Patient-Specific Computational Walking Models in Improving Surgical and Rehabilitation Treatment in Patients With Pelvic Sarcomas

Inclusion Criteria: 1. Patients who have received or are scheduled to receive an internal hemipelvectomy with or without reconstruction at UT MD Anderson Cancer Center. 2. Patients who are 18 years of age and older Exclusion Criteria: 1. Patients who have undergone an external (hindquarter amputated), or an isolated type III internal hemipelvectomy. 2. Previous surgery or significant injury to either hip (prospective patients only) 3. Relevant surgery, procedure, injury, or condition in the last two years which may affect hip pain or general movement patterns on either side (prospective patients only) 4. Pregnant women or women nursing an infant 5. Persons with a pacemaker, hearing aid, aneurysm clips or artificial heart valves, and other forms of loose metal implants will be excluded from the study as assessed by a pre-MRI questionnaire administered by the MRI technician at the time of the scan. 6. Radiological exclusion criteria (assessed after MR scan is conducted on the first visit, prior to DSX/CT radiation exposure): evidence on preliminary MRI of fracture, slipped capital femoral epiphysis (SCFE), masses, lesions, or other anomalies not consistent with an FAI diagnosis.