Combined plate-assisted fixation of femoral diaphyseal prosthesis in the treatment of bone tumors with 41 cases: retrospective cohort study

Background Aseptic loosening remains the primary cause of failure in segmental prosthetic reconstruction. The application of auxiliary plates to diaphyseal prostheses may serve as an effective strategy to enhance early mechanical stability and reduce the incidence of aseptic loosening. However, few studies have systematically evaluated or standardized the use of such plates. Method This retrospective, observational study included 47 patients who underwent femoral diaphyseal prosthesis implantation with auxiliary plate fixation between 2011 and 2024. After excluding six patients lost to follow-up, a total of 41 patients (19 males and 22 females; mean age 60.3 ± 18.1 years) were retrospectively analyzed with a median follow-up duration of 16 months (range, 3 to 120 months). Data regarding the auxiliary plates, including location and quantity, were collected and used to classify plate application types. Postoperative functional outcomes were evaluated using the Musculoskeletal Tumor Society (MSTS) scoring system. The incidence, type, and timing of mechanical failure of the prosthesis were recorded, and prosthetic survival was assessed using competing risk analysis and Kaplan-Meier survival curves. Subgroup analyses were conducted based on baseline characteristics, with linear or logistic regression models applied depending on data type. To further explore the indication criteria for auxiliary plate usage, optimal cutoff values were identified using the method of maximized log-rank statistics. Results All surgeries proceeded uneventfully. Except for one patient who developed postoperative edema, no other patients experienced significant short-term complications. All patients reported satisfactory postoperative functional outcomes. At final follow-up, the majority of patients (29 patients, 70.7%) achieved good recovery (MSTS ≥ 24), with no significant correlation observed between functional recovery and plate usage. Competing risk analysis between mechanical failure and death revealed that the 1-, 2-, 5-, and 10-year overall prosthesis survival rates were 89.8%, 89.8%, 89.8%, and 87.0%, respectively. For patients with higher reconstruction ratios (reconstruction length/femoral diaphyseal length), auxiliary plate fixation also provided satisfactory early mechanical stability. The maximized log-rank test identified a reconstruction ratio of 0.341 as the optimal cutoff for predicting prosthesis mechanical failure, with a significantly higher failure rate observed in patients with reconstruction ratios > 0.341 (p = 0.031). Conclusion The use of auxiliary plates can effectively improve the mechanical survival of femoral diaphyseal prostheses and reduce the incidence of postoperative complications. Overall, auxiliary plate-assisted fixation yields favorable therapeutic outcomes and represents a viable option for reconstruction following femoral diaphyseal tumor resection. We recommend plate-assisted fixation, particularly in patients with higher reconstruction ratios. Level of Evidence Level III, Retrospective cohort study