Preoperative Hemoglobin as a Continuous Predictor of Postoperative Complications Following Elective Total Hip Arthroplasty.

BACKGROUND

Preoperative anemia is associated with adverse outcomes following total hip arthroplasty (THA). However, discrete hemoglobin thresholds may obscure potentially meaningful relationships between anemia severity and postoperative risk. This study assessed preoperative hemoglobin as a continuous variable to predict periprosthetic joint infection (PJI), medical, and surgical complications following elective THA.

METHODS

A health care database was utilized to identify all primary THA patients between 2016 and 2023 with a hemoglobin value available within 28 days preoperatively. The primary outcome was PJI within 90 days of surgery. The secondary outcomes included 90-day aggregate medical and surgical complications. Multivariable logistic regressions with restricted cubic splines (RCS) evaluated hemoglobin as a continuous predictor of postoperative risk. Changepoints were identified using a Metropolis-Hastings bootstrap simulation. In total, 25,654 THAs were included, of which 126 (0.5%) developed PJI within 90 days.

RESULTS

The RCS analysis identified hemoglobin changepoints of 13.5 g/dL for PJI and aggregate medical complications and 13.3 g/dL for aggregate surgical complications. Compared to 13.5 g/dL, patients who had hemoglobin values of 11.0 and 8.0 g/dL had a 1.91-fold (95% confidence interval (CI): 1.37 to 2.68) and 4.40-fold (95% CI: 1.91 to 10.14) increased risk of PJI, respectively. Below the identified changepoint, relative risk increased in a stepwise manner, with average increases of 14.9, 23.2, and 30.7% observed for each 0.5 g/dL decrement from 13.5 to 12.0, 12.0 to 11.0, and 11.0 to 10.0 g/dL, respectively. A similar incremental increase in risk was observed for aggregate medical and surgical complications with each hemoglobin decrement across these ranges.

CONCLUSIONS

Anemia severity is associated with a nonlinear increase in the risk of PJI, medical, and surgical complications following THA. Identified changepoints should inform, not dictate, surgical eligibility and may support individualized optimization. Further research is needed to determine whether anemia correction reduces complication risk.