Characterization of complex vertebral transposition (gamma deformity) > 180 degrees: clinical and radiographic outcomes of halo gravity traction and vertebral column resection (VCR).

Study Design: Prospective case series OBJECTIVE: Results of surgical treatment of complex vertebral transposition "Gamma Deformity" > 180 degrees with halo gravity traction (HGT) and vertebral column resection (VCR). We recently published a novel classification system for complex spine deformities of which complex vertebral transposition > 180 degrees (Gamma; type 3) was described. Halo gravity traction (HGT) has been shown to mitigate surgical risk in complex spine deformity correction and in some cases obviates the need for three-column osteotomy. However, we are not aware of report of its utilization in treating Gamma deformities with or without vertebral column resection (VCR).

Methods: A consecutive series of 13 patients with Gamma deformity (GD) were prospectively enrolled at a single site in West Africa. Standard radiographs and 3D computerized tomography (CT) were done to assess coronal and sagittal vertebral transposition (CVT and SVT). The HGT with 50% of body weight was applied over several weeks followed by VCR. Demographics, operative data, radiographic parameters, and complications data were collected.

Results: 13 pts with GD underwent HGT for an avg of 110 days prior to definitive surgery. Etiologies were Congenital-11 pts and Neurofibromatosis-2 pts. Average age: 17.8 years; Pts were reviewed at 3 months post-op and at minimum 2-year follow-up. Preop myelopathy was present in five patients. Pre-op CVT avg 75% and was corrected in all cases post-op. SVT avg 211 deg and improved with HGT by 36% and corrected to 53 deg (74% correction) post-op. Thoracic kyphosis avg -42 deg and averaged 48 deg post-op. Intra-op spinal cord monitoring (SCM) alerts occurred in 8 pts (61%). Post-operative LEM deficits occurred in 5 pts: 2 fully recovered by 3 months and 2 year follow-up, while the remaining 3 improved but had residual motor deficits at final follow-up. There was one post-operative mortality.

Conclusion: The management of complex vertebral transposition (Gamma deformity) > 180 degrees with HGT prior to VCR is not only effective in some patients, but also associated with high SCM alerts and neurologic injury rates. Myelopathic patients with thoracic deformities are at higher risk of developing permanent neurologic deficits. Surgeons should be aware of this rare and unusual deformity and consider HGT and VCR bearing in mind the technical challenges and high complication rate.