Association between diffuse idiopathic skeletal hyperostosis and thoracic kyphosis in patients with cervical myelopathy: a retrospective observational study

Background Diffuse idiopathic skeletal hyperostosis (DISH) is a structural abnormality of the thoracic spine that is known to impair posture. However, the relationship between DISH and sagittal balance in the whole spine is unclear. The aims of this study were to investigate the prevalence of DISH in patients with cervical myelopathy caused by cervical ossification of the posterior longitudinal ligament (OPLL) or cervical spondylosis and to compare sagittal alignment of the spine between patients with and without DISH. Methods A total of 103 consecutive patients with a diagnosis of cervical myelopathy due to cervical OPLL or spondylosis were retrospectively enrolled in this single-center study. DISH was defined as an ossified lesion that was seen to be completely bridging at least four contiguous adjacent vertebral bodies in the thoracic spine on computed tomography scans. Cervical and spinopelvic sagittal parameters were measured in whole spine radiographs. Results The study population included 28 cases with DISH [DISH (+) group] and 75 without DISH [DISH (−) group]. OPLL was more prevalent in the DISH (+) group than in the DISH (−) group; however, there were no significant differences in other clinical findings. Propensity score matching produced 26 pairs. C7 slope, C2-7 sagittal vertical axis (C-SVA), whole thoracic kyphotic angles, upper thoracic kyphosis, and T5-T12 thoracic kyphosis values were significant higher in the DISH (+) group than in the DISH (−) group. There was no significant between-group difference in the other sagittal spinopelvic parameters. Conclusions This study is the first to compare sagittal alignment in patients with cervical myelopathy according to whether or not they have DISH. Patients with DISH are more likely to have excessive kyphosis in the thoracic spine, a high C7 slope, and a high C2-7 SVA.

What is the most accurate substitute for an invisible T1 slope in cervical radiographs? A comparative study of a novel method with previously reported substitutes

OBJECTIVE The ability to utilize the T1 slope is often limited by poor visibility on cervical radiographs. The C7 slope has been proposed as a reliable substitute but may have similar limitations of visibility. Herein, the authors propose a novel method that takes advantage of the superior visibility on CT to accurately substitute for the radiographic T1 slope and compare the accuracy of this method with previously reported substitutes. METHODS Lateral neutral standing cervical radiographs and cervical CT scans were examined. When the T1 slope was clearly visible on radiographs, the C3–7 slopes and T1 slope were measured. In CT method 1, a direct method, the T1 slope was measured from the upper endplate of T1 to the bottom edge of the CT image, assuming the edge was parallel to the horizontal plane. In CT method 2, an overlaying method, the T1 slope was calculated by superimposing the C7 slope angle measured on a radiograph onto the CT scan and measuring the angle formed by the upper endplate of T1 and the superimposed horizontal line of the C7 slope. A Pearson correlation with linear regression modeling was performed for potential substitutes for the actual T1 slope. RESULTS Among 160 patients with available noninstrumented lateral neutral cervical radiographs, the T1 slope was visible in only 54 patients (33.8%). A total of 52 patients met the inclusion criteria for final analysis. The Pearson correlation coefficients between the T1 slope and the C3–7 slopes, CT method 1, and CT method 2 were 0.243 (p = 0.083), 0.292 (p = 0.035), 0.609 (p < 0.001), 0.806 (p < 0.001), 0.898 (p < 0.001), 0.426 (p = 0.002), and 0.942 (p < 0.001), respectively. Linear regression modeling showed R2 = 0.807 for the correlation between C7 slope and T1 slope and R2 = 0.888 for the correlation between T1 slope with the CT method 2 and actual T1 slope. CONCLUSIONS The C7 slope can be a reliable predictor of the T1 slope and is more accurate than more rostral cervical slopes. However, this study disclosed that the novel CT method 2, an overlaying method, was the most reliable estimate of true T1 slope with a greater positive correlation than C7 slope. When CT studies are available in patients with an invisible T1 slope on cervical radiographs, CT method 2 should be used as a substitute for the T1 slope.

Physiologic Cervical Alignment Change between Cervical Spine X-ray and Computed Tomography

Objective : The purpose of this study was to investigate the correlations among various radiological parameters used to determine cervical alignment from cervical spine radiographs (X-CS) and cervical spine computed tomography (CT-CS), both within and between modalities.Methods : This study included 168 patients (≤60 years old) without a definite whole spine deformity who underwent CT-CS and X-CS. We measured occipital slope (O-s), C1 slope, C2 slope, C7 slope, sella turcica - C7 sagittal vertical axis (StC7-SVA), spinocranial angle, T1 slope, and C27-SVA. We calculated the O-C2 angle, O-C7 angle, and C2-7 angle from the measured parameters and conducted correlation analyses among multiple parameters.Results : The intrinsic correlation features among multiple cervical parameters were very similar for both X-CS and CT-CS. The two SVA parameters (C27-SVA and StC7-SVA) were mainly influenced by the upper cervical slope parameters (r=|0.13–0.74|) rather than the lower slope cervical parameters (r=|0.08–0.13|). The correlation between X-CS and CT-CS for each radiological parameter was statistically significant (r=0.26–0.44) except for O-s (r=0.10) and StC7-SVA (r=0.11).Conclusion : The correlation patterns within X-CS and CT-CS were very similar in this study. The correlation between X-ray and CT was statistically significant for most radiological parameters, and the correlation score increased when the horizontal gaze was consistently maintained. The lower cervical parameters were not statistically associated with translation-related parameters (C2-7 SVA and StC7-SVA). Therefore, the upper cervical segment may be a better predictor for determining head and neck translation.

K-Line Tilt is a Predictor of Postoperative Kyphotic Deformity After Laminoplasty for Cervical Myelopathy Caused by Ossification of the Posterior Longitudinal Ligament

Study Design: Retrospective single-center study. Objectives: K-line is a decision-making tool to determine the appropriate surgical procedures for patients with cervical ossification of the posterior longitudinal ligament (C-OPLL). Laminoplasty (LAMP) is one of the standard surgical procedures indicated on the basis of K-line measurements (+: OPLL does not cross the K-line). We investigated the impact of K-line tilt, a radiographic parameter of cervical sagittal balance measured using the K-line, on surgical outcomes after LAMP. Methods: The study included 62 consecutive patients with K-line (+) C-OPLL who underwent LAMP. The following preoperative and postoperative radiographic measurements were evaluated: (1) the K-line, (2) K-line tilt (an angle between the K-line and vertical line), (3) center of gravity of the head –C7 sagittal vertical axis, (4) C2–C7 lordotic angle, (5) C7 slope, and (6) C2–C7 range of motion. Clinical results were evaluated using the Japanese Orthopedic Association scoring system for cervical myelopathy (C-JOA score). Results: All the patients had non-kyphotic cervical alignment (CL ≥ 0°) preoperatively; however, kyphotic deformity (CL < 0°) was observed in 6 patients (9.7%) postoperatively. The recovery rate of the C-JOA scores was poor in the kyphotic deformity (+) group (7.8%) than in the kyphotic deformity (−) group (47.5%). The K-line tilt was identified to be a preoperative risk factor in the multivariate analysis, and the cutoff K-line tilt for predicting the postoperative kyphotic deformity was 20°. Conclusions: LAMP is not suitable for K-line (+) C-OPLL patients with K-line tilts >20°.

Specific sagittal alignment patterns are already present in mild adolescent idiopathic scoliosis

Purpose The complex three-dimensional spinal deformity in AIS consists of rotated, lordotic apical areas and neutral junctional zones that modify the spine’s sagittal profile. Recently, three specific patterns of thoracic sagittal ‘malalignment’ were described for severe AIS. The aim of this study is to define whether specific patterns of pathological sagittal alignment are already present in mild AIS. Methods Lateral spinal radiographs of 192 mild (10°–20°) and 253 severe (> 45°) AIS patients and 156 controls were derived from an international consortium. Kyphosis characteristics (T4–T12 thoracic kyphosis, T10–L2 angle, C7 slope, location of the apex of kyphosis and of the inflection point) and sagittal curve types according to Abelin-Genevois were systematically compared between the three cohorts. Results Even in mild thoracic AIS, already 49% of the curves presented sagittal malalignment, mostly thoracic hypokyphosis, whereas only 13% of the (thoraco) lumbar curves and 6% of the nonscoliosis adolescents were hypokyphotic. In severe AIS, 63% had a sagittal malalignment. Hypokyphosis + thoracolumbar kyphosis occurred more frequently in high-PI and primary lumbar curves, whereas cervicothoracic kyphosis occurred more in double thoracic curves. Conclusions Pathological sagittal patterns are often already present in curves 10°–20°, whereas those are rare in non-scoliotic adolescents. This suggests that sagittal ‘malalignment’ patterns are an integral part of the early pathogenesis of AIS.

Comparison study of clinical outcomes and sagittal alignment improvement between anterior and posterior fusion techniques for multilevel cervical spondylotic myelopathy

Purpose: To compare the sagittal alignment of different surgical approaches in patients with multiple levels cervical spondylotic myelopathy and explore the relationship between the cervical sagittal alignment and patient’s health relative quality of life. Method: A total of 97 multiple levels cervical spondylotic myelopathy patients who underwent surgery from January 2013 to January 2019 were collected in this study. Patients were divided into three groups: anterior cervical discectomy with fusion, anterior cervical corpectomy with fusion and laminectomy with fusion groups. Clinical outcomes and sagittal alignment parameters were compared preoperative and postoperative. Results: There were no significant differences in the average age and sex ratio among the groups. Sagittal parameters correlated to health relative quality of life were C7 slope, occipito-C2 angle, external auditory meatus tilt and cervical sagittal vertical axis. Both anterior cervical discectomy with fusion and anterior cervical corpectomy with fusion groups exhibited better sagittal alignment and clinical outcomes improvement postoperatively. Anterior cervical discectomy with fusion provided better clinical outcomes and the better improvement of cervical lordosis, C7 slope, occipito-C2 angle and cervical sagittal vertical axis compared with patients with Laminectomy with fusion. Conclusion: C7 slope, occipito-C2 angle, external auditory meatus tilt and cervical sagittal vertical axis are the most important cervical sagittal parameters correlated to clinical outcomes in patients with multilevels cervical spondylotic myelopathy; anterior cervical discectomy with fusion and anterior cervical corpectomy with fusion provides more efficient to restoration of cervical sagittal alignment.

Comparison of different strategies on three-dimensional correction of AIS: which plane will suffer?

Purpose There are distinct differences in strategy amongst experienced surgeons from different ‘scoliosis schools’ around the world. This study aims to test the hypothesis that, due to the 3-D nature of AIS, different strategies can lead to different coronal, axial and sagittal curve correction. Methods Consecutive patients who underwent posterior scoliosis surgery for primary thoracic AIS were compared between three major scoliosis centres (n = 193). Patients were treated according to the local surgical expertise: Two centres perform primarily an axial apical derotation manoeuvre (centre 1: high implant density, convex rod first, centre 2: low implant density, concave rod first), whereas centre 3 performs posteromedial apical translation without active derotation. Pre- and postoperative shape of the main thoracic curve was analyzed using coronal curve angle, apical rotation and sagittal alignment parameters (pelvic incidence and tilt, T1–T12, T4-T12 and T10-L2 regional kyphosis angles, C7 slope and the level of the inflection point). In addition, the proximal junctional angle at follow-up was compared. Results Pre-operative coronal curve magnitudes were similar between the 3 cohorts and improved 75%, 70% and 59%, from pre- to postoperative, respectively (P < 0.001). The strategy of centres 1 and 2 leads to significantly more apical derotation. Despite similar postoperative T4-T12 kyphosis, the strategy in centre 1 led to more thoracolumbar lordosis and in centre 2 to a higher inflection point as compared to centre 3. Proximal junctional angle was higher in centres 1 and 2 (P < 0.001) at final follow-up. Conclusion Curve correction by derotation may lead to thoracolumbar lordosis and therefore higher risk for proximal junctional kyphosis. Focus on sagittal plane by posteromedial translation, however, results in more residual coronal and axial deformity.