A comparative analysis of the prevalence and characteristics of cervical malalignment in adults presenting with thoracolumbar spine deformity based on variations in treatment approach over 2 years

Impact of Growing Rod Surgery for Early-Onset Scoliosis on Cervical Sagittal Alignment

Study Design

Single-institution retrospective study.

Objective

To assess the impact of growing rods (GRs) on postoperative cervical sagittal alignment in patients with early-onset scoliosis (EOS).

Summary of Background Data

Cervical sagittal malalignment is associated with neck and cervical spine dysfunction. The impact of surgery for adolescent idiopathic scoliosis on postoperative changes in cervical spine alignment has been reported by studies. Nevertheless, research on sagittal and spinopelvic parameters in patients with EOS is limited.

Methods

In this study, 28 patients who underwent GR and were followed up until final fusion or bone maturity were included. Standing whole-spine radiographs obtained before GR, after the initial GR surgery, and at the final follow-up were utilized to measure the radiographic parameters. Patients with one or more of the previously reported poor prognostic factors were included in the cervical malalignment (CM) group (n=13), and those with none of the factors were included in the non-CM group (n=15) at the final follow-up, which was followed by correlation analysis and multivariate logistic regression analysis.

Results

No significant change in sagittal alignment between preoperative and final follow-up measurements was found. Pearson correlation analysis revealed a significant positive correlation between the change in the C2-7 angle and T1 slope (T1S) or thoracic kyphosis and a negative correlation between the change in the C2-7 angle and T1S minus C2-7 angle (T1S-CL). The percentage of patients in the CM group increased from 25% preoperatively to 46% at the final follow-up but without significant change. The CM group had significantly smaller preoperative C2-7 angles and lumbar lordosis (LL) and larger T1S-CL and pelvic incidence minus LL (PI-LL) values than the non-CM group.

Conclusion

Smaller preoperative C2-7 angles and larger T1S-CL values were identified as risk factors for CM. Postoperative CM is more likely to occur in patients with reduced compensatory function to maintain preoperative cervical kyphosis.

Machine learning analysis of cervical balance in early-onset scoliosis post-growing rod surgery: a case-control study

We aimed to analyze the cervical sagittal alignment change following the growing rod treatment in early-onset scoliosis (EOS) and identify the risk factors of sagittal cervical imbalance after growing-rod surgery of machine learning. EOS patients from our centre between 2007 and 2019 were retrospectively reviewed. Radiographic parameters include the cervical lordosis (CL), T1 slope, C2-C7 sagittal vertical axis (C2-7 SVA), primary curve Cobb angle, thoracic kyphosis (TK), C7-S1 sagittal vertical axis (C7-S1 SVA) and proximal junctional angle (PJA) were evaluated preoperatively, postoperatively and at the final follow-up. The parameters were analyzed using a t-test and χ2 test. The machine learning methodology of a sparse additive machine (SAM) was applied to identify the risk factors that caused the cervical imbalance. 138 patients were enrolled in this study (96 male and 42 female). The mean thoracic curve Cobb angle was 67.00 ± 22.74°. The mean age at the first operation was 8.5 ± 2.6yrs. The mean follow-up was 38.48 ± 10.87 months. CL, T1 slope, and C2-7 SVA increased significantly in the final follow-up compared with the pre-operative data. (P < 0.05). The CL and T1 slope increased more significantly in the group of patients who had proximal junctional kyphosis (PJK) compared with the patients without PJK (P < 0.05). The location of the upper instrumented vertebrae (UIV) and single/dual growing rod had no significant influence on the sagittal cervical parameters (P > 0.05). According to the SAM analysis of machine learning algorithms, Postoperative PJK, more improvement of kyphosis, and T1 slope angle were identified as the risk factors of cervical sagittal imbalance during the treatment of growing rod surgery. The growing rod surgery in EOS significantly affected the cervical sagittal alignment. Postoperative PJK and more improvement of kyphosis and T1 slope angle would lead to a higher incidence of cervical sagittal imbalance.

Sagittal balance parameters measurement on cervical spine MR images based on superpixel segmentation

Introduction: Magnetic Resonance Imaging (MRI) is essential in diagnosing cervical spondylosis, providing detailed visualization of osseous and soft tissue structures in the cervical spine. However, manual measurements hinder the assessment of cervical spine sagittal balance, leading to time-consuming and error-prone processes. This study presents the Pyramid DBSCAN Simple Linear Iterative Cluster (PDB-SLIC), an automated segmentation algorithm for vertebral bodies in T2-weighted MR images, aiming to streamline sagittal balance assessment for spinal surgeons. Method: PDB-SLIC combines the SLIC superpixel segmentation algorithm with DBSCAN clustering and underwent rigorous testing using an extensive dataset of T2-weighted mid-sagittal MR images from 4,258 patients across ten hospitals in China. The efficacy of PDB-SLIC was compared against other algorithms and networks in terms of superpixel segmentation quality and vertebral body segmentation accuracy. Validation included a comparative analysis of manual and automated measurements of cervical sagittal parameters and scrutiny of PDB-SLIC's measurement stability across diverse hospital settings and MR scanning machines. Result: PDB-SLIC outperforms other algorithms in vertebral body segmentation quality, with high accuracy, recall, and Jaccard index. Minimal error deviation was observed compared to manual measurements, with correlation coefficients exceeding 95%. PDB-SLIC demonstrated commendable performance in processing cervical spine T2-weighted MR images from various hospital settings, MRI machines, and patient demographics. Discussion: The PDB-SLIC algorithm emerges as an accurate, objective, and efficient tool for evaluating cervical spine sagittal balance, providing valuable assistance to spinal surgeons in preoperative assessment, surgical strategy formulation, and prognostic inference. Additionally, it facilitates comprehensive measurement of sagittal balance parameters across diverse patient cohorts, contributing to the establishment of normative standards for cervical spine MR imaging.

Adult cervical spine deformity: a state-of-the-art review

Adult cervical deformity is a structural malalignment of the cervical spine that may present with variety of significant symptomatology for patients. There are clear and substantial negative impacts of cervical spine deformity, including the increased burden of pain, limited mobility and functionality, and interference with patients' ability to work and perform everyday tasks. Primary cervical deformities develop as the result of a multitude of different etiologies, changing the normal mechanics and structure of the cervical region. In particular, degeneration of the cervical spine, inflammatory arthritides and neuromuscular changes are significant players in the development of disease. Additionally, cervical deformities, sometimes iatrogenically, may present secondary to malalignment or correction of the thoracic, lumbar or sacropelvic spine. Previously, classification systems were developed to help quantify disease burden and influence management of thoracic and lumbar spine deformities. Following up on these works and based on the relationship between the cervical and distal spine, Ames-ISSG developed a framework for a standardized tool for characterizing and quantifying cervical spine deformities. When surgical intervention is required to correct a cervical deformity, there are advantages and disadvantages to both anterior and posterior approaches. A stepwise approach may minimize the drawbacks of either an anterior or posterior approach alone, and patients should have a surgical plan tailored specifically to their cervical deformity based upon symptomatic and radiographic indications. This state-of-the-art review is based upon a comprehensive overview of literature seeking to highlight the normal cervical spine, etiologies of cervical deformity, current classification systems, and key surgical techniques.

Cervical Sagittal Balance: Impact on Clinical Outcomes and Subsidence in Anterior Cervical Discectomy and Fusion

Degenerative disease of the cervical spine leads to sagittal imbalance, which may affect treatment results. The purpose of this study was to evaluate changes in selected cervical sagittal balance parameters and their effects on subsidence and clinical outcomes of the procedure. This study encompassed a total of 95 evaluated patients who underwent anterior cervical discectomy and fusion (ACDF). Selected cervical sagittal balance parameters were assessed using lateral projection X-rays: C2-C7 spinal vertical axis (C2-C7 SVA), spinocranial angle (SCA), C7 slope, C2-C7 lordosis, and the segmental Cobb angle. Measurements were collected the day before, the day after, and 12 months after surgery. Changes in clinical parameters was assessed using the VAS and NDI scales. Subsidence was defined as a loss of intervertebral height of more than 30% of the baseline value. Among all the assessed parameters, only the C2-C7 SVA demonstrated a statistically significant difference between the groups with and without subsidence: 26.03 vs. 21.79 [mm], with p = 0.0182, preoperatively and 27.80 vs. 24.94 [mm], with p = 0.0449, on the day after surgery, respectively. We conclude that higher preoperative and postoperative C2-C7 SVA values might contribute to an elevated risk of implant subsidence. Furthermore, both the SCA and C7 slope could conceivably influence the clinical outcome, respectively impacting pain, as assessed by the VAS and the disability, as evaluated through the NDI scale.

Crossing the Bridge From Degeneration to Deformity: When Does Sagittal Correction Impact Outcomes in Adult Spinal Deformity Surgery?

BACKGROUND

Patients with less severe adult spinal deformity (ASD) undergo surgical correction and often achieve good clinical outcomes. However, it is not well understood how much clinical improvement is due to sagittal correction rather than treatment of the spondylotic process.

PURPOSE

Determine baseline thresholds in radiographic parameters that, when exceeded, may result in substantive clinical improvement from surgical correction.

STUDY DESIGN

Retrospective.

MATERIALS AND METHODS

ASD patients with BL and two-year data were included. Parameters assessed: sagittal vertical axis, pelvic incidence-lumbar lordosis mismatch, pelvic tilt, T1 pelvic angle, L1 pelvic angle, L4-S1 lordosis, C2-C7 sagittal vertical axis, C2-T3, C2 slope. Outcomes: Good Outcome (GO) at two years: [meeting either: (1) Substantial Clinical Benefit for Oswestry Disability Index (change >18.8), or (2) Oswestry Disability Index <15 and Scoliosis Research Society Total>4.5]. Binary logistic regression assessed each parameter to determine if correction was more likely needed to achieve GO. Conditional inference tree run machine learning analysis generated baseline thresholds for each parameter, above which, correction was necessary to achieve GO.

RESULTS

We included 431 ASD patients. There were 223 (50%) that achieved a GO by two years. Binary logistic regression analysis demonstrated, with increasing baseline severity in deformity, sagittal correction was more often seen in those achieving GO for each parameter(all P <0.001). Of patients with baseline T1 pelvic angle above the threshold, 95% required correction to meet GO (95% vs. 54%, P <0.001). A baseline pelvic incidence-lumbar lordosis >10° (74% of patients meeting GO) needed correction to achieve GO (odds ratio: 2.6, 95% confidence interval: 1.4-4.8). A baseline C2 slope >15° also necessitated correction to obtain clinical success (odds ratio: 7.7, 95% confidence interval: 3.7-15.7).

CONCLUSIONS

Our study highlighted point may be present at which sagittal correction has an outsized influence on clinical improvement, reflecting the line where deformity becomes a significant contributor to disability. These new thresholds give us insight into which patients may be more suitable for sagittal correction, as opposed to intervention for the spondylotic process only, leading to a more efficient utility of surgical intervention for ASD.

Effects of combined adjustable Halo-pelvic fixation brace on cervical spine alignment in patients with severe rigid spinal deformity

Objective

To evaluate the effect of continuous traction with a combined adjustable Halo-pelvic fixation brace on the cervical spine alignment in patients with severe rigid spinal deformity and analyze its related factors.

Methods

We conducted a retrospective cohort study of 21 patients with severe rigid spinal deformity treated in our department between 2015 and 2019. All subjects received combined adjustable Halo-pelvic fixation brace traction before secondary orthopedic surgery. The influence of the Halo-pelvic fixation brace on the cervical spine alignment was evaluated by measuring the parameters of lateral cervical X-ray at three time points: before traction, at the end of traction, and 6 months after orthopedic surgery. The correlation between parameter changes and total traction duration was analyzed to explore factors influencing cervical alignment.

Results

The C2L-C7L angle was 22.40 ± 15.91° before traction, which decreased to 5.91 ± 6.78° at the end of traction but increased to 14.51 ± 10.07° after orthopedic surgery (BT vs ET p < 0.005, ET vs AOS p < 0.005, BT vs AOS p < 0.005). Accordingly, C2L-C7U angle, C2L-C6L angle, C2L-C6U angle, C2L-C5L angle, C7 or T1 slope, C2-C7 SVA, SCA, C2-T1 Ha, C0 slope, and C0-C2 angle also changed similarly to C2L-C7L angle. Furthermore, moderate correlation was observed between C2L-C7L angle and total traction volume (r = 0.563, p = 0.008) and SCA and traction duration (r = 0.525, p = 0.015). However, no significant correlation was found between other cervical alignment parameters and total traction volume and traction duration.

Conclusions

The continuous traction of a combined adjustable Halo-pelvic fixation brace can affect the cervical spine alignment of patients with severe rigid spinal deformity and straighten the physiological curvature of the cervical spine. However, the sagittal alignment gradually recovers after the traction, without any adverse effects on the orthopedic surgery and global balance after the operation; therefore, this apparatus is worthy of wide application.

Improvement in some Ames-ISSG cervical deformity classification modifier grades may correlate with clinical improvement

This retrospective cohort study describes adult cervical deformity(ACD) patients with Ames-ACD classification at baseline(BL) and 1-year post-operatively and assesses the relationship of improvement in Ames modifiers with clinical outcomes. Patients ≥ 18yrs with BL and post-op(1-year) radiographs were included. Patients were categorized with Ames classification by primary deformity descriptors (C = cervical; CT = cervicothoracic junction; T = thoracic; S = coronal) and alignment/myelopathy modifiers(C2-C7 Sagittal Vertical Axis[cSVA], T1 Slope-Cervical Lordosis[TS-CL], Horizontal Gaze[Horiz], mJOA). Univariate analysis evaluated demographics, clinical intervention, and Ames deformity descriptor. Patients were evaluated for radiographic improvement by Ames classification and reaching Minimal Clinically Important Differences(MCID) for mJOA, Neck Disability Index(NDI), and EuroQuol-5D(EQ5D). A total of 73 patients were categorized: C = 41(56.2%), CT = 18(24.7%), T = 9(12.3%), S = 5(6.8%). By Ames modifier 1-year improvement, 13(17.8%) improved in mJOA, 26(35.6%) in cSVA grade, 19(26.0%) in Horiz, and 15(20.5%) in TS-CL. The overall proportion of patients without severe Ames modifier grades at 1-year was as follows: 100% cSVA, 27.4% TS-CL, 67.1% Horiz, 69.9% mJOA. 1-year post-operatively, severe myelopathy(mJOA = 3) prevalence differed between Ames-ACD descriptors (C = 26.3%, CT = 15.4%, T = 0.0%, S = 0.0%, p = 0.033). Improvement in mJOA modifier correlated with reaching 1-year NDI MCID in the overall cohort (r = 0.354,p = 0.002). For C descriptors, cSVA improvement correlated with reaching 1-year NDI MCID (r = 0.387,p = 0.016). Improvement in more than one radiographic Ames modifier correlated with reaching 1-year mJOA MCID (r = 0.344,p = 0.003) and with reaching more than one MCID for mJOA, NDI, and EQ-5D (r = 0.272,p = 0.020). In conclusion, improvements in radiographic Ames modifier grades correlated with improvement in 1-year postoperative clinical outcomes. Although limited in scope, this analysis suggests the Ames-ACD classification may describe cervical deformity patients' alignment and outcomes at 1-year.

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.

Cervical Deformity: Evaluation, Classification, and Surgical Planning

Cervical deformity is a challenging condition to treat and requires complex decision-making. Apart from a thorough history and physical examination, a thoughtful and quantitative analysis of multiple imaging modalities is critical for understanding the nature and driver of the cervical deformity. A few classification schemes have emerged, and it is now clear that dynamic films are invaluable as they capture the extension reserve that patients can use to compensate for malalignment. These classification systems can help guide surgical planning, because the various subgroups have different properties that lend themselves to specific treatment paradigms. Here we review the clinical and radiographic evaluation, classification, and surgical planning for cervical deformity.

Establishing the minimum clinically important difference in Neck Disability Index and modified Japanese Orthopaedic Association scores for adult cervical deformity

OBJECTIVE

It is being increasingly recognized that adult cervical deformity (ACD) is correlated with significant pain, myelopathy, and disability, and that patients who undergo deformity correction gain significant benefit. However, there are no defined thresholds of minimum clinically important difference (MCID) in Neck Disability Index (NDI) and modified Japanese Orthopaedic Association (mJOA) scores.

METHODS

Patients of interest were consecutive patients with ACD who underwent cervical deformity correction. ACD was defined as C2-7 sagittal Cobb angle ≥ 10° (kyphosis), C2-7 coronal Cobb angle ≥ 10° (cervical scoliosis), C2-7 sagittal vertical axis ≥ 4 cm, and/or chin-brow vertical angle ≥ 25°. Data were obtained from a consecutive cohort of patients from a multiinstitutional prospective database maintained across 13 sites. Distribution-based MCID, anchor-based MCID, and minimally detectable measurement difference (MDMD) were calculated.

RESULTS

A total of 73 patients met inclusion criteria and had sufficient 1-year follow-up. In the cohort, 42 patients (57.5%) were female. The mean age at the time of surgery was 62.23 years, and average body mass index was 29.28. The mean preoperative NDI was 46.49 and mJOA was 13.17. There was significant improvement in NDI at 1 year (46.49 vs 37.04; p = 0.0001). There was no significant difference in preoperative and 1-year mJOA (13.17 vs 13.7; p = 0.12). Using multiple techniques to yield MCID thresholds specific to the ACD population, the authors obtained values of 5.42 to 7.48 for the NDI, and 1.00 to 1.39 for the mJOA. The MDMD was 6.4 for the NDI, and 1.8 for the mJOA. Therefore, based on their results, the authors recommend using an MCID threshold of 1.8 for the mJOA, and 7.0 for the NDI in patients with ACD.

CONCLUSIONS

The ACD-specific MCID thresholds for NDI and mJOA are similar to the reported MCID following surgery for degenerative cervical disease. Additional studies are needed to verify these findings. Nonetheless, the findings here will be useful for future studies evaluating the success of surgery for patients with ACD undergoing deformity correction.

Changes in Cervical Spinal Alignment After Thoracolumbar Corrective Surgery in Adult Patients With Adolescent Idiopathic Scoliosis

STUDY DESIGN

Case-control study.

OBJECTIVE

To examine factors influencing cervical alignment after corrective surgery for adult patients with adolescent idiopathic scoliosis (AdIS) SUMMARY OF BACKGROUND DATA.: Corrective surgery for spinal deformity influences postoperative cervical spinal alignment, but changes in the cervical alignment in adults with AdIS are scarcely reported.

METHODS

We retrospectively examined 85 patients with AdIS who underwent posterior corrective surgery for thoracic or lumbar major curve and were followed up for 2 years. Clinical characteristics, radiographic parameters, and health-related quality of life (HRQOL) were evaluated. Cervical deformity (CD) was defined as one of the following cases: (1) T1 tilt minus C2-C7 angle more than 20°, (2) C2-C7 SVA more than 40 mm, (3) and C2-C7 angle less than -10°. Patients were divided into those with and without CD based on the defined criteria; statistically relevant factors were analyzed.

RESULTS

There were 19 patients in the postoperative CD group. The average age at the time of surgery was lower in the CD group (26.5 vs. 31.4). In the CD group, the average preoperative T1 tilt was smaller (1.1° vs. 12.5°), and the C2-C7 angle was kyphotic (-16.1° vs. 3.0°). The average kyphotic angle at thoracic spine (T5-T12) was lower in the CD group preoperatively (12.5° vs. 19.5°) and postoperatively (15.2° vs. 20.8°). HRQOL outcomes were comparable between the groups. Of the patients with preoperative CD, 51.5% (n = 17) maintained their deformity at the final follow-up, and baseline C2-C7 angle was lower than those who converted to non-CD following surgery (n = 16) (-17.0° vs. -10.3°).

CONCLUSION

More than half of the patients with baseline CD maintained their cervical malalignment postoperatively. Patients with postoperative CD presented cervical kyphotic and thoracic hypokyphotic alignments before surgery. Because CD has the potential to lead to cervical degeneration, careful follow-up observation is necessary for these young patients.

LEVEL OF EVIDENCE

3.

Sagittal alignment of the cervical spine: do we know enough for successful surgery?

Over the past decade, there has been growing interest in the sagittal alignment of the cervical spine and its correlation to clinical outcomes. It is now known that cervical lordosis is not universally physiological and should not be pursued in all patients undergoing surgery. Rather, it is increasingly understood that it is how these angular parameters (lordosis or kyphosis) interact with translational parameters that is reflective of overall cervical spine and whole spine balance, which in turn impacts patient outcomes. This review synthesises currently available evidence relating to the sagittal alignment of the cervical spine. Radiographic assessment of the cervical spine including horizontal gaze is discussed and alignment in physiological and pathological states analysed. The interdependence of spinal segments is reviewed, with cervical alignment correction influencing the adjacent thoracic spine, and similarly lumbar lordosis (LL) and global balance correction changing cervical spine alignment. Cervical kyphosis with associated cervical sagittal imbalance is known to lead to poorer post-operative outcomes, and this dichotomy in outcomes has not been shown to improve even with alignment correction. Further work is required to uncover the extent to which cervical spine alignment correction should be attempted toward improved patient outcomes, in order to plan and deliver patient-specific surgical realignment targets.

Cervical kyphosis in asymptomatic populations: incidence, risk factors, and its relationship with health-related quality of life

Background

Cervical kyphosis has been pointed out in asymptomatic populations. The purposes of this study were (1) to investigate the incidence of cervical kyphosis in asymptomatic populations, (2) to identify risk factors related to cervical kyphosis, and (3) to assess the relationship between cervical kyphosis and health-related quality of life (HRQOL).

Methods

A cohort of 235 asymptomatic volunteers’ records was retrospectively analyzed. Radiographic parameters of the coronal and sagittal planes were measured in the full-length spine x-ray. All patients were classified into two groups based on the cervical lordosis angle: cervical lordosis (CL) and cervical kyphosis (CK). HRQOL was evaluated by EQ-5D and SF-36 (PCS and MCS) questionnaires.

Results

CK was observed in 90 of 235 (38.3%) participants. There was a significant difference with regard to age between volunteers with CK and CL (32.23 ± 8.12 vs. 42.12 ± 6.14, p < 0.05). Several parameters had a significant relationship with CK, including TK, T1 slope, TIA, SVA, and CT. Logistic regression analysis identified age, TK, T1 slope, and SVA as independent risk factors of CK. In addition, there was a negative correlation between CK and the parameters of HRQOL (EQ-5D, − 0.63; PCS, − 0.68; MCS, − 0.59).

Conclusions

The incidence of CK in normal populations is 38.3%. Some spinal parameters are related to CK. CK is associated with the HRQOL.

McGregor's slope and slope of line of sight: two surrogate markers for Chin-Brow vertical angle in the setting of cervical spine pathology

BACKGROUND CONTEXT

Chin-Brow Vertical Angle (CBVA) is not routinely measured on radiographs even though it is a strong assessor of horizontal gaze.

STUDY DESIGN

Retrospective cohort study of patients with full-body stereoradiographs and a primary cervical diagnosis at the time of presentation.

PURPOSE

Assess the utility of McGregor's Slope (McGS) and Slope of Line of Sight (SLS) as surrogate markers for the CBVA in cervical spine pathology.

METHODS

A retrospective review of patients with full-body stereoradiographs was performed. Patients were ≥18 years of age with a primary cervical diagnosis. Analysis of CBVA, McGS, and SLS was conducted as markers of horizontal gaze. Sagittal alignment was characterized by: pelvic tilt (PT), pelvic incidence minus lumbar lordosis (PI-LL), T1-pelvic angle (TPA), sagittal vertical axis (SVA), T2-T12 thoracic kyphosis, C2-C7 SVA (cSVA), C2-C7 Cervical lordosis, T1-Slope minus Cervical Lordosis (TS-CL), and C2-Slope (C2S). A subgroup analysis was performed in patients with cervical deformity. Independent sample t tests and paired t tests compared radiographic alignment. Pearson correlations characterized linear relationships. Linear regression analysis identified relationships between the parameters.

RESULTS

In all, 329 patients were identified with primary cervical spine diagnoses. Chin-Brow Vertical Angle was visible in 171 patients (52.0%), McGS in 281 (85.4%), and SLS in 259 (78.7%). Of the 171 patients with visible CBVA, the mean CBVA was 2.30±7.7, mean McGS was 5.02±8.1, and mean SLS was -1.588±2.03. Chin-Brow Vertical Angle strongly correlated with McGS (r=0.83) and SLS (r=0.89) with p<.001. McGregor's Slope positively correlated with SLS (r=0.89, p=.001).

CONCLUSIONS

This study demonstrates that McGS and SLS serve as strong, positive correlates for CBVA. The reported mean differences between these measurements provide a useful conversion, broadening CBVA's use as a radiographic assessment of horizontal gaze.

Cervical Spine Deformity: Indications, Considerations, and Surgical Outcomes

Cervical spinal deformity (CSD) in adult patients is a relatively uncommon yet debilitating condition with diverse etiologies and clinical manifestations. Similar to thoracolumbar deformity, CSD can be broadly divided into scoliosis and kyphosis. Severe forms of CSD can lead to pain; neurologic deterioration, including myelopathy; and cervical spine-specific symptoms such as difficulty with horizontal gaze, dysphagia, and dyspnea. Recently, an increased interest is shown in systematically studying CSD with introduction of classification schemes and treatment algorithms. Both major and minor complications after surgical intervention have been analyzed and juxtaposed to patient-reported outcomes. An ongoing effort exists to better understand the relationship between cervical and thoracolumbar spinal alignment, most importantly in the sagittal plane.

Comparison of Postoperative Outcomes According to Compensatory Changes of the Thoracic Spine Among Patients With a T1 Slope More Than 40°

STUDY DESIGN

Retrospective study of postoperative outcomes of adult spinal deformity (ASD) surgery.

OBJECTIVE

To clarify the differences in postoperative outcomes depending on the presence or absence of thoracic compensatory changes among patients with a T1 slope (TS) more than 40°.

SUMMARY OF BACKGROUND DATA

Loss correction after ASD surgery is more likely to occur when preoperative TS is more than 40°. When preoperative TS is more than 40°, some cases involve compensatory changes in the thoracic spine and decreased thoracic kyphosis (TK); others involve increased TK without compensatory changes.

METHODS

Seventy-nine patients with TS more than 40° who underwent ASD surgery were enrolled and separated into compensated and noncompensated groups (group C: TK <40°; group NC: TK ≥40°). Radiographic parameters obtained by whole-spine standing x-ray, the Oswestry Disability Index (ODI), and Scoliosis Research Society-22 (SRS-22) questionnaire were assessed.

RESULTS

There were 41 patients in group C and 38 patients in group NC. Preoperative significant differences in TS did not disappear after surgery (preoperative TS: group C and group NC = 46° and 55°, P < 0.001; just after surgery: group C and group NC = 27° and 40°, P < 0.001; 2 years later: group C and group NC = 34° and 47°, P < 0.001). There were no significant differences in ODI and all domains of the SRS-22 before surgery. However, 2 years after the surgery, ODI (38%), pain (3.5), self-image (3.0), and total (3.2) values of the SRS-22 for group NC were significantly worse than those (28%, 4.0, 3.4, and 3.5, respectively) for group C (P < 0.05).

CONCLUSION

Changes in the thoracic spine (TS and TK >40°) result in poor postoperative outcomes. Extending the upper instrumented vertebra (UIV) to the upper thoracic spine must be considered. Even when TS is more than 40°, TK less than 40°, and upper instrumented vertebra set to the lower thoracic level result in good postoperative outcomes.

LEVEL OF EVIDENCE

3.

Cervical spine alignment following surgery for adolescent idiopathic scoliosis (AIS): a pre-to-post analysis of 81 patients

Background

Several studies have emphasized the importance of restoring thoracic kyphosis (TK) in the setting of AIS, but very few have discussed changes in cervical spine alignment following surgery. Aim of this study was to evaluate reciprocal cervical alignment change after modification of global and regional thoracolumbar alignment with surgery in the setting of adolescent idiopathic scoliosis (AIS).

Methods

Baseline and 2-yrs follow-up radiographs of AIS patients (n = 81) were analysed measuring cervical parameters (upper cervical: C2-C0, McGregor Slope; lower cervical: C2-C7, C2-C7 sagittal vertical axis (SVA), C2-T3, C2-T3SVA, C2-T1Harrison (C2-T1Ha), T1 Slope (T1S)), thoracic, lumbar, pelvic and global alignment parameters. Post-operatively, patients were grouped twice; based on changes in TK and SVA. Cervical alignment was compared between groups. Pearson correlation was conducted to examine the relationship between changes in TK, SVA, and cervical alignment.

Results

Stratification by change in TK, revealed significant alteration of lower cervical alignment T1S [p < 0.001]), C2-T3 [p = 0.019], C2-T1Ha [p = 0.043]), but there was no reciprocal change in the upper cervical spine. Stratification by SVA revealed a significant coexisting change in the lower cervical spine (T1S [p < 0.001], C2-C7SVA [p = 0.034], C2-T3 [p = 0.023], C2-T3SVA [p = 0.001]). SVA change was not associated to a change in the upper cervical spine. The correlation analysis showed that with a post-operative increase in TK, the cervical spine became more lordotic. Changes in TK were significantly correlated with: ΔT1S, ΔC2-C7, ΔC2-T3, and ΔC2-T3SVA. Similarly, increased cervical kyphosis was found when SVA was decreased post-operatively. Furthermore, there was a significant correlation between change of SVA and both ΔC2-T3 and ΔC2-T3SVA.

Conclusions

In surgically treated AIS patients, changes in global and regional alignment of the thoracolumbar and cervical spinal segments exhibit interdependence. Thus, surgical planning with regard to sagittal deformity in AIS patients should account for the post-operative impact on cervical alignment.

Cervical mismatch: the normative value of T1 slope minus cervical lordosis and its ability to predict ideal cervical lordosis

OBJECTIVE: Numerous studies have attempted to delineate the normative value for T1S-CL (T1 slope minus cervical lordosis) as a marker for both cervical deformity and a goal for correction similar to how PI-LL (pelvic incidence-lumbar lordosis) mismatch informs decision making in thoracolumbar adult spinal deformity (ASD). The goal of this study was to define the relationship between T1 slope (T1S) and cervical lordosis (CL). METHODS: This is a retrospective review of a prospective database. Surgical ASD cases were initially analyzed. Analysis across the sagittal parameters was performed. Linear regression analysis based on T1S was used to provide a clinically applicable equation to predict CL. Findings were validated using the postoperative alignment of the ASD patients. Further validation was then performed using a second, normative database. The range of normal alignment associated with horizontal gaze was derived from a multilinear regression on data from asymptomatic patients. RESULTS: A total of 103 patients (mean age 54.7 years) were included. Analysis revealed a strong correlation between T1S and C0-7 lordosis (r = 0.886), C2-7 lordosis (r = 0.815), and C0-2 lordosis (r = 0.732). There was no significant correlation between T1S and T1S-CL. Linear regression analysis revealed that T1S-CL assumed a constant value of 16.5° (R2 = 0.664, standard error 2°). These findings were validated on the postoperative imaging (mean absolute error [MAE] 5.9°). The equation was then applied to the normative database (MAE 6.7° controlling for McGregor slope [MGS] between -5° and 15°). A multilinear regression between C2-7, T1S, and MGS demonstrated a range of T1S-CL between 14.5° and 26.5° was necessary to maintain horizontal gaze. CONCLUSIONS: Normative CL can be predicted via the formula CL = T1S - 16.5° ± 2°. This implies a threshold of deformity and aids in providing a goal for surgical correction. Just as pelvic incidence (PI) can be used to determine the ideal LL, T1S can be used to predict ideal CL. This formula also implies that a kyphotic cervical alignment is to be expected for individuals with a T1S < 16.5°.

Validity and Reproducibility of Various Measurement Methods for Craniocervical Sagittal Balance

STUDY DESIGN

A cross-sectional study.

OBJECTIVE

To identify the best indicator for reproducible representation of craniocervical sagittal balance (CCSB).

SUMMARY OF BACKGROUND DATA

Spinal sagittal balance is considered one of the most critical factors affecting the health-related quality of life. Although standard indicators of spinopelvic balance have been established, these do not include the craniocervical balance and there is no standard parameter for evaluating the CCSB.

MATERIALS AND METHODS

Six kinds of sagittal vertical axis (SVA) were drawn by a total of 9 spine or orthopedic surgeons, from the anterior margin of the external auditory canal: cranial center of gravity (CCG), C1 (center of the anterior arch), C2 (C2vb: center of the vertebral body, C2e: center of the lower endplate), and C7 (C7vb: center of the vertebral body, C7p: posterosuperior corner). Eight SVA distances were measured by using 30 radiographs; CCG-C7vb, C1-C7vb, C2e-C7vb, C2vb-C7vb, CCG-C7p, C1-C7p, C2e-C7p, and C2bv-C7p.The interobserver and intraobserver reliabilities, and the correlations between CCG and C1, C2e, or C2bv were calculated among the main groups or subgroups.

RESULTS

In the overall analysis, although the intraclass correlation coefficients (ICC) (1, 1) of all parameters were >0.900, the ICC (2, 1) of CCG-C7p and CCG-C7vb were <0.900. The same trends were noted in the subgroups based on observer's experience. Comparing C7p-related and C7vb-related parameters, ICC (2, 1) showed 0.901 in C7p-related and 0.849 in C7bv-related parameters. In the analysis of the correlation between cranial SVAs, C1-C7p and C2vb-C7p SVAs correlated highly with CCG-C7p SVA (0.905, 0.805, respectively).

CONCLUSIONS

Although the CCG SVA represents the center of the head, the current results revealed its low reproducibility. The low values were notable in those unfamiliar with craniocervical anatomy. The correlation analysis indicated that C1-C7p and C2vb-C7p SVA parameters are suitable for CCG-C7p SVA. Therefore, these 2 are considered as possible standard parameters in evaluating CCSB.

LEVEL OF EVIDENCE

Level III.

Expansive open-door laminoplasty versus laminectomy and instrumented fusion for cases with cervical ossification of the posterior longitudinal ligament and straight lordosis

PURPOSE

To identify whether expansive open-door laminoplasty (Lam) is more appropriate than laminectomy and instrumented fusion (LIF) for cases with ossification of the posterior longitudinal ligament (OPLL) and straight cervical lordosis.

METHODS

A total of 67 cases were included and divided into Group Lam (n = 32) and Group LIF (n = 35), and the mean follow-up periods were 38 and 42 months, respectively. The cervical lordosis was elevated by C2-7 Cobb angle and cervical sagittal balance by C2-C7 sagittal vertical axis (SVA). Japanese Orthopedic Association (JOA), neurological recovery rate (RR) being calculated by the JOA, visual analog scale (VAS) and neck disability index (NDI) were used to assess clinical outcomes.

RESULTS

Differences in general data between two groups were not significant. Total blood loss and operation duration in Group Lam were both significantly less than that in the Group LIF. By the final follow-up, the cervical lordosis significantly decreased in Group Lam and increased in Group LIF, the SVA significantly increased in Group Lam and kept unchanged in Group LIF, and the JOA, VAS, NDI significantly improved in both groups. Although there was no significant difference in RR between the two groups, cases in Group Lam had significantly larger incidence of postoperative kyphosis and kyphotic change rate, and less VAS, NDI and incidence of axial pain than cases in Group LIF.

CONCLUSIONS

When compared with the LIF, the Lam is recommended for cases with OPLL and straight cervical lordosis when taking comparable neurological recovery, less axial pain and better neck function improvement into consideration.