Aims

Total knee arthroplasty (TKA) is a common and safe orthopaedic procedure. Zimmer Biomet's NexGen is the second most popular brand of implant used in the UK. The primary cause of revision after the first year is aseptic loosening. We present our experience of using this implant, with significant concerns around its performance with regards early aseptic loosening of the tibial component.

Aims

We review our experience of Coonrad-Morrey total elbow arthroplasty (TEA) for fractures of the distal humerus in non-rheumatoid patients with a minimum of ten years follow-up.

We evaluated the impact of pre-coating the tibial component with polymethylmethacrylate (PMMA) on implant survival in a cohort of 16 548 primary NexGen total knee replacements (TKRs) in 14 113 patients. In 13 835 TKRs a pre-coated tray was used while in 2713 TKRs the non-pre-coated version of the same tray was used. All the TKRs were performed between 2001 and 2009 and were cemented. TKRs implanted with a pre-coated tibial component had a lower cumulative survival than those with a non-pre-coated tibial component (p = 0.01). After adjusting for diagnosis, age, gender, body mass index, American Society of Anesthesiologists grade, femoral coupling design, surgeon volume and hospital volume, pre-coating was an independent risk factor for all-cause aseptic revision (hazard ratio 2.75, p = 0.006). Revision for aseptic loosening was uncommon for both pre-coated and non-pre-coated trays (rates of 0.12% and 0%, respectively). Pre-coating with PMMA does not appear to be protective of revision for this tibial tray design at short-term follow-up.

Cite this article: Bone Joint J 2013;95-B:367–70.

Hip implant retrieval analysis is the most important source of insight into the performance of new materials and designs of hip arthroplasties. Even the most rigorous in vitro testing will not accurately simulate the behavior of implant materials and new designs of prosthetic arthroplasties. Retrieval analysis has revealed such factors as the effects of gamma-in-air sterilisation of polyethylene, fatigue failure mechanisms of polymethylmethacrylate bone cement, fretting corrosion of Morse taper junctions, third body wear effects of both hard-on-hard and hard-on-soft bearing couples, and the effects of impingement of components on the full spectrum of bearing surfaces, none of which was predicted by pre-implantation in vitro testing of these materials and combinations. The temporal sequence of the retrieval process is approximately six years from first implantation through retrieval analysis, laboratory investigation, and publication of results, and thus, in addition to rigorous clinical evaluation, represents the true development and insight cycle for new designs and materials.

Here we present the results of functional outcome of 531 patients (aged from 27.6 to 88.7, mean 62.6) who have had the Trilogy (Zimmer; Warsaw IN, USA) acetabular shell implanted for 5 years or longer. All patients operated at our unit between 20/1/1992 and 31/3/2004 were included, looking at both Primary (431) and Revision (100) hip arthroplasties. All surgery was performed by the senior surgeon using the Trilogy shell and liners. The Trilogy acetabular shell was used with either an ultra-high molecular weight polyethylene liner or ceramic liner, along with a wide variety of femoral stems, mainly: Harris Pre-coat stem (183 patients, Zimmer), Versys cemented stem (102 pts, Zimmer), CADCAM (140 pts, Stanmore), and HAC Furlong (96 pts, JRI). There were a variety of other stems, including Exeter and Pro-femur. 48 patients had revision of socket only. Functional outcome was assessed by three questionnaires: the Oxford Hip Questionnaire (12 best function-60 worst), the Harris Hip Score (100 best to 0 worst), and the WOMAC Hip Score (0 best-96 worst). Patients filled in these questionnaires at every postoperative follow-up clinic. These were compared with the pre-operative scores obtained from questionnaires which the patients completed retrospectively. Mean follow up questionnaire times were 76.5 months postoperatively for primary arthroplasties, and 70.6 months for the revision arthroplasties. For primary arthroplasty mean scores improved from 40.8 pre-operatively to 16.4 post-operatively (Oxford), 43.9 to 92.9 (Harris), and 51.8 to 9.4 (WOMAC) (all p< 0.05). For revision arthroplasty mean scores improved from 39.1, 41.7, and 49.3 pre-operatively to 19.6, 88.0, and 12.5 (all p< 0.05). No patients required re-operation for loosening, one patient dislocated at day 5. We can conclude that the Trilogy acetabular component is a versatile acetabular implant which can be used with a wide range of femoral components, both in primary and revision Total Hip Arthroplasty, with successful functional outcome scores greater than 5 years after implantation