IE66760B1 - Components of a modular femoral fixation system - Google Patents

Description

Internal fixation of femoral fractures is one of the most common orthopedic surgical procedures. Many different types of femoral fractures are encountered in practice, including fractures in the femoral neck, intertrochanteric, mid-shaft and distal condylar regions. The femoral hone will sometimes fracture cleanly into two large fragments along a well-defined fracture line, and on other occasions fracture into many smaller fragments. Often, more than one type of fracture will exist concurrently in different regions of the femur of an injured patient.

A wide variety of implants have been developed over the years for use in the internal fixation of femoral fractures. Although numerous excellent design achievements have been realized, several general problem areas remain. First, almost all of the currently available implants have a highly specialized application limited to only one specific anatomical location in the femur. Thus, a hospital must maintain at great expense a very large and variegated inventory of different implants to handle all expected contingencies- These implants are generally not compatible, i.e. they cannot be interconnected together in case of a complicated fracture pattern extending into different anatomical regions of the femur.

Second, each implant has its own peculiar attributes and deficiencies, and the use of many of the known Implants involves the use of a surgical technique that is unique to that implant and sometimes complicated and difficult as well. Consequently, the opportunities for -2improper implant selection and surgeon error during implantation are inevitably increased. Finally, tissue reactions with implants made of stainless steel and certain other surgical implant alloys tend to reduce the useful lifetime of the implants and require premature removal from the patient's body.

One very commonly utilised femoral internal fixation device is an elongated implant (nail, screw, pin, etc.) adapted to be positioned along the longitudinal axis of the femoral neck with its leading end portion in the femoral head so as to stabilise a fracture of the femoral neck. The elongated Implant may be implanted by itself or connected to another implant such as a side plate or intramedullary rod.

The leading end portion of the implant typically includes means to positively grip the femoral head bone (external threads, expanding arms, etc.), but the inclusion of such gripping means can introduce several significant problems. First, implants with sharp edges on the leading end portion, such as the externally threaded Implants, exhibit a tendency to migrate proximally towards th® hip joint bearing surface after implantation. Such proximal migration under physiological loading, which Is also referred to as femoral head cut-out, can lead to significant damage to the adjacent hip joint. Also, the externally threaded implants can generate large stress concentrations in the vicinal bone during implantation which can lead to stripping of the threads formed in the bone and thus obviously a weakened grip. The movable arms of known expanding arm devices are usually free at one end and attached at the other end to the main body of the leading end portion of the Implant. As a result, all fatigue loading is concentrated at the attached ends of -3the arms and undesirably large bending moments are realized at the points of attachment, As stated above, known elongated implants used fo stablize fractures of the femoral neck are often connected in use to a side plate which in turn is secured to the outer cortical wall of the adjacent femoral shaft, for example with bone screws» This type of assembly is often selected when a femoral neck fracture is a part of a moxe complicated fracture pattern including also one or more fractures in the metaphyseal and/or diaphysal to be able fo select the appropriate length of the side plate depending upon the particular traumatic condition of the patient's femur. However, the surgeone& flexibility in this regard typically requires the hospital to maintain a costly inventory of implants.

The present invention relates to components for a modular system of femoral internal implants, and instrumentation therefor, that can be employed to treat a number of different fracture patterns and other disorders with a minimal number of interconnectable system components involving simple uncomplicated operational procedures in which surgical invasiveness and operation tiww are minimized. Such a syst®.» ia described in European Patent Publication 251583 (Howaedica Inc-).

French Patent Application 2405062-A describes a surgical elate for treatment of distal fractures of the femur, having a channel-shaped longitudinal part terminating ia a widened plate to fit the external shape of the lower end.of the femur.

According to the invention, there is provided a distal buttress plate adapted to be secured to the outer cortical wall of the lateral distal femur by means of bone fasteners received in apertures in said plate, in . which said plate includes a relatively flat elongated proximal portion adapted to be secured to the lateral distal femoral shaft and a relatively curved distal -4— portion curved out of the plane of ©aid proximal portion adapted to be secured to the lateral distal femoral condyle, with said distal portion comprising a generally rounded head at the distal end of the plate and a generally widened body having a greater maximum width than both said head and said proximal portion, characterized by said head and body being connected by a neck having a minimum width substantially smaller than . the maximum widths of said head and body so as to leave spaces for the accommodation of a pair of fracture reduction lag screws against said neck on the two sides of said neck» Preferably the plate has at least one elongated I apertute in the head and a pair of elongated apertures in th© body, on© on each side of the body» A distal buttress plate according to the invention will now be described by way of example with reference to the accompanying drawings. The plate Is to be used in the kit described in BP«251S83 and is made of resilient, physiologically inert titanium alloy» In the drawings; Pig. 1 is a top plan, view of a distal buttress plate included in a modular implant system, Fig» 2 Is a side elevational view of the plate of Fig» 1, Fig. 3 is an elevational view of the plate of Fig» 1, an elongated bone plat® and a plurality of cortical and cancellous bone screws secured to a patient's distal femur.

A distal buttress plate 171 of the invention adapted to be secured to the outer cortical wall of the lateral distal femur is shown In FIGS» 1 aad 2. Buttress plat® 171 include© a relatively flat elongated proximal portion -5173 adapted to be secured to th® lateral distal femoral shaft and a three dimensionally-contoured distal portion 175 designed to replicate the mean geometry of the lateral femoral condyle of adult -humans- The distal portion 175 includes a generally rounded head 177 at the distal end ©£ plate 171, a generally widened body 179 having a greater maximum width than both head 177 and proximal portion 173, and a neck 181 having a minimum width W substantially smaller than th® maximum widths of head 177 and body 179. As viewed in transverse crosssections, the lower surface of the distal buttress plate 17X is contoured along its entire length to conform to the outer cortical wall of the distal femur.

Distal buttress plate 171 is adapted to be secured to the' outer cortical wall of .the lateral distal femur by means cf bone screes received in apertures in the plate. Thus,, three circular through apertures 183, 185 and 187 are provided in proximal portion 173 for the receipt of three bone screes (e.g- cortical screw 89), one in each aperture- These three apertures are staggered with respect to the longitudinal axis of proximal portion 173 (see PIG. 1), and are Identical respectively to apertures 55, 57 and 59 in the angled side plate 43 described in EP 251583. Also, an elongated aperture 189 is provided in head 177 aad two elongated apertures 191 and 193 are provided in body 179,, one on each side of body 179. Bach of apertures 189, 191 and 1S3 is substantially identical to the apertures in the elongated bone plate 69 and thus are each configured to receive two (or one, if only one is desired) bone screws and permit the universal angulation of said screws when fully advanced in the aperturePurthexmore, it is often highly desirable to use a distal buttress plate in conjunction with a pair of -6fracture reduction lag screws extending across the distal condylar region of the femur., Such lag screws are screwed fully into the bone before the distal buttress plate is implanted and thus cannot practically be passed through th® plate, An important feature of distal buttress plate 171 is that the distal portion 175 thereof is configured in such a manner that spaces outside the periphery of plate 171 are left against neck 181 for the accommodation of two fracture reduction lag screws, extending across the distal condylar region of the femur, on the two sides of neck 181, These two lag screws are shown in phantom in FIG- I as elements X95 and 197» Finally, the distal buttress plat® 171 is also provided with an elongated cavity 199 formed in the lower surface of the proximal portion 173» Cavity 199 is identical to, and is adapted to serve in the same bone plate-‘dovetail interlocking capacity as, cavity 63 in the angled side plate 43 and cavity 167 in the angled side plate 149. When the end of bone plate 69 inserted into cavity 199 abuts the shoulder 201 of the cavity, apertures 185 and 187 overlie the two terminal -apertures., e.g. apertures 79 and 85 respectivelyLf in the bone plate 69» Distal buttress plate 171, elongated bone plate 69, a plurality of cortical bone screws such as screw ©9 and a plurality of cancellous bone screws such as screw 101 can be connected together and secured to a patient's femur F in the manner shown in FIG. 3» First, two lag screws (not shown in FIG. 3) ar® fully implanted in the distal condylar region, if desired, to reduce a fracture -in said region. These implanted lag screws are positioned so that they lie generally in the lateralmedial plane and are spaced so that they will lie in close proximity to the two opposite sides of the neck 181 -7of portion 175 (see FIG. 1). The distal buttress plate 171 is then secured to the lateral femur, with neck 1S1 fitting between the two previously implanted fracture reduction lag screws, by means of bone screws 101 passing through apertures 189, 191 and 193 (one or two screws can be passed through each of apertures 189, 191 and 193, as desired) and a bone screw 89 passed through aperture 133. Bone plate 69 is then slid into cavity 199 until its end abuts shoulder 201 and bone screws 39 are screwed to the femur F through apertures 185 and 187. Finally, bone screws 89 are screwed to the femur 3? through some or all of the four apertures of bone plate 69 remaining outside of th® cavity 199. Distal buttress plate 171 can, of course, be implanted without bone plate 69 if the length I ox the' proximal portion 173 is sufficient without extension for a particular surgical situation.

Claims (3)

1. X» A distal buttress plate (171) adapted to be secured to the outer cortical wall of the lateral distal femur by means of bone fasteners received in apertures ia said plate, in which said plate (17X) includes a relatively flat elongated proximal portion (173) adapted to be secured to the lateral distal femoral shaft and a relatively curved distal portion (3.75) curved out of the plane of said proximal portion (173) adapted to foe secured to the lateral distal femoral condyle, with said distal portion (175) comprising a generally rounded head (177) af the distal end of the plate (171) and a generally widened body (179) having a greater maximum width than both said head (177) and said proximal portion (173 J,, characterised fey said head (177) and foody (179) being connected by a neck (181) having a minimum width substantially smaller than the maximum widths of said head (177) and foody (179) so as to leave spaces for the accommodation of a pair of fracture reduction lag screws (195, 137) against said neck (181) oa the two sides of said neck (181).

2. A distal buttress plate of claim 1 further characterized in that said distal buttress plate (171) is provided with at least one elongated aperture (189) in said-head (177) and a pair a>£ elongated apertures (191, 1931 in said foody (179), one oa each side os the foody (179).

3. A distal buttress plate substantially as hereinbefore described with particular reference to the accompanying drawings.