In vivo deformation of the spine canal before and after surgical corrections of severe and rigid kyphoscoliosis

BACKGROUND: Ponte osteotomy and posterior vertebral column resection (PVCR) are two popular surgical techniques in treatment of severe and rigid kyphoscoliosis. However, quantitative effects of the two surgeries on spinal cord deformation are unclear. This information is critical for improvement of the treatment methods that can maximally correct the spinal deformity and prevent neurological complications. METHODS: Ten patients with severe kyphoscoliosis were investigated. X-ray and CT images of full spine of all patients were acquired before and 6–24 months after surgical treatment using either Ponte osteotomy or PVCR. A 3D model of the spine was constructed for each patient using the CT images that included the spinal canal between T2 and L2 vertebrae. The spinal canal length (SCL) was determined at 5 locations on the cross section of the canal: anterior, posterior, left, right (concave or convex side) and centre positions. The perpendicular distances between the T2 and L2 vertebrae, COBB angles and patient reported outcome measures before and after operations were determined. RESULTS: For patients treated with Ponte osteotomy, the SCLs were elongated by 12.7 ± 9.5 mm (5.4 ± 3.9%) at the concave side and 3.2 ± 6.8 mm (1.3 ± 2.8%) at the convex side. The COBB angle was corrected by 55.8% and the T2-L2 distance was increased by 66.1 ± 12.0 mm (68.4 ± 15.9%). For patients treated using PVCR, the SCLs were shortened by −5.5 ± 5.3 mm (−2.3 ± 2.2%) at the concave side and −14.0 ± 6.6 mm (−5.2 ± 2.6%) at the convex side. The COBB angle was corrected by 60.0% and the T2-L2 distance was increased by 41.5 ± 12.4 mm (32.1 ± 23.0%). The patient reported outcome scores were improved using both surgeries (p < 0.05). CONCLUSION: Ponte and PVCR surgeries caused significant changes of the SCL in scoliosis patients in different ways. The Ponte osteotomy mainly caused elongation of the SCL at concave side and the PVCR caused compression of the SCL at the convex side. Both surgeries partially improved the spinal deformity. The data provide insights for development of new surgical techniques that integrates the advantages of both Ponte and PVCR osteotomies to maximally correct the spine deformity and prevent neurological complications. THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE: The methodology and the data presented in this paper could be instrumental for development of computer assisted surgical techniques that can maximally correct the spinal deformity and minimize the effect on the spinal cord in scoliosis patients.