Clinical comment

The theoretical advantages of hip resurfacing must be demonstrated clinically through improved patient‐reported outcomes over THA (the current gold standard treatment) before widespread adoption is advocated.

Available literature and quality of the evidence

The majority of studies comparing patient reported outcomes between hip resurfacing and replacement surgery are case‐controls (level III) and report mixed results.⁴–¹¹ Nonetheless, there are four randomized controlled trials (RCTs) (level I) that compare clinical outcomes between hip resurfacing and replacement in relatively young and active patients. Two of these studies compare resurfacing with contemporary nonmetal‐on‐metal total hips,¹²,¹³ while the other two studies compare hip resurfacing with metal‐on‐metal THA.¹⁴,¹⁵

Findings

Focusing our discussion on the available level I evidence, there are two studies that compare hip resurfacing to THA with nonmetal‐on‐metal articulations. Costa et al. randomized 126 patients to receive either hip arthroplasty or resurfacing and reported similar Oxford Hip Scores (mean 38.2, 95% confidence interval [CI]: 35.3–41.0 vs 40.4, 95% CI: 37.9–42.9, respectively) and Harris Hip Scores (HHS; 82.3, 95% CI: 77.2–87.5 vs 88.4, 95% CI: 84.4–92.4, respectively) at 12‐month follow‐up.¹³ Strengths of this study include: adherence to a standardized preoperative assessment and perioperative care pathway for both groups, blinded measurement and assessment of outcomes, low cross‐over rates, excellent follow‐up (95%), and the fact that each patient had the allocated surgery according to the preferred technique of the operating surgeon. While clinical outcomes were similar between the two groups, they were limited to a one‐year follow‐up and may not reflect long‐term results between these two interventions. More recently, Haddad and colleagues reported on the long‐term results of their randomized trial involving 80 patients treated with either cementless THA or a Birmingham hip resurfacing.¹² Similar to Costa’s study, there was no difference in mean Oxford Hip Scores (37.9 ± 0.6 for replacement vs 40.1 ± 0.4 for resurfacing) nor HHS (96 ± 4.2 for replacement vs 97.1 ± 5.1 for resurfacing) at mean follow‐up of 12 years. Nonetheless, the authors report that a higher proportion of patients with a hip resurfacing were running and involved in sport and heavy manual labor after 10 years. The authors suggest an advantageous return to high‐level activity in resurfaced patients, perhaps below the sensitivity threshold of the Oxford and HHS. It must be noted, however, that there was a large amount of crossover in this study where only 24 of the 80 patients actually underwent the treatment to which they were randomized.

There are two RCTs comparing hip resurfacing to metal‐on‐metal THA. Vendittoli et al. randomized 209 hips to undergo resurfacing or replacement with a metal‐on‐metal bearing using a 28 mm head.¹⁴ They demonstrated a marginally better Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score in the resurfacing group (5.7 ± 8.6 for resurfacing vs 9 ± 11.0 for THA) at two‐year follow‐up. Garbuz et al. randomized 107 patients to either hip resurfacing or a large head metal‐on‐metal hip arthroplasty.¹⁵ Exceedingly high metal ion levels discovered in the hip arthroplasty group raised concern for trunnionosis and eventually led to the premature termination of the trial. Similar early failures of large head metal‐on‐metal total hips have been identified from multiple studies and registries leading to the widespread abandonment of these implants.¹⁶

Resolution of clinical scenario

• Current level I evidence does not support a clear clinical benefit in patient‐reported outcome measures following hip resurfacing in comparison to THA.
  
• Nonetheless, hip resurfacing as compared to THA may offer advantageous long‐term function with respect to specific high‐demand actives such as participation in running sports and manual labor.