Revision surgeries for tumor endoprostheses around the knee joint: a mid-long-term follow-up of 20 cases

BACKGROUND: Tumor endoprostheses of the knee joint after limb salvage surgery is associated with high rates of complications, which has introduced great challenges to a delayed revision surgery. The aim of the study was to summarize the failures, functional outcomes and prosthetic survival in revision tumor endoprostheses of the knee joint. METHODS: The clinical data of 20 patients with malignant tumors who received prosthetic revisions after limb salvage surgery from January, 2000 until January, 2018 were retrospectively reviewed. The cohort was constituted of 11 male and 9 female patients with a mean age of 34.1 years (range, 16 to 66 years). Infection cases received two-stage revisions after removing prostheses initially, while all other cases received one-stage revisions. Revision reasons and complications were well documented and analyzed. RESULTS: All patients received complete follow-up with a mean time of 64.7 months (range, 27 to 155 months). A total of 6 (6/20, 30.0%) patients experienced a second complication after revision surgery, of whom, one patient with deep infection experienced repeated infections after prosthetic revision and received amputation surgery; one patient revised of prosthetic fracture experienced an infection and received a second-stage infection revision; one case revised of prosthetic loosening had deep infection receiving anti-infective therapy with prostheses still in position; one case having wound complication healed after receiving two times of debridement surgery; one MBGCT patient experienced a second aseptic loosening 6 years after the initial loosening thus undergoing a second revision; a recurrent osteosarcoma patient died of pulmonary metastasis 3 years after revision surgery. Kaplan-Meier survival curve indicated a 5-year survival rate of initial prostheses was 75%. The Musculoskeletal Tumor Society (MSTS-93) score [20.9 (range, 15 to 27 scores)] at 1 year after revision surgeries was significantly improved (p < 0.001) when compared with the score [17.2 (range, 13 to 21 scores)] before revisions. CONCLUSION: Prosthetic mechanical problems, aseptic loosening and infections were primary reasons for revisions after tumor endoprostheses of the knee joint. Although revision surgeries were complicated while still associated with high risk of failure, which remains the remedy strategy for limb salvage and functional recovery in those patients.