Lower Back Muscle Size and Recovery After Lumbar Disc Herniation Surgery

Recovery after surgery for a herniated disc in the lower back differs from person to person. The size of the muscles around the lower spine may be related to recovery, but this relationship is not well understood. The purpose of this observational study is to determine whether the size of two lower-back muscles, the psoas and multifidus muscles, measured on magnetic resonance imaging (MRI) scans obtained before surgery is related to recovery after surgery. The study will include 100 adults aged 18 to 75 years who are scheduled for elective surgery for lumbar disc herniation. Participants will receive their usual anesthesia, surgery, and postoperative care. The study will not require any additional imaging, blood tests, medicines, or procedures. Researchers will use each participant's existing preoperative lumbar MRI scan to measure the psoas and multifidus muscles. Participants will complete the 15-item Quality of Recovery questionnaire (QoR-15) before surgery and again 24 hours, 48 hours, and 7 days after surgery. Researchers will also collect information routinely recorded during care, including pain scores, pain medicine use, nausea and vomiting, time spent in the recovery unit, time to first walking, and length of hospital stay. The primary objective is to determine whether preoperative psoas muscle index and multifidus muscle cross-sectional area are independently associated with postoperative Quality of Recovery-15 (QoR-15) scores 24 hours after lumbar disc herniation surgery.

Inclusion Criteria: * Age between 18 and 75 years * Scheduled for elective surgery for lumbar disc herniation * American Society of Anesthesiologists physical status I-III * Availability of a preoperative lumbar MRI obtained as part of routine clinical care * Scheduled to undergo surgery under general anesthesia * Sufficient cognitive and communication ability to understand and complete the quality of recovery (QoR-15) questionnaire * Willingness to participate and provision of written informed consent Exclusion Criteria: * Emergency surgery * Revision lumbar spine surgery * Surgery for a spinal tumor, infection, trauma, vertebral fracture, spinal deformity, advanced spinal stenosis, or another condition other than lumbar disc herniation * Planned spinal fusion or instrumentation * History of a neuromuscular disorder * Severe cognitive impairment, inability to communicate, or inability to complete the QoR-15 questionnaire * Chronic opioid use or a history of opioid dependence * Preoperative lumbar MRI images of insufficient quality for psoas or multifidus muscle measurement