The goal of this feasibility clinical trial is to learn if melatonin can help teens having major musculoskeletal surgery by promoting healthy sleep. Melatonin is available as a dietary supplement that may be effective in promoting longer, higher quality sleep. This study will assess the feasibility and acceptability of melatonin for teens undergoing major musculoskeletal surgery, as well as determine optimal measured outcomes (sleep, pain, health-related quality of life) at short- and long-term follow-up.