Study On Reverse LISS Plating Subtrochanteric Femur Fractures

Part I Biomechanical comparison of LISS and DCS plating subtrochanteric femur fracturesObjective:To compare the biomechanical characteristics of less invasive stabilization system (LISS) and the dynamic condylar screw (DCS) in plating subtrochanteric femur fractures. Method:Twelve cadaveric femurs (35-50 years old) were selected, excluding any lesions. The twelve femur specimens were randomly divided into two groups, one group was fixed by LISS, and the other group was fixed by DCS. To saw off the specimens with a bias cutter 1cm below lesser trochanter, and simulate comminuted fracture models with 2cm gap between both ends. Paste respectively one resistance strain gage at the medial of the specimens and at the point 1cm beside the fracture line. The specimens were fixed at Instron-8874 servo-hydraulic mechanical testing machine. Stress loading experiments was carried out. It was observed that the Load-Strain relationship,Load-Displacement relationship of the femoral head and the axial stiffness of the femoral head in the two fracture models. Non-destructive cyclic loading experiment was then carried out. Set the peak valley value of load 0-150N, loading frequency 1Hz, period of batching cycle 2000 times. Did accuracy analysis and error processing to all the biomechanics indexs getted from the experiment by Chauvent Criterion, P<0.05 showed statistically significant differences. Results:In the experiment of Axial compression, on Load-Strain relationship conclusions, the strain of LISS internal fixation group in strain gauge 1 and strain gauge 2 was all smaller than the DCS group; The results of Load-Displacement relationship was that, femur vertical displacement of LISS group and DCS group were 2.87±0.84mm and 9.12±0.74mm in 600N respectively; when the load was 600N, the axial stiffness of LISS internal fixation group was 209.06±18.63 N/mm, while the DCS group was 65.79±7.26 N/mm. In the experiment of dynamic fatigue, under the same situation of cyclic loading cycle, the subsidence displacement of femoral head in LISS internal fixation group was smaller than DCS group; The force LISS fixation group to bear was 130.83±11.67 N when max subsidence displacement of the femoral head was 0.5mm, while the DCS group was 80.76±7.35N under the same situation; When the subsidence displacement was 0.5mm, LISS internal fixation group had been 1231±30 times of the cyclic loading cycle already, while the DCS group was the 379±18 times. According to the statistical analysis, all the differences were statistical significance (P<0.01). Conclusions:In the two fixation groups of subtrochanteric fracture, reverse LISS internal fixation group was much firmer than DCS group, and the ability of LISS against to the axial deformation was better than DCS internal fixation device.Part II Reverse LISS plating subtrochanteric femur fracturesObjective:To explore the technique and results of reverse LISS plating for subtrochanteric femur fractures. Methods:From October 2007 to May 2009,31 cases of fresh subtrochanteric femur fractures were treated with reverse LISS. There were 23 males and 8 females, with an average age of 48.6 years (range 27 to 83 years). Twelve injuries were the result of a traffic accident; six, a fall from a greater height; four, a crush of heavy object; nine, a fall from a standing height. According to Seinsheimer classification, four fractures were type IIC, twelve type IIIA, six IIIB, six type IV and three type V. Subtrochanteric fracture was reduced indirectly with patient on a fracture table. The reverse LISS plate was inserted through a lateral incision of the greater trochanter between the lateral vastus muscle and the periosteum. Four to five screws were inserted through stab incisions into the proximal and distal fragments, respectively. Results:Operative time average 50 (range,35～80) minutes and estimated blood loss averaged 90 (range,60～150) ml.31 patients were available for evaluation with an average follow-up of 15.6 months. All fractures healed at a mean of 18.2 weeks (range 13 to 32 weeks). There were no cases of failed fixation, or deep infection. Average range of motion of the hip joint was recorded as follows: flexion 115°,external rotation 35°, internal rotation 15°, adduction 15°, and abduction 36°. According to the modified Harris hip score, scores ranged from 82 to 100 (average,92.6), and there were 24 excellent and 7 good. Conclusions:Reverse LISS plating yield good results in subtrochanteric femur fractures, with stable fixation and minimal invasive procedure.