Results of Low Distal Femur Periprosthetic Fractures.

Objectives: To compare retrograde intramedullary nail (RIMN) and open reduction internal fixation (ORIF) in very distal periprosthetic distal femur fractures (PDFFs) to determine whether RIMN is an acceptable option for these fractures that are often considered too distal for IMN due to limited bone stock.

Design: Retrospective comparative series.

Setting: Level 1 trauma center.

Patients: Patients were treated with fracture fixation for a very distal PDFF, defined as the fracture extending to the anterior flange of the implant or distal. Fifty-six patients met inclusion criteria, with 8 excluded for less than 12 months of follow-up.

Intervention: The intervention involved fracture fixation with RIMN or ORIF.

Main Outcome Measurements: The primary outcome was unplanned return to surgery. Secondary outcomes included fracture union, radiographic alignment, visual analog score, and Patient-Reported Outcome Measurement Information System (PROMIS) Physical Function (PF) and Pain Interference.

Results: The mean follow-up period was 27 months. Twelve patients were treated with ORIF and 36 with RIMN. Twenty-one fractures were at the flange, and 27 extended distal to the flange. There were no differences between fixation methods for reoperation, deep infection, nonunion, malunion, visual analog score pain score, and PROMIS Pain Interference score. The mean PROMIS PF score was higher in the RIMN group compared with that in the ORIF group. There were 5 reoperations in the RIMN group (14%) and 3 in the ORIF group (25%).

Conclusions: This is the largest series, to the best of our knowledge, of a subset of very distal PDFFs. The results suggest that RIMN may be an acceptable treatment option for these very difficult fractures.

Level Of Evidence: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.