(P 89) PATELLAR HEIGHT AND ITS INFLUENCE ON FUNCTIONAL OUTCOMES FOR MEGAPROSTHESES AROUND THE KNEE PERFORMED FOR ONCOLOGICAL INDICATIONS

Objective: Distal femur and proximal tibia are the most common sites for osseous involvement in bone and soft tissue sarcomas. Endoprosthetic implants are widely used methods for reconstruction. The influence of patellar height is extensively studied in primary joint replacement literature. Its effect is somewhat less recognized in megaprosthesis reconstruction, given the extent and the multiplicity of associated factors. This study aimed to evaluate the impact of patellar height on patients who underwent distal femur and proximal tibia megaprosthesis reconstruction.

Methods: This retrospective study included 118 patients (93 distal femur and 25 proximal tibia reconstructions) who had bone and soft tissue tumors treated in a single institution. Data recorded included patient demographics, tissue diagnosis, history of radiotherapy, surgical approach, number of previous surgeries, polyethylene thickness, resection length, resection/total segment ratio, Insall-Salvati (IS) ratio, knee range of motion (ROM), extensor lag, and Musculoskeletal Tumor Society Score. Patients were followed up at least one year until their latest office visit or revision surgery due to failure.

Results: The mean age at surgery was higher for the distal femur group (37.8 ± 20.8 years) vs. the proximal tibia group (32.5 ± 18.9 years). Osteosarcoma was the most common diagnosis (53.8% and 64.0%, respectively). Number of prior surgeries was 0.67 ± 1.35 for distal femur and 1.16 ± 1.99 for proximal tibia. Postoperative patellar height, measured by IS ratio, was greater in the proximal tibia group (1.19 ± 0.53) than in the distal femur group (1.01 ± 0.24), with patella alta more common (52.0% vs. 12.9%). A higher IS ratio was significantly associated with improved postoperative ROM in both distal femur (β = 0.002, p = 0.034) and proximal tibia (β = 0.009, p = 0.007) groups. No significant associations were observed with extensor lag or MSTS score. In proximal tibia cases, resection proportion (β = –9.332, p = 0.038) and radiotherapy (β = 1.325, p = 0.023) were independently associated with IS ratio; no significant predictors were found for distal femur.

Conclusion: This study demonstrated that postoperative patellar height, as identified by IS ratio, is positively associated with knee ROM following both distal femur and proximal tibia reconstructions. In proximal tibia cases, resection extent and radiotherapy influence IS ratio, highlighting the impact of surgical and adjuvant factors on functional alignment.