Abstract
Pseudotumours have recently been reported in non-metal-on-metal total hip replacements (non-MoM THRs), however the magnitude and risk factors for this complication are unknown, as is the outcome of its treatment.
3340 primary THR undergoing revision for pseudotumour between 2008 and 2015 were identified in the National Joint Registry for England and Wales. 7.5% (n=249) of these pseudotumour revisions, had non-MoM bearing surfaces. The risk of revision for pseudotumour in non-MoM hips was 0.032% (249/789,397; 95% CI 0.028%–0.036%). The risk of pseudotumour revision was 2.35 times (95% CI 1.76–3.11) higher in ceramic-on-ceramic compared with hard-on-soft bearings, and 2.80 times (95% CI 1.74–4.36) higher in 36mm metal-on-polyethylene bearings compared to 28mm and 32mm metal-on-polyethylene bearings.
The outcome of revision for pseudotumour non-MoM hips was studied in 185 hips. 13.5% (n=25) had re-revisions at a mean of 1.2 years (range 0.1–3.1 years). Infection (32%), dislocation/subluxation (24%), and aseptic loosening (24%) were the commonest indications for re-revision. The 4-year survival rate was 83.8% (95% CI=76.7%–88.9%). Multiple revision indications (Hazard Ratio (HR)=2.78; 95% CI=1.03–7.49) and incomplete revision procedures (HR=5.76; 95% CI=1.28–25.9) increased the risk of re-revision
Although the overall risk of revision for pseudotumour in non-MoM THRs is low, the risk is increasing and is significantly higher in ceramic-on-ceramic and large head metal-on-polyethylene THR. These revisions have a high early failure rate.
