Diagnostic Accuracy of Magnetic Resonance Imaging for Sagittal Cervical Spine Alignment: A Retrospective Cohort Study

(1) Background: Although radiography performed on the subject in an upright position is considered the standard method for assessing sagittal cervical alignment, it is frequently determined, or reported, based on MRI performed on the subject in a supine position. (2) Methods: Cervical alignment observed in both imaging modalities was assessed using four methods: the C2-7 Cobb angle, the absolute rotation angle (ARA), Borden’s method, and the sagittal vertical axis (SVA). Cervical alignment was determined (lordosis, kyphosis, and straight) based on radiography. Then, the diagnostic cut-off values for the MRI images and their corresponding diagnostic accuracies were assessed. (3) Results: The analysis included 142 outpatients. The determined diagnostic cut-off values for lordosis, using three measurements (Cobb angle, ARA, and Borden’s method), were −8.5°, −12.5°, and 3.5 mm, respectively, and the cut-off values for kyphosis were −4.5°, 0.5°, and −1.5 mm, respectively. The cut-off value for SVA > 40 mm was 19.5 mm. The Cobb angle, ARA, and Borden’s method, on MRI, showed high negative predictive values for determining kyphosis. The SVA on MRI measurements also showed high negative predictive values for determining >40 mm. (4) Conclusions: MRI measurements may be predictive of cervical alignment, especially for the exclusion of kyphosis and SVA > 40 mm. However, caution is needed in the other determinations using MRI, as their accuracies are limited.

When can we expect global sagittal alignment to reach a stable value following cervical deformity surgery?

OBJECTIVE Cervical deformity (CD) is a complex condition with a clear impact on patient quality of life, which can be improved with surgical treatment. Previous study following thoracolumbar surgery demonstrated a spontaneous and maintained improvement in cervical alignment following lumbar pedicle subtraction osteotomy (PSO). In this study the authors aimed to investigate the complementary questions of whether cervical alignment induces a change in global alignment and whether this change stabilizes over time. METHODS To analyze spontaneous changes, this study included only patients with at least 5 levels remaining unfused following surgery. After data were obtained for the entire cohort, repeated-measures analyses were conducted between preoperative baseline and 3-month and 1-year follow-ups with a post hoc analysis and Bonferroni correction. A subanalysis of patients with 2-year follow-up was performed. RESULTS One-year follow-up data were available for 121 of 168 patients (72%), and 89 patients had at least 5 levels remaining unfused following surgery. Preoperatively there was a moderate anterior cervical alignment (C2–7, −7.7° [kyphosis]; T1 slope minus cervical lordosis, 37.1°; cervical sagittal vertebral axis [cSVA], 37 mm) combined with a posterior global alignment (SVA, −8 mm) with lumbar hyperextension (pelvic incidence [PI] minus lumbar lordosis [LL] mismatch [PI-LL], −0.6°). Patients underwent a significant correction of the cervical alignment (median ΔC2–7, 13.6°). Simultaneously, PI-LL, T1 pelvic angle (TPA), and SVA increased significantly (all p < 0.05) between baseline and 3-month and 1-year follow-ups. Post hoc analysis demonstrated that all of the changes occurred between baseline and 3 months. Subanalysis of patients with complete 2-year follow-up demonstrated similar results, with stable postoperative thoracolumbar alignment achieved at 3 months. CONCLUSIONS Correction of cervical malalignment can have a significant impact on thoracolumbar regional and global alignment. Peak relaxation of compensatory mechanisms is achieved by the 3-month follow-up and tends to remain stable. Subanalysis with 2-year data further supports this finding. These findings can help to identify when the results of cervical surgery on global alignment can be best evaluated.

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.

Role of preoperative cervical alignment on postoperative dysphagia after occipitocervical fusion

Background: Dysphagia is one of the most serious complications of occipitocervical fusion (OCF). The previous studies have shown that postoperative cervical alignment, documented with occipito (O)-C2 angles, C2-C6 angles, and pharyngeal inlet angles (PIA), impacted the incidence of postoperative dysphagia in patients undergoing OCF. Here, we investigated the relationship of preoperative versus postoperative cervical alignment on the incidence of postoperative dysphagia after OCF. Methods: We retrospectively reviewed the clinical data/medical charts for 22 patients following OCF (2006– 2019). The O-C2 angles, C2-C6 angles, PIA, and narrowest pharyngeal airway spaces (nPAS) were assessed using plain lateral radiographs of the cervical spine before and after the surgery. The severity of dysphagia was assessed with the functional oral intake scale (FOIS) levels as documented in medical charts; based on this, patients were classified into the nondysphagia (FOIS: 7) versus dysphagia (FOIS: 1–6) groups. Results: Seven patients (35%) experienced dysphagia after OCF surgery. Preoperative PIA and nPAS were smaller in the dysphagia group. Spearman rank correlation showed a positive correlation between preoperative PIA and FOIS and between preoperative nPAS and FOIS. Conclusion: This study suggests that preoperative cervical alignment may best predict the incidence of postoperative dysphagia after OCF.