External fixator, kit comprising an external fixator, and method for fixation

Abstract

The present invention provides an external fixator (1) for the fixation of joints such as the proximal interphalangeal (PIP) joint of the finger and a kit comprising a pair of such external fixators (1). The external fixator (1) comprises a rigid planar member made of a radiolucent material. The planar member comprises a circular through-hole (6) and a linear main slot (10) radially aligned with the through-hole (6). The external fixator (1) can also comprise a circular arc (8) of a radiopaque material centered on the through-hole (6), a tail (14) to assist its manipulation, and one or more auxiliary slots (20). The main and auxiliary slots (10, 20) have a toothed inner surface. In addition to the pair of identical external fixators (1), the kit may further comprise a plurality of Kirschner wires and one or more stoppers (not shown). In use, the pair of external fixators are placed laterally on each outer side of the patient's finger, and a first Kirschner wire of the Kirschner wires passes through the through-hole (6) in each external fixator (1) and is inserted through the condyle or head of the proximal phalanx. A second Kirschner wire of the Kirschner wires passes through the main slot (10) in each external fixator (1) and is inserted through the middle phalanx. A third Kirschner wire passes through a convenient auxiliary slot of the auxiliary slots (20) in each external fixator (1) and is inserted through, over, or under the middle phalanx or a bone fragment thereof. Movement of the second Kirschner wire along the main slot (10) in the direction of arrow D can be used to apply traction to the joint. Movement of the third Kirschner wire along one of the auxiliary slots of the auxiliary slots (20) towards the main slot (10) can be used to reduce subluxation of the middle phalanx or a bone fragment thereof. One or more stoppers engaging the toothed inner surfaces of the main and auxiliary slots (10, 20) then prevent rearward movement of the Kirschner wires along the main and / or auxiliary slots (10, 20). The present invention also provides a method comprising providing a pair of such external fixators (1) for use in surgery.

Description

[Technical Field]

[0001] The present invention relates to an external fixator for fixation of fractured joints, a kit comprising at least a congruent pair of such external fixators, and a method of using a pair of such external fixators in a surgical procedure. The external fixator of the present invention is particularly suitable for fixation of fractured joints within the digit (i.e., within the finger or toe), such as the proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints of the fingers, but may also be used for fixation of fractured wrist joints, such as joints exhibiting die-punch injuries, for example. [Background technology]

[0002] The proximal interphalangeal (PIP) joint is located in each of the fingers of the human hand between the condyle or head of the proximal phalanx (P1) and the base of the middle phalanx (P2). The distal interphalangeal (DIP) joint is located in each of the fingers of the human hand between the condyle or head of the middle phalanx (P2) and the base of the distal phalanx (P3). The PIP and DIP joints can sustain one of several different fracture injuries requiring surgical intervention. These fracture injuries include subluxation of bones and bone fragments in both the dorsal (back of the hand) and volar (palm) directions, pilon fractures, compression of one or more bone fragments, and larger comminution of the bone. The goals of managing such fractures are to reduce subluxation and dislocation of the bones and bone fragments and to restore joint congruity whenever possible. These goals can be met in several different ways, depending on the fracture configuration and the degree of bone fragmentation.

[0003] A common surgical technique used to manage such injuries is ligamentotaxis. In ligamentotaxis, traction (pulling) forces are applied to the fractured joint. When traction is applied, the collateral ligaments and other soft tissues around the joint tighten and help pull any attached bone fragments into a predetermined alignment.

[0004] Several devices exist in the prior art for applying traction to the PIP joint. In order for traction to be applied to a fractured joint, such devices must be mechanically connected to the joint on both the proximal and distal sides of the fracture. This is typically accomplished by passing a Kirschner wire (K-wire) laterally through the fingers on each side of the fracture, then applying traction to the inserted K-wire.

[0005] The first known device for applying traction to an inserted K-wire is the Allison device, described in Ng, CY and Oliver, CW: "Fractures of the Proximal Interphalangeal Joint of the Fingers," Journal of Bone & Joint Surgery (June 2009), Vol. 91-B, No. 6, pp. 705-12. In the Allison device, a pair of torsion springs are placed under tension and attached to the K-wires proximal and distal to the fracture, pulling the K-wires apart. This device has several drawbacks: First, the Allison device is difficult to adjust. Second, the Allison device cannot be used to correct any subluxations or realign compressed bone fragments. Third, the traction force applied to the K-wire by the torsion springs depends on the amount of tension the torsion springs are initially applied to and cannot be easily controlled.

[0006] A second known device is the Suzuki frame, described in Suzuki, Y., Matsunaga, T., Sato, S., and Yokoi, T.: "The Pins and Rubbers Traction System for Treatment of Comminuted Intraarticular Fractures and Fracture-Dislocations in the Hand," Journal of Hand Surgery (Edinburgh, Scotland) (February 1994), Vol. 19, No. 1, pp. 98-107. In the Suzuki frame, a long proximal K-wire is bent vertically at both ends to complete the distal portion of the distal K-wire. Hooks are bent onto the ends of both the proximal and distal K-wires, and then a pair of elastic bands are stretched between and attached to the hooks on the proximal and distal K-wires on each lateral side of the finger to separate the K-wires. The traction force can be controlled by adjusting the number of twists and / or loops in each elastic band. However, this control is not precise. A third K-wire can be inserted laterally in a similar manner to correct the subluxation. However, this correction of the subluxation is not dynamic or adjustable without removing the third K-wire and reinserting it in a new position. Third, the Suzuki frame cannot be used to correct the central fragment of a pilon fracture.

[0007] A third known device is the Hynes and Giddins device, described in Hynes, MC, and Giddins, GE: "Dynamic External Fixation for Pilon Fractures of the Inter-Phalangeal Joints," Journal of Hand Surgery (Edinburgh, Scotland) (April 2001), Vol. 26, No. 2, pp. 122-124. In the Hynes and Giddins device, the proximal and distal K-wires are bent into a Z-shape to compress them together. The traction force can be controlled by adjusting the angle of the Z-shape within the wire arms. However, this control is not precise. A third K-wire can be inserted laterally in a similar manner to correct subluxation. However, the Heinz and Giddins device suffers from the same drawbacks as the Suzuki frame in that the correction of the subluxation is not dynamic or adjustable without removing and reinserting the third K-wire into a new position, and the Heinz and Giddins device cannot be used to correct the central fragment of a pilon fracture.

[0008] Another known device is the "Banjo" splint, originally described in Robertson, RC, Cawley, JJ, and Faris, AM: "Treatment of Fracture-Dislocation of the Interphalangeal Joints of the Hand," Journal of Bone Joint Surgery (1946), No. 28, pp. 68-70. The "Banjo" splint was similarly modernized in Schenck, RR: "Dynamic Traction and Early Passive Movement for Fractures of the Proximal Interphalangeal Joint," Journal of Hand Surgery [of America] (1986), No. 11, pp. 850-858. However, the Banjo splint is cumbersome due to its large external frame and cannot be used to correct any subluxations or realign compressed bone fragments, for example, in a pilon fracture.

[0009] Other prior art devices are also described in U.S. Patent Nos. 6,565,563B and 8,246,561B, both assigned to John M. Agee, U.S. Patent Application Publication No. 2012 / 0029517A to Virak Tan, and EP 0512792 to Smith & Nephew Richards, Inc.

[0010] Further prior art is described in CN109171844A, GB2489471A, and CN102783998A. CN109171844A describes an osteotomy device used in tibial and femoral osteotomies, which functions to spread and fix bone sutures. GB2489471A describes a finger fixator comprising a two-part elongated strut element and two spaced-apart pin-engageable elements on the two-part elongated strut element. The two-part elongated strut element includes a spacing adjustment means for selectively adjusting and setting the spacing between the two pin-engageable elements. The spacing adjustment means may take the form of a rotatable member or a releasable sliding or telescoping mechanism. The strut element may have spaced-apart arcuate arms for receiving pins. CN102783998A describes a hinged traction external fixation device with two parallel screws, a rotating central pin, a maintaining reset pin, a fixing and tensioning pin and a nut. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Patent No. 6,565,563 B [Patent Document 2] U.S. Patent No. 8,246,561 B [Patent Document 3] U.S. Patent Application Publication No. 2012 / 0029517 A [Patent Document 4] EP0512792 A [Patent Document 5] CN109171844 A [Patent Document 6] GB2489471 A [Patent Document 7] CN102783998 A Summary of the Invention [Problem to be solved by the invention]

[0012] It is therefore an object of the present invention to provide an improved external fixator for fixation of a fractured joint, a kit comprising at least a pair of such external fixators, and a method of using a pair of such external fixators in a surgical procedure. [Means for solving the problem]

[0013] Thus, in a first aspect, the present invention provides an external fixator for fixation of a fractured joint. The fixator comprises a rigid, planar member having a pair of parallel, opposing sides. The planar member comprises a circular through-hole perpendicular to the parallel, opposing sides and a linear main slot connecting the parallel, opposing sides. The main slot is radially aligned with the through-hole and has a toothed inner surface.

[0014] As used herein, the term "external" means external to the patient's body. Such an external fixator has the following advantages: Take for example, when an external fixator is used for fixation of the proximal interphalangeal (PIP) joint, the circular through-hole of the external fixator provides a drill guide for inserting a first Kirschner wire through the condyle or head of the proximal phalanx P1 by first marking the patient's skin with a dot through the through-hole and then inserting the first Kirschner wire laterally through the head of the proximal phalanx P1 at the location of the dot.

[0015] Once the first Kirschner wire has been so inserted, a second Kirschner wire can be inserted laterally into the middle phalanx P2 at a convenient location distal to the fracture complex, taking care to ensure that the second Kirschner wire is parallel to the first. The external fixators of the present invention can be inserted over the first and second Kirschner wires, one on each lateral side of the finger, by passing the first Kirschner wire through the circular through-holes of each external fixator and the second Kirschner wire through the main slots of each external fixator. Traction can then be applied to the PIP joint by increasing the separation between the first and second Kirschner wires by moving the second Kirschner wire along the main slots away from the through-holes.

[0016] The toothed inner surface of the main slot advantageously acts as a ratchet, controlling the application of this traction force and helping to prevent the second Kirschner wire from sliding back toward the through-hole. Once the required amount of traction force has been applied, the second Kirschner wire can then be locked in place. This can be done, for example, by inserting a stopper into the main slot on the side of the second Kirschner wire closest to the through-hole, or by bonding the second Kirschner wire to the planar member, or both. Alternatively or additionally, another Kirschner wire, pin, or screw with a wall thickness greater than the width of the main slot can be inserted into the main slot on the side of the second Kirschner wire closer to the through-hole, thereby digging into the planar member on either side of the main slot where the thicker Kirschner wire, pin, or screw is inserted. Because the thicker Kirschner wire, pin, or screw is thicker than the main slot, it cannot slide along the main slot in either direction. The exposed ends of the first and second Kirschner wires, and, if used, the exposed ends of any thicker-walled Kirschner wires, pins, or screws, may then be bent out of the way and / or reduced in size.

[0017] Furthermore, the external fixator of the present invention has the advantage that it can also be used to realign a bone fragment that has been impacted distally into the middle phalanx P2 by inserting another Kirschner wire through the main slot in the external fixator between the impacted bone fragment and the middle phalanx P2. If this other Kirschner wire moves along the main slot in a direction toward the through-hole in the external fixator while the second Kirschner wire holds the middle phalanx P2 in place relative to the proximal phalanx P1, this movement of the other Kirschner wire pushes the bone fragment toward the head of the proximal phalanx P1, returning the bone fragment to alignment.

[0018] Advantageous embodiments of the present invention may be configured according to any of the claims and / or parts of the following description.

[0019] In some embodiments, the toothed inner surface of the primary slot can include a first plurality of teeth, each tapering along the primary slot and away from the through-hole, which has the advantage that such teeth provide a ratchet that prevents movement of a Kirschner wire inserted through the primary slot toward the through-hole, so that the Kirschner wire can be held within the primary slot to apply a traction force to P2.

[0020] In some embodiments, the rigid planar member may be made of a radiolucent material, and the external fixator may further include a circular arc of radiopaque material centered on the through-hole. Making the rigid planar member radiolucent allows for x-ray imaging of the fractured joint undergoing fixation through the rigid planar member. Providing an external fixator with such an arc of radiopaque material has the advantage of providing a guide that allows the circular through-hole of the fixator to be aligned with the center of rotation of the condyle or head of the proximal phalanx P1 by carefully aligning the arc of radiopaque material with the contour of the head of the proximal phalanx P1 so that both the arc and the head appear on an x-ray image. Once positioned in this manner, the patient's skin can be marked with a dot through the circular through-hole of the external fixator to indicate the center of rotation of the head of P1.

[0021] In some embodiments, the rigid planar member can further include an auxiliary slot connecting the parallel opposing sides, the auxiliary slot extending obliquely away from the through-hole relative to the main slot and having a toothed inner surface. The addition of such an auxiliary slot has the advantage that the external fixator can be used to reduce subluxation of the middle phalanx P2 or its fragments and also to apply traction to the PIP joint. Because the auxiliary slot is oblique to the main slot, movement of the Kirschner wire along the auxiliary slot can be used to apply a corresponding oblique force to the middle phalanx P2 or its fragments. The toothed inner surface of the auxiliary slot has the advantage of acting as a ratchet, helping to control the movement of the Kirschner wire and prevent it from sliding back in the opposite direction.

[0022] In some embodiments, the toothed inner surface of the auxiliary slot can include a second plurality of teeth, each tapering in a direction along the auxiliary slot and toward the main slot, which has the advantage that such teeth provide a ratchet that impedes movement of a Kirschner wire inserted through the auxiliary slot in a direction toward the main slot.

[0023] The auxiliary slot may be curved. If so, the direction of the curve is preferably from the through hole toward the opposite end of the main slot. Preferably, however, the auxiliary slot is straight. This has the advantage that the amount of force that can be applied to the middle phalanx P2 or its fragments by moving the Kirschner wire along the auxiliary slot can be more easily controlled.

[0024] In some embodiments, the rigid planar member may include multiple auxiliary slots arranged parallel to one another, which has the advantage that the multiple auxiliary slots provide corresponding different locations for the insertion of Kirschner wires through, onto, or underneath the middle phalanx P2 or its fragments, thereby allowing subluxation thereof to be corrected in a wide range of different fractures.

[0025] In some embodiments, the rigid planar member may include two such auxiliary slots, each located on an opposite side of the main slot, and the two auxiliary slots may be reflection-symmetric with respect to a line on which the main slot lies. This has the advantage that one auxiliary slot of the auxiliary slots may be used to reduce dorsal subluxation of the middle phalanx P2 or its fragments, and the other auxiliary slot of the auxiliary slots may be used simultaneously to reduce palmar subluxation of the middle phalanx P2 or its fragments.

[0026] In some embodiments, the toothed inner surface of the primary slot can include a third plurality of teeth located closer to the through-hole than the first plurality of teeth, each tapering along the primary slot toward the through-hole. This has the advantage that such teeth provide a ratchet that prevents movement of a Kirschner wire inserted through the primary slot away from the through-hole. Thus, the Kirschner wire may be held in the primary slot in a position that realigns bone fragments in the pilon fracture toward the through-hole and toward the head of the proximal phalanx P1, while another Kirschner wire applies traction to P2 in an opposite direction by the first plurality of teeth.

[0027] In some embodiments, the rigid planar member can have a shape that is mirror-symmetrical about the longitudinal axis, with the through-holes and primary slots lying on the longitudinal axis. If so, this has the advantage that the rigid planar member does not have a preferred orientation because it is not chiral, and therefore can be used on either side of a finger undergoing fixation of the PIP joint without first needing to be oriented in the correct direction, thereby saving time during surgery.

[0028] When the rigid planar member has a shape that is mirror-symmetric as just described, and the external fixator further comprises an arc of radiopaque material, in some embodiments, each end of the arc may define an angled line with the longitudinal axis, the angle being in the range of 100 degrees to 140 degrees, inclusive. This has the advantage that if the external fixator is rotated through the same angle that is not aligned with the joint being fixed, the arc will be brought into alignment with the contour of the condyle or head of the proximal phalanx P1 in an x-ray image, yet the external fixator can still be easily manipulated by the surgeon without obstructing the x-ray image.

[0029] If the rigid planar member has a shape that is mirror symmetric as just described, The shape of the rigid planar member may be any one of oblong, elliptical, oval, ovate, obovate, spatulate, rhomboidal, and deltoid. These preferred shapes have the advantage that one of the preferred shapes may be selected to match the shape of the tip of the finger that will receive fixation of the PIP joint, which aids in alignment of the fixator with the finger during surgery.

[0030] Alternatively, the rigid planar member may include a tail located at the opposite end of the main slot from the through-hole. Such a tail has the advantage of providing a handle that can be used by the surgeon to hold and manipulate the fixator during surgery. Because it is particularly desirable to avoid exposing the surgeon's fingers to X-rays during fluoroscopy of the patient through the rigid planar member, the tail provides a handle by which the fixator can be manipulated using instruments such as arterial clips or tourniquets. However, because the tail does not conform to the shape of the tip of the finger receiving fixation of the PIP joint, there is no risk that such manipulation of the fixator will interfere with the finger.

[0031] If the rigid planar member does include such a tail, the tail preferably has a delta-shaped or branched shape and a flat or concave surface at the opposite end of the rigid planar member from the through-hole. This has the advantage that the flat or concave surface provides a convenient surface against which the surgeon can press when moving the Kirschner wire along the main slot away from the through-hole to hold the external fixator in place as the Kirschner wire is moved relative to the fixator. Furthermore, if the tail actually has such a delta-shaped or branched shape, the rigid planar member as a whole will have the appearance of a fish, with the through-hole and main slot respectively resembling the eye and spine of a fish, and, if one or more auxiliary slots are also present in the rigid planar member, other bones of the fish radiating from the spine. This fish-like appearance has the advantage that it can be useful when training surgeons in the use of the fixator to accelerate identification of specific parts of the fixator and to avoid miscommunication, thereby saving time during surgery.

[0032] In some embodiments, the arc of radiopaque material can be embedded within and enclosed by a rigid planar member. This has the advantage that if the radiopaque material comprises, for example, a metal, while the rigid planar member is, for example, an inert plastic material, the radiopaque material can be protected from corrosion by the rigid planar member, and conversely, there is no risk of the radiopaque material interacting with other surgical elements (such as Kirschner wires) or with the patient's fingers or other extremities once the fixator is in place, for example, if the patient is allergic to certain metals. However, in other embodiments, the arc of radiopaque material can instead be provided as an insert within the planar member for ease of manufacturing.

[0033] In a second aspect, the present invention also provides a kit comprising a pair of congruent external fixators described herein. As used herein, the term "congruent" means that the pair of external fixators is geometrically congruent with one another. Such a kit has the advantage of providing a pair of external fixators that have the same shape and size as one another and can therefore be positioned on both lateral sides of the finger that will undergo fixation of the PIP joint.

[0034] In some embodiments, the pair of external fixators in the kit may carry different markings and / or have different colors from each other, which has the advantage that the external fixators can then be distinguished from each other by their different markings and / or colors, which allows the surgeon to quickly and easily identify to colleagues which of the two fixators they are referring to, thereby saving time during the surgical procedure.

[0035] In some embodiments, the kit can further include a plurality of Kirschner wires, where a first one of the Kirschner wires has a diameter that passes through a through-hole in each of the pair of external fixators, and a second one of the Kirschner wires has a diameter that passes through a main slot in each of the pair of external fixators but is restricted from sliding freely along the main slot by the toothed inner surface of the main slot. This has the advantage that the pair of external fixators includes Kirschner wires that are the correct size to be used with the pair of external fixators.

[0036] If the kit does include a plurality of such Kirschner wires, each sharp end of the Kirschner wires in the kit may be provided with a respective cap to protect the sharp end from the person handling the wire, and each such cap may take the form of a soft silicone tube, a rubber bung, or the like.

[0037] Preferably, the main slot has a width that is the same as the diameter of the through-hole in the external fixator, which has the advantage that the first and second Kirschner wires can then also have the same diameter as each other and can therefore be used interchangeably.

[0038] In some embodiments, the kit may further comprise a stop adapted to engage a toothed inner surface of the primary slot in each external fixator of the pair of external fixators, such a stop having the advantage that it can be used to prevent the Kirschner wire from sliding along the primary slot in a direction opposite to the direction in which the Kirschner wire is moved to apply a force to the anatomical element of the joint.

[0039] In some embodiments, when the rigid planar member of each external fixator of the pair of external fixators further comprises an auxiliary slot, the kit may further comprise a third Kirschner wire having a diameter that passes through the auxiliary slot but is restricted from sliding freely along the auxiliary slot by the toothed inner surface of the auxiliary slot. This has the advantage that the pair of external fixators comprises a Kirschner wire that is the correct size for use in the auxiliary slot of the external fixator.

[0040] Preferably, the auxiliary slot has a width equal to the width of the main slot and the diameter of the through-hole in the external fixator, which has the advantage that the third Kirschner wire can then have the same diameter as the first and second Kirschner wires and can therefore be used interchangeably with them.

[0041] When the rigid planar member of each external fixator of the pair further comprises an auxiliary slot, in some embodiments, the kit may further comprise a stop adapted to engage the toothed inner surface of the auxiliary slot in each external fixator of the pair. Such a stop has the advantage that it can be used to prevent the Kirschner wire from sliding along the auxiliary slot in a direction opposite to the direction in which the Kirschner wire is moved to apply force to the anatomical elements of the PIP joint.

[0042] In some embodiments, the stopper can include a cruciform head having arms joined by a circular arc and a body attached to the head, the body having a maximum width equal to the maximum separation between the toothed inner surfaces of the primary and secondary slots. Such a stopper has the advantage that the shape of the head engages the circular cross section of a cylindrical Kirschner wire, while the cylindrical body forms a friction fit with one slot of each of the primary and secondary slots.

[0043] Alternatively or additionally, the stopper may be made of a thermoplastic material, which has the advantage that it can be bonded to the planar member at a desired location by applying heat to the stopper using an instrument such as a diathermy or electrocautery device until the stopper melts.

[0044] In some embodiments, the kit may further comprise a container of adhesive for bonding at least one Kirschner wire to at least one external fixator of the pair of external fixators. The container may be, for example, a pouch or a tube. The adhesive may be, for example, an epoxy resin or polystyrene cement and may be medical grade.

[0045] In some embodiments, the kit may further include a Kirschner wire, pin, or screw having a diameter greater than the width of the primary slot in each of the pair of external fixators. Such a thick-walled Kirschner wire, pin, or screw may be used to lock the position of one or more other Kirschner wires into place by inserting it into the primary slot, because once inserted, the thick-walled Kirschner wire, pin, or screw will not be able to slide in either direction along the primary slot.

[0046] In some embodiments, the thick walled Kirschner wire, pin, or screw may bear different markings and / or have a different color than any other Kirschner wire in the kit, thereby allowing the surgeon to quickly and easily distinguish the thick walled Kirschner wire from the other Kirschner wires.

[0047] In some embodiments, the kit may further comprise a pair of wire benders and / or wire cutters for bending and / or cutting at least one of the Kirschner wires. The wire benders and / or wire cutters may be reusable after appropriate sterilization rather than disposable, so that, for example, only one pair of wire benders and / or wire cutters may be included for every five such kits supplied to the same surgeon or hospital.

[0048] In a third aspect, the present invention also provides a method comprising providing a congruent pair of external fixators as described herein for use in a surgical procedure.

[0049] The method includes inserting a first Kirschner wire having a diameter that passes through a through-hole in each external fixator of the pair of external fixators laterally through the condyle of a first bone proximal to the fracture complex, inserting a second Kirschner wire having a diameter that passes through a main slot in each external fixator of the pair of external fixators but is restricted from sliding freely along the main slot by a toothed inner surface of the main slot laterally through a second bone distal to the fracture complex and parallel to the first Kirschner wire, and Inserting a first external fixator of the congruent pair of external fixators onto a first outer side of the fracture complex over the first and second Kirschner wires by passing a first Kirschner wire through the circular through-hole of one external fixator and a second Kirschner wire through the main slot of the first external fixator; and inserting a first external fixator of the congruent pair of external fixators onto a first outer side of the fracture complex over the first and second Kirschner wires by passing a first Kirschner wire through the circular through-hole of the second external fixator and a second Kirschner wire through the main slot of the second external fixator. applying traction to the fracture complex by inserting a second one of the external fixators over the first and second Kirschner wires onto a second opposing outer side of the fracture complex, and increasing the separation between the first and second Kirschner wires by moving the second Kirschner wire along the main slot of each of the external fixators of the congruent pair in a direction away from the through-hole of each of the external fixators of the congruent pair; The method can further include locking the wires in place on each external fixator of the congruent pair by at least one of inserting a stopper into the main slot on a side of the second Kirschner wire closer to the through-hole than the second Kirschner wire, joining the second Kirschner wire to a rigid planar member, and inserting a pin or screw having a wall thickness greater than the width of the main slot into the main slot on a side of the second Kirschner wire closer to the through-hole than the second Kirschner wire.

[0050] In some embodiments, when the fracture complex comprises subluxated bone fragments and the rigid planar members of each external fixator of the congruent pair of external fixators further comprise auxiliary slots connecting parallel opposing sides of the rigid planar members to one another, the auxiliary slots extending obliquely away from the through holes relative to the main slots of each of the rigid planar members and having toothed inner surfaces, the method includes passing a third Kirschner wire through the auxiliary slot in each external fixator of the pair of external fixators but having a diameter restricted by the toothed inner surface of the auxiliary slot from freely sliding along the auxiliary slot. the third Kirschner wire is inserted laterally through the fractured and subluxated bone fragment parallel to the first and second Kirschner wires; reducing the subluxation of the bone fragment by moving the third Kirschner wire in a direction toward the primary slot of each of the congruent pair of external fixators; and locking the third Kirschner wire into place on each of the congruent pair of external fixators by at least one of inserting a stopper, pin, or screw into the secondary slot on a side of the third Kirschner wire farther from the primary slot than the third Kirschner wire, and bonding the third Kirschner wire to a rigid planar member.

[0051] In some embodiments, when the fracture complex comprises a bone fragment that is impacted distal to the condyle of the first bone, the method further comprises inserting a fourth Kirschner wire having a diameter that passes through a primary slot in each external fixator of the pair but is restricted from sliding freely along the primary slot by a toothed inner surface of the primary slot, laterally through the primary slot in each external fixator of the pair, parallel to the first and second Kirschner wires, between the impacted bone fragment and the second bone, and inserting a fourth Kirschner wire into each external fixator of the pair. The method can further include moving a fourth Kirschner wire along the main slot of each external fixator of the congruent pair in a direction toward the through-hole of each external fixator, and locking the fourth Kirschner wire into a predetermined location on each external fixator of the congruent pair by at least one of inserting a stopper, pin, or screw into the main slot on a side of the fourth Kirschner wire farther from the through-hole than the fourth Kirschner wire, and bonding the fourth Kirschner wire to a rigid planar member.

[0052] In some embodiments, the rigid planar member of at least one external fixator of the congruent pair of external fixators is made of radiolucent material, and at least one external fixator of the congruent pair of external fixators comprises a circular arc of radiopaque material centered on the through-hole of the respective external fixator of the external fixator, and the method may further include aligning the through-hole of at least one external fixator of the congruent pair of external fixators with the center of rotation of the condyle of the first bone by aligning the arc of radiopaque material with a contour of the condyle of the first bone so that both the arc and the contour appear on an x-ray image, and marking on the patient's skin through the through-hole of at least one external fixator of the congruent pair of external fixators with the center of rotation of the condyle of the first bone.

[0053] Further features and advantages of the invention will become apparent from the following detailed description, given by way of example only and in conjunction with the accompanying drawings, in which: [Brief explanation of the drawings]

[0054] [Figure 1] FIG. 1 is a schematic perspective view of a first embodiment of an external fixator. [Figure 2] FIG. 10 is a schematic perspective view of a second embodiment of an external fixator. [Figure 3] FIG. 10 is a schematic perspective view of a third embodiment of an external fixator. [Figure 4] FIG. 10 is a schematic perspective view of a fourth embodiment of an external fixator. [Figure 5] FIG. 10 is a schematic perspective view of a fifth embodiment of an external fixator. [Figure 6] FIG. 10 is a schematic perspective view of a sixth embodiment of an external fixator. [Figure 7] Figure 7A is a schematic top view of one embodiment of a plurality of different embodiments of an external fixator. Figure 7B is a schematic top view of one embodiment of a plurality of different embodiments of an external fixator. Figure 7C is a schematic top view of one embodiment of a plurality of different embodiments of an external fixator. Figure 7D is a schematic top view of one embodiment of a plurality of different embodiments of an external fixator. Figure 7E is a schematic top view of one embodiment of a plurality of different embodiments of an external fixator. Figure 7F is a schematic top view of one embodiment of a plurality of different embodiments of an external fixator. Figure 7G is a schematic top view of one embodiment of a plurality of different embodiments of an external fixator. Figure 7H is a schematic top view of one embodiment of a plurality of different embodiments of an external fixator. [Figure 8] FIG. 10 is a schematic perspective view of a seventh embodiment of an external fixator. [Figure 9] FIG. 13 is a schematic perspective view of an eighth embodiment of an external fixator. [Figure 10] FIG. 1 is a schematic perspective view of a first embodiment of a kit comprising two external fixators. [Figure 11] FIG. 10 is a schematic perspective view of a second embodiment of a kit comprising two external fixators and a number of Kirschner wires. [Figure 12] FIG. 10 is a schematic perspective view of a portion of a third embodiment of a kit comprising two external fixators, a plurality of Kirschner wires, and a stopper. [Figure 13]FIG. 10 is a schematic perspective view of a fourth embodiment of a kit comprising two external fixators and a number of Kirschner wires. [Figure 14] FIG. 10 is a schematic perspective view of a portion of a fifth embodiment of a kit comprising two external fixators, a plurality of Kirschner wires, and a stopper. [Figure 14A] 1 is a schematic top view of an embodiment of a stopper that abuts against a Kirschner wire. FIG. [Figure 15] FIG. 13 is a schematic side elevation view of a ninth embodiment of an external fixator in situ on the PIP joint. [Figure 16] FIG. 16 is a schematic side elevation view of the ninth embodiment of the external fixator shown in FIG. 15 in situ on another PIP joint. [Figure 17A] FIG. 1 is a schematic side elevation view of a fractured PIP joint. [Figure 17B] FIG. 17B is a schematic side elevation view of an embodiment of an external fixator and multiple Kirschner wires applied to the PIP joint shown in FIG. 17A. [Figure 18A] FIG. 1 is a schematic side elevation view of another fractured PIP joint. [Figure 18B] FIG. 18B is a schematic side elevational view of successive stages in the application of one embodiment of an external fixator and multiple Kirschner wires to the PIP joint shown in FIG. 18A. [Figure 18C] FIG. 18C is a schematic side elevational view of successive stages in the application of one embodiment of an external fixator and multiple Kirschner wires to the PIP joint shown in FIG. 18A. [Figure 19A] FIG. 1 is a schematic side elevation view of the PIP joint showing a pilon fracture. [Figure 19B] FIG. 19B is a schematic side elevational view of successive stages in the application of one embodiment of an external fixator and multiple Kirschner wires to the PIP joint shown in FIG. 19A. [Figure 19C] FIG. 19C is a schematic side elevational view of successive stages in the application of one embodiment of an external fixator and multiple Kirschner wires to the PIP joint shown in FIG. 19A. [Figure 19D]FIG. 19D is a schematic side elevational view of successive stages in the application of one embodiment of an external fixator and multiple Kirschner wires to the PIP joint shown in FIG. 19A. [Figure 20] FIG. 19 is a schematic top view of a tenth embodiment of an external fixator. [Figure 21] 1 is a schematic flow diagram of a first embodiment of a method including providing a congruent pair of external fixators as described herein for use in a surgical procedure. [Figure 22] FIG. 2 is a schematic flow diagram of a second embodiment of such a method. [Figure 23] FIG. 10 is a schematic flow diagram of a third embodiment of such a method. DETAILED DESCRIPTION OF THE INVENTION

[0055] FIG. 1 schematically illustrates a first embodiment of an external fixator 1 for joint fixation. The external fixator 1 includes a rigid planar member 2 made of a radiolucent material, i.e., a material transparent to X-rays, allowing for fluoroscopic imaging of the patient through the planar member 2. For example, the planar member 2 may be made of a rigid plastic material manufactured by injection molding. The plastic material may contain an antibacterial additive, such as a silver compound. The planar member 2 has a pair of parallel, opposing side surfaces 4a, 4b, which, in this embodiment, give the external fixator 1 an elliptical shape. The planar member 2 includes a circular through-hole 6 and a linear main slot 10. The through-hole 6 is oriented perpendicular to the parallel, opposing side surfaces 4a, 4b of the planar member 2, and the main slot 10 connects the parallel, opposing side surfaces 4a, 4b. Therefore, a linear rod or wire passing through the through-hole 6 or the main slot 10 will be oriented perpendicular to the parallel, opposing side surfaces 4a, 4b of the planar member 2.

[0056] FIG. 1 also shows a schematic enlargement of the primary slot 10. The primary slot 10 is radially aligned with the through-hole 6. As the enlargement of FIG. 1 shows, the primary slot 10 has a pair of opposing inner surfaces 12, both of which are toothed, wavy, or sawtooth. As such, a straight rod or wire passing through the primary slot 10 is restricted by the pair of toothed inner surfaces 12 of the primary slot 10 from freely sliding along the primary slot 10 in the direction indicated by arrow Y-Y′. The ability of the straight rod or wire to slide along the primary slot 10 will depend on the diameter of the rod or wire relative to the width w of the primary slot 10. If the rod or wire has a diameter that is only slightly smaller than the width w of the primary slot 10, the rod or wire can slide along the primary slot 10 by being pushed hard enough in the direction indicated by arrows Y-Y′ to induce a slight bending of the rigid planar member 2, thereby facilitating the toothed inner surfaces 12 of the primary slot 10 to move slightly apart and allowing the elastic deformation of the planar member 2 to temporarily increase the width w of the primary slot 10 by a small amount. On the other hand, if the rod or wire has a diameter significantly smaller than the width w of the primary slot 10, the ability of the rod or wire to slide along the primary slot 10 will still be impeded by the toothed inner surfaces 12. For example, the primary slot 10 may have a width w of approximately 1.2 mm, designed to accommodate a rod or wire having a diameter of 1.1 mm. Preferably, the width w of the primary slot 10 should be substantially the same as the diameter of the through hole 6 so that rods or wires of the same diameter can pass through both the through hole 6 and the primary slot 10.

[0057] FIG. 2 schematically illustrates a second embodiment of an external fixator 1 for joint fixation. The external fixator 1 of FIG. 2 is identical in all respects to the external fixator shown in FIG. 1 , except that it further includes a semicircular arc 8 of radiopaque material centered about the through-hole 6. Because the semicircular arc 8 is made of a radiopaque material, it will appear on an x-ray image during fluoroscopy of the patient through the rigid planar member 2. For example, the arc 8 may be made of a metal or a metal alloy, such as stainless steel. In this embodiment, the arc 8 is embedded within and enclosed by the planar member 2. While the arc 8 is shown as semicircular in this embodiment, the arc 8 may be any portion of the circumference of a circle, from as small as about 45 degrees to a complete circle, including a full circle. Furthermore, while the semicircular arc 8 in the embodiment of FIG. 2 is shown as continuous, in other possible embodiments it may be discontinuous in a dashed and / or dotted manner. Finally, although in the embodiment of Figure 2, arc 8 is shown as being of finite width, arc 8 may instead be the inner or outer arcuate edge of a more extended piece of radiopaque material, provided that the piece of radiopaque material is not so extensive as to interfere with x-ray imaging of other anatomy of the patient.

[0058] Preferably, when the external fixator 1 is intended for fixation of a fractured PIP joint, the arc 8 should have a radius approximately equal to the average radius of the condyle or head of the proximal phalanx (P1) in an adult human finger. However, this is not strict. For example, an arc 8 with a smaller radius would be more appropriate for fixation of PIP joints in children's fingers. A range of external fixators 1 with arcs 8 of different radii may be conveniently provided for fixation of PIP joints in different patients.

[0059] In the embodiment of FIG. 2 , the arc 8 is positioned and oriented within the external fixator 1 as shown in FIG. 2 . When the external fixator 1 is longitudinally aligned with the middle phalanx P2 of the patient's finger, obstruction of any possible bone fragments of P2 in the case of a pilon fracture by the arc 8 is avoided when taking an x-ray image. On the other hand, when the fixator 1 is rotated counterclockwise around the through-hole 6 through an angle of approximately 100 to 140 degrees out of alignment with P2, the arc 8 is brought into alignment with the contour of the condyle or head of the proximal phalanx P1 in the x-ray image. Therefore, with the fixator 1 in such an orientation, the fixator 1 can be precisely attached through the center of the condyle of P1 by inserting a straight rod or wire through the through-hole 6. Then, by rotating the fixator 1 clockwise through approximately the same angle back into alignment with P2, the fixator 1 can be similarly attached to the middle phalanx P2 by inserting another rod or wire through the primary slot 10 without obstructing the x-ray image of P2 by the arc 8.

[0060] FIG. 3 schematically illustrates a third embodiment of an external fixator 1 for joint fixation. The external fixator 1 of FIG. 3 is identical in all respects to the external fixator 1 of FIG. 2, except that the rigid planar member 2 further includes an auxiliary slot 20 connecting the parallel, opposing sides 4 a, 4 b of the planar member 2. As shown in FIG. 3, the auxiliary slot 20 extends away from the through-hole 6 at an oblique angle relative to the main slot 10. Like the main slot 10, the auxiliary slot 20 has a pair of opposing inner surfaces 22, both of which are toothed, wavy, or serrated, as shown in the enlarged portion of the auxiliary slot 20 also included in FIG. 2. Similar comments apply to the auxiliary slot 20 in relation to a straight rod or wire passing through the auxiliary slot 20, as made above in relation to a straight rod or wire passing through the main slot 10. Preferably, the width z of the auxiliary slot 20 is the same as the width w of the main slot 10, and the toothed inner surface 22 of the auxiliary slot 20 has the same shape and size as the toothed inner surface 12 of the main slot 10. If this is the case, a straight rod or wire of the same diameter as a straight rod or wire passed through the main slot 10 can pass through the auxiliary slot 20 and will behave in the same way as a rod or wire passed through the main slot 10.

[0061] The auxiliary slot 20 can have any convenient shape and length. For example, the auxiliary slot 20 may be curved. However, the auxiliary slot 20 is preferably straight, as in the embodiment shown in FIG. 3.

[0062] Figure 4 schematically shows a fourth embodiment of an external fixator 1 for joint fixation. The external fixator 1 of Figure 4 is identical in all respects to the external fixator 1 of Figure 2, except that it further comprises a plurality of auxiliary slots 20a, 20b, 20c, ..., 20n of the same type as shown and described above in relation to Figure 3. In other words, each of the plurality of auxiliary slots 20a, 20b, 20c, ..., 20n has a respective pair of opposing inner surfaces 22 that are both toothed, wavy, or serrated.

[0063] The plurality of auxiliary slots 20a, 20b, 20c, ..., 20n are arranged parallel to one another. However, the number of auxiliary slots 20a, 20b, 20c, ..., 20n is not fixed, and their spacing need not be constant. There can be any convenient number of auxiliary slots 20a, 20b, 20c, ..., 20n, and the auxiliary slots can have any convenient spacing between adjacent pairs of auxiliary slots. For example, in the embodiment shown in FIG. 4, the plurality of auxiliary slots 20a, 20b, 20c, ..., 20n are four in number and spaced at regular intervals.

[0064] Furthermore, the auxiliary slots 20a, 20b, 20c, ..., 20n do not need to have the same length as each other. In fact, the lengths of the auxiliary slots can be adapted to match the shape of the external fixator 1. However, the widths of the auxiliary slots are preferably the same as each other and as the width of the main slot 10, so that a straight rod or wire of the same diameter can pass through any one of the auxiliary slots 20a, 20b, 20c, ..., 20n and will behave in the same way as if it were passing through another one of the auxiliary slots 20a, 20b, 20c, ..., 20n or the main slot 10.

[0065] Figure 5 shows a schematic diagram of a fifth embodiment of an external fixator 1 for fixation of a joint. The external fixator 1 of Figure 5 is identical in all respects to the external fixator 1 of Figure 4, except that the rigid planar member 2 comprises two plurality of auxiliary slots 20a, 20b, 20c, ..., 20n and 20p, 20q, 20r, ..., 20z shown and described above in relation to Figure 3. Each of the two plurality of auxiliary slots 20a, ..., 20n and 20p, ..., 20z is located on opposite sides of the main slot 10. The two plurality of auxiliary slots 20a, ..., 20n and 20p, ..., 20z are mirror images of each other with respect to the line X-X' on which the main slot 10 lies.

[0066] The external fixator 1 according to the present invention may be of any size. A range of different sizes may be advantageously provided to accommodate a range of differently sized fingers of different patients. For example, a smaller size external fixator 1 may be used for fixation of a child's finger or toe joint than for fixation of the corresponding finger or toe joint of an adult. The planar member 2 of the external fixator 1 according to the present invention may have any shape. In other words, the contour or boundary of the planar member 2 may have any convenient form, so long as the rigid member 2 is flat. The shape of the planar member 2 may be adapted during manufacturing to match the shape of whatever joint the external fixator 1 is intended to be used for ligamentotaxis. Preferably, however, as in the case of the sixth embodiment of the external fixator 1 shown in FIG. 6, the planar member 2 has a shape that is mirror-symmetrical about the longitudinal axis L-L', and the through-holes 6 and the main slots 10 lie on the longitudinal axis L-L'.

[0067] 7A-7H show several different embodiments of the external fixator 1 that conform to this preferred shape. Figures 7A-7H respectively show embodiments of the external fixator 1 in which the shape of the planar member 2 is rectangular, elliptical, oval, leaf-shaped, obovate, spatula-shaped, rhomboid, and delta-shaped. The leaf-shaped and obovate configurations differ only in that the orientation of the outline or boundary of the planar member 2 is inverted relative to the location of the through-holes 6, the arcs of radiopaque material 8, and the primary slots 2 within the planar member 2.

[0068] FIG. 8 schematically illustrates a seventh embodiment of an external fixator 1 for joint fixation. The external fixator 1 of FIG. 8 is identical in all respects to the external fixator 1 of FIG. 2, except that the planar member 2 includes a tail 14 located at the opposite end of the main slot 10 from the through-hole 6. The tail 14 provides a handle to facilitate holding and / or manipulating the external fixator 1 during a surgical procedure. The tail 14 may have a delta-shaped or bifurcated shape and include a flat or concave surface 140 at the opposite end of the planar member 2 from the through-hole 6, as in the eighth embodiment of the external fixator 1 shown in FIG. 9. The surface 140 can be used by the surgeon to press against a Kirschner wire as it moves along the main slot 10 away from the through-hole 6, thereby holding the fixator 1 in place as the Kirschner wire moves relative to the fixator. Furthermore, the tail 14 having such a shape gives the fixator 1 the overall appearance of a fish. This has the advantage that the tail can be used to help speed up identification of certain parts of the fixator 1 during surgery as well as while training surgeons in the use of the fixator.

[0069] FIG. 10 schematically illustrates a first embodiment of a kit 100 including a pair of congruent external fixators 1a, 1b. In other words, the kit 100 includes a pair of external fixators 1a, 1b having the same shape and size. This includes the circular through-holes 6a, 6b, the arcs of radiopaque material 8a, 8b, and the main slots 10a, 10b having the same shape and size as each other, as well as the contours or boundaries of the planar members 2a, 2b having the same shape and size as each other. Each external fixator of the congruent pair of external fixators 1a, 1b can be of any type according to the present invention, including the embodiment of the external fixator 1 already described above in connection with any of FIGS. 1-9. However, in the embodiment shown in FIG. 10, the pair of external fixators 1a, 1b also have different indicia 16a, 16b, which allow the pair of external fixators 1a, 1b to be distinguished from each other. For example, the different markings 16a, 16b may be "L" and "R" to indicate the left and right external fixators of the pair of external fixators 1a, 1b, respectively. Alternatively or additionally, the pair of external fixators 1a, 1b may have different colors. In use, the pair of external fixators 1a, 1b are positioned laterally on the outside of each patient's finger in the same orientation and with one of the parallel, opposing sides 4a, 4b of the first external fixator 1a facing one of the parallel, opposing sides 4a, 4b of the second external fixator 1b. Therefore, the different markings 16a, 16b and / or different colors of the pair of external fixators 1a, 1b can be used by surgeons to quickly and easily identify to colleagues which of the two fixators they are referring to.

[0070] 11 shows a schematic diagram of a second embodiment of a kit 101 including such a pair of congruent external fixators 1a, 1b and two Kirschner wires 31, 32. The first Kirschner wire 31 has a diameter that passes through the through-holes 6a, 6b in each of the pair of external fixators 1a, 1b. The second Kirschner wire 32 has a diameter that passes through the main slots 10a, 10b in each of the pair of external fixators 1a, 1b, but is restricted from sliding freely along the main slots 10a, 10b by the toothed inner surfaces 12a, 12b of the main slots 10a, 10b, in the manner described above in connection with FIG. 1. When the width of the main slots 10a, 10b is the same as the diameter of the through holes 6a, 6b, the diameter of the first Kirschner wire 31 of the Kirschner wires may be the same as the diameter of the second Kirschner wire 32 of the Kirschner wires.

[0071] In use, a patient's finger is placed between a pair of congruent external fixators 1a and 1b. A first Kirschner wire 31 is inserted through the through-hole 6a in the first external fixator 1a, through the head of the proximal phalanx P1 of the patient's finger, and through the through-hole 6b in the second external fixator 1b. A second Kirschner wire 32 is inserted through the main slot 10a in the first external fixator 1a, through the middle phalanx P2 of the patient's finger, and through the main slot 10b in the second external fixator 1b. To apply traction to the PIP joint between P1 and P2, the second Kirschner wire 32 is moved along the main slots 10a and 10b in a direction away from the through-holes 6a and 6b.

[0072] To prevent the second Kirschner wire 32 of the Kirschner wires from sliding back along the main slots 10a, 10b in the direction toward the through-holes 6a, 6b, the kit may further include one or more stoppers 40 adapted to engage with the toothed inner surfaces 12a, 12b of the main slots 10a, 10b, as shown in FIG. 12. FIG. 12 schematically illustrates a portion of a third embodiment of the kit, including such a stopper 40, a pair of congruent external fixators 1a, 1b, and multiple Kirschner wires. The engagement between each stopper 40 and one of the main slots 10a, 10b may be, for example, a friction fit or a click fit. Each stopper 40 may be made of a rigid plastic material manufactured by injection molding, for example. The plastic material may contain an antibacterial additive, such as a silver compound.

[0073] Each stopper 40 may have any convenient shape that engages with the toothed inner surfaces 12a, 12b of the main slots 10a, 10b. For example, the stopper 40 may include a head 45 and a body 46. The head 45 allows the surgeon to manipulate the stopper 40 and insert it into one of the main slots 10a, 10b. The body 46 has a maximum width that fits between adjacent pairs of teeth on the inner surfaces 12a, 12b of the main slots 10a, 10b, but cannot slide along the main slot 10a, 10b from one adjacent pair of teeth to the next adjacent pair of teeth. FIG. 12 shows the stopper 40 inserted into one of the main slots 10a, 10b, abutting the second Kirschner wire 32 of the Kirschner wires, on the side of the Kirschner wire 32 closer to the through-hole 6 than the Kirschner wire 32. Therefore, the stopper 40 prevents the Kirschner wire 32 from sliding along the main slots 10a, 10b in the direction toward the through holes 6a, 6b.

[0074] 13 shows a schematic representation of a fourth embodiment of a kit 102 comprising a pair of congruent external fixators 1a, 1b and three Kirschner wires 31, 32, 33. The pair of external fixators 1a, 1b is identical to the external fixator shown in the embodiment of FIG. 11, except that each external fixator 1a, 1b further comprises a respective auxiliary slot 20a, 20b connecting the parallel, opposing sides of the planar members 2a, 2b to one another, in the manner of the slot 20 of the external fixator 1 shown and described above in relation to FIG. 3. The first Kirschner wire 31 of the Kirschner wires has a diameter that passes through the through-holes 6a, 6b in each of the pair of external fixators 1a, 1b. The second Kirschner wire 32 of the Kirschner wires passes through the primary slots 10a, 10b in each of the pair of external fixators 1a, 1b in the manner described above in connection with Fig. 1, but has a diameter restricted from sliding freely along the primary slots 10a, 10b by the toothed inner surfaces 12a, 12b of the primary slots 10a, 10b. The third Kirschner wire 33 of the Kirschner wires passes through the auxiliary slots 20a, 20b in each of the pair of external fixators 1a, 1b in the manner described above in connection with Fig. 1, but has a diameter restricted from sliding freely along the auxiliary slots 20a, 20b by the toothed inner surfaces 22a, 22b of the auxiliary slots 20a, 20b. When the width of the auxiliary slots 20a, 20b is the same as the width of the main slots 10a, 10b and the diameter of the through holes 6a, 6b, the diameter of the third Kirschner wire 33 may be the same as the diameter of the first and second Kirschner wires 31, 32.

[0075] In use, a patient's finger is placed between the pair of congruent external fixators 1a and 1b, and the first and second Kirschner wires 31 and 32 are inserted as described in connection with FIG. 11 . The third Kirschner wire 33 is inserted through the auxiliary slot 20a in the first external fixator 1a, through, above, or below the middle phalanx P2 of the patient's finger (or through, above, or below the P2 fragment if P2 is fragmented), and through the auxiliary slot 20b in the second external fixator 1b. To reduce the subluxation of the middle phalanx P2 (or the fragment), the third Kirschner wire 33 is moved along the auxiliary slots 20a and 20b in a direction toward the through-holes 6a and 6b.

[0076] To prevent the third Kirschner wire 33 of the Kirschner wires from sliding back along the auxiliary slots 20a, 20b, the kit may further include one or more stoppers 42 adapted to engage with the toothed inner surfaces 22a, 22b of the auxiliary slots 20a, 20b, as shown in FIG. 14. FIG. 14 schematically illustrates a portion of a fifth embodiment of a kit including such a stopper 42, a pair of congruent external fixators 1a, 1b, and multiple Kirschner wires, including the third Kirschner wire 33 of the Kirschner wires. The engagement between each stopper 42 and one of the auxiliary slots 20a, 20b may be, for example, a friction fit or a click fit. Each stopper 42 may be made of a rigid plastic material manufactured by injection molding, for example. The plastic material may contain an antibacterial additive, such as a silver compound.

[0077] Each stopper 42 may have any convenient shape that engages the toothed inner surfaces 22a, 22b of the auxiliary slots 20a, 20b. For example, the stopper 42 may include a head 45 and a body 46 in a manner similar to the stopper 40 described above in connection with FIG. 11. The head 45 of the stopper 42 allows the surgeon to manipulate the stopper 42 and insert it into one of the auxiliary slots 20a, 20b. The body 46 fits between adjacent pairs of teeth on the inner surfaces 22a, 22b of the auxiliary slots 20a, 20b, but has a maximum width such that it cannot slide along the auxiliary slots 20a, 20b from between one adjacent pair of teeth to between the next adjacent pair of teeth.

[0078] The stopper 42 can be inserted into one of the auxiliary slots 20a, 20b on either side of the Kirschner wire 33, depending on which direction along one of the auxiliary slots 20a, 20b the movement of the Kirschner wire 33 should be prevented. Figure 14 shows an example in which the stopper 42 is inserted into one of the auxiliary slots 20a, 20b, abuts against the third Kirschner wire 33 of the Kirschner wires, and is located on the side of the Kirschner wire 33 farther from the through-hole 6 than the Kirschner wire 33. The stopper 42 therefore prevents the Kirschner wire 33 from sliding along the auxiliary slots 20a, 20b in a direction away from the through-holes 6a, 6b.

[0079] Advantageously, the head 45 of either of the stops 40, 42 shown and described in connection with Figures 12 and 14 may have a shape that is complementary to the circular cross-section of the cylindrical Kirschner wire 32, 33. Both stops 40, 42 shown in Figures 12 and 14 have a disk-shaped head 45, which therefore has a circular cross-section, but such cross-section only tangentially engages the cylindrical Kirschner wire. In contrast, Figure 14A schematically shows a top view of an alternative embodiment of the stopper 40, 42, which includes a head 45 having a cross-shaped configuration, the arms of which are connected to each other by circular arcs. Each of these circular arcs has a radius equal to but slightly larger than the radius of the Kirschner wire 32, 33 with which the stopper 40, 42 is designed to be used. Therefore, when the stops 40, 42 of FIG. 14A are placed against the Kirschner wires 32, 33, one of these circular arcs will contact the Kirschner wires 32, 33 in the manner shown in FIG. 14A.

[0080] FIG. 15 shows a schematic diagram of a ninth embodiment of an external fixator 1 in situ on the proximal interphalangeal (PIP) joint. The PIP joint comprises the proximal phalanx P1 and the middle phalanx P2. The PIP joint is formed by the condyle or head H1 of the proximal phalanx P1 and the base B2 of the middle phalanx P2. The external fixator 1 comprises a circular through-hole 6, a semicircular arc 8 of radiopaque material, a main slot 10, a tail 14, and multiple auxiliary slots 20. To secure the external fixator 1 to the PIP joint, the arc 8 is carefully aligned with the contour of the head H1 of the proximal phalanx P1 using X-ray imaging until the through-hole 6 is centered within the head H1. A first Kirschner wire 31 is then inserted through the through-hole 6 and the center of the head H1 of the proximal phalanx P1. A second Kirschner wire 32 is then inserted through the main slot 10 and the middle phalanx P2 at a convenient location. To apply traction to the PIP joint, the second Kirschner wire 32 is moved along the main slot 10 in the direction of arrow D while pressing against the surface 140 of the tail 14 in the direction opposite arrow D, holding the fixator 1 in place as the second Kirschner wire 32 moves relative to the fixator 1. Finally, a stop 40 is inserted into the main slot 10 and abuts the second Kirschner wire 32 on the side of the second Kirschner wire 32 closest to the through-hole 6, preventing the second Kirschner wire 32 from sliding back along the main slot 10 toward the through-hole 6, which would otherwise reduce the applied traction.

[0081] Although FIG. 15 shows only a single external fixator 1, a second congruent external fixator is similarly positioned on the opposite side of the PIP joint from the external fixator 1 shown in FIG. 15. Therefore, the first and second Kirschner wires 31, 32 exit the proximal phalanx P1 and the middle phalanx P2, respectively, and pass through the through-hole 6 and main slot 10 of the second congruent external fixator, respectively. A second stopper 40 is then similarly inserted into the main slot 10 of the second congruent external fixator at a location opposite the location of the stopper 40 shown in FIG. 15 to also prevent the Kirschner wire 32 from sliding along the main slot 10 of the second congruent external fixator.

[0082] FIG. 16 schematically illustrates the external fixator 1 of FIG. 15 in situ on another PIP joint. In this case, the middle phalanx P2 is fractured, resulting in bone fragment BF and dorsal subluxation of the middle phalanx P2. To secure the external fixator 1 to this PIP joint, the same steps as described above in connection with FIG. 15 are first performed. A third Kirschner wire 33 is then inserted through a conveniently located auxiliary slot 20 of the multiple auxiliary slots 20 and through the middle phalanx P2. To reduce the subluxation of the middle phalanx P2, the third Kirschner wire 33 is then moved along a selected auxiliary slot 20 in the direction of arrow A. Finally, a stopper 42 is inserted into the same auxiliary slot 20 and abuts against the third Kirschner wire 33 on the side of the third Kirschner wire 33 that is farthest from the through-hole 6, preventing the third Kirschner wire 33 from sliding along this auxiliary slot 20 away from the through-hole 6, which would otherwise again increase the dorsal subluxation of the middle phalanx P2.

[0083] As in FIG. 15, the second congruent external fixator located on the opposite side of the PIP joint is not shown in FIG. 16. However, as the third Kirschner wire 33 exits the middle phalanx P2, it passes through a corresponding auxiliary slot of the second congruent external fixator. A second stop 42 is then similarly inserted into this auxiliary slot of the second congruent external fixator at a location opposite the location of the stop 42 shown in FIG. 15 to also prevent the third Kirschner wire 33 from sliding along this auxiliary slot of the second congruent external fixator.

[0084] Figure 17A shows a schematic representation of a fractured PIP joint, with the middle phalanx P2 exhibiting multiple fractures, but the bone fragments of the middle phalanx P2 remaining intact. Figure 17B shows a schematic representation of one embodiment of an external fixator 1 and two Kirschner wires 31, 32 secured to the PIP joint of Figure 17A for applying traction to the PIP joint. The external fixator 1 is secured to the PIP joint using the same technique as described above in connection with Figure 15.

[0085] Figure 18A shows a schematic representation of another fractured PIP joint, with the middle phalanx P2 broken, resulting in bone fragment BF and dorsal subluxation of the middle phalanx P2. Figures 18B and 18C show schematic representations of successive stages in the fixation of an external fixator 1 and three Kirschner wires 31, 32, 33, of the same embodiment as shown in Figure 17B, to the PIP joint of Figure 18A to apply traction to the PIP joint and reduce dorsal subluxation of the middle phalanx P2. The external fixator 1 is fixed to the PIP joint using the same technique as described above in connection with Figure 16.

[0086] Figure 18B shows the external fixator 1 after the third Kirschner wire 33 has been inserted through a conveniently located auxiliary slot in the external fixator 1 and through the middle phalanx P2, but before it has been moved along the selected auxiliary slot. Figure 18C shows the external fixator 1 after the third Kirschner wire 33 has been moved along this auxiliary slot in a direction toward the primary slot to reduce the subluxation of the middle phalanx P2, thereby returning it to alignment with the proximal phalanx P1 and into contact with the bone fragment BF. The third Kirschner wire 33 can then be held in place by an appropriately positioned stop inserted into the auxiliary slot in the manner described above in connection with Figure 16.

[0087] FIG. 19A schematically illustrates a PIP joint exhibiting a pilon fracture, in which the middle phalanx P2 is broken, resulting in multiple bone fragments BF. The first of these fragments, BF1, exhibits dorsal subluxation, and the second of these fragments, BF2, exhibits volar subluxation. The third of these fragments, BF3, is distally impacted into the middle phalanx P2. FIGS. 19B-19D schematically illustrate successive stages in the fixation of an external fixator 1 of the same embodiment as shown in FIG. 17B and multiple Kirschner wires to the PIP joint of FIG. 19A to correct this pilon fracture.

[0088] First, in Figure 19B, a first Kirschner wire 31 is inserted through the through-hole in the external fixator 1 and through the condyle or head of the proximal phalanx P1 in the manner described above in connection with Figure 15. A second Kirschner wire 32a is then inserted through the main slot in the external fixator 1 and through the middle phalanx P2, and a third Kirschner wire 33a is inserted through a conveniently located auxiliary slot in the external fixator 1 and through the bone fragment BF1.

[0089] Figure 19C shows the external fixator 1 after the third Kirschner wire 33a has been moved along this auxiliary slot in a direction toward the main slot to reduce the dorsal subluxation of bone fragment BF1. Figure 19C also shows that a fourth Kirschner wire 32b has been inserted through the main slot in the external fixator 1 and between the abutted bone fragment BF3 and the middle phalanx P2. Furthermore, a fifth Kirschner wire 33b has been inserted through another conveniently located auxiliary slot in the external fixator 1 and through bone fragment BF2.

[0090] FIG. 19D shows the external fixator 1 after the fifth Kirschner wire 33b has been moved along this auxiliary slot toward the primary slot to reduce the palmar subluxation of bone fragment BF2. Additionally, the fourth Kirschner wire 32b has been similarly moved along the primary slot toward the through-hole in the external fixator 1, while the second Kirschner wire 32a holds the middle phalanx P2 in place relative to the proximal phalanx P1. This movement of the fourth Kirschner wire 32b pushes bone fragment BF3 toward the head of the proximal phalanx P1, bringing bone fragment BF3 back into alignment with bone fragments BF1 and BF2. All of the Kirschner wires can then be held in place by appropriately positioned stops inserted into the primary and auxiliary slots in the manner described above with reference to FIGS. 15 and 16.

[0091] 19A-19D demonstrate that two or more Kirschner wires can be inserted through any of the primary and auxiliary slots in one embodiment of an external fixator according to the present invention to correct a compound fracture of the PIP joint.

[0092] Figure 20 schematically shows a tenth embodiment of the external fixator 1. The external fixator 1 in Figure 20 has a configuration similar to that shown in Figures 17B, 18B to 18C, and 19B to 19D, but differs from them in several points as follows.

[0093] First, the external fixator 1 of FIG. 20 further comprises a tail 14. The bifurcated tail 14 is disposed symmetrically about the longitudinal axis L-L′ of the planar member 2 of the fixator 1 and comprises a concave surface 140 at the opposite end of the planar member 2 from the through-hole 6. The tail 14 allows for manipulation of the fixator 1 by providing a handle by which the fixator 1 may be held, for example, to apply an instrument such as an arterial clip or tourniquet as described above. The concave surface 140 provides a point of purchase by which a surgeon may apply force to the fixator 1 in the direction shown in FIG. 20 by the arrow labeled D′.

[0094] Second, the external fixator 1 of FIG. 20 differs from the external fixator 1 shown in FIGS. 17B, 18B-18C, and 19B-19D in that, in this case, the arc 8 of radiopaque material centered on the through hole 6 is not embedded within and enclosed by the planar member 2, but instead comprises a stainless steel insert that is fastened to a groove 80 formed in the surface of the planar member 2 for ease of manufacture. The stainless steel insert of the arc 8 is held in place within the groove 80 by a lip 81 that protrudes above the groove 80. Each end of the arc 8 defines a line M-M' that forms an angle θ with the longitudinal axis L-L' of the planar member 2. In this embodiment, the angle θ is approximately equal to 120 degrees.

[0095] Furthermore, to improve the strength and rigidity of the external fixator 1, the planar member 2 is surrounded by a peripheral wall 50 that is thicker than the remainder of the planar member 2. For the same reason, wall 50 similarly extends around the primary slot 10 and around each of the auxiliary slots 20a, 20b, 20c, and 20d. The through-hole 6 is similarly surrounded by a circular wall 60. For example, the planar member 2 may have a thickness of approximately 2-3 mm, while the walls 50, 60 may each have a thickness of approximately 4 mm.

[0096] 20 , the toothed inner surface of the main slot 10 includes a first plurality of teeth 121, each of which tapers in a direction along the main slot 10 and away from the through hole 6. Additionally, the toothed inner surface of each of the auxiliary slots 20a, 20b, 20c, and 20d includes a second respective plurality of teeth 221, each of which tapers in a direction along the respective auxiliary slot 20a, 20b, 20c, and 20d toward the main slot 10. Finally, the toothed inner surface of the main slot 10 further comprises a third plurality of teeth 122, which are located closer to the through hole 6 than the first plurality of teeth 121 and each taper in a direction along the main slot 10 and towards the through hole 6, and thus opposite to the direction in which the first plurality of teeth 121 taper.

[0097] The first plurality of teeth 121 allows the Kirschner wire to be ratcheted in the direction indicated in FIG. 20 by the arrow labeled D, as follows: If the Kirschner wire has a diameter smaller than the widest portion of the teeth 121 but larger than the narrowest portion of the teeth 121, when the wire moves from one tooth of the teeth 121 to the next adjacent tooth, it will induce a slight bending of the rigid planar member 2, thereby facilitating the inner tooth surfaces of the main slot 10 to move slightly away from each other and temporarily increasing the width of the main slot 10 by a small amount through elastic deformation of the planar member 2. Thus, the Kirschner wire can be pushed against a force applied to the concave surface 140 of the tail portion 14, which force is applied in the direction indicated in FIG. 20 by the arrow labeled D′ and opposite to the direction of movement of the Kirschner wire. Such movement of the Kirschner wire is therefore similar to that described above in relation to the Kirschner wire 32a shown in Figures 19B-19D.

[0098] Meanwhile, the third plurality of teeth 122 in the main slot 10 allows the Kirschner wire to be ratcheted in the opposite direction, as shown in FIG. 20 by the arrow labeled D', as follows: Again, if the Kirschner wire has a diameter smaller than the widest portion of the teeth 122 but larger than the narrowest portion of the teeth 122, it will similarly induce a slight bending of the rigid planar element 2 as the wire moves from one tooth of the teeth 122 to the next adjacent tooth. Thus, such a Kirschner wire can be pushed in the direction shown in FIG. 20 by the arrow labeled D' to realign bone fragments of a pilon fracture, such as bone fragment BF3 shown in FIG. 19A. Thus, the movement of the Kirschner wire in this case is similar to that described above in connection with the Kirschner wire 32b shown in FIGS. 19B-19D.

[0099] Finally, the second plurality of teeth 221 formed in each one of the auxiliary slots 20a, 20b, 20c, and 20d, by acting in the same manner as inducing a slight bending of the rigid planar member 2, also allows the Kirschner wire to be ratcheted in a direction toward the main slot 10. Such a Kirschner wire can then be pushed along each of the auxiliary slots 20a, 20b, 20c, and 20d and toward the main slot 10 to realign bone fragments of a pilon fracture, such as bone fragments BF1 and BF2 shown in FIG. 19A. The movement of such a Kirschner wire in this case is therefore similar to that described above in connection with the Kirschner wires 33a and 33b shown in FIGS. 19B-19D.

[0100] Nevertheless, in the case of the first, second and third plurality of teeth 121, 221, 122, it remains possible, by application of sufficient force in the right direction, to push against the dominant direction of the teeth and thus, for example, to release a traction force already applied to the joint or to reposition the Kirschner wire to a different location in the main slot 10 or in one of the auxiliary slots 20a, 20b, 20c and 20d, respectively.

[0101] In general, the external fixator according to the present invention allows a wide variety of different joint fractures to be corrected by using a congruent pair of external fixators according to the present invention to pass Kirschner wires through, over, or under different anatomical components of the joint and then apply forces to these anatomical components in a controlled manner. These forces can be applied by moving the Kirschner wires in either direction along the primary and possibly auxiliary slots of the external fixator. One or more Kirschner wires can be similarly inserted through the same slot and moved in the same or opposite direction to each other, depending on the requirements of the fractured joint undergoing fixation. There is also no limit to the number of Kirschner wires that can be used with the external fixator according to the present invention, up to the maximum number of wires that can be accommodated in the slots of the fixator, which depends on the length of the slot.

[0102] 21 schematically illustrates a first embodiment 200A of a method for using a congruent pair of external fixators in a surgical procedure. The method 200A includes providing 201 a congruent pair of external fixators 1 a, 1 b of the type described above. In this embodiment, the rigid planar members 2 a, 2 b of each of the congruent pair of external fixators 1 a, 1 b are made of a radiolucent material, and each of the congruent pair of external fixators 1 a, 1 b includes a circular arc 8 a, 8 b of radiopaque material centered on the through-hole 6 a, 6 b of one of the external fixators 1 a, 1 b. The through-holes 6a, 6b of each of the congruent pair of external fixators 1a, 1b are aligned with the center of rotation of the condyle of the first bone proximal to the fracture complex by aligning the circular arcs 8a, 8b of radiopaque material with the contour of the condyle of the first bone when both appear together on an x-ray image 202a. The patient's skin is then marked 202b through the through-holes 6a, 6b of each of the congruent pair of external fixators 1a, 1b with the center of rotation of the condyle of the first bone.

[0103] These marks are then used as a guide or target for inserting 203a a first Kirschner wire 31 having a diameter that passes through the through-holes 6a, 6b in each of the paired external fixators 1a, 1b laterally through the condyle of the first bone. 203b A second Kirschner wire 32, 32a having a diameter that passes through the primary slots 10a, 10b in each of the paired external fixators 1a, 1b but is restricted from sliding freely along the primary slots 10a, 10b by the toothed inner surfaces 12a, 12b of the primary slots 10a, 10b is similarly inserted 203b laterally through a second bone distal to the fracture complex and parallel to the first Kirschner wire 31. The first and second Kirschner wires 31, 32, 32a can be inserted in either order.

[0104] Next, the first external fixator 1a of the pair of congruent external fixators is inserted 204a into the first outer side of the fracture complex, covering the first Kirschner wire 31 and the second Kirschner wires 32, 32a, by passing the first Kirschner wire 31 through the circular through-hole 6a of the first external fixator 1a and the second Kirschner wires 32, 32a through the main slot 10a of the first external fixator 1a. The second external fixator 1b of the congruent pair of external fixators is similarly inserted 204b over the first and second Kirschner wires 31, 32, 32a in a similar manner onto a second, opposite, outer side of the fracture complex by passing the first Kirschner wire 31 through the circular through-hole 6b of the second external fixator 1b and the second Kirschner wire 32, 32a through the main slot 10b of the second external fixator 1b. Again, the first and second external fixators of the congruent pair of external fixators 1a, 1b can be inserted in either order over the first and second Kirschner wires 31, 32, 32a.

[0105] A traction force is then applied to the fracture complex by increasing the separation between the first and second Kirschner wires 31, 32a by moving the second Kirschner wire 32, 32a along the primary slots 10a, 10b of each of the congruent external fixators 1a, 1b away from the through-holes 6a, 6b of each of the congruent external fixators 1a, 1b 205. Finally, the second Kirschner wire 32, 32a is locked into place on each of the congruent external fixators 1a, 1b by at least one of the following techniques: inserting a stopper 206a of the type described above into the primary slots 10a, 10b on the side of the second Kirschner wire 32, 32a that is closer to the through-holes 6a, 6b than the second Kirschner wire 32, 32a; The second Kirschner wires 32, 32a are joined to the rigid planar members 2a, 2b by, for example, an adhesive 206b, and a pin or screw having a wall thickness greater than the width of the main slots 10a, 10b is inserted 206c into the main slots 10a, 10b on the side of the second Kirschner wires 32, 32a that is closer to the through holes 6a, 6b than the second Kirschner wires 32, 32a.

[0106] Figure 22 schematically illustrates a second embodiment 200B of a method for using a congruent pair of external fixators in a surgical procedure. Method 200B includes at least the same steps 201, 203a, 203b, 204a, 204b, 205, and at least one of steps 206a, 206b, 206c as described above in connection with Figure 21. In this embodiment, however, the fracture complex includes bone fragments that are subluxated. To address this situation, the rigid planar members 2a, 2b of each of the congruent pairs of external fixators 1a, 1b provided 201 further comprise auxiliary slots 20a, 20b connecting the parallel opposing side surfaces 4a, 4b of the rigid planar members 2a, 2b to one another, the auxiliary slots 20a, 20b extending obliquely away from the through-hole 6 relative to the main slots 10a, 10b of each of the rigid planar members 2a, 2b and having toothed inner surfaces 22a, 22b. The method therefore further includes inserting 213 a third Kirschner wire 33, 33 a, 33 b having a diameter that passes through the auxiliary slot 20 a, 20 b in each of the paired external fixators 1 a, 1 b but whose free sliding along the auxiliary slot 20 a, 20 b is restricted by the toothed inner surfaces 22 a, 22 b of the auxiliary slot 20 a, 20 b. The third Kirschner wire 33, 33 a, 33 b is inserted through the auxiliary slot 20 a, 20 b in each of the paired external fixators 1 a, 1 b and laterally through the subluxated bone fragment, parallel to the first Kirschner wire 31 and the second Kirschner wire 32, 32 a. The subluxation of the bone fragment is then reduced 215 by moving the third Kirschner wire 33, 33 a, 33 b in a direction toward the primary slot 10 a, 10 b of each of the paired external fixators 1 a, 1 b. The third Kirschner wire 33, 33a, 33b is then locked in place on each external fixator of the congruent pair of external fixators 1a, 1b by at least one of the following techniques.Inserting 216a a stopper of the type described above or a pin or screw having a diameter greater than the width of the auxiliary slot 20a, 20b in each external fixator of the pair of external fixators into the auxiliary slot 20a, 20b on the side of the third Kirschner wire 33, 33a, 33b that is farther from the main slot 10a, 10b than the third Kirschner wire 33, 33a, 33b, and bonding 216b the third Kirschner wire 33, 33a, 33b to the rigid planar members 2a, 2b, for example using an adhesive.

[0107] Figure 23 schematically illustrates a third embodiment 200C of a method of using a congruent pair of external fixators in a surgical procedure. Method 200C includes at least the same steps 201, 203a, 203b, 204a, 204b, 205, and at least one of 206a, 206b, and 206c as described above in connection with Figure 21, and may similarly be used in combination with method 200B described above in connection with Figure 22. In this embodiment, however, the fracture complex includes bone fragments that are impacted distal to the condyle of the first bone. To address this situation, the method therefore further comprises inserting 223 a fourth Kirschner wire 32b, having a diameter that passes through the main slot 10a, 10b in each of the pair of external fixators 1a, 1b but whose free sliding along the main slot 10a, 10b is restricted by the toothed inner surfaces 12a, 12b of the main slot 10a, 10b, laterally through the main slot 10a, 10b in each of the pair of external fixators 1a, 1b, between the bone fragment to be impinged and the second bone, parallel to the first Kirschner wire 31 and the second Kirschner wire 32, 32a. The impaction of the bone fragments is then reduced by moving 225 the fourth Kirschner wire 32b along the main slots 10a, 10b of each of the congruent pair of external fixators 1a, 1b in a direction toward the through-holes 6a, 6b of each of the congruent pair of external fixators 1a, 1b. Finally, the fourth Kirschner wire 32b is locked in place on each of the congruent pair of external fixators 1a, 1b by at least one of the following techniques: Inserting 226a a stopper of the type described above or a pin or screw having a diameter greater than the width of the main slot 10a, 10b in each external fixator of the pair of external fixators into the main slot 10a, 10b on the side of the fourth Kirschner wire 32b that is farther from the through-hole 6a, 6b than the fourth Kirschner wire 32b, and joining 226b the fourth Kirschner wire 32b to the rigid planar members 2a, 2b.

[0108] While the present invention has been described above with reference to particular examples and embodiments, the scope of the invention should not be considered limited thereby, but is instead defined by the appended claims. In particular, although the present invention has been described with particular reference to and using the example of fixation of a fractured PIP joint, the external fixator and kit comprising the external fixator according to the present invention are likewise applicable more broadly to the fixation of other fractured joints, such as the DIP joint, and for use in ligamentotaxis, when suitably adapted in terms of shape and size, while still having the same features as defined by the claims.

Claims

1. A kit (100, 101, 102) comprising a pair of congruent external fixators (1, 1a, 1b), said pair of external fixators (1, 1a, 1b) being external fixators (1, 1a, 1b) for fixation of a fractured joint, each of said pair of external fixators (1, 1a, 1b) comprising a rigid planar member (2) having a pair of parallel opposing sides (4a, 4b); The rigid planar member (2) of each of the pair of external fixators (1, 1a, 1b) comprises: Circular through holes (6, 6a, 6b) perpendicular to the parallel opposing side surfaces (4a, 4b); and a linear main slot (10, 10a, 10b) connecting the parallel opposing side surfaces (4a, 4b) to one another; A kit (100, 101, 102), wherein the main slots (10, 10a, 10b) of each of the pair of external fixators (1, 1a, 1b) are radially aligned with the through holes (6, 6a, 6b) and have toothed inner surfaces (12).

2. A kit (100, 101, 102) as described in claim 1, wherein the toothed inner surface (12) of each of the main slots (10) of the pair of external fixators (1, 1a, 1b) has a first plurality of toothed portions (121), each of which tapers in a direction along the main slot (10) and away from the through hole (6).

3. A kit (100, 101, 102) as described in claim 1, wherein the rigid planar member (2) of each of the pair of external fixators (1, 1a, 1b) is made of an X-ray transparent material, and each of the pair of external fixators (1, 1a, 1b) further comprises a circular arc (8) of X-ray opaque material centered on the through hole (6).

4. A kit (100, 101, 102) as described in claim 3, wherein the arc (8) of radiopaque material of each of the pair of external fixators (1, 1a, 1b) is embedded inside the respective rigid planar member (2) of the pair of external fixators (1, 1a, 1b) and is enclosed by the rigid planar member (2).

5. A kit (100, 101, 102) as described in claim 1, wherein each of the rigid planar members (2) of the pair of external fixators (1, 1a, 1b) further comprises an auxiliary slot (20) connecting the parallel opposing side surfaces (4a, 4b) to each other, the auxiliary slot (20) extending obliquely to the main slot (10) away from the through hole (6) and having a toothed inner surface (22).

6. A kit (100, 101, 102) as described in claim 5, wherein the toothed inner surface (22) of each of the auxiliary slots (20) of the pair of external fixators (1, 1a, 1b) has a second plurality of toothed portions (221), and each toothed portion (221) of the second plurality of toothed portions (221) tapers in a direction along the auxiliary slot (20) and toward the main slot (10).

7. A kit (100, 101, 102) as described in claim 5 or 6, wherein the auxiliary slot (20) of each of the pair of external fixators (1, 1a, 1b) is linear.

8. A kit (100, 101, 102) described in any one of claims 5 to 7, wherein each of the rigid planar members (2) of the pair of external fixators (1, 1a, 1b) has a plurality of the auxiliary slots (20a, 20b, 20c, ..., 20n) arranged parallel to each other.

9. A kit (100, 101, 102) as described in claim 8, wherein each of the rigid planar members (2) of the pair of external fixators (1, 1a, 1b) has two plurality of auxiliary slots (20a, 20b, 20c, ..., 20n; 20p, 20q, 20r, ..., 20z), each of the two plurality of auxiliary slots (20a, ..., 20n; 20p, ..., 20z) being arranged on opposite sides of the main slot (10), the two plurality of auxiliary slots (20a, ..., 20n; 20p, ..., 20z) being mirror-symmetrical to each other with respect to a line (X-X'), and the main slot (10) being located on the line (X-X').

10. A kit (100, 101, 102) as described in claim 2, wherein the toothed inner surface (12) of each of the main slots (10) of the pair of external fixators (1, 1a, 1b) has a third plurality of toothed portions (122) located closer to the through hole (6) than the first plurality of toothed portions (121), and each toothed portion (122) of the third plurality of toothed portions (122) tapers in a direction along the main slots (10) of each of the pair of external fixators (1, 1a, 1b) and toward the through hole (6).

11. A kit (100, 101, 102) as described in claim 1, wherein each of the rigid planar members (2) of the pair of external fixators (1, 1a, 1b) has a shape that is mirror-symmetrical with respect to the longitudinal axis (L-L'), and the through hole (6) and the main slot (10) are located on the longitudinal axis (L-L').

12. The rigid planar member (2) of each of the pair of external fixators (1, 1a, 1b) is made of a radiolucent material, and each of the pair of external fixators (1, 1a, 1b) further comprises a circular arc (8) of radiopaque material centered on the through hole (6), 12. The kit (100, 101, 102) according to claim 11, wherein in each of the pair of external fixators (1, 1a, 1b), each end of the arc of radiopaque material (8) defines a line (M-M') that makes an angle (θ) with the longitudinal axis (L-L'), the angle (θ) ranging from 100 degrees to 140 degrees, inclusive.

13. A kit (100, 101, 102) as described in claim 1, wherein each of the rigid planar members (2) of the pair of external fixators (1, 1a, 1b) has a tail (14) located at the opposite end of the main slot (10) from the through hole (6).

14. A kit (100, 101, 102) as described in claim 13, wherein the tail (14) of each of the pair of external fixators (1, 1a, 1b) has a delta-shaped or branched shape and is provided with a flat or concave surface (140) from the through hole (6) to the opposite end of the rigid planar member (2).

15. A kit (100, 101, 102) as described in claim 1, wherein the pair of external fixators (1a, 1b) have different markings (16a, 16b) and / or have different colors from each other.

16. Further comprising a plurality of Kirschner wires (31, 32, 32a, 32b, 33, 33a, 33b), a first Kirschner wire (31) of the Kirschner wires has a diameter that passes through the through-holes (6a, 6b) inside each of the pair of external fixators (1a, 1b); 16. The kit (101, 102) according to any one of claims 1 to 15, wherein the second Kirschner wire (32, 32a, 32b) of the Kirschner wire has a diameter that passes through the main slot (10a, 10b) inside each external fixator of the pair of external fixators (1a, 1b) but is restricted from sliding freely along the main slot (10a, 10b) by a toothed inner surface (12a, 12b) of the main slot (10a, 10b).

17. A kit (101, 102) as described in claim 16, further comprising a stopper (40) adapted to engage with the toothed inner surface (12a, 12b) of the main slot (10a, 10b) inside each external fixator of the pair of external fixators (1a, 1b).

18. Inside each external fixator of the pair of external fixators (1a, 1b), the rigid planar member (2) further comprises auxiliary slots (20, 20a, 20b) connecting the parallel opposing side surfaces (4a, 4b) to one another, the auxiliary slots (20, 20a, 20b) extending obliquely to the main slot (10) away from the through-hole (6) and having toothed inner surfaces (22); 18. The kit (102) according to claim 16 or 17, wherein a third Kirschner wire (33, 33a, 33b) of the plurality of Kirschner wires passes through the auxiliary slot (20a, 20b) inside each external fixator (1a, 1b) of the pair of external fixators (1a, 1b) but has a diameter that is restricted by the toothed inner surfaces (22a, 22b) of the auxiliary slot (20a, 20b) from sliding freely along the auxiliary slot (20a, 20b).

19. A kit (102) as described in claim 18, further comprising a stopper (42) adapted to engage with the toothed inner surface (22a, 22b) of the auxiliary slot (20a, 20b) inside each external fixator of the pair of external fixators (1a, 1b).

20. The stoppers (40, 42) are a cruciform head (45) having arms joined together by a circular arc; a body (46) attached to the head (45), 20. A kit (101, 102) according to claim 17 or 19, wherein the body (46) has a maximum width equal to the maximum separation between the respective toothed inner surfaces (12a, 12b; 22a, 22b) of the main and auxiliary slots (10a, 10b; 20a, 20b).

21. A kit (101, 102) described in any one of claims 17, 19, and 20, wherein the stopper (40) is made of a thermoplastic material.

22. A kit (101, 102) described in any one of claims 16 to 21, further comprising a container of adhesive for joining at least one Kirschner wire of the plurality of Kirschner wires (31, 32, 32a, 32b, 33, 33a, 33b) to at least one external fixator of the pair of external fixators (1a, 1b).

23. A kit (101, 102) described in any one of claims 16 to 22, further comprising a Kirschner wire, pin, or screw having a diameter greater than the width (w) of the main slot (10a, 10b) inside each of the pair of external fixators (1a, 1b).

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