SURGICAL FIXATION SYSTEM
This invention relates to a surgical fixation system for securing a part such as a bone fragment or a ligament to a bone.
In the reduction and fixation of fractures in the hand, the surgeon is frequently faced with the difficult task of securing a small fragment of bone without devitalising or shattering it during fixation. When a bone fracture fragment involves a joint, accurate and secure fixation is essential. In one known method, the bone fracture fragment is secured to the bone from whence it came using a screw. However, even the smallest screw available to the surgeon is often too large for use without further cracking of the bone fragment. It is also known to secure a bone fragment in place by drilling two holes through the bone fragment and the bone and securing the bone fragments using a loop of wire passed through the holes and tightened by twisting the ends of the wire together. However, as the wire loop is tightened, there is a risk of the wire cutting through the fragment. Generally, these fractures require a high degree of skill and ingenuity to repair and poor results are not infrequent, particularly in relatively inexperienced hands.
It is an object of the present invention to obviate or mitigate the above disadvantages of existing fixation systems.
According to one aspect of the present invention, there is provided a surgical fixation system for securing a part to a bone, said system comprising a pair of biocompatible load-spreading members and a length of biocompatible flexible filamentary material, the load-spreading members being adapted to be disposed against said part and said bone respectively at opposite ends of a hole formed through said part and said bone, and the length of flexible filamentary material, in use, being engaged with said members and passing through said hole and being tensioned to secure the part to the bone, with the opposite end regions of the members being urged against the part and the bone respectively by virtue of tensioning of the looped flexible filamentary material.
According to a second aspect of the present invention, there is provided a method of securing a part to a bone using a surgical fixation system as defined in the last preceding paragraph, said method comprising the steps of (a) forming a hole through said part and said bone; (b) introducing said length of biocompatible flexible filamentary material into said hole such that said filamentary material extends beyond the bone on one side and the part to be secured on the other; (c) engaging one load-spreading member against the bone and another against the part to be secured; and (d) tensioning the filamentary material whilst the load-spreading members are engaged whereby to urge the load-spreading members against said part and the bone, respectively.
In one method, the filamentary material is inserted into one end of the hole such that a loop of said filamentary material projects from an opposite end of the hole and the ends of said filamentary material project from said one end, one of the load-spreading members is introduced into the loop, and the other of the load-spreading members is introduced between said ends of said filamentary material before the tensioning step is effected.
In another method, said filamentary material is introduced into one end of the hole with one of the load-spreading members already attached so that ends of the filamentary material project from an opposite end of the hole, and the other of the load-spreading members is introduced between said ends of said filamentary material before the tensioning step is effected.
Said part to be secured to the bone may be a bone fragment which has fractured from the bone, or it may be a piece of soft tissue, e.g. a ligament (autologous, donated or prosthetic) which is to be secured to the bone in a ligament repair procedure.
In a preferred embodiment, at least one of the load-spreading members has a waist region and a pair of opposite end regions. Such a waist region can not only assist in correct positioning of the filamentary material on the load-spreading member, but it can also enable the plate to flex in use so that it can be closely adjacent the surface against which it engages. Such an arrangement may be defined by an appropriately shaped plate or a cruciform-shaped element.
As an alternative, at least one of the load-spreading elements may take the form of a plate having a pair of holes therethrough to receive the filamentary material.
Each of the above-described types of load-spreading members may be used in combination with any other.
Most conveniently, the load-spreading members and the flexible filamentary material are formed of the same biocompatible metal to avoid the risk of electrolytic action causing bone resorption. The flexible filamentary material will normally be formed of a biocompatible wire, although it is within the scope of the present invention to use a suture material.
The present invention reduces the risk of damage to bone fragments being fixed and avoids the need to provide more than one hole through the bone and part to be secured thereto. However, it is within the scope of the present invention for more than one hole to be provided for the repair of long splinters, in which case it is convenient to use elongated load-spreading members which may have more than one waist region or other anchoring formation to permit anchoring more than one length of filamentary material.
In the above description, reference is made to the use of a pair of biocompatible load-spreading members which are adapted to be disposed against said part and said bone, respectively. However, it is also within the scope of the present invention to employ more than two load-spreading members for a repair procedure. Thus, for example, it is possible to use an elongated load-spreading member having more than one waist region or other anchoring formation in conjunction with two or more appropriately located other load-spreading members, with filamentary material extending between the elongated load-spreading member and the other load-spreading members. Alternatively, in a modification of the above-described arrangement, repair may be effected using only a single load-spreading member provided that the filamentary material can be suitably tensioned. For example, in the case of a tendon repair, one load-spreading member can be used at a far end of a hole drilled through the bore and the attachment to the tendon itself at the rear end of the hole could be effected by suturing without the use of another load-spreading member. Embodiments of the present invention will be described, by way of example, with reference to the accompanying drawings, in which:- Figs 1 to 4 are perspective views showing various stages in a bone fragment fixation procedure using one embodiment of a surgical fixation system according to the present invention, and Figs 5 to 10 are illustrations of different load-spreading members that may be used in such a fixation procedure.
In the various illustrated embodiments, similar parts are accorded the same reference numerals.
In Figs 1 to 4, the surgical fixation system comprises a pair of identical, butterfly (or figure-of-eight) shaped, load-spreading plates 10 (see Fig 3) formed of biocompatible stainless steel, and a length of wire 12 also formed of biocompatible stainless steel. Thus, each load-spreading plate 10 comprises a pair of relatively large area opposite end regions 10a integrally united by an intermediate waist region 10b.
In Figs 1 to 4, the surgical fixation system is shown in use for securing a bone fragment 14 to a damaged phalangeal bone 16 from which the fragment 14 has become detached. . A single hole 18 is drilled through the bone fragment 14 and the bone 16 after the surgeon has ensured that the bone fragment 14 is located in the correct position against the bone 16, although this is not actually shown in Fig 1.
Then, a loop of the wire 12 is passed through the hole 18 so that the looped end 12a of the wire 12 projects from one end of the hole 18 whilst the free ends 12b of the wire 12 project from the other end of the hole 18. (Fig 2). One of the load-spreading plates 10 is then introduced into the looped end 12a of the wire 12 which is then withdrawn through the hole 18 until the plate 10 is drawn into abutment with the bone fragment 14. The surgeon ensures that the wire 12 is engaged snugly in the waist 10b and that the opposite end regions 10a of the plate 10 abut against the surface of the bone fragment 16 on opposite sides of the hole 18 therethrough. The other load-spreading plate 10 is then introduced between the free ends 12b of the wire 12 at the opposite end of the hole 18 so that such plate 10 abuts against the bone 16. The free ends 12b of the wire 12 are then twisted together by the surgeon in order to tension the wire 10 and thereby cause the bone fragment 16 to be secured to the bone 18 with the opposite end regions 10a of the plates 10 acting to spread the load and thereby reduce the risk of damage to the parts 14 and 16 being secured together.
In Fig 5, load-spreading plate 10 has a plurality of integral spikes 20 extending from each end region 10a, essentially perpendicularly from the plane of plate 10, in order to provide additional anchorage of the plate to the bone and to prevent twisting of the plate 10 when the wire 12 is twisted. If the plate 10 is to be used for soft-tissue repair, rather longer spikes 20 may be employed.
In Fig 6, a cruciform load-spreading plate 10 is provided with spikes 20.
In Fig 7, load-spreading plate 10 has a multiplicity of (three in this embodiment) waist regions 10b interlinking end regions 10a and intermediate regions 10c. In this embodiment, spikes 20 are provided at each region 10a, 10c. This design is useful for the fixation of long or multiple fragments when multiple, individually orientated wires 12 are required. (Fig 8)
In Fig 9, the load-spreading plate 10 has no waist region 10b but is pre- attached to the wire 12 by for example crimping or welding. However, it is possible to include a waist region to facilitate contouring of the plate 10 so that it is a close fit against the bone.
In Fig 10, load-spreading plate 10 is provided with two through-holes for securement of wire loop 12a. The plate may be oval (as shown) or it may be circular and may have added wings to increase the load- spreading area.
The load-spreading plates 10 may be used in pairs of the same type or pairs of different plates may be used, dependent upon the exact nature of the fracture to be repaired. It is also within the scope of the present invention for only one of such plates to be used, provided of course that this is acceptable for the type of repair being performed.