Abstract
Introduction
Complication and revision rates have shown to be high for all metal-on-metal (MoM) bearings, especially for the ASR Hip System (ASR hip resurfacing arthroplasty (HRA) and ASR XL total hip arthroplasty (THA)). This prompted the global recall of the ASR Hip System in 2010. Many studies have previously explored the association between female gender and revision surgery MoM HRA implants; yet less research has been dedicated to exploring this relationship in MoM THA.
The first purpose of this study was to assess the associations between gender and implant survival, as well as adverse local tissue reaction (ALTR), in patients with MoM THA. Secondly, we sought to report the differences between genders in metal ion levels and patient reported outcome measures (PROMs) in patients with MoM THA.
Methods
The study population consisted of 729 ASR XL THA patients (820 hips) enrolled from September 2012 to June 2015 in a multicenter follow-up study at a mean of 6.4 (3–11) years from index surgery. The mean age at the time of index surgery was 60 (22–95) years and 338 were women (46%). All patients enrolled had complete patient and surgical demographic information, blood metal ion levels and PROMs obtained within 6 months, and a valid AP pelvis radiograph dating a maximum of 2 years prior to consent. Blood metal ion levels and PROMs were then obtained annually after enrollment. A sub-set of patients from a single center had annual metal artifact reduction sequence (MARS) MRI performed and were analyzed for the presence of moderate-to-severe ALTR.
Results
Eighty-nine hips (11%) were revised during the study period. Forty-five of the 338 men underwent revision (13%), and 44 of the 391 women underwent revision (11%). The mean time from index surgery to revision was 7 years for both males and females. After controlling for confounding variables, the only variables found to be associated with revision surgery in patients with unilateral THA were VAS pain (hazard ratio [HR], 1.28; p < 0.001) and elevated cobalt metal ion levels (HR, 1.02; p < 0.001). Patients with bilateral arthroplasties with low HHS (HR, 0.96; p < 0.001) and high cobalt levels (HR, 1.02; p < 0.001) were at increased risk for revision. Moderate-to-severe ALTRs were identified in 48 of the 133 hips with MARS MRI (36%), 17 of which were in females (30% of females) and 31 in males (40% of males). The only variables found to be associated with the presence of moderate-to-severe ALTR were abduction angle (HR, 0.92; p = 0.004) and Corail AMT stem type (HR, 2.31; p = 0.012). Female gender did not influence the risk of revision or ALTR. Chromium concentrations were greater in female patients than males, while cobalt levels were similar between genders. Males reported higher HHS, EQ-5D and UCLA scores than females.
Discussion and Conclusion
Both males and females with MoM THA implants should be followed with equal vigilance as gender does not appear to be associated with poor outcomes, such as revision surgery and presence of ALTR.
