Elevated BMI may not increase risks of dislocation, revision after THA
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Key takeaways:
- Elevated BMI had no association with increased risks of dislocation or revision after total hip arthroplasty.
- Dislocation and revision were similar between patients with high BMI vs. normal BMI.
Published results showed patients with a higher BMI had no differences in rates of dislocation or revision at 1 year to 2 years after primary total hip arthroplasty compared with patients with a normal BMI.
“When controlling for established risk factors for instability, obesity in isolation did not impact dislocation risk,” study co-author Alexander J. Acuña, MD, told Healio. “This suggests that surgeons should consider patients’ individual dislocation risk profiles rather than strict BMI cut-offs when indicating patients for THA and making decisions regarding implants or approach. This should include each patient’s unique comorbidity burden, surgical history, activity level and anatomy,” he added.
Acuña and colleagues from Rush University Medical Center retrospectively analyzed data from 8,931 patients who underwent elective primary THA for osteoarthritis between 2010 and 2022.
Researchers categorized patients into cohorts based on whether they had a BMI of 25 kg/m2 to 29.9 kg/m2 (n=2,313); 30 kg/m2 to 34.9 kg/m2 (n= 2,230); 35 kg/m2 to 39.9 kg/m2 (n=1,852); 40 kg/m2 to 44.9 kg/m2 (n=1,450); 45 kg/m2 to 49.9 kg/m2 (n=752); or 50 kg/m2 to 59.9 kg/m2 (n=334). Cohorts were matched 1:1 with a control cohort of patients with a normal BMI of 20 kg/m2 to 24.9 kg/m2.
According to the study, outcome measures included dislocation rates at 30 days, 90 days, 6 months, 1 year and 2 years, as well as revision rates at 1 year and 2 years.
Overall, Acuña and colleagues found no significant differences in dislocation rates or revision rates between patients with elevated BMI vs. patients with normal BMI at all postoperative follow-up intervals.
They noted dislocation rates increased from 0.73% for patients with BMI between 25 kg/m2 and 29.9 kg/m2 to 1.2% for patients with BMI between 50 kg/m2 and 59.9 kg/m2 at 30-day follow-up.
They also noted patients with a BMI between 45 kg/m2 and 49.9 kg/m2 as well as controls matched to patients with a BMI between 50 kg/m2 and 59.9 kg/m2 had the highest revision rates for instability at 2-year follow-up.
“Our findings encourage additional research to evaluate how uncontrollable factors, such as implant selection (dual mobility vs. larger head), the use of intraoperative technology and each patient’s spinopelvic alignment may impact dislocation risk in patients with instability risk factors regardless of BMI,” Acuña concluded.
Perspective
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In this PearlDiver administrative claims database study, the authors found that BMI was not associated with the risk of dislocation after primary THA. Several prior studies have evaluated the risk of BMI on dislocations and report conflicting results. Some studies have reported higher incidences of dislocation with elevated BMI, while others, like this study, did not identify any association. The strength of this study over prior studies is that it compares the risk of dislocation across various BMI stratifications.
There are several patient and surgical factors other than BMI that have a greater impact on the risk of dislocation after primary THA, including surgical approach, femoral head size, acetabular liner type, component positioning and preexisting lumbar disease. BMI should be considered; however, the data from this study suggests that BMI has little to no impact on the risk of dislocation postoperatively. Patients should be counseled that while elevated BMI may not necessarily increase their risk of dislocation, it is a recognized risk factor for other adverse events, most notably infection.
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