What’s New in Hip Replacement

Abstract

Implant Design and Related Outcomes Dual Mobility Dual-mobility cups do not reduce the revision risk for patients with acute femoral neck fracture, as concluded by Rogmark and Nauclér in an observational cohort of 2,242 patients with dual-mobility cups compared with a matched cohort of 6,726 patients treated with a conventional total hip implant1. The authors reported that, with implant revision surgery as the outcome, they “could not detect any differences between a total hip arthroplasty with a dual mobility cup and one with conventional bearing.” Outcomes were similar and independent of whether the implants were inserted via a direct lateral or posterior approach as well as for subgroup analyses of revision for dislocation and infection. The authors concluded that improvements in the care of patients with hip fracture are most likely to come from elsewhere in the care pathway and “not in design variations of contemporary orthopedic implants.” Cnudde et al. reported similar findings when they investigated patients with neurologic disease undergoing arthroplasty for femoral neck fracture2. Comparing hemiarthroplasty, conventional total hip arthroplasty (THA), and dual-mobility THA performed in 9,638 patients with conditions such as Alzheimer and Parkinson diseases, the authors found that there was an increased risk of dislocation when comparing hemiarthroplasty and THA with a <32-mm head but not with conventional THA with a 32-mm head (hazard ratio [HR], 1.54 [95% confidence interval (CI), 0.94 to 2.51]; p = 0.083) and THA with a dual-mobility implant (HR, 0.68 [95% CI, 0.26 to 1.84]; p = 0.451). Overall, the authors found no difference in the rate of reoperation or revision-free survival between any of the different prostheses or sizes of the femoral head. Cobalt-Chromium Using data from the National Joint Registry linked to U.K. National Health Service (NHS) English hospital inpatient episodes for 374,359 primary THAs, Deere et al. investigated 158,677 hips (42.4%) containing an implant with cobalt-chromium3. With a maximum 14.5-year follow-up (mean [and standard deviation], 5.1 ± 3.5 years [range, 1 day to 14.5 years]), the authors reported finding no association with any of the negative clinical outcomes studied, including all-cause mortality, heart outcomes, cancer, and neurodegenerative disorders. They stated that these data may provide reassurance to patients and clinicians that cobalt-chromium-containing primary THA implants are not associated with detectable adverse systemic effects. In a recent single-surgeon cohort, Gani et al. suggested that metal-on-metal hip resurfacing provides a durable intervention at a mean follow-up of 14.9 years (range, 9.3 to 19.1 years) for men receiving resurfacing implants with a head size of >46 mm4. The survivorship in this group was reported as 97.7%, with no metal ion level exceeding the accepted safe limits. However, the survivorship in female patients was 73.4%. The authors suggested that this high failure rate was closely related to head sizes of ≤46 mm. Patient Factors in Relation to Outcomes Socioeconomics In a recent investigation of 103,901 patients who underwent THA between 1995 and 2017 and were included in the Danish health registries, Edwards et al. concluded that socioeconomic inequality adversely influences the risk of infection after THA5. The cumulative incidence of any infection at 90 days was highest in patients who had the lowest amount of savings (1.3% [95% CI, 1.2% to 1.4%]) compared with those who had the highest amount of savings (0.7% [95% CI, 0.6% to 0.8%]), in patients who had the least education (1.1% [95% CI, 1.0% to 1.2%]) compared with those who had the highest education (0.7% [95% CI, 0.5% to 0.8%]), in patients who lived alone (1.5% [95% CI, 1.3% to 1.6%]) compared with those who did not (0.7% [95% CI, 0.7% to 0.8%]), and in patients who had the lowest income (1.6% [95% CI, 1.5% to 1.70%]) compared with those who had the highest income (0.4% [95% CI,