The effect of local bone density on mechanical failure after internal fixation of pertrochanteric fractures

The aim of this prospective study was to investigate the effect of local hip bone density on mechanical failure after fixation of pertrochanteric fractures and to establish possible risk factors for the failures. A total of 136 consecutive patients presenting a closed unilateral pertrochanteric fracture were enrolled. The patients were treated with a sliding hip screw or an intramedullary nail. Dual energy X-ray absorptiometry measurements for bone density of the contralateral hip were made within 4 weeks postoperatively. Follow-up evaluations on the standard radiographs were documented for any mechanical failure including loss of reduction, screw or blade cut-out, lateral migration of the screw or blade, and implant breakage. Secondary outcomes were also recorded including patient characteristics and fixation construct variables as possible predictors for mechanical failure. At a minimum of 2 years of follow-up, 38 patients were reported with mechanical failure at an estimated risk of 27.9 %. The local bone density measurements for the study population showed no difference between patients with (0.710 g/cm(2)) and without (0.726 g/cm(2)) mechanical failure (P = 0.180). We also observed no significant correlation between local bone density and failure in patients with good fracture reduction (P = 0.862). The multivariate regression analysis identified fracture type (P < 0.001) and quality of fracture reduction (P < 0.001) as being independent predictors for mechanical failure, whereas local bone density was not (P = 0.658). Local hip bone density does not appear to have a significant influence on mechanical failure after internal fixation of pertrochanteric fractures. Stable fractures and fractures with good reduction are expected to obtain satisfactory outcomes.