Association between Preoperative Vitamin D Status and Short-Term Physical Performance after Total Hip Arthroplasty: A Prospective Study

Background: Insufficient serum vitamin D concentrations (50-75 nmol/L) are prevalent in 40-65% of patients who require total hip arthroplasty (THA). This could impair physical recovery after surgery. This study investigated the association between preoperative vitamin D status and physical performance after THA. Additionally, postoperative changes in vitamin D concentrations were measured. Methods: We included 87 patients scheduled for elective THA and aged ≥65 years. Three groups were recruited: patients classified as vitamin D deficient (< 50 nmol/L, n = 23), insufficient (50-75 nmol/L, n = 32), or sufficient (> 75 nmol/L, n = 32). Serum 25-hydroxyvitamin D₃ (25[OH]D₃) concentration and physical performance were measured perioperatively. Linear mixed models were used to examine differences between groups. Results: Change in physical performance over time was not affected by preoperative vitamin D status. In contrast, for physical activity, both vitamin D (p = 0.021) and time (p < 0.001) effect was seen: from 80.2 ± 25.8 to 58.1 ± 17.8 min/day in the deficient group, 143.7 ± 19.8 to 92.9 ± 11.5 min/day in the insufficient group, and 108.1 ± 20.9 to 62.3 ± 12.9 min/day in the sufficient group. The Chair Stand Test, Timed Up and Go test, and 10-Meter Walking Test also improved significantly over time, but independent of vitamin D status. An increase in 25(OH)D₃ concentration 6 weeks postoperatively was correlated with improved hip function (Pearson's r = -0.471, p = 0.018). Overall, serum 25(OH)D₃ declined with 32% one day after surgery (p < 0.001), to nearly return to baseline values 6 weeks later in all groups. Conclusion: Vitamin D status did not appear to affect physical recovery after THA. The drop in vitamin D after surgery deserves further investigation, but could possibly be explained by hemodilution.