Impact of preoperative spinopelvic risk factors on functional outcomes after total hip arthroplasty : a retrospective cohort study.

AIMS: This study aims to assess the functional outcomes of total hip arthroplasty (THA) in patients with pre-existing spinopelvic risk factors, hypothesizing that reduced spinal mobility and spinal deformities will result in poorer postoperative outcomes.

METHODS

We retrospectively analyzed a cohort of 825 hips which underwent THA between October 2018 and March 2023. Preoperative spinopelvic parameters were assessed, including pelvic incidence (PI), pelvic tilt (PT), standing pelvic tilt (PTstand), supine pelvic tilt (PTsupine), flexed seated pelvic tilt (PTseated), lumbar lordosis (LL), and lumbar flexion (LF) (calculated as standing LL minus flexed seated LL), using radiological measurements in supine, standing, and seated positions. Patients were categorized into risk groups based on five spinopelvic risk factors: lumbar stiffness (LF < 20°), PI - LL mismatch ≥ 20°, large anterior pelvic rotation (ΔPTseated - PTstand ≥ 20°), standing PT ≤ -10°, and large posterior pelvic rotation (ΔPTstand - PTsupine)) ≥ 13°. Functional outcomes were measured using the Hip disability and Osteoarthritis Outcome Score for Joint Replacement (HOOS-JR) 12 months postoperatively. A mixture of both parametric and non-parametric statistical tests were used as required by the data, including Krusal-Wallis tests with Dunn's post-hoc testing, chi-squared tests, Mann-Whitney U tests, multiple linear regression, and propensity score matching.

RESULTS

Of the 825 THAs in 775 patients (mean age 64.57 years (SD 10.01), 50.55% female (n = 417)), 21.7% (179 patients) had one or more spinopelvic risk factors. The mean postoperative HOOS JR scores were 91.6 (SD 11.3) for patients without risk factors and 89.3 (SD 12.4) for those with at least one risk factor, with no clinically significant reduction in score (p = 0.125). However, patients with two or more risk factors had significantly lower HOOS-JR scores compared to those with no risk factors (p = 0.001). Multiple linear regression identified standing PT ≤ -10° as the only individual risk factor significantly associated with poorer functional outcomes (p = 0.029).

CONCLUSION

While preoperative spinopelvic risk factors did not universally result in inferior functional outcomes, patients with multiple risk factors (two or more), particularly those with abnormal standing pelvic tilt, showed significantly lower postoperative HOOS-JR scores. These findings highlight the importance of comprehensive preoperative evaluation of spinopelvic parameters to optimize functional outcomes in THA.