Spinal Realignment for Adult Deformity: Three-column Osteotomies Alter Total Hip Acetabular Component Positioning

Introduction: A goal of adult spinal deformity surgery is correction of sagittal imbalance by increasing lumbar lordosis (LL), allowing a previously retroverted pelvis to normalize as evidenced by decreases in pelvic tilt (PT). Realignment of pelvic orientation may alter the position of preexisting total hip arthroplasties (THAs). Methods: Twenty-seven patients with unilateral THA who underwent thoracolumbar fusions for adult spinal deformity from the pelvis to L1 or above were retrospectively reviewed (levels fused, 10.3 [range, 6 to 17]; age, 70 9 years). Comparisons of preoperative and postoperative spinal deformity parameters, acetabular tilt (AT), and acetabular cup abduction angle (CAA) were performed, with subgroup analysis for those who had undergone three-column osteotomy and those who had not. Results: Preoperative deformity was severe, with findings of a sagittal vertical axis >9 cm, PT >25, and pelvic incidence-LL >20 degrees. Postoperatively, AT decreased significantly (-7 degrees +/- 10 degrees; P < 0.001), signifying relative acetabular retroversion. Comparing patients with three-column osteotomy versus those without, AT changes were greater in those with three-column osteotomy (11 degrees +/- 7 degrees and -2 +/- 10 degrees, respectively; P = 0.024). AT was significantly correlated with changes of PT (r = 0.704; P < 0.001). and LL (r = -0.481; P = 0.011). AT decreased (ie, retroverted) 1 degrees for every 3.23 degrees of LL or 1.13 degrees of PT correction. The corona! plane CAA did not change substantially. Discussion: Spinal deformity correction, with techniques such as three-column osteotomy, result in significant THA acetabular component repositioning in the sagittal plane. Resultant decreased AT (ie, retroversion) theoretically may affect tribology, wear, and joint stability and warrants further investigation.