Cervical spine alignment, sagittal deformity, and clinical implications: a review

Statistical modelling of how the sagittal alignment of the cervical spine is affected by adolescent idiopathic scoliosis and how scoliosis surgery changes that

The relationship between the sagittal shape of the cervical spine and that of the thoracolumbar spine is established in the normal spine. Adolescent idiopathic scoliosis (AIS) is recognised as a change in the shape of the spine in both the coronal and sagittal planes. The effects of AIS on the alignment of the cervical spine, including the effects of surgery, has been less well studied. The objective of this study was to identify, using regression analysis, the significant relationships between the alignment of the thoracolumbar spine, in both the coronal and sagittal planes, and the sagittal alignment of the cervical spine in AIS. This study used coronal and sagittal radiographic measures from a group with AIS, both pre and post-operatively, which were analysed using multiple linear regression methods to identify significant parameters that explain the sagittal shape of the cervical spine. There were 51 pairs of pre and post-operative radiographs analysed, 40 of which were Lenke 1 curves and 11 Lenke 3 curves. Posterior spinal fusion was performed for all. The significant parameters pre-operatively were T1 slope, thoracic kyphosis, lumbar lordosis and SVA with an R2 value of 78%. Post-operatively, the significant parameters were T1 slope, thoracic kyphosis, lumbar lordosis and thoracolumbar scoliosis with an R2 of 63%. The sagittal alignment of the cervical spine in AIS is related to the shape of key parameters in the rest of the spine. Changes in the cervical sagittal shape occur to compensate for changes in shape to the rest of the spine that occur as a consequence of surgery. This has implications for the understanding of how the compensatory mechanisms of the spine are used to maintain a horizontal gaze, along with prediction of the effects of surgery on the shape of the spine.

Does cervical curvature affect neurological outcome after incomplete spinal cord injury without radiographic abnormality (SCIWORA): 1-year follow-up

Background

At present, surgery is the primary clinical treatment for SCIWORA patients, but conservative treatment still plays an important role in patients with incomplete spinal cord injury. As an important index of cervical spine degeneration, cervical curvature has an impact on the prognosis of spinal cord injury patients. This paper studied the prognosis of conservatively treated patients with SCIWORA and the correlation between cervical curvature and neurological prognosis.

Methods

A retrospective study was conducted in all the patients with SCI admitted to the Third Affiliated Hospital of Hebei Medical University between January 2017 and June 2020. Data were recorded in 106 eligible patients, including sex, age, injury factors, Cobb angle, CCI, CSA, and ASIA motor and sensory scores. The Wilcoxon sign rank sum test was used to analyze the data postinjury and at the 1-year follow-up. Pearson correlation analysis was performed for the Cobb angle, CCI and CSA. Simple linear regression analysis and multiple linear regression analysis were performed for each group of variables.

Results

The Wilcoxon signed rank sum test confirmed that the Cobb angle, the CCI and the CSA of the patients were not significantly different at the 1-year follow-up when compared with the postinjury values, and the ASIA motor and sensory scores were significantly improved. The Pearson correlation analysis showed correlations among the Cobb angle, the CCI and the CSA. Simple linear regression analysis and multiple linear regression analysis showed that the nerve recovery rate was negatively correlated with age and was positively correlated with the Cobb angle.

Conclusion

Conservative treatment of incomplete SCIWORA can achieve a good prognosis. There is a clear correlation between the Cobb angle, CCI and CSA, and the Cobb angle, as an important influencing factor, needs to be considered. For SCIWORA patients undergoing nonsurgical treatment, improving cervical curvature is beneficial to the prognosis of patients. Age negatively affects the neurological prognosis.

Fatty infiltration in cervical extensor muscle: is there a relationship with cervical sagittal alignment after anterior cervical discectomy and fusion?

Purpose

To investigate the relationship between the preoperative paraspinal Goutalier grade of fatty infiltration and postoperative cervical sagittal alignment in patients undergoing anterior cervical discectomy and fusion (ACDF).

Methods

A total of 101 patients who underwent single-level ACDF with the Zero-profile implant system between March 2011 and April 2020 were included in this study. Cervical sagittal alignment parameters, including the C2-C7 Cobb angle, functional spinal unit (FSU) angle, cervical sagittal vertical axis (SVA), and T1 slope (T1S), were assessed. Preoperative magnetic resonance images were used to classify patients according to Goutalier grade. Clinical outcomes including Neck Disability Index (NDI) scores, Japanese Orthepaedic Association (JOA) scores and Visual Analogue Scale (VAS) scores were collected and analyzed.

Results

According to the Goutalier grade, 33 patients were classified as Goutalier 0–1 (Group A), 44 were classified as Goutalier 1.5–2 (Group B), and 24 were classified as Goutalier 2.5–4.0 (Group C). The mean age among the three groups showed significant differences (P = 0.007). At the last follow-up, the C2-C7 Cobb angle, FSU angle, and T1S improved after the surgery among the groups. Although there were varying degrees of loss of curvature among the different groups during the follow-up period, the postoperative cervical sagittal alignment parameters demonstrated no statistical differences among the three groups (P > 0.05). In addition, patients in all groups experienced significant relief of their symptoms, and the clinical scores were comparable among the groups (P > 0.05).

Conclusion

The complex nature of anterior cervical surgery requires surgical attention both in decompression and sagittal alignment. Our study demonstrates satisfactory postoperative cervical sagittal alignment of patients despite different grades of fatty infiltration of the multifidus muscle following single-level ACDF. Based on our results, the improvement and maintenance of cervical sagittal alignment after ACDF remains a complex problem that spine surgeons should consider before surgery.

The Impact of Upper Cervical Spine Alignment on Patient-reported Outcome Measures in Anterior Cervical Decompression and Fusion

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

To determine the extent to which the upper cervical spine compensates for malalignment in the subaxial cervical spine, and how changes in upper cervical spine sagittal alignment affect patient-reported outcomes.

SUMMARY OF BACKGROUND DATA

Previous research has investigated the relationship between clinical outcomes and radiographic parameters in the subaxial cervical spine following anterior cervical discectomy and fusion (ACDF). However, limited research exists regarding the upper cervical spine (occiput to C2), which accounts for up to 40% of neck movement and has been hypothesized to compensate for subaxial dysfunction.

MATERIALS AND METHODS

Patients undergoing ACDF for cervical radiculopathy and/or myelopathy at a single center with minimum 1-year follow-up were included. Radiographic parameters including cervical sagittal vertical axis, C0 angle, C1 inclination angle, C2 slope, Occiput-C1 angle (Oc-C1 degrees), Oc-C2 degrees, Oc-C7 degrees, C1-C2 degrees, C1-C7 degrees, and C2-C7 degrees cervical lordosis (CL) were recorded preoperatively and postoperatively. Delta (Δ) values were calculated by subtracting preoperative values from postoperative values. Correlation analysis as well as multiple linear regression analysis was used to determine relationships between radiographic and clinical outcomes. Alpha was set at 0.05.

RESULTS

A total of 264 patients were included (mean follow-up 20 mo). C2 slope significantly decreased for patients after surgery (Δ=-0.8, P =0.02), as did parameters of regional cervical lordosis (Oc-C7 degrees, C1-C7 degrees, and C2-C7 degrees; P <0.001, <0.001, and 0.01, respectively). Weak to moderate associations were observed between postoperative CL and C1 inclination ( r =-0.24, P <0.001), Oc-C1 degrees ( r =0.59, P <0.001), and C1-C2 degrees ( r =-0.23, P <0.001). Increased preoperative C1-C2 degrees and Oc-C2 degrees inversely correlated with preoperative SF-12 Mental Composite Score (MCS-12) scores ( r =-0.16, P =0.01 and r =-0.13, P =0.04). Cervical sagittal vertical axis was found to have weak but significant associations with Short Form-12 (SF-12) Physical Composite Score (PCS-12) ( r =-0.13, P =0.03) and MCS-12 ( r =0.12, P =0.05).

CONCLUSION

No clinically significant relationship between upper cervical and subaxial cervical alignment was detected for patients undergoing ACDF for neurological symptoms. Upper cervical spine alignment was not found to be a significant predictor of patient-reported outcomes after ACDF.

LEVEL OF EVIDENCE

Level III.

Biomechanical analysis of laminectomy, laminoplasty, posterior decompression with instrumented fusion, and anterior decompression with fusion for the kyphotic cervical spine

PURPOSE

Anterior and posterior decompressions for cervical myelopathy and radiculopathy may lead to clinical improvements. However, patients with kyphotic cervical alignment have sometimes shown poor clinical outcomes with posterior decompression. There is a lack on report of mechanical analysis of the decompression procedures for kyphotic cervical alignment.

METHODS

This study employed a three-dimensional finite element (FE) model of the cervical spine (C2-C7) with the pre-operative kyphotic alignment (Pre-OK) model and compared the biomechanical parameters (range of motion (ROM), annular stresses, nucleus stresses, and facet contact forces) for four decompression procedures at two levels (C3-C5); laminectomy (LN), laminoplasty (LP), posterior decompression with fusion (PDF), and anterior decompression with fusion (ADF). Pure moment with compressive follower load was applied to these models.

RESULTS

PDF and ADF models' global ROM were 40% at C2-C7 less than the Pre-OK, LN, and LP models. The annular and nucleus stresses decreased more than 10% at the surgery levels for ADF, and PDF, compared to the Pre-OK, LN, and LP models. However, the annular stresses at the adjacent cranial level (C2-C3) of ADF were 20% higher. The nucleus stresses of the caudal adjacent level (C5-C6) of PDF were 20% higher, compared to other models. The PDF and ADF models showed a less than 70% decrease in the facet forces at the surgery levels, compared to the Pre-OK, LN, and LP models.

CONCLUSION

The study concluded that posterior decompression, such as LN or LP, increases ROM, disc stress, and facet force and thus can lead to instability. Although there is the risk of adjacent segment disease (ASD), PDF and ADF can stabilize the cervical spine even for kyphotic alignments.

Instrumented fusion versus instrumented non-fusion following expansive open-door laminoplasty for multilevel cervical ossification of the posterior longitudinal ligament

PURPOSE

To compare the outcomes of expansive open-door laminoplasty with instrumented fusion (ELIF) and expansive open-door laminoplasty with instrumented non-fusion (ELINF) for multilevel cervical ossification of the posterior longitudinal ligament (OPLL).

METHODS

Patients who underwent ELIF or ELINF due to multilevel cervical OPLL from June 2013 to June 2019 were identified. Clinical and radiological outcomes were compared between the two groups.

RESULTS

A total of 78 patients were enrolled in this study with a minimum follow-up of 24 months, including 42 patients in the ELIF group and 36 patients in the ELINF group. At the final follow-up, sagittal vertical axis (SVA) and C2-C7 Cobb angle in the ELIF group were significantly better than those in the ELINF group, and cervical range of movement (ROM) in the ELIF group decreased significantly than that in the ELINF group. The incidence of OPLL progression at the final follow-up was 4.76% (2/42) in the ELIF group and 27.78% (10/36) in the ELINF group. Postoperative Japanese Orthopaedic Association (JOA) score, neck disability index (NDI), and visual analog scale (VAS) score improved significantly in each group, but JOA score and recovery rate (RR) in the ELIF group were significantly better than those in the ELINF group at the final follow-up. When K-line was positive, the difference in the final JOA score between the two groups was not significant, but the RR in the ELIF group was significantly better than that in the ELINF group. When K-line was negative, the final JOA score and RR in the ELIF group were significant higher than those in the ELINF group.

CONCLUSIONS

ELIF and ELINF were two effective surgical procedures for treating multilevel cervical OPLL. However, ELIF was superior to ELINF due to better postoperative JOA score and RR, significant improvement of C2-C7 Cobb angle and maintenance of SVA, and suppressant effect on OPLL progression, especially for patients with K-line ( - ) OPLL.

Patients With Preoperative Cervical Deformity Experience Similar Clinical Outcomes to Those Without Deformity Following 1-3 Level Anterior Cervical Decompression and Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim was to compare the outcomes of patients with incompletely corrected cervical deformity against those without deformity following short-segment anterior cervical decompression and fusion for clinically significant radiculopathy or myelopathy.

SUMMARY OF BACKGROUND DATA

Cervical deformity has increasingly been recognized as a driver of disability and has been linked to worse patient-reported outcomes measures (PROMs) after surgery.

METHODS

Patients 18 years or above who underwent 1-3 level anterior cervical decompression and fusion to address radiculopathy and/or myelopathy at a single institution between 2014 and 2018 with at least 1 year of PROMs were reviewed. Patients were categorized based on cervical deformity into 2 groups: sagittal vertebral axis (cSVA) ≥40 mm as the deformity group, and cSVA <40 mm as the nondeformity group. Patient demographics, surgical parameters, preoperative and postoperative radiographs, and minimum 1-year PROMs were compared.

RESULTS

Of the 230 patients, 191 (83%) were in the nondeformity group and 39 (17%) in the deformity group. Patients with deformity were more likely to be male (69.2% vs. 40.3%, P<0.001) and have a greater body mass index (32.8 vs. 29.7, P=0.028). The deformity group had significantly greater postoperative cSVA (44.2 vs. 25.1 mm, P<0.001) but also had significantly greater ∆cSVA (-4.87 vs. 0.25 mm, P=0.007) than the nondeformity group. Both groups had significant improvements in visual analog scale arm, visual analog scale neck, Short-Form 12 Physical Component Score, and neck disability index (NDI) (P<0.001). However, the deformity group experienced significantly greater ∆NDI and ∆mental component score (MCS)-12 scores (-19.45 vs. -11.11, P=0.027 and 7.68 vs. 1.32, P=0.009).

CONCLUSIONS

Patients with preoperative cervical sagittal deformity experienced relatively greater improvements in NDI and MCS-12 scores than those without preoperative deformity. These results suggest that complete correction of sagittal alignment is not required for patients to achieve significant clinical improvement.

LEVEL OF EVIDENCE

III.

Radiographic Characteristics of Cervical Deformity (CD) Using a Discriminant Analysis: The Value of Extension Radiographs

STUDY DESIGN

This was a retrospective review of a prospectively collected database.

OBJECTIVE

The aim of this study was to delineate radiographic parameters that distinguish severe cervical spine deformity (CSD).

SUMMARY OF BACKGROUND DATA

Our objective was to define parameters that distinguish severe CSD using a consensus approach combined with discriminant analysis as no system currently exists in the literature.

METHODS

Twelve CSD surgeons reviewed preoperative x-rays from a CSD database. A consensus was reached for categorizing patients into a severe cervical deformity (sCD), non-severe cervical deformity (non-sCD), or an indeterminate cohort. Radiographic parameters were found including classic cervical and spinopelvic parameters in neutral/flexion/extension alignment. To perform our discriminant analysis, we selected for parameters that had a significant difference between the sCD and non-sCD groups using the Student t test. A discriminant function analysis was used to determine which variables discriminate between the sCD versus non-sCD. A stepwise analysis was performed to build a model of parameters to delineate sCD.

RESULTS

A total of 146 patients with cervical deformity were reviewed (60.5±10.5 y; body mass index: 29.8 kg/m2; 61.3% female). There were 83 (56.8%) classified as sCD and 51 (34.9%) as non-sCD. The comparison analysis led to 16 radiographic parameters that were different between cohorts, and 5 parameters discriminated sCD and non-sCD. These parameters were cervical sagittal vertical axis, T1 slope, maximum focal kyphosis in extension, C2 slope in extension, and number of kyphotic levels in extension. The canonical coefficient of correlation was 0.689, demonstrating a strong association between our model and cervical deformity classification. The accuracy of classification was 87.0%, and cross-validation was 85.2% successful.

CONCLUSIONS

More than one third of a series of CSD patients were not considered to have a sCD. Analysis of an initial 17 parameters showed that a subset of 5 parameters can discriminate between sCD versus non-sCD with 85% accuracy. Our study demonstrates that flexion/extension images are critical for defining severe CD.

Simulating upright cervical lordosis in the supine position

Cervical alignment or lordosis evolution is still attained by direct radiography in standing position because an ideal cervical curvature is essential to maintain a horizontal gaze with minimal energy consumption. However, upright cervical lordosis changes in supine position. Anterior fusion surgery and more sophisticated radiological examinations, such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), are performed in lying position. Therefore, if upright cervical alignment can be simulated in the supine position, true (upright) cervical lordosis can be demonstrated on CT and MRI and also a more proper anterior cervical fusion can be performed in operation with better surgical outcomes. Forty-nine (49) adult patients underwent radiological examinations, including upright cervi- cal radiography and three session of supine MRI in different positions. MRI was performed in (1) conventional neutral supine position, (2) supine posi- tion with a 5-cm-high pillow, and (3) supine position with a 10-cm-high pillow under the shoulders. MRI results were analyzed. Wilcoxon, Kolmogorov-Smir- nov, and Spearman correlation tests were used to analyze MRI the validity in compared with those of cervical radiography. Cervical lordosis (C2-C7 Cobb angle) of the radiography group was similar to that of supine MRI group using a 5-cm-high pillow, and they have a strong correlation. The T-1 slope from radiography group was similar to and correlated with that of supine MRI groups with both pillows. Cranial tilt measurements of radiography group were different but correlated with the MRI group using a 5-cm-high pillow. Simulating upright cervical lordosis in the supine position is possible by adding a 5-cm- high pillow under the shoulders of the patients. This simulation reduces the need for direct radiography. Anterior cervical fusion surgery performed in this position can provide better surgical results.

Single-level cervical disc arthroplasty in the spine with reversible kyphosis: A finite element study

Background

Our previous studies found the single-level cervical disc arthroplasty (CDA) might be a feasible treatment for the patients with reversible kyphosis (RK). Theoretically, the change of cervical alignment from lordosis to RK comes with the biomechanical alteration of prostheses and cervical spine. However, the biomechanical data of CDA in the spine with RK have not been reported. This study aimed at establishing finite element (FE) models to (1) explore the effects of RK on the biomechanics of artificial cervical disc; (2) investigate the biomechanical differences of single-level anterior cervical discectomy and fusion (ACDF) and CDA in the cervical spine with RK.

Methods

The FE models of the cervical spine with lordosis and RK were constructed, then three single-level surgical models were developed: (1) RK + ACDF; (2) RK + CDA; (3) lordosis + CDA. A 73.6-N follower load combined with 1 N·m moment was applied at the C2 vertebra to produce cervical motion.

Results

At the surgical level, "lordosis + CDA" had the greatest ROM (except for flexion) while "RK + ACDF" had the minimum ROM. However, at adjacent levels, the ROM of "RK + ACDF" increased by 4.05% to 38.04% in comparison to "RK + CDA." "RK + ACDF" had the greatest prosthesis interface stress, while the maximum prosthesis interface stress of "RK + CDA" was at least 2.15 times higher than "lordosis + CDA." Similarly, "RK + ACDF" had the greatest intradiscal pressure (IDP) at adjacent levels, while the IDP of "RK + CDA" was 1.6 to 6.7 times higher than "lordosis + CDA." At the surgical level, "RK + CDA" had the greatest facet joint stress (except for extension), which was 1.9 to 11.2 times higher than "lordosis + CDA." At the adjacent levels, "RK + CDA" had the greatest facet joint stress (except for extension), followed by "RK + ACDF" and "lordosis + CDA" in descending order.

Conclusions

RK significantly changed the biomechanics of CDA, which is demonstrated by the decreased ROM and the significantly increased prosthesis interface stress, IDP, and facet joint stress in the "RK + CDA" model. Compared with ACDF, CDA overall exhibited a better biomechanical performance in the cervical spine with RK, with the increased ROM of surgical level and facet joint stress and the decreased ROM of adjacent levels, prosthesis interface stress, and IDP.

Analysis of Parameters That Can Predict the Cervical Sagittal Vertical Axis in Cervical Fusion Surgery

OBJECTIVE

The absolute value of the cervical sagittal parameters cannot be guaranteed with certainty on all follow-up cervical radiographs. With the assumption that neck posture changes can occur at any time at each follow-up radiographic session, we examined whether the sagittal parameters change meaningfully and identified the factors most closely related to the C2-C7 sagittal vertical axis (SVA).

METHODS

We enrolled 200 patients who had undergone either anterior cervical fusion (n = 100) or posterior cervical fusion (n = 100). The craniovertebral angle (CVA), mandible angle (MA), occipital slope (Os), C2 slope (C2s), C7 slope (C7s), and C2-C7 SVA were measured on 2 different follow-up radiographs after surgery. The C2-C7 angle (C2-C7A) and changes (Δ) in the sagittal parameters between the 2 radiographs were then calculated.

RESULTS

The ΔC2s and ΔCVA showed a very strong correlation with the ΔC2-C7 SVA (r = |0.70-0.93|). An independent t test showed a statistically significant difference for multiple sagittal parameters (i.e., ΔMA, ΔOs, ΔC2s, ΔC7s, and ΔCVA) between the large and small ΔC2-C7 SVA groups. In contrast, the change in the C2-C7A was without statistical significance. A stepwise multivariate regression analysis revealed a high adjusted R2 value (0.841) between the ΔC2-C7 SVA and 2 parameters (standardized coefficient: ΔCVA, -0.563; ΔC2s, -0.398).

CONCLUSIONS

During cervical fusion surgery, the CVA was the most predictable parameter reflecting the C2-C7 SVA in various analyses. The upper cervical parameters (Os and C2s) provided more explanatory power regarding the C2-C7 SVA changes than did the lower cervical parameter (C7s) or the presence of cervical lordosis (C2-C7A).

Correlation between the Photographic Cranial Angles and Radiographic Cervical Spine Alignment

The cranial vertical angle (CVA) and cranial rotation angle (CRA) are used in clinical settings because they can be measured on lateral photographs of the head and neck. We aimed to clarify the relationship between CVA and CRA photographic measurements and radiographic cervical spine alignment. Twenty-six healthy volunteers were recruited for this study. Lateral photographs and cervical spine radiographs were obtained in the sitting position. The CVA and CRA were measured using lateral photographs of the head and neck. The C2-7 sagittal vertical axis (SVA), cervical lordosis (C2-7), and occipito-C2 lordosis (O-C2) were measured using radiographic imaging as a standard method of evaluating cervical spine alignment. Correlations between the CVA and CRA on photographs and cervical spine alignment on radiographs were analyzed. The CVA and SVA were significantly negatively correlated (ρ = −0.51; p < 0.05). Significant positive correlations were found between CVA and C2-7 (ρ = 0.59; p < 0.01) and between CRA and O-C2 (ρ = 0.65; p < 0.01). Evaluating the CVA and CRA on photographs may be useful for ascertaining head and neck alignment in the mid-lower and upper parts of the sagittal plane.

Bridging the cervicothoracic junction during posterior cervical laminectomy and fusion for the treatment of multilevel cervical ossification of the posterior longitudinal ligament: a retrospective case series

BACKGROUND

The purpose of this study was to investigate the surgical efficacy of crossing the cervicothoracic junction during posterior cervical laminectomy and fusion for the treatment of multilevel cervical ossification of the posterior longitudinal ligament (OPLL).

METHODS

From October 2009 to October 2017, 46 consecutive patients with multilevel cervical OPLL underwent posterior cervical laminectomy and crossing the cervicothoracic junction fusion were obtained in the study. Their medical records were retrospectively collected. Cervical lordosis and cervical sagittal balance were used to assess radiographic outcomes. Japanese Orthopedic Association (JOA), axial symptom, C5 root palsy, blood loss, and operation time were used to assess clinical outcomes. The mean follow-up period was 20.7 ± 8.3 months.

RESULTS

The operation time was 205.2 ± 39.8 min and the intraoperative blood loss was 352.2 ± 143.7 ml. Analysis of the final follow-up data showed significant differences in JOA score (P < 0.01), C2-C7 lordosis angle (P < 0.01), and C2-C7 SVA (P < 0.01). CT confirmed that grafted bone was completely fused in all patients and progression of OPLL was observed in two patients (4.3%) at final follow-up. No adjacent segment disease (ASD) or instrument failure occurred in any patients.

CONCLUSIONS

Cervical laminectomy and crossing the cervicothoracic junction fusion are effective and safe methods to treat multilevel cervical OPLL. Randomized controlled studies compared constructs ending at cervical vertebrae or thoracic vertebrae are needed to confirm these results.

Evaluation Of Cervical Sagittal Parameters On Supine Magnetic Resonance Imaging In Patients With Chiari I Malformation Without Syringomyelia

OBJECTIVE

. The current study aimed to assess the effects of tonsillar herniation on cervical alignment in Chiari I patients without syringomyelia using new cervical sagittal alignment parameters, such as C0-2 Cobb angle, C2-7 cobb angle, T1 slope, and C2-7 sagittal vertical axis (SVA).

METHODS

Two spinal surgeons independently evaluated midline T2-weighted sagittal magnetic resonance imaging findings of 28 Chiari I patients without syringomyelia and 40 patients without tonsillar herniation but with similar complaints. Thereafter, the measured C0-2 Cobb angle, C2-7 Cobb angle T1 slope, and C2-7 SVA were compared using the t-test.

RESULTS

Differences in the mean values for C2-7 Cobb angle, T1 slope, and C2-7 SVA were found between Chiari I patients and those without tonsillar herniation Conclusion: The current study showed that Chiari I patients were less lordotic (kyphotic) compared to subjects without tonsillar herniation.

Variation of cervical sagittal alignment parameters according to gender, pelvic incidence and age

PURPOSE

The aim was to describe radiographic cervical sagittal alignment variations according to age, gender and pelvic incidence (PI) and to investigate relationships with thoracic alignment.

METHODS

A total of 2599 individuals (5-93 years) without spinal deformity were studied. Cranial cervical parameters were: McGregor slope, occipita-C2 angle, McGregor-C2 lordosis and C1-C2 lordosis. Caudal cervical parameters were: C2-C7, cranial arch and caudal arch lordosis and C7- and T1-slope. A Bayesian inference compared parameter distributions. Correlations with spinopelvic and global alignment parameters were investigated.

RESULTS

Among cranial cervical parameters, variations of McGregor slope were non-significant. McGregor-C2 lordosis and C1-C2 lordosis were smaller in males and increased significantly during growth, whereas the occipito-C2 angle decreased (Pr > 0.95). The occipito-C2 angle was larger and McGregor-C2 lordosis was smaller in low PI (Pr > 0.95). Among caudal cervical parameters, C2-C7 lordosis and C7- and T1-slope were larger in males and increased after 50 years (Pr > 0.95). Lordosis changes were non-significant in the cranial arch, whereas values increased in the caudal arch after 35 years (Pr > 0.95). Caudal parameter differences were non-significant between PI groups. Strong correlations existed between C2-C7, caudal arch lordosis, C7-slope, T1-slope and thoracic kyphosis. The sagittal vertical axis C2 correlated with caudal arch lordosis and T1-slope (ρ > 0.5; Pr > 0.95).

CONCLUSION

Cervical alignment parameters vary according to age, gender and PI. In the cranial cervical spine, changes occur mainly during growth. In the caudal cervical spine, lordosis increases in the caudal arch, which is related to thoracic kyphosis increase with age. The caudal cervical arch acts as a compensatory segment by progressive extension, allowing horizontal gaze.

Clinical outcomes and revision rates following four-level anterior cervical discectomy and fusion

Studies on outcomes after four-level anterior cervical discectomy and fusion (ACDF) are limited in the literature. The purpose of this study was to report on clinical outcomes and revision rates following four-level ACDF. Patients operated with four-level ACDF were identified in a prospectively accrued single institution database. Outcome scores included the Neck Disability Index (NDI) and Visual Analogue Scale (VAS) for neck and arm pain. Reoperation rates were determined. Any complications were identified from a review of the medical records. Twenty-eight patients with a minimum of 12 months follow up were included in the analysis. The mean age at surgery was 58.5 years. The median radiographic follow up time was 23 (IQR = 16–31.25) months. Cervical lordosis was significantly improved postoperatively (− 1 to − 13, p < 0.001). At the median 24 (IQR = 17.75–39.50) months clinical follow up time, there was a significant improvement in the NDI (38 to 28, p = 0.046) and VAS for neck pain scores (5.1 to 3, p = 0.012). The most common perioperative complication was transient dysphagia (32%) followed by hoarseness (14%). Four (14%) patients required revision surgery at a median 11.5 (IQR = 2–51) months postoperatively. The results of this study indicate that patients who undergo four-level ACDF have a significant improvement in clinical outcomes at median 24 months follow up. Stand-alone four-level ACDF is a valid option for the management of complex cervical degenerative conditions.

Subaxial lordosis loss and influence factors after posterior atlantoaxial fusion

Summary of background data

Cervical sagittal balance is an important evaluation index of cervical physiological function and surgical efficacy. Subaxial kyphosis after atlantoaxial fusion is negatively associated with worse clinical outcomes and higher incidence of lower cervical disk degeneration.

Objectives

This study aimed to confirm the factors that influence subaxial lordosis loss after posterior atlantoaxial fusion.

Methods

We performed a retrospective review of all patients following posterior C1–C2 fusion for atlantoaxial dislocation between January 2015 and December 2017. All charts, records, and imaging studies were reviewed for each case, and preoperative, immediate postoperative, and final follow-up plain films were evaluated. Comparing final follow-up and preoperative C2–C7 angle, patients were divided into two groups for further comparison: subaxial lordosis loss group and subaxial lordosis increase group.

Results

A total of 18 patients were included in the review, with an average radiographic follow-up of 8.4 ± 3.7 months (range 6–17 months). Subaxial lordosis loss was observed in 5 cases (27.8%) at the final follow-up, whereas 13 cases had an increase in subaxial lordosis. The cervical sagittal parameters of preoperative and final follow-up between two groups were compared, the preoperative C2–C7 angle of the subaxial lordosis loss group was bigger than the subaxial lordosis increase group (27.6° ± 10.5° vs 10.5° ± 10.5°, P < 0.05), but there was no statistical difference in other parameters. Univariate chi-square analysis showed that reduction in subaxial lordosis after posterior atlantoaxial fusion was associated with preoperative C2–C7 angle ≥ 20° (χ² = 4.923, P = 0.026). However, Logistic regression analysis showed that the preoperative C2–C7 angle ≥ 20° was not an independent risk factor (OR = 0.147, P = 0.225).

Conclusion

Our study demonstrates that subaxial lordosis loss may occur after posterior atlantoaxial fusion, and preoperative C2–C7 angle ≥ 20° was a risk factor of postoperative loss of subaxial lordosis.

Evaluation of cervical spine pathology in children with Loeys-Dietz syndrome

Background:

Loeys-Dietz syndrome (LDS) is a genetic connective tissue disorder associated with multiple musculoskeletal anomalies, including cervical spine instability. We sought to examine the nature of imaging for cervical spine instability in children with LDS due to likely pathogenic or pathogenic variants in TGFBR1, TGFBR2, TGFB2, SMAD3, or TGFB3.

Methods:

A retrospective chart review was conducted, examining relevant data for all children with LDS screened at our institution from 2004 through 2021. Cervical spine X-rays were used to assess cervical instability, cervical lordosis, and basilar impression.

Results:

A total of 39 patients were identified; 16 underwent cervical spine screening (56.25% male). Median age at initial screening was 7 years (Q1-Q3: 3.75–14, range: 0.1–19). Six of 16 patients evaluated (37.5%) had radiographical evidence of cervical instability. Mean angles of cervical lordosis were 20° (SD = 14.1°, range = 4°–33°) and 17.3° (SD = 16.4°, range = 2°–41°), respectively. Three patients demonstrated radiographical basilar impression. Radiographic progression of cervical instability was seen in one case. All but two were managed conservatively with observation, one patient underwent surgical fixation and fusion of C1-2, the other underwent complex cervical reconstruction anterior and posterior instrumentation.

Conclusion:

Cervical spine evaluation is important in this cohort; we identified 37.5% had evidence of cervical spine instability, and many had concurrent spinal pathology. From our experience, we agree with the recent advisement for screening at diagnosis and for those previously diagnosed that have not undergone screening. Future study may outline more specific screening practices.

Crossing the Cervicothoracic Junction in Multilevel Cervical Arthrodesis: A Systematic Review & Meta-Analysis

INTRODUCTION

In multisegment cervical arthrodeses, a common clinical dilemma for the surgeon is whether to extend the fusion past the cervicothoracic junction (CTJ).

OBJECTIVE

This meta-analysis compares clinical outcomes and radiological parameters when crossing and not crossing the CTJ.

METHODS

Our outcomes of interest included overall reoperation, successful fusion, adjacent segment disease (ASD) leading to revision surgery, estimated blood loss (EBL), length of stay (LOS). We also studied the postoperative change in radiological parameters - cervical sagittal vertical axis (cSVA), cervical lordosis (CL), and T1 slope (T1S) - and change in Neck Disability Index (NDI) and neck pain in Visual Analog Scale (VAS).

RESULTS

Thirteen studies with 1,720 patients were included. There were 974 (56.6%) patients in the non-crossing group and 746 (43.4%) patients in the crossing group. Non-crossing was associated with a higher risk of overall reoperation (RR=1.56; 95% CI:0.98-2.47) and ASD requiring revision surgery (RR=2.82; 95% CI:1.33-5.98; number-needed-to-harm = 22). The non-crossing group had lower EBL by 175 mL and shorter LOS by one day; the latter finding was only trending towards statistical significance. Successful fusion, as well as changes in cSVA, CL, NDI, and VAS were not different between the two groups at a statistically significant level.

CONCLUSIONS

In multilevel cervical arthrodesis, not crossing the CTJ is associated with a higher risk of overall reoperation and ASD requiring reoperation than crossing the CTJ, along with lower EBL and LOS. Differences in successful fusion, patient-reported outcomes, and sagittal radiological parameters were not significant.

Classification and citation analysis of the 100 top-cited articles on adult spinal deformity since 2011: A bibliometric analysis

BACKGROUND

Studies of the 100 most-cited articles are reported for many subjects. However, none has analyzed the article characteristics associated with high citation frequency. This study aims to (1) graphically depict characteristics of the 100 top-cited articles addressing adult spinal deformity (ASD), (2) diagram the association between articles according to subject and major topic medical subject headings (MeSHs), and (3) investigate whether major topic MeSH correlates with article citation frequency.

METHODS

The 100 top-cited ASD publications since 2011 were retrieved using a PubMed Central search on May 6, 2020. Using titles and abstracts, eight subject categories were identified: surgery, conservative treatment, normal values in spinopelvic alignment, review, cervical alignment, classification, compensatory mechanism, and spine-hip relationship. Sankey diagrams were used to organize the information. Network analysis was performed according to article subject and major topic MeSHs. Pearson's r was used to determine whether the weighted number of citations correlates with major topic MeSHs and the number of citations.

RESULTS

The average number of citations per article was 34.8 (range, 19-156). The most represented country was USA (n = 51). The most productive and highly cited journal was Spine (Phila Pa 1976) (n = 34; average, 38.2 citations per article). The most frequent subject categories and major topic MeSHs were "surgery" (n = 53) and "scoliosis" (weighted count, 9.8), while articles with the subject "compensatory" had the highest average number of citations (64.7). The most highly cited article, by Dr. F. Schwab in 2012, had 156 citations. Network analysis revealed the relationships between these articles according to major topic MeSHs. The weighted number of citations according to major topic MeSHs correlated significantly with article citation frequency (Pearson's r, 0.57; p < 0.001).

CONCLUSION

Multiple characteristics of the 100 top-cited ASD articles are presented in diagrams to guide evidence-based clinical decision-making in ASD.

Cervical Sagittal Alignment in Patients with Cervical Spondylotic Myelopathy: An Observational Study From the Canadian Spine Outcomes and Research Network

STUDY DESIGN

Prospective cohort study.

OBJECTIVE

Among patients with CSM, we aimed to evaluate the extent to which: (1) Preoperative cervical sagittal alignment is associated with health-related quality of life, function, and symptoms; (2) Surgery leads to changes in cervical sagittal alignment; and (3) Postoperative cervical sagittal alignment is associated with health-related quality of life, function, and symptoms at 12 months of follow-up.

SUMMARY OF BACKGROUND DATA

The importance of maintaining or improving cervical sagittal alignment in the surgical management of patients with CSM has not been established.

METHODS

We measured C2-C7 Cobb angle, T1 slope, and C2-C7 cervical sagittal vertical axis (cSVA). We tested for associations with Neck Disability Index, Pain Scales for neck and arm pain, EuroQol 5D, Short Form 12 Physical and Mental Component Summaries, and modified Japanese Orthopaedic Association scores. We adjusted for potential confounders using multiple linear regression, and we performed various prespecified subgroup (cSVA > 40 mm, surgical approach) and sensitivity analyses.

RESULTS

Among 250 patients, adjusted analyses yielded significant inverse associations prior to surgery between each of cSVA and T1 slope with SF12 Physical Component Summaries (T1 slope: -0.14, 95% CI -0.26 to -0.01, P = 0.03; C2-C7 cSVA: -0.13, 95% CI --0.21 to -0.05 P < 0.01). Surgery was associated with a small but statistically significant increase in cSVA across the cohort (+5.8 mm [SD 11.7], P < 0.01) but no change in Cobb angle or T1 slope. At 12-months after surgery, there were no significant associations between alignment parameters or change in alignment and any measures of health-related quality of life, function, or symptoms. Results were consistent across subgroup and sensitivity analyses.

CONCLUSION

Increased cSVA and T1 slope were associated with inferior health-related quality of life at presentation among patients with CSM, but no significant associations were observed following surgical treatment.Level of Evidence: 3.

Anterior Canal Reconstruction and Fusion for Myelopathy Caused by Degenerative Cervical Kyphosis and Stenosis With or Without Ossification of the Posterior Longitudinal Ligament

STUDY DESIGN

This was a retrospective study.

OBJECTIVE

To introduce an anterior surgical technique for myelopathy caused by degenerative cervical kyphosis and stenosis (DCKS) with or without ossification of the posterior longitudinal ligament (OPLL).

SUMMARY OF BACKGROUND DATA

The optimal approach in the treatment of DCKS remains a controversy because each anterior or posterior route surgery has advantages and disadvantages.

MATERIALS AND METHODS

In the period from June 2017 through June 2019, a consecutive cohort of adults diagnosed with DCKS underwent anterior canal reconstruction and fusion (ACRF). All patients underwent x-ray, computed tomography, and magnetic resonance imaging of the cervical spine. Radiologic assessment included kyphosis, canal area, canal reconstruction, OPLL, and spinal cord curvature and morphology. The Japanese Orthopaedic Association (JOA) scoring system was used to evaluate the neurological status. Surgery-related and implant-related complications were all recorded. Follow-up was carried out at 3, 6, 12, 24, and 36 months postoperation.

RESULTS

Fourty-one patients were included in the study, of which 19 presented with OPLL. Postoperatively, the canal area were significantly greater at last follow-up compared with preoperation (208.4 vs. 123.2 mm2; P=0.001). There was significant kyphosis correction (-17.6 vs. 8.5 degrees, P=0.001) at last follow-up. Ninety-six segmental canal reconstruction were performed, 89 (92.7%) reached bone fusion at both grooves with a mean time of 7.9 months. On sagittal magnetic resonance imaging, 33 (80.5%) patients presented with lordosis in the spinal cord curvature, 8 (19.5%) with straight. The mean JOA score at last follow-up was significantly better than preoperation (15.0 vs. 9.3 points; P<0.01). One patient presented with cerebrospinal fluid leakage, 1 with screw displacement and 2 with dysphagia.

CONCLUSION

ACRF, receiving good correction of kyphosis, amplified canal area, solid instrumented fusion and circumferential decompression, is an effective and safe surgical technique for cervical myelopathy caused by DCKS with or without OPLL.

LEVEL OF EVIDENCE

Level III-a retrospective analysis.

Incidence and Risk Factors of Mechanical Complications After Posterior-Based Osteotomies for Correction of Moderate to Severe Adult Cervical Deformity: 1-Year and 2-Year Follow-up

BACKGROUND

Rigid cervical deformity (CD) requires multilevel and/or high-grade osteotomies and long-construct fusions to achieve adequate correction. The incidence of mechanical complications (MCs) remains incompletely studied.

OBJECTIVE

To define the incidence and risk factors for MC.

METHODS

A retrospective review of consecutive patients with CD who underwent correction from 2010 to 2018 was performed. Inclusion criteria were cervical kyphosis >20° and/or cervical sagittal vertical axis (cSVA) >4 cm. MCs (junctional kyphosis/failure, pseudarthrosis, and implant failure) and reoperation at 1 and 2 yr were examined.

RESULTS

Eighty-three patients were included. The mean age was 63.4 yr, and 61.0% were female. Fifty-three percent underwent 3-column osteotomies. After surgery, cervical parameters were significantly improved: cSVA (6.2 vs 3.8 cm, P < .001), cervical lordosis (6.3 vs -8.3°, P < .001), cervical scoliosis (CS) (6.5 vs 2.2°, P < .001), and T1 slope (41.7 vs 36.3°, P = .007). The MC rate was 28.9%: junctional (18.1%), implant (16.9%), and pseudarthrosis (10.8%). MC rates at 1 and 2 yr were 14.5% and 25.5%, respectively: junctional (9.6% and 17.6%), implant (9.6% and 17.6%), and pseudarthrosis (2.4% and 7.8%). The overall reoperation rate was 24.1%: 14.5% at 1 yr and 19.6% at 2 yr. Body mass index (BMI) (P = .015) and preoperative CS (P = .040) were independently associated with higher odds of MC. Receiver operating characteristic curves defined CS >5° to be the threshold of risk for MCs and reoperation.

CONCLUSION

Correction of CD is effective by posterior-based osteotomes, but MCs are relatively high at 1 and 2 yr. BMI >30 and preoperative CS >5° predispose patients for MC and reoperation.

Comparison of Radiographic Reconstruction and Clinical Improvement between Artificial Cervical Disc Replacement and Anterior Cervical Discectomy and Fusion

Background

The surgical management of cervical degenerative disc degeneration (CDDD) has not reached a consensus. Artificial cervical disc replacement (ACDR) has been shown to be efficient in reducing symptoms after CDDD, although the topic remains highly controversial in this field. This study aimed to evaluate the effectiveness of ACDR on the treatment of CDDD on the aspect of radiographic reconstruction and clinical improvement compared with anterior cervical discectomy and fusion (ACDF).

Methods

This was a retrospective comparative study with 47 patients who underwent single-level ACDR and 46 patients who underwent single-level ACDF. The radiographic reconstruction was assessed by the cervical sagittal alignment parameters, consisting of two aspects, distance and angle, such as cervical sagittal vertical axis (cSVA), cervical lordosis (CL), T1 slope (T1s), and intervertebral space height (ISH). The clinical improvement was assessed by patient-related outcomes (PROs), consisting of two aspects, relief of axial neck pain and recovery of cervical dysfunction, measured through the Visual Analogue Scale (VAS), Neck Disability Index (NDI), and Japanese Orthopedic Association (JOA).

Results

Significant variations were achieved on aspects of radiographic reconstruction and clinical improvement after ACDR (P < 0.05), which were similar to that of the ACDF group (P < 0.05). A significantly larger postoperative range of motion (ROM) was found in patients less than 45 years of age in the ACDR group (P < 0.05). In addition, a significantly better postoperative JOA was found in patients with a preoperative ISH less than 4 mm in the ACDF group than that in the ACDR group (P < 0.05). Other than that mentioned above, no significant variations in radiographic and clinical outcomes were found between the two groups (P > 0.05).

Conclusions

Overall, this study showed that a similar capability in terms of radiographic reconstruction and clinical improvement was found between the two methods. Specific concerns should be analyzed while choosing between an ACDR and an ACDF. It should be pointed out that, based on our experience, if the patient is younger, ACDR is recommended; for patients with preoperative ISH less than 4 mm, ACDF is more recommended.

Comparison of sagittal vertical axis and decompression on the clinical outcome of cervical spondylotic myelopathy

OBJECTIVE

Decompression and cervical balance are major goals in the surgical treatment of cervical spondylotic myelopathy (CSM). Cervical balance is assumed to be a key factor for neurological recovery and pain reduction. Surgical reduction of C2-7 sagittal vertical axis (SVA) correlates with clinical improvement. However, it remains unclear, how much or even if correction is necessary for clinical improvement as long as surgery results in successful decompression. We aim to evaluate the role of radiological cervical balance parameter on the short-term course of CSM.

METHODS

This is a retrospective study with prospectively collected data of 90 patients. The authors identified 45 patients suffering from CSM that underwent decompressive surgery and instrumentation and showed an increased C2-7 sagittal vertical axis (SVA) after surgery. 45 consecutive patients with a decreased C2-7 SVA were selected as a control group.

RESULTS

Surgery improved the clinical outcome of both groups significantly. No differences could be seen comparing neck pain and neurological improvement between both groups. An increased C2-7 SVA did not correlate with an inferior clinical outcome. T1-slope correlated with the Cobb-angle.

CONCLUSIONS

Decompression and stabilization appear to be key elements of surgical treatment of CSM. In short terms, clinical improvement does not appear to affect patients negatively who show a larger C2-7 SVA after surgery. Optimal C2-7 SVA and necessity for a specific C2-7 correction is unclear. The term "balance" remains a complex entity without clear definition.

Global malalignment in adolescent idiopathic scoliosis: the axial deformity is the main driver

PURPOSE

To evaluate the global alignment of non-operated subjects with adolescent idiopathic scoliosis.

METHOD

A total of 254 subjects with AIS and 64 controls underwent low dose biplanar X-rays and had their spine, pelvis, and rib cage reconstructed in 3D. Global alignment was measured in the sagittal and frontal planes by calculating the OD-HA angle (between C2 dens to hip axis with the vertical). Subjects with AIS were classified as malaligned if the OD-HA was > 95th percentile relative to controls.

RESULTS

The sagittal OD-HA in AIS remained within the normal ranges. In the frontal plane, 182 AIS were normally aligned (Group 1, OD-HA = 0.9°) but 72 were malaligned (Group 2, OD-HA = 2.9°). Group 2 had a more severe spinal deformity in the frontal and horizontal planes compared to Group 1 (Cobb: 42 ± 16° vs. 30 ± 18°; apical vertebral rotation AVR: 19 ± 10° vs. 12 ± 7°, all p < 0.05). Group 2 subjects were mainly classified as Lenke 5 or 6. 19/72 malaligned subjects had a mild deformity (Cobb < 30°) but a progressive scoliosis (severity index ≥ 0.6). The frontal OD-HA angle was found to be mainly determined (adjusted-R² = 0.22) by the apical vertebral rotation and secondarily by the Lenke type.

CONCLUSIONS

This study showed that frontal malalignment is more common in distal major structural scoliosis and its main driver is the apical vertebral rotation. This highlights the importance of monitoring the axial plane deformity in order to avoid worsening of the frontal global alignment.

Do the newly proposed realignment targets bridge the gap between radiographic and clinical success in adult cervical deformity corrective surgery

Hypothesis:

The myelopathy-based cervical deformity (CD) thresholds will associate with patient-reported outcomes and complications.

Materials and Methods:

This study include CD patients (C2-C7 Cobb > 10°, CL > 10°, cervical sagittal vertical axis > 4 cm, or CBVA > 25°) with BL and 1-year (1Y) data. Modifiers assessed low (L), moderate (M), and severe (S) deformity: CL (L: >3°; M:-21° to 3°; S: <‒21°), TS-CL (L: <26°; M: 26° to 45°; S: >45°), C2-T3 angle (L: >‒25°; M:-35° to-25°; S: <‒35°), C2 slope (L: <33°; M: 33° to 49°; S: >49°), MGS (L: >‒9° and < 0°; M: ‒12° to ‒9° or 0° to 19°; S: < ‒12° or > 19°), and frailty (L: <0.18; M: 0.18–0.27, S: >0.27). Means comparison and ANOVA assessed outcomes in the severity groups at BL at 1Y. Correlations found between modifiers assessed the internal relationship.

Results:

One hundred and four patients were included in the study (57.1 years, 50%, 29.3 kg/m²). Baseline S TS-CL, C2-T3, and C2S modifiers were associated with increased reoperations (P < 0.01), while S MGS, CL, and C2-T3 had increased estimated blood lost (>1000ccs, P < 0.001). S MGS and C2-T3 had more postop DJK (60%, P = 0.018). Improvement in TS-CL, C2S, C2-T3, and CL patients had better numeric rating scale (NRS) back (<5) and EuroQOL 5-Dimension questionnaire (EQ5D) at 1 year (P < 0.05). Improving the modifiers correlated strongly with each other (0.213–0.785, P < 0.001). Worsened TS-CL had increased NRS back scores at 1 year (9, P = 0.042). Worsened CL had increased 1-year modified Japanese Orthopedic Association (mJOA) (7, P = 0.001). Worsened C2-T3 had worse NRS neck scores at 1 year (P = 0.048). Improvement in all six modifiers (8.7%) had significantly better health-related quality of life (HRQL) scores at follow-up (EQ5D, NRS, and Neck Disability Index).

Conclusions:

Newly proposed CD modifiers based on mJOA were closely associated with outcomes. Improvement and deterioration in the modifiers significantly impacted the HRQL.

Comparative Effectiveness and Safety of Open-Door Laminoplasty, French-Door Laminoplasty, Laminectomy and Fusion, and Laminectomy Alone for Multilevel Degenerative Cervical Myelopathy: A Bayesian Network Analysis

OBJECTIVES

To evaluate the comparative effectiveness and safety of open-door laminoplasty (OLP), French-door laminoplasty (FLP), laminectomy and fusion (LF), and laminectomy alone (LA) in treating multilevel degenerative cervical myelopathy (MDCM).

METHODS

Embase, PubMed, and Cochrane library were searched from their inception date to 7 January 2021. Randomized controlled trials and cohort studies comparing OLP, FLP, LF, and LA were identified to perform a network meta-analysis (NMA).

RESULTS

A total of 30 studies with 2671 patients were included. Our NMA results showed no significant difference between LF and OLP, but both are superior to LA and FLP in the comparison of JOA (Japanese Orthopaedic Association) score improvement. LF showed a most unsatisfactory outcome in postoperative range of motion (ROM) compared with LA or OLP or with FLP. For the complication outcome, no significant differences were found. The surface under the cumulative ranking curves (SUCRA) for JOA improvement was as follows: LF, OPL, LA, and FLP. For ROM reduction it was LA, OPL, FPL, and LF. For complications it was LF, LA, OLP, and FLP.

CONCLUSIONS

Considering all the evaluated criteria, none of the procedures showed the best outcome with least complications and optimal efficacy. However, OLP can be most recommended because of its second-ranking spectra in both of JOA improvement and ROM reduction, also with an acceptable incidence of complications, with the third least.

PRESENTATION OF THE MULTICENTRIC COLLECTION SPINE SURGERY DATABASE

ABSTRACT Objectives: To present the Spine Surgery Database developed by the Brazilian Spine Study Group and the methodology involved in its creation, in addition to presenting initial informationabout the use of the database. Methods: Description of the steps for selecting the questionnaires and variables to be included in the database, initial expansion of the use of the database tophysicians close to the BSSG, a brief exploration of quality control and methods for the inclusion ofnew centers, and training on the database, in addition to a brief descriptionof some of the data included in the database. Results: Currently, the database includes 428 patients who already underwent spine surgery and 9 collection centers with at least one patient collected. Conclusion: The Brazilian Spine Study Group’s Multicentric Collection Database is a viable tool that allows patients from different sourcesto be included within a common flow. Level of Evidence V; Expert opinion.

Use of a smartphone leveling application to optimize cervical thoracic alignment prior to posterior instrumentation

OBJECTIVE

Posterior cervical decompression and instrumentation (PCDI) is often associated with increase in sagittal balance and loss of lordosis. Here we propose a simple method of surgical positioning utilizing a readily available smartphone application to optimize cervical thoracic alignment in PCDI. The intent of this optimization is to minimize losses in lordosis and increases in sagittal balance.

METHODS

For patients since 2019, the position of the head was adjusted so that the occiput to thoracic spine was aligned and the chin brow angle was parallel to the rails of the surgical table utilizing a leveling smart application (RIDGID Level). Patients before 2019 who were not optimized were compared.

RESULTS

There were 13 patients in the nonoptimized cohort (NOC) and 20 in the optimized cohort (OC). In the NOC, the change in lordosis was -7° (p=0.016) and change in C2-SVA was 7 mm (p<0.001) from preoperative to postoperative values. In the OC, the change in lordosis was 2° (p=0.104) and change in C2-SVA was 2 mm (p=0.592) from preoperative to postoperative values. Between the NOC and OC cohorts, the changes in lordosis and sagittal balance between cohorts were significant (p=0.002 and p=0.001 respectively). There was no significant difference in clinical outcomes as measured by JOA or complication rates.

CONCLUSION

Positioning of the patient in preparation for PCDI can influence post-operative lordosis and sagittal balance. Using the leveling application on the smart phone (RIDGID Level), is a rapid and free alternative for the maintenance of lordosis and sagittal balance during instrumentation in the operating room.

One Hundred Top Cited Articles in Cervical Myelopathy: A Bibliographic Analysis

STUDY DESIGN

A bibliometric review of the literature.

OBJECTIVES

The aim of this study was to identify the most highly cited articles relating to cervical myelopathy and to analyze the most influential articles.

SUMMARY OF BACKGROUND DATA

Over the past several decades, a lot of research has been conducted regarding the subject of cervical myelopathy. Although there are a large number of articles on this topic, to our knowledge, this is the first bibliometric analysis.

METHODS

A selection of search terms and keywords were inputted into the "Dimensions" database and the most highly cited articles in cervical myelopathy were selected from high impact factor journals. The top 100 articles were analyzed for year of publication, authorship, publishing journals, institution and country of origin, subject matter, article type, and level of evidence.

RESULTS

The 100 most cited articles in the topic of cervical myelopathy were published from 1956 to 2015. These articles, their corresponding authors, and number of citations are shown in Table 1. The number of citations ranged from 121 times for the 100th article to 541 times for the top article in a total of 20 journals. The most common topic was operative technique, whereas the journals which contributed the most articles were the Spine journal and the Journal of Neurosurgery.

CONCLUSION

Our study provided an extensive list of the most historically significant articles regarding cervical myelopathy, acknowledging the key contributions made to the advancement of this field.Level of Evidence: 5.

Cervical alignment in the obese population following posterior cervical fusion for cervical myelopathy

STUDY DESIGN

Retrospective cohort study OBJECTIVE: The aim of this study was to investigate the effect of body mass index (BMI) on the reoperation rate and cervical sagittal alignment of patients who underwent posterior cervical decompression and fusion for cervical spondylotic myelopathy (CSM).

SUMMARY OF BACKGROUND DATA

Cervical sagittal balance has been correlated with postoperative clinical outcomes. Previous studies have shown worse postoperative sagittal alignment and higher reoperation rates in patients with high BMI undergoing anterior decompression and fusion. Similar evidence for the impact of obesity in postoperative sagittal alignment for patients with (CSM) undergoing posterior cervical decompression and fusion (PCF) is lacking.

METHODS

A retrospective analysis of 198 patients who underwent PCF for cervical myelopathy due to degenerative spine disease was performed. Demographics, need for reoperation, and perioperative radiographic parameters were collected. Cervical lordosis (CL), C2-7 sagittal vertical axis (SVA), and T1 slope (T1S) was measured on standing lateral radiographs. Comparative analysis of the patient cohort was performed by stratifying the sample population into three BMI categories (<25, 25-30, ≥30).

RESULT

Of the 198 patients that met inclusion criteria, 53 had BMI normal (<25), 65 were overweight (25-30), and 80 were obese (≥30). Mean SVA increased postoperatively in all groups, 4 mm in the normal group, 13 mm in the overweight group, and 13 mm in the obese group (p = 0.003). There was no significant difference in the postoperative change of cervical lordosis or T1 slope between the groups. Multivariate analysis demonstrated fusions involving the cervicothoracic junction and those involving 5 or more levels significantly affected alignment parameters. There were 27 complications requiring reoperation (14%) with no significant differences among the groups stratified by BMI (p = 0.386).

CONCLUSIONS

Overweight patients (BMI>25) with CSM undergoing PCF had a greater increase in SVA than normal weight patients while reoperation rates were similar. In addition, preoperative CL increased with increasing BMI, although this trend was not Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation significant and there was not found to be a significant difference between the change in CL from baseline to post-fusion between BMI cohorts. This study further highlights the importance of considering BMI when attempting to optimize sagittal alignment in patients undergoing PCF.

Risk factors for the development of degenerative cervical myelopathy: a review of the literature

Degenerative cervical myelopathy (DCM) encompasses various pathological conditions causing spinal cord (SC) impairment, including spondylosis (multiple level degeneration), degenerative disc disease (DDD), ossification of the posterior longitudinal ligament (OPLL), and ossification of the ligamentum flavum (OLF). It is considered the most common cause of SC dysfunction among the adult population. The degenerative phenomena of DDD, spondylosis, OPLL and OLF, is likely due to both inter-related and distinct factors. Age, cervical alignment, and range of motion, as well as congenital factors such as cervical cord-canal mismatch due to congenital stenosis, Klippel-Feil, Ehler-Danlos, and Down syndromes have been previously reported as potential factors of risk for DCM. The correlation between some comorbidities, such as rheumatoid arthritis and movement disorders (Parkinson disease and cervical dystonia) and DCM, has also been reported; however, the literature remains scare. Other patient-specific factors including smoking, participation in contact sports, regular heavy load carrying on the head, and occupation (e.g. astronauts) have also been suggested as potential risk of myelopathy development. Most of the identified DCM risk factors remain poorly studied however. Further researches will be necessary to strengthen the current knowledge on the subject, especially concerning physical labors in order to identify patients at risk and to develop an effective treatment strategy for preventing this increasing prevalent disorder.

The Morphological Changes in Adjacent Segments Amongst Patients Receiving Anterior and Oblique Lumbar Interbody Fusion: A Retrospective Study

Adjacent segment disease (ASD) is troublesome condition that has proved to be highly related to spinal malalignment after spinal surgery. Hence, we aimed to evaluate the morphological changes after anterior lumbar interbody fusion (ALIF) and oblique LIF (OLIF) to establish the differences between the two surgical methods in terms of possible ASD avoidance. Fifty patients, half of whom received ALIF while the other half received OLIF, were analyzed with image studies and functional outcomes during the pre-operative and post-operative periods, and 2 years after surgery. Image measurements obtained included spinal-pelvic parameters, index lordosis (IL), segmental lordosis (SL), anterior disc height (ADH), posterior disc height (PDH) and adjacent segment disc angle (ASDA). The ADH and PDH in the adjacent segment decreased in the two groups while OLIF showed greater decrease without radiological ASD noted at 2-year follow-up. Both groups showed an increase in IL after surgery while ALIF showed greater improvement. No statistical difference was identified in functional outcomes between LIFs. We suggest that both ALIF and OLIF can restore adequate lordosis and prevent ASD after surgery. However, it should be noted that patient selection remains crucial when making any decision involving which of the two methods to use.

Audit and Comparison Between Radiographic Markers of Gaze Direction Using EOS Imaging - An Essential Step to Streamline Existing Methods

STUDY DESIGN

Retrospective cohort study on prospectively implemented EOS protocol.

OBJECTIVE

This study aims to audit and compare existing radiological definitions of gaze direction-chin brow vertical angle (CBVA), McGregor slope (McGS), slope of line of sight (SLS), orbital-internal occipital protuberance (OIOP) slope angle, and Tangent to the hard palate (THP) in a neutral, healthy, and asymptomatic cohort.

SUMMARY OF BACKGROUND DATA

The ability to accurately define direction of gaze is the first step when striving for horizontal gaze restoration in any affected individual with rigid sagittal deformity. Yet, the radiological definition of gaze direction remains poorly standardized.

METHODS

Hundred healthy subjects who could achieve horizontal gaze underwent whole-body standing EOS radiographs taken under a strictly standardized protocol. Radiographic measurements of global spinal sagittal parameters and surrogate measures of horizontal gaze were analyzed and compared.

RESULTS

The mean age was 45 ± 15.9 years, with a balanced male-to-female-ratio. Their C7 SVA was -7.7 mm ± 24.8 mm, PI was 51.0o ± 11.4o, PI-LL was -0.9o ± 13.0o and T1-slope was 21.2o ± 9.2o. Measured horizontal gaze parameters were as follows: CBVA (1.07o ± 5.48o), McGS (-3.23o ± 5.63o), SLS (0.45o ± 5.34o), OIOP (5.03o ± 4.66o), THP (-0.17o ± 6.27o). CBVA correlated strongly with McGS (r = 0.679, P < 0.001), SLS (r = 0.592, P < 0.001), OIOP (r = 0.697, P < 0.001), and THP (r = -0.504, P < 0.001). OIOP had the lowest variance amongst all parameters and showed less variability compared to CBVA (SD 4.66 Var 21.69 vs. SD 5.48 Var 30.08, P = .012). Multivariate analysis showed that C2-7 angle was the only parameter found to be associated with OIOP values (P = 0.006).

CONCLUSION

OIOP is the least variable, and most robust radiological method in determining gaze direction. It uses easily recognizable anatomical landmarks and an angular criterion, which makes it advantageous both with x-rays or slot scanners.Level of Evidence: 3.

Etiology and treatment of cervical kyphosis: state of the art review-a narrative review

Objective

To provide state of the art review regarding cervical kyphosis.

Background

Cervical spine kyphosis has been increasingly common due to the growing elderly population. Clinicians should comprehensively understand its symptoms, biomechanics, etiology, radiographic evaluation, classification, and treatment options and complications of each treatment. Comprehensive review will help clinicians improve the management for patients with cervical kyphosis.

Methods

The available literature relevant to cervical kyphosis was reviewed. PubMed, Medline, OVID, EMBASE, and Cochrane were used to review the literature.

Conclusions

This article summarizes current concepts regarding etiology, evaluation, surgical treatment, complications and outcomes of cervical kyphosis. Major etiologies of cervical kyphosis include degenerative, post-laminectomy, and ankylosing spondylitis. Clinical presentations include neck pain, myelopathy, radiculopathy, and problems with horizontal gaze, swallowing and breathing. Cervical lordosis, C2-7 sagittal vertical axis, chin-brow to vertical angle, and T1 slope should be evaluated from upright lateral 36-inch film. The most widely used classification system includes a deformity descriptor and 5 modifiers. A deformity descriptor provides a basic grouping of the deformity consisting of five types, cervical, cervicothoracic, thoracic, coronal cervical deformity, and cranio-vertebral junction deformity. The 5 modifiers include C2-7 sagittal vertical axis, chin-brow to vertical angle, T1 slope minus cervical lordosis, myelopathy based on modified Japanese Orthopaedic Association score, and SRS-Schwab classification for thoracolumbar deformity. Current treatment options include anterior discectomy and fusion, anterior osteotomy, Smith-Peterson osteotomy, pedicle subtraction osteotomy, or a combination of these based on careful preoperative evaluation.

Prioritization of realignment associated with superior clinical outcomes for surgical cervical deformity patients

Background:

To optimize quality of life in patients with cervical deformity (CD), there may be alignment targets to be prioritized.

Objective:

To prioritize the cervical parameter targets for alignment.

Methods:

Included: CD patients (C2–C7 Cobb >10^°°, C2–C7 lordosis [CL] >10^°°, cSVA > 4 cm, or chin-brow vertical angle >25^°°) with full baseline (BL) and 1-year (1Y) radiographic parameters and Neck Disability Index (NDI) scores; patients with cervical (C) or cervicothoracic (CT) Primary Driver Ames type. Patients with BL Ames classified as low CD for both parameters of cSVA (<4 cm) and T1 slope minus CL (TS-CL) (<15^°°) were excluded. Patients assessed: Meeting Minimal Clinically Important Difference (MCID) for NDI (<−15 ΔNDI). Ratios of correction were found for regional parameters categorized by Primary Ames Driver (C or CT). Decision tree analysis assessed cut-offs for differences associated with meeting NDI MCID at 1Y.

Results:

Seventy-seven CD patients (62.1 years, 64%F, 28.8 kg/m²). 41.6% met MCID for NDI. A backward linear regression model including radiographic differences as predictors from BL to 1Y for meeting MCID for NDI demonstrated an R²= 0.820 (P = 0.032) included TS-CL, cSVA, MGS, C2SS, C2-T3 angle, C2-T3 sagittal vertical axis (SVA), CL. By primary Ames driver, 67.5% of patients were C, and 32.5% CT. Ratios of change in predictors for MCID NDI patients for C and CT were not significant between the two groups (P > 0.050). Decision tree analysis determined cut-offs for radiographic change, prioritizing in the following order: ≥42.5^° C2-T3 angle, >35.4^° CL, <−31.76^° C2 slope, <−11.57 mm cSVA, <−2.16^° MGS, >−30.8 mm C2-T3 SVA, and ≤−33.6^° TS-CL.

Conclusions:

Certain ratios of correction of cervical parameters contribute to improving neck disability. Prioritizing these radiographic alignment parameters may help optimize patient-reported outcomes for patients undergoing CD surgery.

Risk-benefit assessment of major versus minor osteotomies for flexible and rigid cervical deformity correction

Introduction:

Osteotomies are commonly performed to correct sagittal malalignment in cervical deformity (CD). However, the risks and benefits of performing a major osteotomy for cervical deformity correction have been understudied. The objective of this retrospective cohort study was to investigate the risks and benefits of performing a major osteotomy for CD correction.

Methods:

Patients stratified based on major osteotomy (MAJ) or minor (MIN). Independent t-tests and Chi-squared tests were used to assess differences between MAJ and MIN. A sub-analysis compared patients with flexible versus rigid CL.

Results:

137 CD patients were included (62 years, 65% F). 19.0% CD patients underwent a MAJ osteotomy. After propensity score matching for cSVA, 52 patients were included. About 19.0% CD patients underwent a MAJ osteotomy. MAJ patients had more minor complications (P = 0.045), despite similar surgical outcomes as MIN. At 3M, MAJ and MIN patients had similar NDI, mJOA, and EQ5D scores, however by 1 year, MAJ patients reached MCID for NDI less than MIN patients (P = 0.003). MAJ patients with rigid deformities had higher rates of complications (79% vs. 29%, P = 0.056) and were less likely to show improvement in NDI at 1 year (0.95 vs. 0.54, P = 0.027). Both groups had similar sagittal realignment at 1 year (all P > 0.05).

Conclusions:

Cervical deformity patients who underwent a major osteotomy had similar clinical outcomes at 3-months but worse outcomes at 1-year as compared to minor osteotomies, likely due to differences in baseline deformity. Patients with rigid deformities who underwent a major osteotomy had higher complication rates and worse clinical improvement despite similar realignment at 1 year.

Predictive model for achieving good clinical and radiographic outcomes at one-year following surgical correction of adult cervical deformity

Background

For cervical deformity (CD) surgery, goals include realignment, improved patient quality of life, and improved clinical outcomes. There is limited research identifying patients most likely to achieve all three.

Objective

The objective is to create a model predicting good 1-year postoperative realignment, quality of life, and clinical outcomes following CD surgery using baseline demographic, clinical, and radiographic factors.

Methods

Retrospective review of a multicenter CD database. CD patients were defined as having one of the following radiographic criteria: Cervical sagittal vertical axis (cSVA) >4 cm, cervical kyphosis/scoliosis >10°° or chin-brow vertical angle >25°. The outcome assessed was whether a patient achieved both a good radiographic and clinical outcome. The primary analysis was stepwise regression models which generated a dataset-specific prediction model for achieving a good radiographic and clinical outcome. Model internal validation was achieved by bootstrapping and calculating the area under the curve (AUC) of the final model with 95% confidence intervals.

Results

Seventy-three CD patients were included (61.8 years, 58.9% F). The final model predicting the achievement of a good overall outcome (radiographic and clinical) yielded an AUC of 73.5% and included the following baseline demographic, clinical, and radiographic factors: mild-moderate myelopathy (Modified Japanese Orthopedic Association >12), no pedicle subtraction osteotomy, no prior cervical spine surgery, posterior lowest instrumented vertebra (LIV) at T1 or above, thoracic kyphosis >33°°, T1 slope <16 and cSVA <20 mm.

Conclusions

Achievement of a positive outcome in radiographic and clinical outcomes following surgical correction of CD can be predicted with high accuracy using a combination of demographic, clinical, radiographic, and surgical factors, with the top factors being baseline cSVA <20 mm, no prior cervical surgery, and posterior LIV at T1 or above.

Multilevel, Percutaneous Posterior Cervical Interfacet Distraction and Fusion for Cervical Spondylotic Radiculopathy: Clinical and Radiographic Outcomes

STUDY DESIGN

Retrospective review of patients who underwent multilevel posterior cervical interfacet distraction and fusion (PCIDF) using cages for cervical spondylotic radiculopathy (CSR).

OBJECTIVE

To determine clinical and radiographic outcomes following multilevel PCIDF.

SUMMARY OF BACKGROUND DATA

Anterior cervical discectomy and fusion has long been the standard of treatment for CSR. Advancements in surgery have employed minimally invasive techniques such as endoscopic discectomy, foraminotomy, and PCIDF. Studies on single-level PCIDF have reported good clinical outcomes, short hospital stays, and rare complications, but its application in multilevel disease is still evolving.

METHODS

Patients with CSR and confirmed radiologic evidence of multilevel foraminal stenosis without central canal stenosis were reviewed. Two-year outcomes of multilevel PCIDF included Neck Disability Index, neck and arm Visual Analogue Scale (VAS), radiographic cervical alignment parameters, evidence of fusion, and incidence of adjacent segment degeneration were compared at different time points.

RESULTS

Thirty patients (mean age 54.6 ± 8.3) were included in the study with an average of 3.4 ± 0.8 levels treated. Mean surgical duration and intraoperative blood loss was 143.2 ± 69.7 minutes and 27.7 ± 28.7 mL, respectively, with an average length of stay at 1.8 ± 1.5 days. Neck Disability Index, VAS-neck, and VAS-arm all significantly improved at 2 weeks (P < 0.001) and was maintained until 2 years postoperatively. A significant decrease in segmental and C2-C7 lordosis, with a corresponding increase in sagittal vertical axis, was observed at 3 months postoperatively (P < 0.001) but did not deteriorate further on subsequent visits. Successful fusion was achieved in 90% of patients after 2 years. There was a 13.3% incidence of adjacent segment degeneration in the study cohort and one perioperative complication (3.3%).

CONCLUSION

Our study suggests that multilevel PCIDF is safe and effective for CSR caused by foraminal stenosis. However, its potential to cause kyphosis and clinical impact on global sagittal alignment requires further scrutiny and long-term evaluation.Level of Evidence: 4.

Reliability assessment of cervical spine parameters measured on full-body radiographs in asymptomatic subjects and patients with spinal deformity

BACKGROUND

Cervical spinal alignment is usually assessed on full-body radiographs allowing for the concomitant evaluation of possible compensatory mechanisms that may occur at any level in the setting of postural malalignment.

HYPOTHESIS

Cervical parameters measured on full-body radiographs are reliable.

PATIENTS AND METHODS

A total of 70 subjects were included and divided in 3 groups: asymptomatic adults (n=21), adolescents with idiopathic scoliosis (n=20), and adults with spinal deformity (n=29), for whom full-body low-dose biplanar radiographs were obtained. Eighteen cervical parameters including gaze and cervical curvature, upper cervical spine, global cervical alignment, thoraco-cervical and cervico-pelvic parameters were measured by 4 operators, three times each. The intraclass correlation coefficient (ICC) and the 95% confidence interval (95% CI) where calculated for each parameter and compared between the 3 groups.

RESULTS

ICC and the 95% CI were similar between the 3 groups. The measured parameters showed a very high repeatability (ICC>0.8) except for C0-C2, which presented an average repeatability (ICC=0.57). The cSVA, CTPA, C2-SPi, cranial offset, T1-SPi, CBVA and cranial tilt had a 95% CI<2 (° or cm). The TIA, T1-CL and C0-C2 had a 95% CI>6°.

DISCUSSION

The poor visibility of the foramen magnum, hard palate, C7, T1, and the sternum on radiographs could explain why certain parameters showed a higher measurement error. The assessment of these error margins is essential for an accurate evaluation of cervical spinal deformities and a proper therapeutic approach.

LEVEL OF EVIDENCE

III; retrospective analysis of prospectively collected data.

The Effect of Laminectomy with Instrumented Fusion Carried into the Thoracic Spine on the Sagittal Imbalance in Patients with Multilevel Ossification of the Posterior Longitudinal Ligament

OBJECTIVE

To determine if there is a difference in either the cervical alignment or the clinical outcomes in cervical ossification of the posterior longitudinal ligament (OPLL) patients who underwent laminectomy with instrumented fusion (LIF) ending at C₆ , C₇ , or proximal thoracic spine for the treatment of multilevel OPLL, and to find out the appropriate distal fusion level.

METHODS

This was a single-center retrospective study. In total, 36 patients with cervical OPLL who underwent three or more level LIF in our institution between January 2015 and January 2017 were enrolled. They were divided into three groups according to their distal ends: C₆ (nine females and 11 males, 60.45 ± 9.68 years old), C₇ (four females and six males, 61.60 ± 10.29 years old), and T-group (two females and four males, 64.33 ± 8.12 years old). Radiographic (compression level, classification of OPLL, occupying rate, C_2-7 cobb angle, C_2-7 sagittal vertical axis, and fusion level) and clinical outcomes (NDI score, operative time, and blood loss) were compared. Predictors of postoperative sagittal imbalance were also identified according to if the postoperative C_2-7 SVA was greater than 40 mm. The sensitivity and specificity of preoperative parameters predicting postoperative cervical stability were evaluated via the receiver operating characteristic (ROC) curve.

RESULTS

All patients were followed up at least 1 year. The blood loss in T group was significantly more than C₆ or C₇ group. The length of fusion level became significantly longer when the caudal level extended to the thoracic spine. The age, preoperative SVA, and NDI score at follow-up were significantly greater in the imbalance group. At the final follow-up, the cervical lordosis tended to be straight and the C_2-7 SVA tended to be greater when the caudal level of fusion was extended to upper thoracic segment. Further ROC curve analysis suggested that patients' age had a sensitivity of 75.00%, specificity of 79.17% for cervical stability, and the AUC was 0.844 (P < 0.01), with the cutoff value for age being 66.5 years old. For preoperative SVA, the sensitivity was 58.30%, and specificity was 91.70%, with the AUC of 0.778 (P < 0.01). The cutoff value for preoperative SVA was 30.4 mm.

CONCLUSION

Although posterior fusion terminating in the thoracic spine was not superior to the cervical spine for patients with multilevel OPLL, for elderly patients (>67 years) with great preoperative SVA (>30 mm), terminating at C₆ was recommended to limit the invasion of cervical extensor muscles, provided the decompression was adequate.

At What Point Should the Thoracolumbar Region Be Addressed in Patients Undergoing Corrective Cervical Deformity Surgery?

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim of this study was to investigate the impact of cervical to thoracolumbar ratios on poor outcomes in cervical deformity (CD) corrective surgery.

SUMMARY OF BACKGROUND DATA

Consideration of distal regional and global alignment is a critical determinant of outcomes in CD surgery. For operative CD patients, it is unknown whether certain thoracolumbar parameters play a significant role in poor outcomes and whether addressing such parameters is warranted.

METHODS

Included: surgical CD patients (C2-C7 Cobb >10°, cervical lordosis [CL] >10°, C2-C7 sagittal vertical axis (cSVA) >4 cm, or chin-brow vertical angle >25°) with baseline and 1-year data. Patients were assessed for ratios of preop cervical and global parameters including: C2 Slope/T1 slope, T1 slope minus C2-C7 lordosis (TS-CL)/mismatch between pelvic incidence and lumbar lordosis (PI-LL), cSVA/sagittal vertical axis (SVA). Deformity classification ratios of cervical (Ames-ISSG) to spinopelvic (SRS-Schwab) were investigated: cSVA modifier/SVA modifier, TS-CL modifier/PI-LL modifier. Cervical to thoracic ratios included C2-C7 lordosis/T4-T12 kyphosis. Correlations assessed the relationship between ratios and poor outcomes (major complication, reoperation, distal junctional kyphosis (DJK), or failure to meet minimal clinically important difference [MCID]). Decision tree analysis through multiple iterations of multivariate regressions assessed cut-offs for ratios for acquiring suboptimal outcomes.

RESULTS

A total of 110 CD patients were included (61.5 years, 66% F, 28.8 kg/m2). Mean preoperative radiographic ratios calculated: C2 slope/T1 slope of 1.56, TS-CL/PI-LL of 11.1, cSVA/SVA of 5.4, CL/thoracic kyphosis (TK) of 0.26. Ames-ISSG and SRS-Schwab modifier ratios: cSVA/SVA of 0.1 and TS-CL/PI-LL of 0.35. Pearson correlations demonstrated a relationship between major complications and baseline TS-CL/PI-LL, Ames TS-CL/Schwab PI-LL modifiers, and the CL/TK ratios (P < 0.050). Reoperation had significant correlation with TS-CL/PI-LL and cSVA/SVA ratios. Postoperative DJK correlated with C2 slope/T1 slope and CL/TK ratios. Not meeting MCID for Neck Disability Index (NDI) correlated with CL/TK ratio and not meeting MCID for EQ5D correlated with Ames TS-CL/Schwab PI-LL.

CONCLUSION

Consideration of cervical to global alignment is a critical determinant of outcomes in CD corrective surgery. Key ratios of cervical to global alignment correlate with suboptimal clinical outcomes. A larger cervical lordosis to TK predicted postoperative complication, DJK, and not meeting MCID for NDI.Level of Evidence: 4.

Systematic Review of Reciprocal Changes after Spinal Reconstruction Surgery : Do Not Miss the Forest for the Trees

The purpose of this review was to synthesize the research on global spinal alignment and reciprocal changes following cervical or thoracolumbar reconstruction surgery. We carried out a search of PubMed, EMBASE, and Cochrane Library for studies through May 2020, and ultimately included 11 articles. The optimal goal of a truly balanced spine is to maintain the head over the femoral heads. When spinal imbalance occurs, the human body reacts through various compensatory mechanisms to maintain the head over the pelvis and to retain a horizontal gaze. Historically, deformity correction has focused on correcting scoliosis and preventing scoliotic curve progression. Following substantial correction of a spinal deformity, reciprocal changes take place in the flexible segments proximal and distal to the area of correction. Restoration of lumbar lordosis following surgery to correct a thoracolumbar deformity induces reciprocal changes in T1 slope, cervical lordosis, pelvic shift, and lower extremity parameters. Patients with cervical kyphosis exhibit different patterns of reciprocal changes depending on whether they have head-balanced or trunk-balanced kyphosis. These reciprocal changes should be considered to in order to prevent secondary spine disorders. We emphasize the importance of evaluating the global spinal alignment to assess postoperative changes.

Utility of intraoperative neuromonitoring and outcomes of neurological complication in lower cervical and upper thoracic posterior-based three-column osteotomies for cervical deformity

OBJECTIVE

For severe and rigid adult cervical deformity, posterior-based three-column osteotomies (3COs) are warranted, but neurological complications are relatively high with such procedures. The performance measures of intraoperative neuromonitoring (IONM) during cervicothoracic 3CO have yet to be studied, and there remains a paucity of literature regarding the topic. Therefore, the authors of this study examined the performance of IONM in predicting new neurological weakness following lower cervical and upper thoracic 3CO. In addition, they report the 6-month, 1-year, and 2-year outcomes of patients who experienced new postoperative weakness.

METHODS

The authors performed a retrospective review of a single surgeon's experience from 2011 to 2018 with all patients who had undergone posterior-based 3CO in the lower cervical (C7) or upper thoracic (T1-4) spine. Medical and neuromonitoring records were independently reviewed.

RESULTS

A total of 56 patients were included in the analysis, 38 of whom had undergone pedicle subtraction osteotomy and 18 of whom had undergone vertebral column resection. The mean age was 61.6 years, and 41.1% of the patients were male. Among the study cohort, 66.1% were myelopathic and 33.9% had preoperative weakness. Mean blood loss was 1565.0 ml, and length of surgery was 315.9 minutes. Preoperative and postoperative measures assessed were cervical sagittal vertical axis (6.5 and 3.8 cm, respectively; p < 0.001), cervical lordosis (2.3° and -6.7°, p = 0.042), and T1 slope (48.6° and 35.8°, p < 0.001). The complication rate was 49.0%, and the new neurological deficit rate was 17.9%. When stratifying by osteotomy level, there were significantly higher rates of neurological deficits at C7 and T1: C7 (37.5%), T1 (44.4%), T2 (16.7%), T3 (14.3%), and T4 (0.0%; p = 0.042). Most new neurological weakness was the nerve root pattern rather than the spinal cord pattern. Overall, there were 16 IONM changes at any threshold: 14 at 50%, 8 at 75%, and 13 if only counting patients who did not return to baseline (RTB). Performance measures for the various thresholds were accuracy (73.2% to 77.8%), positive predictive value (25.0% to 46.2%), negative predictive value (81.3% to 88.1%), sensitivity (18.2% to 54.5%), and specificity (77.8% to 86.7%). Sensitivity to detect a spinal cord pattern of weakness was 100% and 28.6% for a nerve root pattern of weakness. In patients with a new postoperative deficit, 22.2% were unchanged, 44.4% improved, and 33.3% had a RTB at the 2-year follow-up.

CONCLUSIONS

Complication rates are high following posterior 3CO for cervical deformity. 3CO at C7 and T1 has the highest rates of neurological deficit. Current IONM modalities have modest performance in predicting postoperative deficits, especially for nerve root neuropraxia. A large prospective multicenter study is warranted.

Prioritization of Realignment Associated With Superior Clinical Outcomes for Cervical Deformity Patients

Objective

To prioritize the cervical parameter targets for alignment.

Methods

Included: cervical deformity (CD) patients (C2–7 Cobb angle > 10°, cervical lordosis > 10°, cervical sagittal vertical axis [cSVA] > 4 cm, or chin-brow vertical angle > 25°) with full baseline (BL) and 1-year (1Y) radiographic parameters and Neck Disability Index (NDI) scores; patients with cervical [C] or cervicothoracic [CT] Primary Driver Ames type. Patients with BL Ames classified as low CD for both parameters of cSVA (< 4 cm) and T1 slope minus cervical lordosis (TS–CL) (< 15°) were excluded. Patients assessed: meeting minimum clinically important differences (MCID) for NDI (< -15 ΔNDI). Ratios of correction were found for regional parameters categorized by primary Ames driver (C or CT). Decision tree analysis assessed cutoffs for differences associated with meeting NDI MCID at 1Y.

Results

Seventy-seven CD patients (mean age, 62.1 years; 64% female; body mass index, 28.8 kg/m²). Forty-one point six percent of patients met MCID for NDI. A backwards linear regression model including radiographic differences as predictors from BL to 1Y for meeting MCID for NDI demonstrated an R² of 0.820 (p=0.032) included TS–CL, cSVA, McGregor’s slope (MGS), C2 sacral slope, C2–T3 angle, C2–T3 SVA, cervical lordosis. By primary Ames driver, 67.5% of patients were C, and 32.5% CT. Ratios of change in predictors for MCID NDI patients for C and CT were not significant between the 2 groups (p>0.050). Decision tree analysis determined cutoffs for radiographic change, prioritizing in the following order: ≥ 42.5° C2–T3 angle, > 35.4° cervical lordosis, < -31.76° C2 slope, < -11.57-mm cSVA, < -2.16° MGS, > -30.8-mm C2–T3 SVA, and ≤ -33.6° TS–CL.

Conclusion

Certain ratios of correction of cervical parameters contribute to improving neck disability. Prioritizing these radiographic alignment parameters may help optimize patient-reported outcomes for patients undergoing CD surgery.