Immediate weight-bearing is safe following lateral locked plate fixation of periprosthetic distal femoral fractures.

Purpose: This study aimed to determine whether unrestricted weight-bearing as tolerated (WBAT) following lateral locking plate (LLP) fixation of periprosthetic distal femoral fractures (PDFFs) is associated with increased failure and reoperation, compared with restricted weight-bearing (RWB).

Materials and methods: In a retrospective cohort study of consecutive patients with unilateral PDFFs undergoing LLP fixation, patients prescribed WBAT were compared with those prescribed 6 weeks of RWB. The primary outcome measure was reoperation. Kaplan-Meier and Cox multivariable analyses were performed.

Results: There were 43 patients (mean age 80.9 ± 11.7 years, body mass index 26.8 ± 5.7 kg/m² and 86.0% female): 28 WBAT and 15 RWB. There were more interprosthetic fractures in the RWB group (p = 0.040). Mean follow-up was 3.8 years (range 1.0-10.4). Eight patients (18.6%) underwent reoperation. Kaplan-Meier analysis demonstrated no difference in 2-year survival between WBAT (80.6%, 95% CI 65.3-95.9) and RWB (83.3%, 95% CI 62.1-100.0; p = 0.54). Cox analysis showed increased reoperation risk with medial comminution (hazard ratio 10.7, 95% CI 1.5-80; p = 0.020) and decreased risk with anatomic reduction (hazard ratio 0.11, 95% CI 0.01-1.0; p = 0.046). Immediate weight-bearing did not significantly affect the risk of reoperation compared with RWB (relative risk 1.03, 95% CI 0.61-1.74; p = 0.91).

Conclusions: LLP fixation failure was associated with medial comminution and non-anatomic reductions, not with postoperative weight-bearing. Medial comminution should be managed with additional fixation. Weight-bearing restrictions additional to this appear unnecessary and should be avoided.