Efficacy Evaluation of Primary Oncological Knee Arthroplasty in Patients with Tumor Involvement of the Distal Femur

The aim of the study was to determine the factors influencing functional outcomes and the likelihood of mechanical and infectious complications in patients with tumor involvement of the distal femur who underwent primary oncological knee arthroplasty. Methods. We analyzed the treatment results of 227 patients who underwent primary oncological knee arthroplasty for tumor involvement of the distal femur between 2003 and 2018. Functional outcomes were assessed using the MSTS scale at the 12-month follow-up, while mechanical and infectious complications were evaluated according to the ISOLS classification. We also examined the factors affecting these outcomes. Results. Various types of complications occurred after an average period of 70.5 months in 70 (30.8%) patients: infection (type IV) — 16 cases (7.1%); prosthesis failure (type III) — 13 (5.7%); instability of prosthetic components (type II) — 41 (18.1%). Active drainage did not affect the risk of infectious complications but significantly reduced postoperative hospital stay (p0.001). Patients weighing more than 90 kg had a statistically significant increase in the risk of construct failure (p = 0.044). The use of rotating platform prostheses significantly reduced the risk of component failure (p = 0.016). When anatomical femoral stems and rotating platform prostheses were used, there was a significant reduction in the risks of component instability (p0.001). The type of fixation did not increase the risk of mechanical complications (p = 0.860). Utilization of a thin cement mantle decreased the risk of prosthesis instability by 5.1 times compared to standard cementation techniques, with statistically significant differences in odds ratios. The median function of the knee joint, as measured by the MSTS scale, was 80%. Patients operated through the subvastus approach demonstrated the best joint function (p0.001). At the 60-month follow-up, overall prosthesis survival rates ranged from 80 to 100%. However, at 125 months, the leading prostheses were Stryker (92.9%), Mutars (71.8%), and Biomet (69.1%). Conclusions. Rotating-hinge endoprostheses showed optimal performance in reducing the risks of mechanical complications and increasing a construct lifespan. It is essential to use anatomically shaped stems when installing the femoral component. The choice of fixation method does not influence survival rate or stability of the component. It does, however, allow surgeons to take an individualized approach based on the patient’s weight, age, and bone condition. The medial subvastus approach offers the most favorable conditions for restoring knee joint function.