Design And Biomechanical Analysis Of A New Method For Fixation Of The Greater Trochanter

ObjectiveTo analyze the functional outcomes of intertrochanteric hip fractures retrospectively, explore the displacement of the greater trochanter after surgery on the prognosis of the fractures, design a new method for fixation of the greater trochanter and analyze its biomechanical efficacy.Methods(1) Follow up 636 patients of intertrochanteric fractures admitted to PLA General Hospital from 1993 to 2008, statistically analysis the information before,during and after surgery of the patient, compare the Harris Hip Score of all the patients grouped by the kind of treatment, and analyze the relationship between the displacement of the greater trochanter after sugery and the functional outcomes of intertrochanteric hip fracture.(2) Design a new method for fixation of the greater trochanter, which has two hooks in its proximal, while has two screw holes in its distant.(3) Five fresh-frozen human cadaveric proxiamal femora were used in biomechanical analysis.A cyclic shear load was applied, and displacement of the trochanter was measured with increasing load. Meanwhile, force required to displace to 1cm,2cm was recorded.Results(1) Among the 636 patients,145 patientswere lost during the follow up,28 patients committed to conservative treatment for disagreement to the surgry,111 patients died during the follow-up period.In all 225 patients, compare the difference between 109 cases of Jesen-Evans typeⅢand type V and 116 cases of Jesen-Evans typeⅠ,typeⅡ,typeⅣVand type R, The result shows that the Harris Hip Score is 87.628±8.509,84.971±7.742 respectively, which exists statistical significance of the Harris Hip Score (p=0.0153).Compare the different displacement of the greater trochanter at<1cm (34cases),1-2cm(62cases) and>2cm(13cases) of the 109 cases of Jesen-Evans typeⅢand type V. the Harris Hip Score is 89.50±8.510,80.692±7.983,85.573±7.651 respectively, which exists statistical significance of the Harris Hip ScoreAmong 109 cases of Jesen-Evans typeⅢand type V, consist of 30cases of Hemiarthroplasty and 79 cases of intramedullary fixation.Compare the difference of the age and efficacy of therapy.The group of Hemiarthroplasty is older than the other, but has no statistical significance (78.6±5.2岁,71.4±18.5岁p=0.357),while the group of Hemiarthroplasty attain better results than the other and has statistical significance(81.6±12.9,70.4±18.5, p=0.012).(2) Five fresh-frozen human cadaveric proxiamal femora were applied cyclic shear load.Force required to displace to 1cm is 1600N, force required to displace to 2cm is 2400N.When analyzing displacement of the greater trochanter at different loads, the trochanter diaplaced an average of 2mm with the initial load of 700N and continue to displace with each increase in load in a linar fashion. The trochanter diaplaced an average of 5mm with load of 1400N, an average of 15mm with load of 2100N and an average of more than 20mm with load of 2800N.Conclusions:(1) The displacement of the greater trochanter after surgery could decrease the function of gluteus medius significantly, thus for the fracture of dissociated greater trochanter, it is essential to have the greater trochanter repositioned and fixed properly.(2) The newly designed method for fixation of the greater trochanter can not only provide a solide fixation of the greater trochanteric fragment against shear load,but also offer a perpendicular pressure to accelerater the procedure of healing.(3) Through biomechanical analysis, we can conclude that this fixation method can stand the load to the greater trochanter during daily life, without the failure of the fixation.