Dynamic fixation of unstable trochanteric hip fractures. A clinical and radiographic evaluation of the Medoff sliding plate

Abstract: In stabilising extracapsular hip fractures, the Medoff sliding plate (MSP) differs from other screw-plates by its compression capacity along the femoral shaft (uniaxial dynamization). Additional compression along the neck of femur can be achieved by primary release of the lag screw (biaxial dynamization). 244 consecutive inter- and subtrochanteric fractures in 243 elderly patients were fixed with the MSP, and prospectively followed for a minimum of one year. 104 unstable intertrochanteric fractures were uniaxially dynamized and 108 similar fractures were biaxially dynamized. Postoperative weight-bearing was permitted in 95 % of the patients. At 1 year, there was a significant difference (p=0.03) in the fixation failure (7 vs 1) between the dynamization groups. 32 subtrochanteric fractures were also dynamized with the MSP, 17 uniaxially and 15 biaxially. In the uniaxial group staged biaxial dynamization, i.e. initial plate slide later followed by secondary release of the lag screw, was done in 3 fractures with a complete plate slide, and which successfully stopped further lag screw migration. The one failure was a nonunion in a biaxially dynamized fracture. We developed a practical method for establishing the real degree of sliding in screw-plate devices from standard a.p. radiographs, independently of the position of the hip. By analysis of the radiographs, we found that an unstable fracture configuration of the greater trochanter increased the degree of femoral medialisation and fracture compression in biaxially dynamized intertrochanteric fractures. We also performed a randomised multicenter trial in 107 elderly patients, in order to compare the efficacy of the load sharing concept of the MSP (n=55) with that of three more load bearing screw-plate devices (n=52) in fixation of subtrochanteric fractures. Significantly (p=0.04) more patients in the MSP group (78 % vs 60 %) were allowed immediate postoperative weight-bearing. Significantly (p=0.01) fewer failures (1 vs 8) were found in the MSP group than in the other group. We think that it is possible to reduce the rate of fixation failure by using the right dynamization mode of the MSP. We recommend uniaxial dynamization in the subtrochanteric fracture, staged biaxial dynamization in the combined inter/subtrochanteric fracture with a complete plate slide, and biaxial dynamization in the unstable intertrochanteric fracture.