Romosozumab Effects on Bone Density, Muscle Mass, and Spine Surgery Outcomes

The goal of this clinical trial is to learn if romosozumab (Evenity) can improve bone and muscle health in postmenopausal women with osteoporosis who are undergoing lumbar spine surgery. The main questions it aims to answer are: * Does romosozumab improve bone strength and reduce the risk of complications during and after spine surgery? * Does romosozumab increase muscle mass and help patients recover better from surgery? Researchers will compare romosozumab (a monthly injection) to alendronate (a weekly pill), both approved treatments for osteoporosis, to see which is more effective in this surgical setting. Participants will: * Be randomly assigned to receive romosozumab or alendronate * Take standard vitamin supplements and receive a one-time dose of zoledronic acid near the end of the study * Attend five study visits over about 12 months * Undergo bone scans, muscle imaging, and complete health questionnaires before and after surgery