Pilot Study Of Pourable Dynamic Hip Screw For The Treatment Of Osteoporotic Intertrochanteric Fracture

Backgroud: Osteoporotic intertrochanteric fractures are prevalent diseases in the clinical settings , which occur predominantly in the elderly.With rich blood supplying, intertrochanteric fractures are easily healed. DHS (dynamic hip screw) is the often used inter-fixator for stable osteoporotic intertrochanteric fractures,which has dual function of sliding and pressing. However,duing to the existence of osteoporosis, screw holding force is weakened.We can often find that the lag screw displace , even cut the femoral head and neck, leading to the failure of the internal fixation.Objective: To study the biomechanical properties of pourable dynamic hip screw augmented with bone cement in osteoporotic intertrochanteric fractures and dispersion of the bone cement in the femoral head and neck.Methods: According to the clinical character of osteoporotic intertrochanteric fractures ,the advantages and disadvantages of dynamic hip screw (DHS), we designed bone cement pourable dynamic hip screw to improve fixation.We choosed fresh embalmed osteoporosis hip cadavers (two males and four females) to make the specimens of the intertrochanteric fracture models of Type AO31 - A1 after bone mineral density being performed by dual-energy X-ray absorptiometry.Under C arm X-ray fluoroscopy ,one side was fixed with DHS(setted as the control group) randomly ,and the other was fixed with prurable DHS(setted as the experimental group), CT coronal scanning was conducted for specimens to observe bone cement diffusion.The biomechanical tests on the bending stiffness were performed with the multifunctional biomechanics tester. Each specimen was loaded 200N firstly to eliminate elastic creep, then continued to loading to 1000N, repeated 50 times, recorded the maximal displacement and stiffness. After loading continued to a failure,the load data showed by biomechanical machine were recorded as the maximum loading.The data was analysed statistically by using paired t test.Results: All of internal fixator of 6 groups were well placed, One lag screw exitted and the big trochanter fracture was observed in the control group for repeated compression tests .The average stiffness of the experimental group was 929.629493 N/mm, increased by 80.84% (t=5.11 p=0.004) compaired with the control group (514.070792N/mm) and the maximal displacement of experimental group was 1.15075mm decreased by 52.51%( t=8.511 p=0.000) compaired with the control group(2.422915mm).The maximum loading of experimental group was 3664.3N while the control group was 2845.7N (t=7.985 p=0.001),all with significant differences.CT coronal scanning showed that bone cement well diffused.Conclusion: Pourable DHS provided more stable and lower cutting possibility than conventional DHS for the treatment of intertrochanteric fractures,and the bone cement diffused satisfiedly.