In metal-on-metal (MoM) hip arthroplasties and resurfacings, mechanically induced corrosion can lead to elevated serum metal ions, a local inflammatory response, and formation of pseudotumours, ultimately requiring revision. The size and diametral clearance of anatomical (ADM) and modular (MDM) dual-mobility polyethylene bearings match those of Birmingham hip MoM components. If the acetabular component is satisfactorily positioned, well integrated into the bone, and has no surface damage, this presents the opportunity for revision with exchange of the metal head for ADM/MDM polyethylene bearings without removal of the acetabular component. Between 2012 and 2020, across two centres, 94 patients underwent revision of Birmingham MoM hip arthroplasties or resurfacings. Mean age was 65.5 years (33 to 87). In 53 patients (56.4%), the acetabular component was retained and dual-mobility bearings were used (DM); in 41 (43.6%) the acetabulum was revised (AR). Patients underwent follow-up of minimum two-years (mean 4.6 (2.1 to 8.5) years).Aims
Methods
We found the ABG cementless hip has excessive acetabular wear and premature failure due to osteolysis. In 60 patients implanted at mean age 56 years, 66 hips (mean follow up 48 months), 7 were revised and 7 have severe acetabular osteolysis. In some this is entirely asymptomatic. There was significant association with osteolysis, length of follow up and wear but no correlation between wear and acetabular component position, age, liner thickness, and use of ceramic or CoCr heads. We recommend regular lifelong radiological review of these hips and suspension of use of this prosthesis until a wider review is undertaken.
We wished to determine the most accurate and reliable technique for insertion of tibial prostheses, with tibial resection guided by either intramedullary (IM) or extramedullary (EM) alignment jigs. 135 consecutive AGC cemented total knee replacements in 126 patients in a single unit were performed by, or directly supervised by, four consultant surgeons. Ethical approval and patient consent was obtained. Intramedullary alignment was used for the femoral cuts and patients were randomised at the time of operation to have either IM or EM guides for resection of the proximal tibia, cut with a zero degree posterior slope in both. The protocol only entered patients into the trial if their knees were suitable for use with both IM and EM tibial alignment although, in the event, no patients were excluded. Long leg radiographs (standing hip to ankle) were taken by a standardised method three months after the surgery. A blinded assessor, unaware of the alignment method used, evaluated acceptable films and measured tibial component alignment. The proportion of tibial prostheses aligned within two degrees of 90 was the endpoint of the study. Of the 135 knees 100 suitable x-rays were assessed. Correct tibial alignment was more likely in the IM group (85%) than the EM group (65%), p=0. 019. Though mean alignment was similar, variation (standard deviation) was less in the IM group (2. 0 vv 2. 2). In the AGC knee, intramedullary alignment guides are superior to extramedullary guides for alignment of the tibial prosthesis. We recommend the routine use of intramedullary tibial alignment.