Comparative assessment of implantable hip devices with different bearing surfaces: systematic appraisal of evidence

Abstract

Objective: To determine comparative safety and effectiveness of combinations of bearing surfaces of hip implants.

Design: Systematic review of clinical trials, observational studies, and registries.

Data sources: Medline, Embase, Cochrane Controlled Trials Register, reference lists of articles, annual reports of major registries, summaries of safety and effectiveness for pre-market application and mandated post-market studies at the United States Food and Drug Administration.

Study selection: Criteria for inclusion were comparative studies in adults reporting information for various combinations of bearings (such as metal on metal and ceramic on ceramic). Data search, abstraction, and analyses were independently performed and confirmed by at least two authors. Qualitative data syntheses were performed.

Results: There were 3139 patients and 3404 hips enrolled in 18 comparative studies and over 830 000 operations in national registries. The mean age range in the trials was 42-71, and 26-88% were women. Disease specific functional outcomes and general quality of life scores were no different or they favoured patients receiving metal on polyethylene rather than metal on metal in the trials. While one clinical study reported fewer dislocations associated with metal on metal implants, in the three largest national registries there was evidence of higher rates of implant revision associated with metal on metal implants compared with metal on polyethylene. One trial reported fewer revisions with ceramic on ceramic compared with metal on polyethylene implants, but data from national registries did not support this finding.

Conclusions: There is limited evidence regarding comparative effectiveness of various hip implant bearings. Results do not indicate any advantage for metal on metal or ceramic on ceramic implants compared with traditional metal on polyethylene or ceramic on polyethylene bearings.

Fig 1 Harris hip scores at two years (top) after hip implants with metal on metal versus metal on polyethylene bearings. Zijlstra et al measured score at both 24 months and 60 months

Fig 2 Harris hip score beyond two years after hip implants with metal on metal versus metal on polyethylene or ceramic on polyethylene bearings. Jacobs et al assessed score at mean 43 months while Dorr et al assessed score at 60 months. Zijlstra et al measured score at both 24 months and 60 months. SD of mean imputed for Jacobs et al and sensitivity analyses performed; varying estimates of SD did not change overall estimate of effect

Fig 3 Qualitative evidence reported in six national data sources/registries (Australia, New Zealand, England and Wales, Italy (Emilia-Romagna), Kaiser and CMS databases)