The aim of this Phase I/II of the clinical trial is to investigate whether the transplantation of normal myoblasts throughout one muscle (in this case, the extensor carpi radialis) of DMD patients is safe and will improve the strength of that muscle. The patients will be transplanted with myoblasts grown from the muscle biopsy of a healthy donor. Thirty million myoblasts will be injected per cm cube in a progressively higher volume of muscle (i.e., 3, 6 and 9 cm cube). The contralateral muscle will be injected with saline as a control. The patients and the investigators will be blind to the side injected with cells. The strength of both muscles will be measured at 3 months post transplant to verify if myoblast transplantation increased muscle strength. If there is no significant strength increase, the protocol will be terminated immediately for that patient. If there is a significant strength increase, the patient will be maintained under immunosuppression until 6 months and the muscle strength will be re-evaluated.