gms | German Medical Science

Objectives: After primarily enthusiastic re-invention of metal-on-metal (MoM) hip resurfacing as a bone-preserving procedure, increasing concern has been expressed in recent years about the potential of adverse reactions to metal debris (ARMD). Although numerous case reports and even some large series of metal-related adverse events are available, most of them address this complication in not well-performing implants which have been recalled from the market. There is a lack of systematically performed investigations with appropriate imaging techniques in cohorts with well-functioning devices. Aim of our study is therefore to evaluate the true medium-term incidence of ARMD with MRI and metal ion analysis in an unselected group of patients after Durom (TM) Hip Resurfacing.

Methods: Between October 2003 and March 2007 we performed 136 MoM hip resurfacing procedures with DuromTM in 123 consecutive patients (mean age 56.22±7.8; 23.6% females). After a mean follow up time of 8.4±0.9 (5.9-10.5) years we could obtain full clinical and radiographic (conventional x-ray and Metal-Artefact-Reduction-Sequence/ MARS-MRI) as well as metal ion investigation (cobalt/chromium levels in serum and whole blood) in 104 hip replacements (76.5%). 5 patients had already undergone revision arthroplasty, 3 patients had to be excluded due to decease or inability to participate at the follow-up examination due to medical reasons. Another 16 patients could not participate at the clinical examination due to long travelling distance, but questionnaire-based information about the implant function could be obtained.

Results and Conclusion: An overall number of 17 (16.3%) MRI-investigated hips showed ARMD with any degree of severity. ARMD of >=2cm diameter could only be detected in 10 hips (9.6%). The mean serum level of chromium was 2.69±2.06 (min-max: <0.5-15) ug/l. and the mean serum level of cobalt was 1.05±1.55 (min-max: <0.5-15.14) ug/l. Only 7 out of 17 patients (41.2%) with ARMD showed serum cobalt or chromium levels of more than 2ug/l. 2 out 17 patients had higher serum levels than 10ug/l (11.8%). Two clinically well-functioning patients with substantial ARMD had to be revised as a result of this follow-up study due to extremely elevated metal ions.

Only a few cases of ARMD were associated with marked elevation of serum chromium and cobalt levels. By following the European Expert Consensus recommendations (2012), 58.8% of the patients with ARMD diagnosed with MRI would not have been detected. Future investigations have to evaluate the relevance of these findings.