Do survival rate and serum ion concentrations 10 years after metal-on-metal hip resurfacing provide evidence for continued use?

BACKGROUND: Owing to concerns attributable to problems associated with metal-on-metal bearing surfaces, current evidence for the use of hip resurfacing is unclear. Survival rates reported from registries and individual studies are controversial and the limited long-term studies do not conclusively allow one to judge whether hip resurfacing is still a reasonable alternative to conventional THA. QUESTIONS/PURPOSES: We asked whether the long-term survival rate of hip resurfacing is comparable to that of conventional THA and certain factors can be identified that influence serum ion concentration 10 years postoperatively. We specifically assessed (1) the 10-year survivorship in the whole cohort and in male and female patients, (2) serum concentrations of metal ions in patients with hip resurfacing who had not undergone revision surgery, and (3) potential influencing factors on the serum ion concentration. METHODS: We retrospectively reviewed our first 95 patients who had 100 hip resurfacings performed from 1998 to 2001. The median age of the patients at surgery was 52 years (range, 28-69 years); 49% were men. We assessed the survival rate (revision for any reason as the end point), radiographic changes, and serum ion concentrations for cobalt, chromium, and molybdenum. The correlations between serum ion concentration and patient-related factors (age, sex, BMI, activity) and implant-related factors (implant size, cup inclination, stem-shaft angle) were investigated. The minimum followup was 9.3 years (mean, 10 years; range, 9.3-10.5 years). RESULTS: The 10-year survivorship was 88% for the total cohort. The overall survival rate was greater in men (93%) than in women (84%). Median serum ion levels were 1.9 µg/L for chromium, 1.3 µg/L for cobalt, and 1.6 µg/L for molybdenum. Radiolucent lines around acetabular implants were observed in 4% and femoral neck thinning in 5%. CONCLUSIONS: Although our overall failure rate was greater than anticipated, the relatively low serum ion levels and no revisions for pseudotumors in young male patients up to 10 years postoperatively provide some evidence of the suitability of hip resurfacing in this subgroup. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.

Short-term outcome after posterior versus lateral surgical approach for total hip arthroplasty - A randomized clinical trial.

PURPOSE: Currently, total hip replacement (THR) is most commonly performed via a posterior or a direct lateral approach, but the impact of the latter on the invention's outcome has yet not been quantified. METHODS: We compared the short-term outcome of cementless THR using the both approaches in a prospective, randomized controlled trial. 60 patients with unilateral osteoarthritis were included. Outcome assessment was performed one day before surgery and one week, four weeks, six weeks and 12 weeks after surgery, respectively, using the Harris Hip score as primary objective. RESULTS: We found no significant difference in the intraindividual Harris Hip Score improvement at the pre- and three months post-operative assessments between both treatment groups (p = 0.115). However, Harris Hip scores and most functional and psychometric secondary endpoints showed a consistent tendency of a slightly better three months result in patients implanted via the posterior approach. In contrast a significant shorter operating time of the direct lateral approach was recorded (67 minutes versus 76 minutes, p<0.001). CONCLUSION: In our opinion this slightly better short-term functional outcome after posterior approach is not clinical relevant. However, to make definitive conclusions all clinical relevant factors (i.e. mid- to long-term function, satisfaction, complication rates and long-term survival) have to be taken into account. LEVEL OF EVIDENCE: I - therapeutic.

In vivo wear rate of the Birmingham Hip Resurfacing arthroplasty. A review of 10 retrieved components.

The wear of 8 femoral and 2 acetabular components of the Birmingham Hip Resurfacing (Midland Medical Technologies Ltd, Birmingham, UK) was measured using a coordinate measuring machine (CMM5; SIP, Geneva, Switzerland). After a median in situ time of 13 months, measurements of the Birmingham Hip Resurfacing femoral heads revealed a median volumetric wear of 2.9 mm(3). In one case with a cup abduction angle of 70 degrees , a significantly higher wear of 17.8 mm(3) was found. The 2 acetabular components showed volumetric wear of 5.4 and 27.6 mm(3) after 14 and 15 months in vivo. The wear rates of the investigated femoral components were somewhat, but not significantly, higher than the previously investigated 28-mm Metasul heads (median, 0.8 mm(3); Zimmer GmbH, Winterthur, Switzerland).

Birmingham Hip Resurfacing arthroplasty: short-term clinical and radiographic outcome.

BACKGROUND: Aim of our study was to evaluate the clinical and radiographic outcome of the first 300 consecutively implanted Birmingham Hip Resurfacing arthroplasties (BHR) in our department. METHODS: 300 BHR arthroplasties were performed in 263 patients until May 2003. Primary clinical endpoints of the investigation were the implant survival and the total Harris hip score, assessed at the last examination. RESULTS: At a median follow-up time of 24 months the Kaplan/Meier survivor estimate was 98%. 6 implant revisions were performed due to infection (2), malposition (1), femoral neck fracture (1), primary unstable cup (1) and chronic pain (1), respectively. The median Harris hip score improved from 51 points to 96 points at last follow-up. No hip showed radiographic signs of aseptic implant loosening. CONCLUSIONS: The preliminary experience with the BHR for the younger adult requiring hip arthroplasty is encouraging, but has to be reproduced in the long-term.

Serum metal ion exposure after total knee arthroplasty.

All metal implants release metal ions because of corrosion. This has been studied and debated, especially in metal-on-metal total hip arthroplasties. Total knee arthroplasty implants have large metal surface areas and therefore substantial potential for corrosion. We determined changes in serum levels of metal ions in 41 patients after cemented unconstrained total knee arthroplasty without patellar resurfacing, 18 with unilateral total knee arthroplasty (median, 66 months after surgery) and 23 patients with bilateral total knee arthroplasties (75 and 50 months after first and second surgeries, respectively). Serum concentrations of chromium, cobalt, and molybdenum were analyzed and related to the number of total knee arthroplasties and compared with those of 130 control patients without implants. The median chromium, cobalt, and molybdenum concentrations were 0.92, 3.28, and 2.55 microg/L, respectively, in the unilateral total knee arthroplasty sample and 0.98, 4.28, and 2.40 microg/L, respectively, in the bilateral total knee arthroplasty sample. We observed no difference between the serum levels in patients with unilateral and bilateral arthroplasties, but the serum levels of chromium and cobalt of both study groups were greater than those of the control group (less than 0.25 microg/L). The patients who had total knee arthroplasty had molybdenum profiles that were similar to those of the control group (median, 2.11 microg/L).

Neo-capsule tissue reactions in metal-on-metal hip arthroplasty.

BACKGROUND: Modern-generation metal-on-metal articulations have a high wear resistance and may therefore be able to improve the long-term performance of artificial joints. However, the biological effects are still under debate. This study was undertaken to review the histopathological changes in neo-capsule tissues of different metal-on-metal hip arthroplasties. METHODS: Neo-capsule tissue samples from 46 hips with modern second-generation metal-on-metal articulations (39 hip resurfacings and 7 non-cemented total hip replacements) with a variety of failure mechanisms were examined histopathologically and immunohistochemically. RESULTS: A distinct lymphocytic infiltration was found in all cases with in situ times of more than 7 months, consisting of CD20-positive B-lymphocytes and CD3-positive T-lymphocytes and sometimes thinly distributed CD138-positive plasma cells without dominant T-cell or plasma cell infiltrates. INTERPRETATION: This distinct lymphocytic infiltration has not been reported in tissue analyses of metal- or ceramic-on-polyethylene hip replacements, and may therefore be considered to be a characteristic histological pattern of tissue reactions on metal particles and/or ions around metal-on-metal bearings.

Exposure to chromium, cobalt and molybdenum from metal-on-metal total hip replacement and hip resurfacing arthroplasty.

BACKGROUND: All metal implants--and metal-on-metal bearings in particular--corrode and cause a release of metal ions. Because cobalt and chromium have been shown to be carcinogenic and mutagenic in human and animal models, systemic toxicity and cancer risk are considered to be possible disadvantages of the metal-on-metal articulation. This study was designed to investigate the serum concentration profiles of chromium, cobalt and molybdenum after implantation of a Birmingham hip resurfacing arthroplasty (BHR) and a cementless total hip replacement with a 28-mm Metasul articulation (MTHR), over the first 2 years after implantation. METHODS: We analyzed profiles of metal ion serum levels in 111 patients implanted with a BHR, in 74 patients implanted with an MTHR, and in 130 implant-free probands control subjects using atomic absorption spectrophotometry. RESULTS: Chromium and cobalt concentrations (in microg/L) of all BHR and MTHR patients differed significantly from those of control subjects (chromium: < 0.25; cobalt: 0.25). The median chromium and cobalt concentrations in BHR patients had increased to 5.1 and 4.3 microg/L 2 years after surgery. Concentrations in BHR patient exceeded those in the unilateral MTHR patients. Molybdenum serum concentrations hardly changed over time in either group and were not significantly different from the concentrations seen in the control subjects. INTERPRETATION: During the first 2 years after surgery, the Birmingham hip resurfacing arthroplasty leads to a significantly greater increase in serum chromium and cobalt levels than the 28-mm metal-on-metal MTHR. Observation of patients over a longer period will be necessary in order to evaluate any chronic adverse effects to the system due to elevated chromium and cobalt serum concentrations.