Hip arthroplasty with the articular surface replacement (ASR) system: survivorship analysis and functional outcomes

Background

The articular surface replacement (ASR) hip resurfacing system, now withdrawn, has the highest all-cause revision rate (24.2 % at 7 years) compared with other resurfacing brands. We present our experience with the ASR articulation and the implant recall process.

Methods

We reviewed the medical records and examined all 55 patients (57 hips) who had THA by the senior author between March 2005 and November 2008. We recorded the Oxford Hip scores, metal ion levels, need for revision, the indication for revision, and the intra-operative findings. Radiographs were performed at the time of recall to detect component failure.

Results

Survival at 5 years with revision for any reason as the endpoint was 85.1 % for all patients. At the time of recall, 10 (17.5 %) of fifty-seven THAs were already revised. Four (40 %) of the ten revisions were performed within 1 month of the operation due to a periprosthetic fracture. Three other revisions were due to avascular necrosis at a mean time of 3.6 years. One patient was revised due to infection. The two remaining revisions were due to ongoing groin pain, in one of whom the cup was found to be loose.

Conclusions

Our data indicate an overall high revision rate, comparable with recently published studies. Even though most of our revisions were attributed to causes that are not specific to the metal-on-metal articulation, we do expect to find more cases of failures in the future. Therefore, continued close clinical surveillance and laboratory monitoring of these patients is warranted.