Factors affecting peri-implant fracture following locking plate for osteoporotic distal femur fractures.

INTRODUCTION: The purpose of this study is to evaluate the outcomes and to analyze the risk factors for the occurrence of peri-implant fracture after treatment of osteoporotic distal femoral fractures using a locking plate.

HYPOTHESIS: Risk factors affecting peri-implant fracture exist after locking plate fixation in osteoporotic distal femur fracture.

MATERIALS AND METHODS: Eighty-nine cases (88 patients) with osteoporotic distal femoral fractures were evaluated between January 2006 and January 2014. The cohort included 13 men and 76 women with a mean age of 70.4 (50-91). Mean duration of follow-up was 47.9 months (12 to 106). All patients with distal femoral fracture were treated with a locking compression plate. Bone mineralized densitometry measurement was obtained from all patients. Risk factors including sex, age, rheumatoid arthritis (RA), taking of bisphosphonate, primary or periprosthetic fracture after total knee arthroplasty (TKA), open or closed fracture, types of the most proximal screw (locking/cortical), and number of proximal screws were analyzed. Complication, union, time to union, and range of motion of knee were also evaluated.

RESULTS: All patients had osteoporosis with the mean BMD of -3.16 (-2.5∼-5.4). The mean range of motion of knee was 126 degrees (90-145). Eighty-four cases (94.4%) showed union, the mean time to union was 14 weeks (10-42). Peri-implant fractures occurred in four patients (4.5%) after bone union at mean 37.5 months (14-62) postoperatively. Eight patients had angular deformities of over 5 degrees. Nonunion was observed in 5 cases and superficial wound infection in 2 cases. There were eight patients with RA, two of whom had suffered a peri-implant fracture. In statistical analysis, rheumatoid arthritis or periprosthetic fracture in TKA patients was a risk factor for peri-implant fracture (P=0.039, 0.019, respectively), and other factors showed no statistical differences.

CONCLUSIONS: Treatment using a locking plate showed favorable outcomes in osteoporotic distal femoral fractures. However, peri-implant fracture could occur in patients with RA or periprosthetic fracture after TKA. Therefore, cautious consideration is required for management of osteoporotic distal femur fracture in patients with RA or periprosthetic fracture after TKA. Analysis of more cases will be needed in order to achieve conclusive results.

LEVEL OF EVIDENCE: Therapeutic study, level IV (retrospective study). See the Guidelines for Authors for a complete description of levels of evidence.