Forty-six studies were included in the review (6,189 participants): 10 RCTs (1,313 participants), 28 prospective observational studies (4,009 participants) and eight retrospective studies (867 participants). Nine studies described an adequate method of randomisation. Assessors were blinded in four studies and patients were blinded in two. Groups were comparable at baseline in 25 studies. Intention-to-treat analyses were used in 16 studies. Overall quality scores were zero to 3 in one study, 4 to 7 in 16 studies, 8 to 11 in 23 studies and 12 to 15 in five studies. Mean follow-up was 25 months.
Functional outcomes: Hip resurfacing was associated with better functional outcomes than total hip arthroplasty, including WOMAC score (MD -2.4, 95% CI -3.9 to -0.9), range of motion component of Harris hip score (MD -0.05, 95% CI -0.1 to -0.03) and overall Harris hip score (MD 2.5, 95% CI 1.2 to 3.8). Total hip arthroplasty was associated with greater difficulty in undertaking a step test task than hip resurfacing (RR 0.3, 95% CI 0.1 to 0.6). Overall Harris hip score was associated with some heterogeneity (Ι²=28%). There was no significant difference between treatment groups in terms of the Merle d'Aubigne index, Oxford hip score or hop test results.
Radiological outcomes: There was a significantly greater number of incidences of heterotopic ossification (RR 1.6, 95% CI 1.2 to 2.1) with hip resurfacing compared with total hip arthroplasty; statistical heterogeneity was not present. There was no significant difference between groups in acetabular or femoral offset, leg length, cup height or presence of specific acetabular or femoral radiolucency.
Complications: There was a significantly greater number of incidences of aseptic loosening (RR 3.1, 95% CI 1.1 to 8.5; 10 studies) and revision surgery (RR 1.7, 95% CI 1.2 to 2.5; 18 studies) with hip resurfacing than with total hip arthroplasty. These outcomes were associated with statistical heterogeneity (Ι²=52% and Ι²=30%). Hip resurfacing was associated with reduced incidence of dislocation (RR 0.2, 95% CI 0.1 to 0.5) and was not associated with heterogeneity. There was no significant difference between groups in other complications.
The funnel plot did not provide evidence of publication bias.
Further results were reported for other clinical outcomes and quality of life.