Jumbo Femoral Heads in Total Hip Arthroplasty: Improved Early Stability Without Added Complications.

Abstract

Larger femoral heads have been proposed to reduce dislocation risk following total hip arthroplasty (THA). While the benefit of increasing head size from 28 or 32 mm to ≥ 36 mm is well established, it remains unclear whether jumbo (40 or 44 mm) femoral heads confer additional stability over traditional large (36 mm) heads. This study aimed to determine whether jumbo heads improve stability or alter early complication rates. We identified 6,413 primary THAs with large-diameter femoral heads (36-, 40-, or 44-mm) implanted at a single institution between February 1, 2016, and December 31, 2022. Cases were stratified by femoral head diameter into the traditional large-head (36 mm, n = 5,897) and jumbo-head (40 or 44 mm, n = 516) groups. The median follow-up was 2.4 years (range, 0.1 to 9.8; interquartile range [IQR], 1.3 to 4.1). The primary outcome was prosthetic hip dislocation at the last clinical follow-up. Time-to-event analyses were performed using multivariable Cox models with surgeon-level random effects, adjusting for patient-specific factors, year of surgery, surgical approach, and robotic assistance. In the full follow-up period, jumbo heads were not associated with a lower adjusted dislocation risk (hazard ratio (HR): 0.55 [95% confidence interval (CI): 0.13 to 2.34], P = 0.139) when compared with 36 mm heads. When analysis was truncated to the first postoperative year, 40 or 44 mm heads were associated with a lower dislocation risk compared with 36 mm heads (HR: 0.20 [95% CI: 0.05 to 0.79], P = 0.032). There were no significant differences in dislocation risk observed at 90 days. Rates of postoperative complications (periprosthetic joint infection and fracture) were similar between groups at 90 days, one year, and last follow-up. Compared with traditional large heads (36 mm), jumbo heads (40 or 44 mm) provided a modest, transient reduction in dislocation risk during the first postoperative year, most evident following the posterior approach THA, but did not confer additional long-term protection. Jumbo heads were not associated with increased rates of early surgical complications. Longer-term studies are warranted to address historical concerns.