 Nearly all patients with Duchennes Muscular Dystrophy DMD have scoliosis. Posterior instrumented spinal fusion, which is a surgery to correct scoliosis, has been shown to improve quality of life and satisfaction of both parents and families. The progressive muscular weakness leads to the development of scoliosis soon after the child has become unable to walk. The muscular weakness and scoliosis also affect the pulmonary function of these children. Pulmonary Function Tests PFT have been used to determine pulmonary fitness prior to surgery as a way to determine how well or if the child will tolerate surgery. Children with poor results on the PFT are determined to be too fragile to tolerate such a large operation. The physicians conducting this study feel that the PFT may be inaccurate and that this may not be the best single test to determine pulmonary fitness. The physicians conducting the study think things like the time of day the study is done, how tired you are when you complete the test, and how well you understand the test may affect the results of the test. 