Does patellar height influence functional outcomes after reconstruction in distal femur tumours?

Background: Patellar height plays a critical role in maintaining knee biomechanics and extensor mechanism efficiency. While its significance after total knee arthroplasty is well documented, its impact following distal femoral endoprosthetic reconstruction remains underexplored. The objective of this study was to evaluate the relationship between patellar height and functional outcomes using the Musculoskeletal Tumour Society-93 (MSTS) score and to assess the influence of patellar height on extensor lag and knee range-of-motion (ROM). Methods: This retrospective single-centre study included 61 patients who underwent intra-articular resection and endoprosthetic reconstruction for primary malignant and benign aggressive distal femur tumours between January 2018 and December 2023. Patellar height was measured using the modified Caton-Deschamps (mCD) index and categorized into baja, norma and alta. Clinical assessment included measurement of extensor lag, knee ROM and MSTS-93 scores. To evaluate intergroup differences and correlations, statistical analysis was performed. Results: Mean age was 27.52 ± 13.27years, including 36 males(59 %) and 25 females(41 %). Median follow-up was 13months(IQR6.5-32.5). Mean femoral resection length was 15.43 ± 3.23 cm and mean tumour volume resected was 450.48 ± 288.63 cm3. Mean patellar height(mCD index) in the baja(n = 5), norma(n = 44) and alta group(n = 12) was 0.48 ± 0.14, 1.03 ± 0.15 and 1.43 ± 0.10 respectively and median MSTS-93 score was 27.5(IQR21.5-29), 29(IQR27-30) and 29(IQR28.25-30) respectively. Median knee ROM was 100°(IQR90°-120°). Twenty-six(42.6 %) individuals had a median extensor lag of 15°(IQR10°-20°). Comparison of MSTS-93 score(p = 0.228), flexion ROM(p = 0.350) and extensor lag(p = 0.910) between the 3 groups showed no significant differences. The correlations between patellar height and MSTS-93 score(ρ = +0.206,p = 0.112), flexion ROM(ρ = +0.169,p = 0.194) and extensor lag(ρ = -0.020,p = 0.880), were not statistically significant. Conclusion: Although not statistically significant, patients with patella norma and alta demonstrated better functional outcomes. While no definitive correlation was established, the findings suggest that patellar height may influence functional recovery after distal femoral endoprosthesis reconstruction, and larger prospective studies are needed to validate these findings.