Table I.
The demographics of the patients in the study
| 40 hips in 39 patients | |
|---|---|
| Gender (M/F) (%) | 17 (42.5)/23 (57.5) |
| Mean age at primary (yrs) (range) | 52.8 (28.7 to 71.8) |
| Mean BMI (kg/m2) (range) | 29.9 (22.2 to 50.1) |
| Unilateral /bilateral metal-on-metal hips (%) | 23 (57.5)/17 (42.5) |
| Hip resurfacing design (%) | |
| Birmingham Hip Resurfacing (Smith & Nephew, Warwick, UK) | 21 (52.5) |
| Conserve Plus (Wright Medical, Memphis, Tennessee) | 15 (37.5) |
| Recap (Biomet, Bridgend, UK) | 3 (7.5) |
| Articular Surface Replacement (DePuy, Leeds, UK) | 1 (2.5) |
| Mean component sizes (mm) (range) | Femoral 47 (40 to 54) |
| Acetabular 53 (46 to 60) | |
| Acetabular component position (o) | |
| Mean inclination (range) | 49.6 (34.0 to 74.1) |
| Mean anteversion (range) | 10.8 (2.0 to 33.0) |
| Abnormal radiographic features (%) | |
| Acetabular loosening | 7 (17.5) |
| Femoral loosening | 2 (5.0) |
| Acetabular osteolysis | 9 (22.5) |
| Femoral osteolysis | 4 (10.0) |
| Femoral neck thinning | 14 (35.0) |
| Femoral neck fracture | 2 (5.0) |
| Heterotopic ossification | 3 (7.5) |
| Median blood metal ion concentration in µg/l (IQR) | Cobalt: 12.9 (2.4 to 61.5) |
| Chromium: 11.4 (3.4 to 54.9) | |
| Median pre-revision Oxford hip score (0 to 48 scale) (IQR) | 40.5 (27.0 to 47.0) |
| Mean pre-revision UCLA score (1 to 10 scale) (range) | 5.7 (2 to 9) |
| Pre-revision symptoms (%) | |
| Symptomatic | 34 (85) |
| Asymptomatic | 6 (15) |
| Systemic symptoms | 1 (2.5) |
| Mean time between US and MARS-MRI (days) (range) | 14.6 (0 to 90) |
| Mean time between imaging and revision (mths) (range) | 5.3 (0.06 to 12) |
| Mean time from primary to revision (yrs) (range) | 6.3 (1.7 to 11.5) |
| Mean age at revision (yrs) (range) | 59.1 (40.0 to 77.7) |
| Indication for revision (%) | |
| Pseudotumour | 33 (82.5) |
| ARMD | 5 (12.5) |
| Cup loosening | 1 (2.5) |
| Femoral loosening | 1 (2.5) |
BMI, body mass index; IQR, interquartile range; MARS-MRI, metal artefact reduction sequence MRI; US, ultrasound; UCLA, University of California, Los Angeles activity score; ARMD, adverse reaction to metal debris