Over time, the locking mechanism of Modular Universal Tumour and Revision System (MUTARS) knee arthroplasties changed from polyethylene (PE) to polyether-ether-ketone Optima (PEEK) and metal-on-metal (MoM) in an attempt to reduce the risk of mechanical failure. In this study, we aimed to assess the cumulative incidence of locking mechanism revision for symptomatic instability by type of material, and assess potential associated risk factors. The MUTARS Orthopaedic Registry Europe was used for a retrospective review of 316 patients (54% male (n = 170), median age 44 years (IQR 23 to 61)) who underwent a MUTARS knee arthroplasty for oncological indications between December 1995 and January 2023. The minimum follow-up was 12 months, and the median follow-up was 7.9 years (IQR 3.3 to 13.0). A competing risk model was used to estimate the cumulative incidence of first locking mechanism revision with death and revision for any other reason as competing events. Possible risk factors were assessed employing a univariate cause-specific hazards regression model.Aims
Methods
We undertook a cemental unipolar proximal femoral endoprosthetic replacement in 131 patients with a mean age of 50 years (2 to 84). Primary malignant tumours were present in 54 patients and 67 had metastatic disease. In addition, eight patients had either lymphoma or myeloma and two had non-oncological disorders. The mean follow-up was 27 months (0 to 180). An acetabular revision was required later in 14 patients, 12 of whom had been under the age of 21 years at the time of insertion of their original prosthesis. The risk of acetabular revision in patients over 21 years of age was 8% at five years compared with 36% in those aged under 21 years. All the unipolar hips in this younger age group required revision within 11 years of the initial operation. We conclude that unipolar replacement should not be used in younger patients and should be avoided in patients with a life expectancy of more than five years.
