Alternative techniques in trochanteric hip fracture surgery. Clinical and biomechanical studies on the Medoff sliding plate and the Twin hook

Detta är en avhandling från Department of Orthopedics, Helsingborg Hospital, S-251 87 Helsingborg, Sweden

Sammanfattning: In allowing compression along the femoral shaft (uniaxial dynamization) and optional compression along the femoral neck (biaxial dynamization), the Medoff sliding plate (MSP) represents a new principle in the fixation of trochanteric hip fractures. The Twin hook with 2 apical hooks was designed as an alternative to the lag screw. In 3 prospective consecutive case series and 1 prospective randomized study together comprising 342 trochanteric fractures, these alternative techniques were investigated. 3 postoperative fixation failures occurred in the unstable intertrochanteric fractures treated with biaxial dynamization with the MSP (n=194), and 5 in those treated with the sliding hip screw (n=62) (p=0.04). A mean femoral shortening of 15 mm with the MSP and 11 mm with the sliding hip screw was found (p=0.03). More medialization of the femoral shaft occurred with the sliding hip screw (26%) than with the MSP (12%) in patients with marked femoral shortening (p=0.03). 3 postoperative fixation failures occurred in subtrochanteric fractures treated with uniaxial dynamization (n=29) and 2 in those treated with biaxial dynamization (n=19). Medialization of the femoral shaft occurred in 9 of the 19 biaxially dynamized fractures. The Twin hook was used in 50 patients and appeared to provide similar fixation stability as the lag screw. Biomechanical tests confirmed improved stress transmission over the fracture area with the MSP compared to the sliding hip screw in intertrochanteric fractures, and similar fixation stability with the MSP and the Intramedullary Hip Screw in subtrochanteric fractures. In axial and torsional loading, the Twin hook demonstrated gradually increasing resistance to migration. With the lag screw, the peak load was higher, but after migration with failure of the support by the threads, the loads were similar. Biaxial dynamization with the MSP appears to control fracture impaction effectively and minimizes the rate of postoperative fixation failure in intertrochanteric fractures. In subtrochanteric fractures, uniaxial dynamization prevents medialization of the femoral shaft and is therefore preferred to biaxial dynamization. The Twin hook appears to provide adequate fixation stability, and with potential for simplified intraoperative handling and reduced dissection, the Twin hook may pose advantages compared to the lag screw.

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