Metastatic Bone Disease

This study aims to evaluate how walking stability and the ability to perform daily activities change during cancer treatment, and whether a smartwatch can detect these changes. The goal is to develop proactive, personalized tools that automatically monitor treatment response and predict potential complications. To support future implementation, the study will assess the feasibility of wearing a smartwatch for at least 12 hours per day, using a mobile application, and completing weekly questionnaires among patients with primary osteosarcoma or metastatic bone disease.

The goal of this clinical trial is to find out if removing and replacing part of the hip bone works better than using metal hardware to stabilize the bone in patients whose cancer has spread to the hip. The main questions are: 1. Does removing and replacing part of the bone work better than just stabilizing it with metal hardware? 2. Does removing and replacing the bone help reduce problems like cancer coming back or the metal hardware breaking? Researchers will compare two treatments: using metal rods and plates to stabilize the bone (internal fixation) versus removing part of the bone and possibly replacing the hip joint (resection and reconstruction) to see if the second option causes fewer problems. Participants will: * Be randomly assigned to one of two groups (internal fixation or resection and reconstruction). * Have one of the two surgeries based on which group they're in. * Go to follow-up appointments with the study doctor at 2 weeks, 6 weeks, 4 months, 6 months, 9 months, and 12 months after surgery.