The risk factors for mechanical complication in endoprosthetic reconstruction of knee osteosarcoma

The increased limb survival rates and higher functional demands have also increased the mechanical complication rates of megaprostheses. This study aimed to analyse possible risk factors which can predispose patients to mechanical complications.

Patients with knee osteosarcoma referred to our clinic from 1992 to 2014 were investigated retrospectively. The patients who underwent surgical resection and endoprosthetic reconstruction with at least 5 years of follow up were analysed. The revision of the megaprosthesis due to a mechanical complication was accepted as an endpoint. The possible risk factors, including cement usage, implant material, joint mechanism, neoadjuvant radiotherapy, and anatomical localization of the lesion, were analysed for any association with mechanical complication rates.

A total of 118 patients were included for final analysis. The average age was 24.5 years (standard deviation ±10.1, range: 15-64). Mechanical complication rate was 22% which included 19 aseptic loosenings and seven implant failures. The average time to mechanical complication was 32.5 months. Overall, 5-year implant survival was 78%. Multiple regression analysis revealed that cement usage is an independent risk factor for mechanical complication (P = 0.007). Although the 5-year implant survival was higher in rotating hinge and titanium implants compared with fixed hinge and cobalt chrome, the multiple regression model did not yield a correlation with mechanical complication rates.

Cemented implants showed significantly higher mechanical complication rates compared with cementless ones in this series of knee osteosarcoma patients who underwent megaprosthetic reconstruction. Hinge mechanism and implant material did not have a significant effect on mechanical complication rates.