89. The use of predictive modeling to determine postoperative thoracic kyphosis and pelvic tilt in adult spinal deformity surgery

Abstract

<h3>BACKGROUND CONTEXT</h3> To minimize complications associated with adult spinal deformity (ASD) surgery, many surgeons pre-operatively plan sagittal plane correction. Unfortunately, it is unclear how the native spine will react postoperatively. In attempts to account for this compensatory response after fusion with upper instrumented level in the lower thoracic region, these authors initially planned thoracic kyphosis restoration to 40° (or left as is if initial kyphosis >40°). After measuring actual compensatory responses postoperatively, this preoperative planning underwent iterative improvement and now utilizes a complex predictive model to simulate compensation. <h3>PURPOSE</h3> The aim was to determine if a predictive model can simulate changes in thoracic kyphosis (TK) and pelvic tilt (PT) after ASD surgery and to compare it to the prior planning strategy. <h3>STUDY DESIGN/SETTING</h3> This is a retrospective study evaluating a complex predictive model's use in ASD surgery planning. <h3>PATIENT SAMPLE</h3> The study population consisted of 42 patients who had surgeries previously planned using the older planning technique. <h3>OUTCOME MEASURES</h3> Outcome measures included predictive model, prior planning strategy, and postoperative TK and PT values. <h3>METHODS</h3> Radiographic data from over 500 patients was utilized in training and testing the model. The model used projected lumbar lordosis and number of instrumented levels to predict postoperative TK and PT. With the model, 12- and 24-month postoperative TK and PT were simulated for the patients who had previously planned surgeries. The model and previous planning method were compared to actual postoperative values. <h3>RESULTS</h3> There were significant differences between measured pre- and postoperative TK and PT. The predictive postoperative values at 12- and 24-M for TK and PT did not significantly differ from actual postoperative values, with better correlative values to actual TK than the previous plan. <h3>CONCLUSIONS</h3> Patients undergo significant long-term compensatory TK and PT changes, indicating need for pre-operative predictive modeling to aid in surgical planning. The predictive model can project thoracolumbar spine compensation after deformity correction surgery. It is better than the prior planning strategy at anticipating long-term TK and possibly PT. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.