Spinopelvic parameters. From Delsole EM, Vigdorchik JM, Schwarzkopf R, Errico TJ, and Buckland AJ. Total hip arthroplasty in the spinal deformity population: does degree of sagittal deformity affect rates of safe zone placement, instability, or revision? J Arthroplasty. 2017; 32(6):1910–1917