A patella bone plate system and set of bone plates comprising u-shaped plates with branch-offs and a hook

Abstract

A patella bone plate system (10) to secure patella (14) bone fractures through surgery, comprising: a distal plate (11) of substantially U – shaped, curved configuration with distally directed branch-off's (28; 28'; 29;29'), the U-shape having at a bottom region (12) thereof a distal hook (13) insertable through the patella distal tendon (15), and on either side of the distal hook (13) there is located a distal engagement hole (16; 16') at end of a distal branch-off (29; 29'), a proximal plate (17) to be located at a proximal patella region (18), free plate ends (19; 19') thereof each having a proximal engagement hole (20; 20') and an adjacent proximal hook member (21; 21'), and a pair of interconnection members (22; 22'; 23; 23') configured to engage and compressively interconnect the distal plate (11) and the proximal plate (17) by linking the distal engagement holes (16; 16') of the distal plate (11) with the proximal engagement holes (20; 20').

Description

[0001] A PATELLA BONE PLATE SYSTEM of the invention

[0002] The present invention relates to a patella bone plate system to secure patella bone fractures through surgery, as defined in the preamble of claim 1, and a set of patella bone plates, as defined in the preamble of claim 12.

[0003] Fractures of the kneecap constitute about 1% of all fractures, but are most frequent among young men and elderly women of 60 to 80 years, while the total incidence is estimated to 10.1 / 100 000 and of which about 1 / 3 require surgery.

[0004] If the fracture is displaced, the patient will not be able to extend the knee, and surgery is mandated.

[0005] The gold standard of surgical care is tension band wiring (TBW) and has been unaltered since the 1950s. It comprises the insertion of two 1.6 - 2.0 mm steel pins placed close to the joint surface with a figure-of-eight steel wire looped around the pins and on the front of the bone surface with documented partial failures in 22-30 % of cases and catastrophic failures in 5 - 14% of cases requiring revision surgery. Due to the weak bone / metal interface, movement after the operation is restricted, and weight-bearing exercises are generally postponed for 6-12 weeks.

[0006] The relatively long immobilisation period probably accounts for the permanent average loss of strength of about 31% compared to the uninjured limb. These poor results would not be acceptable in higher volume fractures, but probably due to the low incidence, little attention has been dedicated to kneecap fractures. Newer implants are commercially available, but their use is limited to more uncomplicated two-part fractures and the documentation is sparse.

[0007] The AO / OTA classification system divides patellar fractures into extra-articular (34A), partial articular (34B), and complete articular (34C) types. These types, and their subtypes, however, do not describe the actual fracture pattern and comminution zones where fractures ranges from simple fracture lines to severely complex fracture lines in all directions involving the distal pole in 59% in C fractures. This complexity of fracture patterns combined with an increasing osteoporotic elderly population calls for a more complete fixation system that can be adopted to the individual fracture.

[0008] The goal of patella fracture surgery is to perform an open reduction and internal fixation that secures the fracture to allow for early range of motion and non-weight bearing exercises to counter joint stiffness and muscle atrophy while the fracture heals.

[0009] In children, growth plates need to be respected, while in the adult population this is not so. Osteoporotic patients tend to have more complex fracture patterns with poor bone stock.

[0010] Locking plates are proven superior to regular cortical screws in osteoporotic bone and is therefore recommended in these patients. Newer plating options do not secure both the upper and lower aspects of the patella and base their design on a plate directly under the skin incision, with a reported infection risk of 3 - 10%.

[0011] Prior art

[0012] As mentioned in the background of the invention, Tension Band Wire (TBW) has been the gold standard of treatment since popularized by the AO in the 1950-60's. It consists of two smooth pins in the coronal plane that provide rotational stability and joint alignment and a figure-of-eight steel wire where each loop is placed under the pins through the patella tendon distally and the quadriceps tendon proximally and crosses on the anterior surface.

[0013] Theoretically, this neutralizes the distraction forces on the anterior surface and in flexion, exerts compression forces on the dorsal surface. This theoretical principle does not work in complex fracture patterns where the dorsal surface in not intact and has not been confirmed in biomechanical studies. However, it is a cheap and simple fixation method and is considered to be the gold standard despite questionable results.

[0014] A modification to the principles of TBW is the use of Cannulated Screws which replace the smooth pins, and where the wire is instead inserted through the screws. This option has shown better stability than TBW in some studies in simple fracture patterns.

[0015] Other prior art approaches are e.g. superior plates and lateral plates. Superior plates are commercially available in multiple plate configurations, and where the plate is placed on the entire anterior surface of the damaged knee-cap / patella with locking screws directed from anterior to posterior. The advantage is that the plate is placed on the tension side of the patella. Disadvantages is that they are placed directly under the incision, with the inherent risk of infection and the anterior placement may result in more implant irritation with subsequent need of implant removal.

[0016] Lateral plates relate to the other prior art types of plate configuration. With such a plate configuration, the plate is placed on one or both sides just anterior to the medial and lateral patellofemoral ligaments, conjoining distally over the patella. The advantage is that the plate is placed away from the incision, potentially more soft tissue friendly, but is not placed on the tension side of the patella. An example of such lateral plate is a distal plate of substantially U - shaped, curved configuration made by Koenigsee hnplantate GmbH (Patella-Platte 3.5 ws).

[0017] Another aspect is that neither lateral, nor superior plates secure the distal pole of the patella well. Some of the plates have therefore incorporated distal hooks to secure some kind of distal fixation that cannot be fixated with anterior screws. None of the prior art lateral or superior exhibit proximal hooks to secure the proximal fragments of the fractured patella.

[0018] Finally, it should be mentioned that most types of patella plates offer suture options through exhibiting a plurality of small holes of about 1.4 mm to allow for temporary pin placement during the reposition, and later for suture augmentation of the patella and quadriceps tendon.

[0019] Summary of the invention

[0020] The patella bone plate system of the invention is intended to more properly secure into position both the proximal and distal poles of the damaged patella with controlled compression, and simultaneously present as little as possible plate structure under the surgery incision in order to potentially reduce the risk of infection and implant irritability.

[0021] The system comprises a distal plate of substantially U - shaped, curved configuration, the distal plate being provided with a plurality of distally directed branch-offs, the distal plate at a bottom region of the U- shape having a distal hook configured to be inserted through the patella tendon, and at the bottom region on either side of the distal hook there is located a distal engagement hole at an end of one of the branch-offs, a proximal plate being configured to be located at a proximal region of the patella, proximal free ends of the proximal plate each having a proximal engagement hole and an adjacent proximal hook member, and a pair of interconnection members being configured to engage and compressively interconnect the distal plate and the proximal plate by linking each pair of a distal engagement hole and a proximal engagement hole, respectively.

[0022] Further embodiments of the patella bone plate system will appear from the associated subclaims, and the detailed description with reference to the attached drawing illustrating nonlimiting embodiments of the invention.

[0023] The set of patella bone plates to secure patella bone fractures through surgery comprises: a distal plate of substantially U - shaped, curved configuration, the distal plate being provided with a plurality of distally directed branch-offs , the distal plate at a bottom region of the U- shape having a distal hook configured to be inserted through the patella tendon, and at the bottom region on either side of the distal hook there is located a distal engagement hole at an end of one of the branch-offs, and further a proximal plate being configured to be located at a proximal region of the patella, proximal free ends of the proximal plate each having a proximal engagement hole and an adjacent proximal hook member, and the proximal plate and the distal plate being configured to be compressively co-operative upon linking the proximal holes with the distal holes.

[0024] Further embodiments of the set of patella bone plates will appear from the associated subclaims, and the detailed description with reference to the attached drawing illustrating nonlimiting embodiments of the invention.

[0025] Fig. 1 is a front view of the patella bone plate system of the invention.

[0026] Fig. 2 is a top view of the system.

[0027] Fig. 3 is a side view of the system from one side.

[0028] Fig. 4 is a perspective front view of the system as seen from one side and slightly from above.

[0029] Fig.5 is a partial side view of the proximal plate of the system. Fig.6 is a front view of the patella bone plate system of the invention shown installed on a sample patella bone.

[0030] Fig. 7 shows the system as installed on the sample patella bone and viewed from a proximal region of patella bone towards its distal region.

[0031] Fig. 8 is a side view of the system from one side as installed on the sample patella bone.

[0032] Fig. 9 is a perspective front view of the system as seen from one side and as installed on the sample patella bone.

[0033] Fig.10 shows the system as installed on the sample patella bone and viewed from a distal region of the patella bone towards its proximal region.

[0034] Detailed description

[0035] The patella bone plate system 10, according to the invention, exhibits a distal plate 11 of substantially U - shaped, curved configuration. The distal plate 11 has at a bottom region 12 of the U- shape has a distal hook 13 configured to be inserted through the patella distal tendon (not shown), i.e. just below the distal pole 15 of the patella 14. At the bottom region 12 on either side of the distal hook 13 there is located an oblique screw hole 16, 16’.

[0036] Further, a proximal plate 17 is configured to be located at a proximal pole region 18 of the patella 14, and the free ends 19; 19’ of the proximal plate each have a screw hole 20; 20’ and an adjacent proximal hook member 21; 21’. In the non-limiting embodiment shown, the proximal plate 17 has a substantially U-shaped configuration.

[0037] The system also comprises a pair of cannulated interconnection screws 22; 22’ with associated end nuts 23; 23’. This pair of screws and their nuts are configured to interconnect the distal plate 11 and the proximal plate 17, each screw 22; 22’ with nut 23; 23’ extending between and engaging one of the oblique screw holes 16; 16’ of the distal plate 11 and one of the free end holes 20; 20’ of the proximal plate 17. The oblique screw holes 16; 16’ are suitably each located on a distally directed branch-off 29; 29’ from the respective leg 11’; 11” of the distal plate 11.

[0038] The distal plate has a locking screw hole 24 which is located at a bottom mid-point 12’ of the U-shape of the distal plate 11 at a root location 13’ of the distal hook 13. Further, a proximal locking screw hole 25 is located at a bottom mid-point 17’ of the U-shape of the proximal plate 17.

[0039] It is also noted each leg 11’; 11” of the U-shaped distal plate 11 is provided with a plurality of securing screw holes 26; 26’ to selectively receive a patella part securing screw based on surgical judgement during an operation procedure. It is noted that at least one of the securing screw holes 27: 27’ on each leg is located on a distally directed branch-off 28; 28’ from the leg 11’; 11”.

[0040] It will be appreciated that the distal plate 11, the proximal plate 17, and the interconnection screws 22; 22’ with nuts 23; 23’ should all be made from a bio-compatible material.

[0041] The present invention with its distal plate 11, its proximal plate 17 and their interconnecting screws 22; 22’ and nuts 23; 23’ effectively secure the distal pole 15 and the proximal pole 18 to exert controlled joint compression between the two.

[0042] The distal pole 15 is secured with the solid hook 13 being inserted through an incision in the patella tendon. On the sides, the distal pole 15 is secured with the buttress effect of the two oblique screw holes 16; 16’ and subsequently in interaction with the screws 22; 22’.

[0043] It will be appreciated that the patella body 14 can be further secured by the placement of locking, cortical or variable locking screws (not shown) entered through any one of the holes 26; 26’; 27; 27’ at the surgeon's discretion at angles to the prevailing distraction forces. The body 14 is also substantially supported by the distal and proximal fixation of the poles 15; 18 through use of the interconnecting screws 22; 22’ and their screws 23; 23’.

[0044] The proximal plate 17 is connected to the distal plate 11 with the interconnecting cannulated screws 22; 22’ and with the associated proximal nut 23; 23’. Using a jig (not shown) to locate the distal plate 11 and the proximal plate in proper mutual positions, a guidewire (not shown) is inserted through the distal plate's two oblique holes 16; 16’ and through the corresponding two holes 20; 20’ in the proximal plate 17. A 4.0 mm diameter drill bit is used, the guide wire is introduced and then the cannulated screw 22; 22’ and nut 23; 23’ is inserted over the guide wire from distal end, and the nut is thread onto the screw from the proximal end. This provides controlled compression between the two poles. It will be appreciated by the expert in the art that most parts of the main implant are not situated directly under the incision, which is beneficial both with respect to avoid infection and implant irritation. The controlled compression is beneficial for reduction of the fracture on the patella and inherently for optimizing the healing process. After the fracture is healed, the implant may be removed at the surgeon's discretion.

[0045] It should be mentioned that surgical management of patella fractures is indicated when there is a step in the joint surface of more than 2 mm or there is present a disruption of the extensor mechanism. The soft tissue envelope must be optimized preoperatively. The implants are connected to an aiming device, i.e. an installation aid jig intraoperatively by the responsible healthcare personnel.

[0046] After reduction and temporary fixation of the patella fracture(s) with pins (not shown), the proximal plate 17 and distal plate 11 are secured to the aiming device. The distal plate 11 is placed first with the hook 13 inserted through a longitudinal incision in the patella tendon. The distal plate 11 is then temporarily secured with two distal pins or more. The proximal plate 17 is then placed with the two holes 20; 20Tor the connecting screws placed into position through longitudinal incisions through the quadriceps tendon and the proximal plate 17 is then temporarily secured with pins through the plate pin holes 30, 30’. Compression in then made through the aiming device at the surgeon's discretion. Drill sleeves for the 4.0 mm diameter drill bit is placed through the aiming device in the two holes 16; 16 and drilled through the holes 20; 20’ proximally. The drill bit and sleeves are removed, and a long metal guide wire is placed through the hole. The cannulated screws 22, 22’ and proximal cannulated nuts 23, 23’ are attached to two cannulated screw drivers, and advanced towards each other over each end of the wire and the proximal plate 17 and distal plate 11 are then secured to each other and further compression is obtained between the implants, i.e. the plates 11; 17, as needed. The aiming device / jig is removed and the remaining locking holes 24; 25 and at least some of the screw holes 26; 26’; 27; 27’ are then used to secure the patella fracture.

[0047] The aiming device / jig is not shown, but will have has two ends where the proximal and distal plates 17; 11 are fastened with a screw through the aiming device and plate. There are two trochars distally and proximally to fit with the plates. Into these trochars, a drill sleeve can be attached for the 4.0 mm diameter drill bit. The two ends of the aiming device are attached with a compression device that can compress the two plates 11; 17 towards each other. It will be appreciated that the aiming device / jig enables compression between the distal and proximal poles of the patella, and provides for holes for drilling, pins and screws.

[0048] The hole is large enough to accommodate the screw head. In view thereof it is at first inserted a metal sleeve into the hole having a more narrow channel: 4 mm for a 4 mm diameter drill bit. The sleeve is typically 5-8 cm long and guides the drill bit in proper direction. Following the drilling, the sleeve is removed, and a long pin is suitably entered (normally with noncannulated screws as the screws are thereafter entered), exiting at the other side of the patella and through the proximal plate 17. Thereafter, the cannulated screw 22; 22’ is entered over the pin from distal position of the system and at the same time the cannulated nut 23; 23’from the proximal position of the system. The screwdrivers used should be cannulated in order to properly carry out the operation of installing the screws 22; 22’ and nuts 23 ; 23 ’ .

[0049] It is noted that also the distal plate 11 has plate pin holes 31; 31 to temporarily secure the distal plate 11.

[0050] Although the compressive interconnection members have been described as cannulated screws (22; 22’) with associated nuts (23; 23’), it lies within the concepts of the invention as an alternative to use non-cannulated screws with associated nuts. Suitably, such alternative interconnection members are made of a bio-compatible material.

Claims

CLAIMS1. A patella bone plate system (10) to secure patella (14) bone fractures through surgery, the system comprising: a distal plate (11) of substantially U - shaped, curved configuration, wherein the distal plate (11) is provided with a plurality of distally directed branch-off s (28;28’; 29;29) , wherein the distal plate (11) at a bottom region (12) of the U- shape has a distal hook (13) configured to be inserted through the patella tendon, and wherein at the bottom region (12) on either side of the distal hook (13) there is located a distal engagement hole (16; 16’) at an end of one of the branch-of s (29; 29’), a proximal plate (17) being configured to be located at a proximal region (18) of the patella (14), wherein proximal free ends (19; 19’) of the proximal plate (17) each have a proximal engagement hole (20; 20’) and an adjacent proximal hook member (21; 21’), and a pair of interconnection members (22; 22’; 23; 23’) configured to engage and compressively interconnect the distal plate (11) and the proximal plate (17) by linking each pair of a distal engagement hole (16; 16’) and a proximal engagement hole (20; 20’), respectively.

2. The patella bone plate system (10) of claim 1, wherein a locking screw hole (24) is located at a bottom mid-point (12’) of the U-shaped part of the distal plate (11) at a root location (13’) of the distal hook (13).

3. The patella bone plate system (10) of claims 1 or 2, wherein the proximal plate has a U- shaped configuration.

4. The patella bone plate system (10) of claim 1 or 2, wherein a locking screw hole (25) is located at a bottom mid-point (17’) of the proximal plate (17).

5. The patella bone plate system (10) of claim 3, wherein a locking screw hole (25) is located at a bottom mid-point (17’) of the U-shape of the proximal plate (17).

6. The patella bone plate system (10) of any one of claims 1 - 5, wherein each leg (11’; 11”) of the U-shaped part of the distal plate (11) is provided with a plurality of securing screw holes (26; 26’; 27; 27’) to selectively receive a patella part securing screw.

7. The patella bone plate system (10) of claim 6, wherein at least one of the securing screw holes (27; 27’) on each leg (11’; 11”) is located at an end of another one of the distally directed branch-off’s (28; 28’) which extends from the leg.

8. The patella bone plate system (10) of any one of claims 1 - 7, wherein the distal plate, the proximal plate and the interconnection members are made from a bio-compatible material.

9. The patella bone plate system (10) of any one of claims 1 - 8, wherein the distal attachment holes (16; 16’) have an oblique orientation.

10. The system of any one of claims 1 -9, wherein each of the compressive interconnection members comprises an interconnection screw (22; 22’) with associated end nut (23; 23’) configured to interconnect the distal plate (11) and the proximal plate (17), each screw with associated nut extending between and engaging one of the distal engagement holes (16; 16’) of the distal plate (11) and one of the proximal engagement holes (20; 20’) of the proximal plate (17).

11. The system of claim 10, wherein the interconnection screw (22; 22’) is a cannulated interconnection screw.

12. A set of patella bone plates (11; 17) to secure patella (14) bone fractures through surgery, the set comprising: a distal plate (11) of substantially U - shaped, curved configuration, wherein the distal plate (11) is provided with a plurality of distally directed branch-off s (28;28’; 29;29) , wherein the distal plate (11) at a bottom region (12) of the U- shape has a distal hook (13) configured to be inserted through the patella tendon, and wherein at the bottom region (12) on either side of the distal hook (13) there is located a distal engagement hole (16; 16’) at an end of one of the branch-of s (29; 29’), and a proximal plate (17) being configured to be located at a proximal region (18) of the patella (14), wherein proximal free ends (19; 19’) of the proximal plate (17) each have a proximal engagement hole (20; 20’) and an adjacent proximal hook member (21; 21’), and wherein the proximal plate (17) and the distal plate (11) are configured to be compressively co-operative upon linking the proximal engagement holes (20; 20') with the distal engagement holes (16; 16').

13. The set of patella bone plates (11; 17) of claim 12, wherein a locking screw hole (24) is located at a bottom mid-point (12’) of the U-shaped part of the distal plate (11) at a root location (13’) of the distal hook (13).

14. The set of patella bone plates (11; 17) of claims 12 or 13, wherein the proximal plate has a U-shaped configuration.

15. The set of patella bone plates (11; 17) of claim 12 or 13, wherein a locking screw hole (25) is located at a bottom mid-point (17’) of the proximal plate (17).

16. The set of patella bone plates (11; 17) of claim 14, wherein a locking screw hole (25) is located at a bottom mid-point (17’) of the U-shape of the proximal plate (17).

17. The set of patella bone plates (11; 17) of any one of claims 12 - 16, wherein each leg (11’; 11 ”) of the U-shaped part of the distal plate (11) is provided with a plurality of securing screw holes (26; 26’; 27; 27’) to selectively receive a patella part securing screw.

18. The set of patella bone plates (11; 17) of claim 17, wherein at least one of the securing screw holes (27; 27’) on each leg (11’; 11”) is located at an end of another one of the distally directed branch-off’s (28; 28’) which extends from the leg.

19. The set of patella bone plates (11; 17) of any one of claims 12 - 18, wherein the distal plate and the proximal plate are made from a bio-compatible material.

20. The set of patella bone plates (11; 17) of any one of claims 12 - 19, wherein the distal engagement holes (16; 16’) have an oblique orientation.

21. The set of patella bone plates (11; 17) of any one of claims 12 - 20, wherein each pair of proximal engagement hole (20; 20') and distal engagement hole (16; 16') is configured to be linked by means of a compressive interconnection member comprising an interconnection screw (22; 22’) with associated end nut (23; 23’),22. The set of patella bone plates of claim 21, wherein the interconnection screw (22; 22’) is a cannulated interconnection screw.

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