Biomechanical Study Of The Different Fixations For Complex Unstable Femoral Intertrochanteric Fractures

Part I Biomechanical Study of Different Fixations Based on SynboneModel for Complex Unstable Femoral Intertrochanteric FracturesObjective This study designed a new kind of proximal hip internal-fixator (PFI). Theaim of this study was to detect and compare the effectiveness of4different fixations forcomplex unstable proximal intertrochanteric fractures by biomechanical test.Methods24synbones of proximal femur were made to simulate the complexunstable femoral intertrochanteric fracture models (Evans-Jensen type III). They werefixed by dynamic hip screw (DHS), proximal femoral nail antirotation (PFNA), lessinvasive stabilization system for distal femur (LISS) in reversed pattern, and proximalfemoral internal-fixator (PFI). Four different fixation models,6for each group, were testedby biomechanical testing machine then.Results Under the compressing test, the fracture displacement of LISS was minimalduring300N,600N and1200N. There were significant difference between LISS systemand the other three models (P＜0.05). The fracture displacement of DHS was maximum,with significant difference comparing to PFNA and PFI (P＜0.05). There was nosignificant difference between PFNA and PFI (P＞0.05). Under torsional load, the anglechange of LISS was still minimal during300N,600N,1200N. There were significantdifference between LISS system and the other three models (P＜0.05). The torsionaldisplacement of DHS and PFNA at fracture were all maximum, with no significantdifference (P＞0.05). There were significant difference between PFI to both PFNA andDHS(P＜0.05).Conclusion There is significant superiority of LISS in compression and torsionresistance comparing with other3fixation groups. In the ability of compression resistance,PFI is similar to PFNA. However PFI was shown stronger than PFNA in torsionalresistance. DHS system was tested as the least resistance of compression or torsion. Part II Finite Elementary Analysis of Different Fixations for ComplexUnstable Femoral Intertrochanteric FracturesObjective By finite elementary analysis, the biomechanical performance of differentfixation for complex unstable proximal intertrochanteric fracture was observed. The resultof finite elementary analysis ware compared with it of entity model, and the consistency oftwo different biomechanical test methods for femoral intertrochanteric fracture wasevaluated.Methods The finite elementary model of adult complex unstable femoralintertrochanteric fractures was firstly established, and matching with four different fixationfinite elementary models, DHS, PFNA, reversed LISS and PFI. By compression load,torsion load, compression-torsion load, the stress distribution and deformation on thefracture site were analyzed.Results During these four different fixation models, the LISS had shown the bestresistance in both compression and torsion test. The compression resistance of PFI wasworse. And the torsion resistances of PFNA and DHS were worst.Conclusion The result of the finite elementary analysis was consistent with resule ofbiomechanical test. LISS is biomechanically the best fixation method for complex unstablefemoral intertrochanteric fractures. Furthermore, the PFI is also applicable to thesecomplex unstable fractures.