| Intertrochanteric fracture is quite common in hip injuries which usually happen to old people. It is not only relative to the osteoporosis, but also the strength reducing and fragility increasing of the bone. With the high speed dynamic injuries (such as falling injuries, traffic accidents) increased in the recent years, the numbers of middle-aged and young patients have significantly increased. This kind of patients always suffer comminuted and instable fractures that caused by high energy violence. The death rate has greatly decreased with the progress of various internal fixation operations and the improvement of diagnosis and treatment in perioperative complications, but the complications such as coxa vara, steel plate failure, femoral head and neck cutting, shortening of the lower limbs still exist. The proximal femur is a truss structure. It is the most important part to resistance and turned against elastic buckling in biomechanics. Some biomechanics experiments turn out that the coloboma and extensive coloboma of the lesser trochanteric would lead to the proximal femur stress concentration which could weaken the performance of resisting the external load and the resistance against the torque. The lesser trochanteric coloboma and the medialis cortex of the proximal femur coloboma are important reasons lead to complications such as coxa vara, steel plate failure, femoral head and neck cutting, shortening of the lower limbs.In order to prevent or reduce the complications, more and more attention is paid to the importance of restoring the continuity of the lesser trochanteric and the medialis cortex of the proximal femur. However, difficulties are showed to restore and fix the continuity of the lesser trochanteric because it is located inside the rear and towed by the iliopsoas. If we fix it with bare hands, it would definitely prolong the time of the operation and increase the damage of the soft tissue around the lesser trochanteric which would ruin the blood supply and increase bleeding. Nowadays, lag screws are used to fix the lesser trochanteric in the clinical in China. This method has no specific reduction fixation system and it is still in exploration.ObjectiveFinite element analysis is undertaken to research the biomechanics influence of posteriomedial fractures to the intertrochanteric fractures which is fixed by dynamical hip screw. According to the results of finite element analysis, we are trying to design and produce the lesser trochanteric reduction fixation system.Method1Finite element analysis of the intertrochanteric fractures fixed by dynamical hip screw (DHS).Intertrochanteric fractures models involved to lesser trochanteric and medialis cortex of the proximal femur are established on the base of three dimensional finite element analysis of intact and osteotomied proximal femurs through computerized tomographic (CT) data. We fix the models by dynamical hip screw (DHS) and analyze them by finite element analysis.2The design of the lesser trochanteric reduction fixation system.According to anatomical features of the lesser trochanteric and biomechanics characteristics of the proximal femur, we design and draw up the three-views-drawing of the lesser trochanteric reduction fixation system. We produce a stainless steel lesser trochanteric reduction fixation system according to the three-views-drawing.3The clinical trials of the lesser trochanteric reduction fixation system.Nine patients who were diagnosed Evans Ⅲ intertrochanteric fractures are included. The lesser trochanteric reduction fixation system is used to fix the intertrochanteric fractures with the combined fixation of dynamical hip screw and lag screw in the operation by experienced doctors. The patients were postoperative followed-up by us.Result1There was no significant changes of the stressful endurability in both the medial femoral cortex and the DHS when the isolated lesser trochanteric was involved in intertrochanteric fractures. When half of the medial cortex was involved, the stressful endurability of the DHS had increased by9%with a28%in the medial femoral cortex. The stressful endurability of the DHS and the medial femoral cortex were respectively increased by96%and125%when the entire medial cortex was involved. After using4.5mm lag screws to fix the lesser trochanteric and the medial cortex, the largest stressful endurability of all parts had reduced. There were no significant differences between two groups when comparing to the simple intertrochanteric fractures.2The patients of clinical trials were all followed-up after the operations. The mean of the follow-up time was9months, the maximum time was12months and the minimum time was8months. The results of the treatment are satisfied. According to GongYi Huang’s assessment standards, seven are superior and two are good in the nine cases and the excellent rate was100%.Conelusion1When the intertrochanteric fracture is company with isolated lesser trochanteric fracture, it will be safe to not to fix it. But when the medial cortex (no matter half or entire of it) is involved, the continuity of the cortex should be restored. Restoring the continuity of the medial cortex can enhance the conduction for vertical load of the proximal femur and lower the local stress. According to this theory, complications such as coxa vara, steel plate failure, femoral head and neck cutting and shortening of the lower limbs can be reduced or even avoided.2Dynamical hip screw (DHS) companied with lag screw is a good way to treat the intertrochanteric unstable fractures. Its impressive effect is benefits from the fixation of the medial cortex which restored the biomechanics characteristics of the proximal femur. Using the lesser trochanteric reduction fixation system can restore the continuity of the medial cortex in maximum and expand the range of dynamical hip screw treatment in intertrochanteric fractures. |
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