[Biomechanical study of the lateral wall of the femur in the treatment of femoral intertrochanteric fracture with intramedullary or extramedullary fixation].

Objective: To observe the biomechanical effects of the lateral wall of the femur in treating femoral intertrochanteric fractures with intramedullary or extramedullary fixation to guide the choice of clinical fixed methods.

Methods: Twelve adults femur specimens of intertrochanteric fractures were belong to the type A1 of the AO fracture classification and randomly divided into the lateral wall complete PFNA group, the lateral wall complete PF-LCP group, the lateral wall breakage PFNA group, lateral wall breakage PF-LCP group, every group had 3 specimens. The four groups of specimens were subjected to compressive loading experiment with Universal Material Testing Machine. The maximum loading force was observed. The distance between fracture ends, the distance of fracture dislocation and the sliding distance of the fracture fragments along the intertrochanteric were measured with Calipers.

Results: The maximum loading force of lateral wall complete PFNA group were larger than that of lateral wall complete PF-LCP group, and the maximum loading force of lateral wall breakage PFNA group were larger than that of lateral wall breakage PF-LCP group, there were significant differences (<0.05). The distance between fracture ends of the four groups before compression were not significant differences(>0.05). The distance between fracture ends, the distance of fracture dislocation and the sliding distance of the fracture fragments were not significant differences between lateral wall complete PFNA group and lateral wall complete PF-LCP group after compression (>0.05). But the distance between fracture ends, the distance of fracture dislocation and the sliding distance of the fracture fragments of lateral wall breakage PFNA group were less than that of lateral wall breakage PF-LCP group(<0.05).

Conclusions: Intramedullary fixation of intertrochanteric fractures have stronger loading force. Both intramedullary and extramedullary fixation of intertrochanteric fractures have strong stability when the lateral wall of the femur is complete, but intramedullary fixation of intertrochanteric fractures is stronger stability than extramedullary fixation when the lateral wall of the femur is broken. So the intramedullary fixation is the first choice for the treatment of intertrochanteric fracture.