Ten years on: increased metal ion levels in a cohort of patients who underwent uncemented metal-on-polyethylene total hip arthroplasty.

AIMS: We have previously demonstrated raised cobalt and chromium levels in patients with larger diameter femoral heads, following metal-on-polyethylene uncemented total hip arthroplasty. Further data have been collected, to see whether these associations have altered with time and to determine the long-term implications for these patients and our practice. METHODS: Patients from our previous study who underwent Trident-Accolade primary total hip arthroplasties using a metal-on-polyethylene bearing in 2009 were reviewed. Patients were invited to have their cobalt and chromium levels retested, and were provided an Oxford Hip Score. Serum ion levels were then compared between groups (28 mm, 36 mm, and 40 mm heads) and over time. RESULTS: Metal ion levels were repeated in 33 patients. When comparing the results of serum metal ion levels over time, regardless of head size, there was a significant increase in both cobalt and chromium levels (p < 0.001). Two patients with larger head sizes had undergone revision arthroplasty with evidence of trunnion damage at surgery. Two patients within the 40 mm subgroup had metal ion levels above the MHRA (Medicines and Healthcare Products Regulatory Agency) threshold for detailed investigation. The increase in cobalt and chromium, when comparing the 36 mm and 40 mm groups with those of the 28 mm group, was not significant (36 mm vs 28 mm; p = 0.092/p = 0.191; 40 mm vs 28 mm; p = 0.200/p = 0.091, respectively). There was no difference, between femoral head sizes, when comparing outcome as measured by the Oxford Hip Score. CONCLUSION: This study shows an increase in cobalt and chromium levels over time for all modular femoral head sizes in patients with metal-on-polyethylene bearings, with two patients demonstrating ion levels above the MHRA threshold for failure, and a further two patients requiring revision surgery. These results may have clinical implications regarding longer term follow-up of patients and future implant choice, particularly among younger patients. Cite this article: Bone Joint J 2020;102-B(7):832-837.

10-year results of the Birmingham Hip Resurfacing: a non-designer case series.

INTRODUCTION: Recent controversies surrounding metal-on-metal (MoM) hip resurfacing has led to a substantial decline in its use. Despite this, there is good evidence to support the use of specific implants in select patients. PATIENTS AND METHODS: A retrospective analysis of Birmingham Hip Resurfacing (BHR) patients with a minimum of 10 years follow-up was performed. Functional scoring was performed with the Oxford Hip Score (OHS) and failure was defined as revision for any cause. 111 patients underwent 121 BHR procedures. All patients had a minimum follow-up of 10 years. 70 patients (63%) were male. Mean patient age at surgery was 52.5 years (male 53.9 years, female 48.8 years). RESULTS: Overall survival at 10 years was 91% (97% male, 80% female). There was a statistically significant improvement in OHS postoperatively which remains at 10-year follow-up (p = <0.05). There was no significant difference in scores between the male and female groups. Revisions were most often in patients with smaller component sizes but this was not found to be statistically significant. CONCLUSIONS: Our results reflect that of the wider literature in that good outcomes can be obtained with this implant in a select group of patients and results are comparable to that of conventional hip arthroplasty in patients of a similar age.

Blood metal ions after hybrid metal-on-polyethylene Exeter-Trident total hip replacement.

BACKGROUND: Metal-on-metal total hip replacements (THRs) with large femoral heads have been associated with elevated levels of cobalt (Co) and chromium (Cr), which have been attributed to high levels of wear at the articular surface. Our unit recently published data showing a significant increase in the mean levels of Co ions in patients with a 36-mm diameter femoral head with the metal-on-polyethylene Trident-Accolade system. The aim of this study is to assess the levels of Co and Cr in the Exeter-Trident hybrid system, as similar findings would raise concern over the V40 taper trunnion. MATERIALS AND METHODS: The study included 83 patients (45 male and 38 female with a mean age of 75.6 years) who received Exeter-Trident hybrid metal-on-polyethylene THRs. The patients were then divided into two groups according to the diameter of the femoral head used-38 patients in the 28-mm group (control), and 45 in the 36-mm (experimental) group. Serum levels of blood Co and Cr were analysed for all recruited patients. RESULTS: In the control group (28-mm femoral head) all Co and Cr values were normal (under the abnormal threshold), as were the experimental group (36-mm femoral head). The data values were below <10 nmol and <40 nmol for Co and Cr, respectively. CONCLUSION: Since the National Joint Registry (NJR) states that the Exeter femoral stem is the commonest cemented femoral stem prosthesis used in the UK, we found it imperative that these results are documented given the corresponding findings in the Trident-Accolade system in our previous study. This study provides relative reassurance that the issue does not lie with the V40 taper trunnion, but raises suspicion that the issue may be with the titanium Accolade stem with large diameter femoral heads.

The Mayo Conservative Hip: experience from a district general hospital.

The Mayo Conservative Hip femoral prosthesis has been designed to optimise proximal femoral loading as well as preserving proximal femoral bone stock. Between October 2003 and May 2006, 42 patients (49 hips) underwent total hip replacement (THR) using the Mayo Conservative Hip femoral component. The mean age at operation was 57.8 years (range 44 to 74) and the mean clinical follow up was 3.1 years (range 2.3 to 4.7 years). The aim of our study was to review the short term results of this unorthodox femoral component. We found that 18% degrees of stems were malaligned >or= 5 degrees and the prevalence of intra-operative femoral fracture was 4%. We feel this prosthesis is difficult to implant and has an unacceptable fracture rate.