Long-term outcomes of small head metal-on-metal compared to ceramic-on-polyethylene primary total hip arthroplasty: a registry-based cohort study
摘要
We aimed to compare the long-term outcomes of small-head (28 mm) metal-on-metal (MoM) total hip arthroplasty (THA) to ceramic-on-polyethylene (CoP) THA using the same cup.
MethodsAll primary elective MoM and CoP THAs performed 1998–2011 were prospectively included in a local registry. Patients were followed until 31 December 2022. Outcomes were all-cause revision, complications and mortality. The uncemented Morscher 28 mm monobloc press-fit cup was used in all THAs.
ResultsOverall, 3257 THAs were included, 864 MoM (mean age 63) and 2393 CoP THAs (mean age 72). Mean follow-up of the cohort was 12.9 years (maximum 26.8 years). Revision for any cause was performed in 85 MoM and 79 CoP THAs. Cumulative incidence of all-cause revision at 20 years was 13.2% (95% CI 10.6 to 16.3) in MoM and 6.3% (95% CI 4.8 to 8.3) in CoP group. Adjusted hazard ratio for all-cause revision was 1.88 (95% CI 1.34 to 2.65) comparing MoM vs. CoP. Diagnoses at revision were mainly aseptic loosening (33%) and adverse local tissue reactions (33%) in MoM and aseptic loosening in CoP group (44%). The smoothed hazard function revealed the largest difference in instantaneous revision rate between three and 14 years postoperative. After that period no difference was observed.
ConclusionOverall, the cumulative risk of all-cause revision was almost twice as high in patients with a small head MoM as compared to a CoP THA over the 20-year period. However, most of the excess in revisions among MoM patients occurred between three and 14 years postoperative.