A novel classification that defines the normal cervical spine: an analysis based on 632 asymptomatic Chinese volunteers.

PURPOSE: The "normal" cervical spine may be non-lordotic shapes and the cervical spine alignment targets are less well established. So, the study was to propose novel classification for cervical spine morphologies with Chinese asymptomatic subjects, and to address cervical balance status based on the classification. METHOD: An overall 632 asymptomatic individuals on cervical spine were selected from January 2020 to December 2022, with six age groups from 20-30 year to 70 plus group. Cervical alignment contained C2-7 cervical lordosis (C2-7 CL) and T1 slope (T1S), together with C1-2 CL, C2-4 CL, C5-7 CL, C2S, cervical sagittal vertical axis (CSVA), thoracic inlet angle (TIA) and neck tilt (NT). C2-7 cervical lordosis was regarded as primary outcomes. To identify groups with similar cervical alignment parameters, a 2-step cluster analysis was performed. RESULTS: C2-7 CL, T1S, CSVA, TIA and NT increased by age and mean value of them were larger in male than female group. Four unique clusters of female lordotic cluster, female kyphotic cluster, male lordotic cluster and male kyphotic cluster were classified mainly based on gender and C2-C7 CL. T1S was the independent influencing factor for C2-7 CL in all individuals and C2-7 CL = -28.65 + 0.57 × TIA, which varied from clusters. Although interactions among cervical parameters, it showed the alignment was more coordinated in lordotic groups. CONCLUSIONS: The cervical sagittal profile varied with age and gender. Four clusters were naturally classified based on C2-7 CL and gender. The cervical balance status was addressed by C2-7 CL = - 28.65 + 0.57 × TIA.

Usefulness of the preoperative thoracic inlet angle in comparison to the T1 slope for predicting cervical kyphosis after laminoplasty.

PURPOSE: Thoracic inlet angle (TIA) is a sagittal radiographic parameter with a constant value regardless of posture and is significantly correlated with the sagittal balance of the cervical spine. However, the practical use of TIA has not been studied. This study aimed to investigate the usefulness of the preoperative TIA for predicting the development of kyphotic deformity after cervical laminoplasty in comparison to the preoperative T1 slope (T1S). METHODS: A total of 98 patients who underwent cervical laminoplasty without preoperative kyphotic alignment were included (mean age, 73.7 years; 41.8% female). Radiography was evaluated before surgery and at the 2-year follow-up examination. The cervical sagittal parameters were measured on standing radiographs, and the TIA was measured on T2-weighted MRI in a supine position. Cervical alignment with a C2-C7 angle of ≥ 0° was defined as lordosis, and that with an angle of < 0° was defined as kyphosis. RESULTS: Postoperative kyphosis occurred in 11 patients (11.2%). Preoperatively, the kyphosis group showed significantly lower values in the T1S (23.5° vs. 30.3°, p = 0.034) and TIA (76.1° vs. 81.8°, p = 0.042). We performed ROC curve analysis to clarify the impact of the preoperative TIA and T1S on kyphotic deformity after laminoplasty. The optimal cutoff angles for TIA and T1S were 68° and 19°, respectively, with similar diagnostic accuracy. CONCLUSION: This study demonstrated the clinical utility of the preoperative TIA for predicting the risk of postoperative kyphotic deformity after cervical laminoplasty. These findings suggest the importance of the preoperative assessment of thoracic inlet alignment in cervical spine surgery.

Factors related to T1 slope: spinopelvic balance and thoracic compensation.

OBJECTIVE: To identify factors associated with T1 slope (T1S). METHODS: A total of 215 patients over 18 years old who underwent whole-spine X-rays to evaluate lower back pain were enrolled in this study. T1S, pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), thoracic kyphosis (TK), lumbar lordosis (LL), cervical lordosis (CL), thoracolumbar kyphosis (TLK), and sagittal vertical axis (SVA) were measured. Patients were divided into balance, compensatory balance, thoracic compensation, and thoracic decompensation groups. RESULTS: TK (p < 0.001), SVA (p < 0.001), and CL (p = 0.020) were significantly related to high T1S. The balance group had the smallest PT, largest SS and largest LL of the four groups (p < 0.001). The thoracic compensation group had the smallest TK of all groups (p < 0.001). There was no significant difference in T1S between the balance and thoracic compensation groups (p = 0.099). The thoracic decompensation group had a larger T1S than the balance group (p = 0.023). CONCLUSIONS: Caudal spine segments had a sequential effect on cranial spine segments. T1S reflected the compensation ability of the spine. The absence of balance tended to increase the T1S. Pelvic posterior rotation and thoracic compensation were two crucial factors protecting against increased T1S in patients with ASD.

Mechanisms of compensatory for cervical lordosis changes after laminectomy with fusion.

BACKGROUND: The compensatory mechanisms for cervical lordosis change after laminectomy with fusion was not clear. The objective of this study was to evaluate the compensatory behaviors for cervical lordosis change after laminectomy with fusion. METHODS: This was a retrospective radiological analysis of 43 patients with cervical spondylotic myelopathy who underwent laminectomy with fusion (LCF). The following cervical parameters were measured: C2-7 Cobb angle (C2-7), occiput-C2 angle (O-C2), the cervical sagittal vertical axis (cSVA), and T1 slope (T1S). The difference was calculated for all angle parameters between the two time points using the following formula: the amount of change (Δ) = (value at the follow-up)-(preoperative value). Non-parametric tests and the t-test were used to compare the difference. The Pearson correlation test was performed, and stepwise multiple regression analysis was performed to determine the best correlation between ∆cSVA and ∆T1S. RESULTS: The mean age of 43 patients was 65.51 ± 9.80 years. All patients were classified into two subgroups based on ΔcSVA: Group M (maintained) and, Group I (increased). The preoperative O-C2, C2-7, T1S, and cSVA were similar between Group M and group I (p = 0.950, p = 0.731, p = 0.372, and p = 0.152, respectively). Postoperative O-C2 and postoperative cSVA were significantly different (p = 0.036 and p = 0.004, respectively). ∆O-C2, ∆T1S and ∆cSVA were significantly different between the two groups (p = 0.006, p = 0.000, and p = 0.000, respectively). ΔcSVA had significant correlations with ΔO-C2 neutral angle (r = 0.377) and ΔT1S (r = 0.582). A linear regression equation was established: ΔcSVA = 0.602 + 0.103 * ΔT1S (R = 0.582, R2 = 0.339). CONCLUSIONS: The decrease of TIS should be the first and foremost compensation for the loss of lordosis in C2-7 segments after LCF. When the change of T1S alone can not prevent the deterioration of cervical sagittal balance, further increases in the O-C2 segment occur.

The impact of age, sex, disc height loss and T1 slope on the upper and lower cervical lordosis: a large-scale radiologic study.

PURPOSE: To clarify the relative influence of age, sex, disc height loss and T1 slope on upper (Occiput-C2) and lower cervical lordosis (C2-C7). METHODS: Standing lateral cervical radiographs of 865 adult subjects were evaluated. The presence and severity of disc height loss from C2/C3 to C6/C7 (a total of 4325 discs) were assessed using a validated grading system. The total disc height loss score for each subject was calculated as the sum of the score of each disc space. Sagittal radiographic parameters included: occipital slope, occiput-C2 (Oc-C2) lordosis, C2-C7 lordosis and T1 slope. Multivariable regression analyses were performed to examine the relative influence of the multiple factors on upper and lower cervical lordosis. RESULTS: This study included 360 males and 505 females, with a mean age of 40.2 ± 16.0 years (range, 20-95 years). Linear multivariate regression analyses showed that greater age, male sex, greater T1 slope were each found to be significantly and independently associated with greater C2-C7 lordosis, whereas total disc height loss score was negatively associated with C2-C7 lordosis. T1 slope had the most independent influence on C2-C7 lordosis among these factors. Age, sex and disc height loss were not independently associated with Oc-C2 lordosis. CONCLUSIONS: Results from our large-scale radiologic analysis may enhance the understanding of the factors that affect cervical lordosis, indicating that age, sex, disc height loss and T1 slope were each independently associated with C2-C7 lordosis. However, age, sex and disc height loss were not independently associated with upper cervical lordosis.

Sagittal balance of the cervical spine: a systematic review and meta-analysis.

PURPOSE: The purpose of this systematic review and meta-analysis was to compare the cervical sagittal parameters between patients with cervical spine disorder and asymptomatic controls. METHODS: Two independent authors systematically searched online databases including Pubmed, Scopus, Cochrane library, and Web of Science up to June 2020. Cervical sagittal balance parameters, such as T1 slope, cervical SVA (cSVA), and spine cranial angle (SCA), were compared between the cervical spine in healthy, symptomatic, and pre-operative participants. Where possible, we pooled data using random-effects meta-analysis, by CMA software. Heterogeneity and publication bias were assessed using the I-squared statistic and funnel plots, respectively. RESULTS: A total of 102 studies, comprising 13,802 cases (52.7% female), were included in this meta-analysis. We used the Newcastle-Ottawa Scale (NOS) to evaluate the quality of studies included in this review. Funnel plot and Begg's test did not indicate obvious publication bias. The pooled analysis reveals that the mean (SD) values were: T1 slope (degree), 24.5 (0.98), 25.7 (0.99), 25.4 (0.34); cSVA (mm), 18.7 (1.76), 22.7 (0.66), 22.4 (0.68) for healthy population, symptomatic, and pre-operative assessment, respectively. The mean value of the SCA (degree) was 79.5 (3.55) and 75.6 (10.3) for healthy and symptomatic groups, respectively. Statistical differences were observed between the groups (all P values < 0.001). CONCLUSION: The findings showed that the T1 slope and the cSVA were significantly lower among patients with cervical spine disorder compared to controls and higher for the SCA. Further well-conducted studies are needed to complement our findings.

Increased Neck Tilt/T1 slope ratio may play an important role in patients with cervical kyphosis.

BACKGROUND: In previous studies, we demonstrated that the T1 slope (T1s) is associated with clinical outcomes, but the results were not specific for individuals. A recent study suggested that an increased pelvic tilt (PT)/sacral slope (SS) ratio may play an important role in the degeneration of lumbar scoliosis and pathogenesis of lumbar spondylolisthesis. Therefore, we aimed to explore the role of neck tilt (NT)/T1s in patients with cervical kyphosis. METHODS: In total, the data of 36 kyphosis patients who underwent anterior cervical hybrid decompression and fusion (ACHDF) for multilevel (3 levels) cervical spondylotic myelopathy were retrospectively analyzed. The radiographic measurements included the T1s, NT, C2-7 Cobb angle, and C2-7 sagittal vertical axis (SVA). The visual analog scale (VAS) and neck disability index (NDI) scores were used to determine the clinical prognosis. Pearson's correlation coefficient was calculated to assess the relationships among preoperative imaging examination parameters. RESULTS: The mean C2-7 Cobb angle was - 5.93 ± 3.00° before surgery, 9.67 ± 6.61° after surgery, and 7.91 ± 8.73° at the follow-up. The preoperative NT/T1s ratio was positively correlated with the ΔC2-7 Cobb angle (r = 0.358, p < 0.05) and negatively correlated with the preoperative C2-7 Cobb angle (r = -0.515, p < 0.01) and preoperative C2-7 SVA (r = -0.461, p < 0.01). The linear regression model indicated a positive correlation between the preoperative NT/T1s ratio and the ΔC2-7 Cobb angle (R2 = 0.122). CONCLUSIONS: The preoperative NT/T1s ratio may be positively correlated with changes in postoperative cervical spine curvature (Cobb angle). The NT/T1s ratio may be worthy of increased attention among sagittal parameters.

Cervical sagittal alignment after Prestige LP cervical disc replacement: radiological results and clinical impacts from a single-center experience.

BACKGROUND: Cervical disc replacement (CDR) has been widely used to treat one- and two-level cervical degenerative disc disease. Studies have shown the effectiveness of CDR in preserving range of motion (ROM) and delaying adjacent segment degeneration (ASD). Cervical sagittal alignment is an important factor affecting favorable clinical outcomes in cervical spine surgery. This study aimed to explore whether cervical sagittal alignment can be maintained after CDR and to identify the impact of cervical sagittal alignment on outcomes after CDR. METHODS: This was a single-center, retrospective study. 132 patients who underwent one-level CDR were included. Cervical sagittal alignments, including cervical lordosis (CL), segmental alignment (SA), sagittal vertical axis (SVA), T1 slope (T1s), and T1s minus CL (T1s-CL), were measured. The effects of cervical sagittal alignment on the CDR outcomes were analyzed. Patients were divided into the heterotopic ossification (HO) group and ASD group to determine the potential impacts of cervical sagittal parameters. RESULTS: The cervical sagittal alignment parameters, except for the SVA, were significantly improved after CDR and showed decreasing trends at the last follow-up. Significantly higher CL and T1s were found in patients with better ROM after CDR. SVA ≥ 20 mm increased the risk of anterior HO (odds ratio = 2.945, P = 0.007). Significantly kyphotic SA and lower T1s values were found in the ASD patients than in the non-ASD patients (P < 0.05). Patients with ASD at the inferior level showed significantly worse CL (P < 0.05). CONCLUSION: CDR had limited function of improving cervical sagittal alignment. Poor cervical sagittal alignment after CDR was associated with HO, ASD, and less ROM.

Radiographic predictive findings of neck pain in patients with ankylosing spondylitis.

OBJECTIVE: The aim of this study was to investigate the relationship between neck pain and radiological findings in ankylosing spondylitis (AS) patients. METHODS: The study groups comprised 257 AS and 50 normal patients. Of the AS patients, 91 had axial neck pain (group 1) and 166 did not (group 2). Full-length radiographs of the spine in the anteroposterior and lateral planes were taken. Radiographic parameters such as the chin brow vertical angle (CBVA), McGregor slope (McGS), slope of the Line of Sight (SLS), C2 slope, C2-C7 lordosis (CL), C2-C7 sagittal vertical axis (C2-C7 SVA), and T1 slope were measured. Statistical analysis was performed. RESULTS: The AS and normal patients were found to have significantly different CBVA, McGS, C2 slope, C2-C7 SVA, and T1 slope. However, no significant difference was observed for SLS and CL. Between groups 1 and 2, there were significant differences in the McGS, CL, and T1 slope. However, no significant difference between these two groups was observed for CBVA, SLS, C2 slope, and C2-C7 SVA. Logistic regression analysis was performed to identify statistically significant predictors of neck pain in AS patients and it revealed that the T1 slope and McGS were two such predictors. The T1 slope showed superior discriminatory power to McGS and CL in the receiver operating characteristic curve analysis. CONCLUSIONS: This study shows that a high T1 slope and McGS are independent radiological predictors of neck pain in AS. Further well-designed studies would be necessary to substantiate our results.

The association of cervical sagittal alignment with adjacent segment degeneration.

PURPOSE: Cervical spine surgery may affect sagittal alignment parameters and induce accelerated degeneration of the cervical spine. Cervical sagittal alignment parameters of surgical patients will be correlated with radiological adjacent segment degeneration (ASD) and with clinical outcome parameters. METHODS: Patients were analysed from two randomized, double-blinded trials comparing anterior cervical discectomy with arthroplasty (ACDA), with intervertebral cage (ACDF) and without intervertebral cage (ACD). C2-C7 lordosis, T1 slope, C2-C7 sagittal vertical axis (SVA) and the occipito-cervical angle (OCI) were determined as cervical sagittal alignment parameters. Radiological ASD was scored by the combination of decrease in disc height and anterior osteophyte formation. Neck disability index (NDI), SF-36 PCS and MCS were evaluated as clinical outcomes. RESULTS: The cervical sagittal alignment parameters were comparable between the three treatment groups, both at baseline and at 2-year follow-up. Irrespective of surgical method, C2-C7 lordosis was found to increase from 11° to 13°, but the other parameters remained stable during follow-up. Only the OCI was demonstrated to be associated with the presence and positive progression of radiological ASD, both at baseline and at 2-year follow-up. NDI, SF-36 PCS and MCS were demonstrated not to be correlated with cervical sagittal alignment. Likewise, a correlation with the value or change of the OCI was absent. CONCLUSION: OCI, an important factor to maintain horizontal gaze, was demonstrated to be associated with radiological ASD, suggesting that the occipito-cervical angle influences accelerated cervical degeneration. Since OCI did not change after surgery, degeneration of the cervical spine may be predicted by the value of OCI. NECK TRIAL: Dutch Trial Register Number NTR1289. PROCON TRIAL: Trial Register Number ISRCTN41681847. These slides can be retrieved under Electronic Supplementary Material.

Relationship between the atlantodental interval and T1 slope after atlantoaxial fusion in patients with rheumatoid arthritis.

BACKGROUND: Atlantoaxial fusion has been widely used for the treatment of atlantoaxial instability (AAI). However, atlantoaxial fusion sacrifices the motion of atlantoaxial articulation, and postoperative loss of cervical lordosis and aggravation of cervical kyphosis are observed. We investigated various factors under the hypothesis that the atlantodental interval (ADI) and T1 slope may be associated with sagittal alignment after atlantoaxial fusion in patients with rheumatoid arthritis (RA). METHODS: We retrospectively investigated 64 patients with RA who underwent atlantoaxial fusion due to AAI. Radiological factors, including the ADI, T1 slope, Oc-C2 angle, cervical sagittal vertical axis, and C2-C7 angle, were measured before and after surgery. RESULTS: The various factors associated with atlantoaxial fusion before and after surgery were compared according to the upper and lower preoperative ADIs. There was a significant difference in the T1 slope 1 year after surgery (p = 0.044) among the patients with lower preoperative ADI values. The multivariate logistic regression analysis showed that the preoperative ADI (> 7.92 mm) defined in the receiver-operating characteristic curve analysis was an independent predictive factor for the increase in the T1 slope 1 year after atlantoaxial fusion (odds ratio, 4.59; 95% confidence interval, 1.34-15.73; p = 0.015). CONCLUSION: We found an association between the preoperative ADI and difference in the T1 slope after atlantoaxial fusion in the patients with RA. A preoperative ADI (> 7.92 mm) was an independent predictor for the increase in the T1 slope after atlantoaxial fusion. Therefore, performing surgical treatment when the ADI is low would lead to better cervical sagittal alignment.

Radiographic analysis of the correlation between ossification of the nuchal ligament and sagittal alignment and segmental stability of the cervical spine in patients with cervical spondylotic myelopathy.

BACKGROUND: Ossification of the nuchal ligament (ONL) caused by chronic injury to the nuchal ligament (NL) is very common in instability-related cervical disorders. PURPOSE: To determine possible correlations between ONL, sagittal alignment, and segmental stability of the cervical spine. MATERIAL AND METHODS: Seventy-three patients with cervical spondylotic myelopathy (CSM) and ONL (ONL group) and 118 patients with CSM only (control group) were recruited. Radiographic data included the characteristics of ONL, sagittal alignment and segmental stability, and ossification of the posterior longitudinal ligament (OPLL). We performed comparisons in terms of radiographic parameters between the ONL and control groups. The correlations between ONL size, cervical sagittal alignment, and segmental stability were analyzed. Multivariate logistic regression was used to identify the independent risk factors of the development of ONL. RESULTS: C2-C7 sagittal vertical axis (SVA), T1 slope (T1S), T1S minus cervical lordosis (T1S-CL) on the lateral plain, angular displacement (AD), and horizontal displacement (HD) on the dynamic radiograph increased significantly in the ONL group compared with the control group. The size of ONL significantly correlated with C2-C7 SVA, T1S, AD, and HD. The incidence of ONL was higher in patients with OPLL and segmental instability. Cervical instability, sagittal malalignment, and OPLL were independent predictors of the development of ONL through multivariate analysis. CONCLUSION: Patients with ONL are more likely to have abnormal sagittal alignment and instability of the cervical spine. Thus, increased awareness and appreciation of this often-overlooked radiographic finding is warranted during diagnosis and treatment of instability-related cervical pathologies and injuries.

Analysis of sagittal alignment parameters following anterior cervical hybrid decompression and fusion of multilevel cervical Spondylotic myelopathy.

BACKGROUND: To investigate the relationships between sagittal parameters and health-related quality of life (HRQOL) scores following anterior cervical hybrid decompression and fusion (ACHDF) of multilevel cervical spondylotic myelopathy (CSM) and to study the impact of the T1 slope (T1 s). METHODS: In total, 42 patients with complete radiographic measurements following ACHDF in the Spine Surgery Department of the First Affiliated Hospital of Fujian Medical University from August 2014 to January 2017 were retrospectively analysed. Radiographic measurements included C2-7 lordosis, T1 s, C2-7 sagittal vertical axis (SVA), cervical tilting and cranial tilting. The neck disability index (NDI) was used to evaluate the HRQOL. Spearman's correlation coefficients were calculated between pairs of cervical sagittal parameters and NDI scores. RESULTS: Preoperative NDI scores were correlated with preoperative T1 s (r = 0.413); follow-up NDI scores were correlated with follow-up T1 s (r = 0.534). The regression analysis indicated that a preoperative T1 s value of 42.36° corresponded to a preoperative NDI score of 25 (r2 = 0.171, P < 0.001). A follow-up T1 s value of 48.61° corresponded to a follow-up NDI score of 25 (r2 = 0.421, P < 0.01). The differences in C2-7 SVA and cranial tilting before and after the operation were statistically significant (P < 0.05). CONCLUSION: This study showed that the sagittal balance of the cervical vertebrae changed significantly after ACHDF, showing a forward trend. The sagittal parameters after ACHDF were related to clinical prognosis. An excessive T1 s can be considered a risk factor. The T1 s could provide a reference value to determine the correction of the sagittal balance of the cervical spine.

K-line tilt as a novel radiographic parameter in cervical sagittal alignment.

OBJECTIVE: To investigate the relationship between the K-line tilt and classical cervical parameters such as the C2-C7 sagittal vertical axis (SVA), cervical lordosis, and the T1 slope in cervical sagittal alignment. We assessed whether the K-line tilt can be used as an excellent cervical parameter. METHODS: We reviewed 50 patients aged 60-89 years who visited the spine center outpatient clinic from May 2017 to September 2017 through cervical spine lateral radiography and checked the cervical spine parameters. All targeted patients were randomized without any prejudice. Radiographic measurements included the K-line tilt, C2-C7 lordosis, the C2-C7 SVA, the T1 slope, and T1 slope minus C2-C7 lordosis (T1S-CL). Pearson correlation coefficients were calculated between the K-line tilt and each cervical parameter. RESULTS: Of the 50 patients, 33 were men. The mean age of the patients was 70.84 ± 7.52 years. The mean K-line tilt was 11.28 ± 8.31°. The K-line tilt was correlated with the C2-C7 SVA (r = 0.813, P = 0.000) and T1S-CL (r = 0.315, P = 0.026). CONCLUSION: This study showed that the K-line tilt is also a useful parameter like the C2-C7 SVA and T1S-CL in cervical sagittal alignment. These slides can be retrieved under Electronic Supplementary Material.

Which parameters are relevant in sagittal balance analysis of the cervical spine? A literature review.

INTRODUCTION: Cervical spine is part of the spine with the most mobility in the sagittal plane. It is important for surgeons to have reliable, simple and reproducible parameters to analyse the cervical. MATERIAL AND METHOD: This study is a systematic review and a critique of current parameters to help improve the study of cervical spinal balance. We conducted a systematic search of PUBMED/MEDLINE for literature published since January 2014. Only studies written in English and containing abstracts were considered for inclusion. The search performed was: «C7 slope¼ OR «T1 slope¼ OR «C2C7 offset¼ OR «C2C7 lordosis¼ OR «cervical SVA (sagittal vertical axis)¼ OR «TIA (thoracic inlet angle)¼ (Lee et al., J Spinal Disord Tech 25(2):E41-E47, 2012) OR «SCA (spino-cranial angle)¼. Exclusion criteria were purely post-operative and cadaveric analysis, studies performed with CT scan or MRI, studies on adolescent idiopathic scoliosis, traumatology studies and no standing analysis of the cervical spine. Relevance was confirmed by investigators if cervical parameters was a major criteria of the study. RESULTS: 138 articles were found by the electronic search. After complete evaluation 20 articles were selected. The large majority of papers used the same parameters C2_C7 lordosis, C2-C7 SVA, T1 slope or C7 slope and T1 slope/cervical lordosis mismatch. Janusz reported a new parameter using a retrospective cohort of patient with cervical radiculopathy: the TIA (thoracic inlet angle). Le Huec reported an other new parameter based on a prospective study of asymptomatic volunteer: the spino-cranial angle (SCA). This parameter is highly correlated with the C7 slope and the cervical lordosis. Other studies reported parameters that are more global balance analysis including the cervical spine than cervical spine balance itself. CONCLUSION: The most important parameters to analyse the cervical sagittal balance according to the literature available today for good clinical outcomes are the following: C7 or T1 slope, average value 20°, must not be higher than 40°. cSVA must not be less than 40°C (mean value 20 mm). SCA (spine cranial angle) must stay in a norm (83° ± 9°). Future studies should focus on those three parameters to analyse and compare pre and post op data and to correlate the results with the quality of life improvement.

MRI kinematic analysis of T1 sagittal motion between cervical flexion and extension positions in 145 patients.

PURPOSE: Although the T1 vertebra is considered as an important factor of cervical balance, little is known about its motion between flexion and extension. The purpose of present study was to analyze the T1 sagittal motion using kinematic magnetic resonance imaging (kMRI), and to identify factors that relate to T1 sagittal motion. METHODS: We retrospectively analyzed 145 kMR images taken in weight-bearing neutral, flexion and extension positions. Cervical balance parameters were evaluated in each position. The degree of T1 sagittal motion was defined as [(T1 slope at extension) - (T1 slope at flexion)]. All patients were divided into three groups: Positive group (T1 followed the head motion, T1 sagittal motion > 5°), Stable group (5 ≥, ≥ - 5) and Negative group (T1 moved in the opposite direction from the head motion, > - 5). The groups were compared and multivariate logistic regression analysis was calculated. RESULTS: There were 57 (40%) patients in the positive, 56 (39%) in the stable and 32 (22%) in the negative group. The positive group had the largest C2-7 sagittal vertical axis in flexion (p < 0.001) and the shortest in the extension (p = 0.023). Similar trends were seen in cranial tilt and cervical tilt. The value of T1 height < 27 mm was a significant independent factor for the negative group (p = 0.008, adjusted odds ratio = 5.958). CONCLUSION: Based on T1 sagittal motion, 40% of the patients were classified in positive group (the T1 vertebra followed the head motion in flexion and extension), and 20% were classified in the negative group (the T1 vertebra moved in the opposite direction from the head motion). T1 height < 27 mm was a potential predictor of negative group.

Cervical sagittal balance: a biomechanical perspective can help clinical practice.

PURPOSE: In this article, we summarize our work on understanding the influence of cervical sagittal malalignment on the mechanics of the cervical spine. METHODS: Biomechanical studies were performed using an ex vivo laboratory model to study the kinematic and kinetic response of human cervical spine specimens in the setting of cervical sagittal imbalance. The model allowed controlled variations of C2-C7 Sagittal Vertical Alignment (C2-C7 SVA) and T1-Slope so that clinically relevant sagittally malaligned profiles could be prescribed, while maintaining horizontal gaze, and their biomechanical consequences studied. RESULTS: Our results demonstrated that increasing C2-C7 SVA caused flexion of lower cervical (C2-C7) segments and hyperextension of suboccipital (C0-C1-C2) segments to maintain horizontal gaze. An increase in C2-C7 SVA increased the lower cervical neural foraminal areas. Conversely, increasing T1-slope predominantly influenced subaxial cervical lordosis and, as a result, decreased cervical neural foraminal areas. Therefore, we believe patients with increased upper thoracic kyphosis and radicular symptoms may respond with increased forward head posture (FHP) as a compensatory mechanism to increase their lower cervical neural foraminal area and alleviate nerve root compression as well as reduce the burden on posterior muscles and soft and bony structures of the cervical spine. Increasing FHP (i.e., increased C2-C7 SVA) was associated with shortening of the cervical flexors and occipital extensors and lengthening of the cervical extensors and occipital flexors, which corresponds to C2-C7 flexion and C0-C2 extension. The greatest shortening occurred in the suboccipital muscles, suggesting considerable load bearing of these muscles during chronic FHP. Regardless, there was no evidence of nerve compression within the suboccipital triangle. Finally, cervical sagittal imbalance may play a role in exacerbating adjacent segment pathomechanics after multilevel cervical fusion and should be considered during surgical planning. CONCLUSIONS: The results of our biomechanical studies have improved our understanding of the impact of cervical sagittal malalignment on pathomechanics of the cervical spine. We believe this improved understanding will assist in clinical decision-making.

Characteristics of cervical sagittal parameters in healthy cervical spine adults and patients with cervical disc degeneration.

BACKGROUND: The cervical sagittal parameters of the normal population and the impact of disc degeneration on cervical sagittal alignment have not been clearly defined yet. This study is applied to investigate the characteristics and relationships of cervical sagittal parameters in normal adults and patients with cervical disc degeneration. METHODS: We reviewed 50 normal control subjects (normal group, NG) and 50 patients with cervical disc degeneration (degeneration group, DG), who had both cervical MRI and radiographs obtained together, between January 2010 and September 2015. Data including C2-7 lordosis (CL), T1 slope (T1S), thoracic inlet angle (TIA), neck tilt (NT), C2-7 sagittal vertical axis (C2-7 SVA), cervical tilting, and cranial tilting on cervical radiographs were collected and analyzed. RESULTS: T1S in the NG was significantly greater than in the DG (P < 0.05), while NT and C2-7 SVA in the NG were significantly lower than in the DG (P < 0.01 and P < 0.05, respectively). T1S positively correlated with CL in both groups (Pearson correlation coefficients of 0.588 in the NG and 0.504 in the DG). No significant difference was seen in TIA between the NG and DG. CONCLUSIONS: T1S was involved in the occurrence and development of cervical disc degeneration, and TIA could be considered as a constant morphological parameter in both the normal population and cervical disc degeneration patients.

Analysis of cervical sagittal alignment change following correction of thoracic and thoracolumbar Scheuermann's kyphosis.

PURPOSE: To analyse pre-operative and post-operative changes of cervical sagittal alignment (CSA) in Scheuermann's kyphosis (SK) patients. METHODS: 64 SK and 33 control patients were retrospectively reviewed. Whole spine X-rays obtained at pre-op, 3 months post-op and at latest follow-up were reviewed and ten separate CSA radiological parameters were measured. Patients were divided in three groups: thoracic SK (TK group, apex T6-T9, n = 40), thoracolumbar SK (TLK group, apex T10-T12, n = 24), and controls. RESULTS: Pre-operative C2-C7 lordosis was 21.1° ± 8.1°(TK), 6.1° ± 5.0°(TLK), and 11.4° ± 8.3° in control group and correlated significantly with T1 slope in both SK groups (r = 0.640, r = 0.772). Pre-operative T1 slope was dependent on deformity type, thoracic kyphosis (TK, ß = 0.445), and lumbar lordosis (LL, ß = -0.354). At final follow-up C2-C7 lordosis decreased to 15.7° ± 5.5° in TK, and increased to 12.1° ± 4.1° in TLK group. C2-C7 lordosis changes linearly correlated with T1 slope changes post-operatively (r = 0.721). Post-operative T1 slope showed linear correlation with post-operative changes in TK (ß = 0.728) and pelvic tilt (PT, ß = 0.539) in TK, and LL (ß = -0.669), thoracolumbar kyphosis (TLK, ß = -0.434), and PT (ß = 0.760) in TLK group. CONCLUSIONS: Our study suggests that SK is not a homogenous group of patients. Two patterns of pre- and post-operative CSA are demonstrated in TK and TLK groups. T1 slope is the most important parameter in determining pre-operative CSA and correlates with other regional anatomical parameters (TK and LL). Post-operative CSA adaptations also correlate with T1 slope post-operative changes. However, post-surgical T1 slope correlates with different parameters in the two SK groups (TK and PT in TK group; TLK, LL, and PT in TLK group).

Despite worse baseline status depressed patients achieved outcomes similar to those in nondepressed patients after surgery for cervical deformity.

OBJECTIVE Depression and anxiety have been demonstrated to have negative impacts on outcomes after spine surgery. In patients with cervical deformity (CD), the psychological and physiological burdens of the disease may overlap without clear boundaries. While surgery has a proven record of bringing about significant pain relief and decreased disability, the impact of depression and anxiety on recovery from cervical deformity corrective surgery has not been previously reported on in the literature. The purpose of the present study was to determine the effect of depression and anxiety on patients' recovery from and improvement after CD surgery. METHODS The authors conducted a retrospective review of a prospective, multicenter CD database. Patients with a history of clinical depression, in addition to those with current self-reported anxiety or depression, were defined as depressed (D group). The D group was compared with nondepressed patients (ND group) with a similar baseline deformity determined by propensity score matching of the cervical sagittal vertical axis (cSVA). Baseline demographic, comorbidity, clinical, and radiographic data were compared among patients using t-tests. Improvement of symptoms was recorded at 3 months, 6 months, and 1 year postoperatively. All health-related quality of life (HRQOL) scores collected at these follow-up time points were compared using t-tests. RESULTS Sixty-six patients were matched for baseline radiographic parameters: 33 with a history of depression and/or current depression, and 33 without. Depressed patients had similar age, sex, race, and radiographic alignment: cSVA, T-1 slope minus C2-7 lordosis, SVA, and T-1 pelvic angle (p > 0.05). Compared with nondepressed individuals, depressed patients had a higher incidence of osteoporosis (21.2% vs 3.2%, p = 0.028), rheumatoid arthritis (18.2% vs 3.2%, p = 0.012), and connective tissue disorders (18.2% vs 3.2%, p = 0.012). At baseline, the D group had greater neck pain (7.9 of 10 vs 6.6 on a Numeric Rating Scale [NRS], p = 0.015), lower mean EQ-5D scores (68.9 vs 74.7, p < 0.001), but similar Neck Disability Index (NDI) scores (57.5 vs 49.9, p = 0.063) and myelopathy scores (13.4 vs 13.9, p = 0.546). Surgeries performed in either group were similar in terms of number of levels fused, osteotomies performed, and correction achieved (baseline to 3-month measurements) (p < 0.05). At 3 months, EQ-5D scores remained lower in the D group (74.0 vs 78.2, p = 0.044), and NDI scores were similar (48.5 vs 39.0, p = 0.053). However, neck pain improved in the D group (NRS score of 5.0 vs 4.3, p = 0.331), and modified Japanese Orthopaedic Association (mJOA) scores remained similar (14.2 vs 15.0, p = 0.211). At 6 months and 1 year, all HRQOL scores were similar between the 2 cohorts. One-year measurements were as follows: NDI 39.7 vs 40.7 (p = 0.878), NRS neck pain score of 4.1 vs 5.0 (p = 0.326), EQ-5D score of 77.1 vs 78.2 (p = 0.646), and mJOA score of 14.0 vs 14.2 (p = 0.835). Anxiety/depression levels reported on the EQ-5D scale were significantly higher in the depressed cohort at baseline, 3 months, and 6 months (all p < 0.05), but were similar between groups at 1 year postoperatively (1.72 vs 1.53, p = 0.416). CONCLUSIONS Clinical depression was observed in many of the study patients with CD. After matching for baseline deformity, depression symptomology resulted in worse baseline EQ-5D and pain scores. Despite these baseline differences, both cohorts achieved similar results in all HRQOL assessments 6 months and 1 year postoperatively, demonstrating no clinical impact of depression on recovery up until 1 year after CD surgery. Thus, a history of depression does not appear to have an impact on recovery from CD surgery.