Table 1.
Summary of the study cohort
| Total cohort for analyses(48 hips in 40 patients) | ||
|---|---|---|
| Sex | Female Male |
26 (54%) 22 (46%) |
| Age at first ultrasound scan | Mean (range) in years | 61.9 (39.0–82.2) |
| Time between primary hip arthroplasty and first ultrasound scan | Mean (range) in years | 5.0 (0.5–11.7) |
| Time interval between repeat ultrasound scans | Mean (range) in years | 1.1 (0.2–3.3) |
| Indication for repeat ultrasound examination | Under surveillance and/or patient refused revision Asymptomatic initially, then developed symptoms Remains asymptomatic but concentration of metal ions in blood increasing |
34 (71%) 8 (17%) 6 (13%) |
| Implant type and design |
Total hip arthroplasty > Synergy/modular head (Smith & Nephew, Warwick, UK) > Corail-Pinnacle (DePuy International Limited, Leeds, UK) > Caparo Amoda (Comis Orthopaedics, Birmingham, UK) > Other Hip resurfacing > Birmingham Hip Resurfacing (Smith & Nephew, Warwick, UK) > Other |
27 (56%) 13 8 2 4 21 (44%) 19 2 |
| Initial inclination of the acetabular component | Mean (range) in degrees | 44.9 (25.3–66.5) |
| Number of patients with unilateral or bilateral metal-on-metal hips | Unilateral Bilateral* |
22 (46%) 26 (54%) |
| Blood metal ion concentration | Median (interquartile range) in µg/l | Cobalt = 7.6 (2.9–10.9) Chromium = 4.8 (2.1–6.3) |
| Oxford hip score | Median (interquartile range) > % scale > 0 to 48 scale |
43.8 (25.0–60.4) 27.0 (19.0–36.0) |
| Hips with pseudotumours revised after repeat ultrasound scan | Adverse reaction to metal debris | 15 of 26 (58%) |
*
Of 26 patients with bilateral metal-on-metal hip bearings, 8 patients required repeat ultrasound imaging of both hips (therefore, these 16 hips have been included in the study). The remaining 18 patients with bilateral metal-on-metal hip bearings did not have repeated imaging of their contralateral metal-on-metal hip bearing (therefore, these contralateral hips were not eligible for study inclusion).