Well-reduced bisphosphonate-associated atypical femur fractures have low rates of nonunion and delayed union.

INTRODUCTION

Bisphosphonate-associated atypical femur fractures have been reported to have high rates of delayed union and nonunion, as well as high rates of contralateral fracture. There have been limited studies looking at specific factors associated with delayed union or nonunion of atypical fractures. Many studies are limited by small numbers of patients. To date, no studies have examined the effect of reduction technique (closed versus open versus percutaneous) and reduction quality on healing.

METHODS

This was a multicentered retrospective review of patients greater than 50 years of age with atypical femur fractures treated surgically at level 1 orthopedic trauma center. Patients who were lost to follow-up prior to radiographic union or who were lost to follow-up prior to 6 month follow-up and who had not yet achieved radiographic union were excluded. The primary outcome was union. Secondary outcomes included time to radiographic healing and reoperation.

RESULTS

A total of 148 patients with atypical femoral shaft fractures were identified; 75 patients met inclusion criteria. All were female, with an average age of 75 (standard deviation 8.8). Fifty underwent a closed reduction, 15 underwent open reduction, and 10 had a percutaneous reduction. Reduction quality was excellent in 97% of patients. All patients were treated with an intramedullary implant. Two patients (3%) went on to nonunion, which was diagnosed at an average of nine months postoperatively. Three patients (4%) had delayed union. The median time to union was 3.1 months (IQR 2.9-3.6). In univariate analysis, subtrochanteric fracture location, poor reduction quality, open fracture, and open reduction were each independently associated with increased risk of nonunion or delayed union. The rate of contralateral fracture was only 5% at a median follow-up of 4 years.

DISCUSSION/CONCLUSION: In this cohort of patients with a high rate of well-reduced bisphosphonate-associated femoral shaft fractures, the rate of nonunion and delayed union as well as the median time to radiographic union is significantly lower than has been previously reported. Varus and flexion malreduction, fracture plane gap, open fracture, performing an open reduction, and subtrochanteric fracture location were each independently associated with increased risk of nonunion and delayed union. Finally, there was a low rate (5%) of contralateral fracture.