Anterior slip phenomenon of the vertebrae after corpectomy surgery and its clinical significance

Abstract

To investigate the anterior slip phenomenon of the vertebrae after corpectomy surgery and its clinical significance. The clinical data of 164 patients with cervical spondylotic myelopathy treated from January 2010 to April 2013 were retrospectively analyzed. There were 88 males and 76 females, aged from 38 to 74 years old with the mean of 56.2 years. Among them, 31 cases for C₄ corpectomy, 87 cases for C₅ corpectomy, 46 cases for C₆ corpectomy. Preoperative and postoperative distance of posterior wall of vertebral canal to the line of adjacent upper vertebral bodies anterosuperior border and lower vertebral bodies anteroinferior border was measured by CT in cervical sagittal middle layer scanning as the center, anterior slip degree of the vertebrae after operation was evaluated. The fast clustering method was used, the vertebral shift distance as variable, according to the size of the forward distance, 90 cases classified as group 1(forward greatly group), and the 74 cases classified as group 2(forwad short group). The relationships on the anterior slip of the vertebrae and cervical curvature, surgical segment were analyzed. Japanese Orthopaedic Association (JOA) scores and its improvement rate were observed before and after operation, and the relationships on the anterior slip of the vertebrae and sagittal plane diagonal diameter of spinal canal, clinical effect were analyzed. All the patients were followed up from 12 to 48 months with an average of 29.5 months. All operative vertebrae occurred anterior slip with different degree after corpectomy surgery, the maximum was 3.52 mm and minimum was 1.12 mm, with an average of (2.14±1.02) mm. According to the clustering method, the anterior slip distance with (3.07±0.21) mm classified as forward greatly group(90 cases, 54.9%) and the anterior slip distance with (1.55±0.32) mm classified as forwad short group(74 cases, 45.1%). There was no significant difference between anterior slip distance and operation segments(χ²=0.01, P=0.996). Cervical curvature index and anterior slip distance of operated vertebra had a positive correlation (r=0.724). The incidence of reduction of the diagonal diameter of cervical spinal canal in forward greatly group was higher than that of forwad short group(χ²=4.45, P=0.035). The patients with unsatisfactory efficacy appeared obvious anterior slip of the vertebrae after corpectomy than the patients with satisfactory efficacy(P<0.05). Corpectomy of the cervical spine can result in vertebral forward displacement trend, and obvious displacement may cause the secondary compression of the spinal cord.