Radiological Spinopelvic Parameters Can Be Risk Factors for Early Total Hip Replacement After Spine Fusion

<h3>Background</h3> Interest in the correlation between the spinopelvic complex and its radiographic parameters in early total hip arthroplasty has been increasing. This study investigated whether radiological spinopelvic parameters are risk factors for early total hip replacement (THR) within 1 year of spinal fusion surgery. The primary research question focused on identifying specific spinopelvic changes that may lead to early THR. <h3>Methods</h3> We retrospectively analyzed patients who underwent lumbar spinal fusion between 2016 and 2021. The patients were divided into 2 groups: patients who underwent early THR (<i>n</i> = 35) and patients who did not (<i>n</i> = 213). Spinopelvic parameters, including pelvic incidence (PI), sacral slope (SS), pelvic tilt, lumbar lordosis, thoracolumbar kyphosis (TLK), sagittal vertical axis, and thoracic kyphosis (TK), were measured before and after surgery. The statistical analyses included inverse probability of treatment weighting, independent <i>t</i> tests, <i>χ</i>² tests, and logistic regression analyses. <h3>Results</h3> A total of 248 patients were included in the study. The pre- and postoperative TLK and TK angles were significantly smaller in the early THR group than in the late THR group. Increases in the PI and SS after surgery were significant risk factors. The use of interbody fusion techniques was associated with a higher rate of early THR. The difference in the PI minus lumbar lordosis before and after surgery was also significantly correlated with early THR. <h3>Conclusions</h3> Abnormal spinopelvic parameters, especially reduced TLK and TK angles and increased PI and SS, are risk factors for early THR. <h3>Clinical Relevance</h3> Changes in spinopelvic parameters can lead to rapid hip joint destruction, which highlights the need for careful preoperative evaluation and postoperative monitoring of patients to prevent early THR. <h3>Level of Evidence</h3> 3.