JOA - 2026-04-02 - Journal Article
Primary Total Hip Arthroplasty in Patients Who Have Morbid Obesity: A Propensity-Weighted Analysis of Dual Mobility and Standard Fixed-Bearing Implants.
Rudisill SS, Wu M, Weintraub MT, Grimm JA, Taunton MJ, Trousdale RT
Topics
Key Takeaway
In morbidly obese patients (BMI >40) undergoing primary THA, dual mobility implants achieved 100% five-year survivorship free from revision versus 96.8% for fixed-bearing constructs, with instability rates of 1.4% versus 0.6%.
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Summary
This study compared dual mobility versus fixed-bearing THA outcomes in patients with BMI >40 using a single-institution registry and propensity-weighted Kaplan-Meier analysis. Instability rates were low in both groups (1.4% DM vs. 0.6% fixed-bearing), and no revisions occurred in the DM cohort versus 4.6% in fixed-bearing (P=0.070). Propensity-weighted five-year survivorship free from revision was 100% for DM versus 96.8% for fixed-bearing, though differences did not reach statistical significance.
Key Limitation
The DM cohort (n=69) is too small to detect statistically significant differences in revision or instability rates, and the non-significant P-values (0.070) for revision and reoperation preclude definitive conclusions despite favorable point estimates.
Original Abstract
INTRODUCTION
Dual mobility (DM) bearings in total hip arthroplasty (THA) are designed to offer enhanced stability compared to traditional fixed-bearing constructs. However, the stability and durability of DM implants subjected to increased forces in the setting of morbid obesity remain underexplored. This study aimed to compare outcomes of DM and fixed-bearing constructs among morbidly obese patients following primary THA.
METHODS
We retrospectively reviewed patients who had a body mass index (BMI) greater than 40 and underwent primary THA between 2005 and 2022 using an institutional total joint registry. Those who had less than two years of follow-up and fixed-bearing head sizes less than 36 mm were excluded. There were 69 patients who received DM and 943 who received fixed-bearing implants that were included, achieving a mean follow-up of 6.0 years (range, 2.0 to 17.2). Dual mobility patients were older (mean age 63.0 versus 60.8 years, P = 0.032), more commonly women (73.9 versus 43.6%, P < 0.001), had higher BMI (mean 45.5 versus 44.5, P = 0.019), and more frequently underwent posterior approach THA (91.3 versus 59.9%, P < 0.001). Using propensity weighting to adjust for age, sex, BMI, surgical approach, surgical indication, spine disease, and spine surgery, Kaplan-Meier analyses assessed survivorship free from instability, revision, reoperation, and nonoperative complication.
RESULTS
Rates of instability were low in both DM and fixed-bearing groups (1.4 versus 0.6%). There were no revisions that occurred following DM THA, whereas 43 fixed-bearing constructs required revision (0 versus 4.6%, P = 0.070), including five (0.5%) for instability. Reoperation (1.4 versus 7.1%; P = 0.070) and nonoperative complication (5.8 versus 5.5%; P = 0.921) rates were similar. Propensity-weighted five-year survivorship free from instability, revision, reoperation, and nonoperative complication was 98.6, 100.0, 98.5, and 94.2% for DM and 99.4, 96.8, 94.1, and 92.3% for fixed-bearing implants.
CONCLUSION
In morbidly obese patients, DM implants demonstrated excellent five-year survivorship with outcomes comparable or slightly superior to fixed-bearing constructs. These findings suggest DM implants may provide stability without increasing complication rates in this high-risk population.