[New type spinal osteotomy with cage inserting anteriorly and closing posteriorly to correct thoracolumbar kyphosis by a single posterior approach].

OBJECTIVE: To evaluate the feasibility, safety and efficacy of surgical correction of thoracolumbar kyphosis, using the new type spinal osteotomy with cage inserting into the intervertebral gap anteriorly and closing posteriorly by a single posterior approach.

METHODS: Since 2003, eight consecutive patients with thoracolumbar kyphosis were treated surgically. There were 4 male and 4 female with the mean age of 35 years old (from 14 to 58 years old). There were 3 cases of congenital kyphosis with scoliosis, 1 case of old spinal tuberculosis kyphosis, 2 cases of post-traumatic kyphosis, 1 case of ankylosing spondylitic kyphosis with old stress fracture and 1 case of iatrogenic kyphosis post-op of laminectomy due to the removal of ependymoma from cauda equina. The apex level of kyphosis was T(11) in 1 case, T(12) in 2 cases, L(1) in 3 cases and L(2) in 2 cases. The average preoperative Cobb angle of kyphosis was 73 degrees (range from 42 degrees to 90 degrees), there were 3 cases associated with scoliosis, with the mean preoperative Cobb angle of scoliosis was 25.7 degrees (range from 20 degrees to 36 degrees). According to the Frankel grading system, 2 cases were classified as Grade C, 2 cases as Grading D and 4 cases as Grading E preoperatively. All the patients had severe thoracolumbar dorsum pain with difficulty of sitting. The bladder sphincter function disturbance were also found in 3 cases. The main procedures of the new type spinal osteotomy consisted of temporary rod installation, trans-intervertebral spinal osteotomy, circumferential decompression of the spinal cord, dissection and complete cut of the anterior longitudinal ligament, spreading the intervertebral gap with the distraction forceps during the instrumentation correction maneuver and replaced by the cage filled with autograft bone inserting into the intervertebral gap, then the closing maneuver followed.

RESULTS: The average operation time was 4.5h (range from 3.5 to 6 h), and the mean blood loss volume during the operation was 2280 ml (range from 700 to 4200 ml). All patients underwent surgery safely and there were no major complications related to the surgical procedures, apart from CSF leakage of 1 case postoperatively and transient low blood pressure of 1 case intraoperatively. Localized kyphosis, scoliosis were reduced from an average of 73 degrees to 8.3 degrees and 25.7 degrees to 18.7 degrees respectively with an average 12.8 months follow-up. Bony fusion were achieved in all patients and there was no correction loss. Neurologic improvement occurred in 1 case from Frankel Grade C to Grade D, and 1 case from Frankel Grade D to Grade E after the surgery. The bladder sphincter function were also found improved in 2 cases postoperatively.

CONCLUSIONS: The new type spinal osteotomy with cage inserting anteriorly and closing posteriorly by a single posterior approach was a safe, reliable and effective surgical procedure for the treatment of the thoracolumbar kyphosis with the Cobb angle from 40 degrees to 90 degrees. Compared with the other common spinal wedge osteotomies, the deformation danger, such as hanging down, kinking or dural buckling could be effectively prevented, a better correction rate is also achieved significantly with this new type procedure.