

[0249] Sliding down the measuring sleeve 90 on the measuring rod 80 until an abutment surface 901 of the measuring sleeve 90 abuts against the joint surface surrounding the drilled graft recipient cavity.

[0250] Securing the relative position of the measuring sleeve 90 and the measuring rod 80 with the securing means 85.

[0251] Determining the depth of the graft recipient cavity, preferably by determining the position of the graft holding surface 804 with respect to the graduated slot 903 of the measuring sleeve 90.

[0252] Removing the measuring adjusting device from the graft recipient cavity, i.e. the channel. Thus, the measuring rod 80 on the measuring side of the adjusting measuring device 8 is located in the guiding through hole of the measuring sleeve 90 at the exact distance from the measured depth. In a preferred embodiment, the measured depth is determined using the graduated 903 slot of the measuring sleeve 90. The method includes a step of cutting the graft at the measured length comprising:

[0253] Fitting the graft within the measuring sleeve 90 from the distal end 909 until it abuts against the graft holding surface 804 of the measuring rod 80. Preferably the removed osteochondral graft is inserted with the hyaline cartilage cap facing upwards.

[0254] Cutting the graft to size by guiding a cutting device at the cut guiding surface 902 of the measuring sleeve.

[0255] The method includes a step of inserting the graft into the graft recipient cavity including: Fitting the graft within the graft guiding hole 102 of the graft insertion guide 100.

[0256] Abutting and positioning the graft insertion guide 100 by means of its positioning resting surface 104 provided at its proximal end 108 against the surface surrounding the drilled graft recipient cavity.

[0257] - Guiding the graft in the graft guiding hole 102 in translation toward the graft recipient cavity, until the graft is inserted in the graft recipient cavity in a position in which the distal end of the graft protrudes from the surrounding surface of a given distance. Visualizing said distance through the window 103 of the graft insertion guide 100.

[0258] Preferably inserting the osteochondral graft into the graft insertion device 100 with the graft cap facing up in the direction of the distal end 109 of the graft insertion guide 100 and then gently hammering it down into the channel using the proximal end 78 side of the dilator 7. Preferably removing the graft insertion guide 100, when the graft protrudes just one mm above the surface of the graft recipient cavity.

[0259] The method includes a step of positioning and shaping the graft protruding surface with respect to the surrounding surface by preferably mounting the shaping cup 110 on the proximal end of the dilator 7, positioning the shaping surface 112 of the shaping cup 110 on the protruding distal surface of the graft, gently hammering the graft cap into the joint surface by hammering the shaping cup 110 mounted on the dilator 7 until the distal surface of the graft is in the desired position, in flush mate with the surrounding surface and the graft distal end is shaped at the desired shape.

[0260] Preferably the graft is further pushed down, optionally gently hammered down, by the shaping cup 110 of a cartilage -saving (soft, preferably plastic) material, said shaping cup HOjhaving a shaping surface 112 configured to contact the cap surface of the graft inserted into the graft recipient cavity, wherein the minimum diameter of the shaping cup is larger than the diameter of the graft, the shaping surface 112 being formed as a concave surface fitting to the cartilage surface, thereby forming an even surface on the injured cartilage area.

[0261] In the case of several inserted graft, drilling the following graft recipient cavity may precede the step of hammering the graft caps with the shaping cup 110 mounted on the dilator 7.

[0262] The method may comprise a final step of cleaning the joint and closing the operation site on the horse. Subchondral cyst surgery from extra-articular exploration

[0263] In this example, the graft is taken from the external iliac crest from an incision of 3 -5 cm in the external run of the tuber coxae. The cannula is preferably hammered slightly caudomedially into the external iliac crest. If necessary, 2-3 grafts of 4-6 cm length can be taken from this site.

[0264] The area to be treated may be explored from the nearest explorable surface to the cyst. Importantly, if there are ligaments or other formations in the area, it is advisable to excavate these parallel to the fibre run, but with the bone surface sufficiently exposed for safe drilling and graft insertion.

[0265] Once the area to be treated has been prepared, the drilling is typically performed parallel to the joint surface so that the center of the drilled hole passes through the center of the cyst, avoiding penetration of the joint. Based on X-rays, CT scans, etc., the appropriate graft size may be predetermined, wherein the graft may be taken at the beginning of the operation using the graft chisel.

[0266] The next steps are preferably similar to the steps described previously: cleaning the canal, washing, dilating, measuring the channel depth, then cutting to size and inserting the graft, and closing the surgical site.

[0267] Medial or lateral femorotibial joint implantation

[0268] For implantation into the medial or lateral femoral condyle, the horse was positioned in dorsal recumbency with the recipient stifle flexed at approximately 90°. In early cases, arthrotomy was performed to expose the femoral condyle; however, in the last decade, arthroscopic evaluation has preceded arthrotomy to diagnose concurrent soft tissue lesions. Although implantation is performed during arthroscopy in certain cases, in majority of instances, an arthrotomy is performed. The SBCs were drilled 8-10 mm deeper than their cavities at the cloaca, and the fibrous lining of the lesion was entirely removed. The wall of the recipient hole was carefully inspected arthroscopically for any remaining cavities or internal linings. After flushing and dilating the drilled hole, a measuring adjusting device was employed to measure the channel depth and cut the graft to an appropriate length. Grafts were delicately inserted using a press-fit technique, using a drill guide and graft tamp, with careful attention to preserving surface congruency. Depending on the required number of grafts, additional holes were drilled adjacent to the first hole, and the procedure was repeated until the cyst cavity was completely filled. The implants were positioned adjacent to each other or several millimeters apart. At the conclusion of the procedure, the joint was lavaged, and the surgical wound was closed in five layers, followed by application of a stent bandage.

[0269] In two cases, an attempt was made to reconstruct the focal full -thickness cartilage loss of the large (6-8 cm2) weight-bearing surfaces of the MFC. The same implantation technique was used in these patients, with numerous (six pieces) short (15-20 mm in length) osteochondral grafts inserted in a mosaic-like pattern as shown in figures 12. B and 13. B.

[0270] Additionally, two middle-aged horses were deemed unsuitable donors for autograft harvesting. Osteochondral allografts from individuals aged <5 years were implanted in these horses. Metacarpophalangeal or metatarsophalangeal joint implantation

[0271] Maximal flexion of the metacarpophalangeal or metatarsophalangeal joint exposes the weightbearing surface of the distal metacarpus or metatarsus through a 3-5 cm long arthrotomy over the dorsal aspect of the joint. In one case of trauma (Case 27), insertion was performed under arthroscopic control. The cyst was identified and drilled, and implantation was performed as previously described for the stifle joint. The arthrotomic wound was closed in four layers, and a Robert Jones bandage was applied for 2 weeks.

[0272] Postoperative care

[0273] The horses received antibiotic treatment for 5-7 days and nonsteroidal anti-inflammatory medication (Phenylbutazone 2.2 mg / kg PO twice daily) for 7 days postoperatively. Postoperative radiographs were taken 7-14 days post-surgery, and the horses were hospitalized until suture removal 14 days after surgery.

[0274] Rehabilitation protocols have evolved over the past few decades, with an increasing use of stable confinement. Initially, 1 week of box rest was followed by 2 weeks of hand-walking, after which the horses were turned into a paddock. However, drawing from human experience, a longer rest period of 2 months is recommended, followed by daily hand walking thereafter. Paddock exercise is initiated only 3-4 months following surgery. At this time, follow-up physical and radiographic examinations, along with intraarticular treatment using 10-15 mg triamcinolone acetonide and hyaluronic acid, were recommended by the referring veterinarian or hospital. Follow-up arthroscopy was suggested in cases where lameness persisted or additional pathology was suspected. In case without complications, work could be resumed as early as 6 months post-surgery.

[0275] 4, Follow-up evaluation

[0276] A minimum follow-up period of 12 months was ensured for all patients. Long-term follow-up involved recheck examinations or control arthroscopy at the hospital, observations by the owner or referring veterinarian, and access to competition results available in national competition or racing databases (www.dijugratas.hu, www.kincsempark.hu, and www.fogatsport.hu). The lameness severity post-surgery and horse performance levels were assessed. A successful outcome was defined as a horse being free of lameness and capable of performing at its previous or higher level of activity. The outcome was deemed satisfactory if lameness improved or resolved after the operation, and the horse was used for lower levels of activity than its previous or intended use. The unsatisfactory outcome was recorded if lameness remained unchanged or worsened post-surgery.

[0277] 5 , Data analysis

[0278] Statistical analyses were performed using the R software. A logistic regression model was employed to compare outcomes based on the following variables: age group (age 0-3 years vs. >3 years), preoperative lameness grade (1-5), presence of preoperative concurrent joint pathology (yes / no), operated joint (femorotibial or fetlock), and number of implanted grafts (1-6). Outcomes were classified as either improved or unimproved in the statistical analyses. The level of significance was set at p<0.05. Results

[0279] 1. Clinical data

[0280] Complete data from 33 horses were available, comprising 11 stallions, 7 geldings, and 15 mares. The median age of the horses was 3 years, with an average age of 5.7 years (range, 1-15 years). The study included were three Thoroughbreds, five Standardbreds, five Arabian horses, one pony, two Quarter Horses, and 17 Warmbloods. Among the lesions, 14 were SBCs in the MFC of the right hind limb, seven were SBCs in the MFC of the left hind limb, and a single SBC affected the lateral femoral condyle of the left hind limb. Additionally, nine horses exhibited cyst-like lesions in the distal MCIII (six cases) or distal MTIII (three cases). Two horses displayed focal 6-8 cm2fullthickness cartilage loss on the MFC of the right or left hind limb.

[0281] In these mosaicplasty operations, the kits of the invention and parts thereof newly developed by the inventors were used in a part of the horses as disclosed below. This allowed a comparison of the practical effects of the invention in contrast to mosaicplasty with previous techniques.

[0282] All horses included in this study exhibited lameness, with a median grade of 3 / 5 (range, 1-5), and despite conservative treatment, none showed long-term improvement.

[0283] 2. Intraoperative observations

[0284] For MFC or LFC lesions, an average of 3.29 grafts (ranging from one to six) were inserted in a mosaic-like pattern, with a median of three grafts. In cases of distal MTIII or MCIII cysts, one graft was implanted in four patients, whereas two grafts were inserted in five patients. The diameters of the grafts varied between 6.5, 8.5, or 10 mm, depending on the conformation and size of the defect.

[0285] During graft harvesting, a primary challenge is encountered in drilling into the neighboring channel, leading to shorter and incompletely harvested grafts. Breakage of the harvested graft was sporadically observed, particularly in the older horses.

[0286] The development of the novel tubular chisel of the invention which has a sharpened rim and can be supplied with a chisel tamp usable as a “T” handler inserted through the hole at the distal end of the chisel during graft extraction greatly improved the success of harvesting the grafts.

[0287] In previous operations, a technical hurdle was encountered where it was not feasible to completely insert a graft during implantation. Consequently, the graft was over drilled, necessitating replacement with another graft of the same size. This phenomenon caused problems specifically in three cases. Following the development of a new measuring adjusting device of the invention, this complication was successfully mitigated.

[0288] Also, the technology of graft insertion has been greatly improved by the development of a drill guide and a graft insertion guide as two separate tools and optionally two separate parts of the kit.

[0289] Using the drill guide 6 of the invention during the drilling procedure of the recipient hole provides an advantage over previous guides in that it comprises a bone-tissue engaging portion 62 located at said proximal end 68 and having a sharpened edged rim being configured to abut against the outer surface of the osteochondral tissue to be removed, preferably the chondrocyte surface thereof. The drill 5 is fited within the guiding hole of the drill guide 6. The advantages of the drill 5 of the invention are detailed below.

[0290] This arrangement allows a safe positioning of the drilling and facilitates the creation of a precisely prepared hole for the graft.

[0291] Thereafter the graft is inserted gently through this instrument into the recipient hole with the help of the dilator and a hammer.

[0292] The graft insertion guide 100 of the kit according to the invention, which was previously the same tool as the drill guide 6, is now differs significantly from the previously described drill guide 6. On the contrary to the prior art kit shown in figure l.B the graft insertion guide 100 comprises as positioning resting surface 104 which is devoid of any outwardly protruding sharpened edge so as not to damage the surrounding surface, especially cartilage on the surface. Thus, the positioning resting surface 104 can be gently abuted against a surface surrounding the drilled graft recipient cavity. This is reflected also in the diameter used which is adjusted to the size of the hole for engaging the graft. In a preferred embodiment the body 101 of the graft insertion guide 100 further comprises a window 103 formed in the vicinity of the proximal end 108 of the graft insertion guide 100 for visualizing the inserted graft.

[0293] Both the graft insertion guide 100 and the drill guide 6 may be provided with an angled stylet for holding these tools stably in place.

[0294] By this improvement the inventors have experienced a significantly more precise provision of the drilled holes (graft recipient cavity) and graft insertion thereto.

[0295] In several experiments the inventors have experienced a problem associated with drilling. The bone tissue of the horses is hard and the debris easily and typically sticks in the grooves of a traditional drilling bit. This may result in increasing the heat during drilling and even the burning of the bone unless the operator is careful enough to pull out the drill from time to time and remove the osteochondral debris. The development of drill 5 having a narrowed diameter for holding the debris and a novel type of head according to the invention resulted in an improved removal of debris during drilling and avoidance of overheating.

[0296] The arrangement of the drilling guide and the drill together provided sharp edged and healthy holes in the injured osteochondral tissue for engaging the grafts.

[0297] In 30.3% (10 / 33) of horses, concurrent joint pathology was identified, either through radiographic examination (8) or arthroscopic evaluation (7). Among these findings, fibrillation of the medial meniscus in three out of 24 cases, injury of the cranial meniscotibial ligament in one out of 24 cases, full-thickness cartilage injuries in two out of 24 cases. Additionally, advanced radiological alterations were noted in six out of 24 cases, including elongation of the proximomedial tibial plateau, periarticular osteophyte formation, or an uneven condylar surface, primarily in the femorotibial joints. In the fetlock joints, concurrent osteochondrosis dissecans were observed in two out of nine cases, periarticular osteophyte formation in one out of nine cases, and cartilage injury one out of nine cases.

[0298] All these results supported the formation of an even condylar surface the methodology for which has been significantly improved by using the kit of the invention n particular the shaping cup and preferably using both the dilator and the shaping cup together

[0299] Follow-up arthroscopy was conducted on nine medial femorotibial joints (MFTJ) 6-10 months post-surgery, with one exception due to sepsis. Among these cases, macroscopic evaluation of adaptation of the implanted grafts revealed congruent articular surface in five horses. The transplanted cartilage exhibited shiny and smooth surfaces, with areas of intact or slightly fibrillated regions at the interface. However, in Horse 2, deformation of the hyaline cap margins was noted, whereas in Horse 8, the cap of a marginal graft was detached and found freely within the MFTJ, necessitating removal during arthroscopy. Additionally, slight fibrillation was observed at the interface region between two other grafts in this case. Two joints required multiple repeat arthroscopies, involving lavage and partial graft debridement, due to septic complications.

[0300] During necropsy, the surgical site in the metacarpophalangeal joint was inspected and appropriately interpreted in a single patient euthanized for unrelated reasons, 2 years post-surgery.

[0301] Postoperative complications occurred in 18% (6 / 33) of patients. Minor complications were present in three horses, including seroma formation at the surgical site (Horse 17) and dehiscence of the arthrotomy wound (Horses 18 and 24).

[0302] Three horses experienced major postoperative complications. Specifically, Horse 8 exhibited detachment of the cartilage cup from one implanted graft, as previously described. Horses 15 and 16 developed septic complications, resulting in subsequent graft necrosis.

[0303] Apart from slight effusion observed in the postoperative weeks, no long-term complications were noted concerning the donor femoropatellar joints. Regarding the recipient femoropatellar joints, effusion was observed in the early postoperative period, accompanied by mild-to-moderate lameness within the first postoperative week; however, this condition significantly improved over a period of 4-weeks.

[0304] 3. Radiographic findings

[0305] Preoperative radiography involved at least two projections of the targeted joint. With the exception of two cases, SBCs characterized by decreased radiopacity surrounded by a sclerotic bony rim were identified. Twenty-four percent (8 / 33) of the horses showed evidence of osteoarthritis in the medial femorotibial joint (7) or fetlock joint (1) on radiography. Postoperative radiographs obtained >10 months post-surgery were available for 17 patients. Complete resolution of the defect occurred in 9 instances. The cyst size decreased in three cases and remained unchanged or increased in five cases radiographically.

[0306] 4. Postoperative follow-up and outcome

[0307] All cases had a minimum follow-up period of 12 months, ranging from 12 to 120 months, with a median duration of 24 months and an average duration of 36.9 months. Sixty-four percent (21 / 33) of the cases were sound 1 year after the procedure and were able to compete at the previous or higher activity level. Twenty-four percent (8 / 33) of the patients showed improvement and were employed for breeding or light-ridden activities. Twelve percent of patients showed no postoperative improvement (2 / 33) or deterioration in lameness (2 / 33). No significant association was found between the outcome and the preoperative lameness score (p=0.45), patient age (younger or older than 3 years) (p=0.58), or the number of implanted grafts (p=0.78).

[0308] Coexistent joint pathology had a significant negative impact on the outcome (p=0.026). Chronic and large lesions, coupled with substantial subchondral bone pathologies necessitating multiple graft implantations, were associated with unfavorable outcomes.

[0309] The postoperative complications were reduced significantly by the use of the novel shaping cup of the invention. The shaping cup is made of a material which does not injures e.g. scraps the cartilage surface e.g. hyaline surface, however, is useful to place the graft into position so that it may form an even surface together with the cartilage surface.

[0310] In case of small scraps or gaps or flaws on the surface, e.g. between the graft and the surrounding cartilage (e.g. cartilage cap) the osteochondral injury of the cartilage or even the underlying bone may recur, e.g. in the form of a cyst.

[0311] The shaping cup fits on a rod whereby it can be hammered so that the graft itself may be hammered, gently, into its designed position in the hole bored previously so that its may form, together with the surrounding cartilage, an even surface repaired by the mosaicplasty method of the invention.

[0312] In the preferred embodiment the shaping cup fits on the dilator thereby simplifying the operation procedure.

[0313] References

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Claims

31. CLAIMS1. A kit of instruments for equine mosaicplasty carried out by placing an osteochondral graft into a targeted osteochondral region, said kit comprising• a drill (5) for drilling a graft recipient cavity into the targeted osteochondral region, said drill (5) extending along a longitudinal axis between a proximal end (58) and a distal end (59) having a cutting head part (51) located at the proximal end (58), the cutting head part (51) being comprised within a cylindrical geometrical envelope surface (510) of a first diameter (D5), and a coupling end part (54) located at the distal end (59) of the drill (5),• a drill guide (6) extending along a longitudinal axis between a proximal end (68) and a distal end (69) having:- a drill guiding portion (61) having a cylindrical guiding hole (610) of the first diameter (D5) extending along the longitudinal axis of the drill guide, the drill guiding portion (61) being configured to guide the drill (5) in translation along the longitudinal,- a bone-tissue engaging portion (62) located at said proximal end (68) having a sharpened edged rim perpendicular to the longitudinal axis configured to abut against the surface of the surgical site,• a dilator (7) extending along a longitudinal axis between a proximal end (78) and a distal end (79) having a dilating portion (71) located at its proximal end (78) configured to be inserted into the drilled graft recipient cavity, characterised in that the kit further comprises• a measuring adjusting device (8) for depth measurement of the graft recipient cavity as well as aiding the cutting of the graft to the measured size, said measuring adjusting device (8)• a graft insertion guide ( 100) having a body (101) extending along a longitudinal axis between a proximal end (108) and a distal end (109) having- a positioning resting surface (104) provided at said proximal end (108) configured to abut against a surface surrounding the drilled graft recipient cavity, and- a graft guiding hole (102) extending coaxially with said longitudinal axis into which the graft can be slidably fitted,- a window (103) formed in the vicinity of the proximal end (108), a shaping cup (110) in a cartilage -saving (soft) material, preferably plastic, configured to be mounted on the proximal end (78) of the dilator (7) and having a shaping surface (112) configured to contact the cap surface of the graft inserted into the graft recipient cavity, the shaping surface (112) being formed as a concave surface fitting to the cartilage surface, wherein the minimum diameter of the shaping cup is larger than the diameter of the graft, wherein the drill comprises:- a narrowed portion (52) adjacent to the cutting head part (51) having a second diameter (D52) smaller than the first diameter (D5), the narrowed portion (52) being configured to accommodate the debris of a drilling operation,- a guiding portion (53) located between the narrowed portion (52) and the distal end (59) of the drill (5), the guiding portion (53) having a cylindrical guiding surface of a diameter equal to the first diameter (D5), the guiding portion (53) being configured to be slidably and rotatably fitted within the drill guiding hole (610) of the drill guide (6).

2. The kit according to claim 1 wherein the measuring adjusting device (8) comprises- a measuring rod (80) extending along a longitudinal axis between a distal end (808) and a proximal end (809) provided at its proximal end (809) with an abutment surface (802) configured to abut against the bottom surface of the graft recipient cavity and a graft holding surface (804) provided at its distal end (809), the measuring rod having an outer guiding surface (803), wherein at least a portion of the outer guiding surface (803) is configured to be fitted in the drilled graft recipient cavity,- a tubular measuring sleeve (90) extending along a longitudinal axis between a proximal end (908) and a distal end (909), the tubular measuring sleeve (90) comprising a guiding through hole, wherein a graft can be slidably fitted in at least a section of the guiding through hole extending from the distal end (909) of the measuring sleeve (90), an abutment surface (901) provided at its proximal end (908) configured to abut against a surface surrounding the drilled graft recipient cavity, and a cut guiding surface (902) provided at its distal end (909) configured to guide a cutting device for cutting the graft fitted into the measuring sleeve (90), wherein the measuring rod (80) is slidably guided within the guiding through hole of the measuring sleeve (90),- the measuring sleeve (90) further comprising a securing means (85) for securing the measuring rod (80) at a desired position with respect to the measuring sleeve (90).

3. The kit according to any of claims 1 to 2, characterised in that the cutting head part (51) of the drill (5) is three-fluted, each flute being formed as a wing (511) radially extending from the longitudinal axis of the drill (5), the wing (511) having a lateral surface (512) extending between a base edge (512) and a top edge (514) inclined with respect to the longitudinal axis of the cutting head part 51 by an angle comprised between 3°and 20°, preferably comprised between 5° and 15°.

4. The kit according to claim 3, characterised in that the lateral surface (512) of the wing (511) of the cutting head part (51) is a planar surface defined by the base edge (512) and the top edge (514) each being straight edges.

5. The kit according to any of claims 1 to 4 wherein the shaping cup (110) has a concave shaping surface (112) having a radius essentially identical with the hyaline cartilage to be treated, preferably a radius of 70 to 90 mm, preferably 75 to 85 mm, more preferably 78 to 82 mm, in particular 80 mm.

6. The kit according to any of claims 1-5, characterised in that the drill guide (6) and the graft insertion guide (100) are each provided with a respective stylet (63,105) extending in a transverse direction with respect to the longitudinal axis of the drill guiding hole (610) and the graft guiding hole (102).

7. The kit according to any of claims 1-6, characterised in that the drill guiding portion (53) of the drill (5) is graduated.

8. The kit according to any of claims 1-7, characterised in that the measuring sleeve (90) of the measuring adjusting device (8) is provided with a graduated slot (903) extending from its distal end (909).

9. The kit according to any of claims 1-8, characterised in that the dilating portion (71) of the dilator (7) has a dilating ratio of 0.4 mm / 9 mm, the dilating ration being defined as the ratio of the total diameter increase along the length of the dilating portion (71) to the length of the dilating portion (71).

10. The kit according to any of claims 1-9, characterised in that the shaping cup (110) is made of a plastic material.

11. The kit according to any of claims 1-10, characterised in that the kit further comprises a tubular chisel (2) extending along a longitudinal axis between a proximal end (28) and a distal end (29), the chisel (2) having a graft accommodating portion (22) extending from its proximal end (28) and a cutting edge (21) provided at its proximal end (28), the cutting edge (21) having an inner angle comprised between 5° and 45°, preferably between 10° and 20°.

12. The kit according to claim 11, characterised in that the kit further comprises a chisel tamp (3) extending along a longitudinal axis between a first end (38) and a second end (39), and a chisel protection cup (4) extending along a longitudinal axis between a first end (48) and a second end (49), the chisel protection cup (4) being provided with a first receiving hole (41) extending from its first end (48) and with a guiding hole (42) extending from its second end (49), wherein the portion of the chisel (2) extending from its proximal end (28) is configured to be received in the first receiving hole (41) of the chisel protection cup (4) and the chisel tamp (3) is configured to be inserted and guided from its first end (38) in the guiding hole (42) of the chisel protection cup (4).

13. A method for performing equine mosaicplasty using the kit of any of claims 1-12, said method comprising:• determining a osteochondral region to be repaired,• providing and preparing an osteochondralosteochondral graft,• cutting the cartilage layer (cap) corresponding to said determined osteochondral osteochondral region by- abutting the bone-tissue engaging portion (62) of the drill guide (6) perpendicularly against the surface of said determined osteochondral region to be repaired and- sinking said bone-tissue engaging portion (62) into the corresponding cartilage portion preferably thereby cutting the sharped edged rim into the cartilage layer thereof,• drilling a graft recipient cavity of a desired depth based on the determined osteochondral region to be repaired, wherein drilling the graft recipient cavity comprising:- fitting the drill (5) into the drill guiding portion (61) of the drill guide (6),- driving the drill (5) into said determined osteochondral region until a desired depth,- wherein the drill (5) is guided with respect to the drill guiding hole (610) of the drill guide (6) by the guiding portion (53) of the drill (5),- optionally (if required) evacuating the drill waste from the cutting head part (51) of the drill (5) by transporting it toward the narrowed portion (52) of the drill (5) adjacent to the cutting head part (51),• dilating the drilled graft recipient cavity by inserting the dilating portion (71) of the dilator (7) into the graft recipient cavity until the proximal end (78) of the dilator (7) abuts against the bottom of the graft recipient cavity, maintaining the dilating portion in this inserted state for a predetermined period of time,• measuring the depth of the drilled graft recipient cavity by- fitting the measuring rod (80) of the measuring adjusting device (8) into the graft recipient cavity, until the abutment surface (801) of the measuring rod (80) abuts against the bottom of the graft recipient cavity,- engaging and sliding down the measuring sleeve (90) on the measuring rod (80) until the abutment surface (901) of the measuring sleeve (90) abuts against a surface surrounding the drilled graft recipient cavity,- securing the measuring sleeve (90) with respect to measuring rod (80) by means of the securing means (85),- determining the depth of the graft recipient cavity,- removing the measuring sleeve (90) from the graft recipient cavity,• cutting the graft at the measured length by- fitting the graft within the measuring sleeve (90) from the distal end (909) thereof until it abuts against the graft holding surface (804) of the measuring rod (80),- cutting the graft to size by guiding a cutting device at the cut guiding surface (902) of the measuring sleeve (90),• inserting the graft into the graft recipient cavity by- fitting the graft within the graft guiding hole (102) of the graft insertion guide (100),- abutting and positioning the graft insertion guide (100) by means of its positioning resting surface (104) provided at its proximal end (108) against the surface surrounding the drilled graft recipient cavity,-guiding the graft within the graft insertion guide in translation toward the graft recipient cavity, until the graft is inserted in the graft recipient cavity in a position in which the distal end of the graft protrudes from the bone surface of a given distance,-removing the graft insertion guide,• positioning and shaping the protruding surface of the graft with respect to the surrounding surface by mounting the shaping cup (110) on the proximal end (78) of the dilator (7),- positioning the shaping surface (112) of the shaping cup (110) on the protruding distal surface of the graft,- gently hammering the graft cap into the surface by hammering the shaping cup (110) mounted on the dilator (7) until the distal surface of the graft is in flush mate with the surrounding bone surface and the graft distal end is shaped at the desired shape, wherein the distance between the graft cap and the graft insertion cavity is visualized through the window (103) of the graft insertion guide (100).

14. The method according to claim 13, wherein the drill (5) is guided with respect to the drill guide (6) by the guiding portion (53) and at least a part of the cutting head part (51).

15. The method according to any of claims 13 to 14, wherein drill waste is stored in the space formed between the narrowed portion (52) and the surface of the drill guiding hole (610) of the drill guide (6).

16. The method of according to any of claims 13-15, wherein the graft is inserted into the graft insertion device (100) with the graft cap facing in the direction of the distal end (109) and then the graft is gently hammered down into the channel using the proximal end (78) side of the dilator (7) until the graft cap protrudes preferably just one mm above the surface.

17. The method of according to any of claims 13-16, wherein the graft is further pushed down, optionally gently hammered down, by the shaping cup ( 110) of a cartilage -saving (soft, preferably plastic) material, said shaping cup (110) having a shaping surface (112) configured to contact the cap surface of the graft inserted into the graft recipient cavity, wherein the minimum diameter of the shaping cup is larger than the diameter of the graft,the shaping surface (112) being formed as a concave surface fitting to the cartilage surface, thereby forming an even surface on the injured cartilage area.

18. The method of claim 17 wherein said shaping cup is configured to be mounted on the proximal end (78) of the dilator (7).

19. The method of claim 17 or 18, wherein the shaping cup (110) has a concave shaping surface (112) having a radius essentially identical with the hyaline cartilage to be treated, preferably a radius of 70 to 90 mm, preferably 75 to 85 mm, more preferably 78 to 82 mm, in particular 80 mm.

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