This clinical trial tests how well monitoring the sacral reflexes during surgery (intraoperatively) works to predict the post operative function for patients undergoing removal of the lowest part of the spine (sacrectomy) for pelvic bone cancers or patients undergoing spinal procedures. These surgical procedures can lead to damage to sacral root nerves which can result in impairment to the lower extremities, bowel, bladder, and sexual function. Intraoperative monitoring of sacral reflexes can provide objective, real-time information about pelvic nerve function during surgery. This can aid surgical decision-making and help surgeons better prepare patients to understand the changes that may have occurred to their function as a result of surgery. Intraoperative neuromonitoring may work well to predict postoperative function in patients undergoing sacrectomy for pelvic bone malignancy or patients undergoing spinal procedures.