An achondroplastic patient with a thoracolumbar kyphosis was first seen at the age of 16 at our institution. His only concern at that time was the aesthetic implication of his deformity. His physical examination was normal except for loss of the neurologic reflexes in the lower limbs. The radiographs showed a fixed 180° thoracolumbar kyphosis with correct frontal and sagittal balances. No spinal cord anomaly was found on MRI. Two years later, he developed a progressive neurogenic claudication of the lower limbs. He was still neurologically intact at rest. The MRI showed an abnormal central spinal cord signal in front of the apex of the kyphosis associated with the narrow congenital spinal canal. In regards to this progressive neurological worsening, a surgical treatment was decided. We decided to perform a front and back arthrodesis combined with a spinal cord decompression without reduction of the deformity. A five-level hemilaminotomy was performed with a posterior approach at the kyphosis deformity. The spinal cord was individualised onto 10 cm and the left nerve roots were isolated. A decancellation osteotomy of the three apex vertebrae and a disc excision were performed. The posterior aspect of the vertebral body was then translated forward 2 cm and in association with the spinal cord. Two nerve roots were severed laterally to approach the anterior part of the kyphosis and a peroneal strut graft was inlayed anterolaterally. A complementary anterior and a right posterolateral fusion was made with cancellous bone. The patient was immobilised in a cast for 3 months relayed by a thoracolumbosacral orthosis for 6 months. At 3 years follow-up, the neurogenic claudication had disappeared. No worsening of the kyphosis was observed. His only complaint is violent electric shock in the lower limbs with any external sudden pressure on the spinal cord in the area uncovered by bone.