BIOMECHANICAL STUDY ON FEMORAL-NECK FRACTURE FIXATION IN RELATION TO BONE-MINERAL DENSITY

Twenty pairs of fresh-frozen cadaveric femurs were used in the study. The left femurs were used as control for the mechanical testings and b one mineral content scans, the right femurs were divided into two expe rimental groups, i.e. 'fractured' group and 'healed' group. In the 'fr actured' group, twelve right femurs were osteotomized at the plane per pendicular to the femoral neck shaft axis, through the mid-cervical ar ea of the femoral neck. The artificially created fractures were fixed with the AO dynamic hip screw system using a 4-hole plate and a compre ssion screw. In the 'healed' group, the dynamic hip screws were applie d to eight intact right femurs to simulate healed fractures. Bone mine ral density scans and mechanical testings were performed on all the fe murs. Good correlation was observed between bone mineral density and f emoral neck strength in the control group. There was a decrease of 43. 5% in strength in the 'fractured' group when compared to the control g roup. However, in the 'healed' group the failure load was found to be 15.2% lower than the control group. The femoral fixation strength in t he 'fractured' and 'healed' groups had good correlation with the bone mineral density. Results from this study indicated that bone mineral d ensity is an important predictive factor in fracture fixation failure. Therefore it may be appropriate to consider the bone mineral density of a patient with proximal femoral fracture treated with fixation devi ces, as a criterion in prescribing a more protective postoperative man agement, with respect to weight bearing protocol.