Moderate to severe rigid cervical kyphosis: morphological characteristics and surgical treatment

English Keywords:Cervical kyphosis  Rigid  Morphological characteristics  Surgical approach  Osteotomy

English Abstract:

  【Abstract】 Objectives: To evaluate the sagittal morphological characteristics of moderate to severe rigid cervical kyphosis, and to analyze the factors related to surgical correction effect and neurological outcome.Methods: 34 patients with moderate to severe rigid cervical kyphosis who were surgically treated at our hospital between January 2014 and March 2021 were retrospectively enrolled. The moderate to severe kyphosis was defined as regional kyphosis angle ≥20°. The rigid kyphosis was defined as flexibility <30% or segmental ankylosis visualized on CT scans. The mean age of the enrolled patients at operation was 50.1±17.6 years (range: 14-83 years), comprising 21 male patients and 13 female patients. The etiologies were degenerative kyphosis in 18 cases, congenital deformity in 5 cases, iatrogenic kyphosis in 5 cases, ankylosing spondylitis in 3 cases, and traumatic kyphosis in 3 cases. 24 cases were operated through anterior approach, 5 through posterior approach, and 5 through combined approach, respectively. Three-column osteotomy with deformity correction was performed in five patients. The baseline data, surgical parameters, and follow-up information were collected. The neck pain and neurological functional status were evaluated with visual analogue scale (VAS), neck disability index (NDI), and modified Japanese Orthopaedic Association scale (mJOA), respectively. The regional kyphosis angle, T1 slope, cervical sagittal vertical axis, and chin-brow vertical angle were measured on lateral film of cervical spine radiographs before operation, immediately after operation and at the final follow-up. The deformity angular ratio was defined as regional kyphosis angle/number of segments involved in kyphosis. According to the distribution of data, independent sample or paired sample t test, Mann-Whitney U test, Wilcoxon signed-Rank test, Chi-square test or Fisher′s exact probability test were selected to compare the distribution of the above radiographic parameters and scoring indexes at different time points or in different subgroups of patients. Results: The patients had a median regional kyphosis angle of 25° (ranged 20° to 100°) and a median deformity angular ratio of 7.5° (ranged 5° to 25°). They were divided into two groups according to mJOA score. The deformity angular ratio in patients with severe cervical myelopathy was significantly higher than that of patients with mild to moderate cervical myelopathy [9.3° (5.0°-25.0°) vs 7.0° (5.3°-10.0°), P=0.016]. The mean operation time was 277±140 minutes, and the median blood loss was 150 (20-2000)ml. The regional kyphosis angle and deformity angular ratio were corrected from 31.6°±19.5° and 8.8°±4.2° preoperatively to 2.8°±5.7°and 0.9°±1.9° postoperatively, respectively. These differences were statistically significant(P<0.001). After 1.0±0.8 (0.3-3.1) years of radiographic follow-up, there was no statistical difference in the measured values of these two sagittal parameters at the final follow-up compared with those immediately after the operation(P>0.05). The mean clinical follow-up time was 3.0±1.5 years. At the final follow-up, the VAS, NDI and mJOA scale were improved from 5.3±1.8, (27.7±16.5)% and 11.9±4.3 preoperatively to 1.3±1.2, (7.7±7.1)% and 14.8±2.2 postoperatively, respectively. These differences were statistically significant(P<0.001). The correction of deformity angular ratio was positively correlated with the improvement of mJOA(Spearman r=0.417, P=0.018). There were 14 (41.2%) patients showed early postoperative complications, including 10 (29.4%) neurological deficits, and 8 patients (23.5%) developed late complications. Patients with early postoperative complications had a longer course of disease, higher proportion of the highest osteotomy grade >2, and greater operative blood loss. Conclusions: Choosing appropriate surgical methods for the treatment of moderate to severe rigid cervical kyphosis can achieve satisfactory clinical results. The deformity angular ratio can be regarded as an important parameter for morphological evaluation, which is able to predict the postoperative improvement of neurological function to some extent.