Sagittal alignment of cervical spine in adult idiopathic scoliosis

Analysis of risk factors of axial neck pain in posterior cervical single-door laminoplasty from the perspective of cervical sagittal plane

Objective

We carried out this study to explore the possible relationship between the cervical sagittal parameters in radiological images and axial neck pain (ANP) for patients who had underwent posterior cervical single-door laminoplasty.

Method

141 patients were enrolled in the study from January 2018 to January 2021, among which 38 were enrolled into the ANP group and 103 were enrolled into the non-ANP group. C2–7 Cobb angle, C2–7 sagittal vertex axis (SVA), thoracic inlet angle, neck tilt, and T1 slope were measured using computed tomography. Spearman correlation tests were used to analyze the possible correlation between radiological parameters and ANP. Logistic regression was carried out to analyze the potential risk factor for the occurrence of ANP. Receiver operating characteristic (ROC) curve and area under the ROC curve were used to evaluate the significant result and the optimal diagnostic value.

Results

As for radiographic parameters in the sagittal plane, the results suggested that only T1 slope and C2–7 SVA were statistically different between the ANP and non-ANP group (p = 0.001 and p = 0.047). Patients whose surgery involved the C2 spinous process demonstrated severe ANP symptoms than patients in the non-ANP group (p = 0.003). The Spearman correlation test showed that no statistical differences were found between visual analog scale (VAS) and radiological morphology parameters and only C2 involvement was found to correlate with postoperative VAS with respect to surgery. Logistic multivariate regression analysis demonstrated that only C2 involvement and T1 slope were significantly different when C2–7 SVA, T1 slope, C2 involvement together were included into consideration, with p values of 0.01 and 0.001.

Conclusion

According to our research, C2 involvement and greater T1 slope were independent risk factors of ANP for the patients who underwent laminoplasty of cervical spine.

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.

What are the major drivers of outcomes in cervical deformity surgery?

Background Context:

Cervical deformity (CD) correction is becoming more challenging and complex. Understanding the factors that drive optimal outcomes has been understudied in CD corrective surgery.

Purpose:

The purpose of the study was to weight baseline (BL) factors on impact upon outcomes following CD surgery.

Study Design Setting:

This was a retrospective review of a single-center database.

Patient Sample:

The sample size of the study was 61 cervical patients.

Outcome Measures:

Two outcomes were measured: “Improved outcome (IO)”: (1) radiographic improvement: “nondeformed” Schwab pelvic tilt (PT)/sagittal vertical axis (SVA) and Ames cervical sagittal vertical axis (cSVA)/T1 Slope – cervical lordosis (TSCL); (2) clinical: MCID Euro-QOL 5 Dimension (EQ5D), Neck Disability Index (NDI), or improvement in modified Japanese Orthopedic Association (mJOA) scale modifier; and (3) complications/reoperation: no reoperation or major complications and “poor outcome” (PO): (1) radiographic deterioration: “moderate” or “severely” deformed Schwab SVA/PT and Ames cSVA/TS-CL; (2) clinical: not meeting MCID EQ5D and NDI worsening in mJOA modifier; and (3) complications/reoperation: reoperation or complications.

Materials and Methods:

CD patients included full BL and 1-year (1Y) radiographic measures and Health related quality of life (HRQLs) questionnaires. Patients who underwent a reoperation for infection were excluded. Patients were categorized by IO, PO, or not. Random forest assessed ratios of predictors for IO and PO. Categorical regression models predicted how BL regional deformity (Ames cSVA, TS-CL, and horizontal gaze), BL global deformity (Schwab PI-LL, SVA, and PT), regional/global change (BL to 1Y), BL disability (mJOA score), and BL pain/function impact outcomes.

Results:

Sixty-one patients were included in the study (55.8 years, 54.1% of females). Surgical approach included 18.3% anterior, 51.7% posterior, and 30% combined. The average number of levels fused for the cohort was 7.7. Mean operative time was 823 min, and estimated blood loss (EBL): 1037ccs. At 1Y, 24.6% had an IO and 9.8% had PO. Random forest analysis showed the top five individual factors associated with an IO: BL maximum kyphosis, maximum lordosis, C0–C2, L4 pelvic angle, and NSR back pain (80% radiographic, 20% clinical). Categorical IO regression model (R² = 0.328, P = 0.007) showed low BL regional deformity (β = ‒0.082), low BL global deformity (β = ‒0.099), global improvement (β = ‒0.532), regional improvement (β = ‒0.230), low BL disability (β = ‒0.100), and low BL NDI (β = ‒0.024). Random forest demonstrated the top five individual BL factors associated with PO, 80% were radiographic: BL CL apex, DJK angle, cervical lordosis, T1 slope, and NSR neck pain. Categorical PO regression model (R² = 0.306, P = 0.012) showed high BL regional deformity (β = ‒0.108), high BL global deformity (β = ‒0.255), global decline (β = ‒0.272), regional decline (β = 0.443), BL disability (β = −‒0.164), BL and severe NDI (>69) (β = ‒0.181).

Conclusions:

Categorical weight demonstrated radiographic as the strongest predictor of both improved (global alignment) and PO (regional deformity/deterioration). Radiographic factors carry the most weight in determining an improved or PO, and can be ultimately utilized in preoperative planning and surgical decision-making to optimize outcomes.

Global alignment taking into account the cervical spine with odontoid hip axis angle (OD-HA)

INTRODUCTION

Global alignment analysis is of upmost importance in adult spinal deformity patients (ASD). Numerous parameters exist in the literature to measure global alignment based upon C7 or T1. One common limitation of these parameters is that they neglect the cervical segment which is essential in spinal compensatory mechanisms and in horizontal gaze preservation. A recent stereoradiography analysis of asymptomatic subjects introduced a new 3D parameter (ODHA), defined as the angle between the vertical reference line and the line joining the odontoid tip (OD) to hip axis center (HA). Thus, the goal of this study was to analyze 3D global alignment of ASD patients using the new parameter odontoid hip axis angle and its relationship to other spinal parameters.

METHODS

In this prospective study, 90 adult patients with lumbar scoliosis (Cobb > 20°) were included. All subjects underwent low dose biplanar X-rays with 3D spinal reconstructions. Based on published normative values of ODHA, we defined abnormally high value as mean ODHA of asymptomatic subject + 2SD (i.e., ODHA > 6.1°). Values of 3D radiographic parameters and ODI were compared between patients with ODHA > 6.1° and < 6.1°.

RESULTS

Mean ODHA was 5+/- 3.6° (0.4° to 18.6°). 22 patients had abnormally high ODHA. They were older than the 68 other patients (68+/- 9y vs 53+/- 14y, p = 0.001), without any significant difference in terms of sex, BMI and rate of rotatory subluxation (54% vs 62%, p = 0.06). However, coronal and sagittal deformity was more important in patients with abnormal ODHA (larger Cobb angle, coronal malalignment, pelvic tilt and lower lumbar lordosis). Patients with abnormal ODHA had significantly worst ODI (50+/- 23 vs 30+/- 18, p = 0.0005).

CONCLUSION

Extreme values of ODHA are observed in significantly older patients with significant functional impairment. In addition, in these patients with sagittal malalignment with loss of lumbar lordosis, who recruit compensatory mechanisms such as pelvic retroversion, the cervical area is also involved with a posture in cervical hyperlordosis to maintain the head over the pelvis. Thus, ODHA is an interesting parameter allowing a more comprehensive alignment measurement taking into account the mechanisms of compensation of the cervical spine to the pelvis.

Impact of cervical sagittal parameters on axial neck pain in patients with cervical kyphosis

Background

Cervical sagittal alignment (CSA) is closely related with cervical disk degeneration and impacts the spinal function, especially in the setting of cervical kyphosis (CK). In this study, we evaluated the influence of cervical sagittal parameters on the development of axial neck pain (ANP) in patients with CK.

Methods

Data pertaining to 263 patients with CK who visited the outpatient department of our hospital between January 2012 and December 2018 were retrospective analyzed. The most common symptoms of ANP were neck pain, stiffness, or dullness. Visual analog scale (VAS) was used to evaluate ANP. The following radiographic parameters were evaluated: CK types, C2-7 sagittal vertical axis (SVA), thoracic inlet angle (TIA), T1 slope, neck tilt (NT), cranial tilt, and cervical tilt. Sagittal alignment of CK was classified into 2 types: global and regional type. Multivariate logistic regression analysis was performed to identify risk factors for ANP.

Results

Patients who complained of ANP were categorized as ANP group (VAS score ≥ 3; n = 92), while those without ANP were categorized as non-ANP group (VAS score < 3; n = 171). There was no significant between-group difference with respect to age (P = 0.196), gender (P = 0.516), TIA (P = 0.139), NT (P = 0.676), CK type (P = 0.533), cranial tilt (P = 0.332), cervical tilt (P = 0.585), or cervical disk degeneration (P = 0.695). The T1 slope and C2-7 SVA in the ANP group were significantly greater than that in the non-ANP group (P < 0.05). On multivariate logistic regression, C2-7 SVA [

odds ratio (OR) 2.318, 95% confidence interval 1.373–4.651, P = 0.003) and T1 slope (OR 2.563, 95% CI 1.186–4.669, P = 0.028) were identified as risk factors for ANP.

Conclusions

Our findings suggest a significant effect of cervical sagittal parameters on the occurrence of ANP in patients with CK. Greater T1 slope and larger C2-7 SVA may lead to the development of neck pain.

High thoracic kyphosis: impact on total thoracic kyphosis and cervical alignment in patients with adolescent idiopathic scoliosis

PURPOSE

To evaluate the impact of proximal thoracic segment (T1-T5) on global thoracic kyphosis, as well as its influence on cervical alignment (lordotic, kyphotic or straight) in patients with adolescent idiopathic scoliosis (AIS).

METHODS

We conducted a retrospective study of 80 patients with AIS. The inclusion criteria were patients between 10 and 18 years of age with a posteroanterior (PA) and lateral full-length radiographs, excluding those subjected to surgery, orthotic treatment, with other spinal disease or with poor X-ray quality. The parameters evaluated were age, sex, pelvic incidence (PI), sacral slop (SS), pelvic tilt (PT), global sagittal balance (GSB), scoliotic curvatures (differentiated according to primary curve, lumbar modifier and sagittal modifier), cervical spine alignment, thoracic sagittal Cobb angle between T1 and T5, T5 and T12 and between T1 and T12.

RESULTS

In patients with AIS, the proximal sagittal thoracic Cobb segment, contrary to the distal, demonstrated a significant positive correlation with cervical spine alignment (p < 0.05). As there is an increase in proximal thoracic angle, there is an increase in cervical lordosis. We also demonstrated that the correlation between an increase in scoliotic curvature and a decrease in kyphosis only occurred in the distal thoracic segment (T5-T12). Relative to the spinopelvic parameters, the PI was not related with the dorsal kyphosis or shape of the cervical spine.

CONCLUSIONS

In AIS, proximal (T1-T5) and distal (T5-T12) thoracic kyphosis have different contributions on the global thoracic sagittal curvature and in the phenomenon of hypokyphosis. On the other hand, only the proximal segment is significantly related to the shape of the cervical spine.

LEVEL OF EVIDENCE

IV.

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.

The change of cervical sagittal parameters plays an important role in clinical outcomes of cervical spondylotic myelopathy after multi-level anterior cervical discectomy and fusion

BACKGROUND

Cervical sagittal parameters were closely related with clinical outcomes after multi-level ACDF. Our purpose was to evaluate the clinical outcomes and cervical sagittal parameters in patients with MCSM after ACDF and to identify the risk factors of poor clinical outcomes.

MATERIAL AND METHODS

ACDF was performed in 89 patients with MCSM. Based on average JOA recovery rate, patients were divided good-outcome group (group GO) and poor-outcome group (group PO). The cervical sagittal parameters including Cobb angle, SVA, T1S, cranial tilt and cervical tilt were measured. Multivariate logistic regression was used to identify risk factors.

RESULTS

Fifty-four patients (60.67%) were divided into group GO, while 35 patients (39.33%) were divided into group PO. Cobb angle, SVA and T1S was corrected from preoperative average 11.80° ± 9.63°, 23.69 mm ± 11.69 mm and 24.43° ± 11.78° to postoperative average 15.08° ± 9.05°, 18.79 mm ± 10.78 mm and 26.92° ± 11.94° respectively (p < 0.001). △Cobb angle (p = 0.008) and △SVA (p = 0.009) showed significantly statistical differences between two groups. Longer symptom duration, lower preoperative JOA score, smaller △Cobb angle and larger △SVA were identified as risk factors of poor clinical outcomes.

CONCLUSION

Multi-level ACDF is an effective surgical method to treat patients with MCSM. However, long duration of preoperative symptoms, lower preoperative JOA score, smaller △Cobb angle and larger △SVA are risk factors for poor outcomes in patients with MCSM after ACDF. Sagittal parameters should be paid attention to in surgery.

Sagittal alignment of the cervical spine in the setting of adolescent idiopathic scoliosis

OBJECTIVEThe goal of this study was to investigate the impact of thoracic and lumbar alignment on cervical alignment in patients with adolescent idiopathic scoliosis (AIS).METHODSEighty-one patients with AIS who had a Cobb angle > 40° and full-length spine radiographs were included. Radiographs were analyzed using dedicated software to measure pelvic parameters (sacral slope [SS], pelvic incidence [PI], pelvic tilt [PT]); regional parameters (C1 slope, C0-C2 angle, chin-brow vertical angle [CBVA], slope of line of sight [SLS], McRae slope, McGregor slope [MGS], C2-7 [cervical lordosis; CL], C2-7 sagittal vertical axis [SVA], C2-T3, C2-T3 SVA, C2-T1 Harrison measurement [C2-T1 Ha], T1 slope, thoracic kyphosis [TK], lumbar lordosis [LL], and PI-LL mismatch); and global parameters (SVA). Patients were stratified by their lumbar alignment into hyperlordotic (LL > 59.7°) and normolordotic (LL 39.3° to 59.7°) groups and also, based on their thoracic alignment, into hypokyphotic (TK < -33.1°) and normokyphotic (TK -33.1° to -54.9°) groups. Finally, they were grouped based on their global alignment into either an anterior-aligned group or a posterior-aligned group.RESULTSThe lumbar hyperlordotic group, in comparison to the normolordotic group, had a significantly larger LL, SS, PI (all p < 0.001), and TK (p = 0.014) and a significantly smaller PI-LL mismatch (p = 0.001). Lumbar lordosis had no influence on local cervical parameters.The thoracic hypokyphotic group had a significantly larger PI-LL mismatch (p < 0.002) and smaller T1 slope (p < 0.001), and was significantly more posteriorly aligned than the normokyphotic group (-15.02 ± 8.04 vs 13.54 ± 6.17 [mean ± SEM], p = 0.006). The patients with hypokyphotic AIS had a kyphotic cervical spine (cervical kyphosis [CK]) (p < 0.001). Furthermore, a posterior-aligned cervical spine in terms of C2-7 SVA (p < 0.006) and C2-T3 SVA (p < 0.001) was observed in the thoracic hypokyphotic group.Comparing patients in terms of global alignment, the posterior-aligned group had a significantly smaller T1 slope (p < 0.001), without any difference in terms of pelvic, lumbar, and thoracic parameters when compared to the anterior-aligned group. The posterior-aligned group also had a CK (-9.20 ± 1.91 vs 5.21 ± 2.95 [mean ± SEM], p < 0.001) and a more posterior-aligned cervical spine, as measured by C2-7 SVA (p = 0.003) and C2-T3 SVA (p < 0.001).CONCLUSIONSAlignment of the cervical spine is closely related to thoracic curvature and global alignment. In patients with AIS, a hypokyphotic thoracic alignment or posterior global alignment was associated with a global cervical kyphosis. Interestingly, upper cervical and cranial parameters were not statistically different in all investigated groups, meaning that the upper cervical spine was not recruited for compensation in order to maintain a horizontal gaze.

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.

The Relationship Between Improvements in Myelopathy and Sagittal Realignment in Cervical Deformity Surgery Outcomes

STUDY DESIGN

Retrospective review.

OBJECTIVE

Determine whether alignment or myelopathy improvement drives patient outcomes after cervical deformity (CD) corrective surgery.

SUMMARY OF BACKGROUND DATA

CD correction involves radiographic malalignment correction and procedures to improve motor function and pain. It is unknown whether alignment or myelopathy improvement drives patient outcomes.

METHODS

Inclusion: Patients with CD with baseline/1-year radiographic and outcome scores. Cervical alignment improvement was defined by improvement in Ames CD modifiers. modified Japanese Orthopaedic Association (mJOA) improvement was defined as mild [15-17], moderate [12-14], severe [<12]. Patient groups included those who only improved in alignment, those who only improved in mJOA, those who improved in both, and those who did not improve. Changes in quality-of-life scores (neck disability index [NDI], EuroQuol-5 dimensions [EQ-5D], mJOA) were evaluated between groups.

RESULTS

A total of 70 patients (62 yr, 51% F) were included. Overall preoperative mJOA score was 13.04 ± 2.35. At baseline, 21 (30%) patients had mild myelopathy, 33 (47%) moderate, and 16 (23%) severe. Out of 70 patients 30 (44%) improved in mJOA and 13 (18.6%) met 1-year mJOA minimal clinically important difference. Distribution of improvement groups: 16/70 (23%) alignment-only improvement, 13 (19%) myelopathy-only improvement, 18 (26%) alignment and myelopathy improvement, and 23 (33%) no improvement. EQ-5D improved in 11 of 16 (69%) alignment-only patients, 11 of 18 (61%) myelopathy/alignment improvement, 13 of 13 (100%) myelopathy-only, and 10 of 23 (44%) no myelopathy/alignment improvement. There were no differences in decompression, baseline alignment, mJOA, EQ-5D, or NDI between groups. Patients who improved only in myelopathy showed significant differences in baseline-1Y EQ-5D (baseline: 0.74, 1 yr:0.83, P < 0.001). One-year C2-S1 sagittal vertical axis (SVA; mJOA r = -0.424, P = 0.002; EQ-5D r = -0.261, P = 0.050; NDI r = 0.321, P = 0.015) and C7-S1 SVA (mJOA r = -0.494, P < 0.001; EQ-5D r = -0.284, P = 0.031; NDI r = 0.334, P = 0.010) were correlated with improvement in health-related qualities of life.

CONCLUSION

After CD-corrective surgery, improvements in myelopathy symptoms and functional score were associated with superior 1-year patient-reported outcomes. Although there were no relationships between cervical-specific sagittal parameters and patient outcomes, global parameters of C2-S1 SVA and C7-S1 SVA showed significant correlations with overall 1-year mJOA, EQ-5D, and NDI. These results highlight myelopathy improvement as a key driver of patient-reported outcomes, and confirm the importance of sagittal alignment in patients with CD.

LEVEL OF EVIDENCE

3.

Diagnostic Value of T1 Slope in Degenerative Cervical Spondylotic Myelopathy

Background

To explore the diagnostic value of sagittal measurement of thoracic inlet parameters for degenerative cervical spondylotic myelopathy (DCSM).

Material/Methods

Sixty patients with DCSM (study group) and the same number of normal subjects (control group) were initially enrolled in the study. All data from X-ray in the standing position and computed tomography (CT) in the supine position were collected and carefully analyzed. Cervical sagittal parameters, including C2–C7 angle, C2–C7 sagittal vertical axis (C2–C7 SVA), T1 slope, thoracic inlet angle (TIA), and neck tilt (NT), were measured at the lateral radiographs by using standard X-rays and CT. Univariate analysis and multivariate logistic regression analysis were carried out to explore the diagnostic value of cervical sagittal parameters for the DCSM.

Results

All the enrolled patients in the study and control groups completed the follow-up, and the mean follow-up periods were 35.8 months in the study group and 36.3 months in the control group. The DCSM group had smaller T1 slope and TIA when compared with that of the control group (18.14±2.67° vs. 24.16±3.7°, p=0.00; 66.42±12.36° vs. 70.42±10.21°, p=0.01). Logistic regression analysis and receiver operating characteristic (ROC) curve revealed that preoperative T1 slope of less than 18.5° had significant diagnostic value for the incidence of DCSM (p<0.05).

Conclusions

Patients with sagittal imbalance of thoracic inlet parameters have higher risk of DCSM, while T1 slope of less than 18.5° showed significant diagnostic value for the incidence of DCSM.

Cervical Alignment Variations in Different Postures and Predictors of Normal Cervical Kyphosis: A New Understanding

STUDY DESIGN

Comparative study of prospectively collected radiographic data.

OBJECTIVE

To predict physiological alignment of the cervical spine and study its morphology in different postures.

SUMMARY OF BACKGROUND DATA

There is increasing evidence that normal cervical spinal alignment may vary from lordosis to neutral to kyphosis, or form S-shaped or reverse S-shaped curves.

METHODS

Standing, erect sitting, and natural sitting whole-spine radiographs were obtained from 26 consecutive patients without cervical spine pathology. Sagittal vertical axis (SVA), global cervical lordosis, lower cervical alignment C4-T1, C0-C2 angle, T1 slope, C0-C7 SVA and C2-7SVA, SVA, thoracic kyphosis, thoracolumbar junctional angle, lumbar lordosis, sacral slope, pelvic tilt, and pelvic incidence were measured. Statistical analysis was performed to elucidate differences in cervical alignment for all postures. Predictive values of T1 slope and SVA for cervical kyphosis were evaluated.

RESULTS

Most patients (73.0%) do not have lordotic cervical alignment (C2-C7) upon standing (mean -0.6, standard deviation 11.1°). Lordosis increases significantly when transitioning from standing to erect sitting, as well as from erect to natural sitting (mean -17.2, standard deviation 12.1°). Transition from standing to natural sitting also produces concomitant increases in SVA (-8.8-65.2 mm) and T1-slope (17.4°-30.2°). T1 slope and SVA measured during standing significantly predicts angular cervical spine alignment in the same position. SVA < 10 mm significantly predicts C4-C7 kyphosis (P < 0.001), and to a lesser extent, C2-C7 kyphosis (P = 0.02). T1 slope <20° is both predictive of C2-C7 and C4-7 kyphosis (P = 0.001 and P = 0.023, respectively). For global cervical Cobb angle, T1 slope seems to be a more significant predictor of kyphosis than SVA (odds ratio 17.33, P = 0.001 vs odds ratio 11.67, P = 0.02, respectively).

CONCLUSION

The cervical spine has variable normal morphology. Key determinants of its alignment include SVA and T1 slope. Lordotic correction of the cervical spine is not always physiological and thus correction targets should be individualized.

LEVEL OF EVIDENCE

3.

C7 sagittal vertical axis is the determinant of the C5-C7 angle in cervical sagittal alignment

BACKGROUND CONTEXT

Previous studies have indicated that the T1 slope correlates with cervical lordosis. In contrast, the specific impact of the C7 sagittal vertical axis (C7SVA) on cervical lordosis remains unknown.

PURPOSE

This study aimed to investigate the specific role of C7SVA in cervical lordosis.

STUDY DESIGN/SETTING

This was a retrospective radiographic study.

PATIENT SAMPLE

Forty-eight consecutive patients who underwent lateral standing radiography of the entire spine were retrospectively reviewed.

OUTCOME MEASURES

Radiographic parameters included occipito (Oc)-C7, Oc-C2, C2-C7, C2-C4, and C5-C7 angles; T1 slope; C7SVA; T1 pelvic angle (TPA); pelvic incidence; pelvic tilt; and sacral slope.

METHODS

The radiographs of 96 consecutive patients who underwent lateral standing radiography of the entire spine in June 2015 in our hospital were retrospectively reviewed. Patients having cervical deformities, having undergone cervical fusion, and under 18 years of age were excluded. A total of 48 Asian patients (14 men and 34 women; mean age, 54.6 years) were eligible. Pathologies included scoliosis, myelopathy, thoracolumbar deformity, and spondylosis. Spearman rank correlation coefficients were used to examine correlations between the parameters. The relationship between C5-C7 lordosis and the radiographic parameters was calculated using the forward stepwise multivariate regression analysis. The authors do not have financial associations relevant to this article.

RESULTS

C7SVA correlated with the Oc-C7 (r=0.42) and C2-C7 (r=0.50) angles. However, the correlation coefficient was smaller than that between the T1 slope and Oc-C7 (r=0.83) or C2-C7 (r=0.76) angles. When the C2-C7 angle was divided into C2-C4 and C5-C7 angles, C7SVA correlated with the C5-C7 (r=0.63) angle but not with the C2-C4 angle. The correlation coefficient between the C5-C7 angle and C7SVA was higher than that between the C5-C7 angle and T1 slope (r=0.53) or the C5-C7 angle and TPA (r=0.60). Using radiographic parameters and age, multiple regression analysis revealed that only C7SVA affected the C5-C7 angle.

CONCLUSIONS

C7SVA was the only radiographic parameter that affected the C5-C7 angle. Both T1 slope and C7SVA are key to the shape of the cervical sagittal alignment. The results of this study can be a starting point to improve our understanding of cervical sagittal alignment.

Correlation of cervical sagittal alignment parameters on full-length spine radiographs compared with dedicated cervical radiographs

BACKGROUND

Radiographic parameters to evaluate the cervical spine in adult deformity using 36-inch films have been proposed. While 36-inch films are used to evaluate spinal deformity, dedicated cervical films are more commonly used to evaluate cervical spine pathology. The purpose of this study is to determine correlations between sagittal measures from a dedicated cervical spine radiographs and 36-inch spine radiographs.

METHODS

Patients who had standing cervical and 36-inch radiographs within four weeks of each other were identified. On separate occasions, the following measures were determined: C0-C2, C0-C7, C1-C2 and C2-C7 sagittal Cobb angles; T1 slope; chin-brow-vertical angle (CBVA), C1-C7 sagittal vertical axis (SVA), C2-C7SVA, center of gravity-C7 sagittal vertical axis (COG-C7SVA). Paired t-tests and correlation analyses were done between parameters from the cervical and the 36-inch film.

RESULTS

Radiographic measurements were collected on 40 patients (33 females and 7 males, mean age of 48.9 ± 14.5 years). All correlations were statistically significant at p < 0.001. C0-C2 Cobb had the strongest correlation (r = 0.81) and C2-C7 Cobb had the weakest (r=0.62). Among sagittal balance parameters, COG-C7SVA had the weakest correlation (r = 0.42) and C1-C7SVA (r = 0.64) and the C2-C7SVA (r = 0.65) had strong correlations. The T1 slope and the CBVA had correlation coefficients of 0.74 and 0.91, respectively. There was no statistically significant difference in measures taken from the cervical film and 36-inch film, except for the C0-C7 Cobb (p = 0.000) with a measurement difference of 7° and the T1 tilt (p = 0.000) with a measurement difference of 5°.

CONCLUSION

Except for COG-C7 SVA, strong correlations between most cervical spine parameters taken from a dedicated cervical film and those taken from a 36-inch film were seen. 36-inch radiographs provide a reasonable estimation of cervical sagittal spine parameters and may obviate the need for a dedicated cervical spine radiograph.