[Impaction posterior wedge osteotomy for the treatment of postsurgical flatback: 22 cases]

There is increasing interest in sagittal balance as an important element when planning treatment of spinal deformations. Posture disorders, particularly flatback, can be observed after surgical treatment of scoliosis. The frequency of flat back syndrome has increased with the development of spinal surgery.

Posterior osteotomy is designed to resolve these problems. Two techniques are used: the Smith-Petersen procedure and transpedicular subtraction osteotomy. We adopted the second procedure, adding two technical modifications: installation on an orthopaedic table and intracorporeal cancellous impaction. We performed closed posterior osteotomy by intracorporeal impaction and report here our results in a series of 22 patients with postoperative flat back treated between July 1999 and June 2002. Mean age at surgery was 52 years. There were sixteen women and six men. All patients had a history of spinal surgery with fusion. They had had 2.1 spinal operations on average with a maximum of seven. All patients complained of severe postural pain. They had difficulty bending forward and standing back up. Radiographically, we noted altered spinal and pelvic angles and an abnormal plumb line from C7 to the promontory.

We analyzed outcome at 21 months on average. Preoperatively five patients had 12 levels of non-union. Osteotomy was performed at L4 in nineteen patients and L3 in three. A rigid instrumentation was used in all cases. Osteosynthesis material was implanted after correction of the deformation with no particular problem for spinal stability or reduction. Mean operative time was 180 minutes and mean blood loss was 1680 ml. A complementary anterior approach was required in one patient. Intraoperative complications were dominated by dural breaches in five patients, high paraplegia not directly related to the osteotomy in one patient, regressive S1 paresia occurred in one patient and transient cruralgia which regressed in 4 to 6 months in four patients. We also observed functional intestinal obstruction in one patient and severe depression in another. There were no infections or deaths. We also observed two cases of predominant correction at the discal level and not the vertebral level. All operated patients felt their posture was improved and were able to maintain the upright position for prolonged periods. Flexion of the lower limbs was improved. Mean correction of lumbar lordosis was 25.1 degrees (range 12-39). Mean sacral slope was 33 degrees . Mean correction of the position of C7 on the promontory plumb line was 72 mm. This variable was highly altered preoperatively (95.6 mm) and was improved after osteotomy in all patients. At last follow-up, there was one case of nonunion which had been successfully revised.

The literature on osteotomy for the treatment of flat back is sparse. Our series of subtraction osteotomy is the largest reported to date. Preoperative and intraoperative planning remain a topic of debate and require further study.