Prior Femoral Canal Instrumentation Is a Major Risk Factor for Fixation Failure After Distal Femoral Replacement.

BACKGROUND

Distal femoral replacement (DFR) is a salvage option for massive femoral bone loss and is often performed in revision total knee arthroplasty (rTKA) that have undergone multiple prior procedures. This study aimed to report on a large cohort of DFRs performed at a tertiary referral institution regarding survivorship and risk factors for aseptic loosening, specifically the impact of a previously instrumented femoral canal.

METHODS

Between 2016 and 2021, 105 patients undergoing rTKA to DFR with a minimum 2-year follow-up were identified. Kaplan-Meier estimates assessed survivorship free from all-cause reoperation, all-cause revision, and revision for aseptic loosening. Logistic regressions were conducted to assess potential risk factors for radiographic loosening and the need for revision.

RESULTS

Prior femoral canal instrumentation was identified in 59% of cases, and 54% had undergone multiple prior procedures. The 2-year survivorship free from revision for aseptic loosening was 93%. The 2-year survivorship free from all-cause reoperation was 87% for native canals and 59% for previously instrumented canals (P = 0.008). The 2-year survivorship free from all-cause revision was 100 and 81%, respectively (P = 0.014). Regression analysis found re-rTKA (odds ratio [OR] = 18.3, P = 0.006), prior femoral canal instrumentation (OR = 14.6, P = 0.01), and prior femoral canal cementation (OR = 8.2, P = 0.007) to be risk factors for aseptic loosening.

CONCLUSIONS

A DFR for rTKA had high 2-year survivorship free from revision for aseptic loosening (93%). Regression analyses revealed multiple risk factors for aseptic femoral component loosening with a previously instrumented femoral canal, resulting in a 2.8-times higher rate of reoperation, a 10.5-times higher rate of all-cause revision, and an 11-times higher rate of aseptic loosening. Future research on fixation strategies in sclerotic, previously instrumented femoral canals should be prioritized to reduce the risk of fixation failure in this high-risk cohort.