Tethered cord is a common finding in congenital scoliosis. The most frequently advocated approach for this condition is to perform prophylactic detethering of the cord before scoliosis corrective surgery. The authors report on a 14-year-old patient with congenital thoracic kyphoscoliosis associated with a tethered cord, who developed progressive paraparesis and was successfully treated by posterior spine shortening osteotomy alone without prophylactic untethering. The patient had a 103° scoliotic curve together with a 93° kyphotic curve with an apical vertebra of T-7. Furthermore, he developed a significant progression of neurological deficits, including weakness of both legs and urinary and bowel incontinence. Preoperative MRI revealed that the spinal cord was entrapped by the apical vertebra and the low-placed conus medullaris was at approximately L-5. A posterior vertebral column resection of T-7 was performed for the purpose of simultaneously correcting the kyphoscoliosis and releasing tension on the tethered cord without a true detethering surgery. The patient's spinal cord function recovered completely from Frankel D to Frankel E by 6 months after the procedure. Evaluation at 31 months after surgery showed maintenance of good curve correction and normal neurological function.