Abstract
Introduction
Solid or cystic pseudotumour is a potentially destructive complication of metal on metal (MoM) couples, usually needing revision surgery. However, complete clearance of the pseudotumour is unlikely at times. This prospective case-controlled study reports cases which had recurrence after revision surgery for pseudotumour related to metal on metal hip couples.
Methods
A total of 37 hips (33 MoM hip resurfacing and four big head MoM total hip arthroplasty (THA)) were revised for pseudotumour during the last 10 years. The patient demographics, time to revision, cup orientation, operative and histological findings were recorded for this cohort. Patients were divided into two groups - group R (needing re-revision for disease progression) and group C (control - no evidence of disease progression). Oxford hip scores (OHS, 0–48, 48 best outcome) were used to assess clinical outcome. The diagnosis of disease progression was based on recurrence of clinical symptoms, cross-sectional imaging, operative and histological findings.
Results
Nine of 37 (24%) patients identified with worsening symptoms, eight underwent further re-revision surgery while one is awaiting revision surgery (group R). All patients were females and the mean time to initial revision in group R was 34 months (SD 21.8) and 60.5 months in group C (SD 27.5, p< 0.01). The mean cup abduction angle and anteversion in group R were 480 (SD 9.3) and 5.10 (SD 5.0), and 500 (SD 8.7) and 14.50 (SD 8.5) respectively. Re-revision surgery confirmed disease progression in all cases. Oxford hip score was significantly worse in group R 19 (SD 8.0) as compared to group C 33 (SD14.2) (p=0.03).
Discussion
This study demonstrates that solid pseudotumour can progress following initial revision. This is likely to be an ongoing reaction to retained metal debris despite adequate clearance. All patients revised for pseudotumour should be monitored using early ultrasound or MRI.
