A review of hip resurfacings revised for unexplained pain.

Background: Adverse reaction to metal debris (ARMD) has come to prominence as a mode of failure for metal-on-metal hip resurfacings. These patients frequently present with unexplained groin pain.

Aims: 1) To review all metal-on-metal hip resurfacings revised for unexplained pain seeking evidence for ARMD; 2) To determine the clinical outcome following revision arthroplasty.

Methods: The hospital database was searched (1997-2009) to identify all cases of Birmingham Hip Resurfacings (BHRs) revised for unexplained pain. ARMD was diagnosed using specific clinical, radiological, and histopathological criteria. Postoperatively all patients were assessed in clinic and completed an Oxford Hip Score (OHS) questionnaire.

Results: Of 3076 BHRs implanted 149 were revised. Of these, 20 BHRs in 17 patients were revised for unexplained pain (mean age at BHR 50.5 yr; 55% female). Unexplained pain requiring revision had a prevalence of 0.65% of all hip resurfacings performed (20/3076). ARMD was the mode of failure in 50% (n = 10). Common features observed in ARMD patients included hip-joint effusions, femoral neck thinning, intraoperative macroscopic granulomas, and lymphocytic infiltrates on histopathological examination. No ARMD patients had macroscopic soft-tissue destruction. A range of mechanical causes were responsible for the remaining failures. At a mean 3.6 year follow-up (range 1.1-8.0) one ARMD patient experienced a dislocation. There were no further complications or need for surgical re-intervention. Median OHS for the cohort was 25.0%.

Conclusions: Hip resurfacings revised for unexplained pain comprise a diverse group of conditions with ARMD being the commonest. ARMD probably contains subgroups yet to be defined, some of which may be related to mechanical rather than immunological factors.