Biomechanical Study And Clinical Observation Of Three Surgical Methods For Fixation Of Stable Intertrochanteric Fractures

Objective To evaluate the biomechanical and clinical effects comparison of Two methods of Orthofix pertrochanteric fixator(OPF) and Dynamic hip screw(Dynamic hip screw,DHS),three kinds of extramedullary fixation methods fixed stable intertrochanteric fracture.Method Selection of proximal femoral mold(sawbone)9 roots, witch were randomly divided into 3 groups, fixed using external fixator with the proximal half-pin placed into the femoral head in convergent way(OPFC group), the external fixator with proximal half-pin placed into the femoral head in parallel way(OPFP group),and the DHS. Make sure that each fixator is in good position and then remove all the fixators. Cutting each mold along the intertrochanteric crest using the wire saw to create the intertrochanteric fracture model(31A-1.1) according to the AO classification. Then the reduct the fracture and re-fix the mold and then past strain gauge on distal side of the fracture, The fracture model on the biomechanical tester with axial compression stress was applied by simulating the state of human standing on one foot. For each fracture model axial vertical load was applied by the loading speed of 10 mm / min. Record strain values at different points around the fracture line, the stress distribution, the vertical displacement of the femoral head and calculate the fragments considerable contact area and axial stiffness of each fracture model under different loads(200N, 400 N, 600 N, 800 N, 1000 N, 1200N),and then stability of the fixed model was tested under torsional stress, record the rotation angle of each fracture model in different torques(4NM, 8NM, 12NM) and calculate the rotational stiffness. Selected femoral intertrochanteric fracture 117 cases,from 2010 to 2014,which older than or equal to 65 years of age,among them 41 cases with OPFC,application of OPFP fixed 29 cases,application of DHS fixation of 47 cases.This group of male 50 cases,female 67 cases;65 to 93 years old,average 78.65 years.Compare the incision length,operative time,intraoperative blood loss,postoperative flow and bed time, postoperative complications, postoperative functional status of joint between the three methods of treatment etc.Result 1. Stress distribution and the strain values of the fracture site. The including tension side of OPFC group and DHS group were all pressure stress, but the OPFP group were pulled stress at the two lateral points,and pressure stress at the three points near the femoral calcar,We could see the stress distribution of OPFC group and DHS group around the screw in all the 5 points.but the OPFP group only at the 3points near the femoral calcar, there is no difference between OPFC group and DHS group. The fragments considerable contact area of OPFC group and DHS group are superior to OPFP group(P<0.05). 2.OPFC are superior to OPFP and DHS in vertical displacement of the femoral head, axial stiffness, torsional stiffness and the mechanical properties of torsional displacement(p<0.5). OPFP and DHS are the same(p>0.5).3.117 patients received postoperative follow-up of 6 to 18 months(mean 13.6months), OPFC and OPFP are superior to DHS in the operation time,the blood loss, the time to union,the time in bed. OPFP group is superior to OPFC group in operation time(p<0.5)). There is no difference in incision length, blood loss between OPFP group and OPFC group(p>0.5),there is no statistically significant difference in postoperative SANDERS pain score, postoperative complications in plants(plants within the femoral head cutting out,varus of the proximal femur,the failure of the plant), postoperative function in 1 year in three kinds of fixation(P>O.05).Conclusion 1.OPFC has a better biomechanical advantage than the OPFP and DHS in resisting axial compression and anti-rotation ability, OPFC and DHS have quite the same considerable contact area. 2.The orthofix pertrochanteric fixator has good clinical outcome in treatment of intertrochanteric fracture, which has advantages of simple operation, less operative time, little bleeding, early functional exercise, but it also has the disadvantage of superficial skin reactions, and for the cases of osteoporosis and fractures smash cases complications.In DHS fixation method,more traumatic,hemorrhage, intraoperative bone splitting possibility and postoperative complications in plants and larger possibility of the loss of reduction.All three types of fixation is an effective method in treatment of intertrochanteric fractures and OPFC method is comparative advantage in extramedullary fixation method.