Components of a modular femoral fixation system

Abstract: 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 in said plate, characterized in that said plate (171) includes a relatively flat elongated proximal portion (173) adapted to be secured to the lateral distal femoral shaft and a relatively curved distal portion (175) curved out of the plane of said proximal portion (173) adapted to be secured to the lateral distal femoral condyle, with said distal portion (175) comprising a generally rounded head (177) at 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), with said head (177) and body (179) being connected by a neck (181) having a minimum width substantially smaller than the maximum widths of said head (177) and body (179) so as to leave spaces for the accommodation of a pair of fracture reduction lag screws (195, 197) against said neck (181) on the two sides of said neck (181).

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 bone 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 improper 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 utilized 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 stabilize 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 the 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 the arms and undesirably large bending moments are realized at the points of attachment. As stated above, known elongated implants used to 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 more complicated fracture pattern including also one or more fractures in the metaphyseal and/or diaphysal to be able to select the appropriate length of the side plate depending upon the particular traumatic condition of the patient's femur. However, the surgeon's 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 times are minimized. Such a system is described in European Patent Publication 251583 (Howmedica Inc.). French Patent Application 2405062-A describes a surgical plate for treatment of distal fractures of the femur, having a channel-shaped longitudinal part terminating in 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 portion curved out of the plane of said 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 aperture in the head and a pair of elongated apertures in the body, one 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 EP-251583 and is made of resilient, physiologically inert titanium alloy. In the drawings: Fig. 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 plate 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 and 2. Buttress plate 171 includes a relatively flat elongated proximal portion 173 adapted to be secured to the 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 of 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 the maximum widths of head 177 and body 179. As viewed in transverse cross-sections, the lower surface of the distal buttress plate 171 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 of bone screws 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 screws ( 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 FIG. 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 and two elongated apertures 191 and 193 are provided in body 179, one on each side of body 179. Each of apertures 189, 191 and 193 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 aperture. Furthermore, it is often highly desirable to use a distal buttress plate in conjunction with a pair of fracture 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 the 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. 1 as elements 195 and 197. Finally, the distal buttress plate 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 respectively, in the bone plate 69. Distal buttress plate 171, elongated bone plate 69, a plurality of cortical bone screws such as screw 89 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) are 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 lateral-medial plane and are spaced so that they will lie in close proximity to the two opposite sides of the neck 181 of portion 175 (see FIG. 1). The distal buttress plate 171 is then secured to the lateral femur, with neck 181 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 183. Bone plate 69 is then slid into cavity 199 until its end abuts shoulder 201 and bone screws 89 are screwed to the femur F through apertures 185 and 187. Finally, bone screws 89 are screwed to the femur F through some or all of the four apertures of bone plate 69 remaining outside of the cavity 199. Distal buttress plate 171 can, of course, be implanted without bone plate 69 if the length of the proximal portion 173 is sufficient without extension for a particular surgical situation.

Claims: 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 in said plate, in which said plate (171) includes a relatively flat elongated proximal portion (173) adapted to be secured to the lateral distal femoral shaft and a relatively curved distal portion (175) curved out of the plane of said proximal portion (173) adapted to be secured to the lateral distal femoral condyle, with said distal portion (175) comprising a generally rounded head (177) at 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), characterized by said head (177) and body (179) being connected by a neck (181) having a minimum width substantially smaller than the maximum widths of said head (177) and body (179) so as to leave spaces for the accommodation of a pair of fracture reduction lag screws (195, 197) against said neck (181) on the two sides of said neck (181). 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 of elongated apertures (191, 193) in said body (179), one on each side of the body (179).

Inventors: CHAPMAN MICHAEL WILLIAM, EDWARDS CHARLES CANNON, MEARS DANA CHRISTOPHER, CHAPMAN, MICHAEL WILLIAM, EDWARDS, CHARLES CANNON, MEARS, DANA CHRISTOPHER
Applicants: HOWMEDICA, HOWMEDICA INC.
Application year: 1987
Main classification: A61B17
IPC codes: A61F2, A61B17