Anterior cervical discectomy and fusion with a zero-profile VA spacer device: a clinical and radiological study with two-year follow-up

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to compare clinical and radiological outcomes of the anterior cervical discectomy and fusion (ACDF) with a novel zero-profile variable-angle (Zero-P VA) spacer and a traditional poly-ether-ether-ketone (PEEK) cage and plate system in cases pertaining to cervical radiculopathy/myelopathy. There are two conventional types of ACDF procedures aimed at treating symptomatic cervical spondylosis. The first one involves an uninstrumented "stand-alone" approach utilizing bone graft/cage, while the second incorporates bone graft/cage in conjunction with a front plate positioned before the vertebral bodies. Both procedures have their own inherent advantages and disadvantages. The Zero-P VA spacer, however, represents a unique synthesis by amalgamating the advantages of both traditionally typical procedures. Notably, this spacer can potentially circumvent the issue related to prevertebral soft-tissue disturbance and reduce the occurrence of dysphagia.

METHODS

Using our surgical database, the authors systematically conducted a retrospective analysis encompassing all patients who underwent single-level ACDF between January 2018 and January 2019, with a minimum two-year follow-up. Patients either received a Zero-P VA implant or PEEK cage coupled with plating. The Japanese Orthopedic Association (JOA) score and Visual Analogue Scale (VAS) for arm and neck pain were documented. Dysphagia was evaluated using the Eating Assessment Tool-10 (ETA-10). Additional parameters such as cervical alignment, fusion rate and the incidence of postoperative complications were assessed.

RESULTS

According to the outcomes of the statistical analysis, there was no substantial disparity that emerged in the advancements observed in the JOA and VAS metrics between the two study cohorts. Noteworthy, however, the ETA-10 scores were statistically significantly reduced in the Zero-P VA group compared to the cage and plating group (p < 0.05). At the final follow-up, there were no statistically significant differences in the height of the operated segment, Cobb angle of the fused segment, C2-C7 Cobb angle and fusion rate between the two groups (p > 0.05). However, postoperative complications were slightly lower in patients with the Zero-P VA group (7.69%) as compared to the cage and plating group (16.67%).

CONCLUSION

The clinical outcomes observed with the Zero-P VA spacer used for single-level ACDF were found to be satisfactory. The performance of this device is comparable or even superior to the traditional cage and plating method in preventing postoperative dysphagia and mitigating potential complications associated with the use of a plate.

A Novel Intraoperative Posture-Adjustment Apparatus for Correction of Cervical Lordosis in Anterior Cervical Surgery

OBJECTIVE

Cervical alignment is a crucial factor related to the success of anterior cervical surgical procedures. In patients with severe spinal cord compression, a traditional neck pillow (TNP) may not adequately correct cervical position during surgery. Therefore, the aim of this study was to introduce this innovative intraoperative posture-adjustment apparatus (IPAA), and explored its clinical and radiological results in cervical angle correction against TNP in patients who had undergone anterior cervical surgery.

METHODS

The clinical and radiological data of 86 patients who underwent anterior cervical surgery with a minimum follow-up period of 1 year were retrospectively reviewed. Of these, 58 patients underwent IPAA, whereas 28 underwent TNP. Radiological parameters such as the degree of C2-C7 lordosis (CL), functional spinal unit angle (FSUA), C7 slope (C7S), fusion rate, and adjacent segment disease (ASD) were recorded and compared between the groups. Clinical outcomes including the Japanese Orthopaedic Association (JOA), neck disability index (NDI), visual analogue scale (VAS) for neck and arm were recorded. Complications such as kyphosis, dysphagia, Braden Scale score, revision surgery, hematoma, cerebrospinal fluid leakage, wound infection, and deep venous thrombosis were also recorded. The independent t-test or Mann-Whitney U test was used to compare continuous data, and categorical variables were assessed using the Pearson's chi-square test or Fisher's exact test.

RESULTS

Compared with the pre-operative data, the post-operative CL, FSUA, and C7S were significantly increased in both groups. CL, FSUA, and C7S in the IPAA group (14.44 ± 4.94°, 7.36 ± 2.91°, 16.54 ± 4.63°) were significantly higher than those in the TNP group (7.17 ± 8.19°, 4.99 ± 5.36°, 14.19 ± 4.48°; P < 0.05). Although there were no significant differences between the groups in terms of VAS arm and JOA scores, the post-operative and final follow-up NDI and VAS neck scores in the IPAA group were significantly lower than those in the TNP group (p < 0.05). At the last follow-up, the TNP group had significantly more kyphotic patients than the IPAA group (2 vs. 0, p = 0,041). There was no significant difference between the groups in terms of fusion rate, ASD, or complications such as dysphagia, Braden's Scale score, revision surgery, hematoma, cerebrospinal fluid leakage, wound infection, or deep venous thrombosis.

CONCLUSION

IPAA was shown to be more effective than TNP in adjusting cervical alignment (CL, FSUA, and C7S). These findings suggest that IPAA could be used as an alternative way to TNP in neck setting and cervical alignment adjustment and IPAA could potentially improve clinical outcomes after anterior cervical surgery.

MRI-based measurements of spondylolisthesis and kyphosis in degenerative cervical myelopathy

BACKGROUND

To provide normative data and to determine accuracy and reliability of preoperative measurements of spondylolisthesis and kyphosis on supine static magnetic resonance imaging (MRI) of patients with degenerative cervical myelopathy.

METHODS

T2-weighted midsagittal images of the cervical spine were in 100 cases reviewed twice by one junior observer, with an interval of 3 months, and once by a senior observer. The spondylolisthesis slip (SSlip, mm) and the modified K-line interval (mK-line INT, mm) were assessed for accuracy with the standard error of measurement (SEm) and the minimum detectable change (MDC). Intraobserver and interobserver reliability levels were determined using the intraclass correlation coefficient (ICC).

RESULTS

The SEm was 0.5 mm (95% CI 0.4-0.6) for spondylolisthesis and 0.6 mm (95% CI 0.5-0.7) for kyphosis. The MDC, i.e., the smallest difference between two examinations that can be detected with statistical certainty, was 1.5 mm (95% CI 1.2-1.8) for spondylolisthesis and 1.6 mm (95% CI 1.3-1.8) for kyphosis. The highest reliability levels were seen between the second observation of the junior examiner and the senior observer (ICC = 0.80 [95% CI 0.70-0.87] and ICC = 0.96 [95% CI 0.94-0.98] for SSlip and mK-line INT, respectively).

CONCLUSIONS

This study provides normative values of alignment measurements of spondylolisthesis and kyphosis in DCM patients. It further shows the importance of taking measurement errors into account when defining cut-off values for cervical deformity parameters and their potential clinical application in surgical decision-making.

The ratio of cervical lordosis to C7 slope represents the reciprocal change between cervical sagittal alignment and global spinal alignment

PURPOSE

This retrospective cross-sectional study investigated variations in the ratio of cervical lordosis to C7 slope (CL/C7S) at different stages of global sagittal balance to better understand how global sagittal alignment affects cervical alignment.

METHODS

A total of 255 patients with the degenerative lumbar disease were retrospectively studied within a single medical center. Whole spine radiographs were used to evaluate sagittal parameters, mainly including occiput-C2 lordosis (OC2), cervical lordosis (CL), C7 slope (C7S), the ratio of cervical lordosis to C7 slope (CL/C7S), cervical sagittal vertical axis (CSVA), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), PI minus LL mismatch (PI-LL), and sagittal vertical axis (SVA). Patients were divided into the balance group (SVA < 50 mm, PI-LL ≤ 10°), hidden imbalance group (SVA < 50 mm, PI-LL > 10°), and imbalance group (SVA > 50 mm).

RESULTS

Significant correlations were found between CL/C7S and OC2 (r = - 0.334), CSVA (r = - 0.504), PI-LL (r = 0.189), and SVA (r = 0.309). Multivariable linear regression analysis indicated that patients in the hidden imbalance group had lower CL/C7S than those in the balance group (B = - 0.234, P < 0.001), whereas the value of CL/C7S in patients with imbalanced sagittal alignment was higher than those with balanced alignment (B = 0.164, P = 0.011). The mean value of CL/C7S was 0.71, 0.51, and 0.97 in the balance, hidden imbalance, and imbalance groups, respectively. The global spine tended to tilt forward as the LL decreased, while TK, PT, PI-LL, and SVA increased (all, P < 0.001) from the balance stage to the imbalance stage.

CONCLUSIONS

CL/C7S tended to be lower when the thoracic extension increased to maintain global sagittal balance at the hidden imbalance stage. Inversely, CL/C7S increased significantly when the global spine showed severe anterior malalignment.

Changes in cervical alignment of Zero-profile device versus conventional cage-plate construct after anterior cervical discectomy and fusion: a meta-analysis

BACKGROUND

Anterior cervical diskectomy and fusion (ACDF) has been widely accepted as a gold standard for patients with cervical spondylotic myelopathy (CSM). However, there was insufficient evidence to compare the changes in the cervical alignment with different fusion devices in a long follow-up period. This meta-analysis was performed to compare the radiologic outcomes and loss of correction (LOC) in cervical alignment of Zero-profile (ZP) device versus cage-plate (CP) construct for the treatment of CSM.

METHODS

Retrospective and prospective studies directly comparing the outcomes between the ZP device and CP construct in ACDF were included. Data extraction was conducted and study quality was assessed independently. A meta-analysis was carried out by using fixed effects and random effects models to calculate the odds ratio and mean difference in the ZP group and the CP group.

RESULTS

Fourteen trials with a total of 1067 participants were identified. ZP group had a lower rate of postoperative dysphagia at the 2- or 3-month and 6-month follow-up than CP group, and ZP group was associated with a decreased ASD rate at the last follow-up when compared with the CP group. The pooled data of radiologic outcomes revealed that there was no significant difference in postoperative and last follow-up IDH. However, postoperative and last follow-up cervical Cobb angle was significantly smaller in the ZP group when compared with the CP group. In subgroup analyses, when the length of the last follow-up was less than 3 years, there was no difference between two groups. However, as the last follow-up time increased, cervical Cobb angle was significantly lower in the ZP group when compared with the CP group.

CONCLUSION

Based on the results of our analysis, the application of ZP device in ACDF had a lower rate of postoperative dysphagia and ASD than CP construct. Both devices were safe in anterior cervical surgeries, and they had similar efficacy in correcting radiologic outcomes. However, as the last follow-up time increased, ZP group showed greater changes cervical alignment. In order to clarify the specific significance of LOC, additional large clinical studies with longer follow-up period are required.

Preoperative Cervical Cobb Angle Is a Risk Factor for Postoperative Axial Neck Pain after Anterior Cervical Discectomy and Fusion with Zero-Profile Interbody

OBJECTIVES

Anterior cervical discectomy and fusion (ACDF) with zero-profile interbody has a lower incidence of complications in treating cervical spondylotic myelopathy (CSM). However, postoperative axial neck pain is still commonly occurred, and the factors affecting which is not known. Here, we retrospectively analyze the risk factors for postoperative axial pain after performing ACDF with zero-profile implant in single-level CSM.

METHODS

Patients who suffered from single-level CSM and who received ACDF with zero-profile implant between 2018 January to 2020 December were reviewed. Of 180 single-level CSM patients, 144 patients who passed the inclusion criteria were enrolled. Patients were divided into two groups according to the severity of postoperative axial pain as measured by postoperative neck visual analogue scale (nVAS). Clinical parameters including age, sex, smoking history, symptom duration, body mass index (BMI), the Japanese Orthopaedic Association (JOA) scores, as well as radiological parameters were obtained pre- and post-operatively, and the data were compared between two groups. Pearson's chi-square tests and Mann-Whitney U tests were implemented to identify statistically significant differences between subgroups for categorical and continuous data, respectively; otherwise, the data were tested with Student's t-test. Risk factors were identified using logistic regression.

RESULTS

Of the patients (97.8%) achieved satisfied neurological recovery, and 88.2% of the patients achieved fusion at 1-year follow-up. 33% of the patients (48 patients out of 144) had sustained postoperative axial pain after the surgery. Comparison of different severity groups exhibited no significant differences in terms of the possible risk factors (P > 0.05) except for pre- and post-operative C2-C7 Cobb angles (6.33 ± 6.53 vs. 11.88 ± 7.41, P < 0.05; 13.49 ± 5.31 vs 16.64 ± 7.34, P < 0.05). Furthermore, correlation analysis showed that the preoperative C2-C7 Cobb angle is significantly correlated with the severity of the postoperative axial pain (R²  = 0.83, P < 0.01). In addition, logistic regression analysis demonstrated that the preoperative C2-C7 Cobb angle is an independent predictor of postoperative axial pain (P < 0.01, OR = 0.53). Further receiver operating characteristic (ROC) analysis displayed an area under the curve (AUC) of 0.78 (P < 0.01) for preoperative C2-C7 Cobb angle, and the optimal cutoff was 8.4° (sensitivity 0.77, specificity 0.65).

CONCLUSION

The pre-operative C2-C7 Cobb angle is a risk factor for severe postoperative axial pain after anterior cervical discectomy and fusion with zero-profile interbody, and we should be cautious when poor preoperative C2-C7 Cobb angle is found in myelopathy patients planning to use zero-profile interbody to treat such patients.

Cervical Alignment Analysis Comparing Two-Level Cervical Disc Arthroplasty with Anterior Cervical Discectomy and Fusion with Anterior Plate Fixation

OBJECTIVE

This study assesses cervical alignments after 2-level cervical disc arthroplasty (CDA) versus anterior cervical discectomy and fusion (ACDF) with anterior plate fixation.

METHODS

Eighty-two patients who underwent 2-level CDA or ACDF in 2014-2019 were identified. Cervical alignment parameters were compared between the 2 cohorts. Subgroup analyses were performed to determine factors that differentiate alignment outcomes between the 2 procedures.

RESULTS

Although both cohorts achieved significant focal lordosis (FL) and overall cervical lordotic (CL) gains, CDA cohorts achieved significantly greater 12-month FL gain (P = 0.022). However, in a multivariate analysis controlling for preoperative variables, FL gain was no longer significant. Although the CDA cervical sagittal vertical axis (cSVA) significantly improved at 3 (P = 0.030) and 12 (P = 0.007) months, these improvements were not superior to the ACDF cSVA. Male patients undergoing CDA achieved greater 12-month CL gain. Patients undergoing CDA with body mass index >25 kg/m² achieved greater 12-month FL gain. Patients undergoing CDA with symptom duration >12 months achieved greater FL gain at 3 and 12 months. Patients undergoing CDA with high baseline T1 slope or cSVA achieved greater 12-month cSVA reduction. Clinical outcomes were comparable between the 2 cohorts. Unlike the ACDF group, CL gain in the CDA group was significantly correlated with the cSVA reduction, which was associated with significant improvement in the Neck Disability Index, arm pain, and 12-Item Short-Form Mental Component Scores. Heterotopic ossification was not found to significantly affect patient outcome and cervical alignment in both cohorts.

CONCLUSIONS

ACDF and CDA are viable options for 2-level degenerative disc disease in carefully selected patients. Both approaches produced equivalent postoperative alignment changes in a 2-level operation.

Short-term effects of instrument-assisted soft tissue mobilization compared to algometry pressure release in tension-type headache: a randomized placebo-controlled trial

PURPOSES

To compare the effectiveness of instrument-assisted soft tissue mobilization (IASTM) and pressure algometry with sham ultrasound (control group) on the clinical measures of headache, pressure pain threshold (PPT) of upper trapezius and suboccipital muscles and cervical alignment in patients with tension type headache (TTH).

METHODS

Seventy-two patients with TTH of both genders were randomly allocated to 3 experimental groups: a) the IASTM group (n=24), b) pressure algometry group (n=24), and c) sham ultrasound control group (n=24). Headache frequency and disability, pressure pain threshold of upper trapezius and suboccipital muscles, cervical lordosis angle (CA) and anterior head translation (AHT) were measured four weeks before and after intervention. Moreover, headache frequency was followed up for two more weeks after intervention.

RESULTS

Statistically significant improvements (P <0.05; effect size ranges 1.1-1.9) were observed in all outcome measures following IASTM compared to the other two intervention methods. In the IASTM group, the headache frequency decreased from 15 to 2 days/month. Also, headache disability decreased from 19 to 10. Further, CA increased from 17.5° to 31.4° and AHT decreased from 24.1 to 15.5 mm. The pressure algometry group showed significantly lower headache frequency at the follow-up (P < 0.01) than the sham ultrasound control group. However, Similar findings in the other evaluated outcomes were found between the pressure algometry and sham ultrasound control groups (P ˃ 0.05).

CONCLUSION

The results of the present study indicate the effectiveness of IASTM in improving headache symptoms and cervical alignment in patients with TTH.

Predictive value of sagittal craniocervical roentgenographic parameters for HRQOL after craniocervical fusion

PURPOSE

Loss of "physiological" sagittal alignment following craniocervical fusion (CCF) for degenerative disease may be associated with loss of horizontal gaze, dysphagia and poor HRQOL. This study reports on sagittal craniocervical roentgenographic predictors of HRQOL (SF-36) in patients following uncomplicated CCF for fresh upper cervical traumatic (UCT) injuries.

METHODS

Twenty-two consecutive adult patients (group P) aged 50 ± 16 years, who had undergone CCF for fresh unstable C₁ and C₂AO/type UCT injuries, were evaluated 39 ± 12 months postoperatively with upright lateral cervical roentgenograms and SF-36as HRQOL measure. Physiological data for cervical sagittal alignment and SF-36 were taken from an age-matched control group (C) of 30 individuals aged 52 ± 12 years. Several commonly used sagittal cervical roentgenographic parameters were tested as potential predictors of the SF-36 domains in both groups. Roentgenographic predictors for each of the nine SF-domains were calculated using stepwise multilinear regression analysis (MLRA).

RESULTS

The roentgenographic predictors in patients included (1) the angle created by McGregor's line and the inferior surface of the axis (OC₂a) for physical function (PF, P = 0.049), role limitations due to physical health (RLPH, P = 0.004),role limitation due to emotional problems (RLEP, P = 0.004), emotional functioning (EF) (P = 0.012), social functioning (SF) (P = 0.028) and general health (GH, P = 0.041). (2) The angle formed between a horizontal line and the superior endplate of T₁-vertebra (T₁-slope) was predictor for SF (P = 0.017) and pain (P = 0.021), and (3) the angle between McGregor's line and the line that links the center of the C₁ anterior arch and the apex of cervical sagittal curvature (PIA) was predictor for health change (HC, P = 0.002).

CONCLUSIONS

This study showed that postoperative OC₂a, PIA and T1-slope safely predict HRQOL outcomes (SF-36) following CCF for fresh trauma. It seems theoretically that the adequate restoration of the upper cervical alignment including C1-C2 upper cervical lordosis (OC₂a) and PIA, in interaction with T1-slope, is important for postoperative HRQOL scores close to physiological values. The authors speculate that C0-C4 fusion restores horizontal gaze and allows for painful regain of pre-trauma quality of life. Spine surgeons should realign and stabilize the craniocervical junction taking in consideration these roentgenographic predictors.

Spino cranial angle as a predictor of loss of cervical lordosis after laminoplasty in patients with cervical myelopathy

Background

To explore the relationship between spino cranial angle (SCA) and loss of cervical lordosis (LOCL), and to determine whether SCA has the ability to predict LOCL for patients with cervical myelopathy.

Methods

A total of 68 consecutive patients with cervical myelopathy who received laminoplasty (LAMP) were selected to the current study. C2–C7 lordosis was defined as a representation of the cervical alignment. Alignment change > 0° was considered LOCL. Multiple linear regression analysis was applied to evaluate the association between LOCL and various sagittal parameters at preoperative, such as SCA, CL, T1s and cSVA. Linear regression analysis was applied to evaluate the relationships between LOCL and preoperative SCA in each subgroup.

Results

Patients were assigned to three groups depending on the quartile of preoperative SCA. The first quarter of patients were defined as the low SCA group, the last quarter were defined as the high SCA group and the middle half were defined as the middle SCA group. There was no statistically significant difference in age, sex and the type of OPLL among the three groups. Patients in the low SCA group showed more cervical lordosis before surgery and more LOCL after LAMP (p < 0.001). After linear regression analysis for SCA and LOCL, preoperative SCA was negatively correlated with LOCL in the low SCA group (r = − 0.857, p < 0.001) and high SCA group (r = − 0.515, p = 0.034). However, there was no significant correlation between preoperative SCA and LOCL in the middle SCA group (r = 0.027, p = 0.881).

Conclusions

Patients with lower SCA had more lordosis preoperatively and performed more LOCL after LAMP at 2 years of follow-up. Both too high or low preoperative SCA were negatively correlated with the degree of LOCL, while when the SCA fluctuates in a suitable range, it is easier to compensate for the changes of cervical sagittal alignment.

Association of Spinal Alignment Correction With Patient-Reported Outcomes in Adult Cervical Deformity: Review of the Literature

Objective

Adult cervical deformity (ACD) is a debilitating spinal condition that causes significant pain, neurologic dysfunction, and functional impairment. Surgery is often performed to correct cervical alignment, but the optimal amount of correction required to improve patient-reported outcomes (PROs) are not yet well-defined.

Methods

A review of the literature was performed and Fisher's z-transformation (Zr) was used to pool the correlation coefficients between alignment parameters and PROs. The strength of correlation was defined according to the following: poor (0 < r ≤ 0.3), fair (0.3 < r ≤ 0.5), moderate (0.5 < r ≤ 0.8), and strong (0.8 < r ≤ 1).

Results

Increased C2-C7 SVA was fairly associated with increased Neck Disability Index (NDI) (pooled Zr = 0.31; 95% CI, -0.03, 0.58). Changes in TS-CL poorly correlated with NDI (pooled Zr = -0.04; 95% CI, -0.23-0.30). Increased C7-S1 was poorly associated with worse EQ-5D (pooled Zr = -0.22; 95% CI, -0.36, -0.06). Correction of horizontal gaze (CBVA) did not correlate with legacy metrics. mJOA correlated with C2-slope, C7-S1, and C2-S1.

Conclusion

Spinal alignment parameters variably correlated with improved HRQoL and myelopathy after corrective surgery for ACD. Further studies evaluating legacy PROs, PROMIS, and ACD specific instruments are needed for further validation.

Alignment, Classification, Clinical Evaluation, and Surgical Treatment for Adult Cervical Deformity: A Complete Guide

Adult cervical deformity management is complex and is a growing field with many recent advancements. The cervical spine functions to maintain the position of the head and plays a pivotal role in influencing subjacent global spinal alignment and pelvic tilt as compensatory changes occur to maintain horizontal gaze. There are various types of cervical deformity and a variety of surgical options available. The major advancements in the management of cervical deformity have only been around for a few years and continue to evolve. Therefore, the goal of this article is to provide a comprehensive review of cervical alignment parameters, deformity classification, clinical evaluation, and surgical treatment of adult cervical deformity. The information presented here may be used as a guide for proper preoperative evaluation and surgical treatment in the adult cervical deformity patient.

Occipital bone erosion induced by C1 pedicle screw as a late complication of atlantoaxial fixation: a case report and literature review

PURPOSE

The objective of this case report is to highlight occipital bone erosion as an unusual late complication of C1-C2 instrumented fixation.

CASE PRESENTATION

A 60-year-old man of a displaced Anderson type II odontoid fracture was surgically treated by C1-C2 pedicle screw fixation. Occipital bone erosions, caused by a repeat irritation of the end of rod to the occipital bone, were detected on multiplane reconstructed computed tomography at 3 months after surgery. The lesion progressed over time with increasing the C2 anteversion on radiological evaluations. Eventually, the bony shell had been reactively formed around the protruded screw-rod construct and the Oc-C1 segment had been spontaneously stabilized. Fortunately, he had experienced no symptoms caused by the lesion at 5-year follow-up.

CONCLUSION

The occipital bone erosion is an unusual late complication in C1-C2 posterior fixation using C1 pedicle screw. The increasing occipital-C1 lordosis compensating for the great C2 anteversion (high C2 slope) was related to the progression of the lesion. In C1-C2 pedicle screw fixation, surgeons should recognize a possibility of this complication and realize a relation between the occurrence of the lesion and the sagittal alignment of the cervical spine to take measures to avoid the complication.

Correction of the spine with magnetically controlled growing rods in early onset scoliosis : A pre-to-post analysis of 21 patients with 1‑year follow-up

BACKGROUND

Several studies have emphasized that the magnetically controlled growing rod (MCGR) technique decreases complications and costs and could be considered a safe procedure for treating patients with early onset scoliosis (EOS). To the best of our knowledge, the sagittal profile of patients with an implanted MCGR has not been sufficiently studied before.

OBJECTIVE

The objectives of this study were twofold: firstly, to evaluate the influence of MCGR on the coronal, sagittal and axial planes. Secondly, to analyze changes of cervical alignment post-MCGR implantation.

MATERIAL AND METHODS

This was a retrospective study of patients with EOS who underwent MCGR from 2012 to 2018. Patients were included if they presented with a thoracic or lumbar curvature greater than 40° (Cobb angle) and Risser's sign 0. Global analysis of all patients was reported. Patients were stratified preoperatively by thoracic alignment into a hypokyphotic or kyphotic group. Furthermore, the study population was divided into an anteriorly aligned group and a posteriorly aligned group. Sagittal alignment parameters and parameters of coronal and axial plane were measured and the preoperative to postoperative change was compared then analyzed 1 year after surgery. No external funding was procured for this research and the authors' conflicts of interest are not pertinent to the present work.

RESULTS

A total of 21 patients were included in the study. There was a significant coronal correction of the structural and compensatory curves (p < 0.01). Before and after surgery, the coronal C7 plumbline was unchanged and remained within the normal range. Postoperatively, a significant derotation of the apical vertebra in thoracic and lumbar curves was observed (p < 0.05). Global analysis of the sagittal profile revealed a significant decrease of TK (p < 0.001) and T9SPi (p = 0.002) with a simultaneous significant increase of T1T3 angle (p = 0.015) and T1T4 angle (p = 0.015). No significant changes of the sagittal parameters of cervical, lumbar and spinopelvic parameters were noted. Among all groups, cervical parameters did not reveal any statistically significant changes. At 1‑year follow up the T1T3 angle (p = 0.01) and T1T4 angle (p = 0.03) were significantly increased. All other measured parameters of sagittal, coronal and axial profile were unchanged.

CONCLUSION

The implantation of MCGR had a significant impact on the sagittal profile. Notwithstanding, no further compensatory mechanisms of the cervical spine and pelvis had to be recruited to safeguard sagittal alignment.

Cervical Sagittal Alignment: Literature Review and Future Directions

Cervical alignment as a concept has come to the forefront for spine deformity research in the last decade. Studies on cervical sagittal alignment started from normative data, and expanded into correlation with global sagittal balance, prognosis of various conditions, outcomes of surgery, definition and classification of cervical deformity, and prediction of targets for ideal cervical reconstruction. Despite the recent robust research efforts, the definition of normal cervical sagittal alignment and cervical spine deformity continues to elude us. Further, many studies continue to view cervical alignment as a continuation of thoracolumbar deformity and do not take into account biomechanical features unique to the cervical spine that may influence cervical alignment, such as the importance of musculature connecting cranium-cervical-thoracic spine and upper extremities. In this article, we aim to summarize the relevant literature on cervical sagittal alignment, discuss key results, and list potential future direction for research using the '5W1H' framework; "WHO" are related?, "WHY" important?, "WHAT" to evaluate and "WHAT" is normal?, "HOW" to evaluate?, "WHEN" to apply sagittal balance?, and "WHERE" to go in the future?

Impact of Nonlordotic Sagittal Alignment on Short-term Outcomes of Cervical Disc Replacement

Objective

To evaluate outcomes of cervical disc replacement (CDR) in patients with nonlordotic alignment.

Methods

Patients who underwent CDR were retrospectively reviewed and divided into 3 cohorts: (1) neutral/lordotic segmental and C2–7 Cobb angle (L), (2) nonlordotic segmental Cobb angle, lordotic C2–7 Cobb angle (NL-S), and (3) nonlordotic segmental and C2–7 Cobb angle (NL-SC). Radiographic and patient-reported outcomes (PROMs) were compared.

Results

One-hundred five patients were included (L: 37, NL-S: 30, NL-SC: 38). A significant gain in segmental lordosis was seen in all cohorts at < 6 months (L: -1.90° [p = 0.007]; NL-S: -5.16° [p < 0.0001]; NL-SC: -6.00° [p < 0.0001]) and ≥ 6 months (L: -2.07° [p = 0.031; NL-S: -6.04° [p < 0.0001]; NL-SC: -6.74° [p < 0.0001]), with greater lordosis generated in preoperatively nonlordotic cohorts (p < 0.0001). C2–7 lordosis improved in the preoperatively nonlordotic cohort (NL-SC: 8.04°) at follow-up of < 6 months (-4.15°, p=0.003) and ≥ 6 months (-6.40°, p=0.003), but not enough to create lordotic alignment (< 6 months: 3.89°; ≥ 6 months: 4.06°). All cohorts showed improvement in Neck Disability Index, visual analogue scale (VAS) neck, and VAS arm, without significant difference among groups in the amount of improvement (≥ 6-month PROMs follow-up=69%).

Conclusion

In patients without major kyphotic deformity, CDR has the potential to generate and maintain lordosis and improve PROMs in the short-term, and can be an effective treatment option for patients with nonlordotic alignment.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

LEVEL OF EVIDENCE

IV.

Cervical sagittal alignment in adolescent high dysplastic developmental spondylolisthesis: how does the cervical spine respond to the reduction of spondylolisthesis?

Background

Although pelvic and related parameters have been well stated in lumbar developmental spondylolisthesis, cervical sagittal alignment in these patients is poorly studied, especially in high dysplastic developmental spondylolisthesis (HDDS). The purpose of this study is to investigate the sagittal alignment of the cervical spine in HDDS and how the cervical spine responds to reduction of spondylolisthesis.

Methods

Thirty-three adolescent patients with lumbar developmental spondylolisthesis who received preoperative and postoperative whole-spine x-rays were reviewed. They were divided into the HDDS group (n = 24, 13.0 ± 2.2 years old) and the low dysplastic developmental spondylolisthesis (LDDS) group (n = 9, 15.6 ± 1.9 years old). Spinal and pelvic sagittal parameters, including cervical lordosis (CL), were measured and compared between groups. In the HDDS group, the postoperative parameters were measured and compared with those before surgery.

Results

HDDS group had a higher proportion of cervical kyphosis (70.8% vs. 22.2%, P = 0.019), and there was a significant difference in CL between the two groups (− 8.5° ± 16.1° vs. 10.5° ± 11.8°, P = 0.003). CL was correlated with the Dubousset’s lumbosacral angle (Dub-LSA), pelvic tilt (PT), and thoracic kyphosis (TK). In the HDDS group, CL in patients with a kyphotic cervical spine was significantly improved after reduction of spondylolisthesis (− 16.4° ± 5.9° vs. − 3.6° ± 9.9°, P < 0.001). In the HDDS group, 46% (6/13) of the patients with postoperative Dub-LSA < 90° still had sagittal imbalance (sagittal vertical axis, [SVA] > 5 cm), while no sagittal imbalance was observed in patients with postoperative Dub-LSA > 90° (46% [6/13] vs. 0% [0/11], P = 0.016).

Conclusions

HDDS can lead to cervical kyphosis through a series of compensatory mechanisms. Reduction of spondylolisthesis and correction of lumbosacral kyphosis may correct the cervical kyphosis and normalize the overall spinal sagittal profile. Correction of Dub-LSA to above 90° might be used as an objective to better improve the sagittal alignment of the spine.

Cranial Kyphotic Change After Multilevel Anterior Cervical Corpectomy and Fusion May Lead to Myelopathy Recurrence

OBJECTIVE

To determine the characteristic alignment change in patients with myelopathy recurrence after multilevel anterior cervical corpectomy and fusion (m-ACCF).

METHODS

We analyzed 52 patients who underwent m-ACCF, including 20 who underwent revision surgeries for myelopathy recurrence (R group) and 32 postoperative asymptomatic patients (A group). Classic alignment parameters (cervical lordosis angle, cervical sagittal vertical axis, and fusion area angle and length) and original alignment parameters (α-β, β-bone graft [BG], BG-γ, and γ-δ angles) were measured preoperatively, postoperatively, and at follow-up or before revision surgery. The difference in the amount of change in parameters between groups was analyzed. The relationship between distribution of restenotic lesions and characteristic alignment change in the R group was evaluated.

RESULTS

Cervical lordosis angle, fusion area angle, and fusion area length in the R group significantly decreased postoperatively compared with the A group (P < 0.01, P < 0.01, and P = 0.04). Compared with the A group, α-β and β-BG angles in the R group significantly decreased (P < 0.01), indicating kyphotic change on the cranial side. BG-γ and γ-δ angles in the R group significantly increased (P < 0.01), indicating lordotic change in the caudal fused area. Restenotic lesions significantly increased on the cranial side in the R group (cranial side, 19 levels; caudal side, 5 levels; P < 0.01).

CONCLUSIONS

In patients with myelopathy recurrence after m-ACCF, the cranial side has significant kyphosis and the caudal side has lordosis. Moreover, 79.2% of the restenotic lesions were significantly maldistributed on the cranial side. Surgeons should pay close attention to cranial kyphosis inducing myelopathy recurrence after m-ACCF.

Exploration on sagittal alignment and clinical outcomes after consecutive three-level hybrid surgery and anterior cervical discectomy and fusion: a minimum of a 5-year follow-up

Purpose

To compare sagittal alignment and clinical outcomes between three-level hybrid surgery (HS) and anterior cervical discectomy and fusion (ACDF) on cervical spondylotic myelopathy (CSM) over a 5-year follow-up.

Method

The study included 32 patients with ACDF, 36 patients with 1 prosthesis and 2 cages (HS1 group), and 25 cases with 2 prostheses and 1 cage (HS2 group). Alignment parameters included C2–C7 cervical lordosis (CL), C2–C7 sagittal vertical axis (SVA), T1 slope (T1S), and T1S minus CL (T1SCL). Radiographic parameters were range of motion (ROM), upper and lower adjacent ROM (UROM and LROM), and operated-segment lordosis (OPCL), as well as adjacent segment degeneration (ASD). Clinical outcomes included the neck disability index (NDI) and Japanese Orthopedic Association (JOA) score.

Results

Three groups were well-matched in demographics. All groups gained comparable improvement on NDI and JOA (P < 0.01). All groups gained CL improvement at the final visit (P < 0.05). There were no statistical differences on SVA and T1SCL among the groups and among preoperation, 1 week later, and final follow-up (P > 0.05) while T1S improved at 1 week later and final follow-up with HS2. The final change of all alignment parameters among the three groups was of no differences. ROM decreased and OPCL increased in all groups at the final follow-up (P < 0.05). UROM and LROM increased with ACDF but kept stable with HS1 and HS2. There was no inter-group difference on the incidence of ASD (P > 0.05).

Conclusion

Cervical alignment was comparably improved. HS and ACDF provided identified mid-term efficacy, and it was not necessary to have to use prosthesis on three-level CSM.

Can knee flexion contracture affect cervical alignment and neck tension? A prospective self-controlled pilot study

BACKGROUND CONTEXT

The coordination of the alignment between the lower extremities and cervical spine helps to achieve balance and horizontal gaze during standing and walking. Malalignment in any segment can disturb the global balance, causing compensation in another segment. Knee flexion contracture (KFC) can cause spine inclination with increased C7 tilt or C7 SVA (sagittal vertical axis). Cervical alignment and the posterior muscles are essential for maintaining the horizontal gaze which is closely related to neck tension (NT).

PURPOSE

This study aimed to determine whether KFC can affect cervical alignment and its potential effects on the posterior muscles and NT.

DESIGN

A prospective pilot study was carried out in preoperative (pre-op) and postoperative (post-op) phases.

PATIENT SAMPLE

This study included 22 consecutive patients with KFC and 12 control subjects in our department who agreed to participate from between August 1, 2018 and February 28, 2019 in our department.

OUTCOME MEASURES

Visual analog scale (VAS) and neck disability index (NDI) were used. The sagittal alignment parameters and cervical range of motion (ROM) were measured on radiographic images, and included the C0-C2 lordosis (C0-2L), C2-C7 lordosis (C2-7L), C2 SVA, C7 SVA, T1 slope, thoracic kyphosis, lumbar lordosis (LL), pelvic tilt, sacral slope, and knee flexion angle (KA). Surface electromyography-based flexion-relaxation ratio (FRR) and ultrasound-based shear wave elastography (SWE) were performed.

METHODS

The control group was matched for age, sex, and body mass index with the KFC group. Patients in the KFC group underwent arthroscopic surgery to correct knee alignment. Comparisons between pre-op and post-op phases were performed using paired sample t tests, comparisons between KFC and control groups were performed using independent samples t tests. The correlation analysis between the parameters was performed using Spearman analysis. Funding for this study was provided by the National Natural Science Foundation of China (60,000 USD), Beijing Municipal Administration of Hospitals Incubating Program (50,000 USD), and Beijing Municipal Administration of Hospitals Clinical Medicine Development of Special Funding Support (20,000 USD). There were no conflicts of interest associated with this study.

RESULTS

The average follow-up time for this pilot study was 11.4±1.5 days. Pre-op, the KFC group had higher KA, T1S, C7 SVA, C2 SVA, C0-2L, SWE, VAS, and NDI compared with the control group, but all of these parameters were decreased significantly post-op. The LL, FRR of splenius capitis (FRRsc), and ROM of the KFC group pre-op were lower than the control group, and all of these were increased significantly post-op. There were no differences in pelvic tilt, sacral slope, C2-7 L, or TK between the KFC and control groups, or in FRR of splenius capitis (FRRutr) between pre-op and post-op phases. KA had strong correlations with LL (r=-0.83), which correlated well with C7 SVA (r=-0.75). C7 SVA correlated strongly with C2 SVA (r=0.79), which also correlated strongly with C0-2 L (r=0.76). C0-2 L correlated well with FRRsc (r=-0.65) and SWEsc (r=0.72), and both of them correlated well with VAS (r=-0.54, r=0.71) and NDI (r=-0.57, r=0.76). ROM correlated well with FRRsc (r=0.71), SWEsc (r=-0.74), VAS (r=-0.66), and NDI (r=-0.66).

CONCLUSIONS

KFC may cause spine inclination and craniocervical malalignment, leading to NT and ROM reduction. The results of this pilot study may be helpful in guiding further studies concerning KFC and NT.

The Correlation Between Postoperative Cervical Sagittal Alignment and Spine Sagittal Alignment in Adolescent Idiopathic Scoliosis: A Meta-Analysis

OBJECTIVE

To perform a meta-analysis exploring the correlation between cervical lordosis (CL) and sagittal spine alignment in patients with adolescent idiopathic scoliosis (AIS) after surgery for determining a surgical strategy.

METHODS

We searched 3 electronic databases for studies discussing the correlation between CL and spine sagittal alignment in patients with AIS. Studies reported from the inception of the database to June 2019 were retrieved without any language restrictions. Summary correlation coefficient (r) values were extracted from each study, and 95% confidence intervals (CIs) were calculated. In addition, we conducted subgroup analyses in different curve type subgroups with at least 2 studies.

RESULTS

Ten relevant studies involving 539 patients were evaluated in this meta-analysis. The Pearson correlation (r) for CL and the T1 slope was -0.69; (95% CI, -0.79 to -0.54). The fixed-effects summary correlation between CL and thoracic kyphosis in patients was moderate (r = -0.40; 95% CI, -0.48 to -0.31). In addition, the fixed-effects summary correlations between CL and lumbar lordosis (r = 0.19; 95% CI, 0.07-0.30), pelvic incidence (r = -0.08; 95% CI, -0.20 to 0.04), pelvic tilt (r = -0.06; 95% CI, -0.18 to 0.06), and sacral slope (r = -0.06; 95% CI, -0.18 to 0.06) in patients were weak.

CONCLUSIONS

There is a strong negative correlation between CL and the T1 slope in patients with AIS. Given the lack of robust clinical evidence, these findings warrant verification by large prospective registries and randomized trials with long follow-up periods.

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

Background

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

Methods

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

Results

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

Conclusions

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

Predictive model for distal junctional kyphosis after cervical deformity surgery

BACKGROUND CONTEXT

Distal junctional kyphosis (DJK) is a primary concern of surgeons correcting cervical deformity. Identifying patients and procedures at higher risk of developing this condition is paramount in improving patient selection and care.

PURPOSE

The present study aimed to develop a risk index for DJK development in the first year after surgery.

STUDY DESIGN/SETTING

This is a retrospective review of a prospective multicenter cervical deformity database.

PATIENT SAMPLE

Patients over the age of 18 meeting one of the following deformities were included in the study: cervical kyphosis (C2-7 Cobb angle>10°), cervical scoliosis (coronal Cobb angle>10°), positive cervical sagittal imbalance (C2-C7 sagittal vertical axis (SVA)>4 cm or T1-C6>10°), or horizontal gaze impairment (chin-brow vertical angle>25°).

OUTCOME MEASURES

Development of DJK at any time before 1 year.

METHODS

Distal junctional kyphosis was defined by both clinical diagnosis (by enrolling surgeon) and post hoc identification of development of an angle<-10° from the end of fusion construct to the second distal vertebra, as well as a change in this angle by <-10° from baseline. Conditional Inference Decision Trees were used to identify factors predictive of DJK incidence and the cut-off points at which they have an effect. A conditional Variable-Importance table was constructed based on a non-replacement sampling set of 2,000 Conditional Inference Trees. Twelve influencing factors were found; binary logistic regression for each variable at significant cutoffs indicated their effect size.

RESULTS

Statistical analysis included 101 surgical patients (average age: 60.1 years, 58.3% female, body mass index: 30.2) undergoing long cervical deformity correction (mean levels fused: 7.1, osteotomy used: 49.5%, approach: 46.5% posterior, 17.8% anterior, 35.7% combined). In 2 years after surgery, 6% of patients were diagnosed with clinical DJK; however, 23.8% of patients met radiographic definition for DJK. Patients with neurologic symptoms were at risk of DJK (odds ratio [OR]: 3.71, confidence interval [CI]: 0.11-0.63). However, no significant relationship was found between osteoporosis, age, and ambulatory status with DJK incidence. Baseline radiographic malalignments were the most numerous and strong predictors for DJK: (1) C2-T1 tilt>5.33 (OR: 6.94, CI: 2.99-16.14); (2) kyphosis<-50.6° (OR: 5.89, CI: 0.07-0.43); (3) C2-C7 lordosis<-12° (OR: 5.7, CI: 0.08-0.41); (4) T1 slope minus cervical lordosis>36.4 (OR: 5.6, CI: 2.28-13.57); (5) C2-C7 SVA>56.3° (OR: 5.4, CI: 2.20-13.23); and (6) C4_Tilt>56.7 (OR: 5.0, CI: 1.90-13.1). Clinically, combined approaches (OR: 2.67, CI: 1.21-5.89) and usage of Smith-Petersen osteotomy (OR: 2.55, CI: 1.02-6.34) were the most important predictors of DJK.

CONCLUSIONS

In a surgical cohort of patients with cervical deformity, we found a 23.8% incidence of DJK. Different procedures and patient malalignment predicted incidence of DJK up to 1 year. Preoperative T1 slope-cervical lordosis, cervical kyphosis, SVA, and cervical lordosis all strongly predicted DJK at specific cut-off points. Knowledge of these factors will potentially help direct future study and strategy aimed at minimizing this potentially dramatic occurrence.

Upper cervical lordosis compensates lower cervical kyphosis to maintain whole cervical lordosis after selective laminectomy

After lower-cervical-level spinal-cord tumor resection, compensatory upper cervical lordosis with lower cervical kyphosis was observed. However, no studies examined this compensation following posterior decompression surgery for cervical compressive myelopathy (CCM). The purpose of this study was to evaluate the compensatory mechanism after muscle-preserving selective laminectomy (SL) and to assess the clinical outcomes following such compensation. Enrolled in the study were 125 CCM patients who underwent C6 single-level SL, C5-C6 two-level SL, C4-C6 three-level SL, and C3-C6 four-level SL. Cervical spine lateral radiography was taken before surgery and during the final followup. The C2-C5, C5-C7, and C2-C7 angles were measured and presented respectively as the patients' "upper," "lower," and "whole" cervical alignments. Patients were divided into two groups according to their postoperative C5-C7 alignment changes. We then divided the C5-C7 kyphotic-change group according to the patients' postoperative C7 slope changes. Postoperative cervical sagittal balance and surgical outcomes were compared within the groups. Postoperative C5-C7 kyphotic change was compensated for by C2-C5 lordotic change, maintaining the preoperative C2-C7 angle. Although postoperative C5-C7 kyphotic change alone did not affect cervical sagittal balance or surgical outcomes, patients with C5-C7 kyphotic changes and C7 slope increases showed greater increases in the C2-C7 sagittal vertical axis and lower recovery rates in Japanese Orthopaedic Association scores. The patients' postoperative lower cervical kyphotic changes were compensated for by upper cervical lordotic changes. Despite this compensation, increases in patients' C7 slopes adversely affected sagittal balance and functional recovery.

Measurement of Cervical Sagittal Alignment Parameters on X-Ray Films of Adults without Severe Spinal Deformity Whose Shoulder Hides the Lower Cervical Column

OBJECTIVE

The Cobb angle between the lower endplate of C2 and C7 (C2L-C7L angle) is a traditional parameter used for the assessment of the cervical alignment. However, when the lower cervical column is masked by the shoulder, measurements are difficult. In the present study, we inspected 191 X-ray films, measured the Cobb angle between C2L and the endplates at the several levels of the lower cervical column, and assessed their usefulness of such measurements for the determination of cervical sagittal alignment.

METHODS

We obtained X-ray films on 191 patients ranging in age from 20 to 93 years. The Cobb angle between C2L and the C7 upper (C7U), the C6 lower (C6L), the C6 upper (C6U), and the C5 lower endplate (C5L) was measured and compared with the C2L-C7L angle.

RESULTS

C7L was identified in 116 of 191 patients (60.7%). Except for C2L-C7U angle (P = 0.55), the difference in the mean between C2L-C7L angle and the angle between C2L and the other endplates was statistically significant (P < 0.05). There was a very strong correlation between C2L-C7L angle and C2L-C7U angle (r = 0.99), C2L-C6L angle (r = 0.96), C2L-C6U angle (r = 0.94), and C2L-C5L angle (r = 0.86).

CONCLUSIONS

To measure the C2L-C7L angle on unclear X-ray films, C7U can be substituted for C7L. Our measurement data for the C6 and C5 endplates were statistically different; however, the correlation between the C2L-C7L angle and C2L-C6U angle, C2L-C6L angle or C2L-C5L angle was very strong. In patients with unclear lower vertebral bodies, cervical sagittal alignment can be predicted by using adjacent endplates.

Sagittal Profile Response of Cervical Spine After Posterior Correction in Thoracic and Lumbar Adolescent Idiopathic Scoliosis: Correlation with Thoracic Kyphosis?

OBJECTIVE

To analyze postoperative changes in cervical alignment in patients with adolescent idiopathic scoliosis (AIS) with different curve patterns.

METHODS

Radiographic data were retrospectively reviewed in 43 patients with AIS with right thoracic major curve versus 39 with major lumbar curve with a minimum of 2 years' follow-up. Radiographic parameters analyzed in this study included cervical sagittal parameters (cervical lordosis [CL], T1 slope, T1 slope minus C2-C7 lordosis, T1-spine, T1 pelvic angle, and C2-C7 sagittal vertical axis) and spinopelvic sagittal parameters obtained from radiographs. Paired t tests were used for comparison with 0.05 as a statistically significant threshold.

RESULTS

At baseline, larger CL (5.69° vs. -5.12°, P = 0.002) and smaller T1 slope minus C2-C7 lordosis (9.26° vs. 17.09°, P = 0.001) was noted in patients with lumbar-curve adolescent idiopathic scoliosis (L-AIS), whereas preoperative thoracic kyphosis (TK) was not different between the 2 groups. When the immediate postoperative sagittal profiles were compared between the 2 groups, larger TK (23.72° vs. 18.86°, P = 0.009) and more obvious CL (7.26° vs. -2.60°, P = 0.001) were noticed in the L-AIS group. During the follow-up, larger TK and CL were still maintained in the L-AIS group. In addition, a significant correlation was found between the improvement of CL and TK restoration in patients with L-AIS (r = -0.473, P = 0.002).

CONCLUSIONS

Correlations between the improvement of CL and TK highlight the importance of restoration of patients with normal TK or AIS. Reciprocal changes in cervical alignment may happen if the TK was also simultaneously restored in patients with AIS. For patients with different curve patterns, the cervical sagittal parameters tend to be similar during follow-up.

Effect of the craniocervical brace on craniocervical angle, thoracic kyphosis angle, and trunk extensor muscle activity during typing in subjects with forward head posture

BACKGROUND

The relationship between forward head posture (FHP) and thoracic kyphosis has been a subject of interest in the rehabilitation field for visual display terminal workers.

OBJECTIVE

The aim of this study was to investigate the immediate effects of the craniocervical brace use on craniocervical angle (CCA), thoracic kyphosis angle (TKA), and trunk extensor muscle activity.

METHODS

Twelve young male subjects with forward head posture (21.6±1.9 years) participated in this study. We compared CCA & TKA and trunk extensor muscle activity between with and without application of the craniocervical brace during visual display terminal work.

RESULTS

When wearing the craniocervical brace, the subjects demonstrated significantly greater CCA at the start and the end of the task and less change in CCA during the task (p < 0.05). While non-significantly less TKA was seen at the start of the task, significantly less TKA was observed at the end of the task when using the craniocervical brace (p < 0.05). The craniocervical brace use also led to significantly less change in TKA (p < 0.05). There was no significant difference in the trunk extensor muscle activity.

CONCLUSIONS

Use of the craniocervical brace decreased FHP immediately, lessened thoracic kyphosis over time, and prevented the worsening of FHP and thoracic kyphosis during visual display terminal work.

Clinical Outcomes of Correcting Cervical Deformity in Cerebral Palsy Patients

OBJECTIVE

To assess several different cervical alignment parameters to determine the clinical relationship between cerebral palsy (CP) with cervical spondylotic myelopathy (CSM) and cervical deformity.

METHODS

This study included consecutive patients (N = 31) with CP CSM who underwent cervical operation between January 2006 and January 2014 and who had cervical deformities, such as angular and translational deformities. Cervical spine alignment was assessed with the following parameters: C2-7 Cobb angle, C2-7 sagittal vertical axis (SVA), and T1 slope minus C2-7 Cobb angle. Other clinical values were the manual muscle test, spasticity, grip and pinch test, Box and Block test, and Jebsen-Taylor Hand Function Test. Outcome assessments (Oswestry Neck Disability Index [NDI] and modified Barthel Index) were obtained for all patients pre- and postoperatively.

RESULTS

Mean follow-up duration was 3.5 years. There were 13 patients in the corrected group and 18 in the not corrected group. Angular and translational correction were 19.0° (C2-7 Cobb angle), 19.8° (T1 slope minus C2-7 Cobb angle), and 16 mm (C2-7 SVA). Postoperative NDI scores showed greater improvement in the corrected group than the uncorrected group (P = 0.049). In the corrected group, grip power increased postoperatively (8.9 ± 8.9 vs 15.5 ± 8.3; P = 0.021).

CONCLUSIONS

Surgical treatment for patients with CP CSM deformity helped alleviate symptoms. Postoperative NDI scores and hand function improved in patients with CP CSM deformity, especially those in the corrected group. Clinicians should consider correcting the deformity in patients with CP CSM.

Laminar closure after expansive open-door laminoplasty: fixation methods and cervical alignments impact on the laminar closure and surgical outcomes

BACKGROUND CONTEXT

Although several laminar fixation methods in expansive open-door laminoplasty (EODL) have been reported, the differences in outcomes between the methods have not been well understood.

PURPOSE

The aim of this study were to investigate the impact of laminar fixation methods and cervical spine alignment after EODL on clinical and radiological outcomes, and to investigate the impact of laminar closure on clinical outcomes.

STUDY DESIGN

This study is a retrospective review of clinical and radiological data.

PATIENT SAMPLE

The inclusion criteria were having undergone EODL with suture anchor (n=74, Anchor group) or hydroxyapatite spacers (n=65, Spacer group) for cervical spondylotic myelopathy (CSM). Different surgical procedures were used during two time periods: anchor technique from 2001 to 2006, and spacer technique from 2007 to 2012.

OUTCOME MEASURES

Japanese Orthopaedic Association (JOA) scores for cervical myelopathy were recorded. Cross-sectional areas (CSA) were measured preoperatively, and at 1 week, 6 months, and 2 years postoperatively at each level (C3-C6) using reconstructed axial computed tomography (CT) images. The CSA decrease of more than 20% was defined as laminar closure.

METHODS

The JOA scores and the CSA values were compared between the two groups (Anchor group vs. Spacer group) and subgroups (preoperative kyphosis vs. lordosis alignment, closure vs. non-closure groups).

RESULTS

In both groups, the mean CSA decreased at 6 months postoperatively compared with that at 1 week postoperatively. The CSA further decreased at 2 years postoperatively in the Anchor group but remained unchanged after 6 months in the Spacer group. The CSA remained unchanged in patients with preoperative lordosis in both groups. However, patients with kyphosis in the Anchor group showed a continuously decreasing CSA throughout the follow-up period, whereas CSA was stable in patients with kyphosis in the Spacer group (p<.01). Although the preoperative JOA scores did not differ between the closure and non-closure group (p=.924), the JOA score was significantly worse in the closure group at 1 and 2 years postoperatively (p=.023 and p=.011 respectively).

CONCLUSIONS

The patients with CSM with kyphosis in the Spacer group experienced significantly less laminar closure after EODL compared with patients in the Anchor group. Laminar closure greater than 20% was associated with poor outcome. Therefore, spacer fixation is preferable to anchor screw fixation during EODL in patients with kyphosis.

Factors that regulate spinal cord position after expansive open-door laminoplasty

INTRODUCTION

Although appropriate dorsal migration of the spinal cord is a desired end point of cervical laminoplasty, it is difficult to predict in advance the spinal cord position after surgery and to control it during surgery. The aim of the present study was to investigate the factors that affect postoperative spinal cord position after cervical laminoplasty using multivariable analysis.

MATERIALS AND METHODS

We retrospectively assessed 56 consecutive patients with cervical spondylotic myelopathy treated by open-door laminoplasty. The postoperative anterior space of the spinal cord was measured at 204 levels, and its maximum value was measured at 56 levels within the decompressed area. To identify the factors that regulate the postoperative spinal cord position, we evaluated seven radiological parameters, including the C3-C7 lordosis angle (LA), LA of the decompressed area, C3-C7 spinal cord lordosis angle (SCLA), SCLA of the decompressed area, spinal canal sagittal diameter at C5, number of expanded lamina, and postoperative dural sac diameter.

RESULTS

The postoperative anterior space of the spinal cord was 5.5 ± 1.4 mm, and its maximum value was 6.4 ± 1.3 mm. A multiple linear regression analysis revealed that the number of expanded laminae (standardized partial regression coefficient: β = 0.17, p = 0.009) and dural sac diameter (β = 0.43, p < 0.001) was significantly associated with anterior space of the spinal cord. Although these parameters were also significantly associated with the maximum value, their relative contributions were reversed; β = 0.49 (p < 0.001) for the number of expanded laminae and 0.25 (p = 0.029) for the dural sac diameter.

CONCLUSIONS

The number of expanded laminae and dural sac diameter was significantly associated with the spinal cord position after laminoplasty. These factors could help to predict spinal cord position following laminoplasty and achieve adequate indirect decompression of the spinal cord.

Cervical sagittal deformity develops after PJK in adult thoracolumbar deformity correction: radiographic analysis utilizing a novel global sagittal angular parameter, the CTPA

PURPOSE

To describe reciprocal changes in cervical alignment after adult spinal deformity (ASD) correction and subsequent development of proximal junctional kyphosis (PJK). This study also investigated these changes using two novel global sagittal angular parameters, cervical-thoracic pelvic angle (CTPA) and the T1 pelvic angle (TPA).

METHODS

Multicenter, retrospective consecutive case series of ASD patients undergoing thoracolumbar three-column osteotomy (3CO) with fusion to the pelvis. Radiographs were analyzed at baseline and 1 year post-operatively. Patients were substratified into upper thoracic (UT; UIV T6 and above) and lower thoracic (LT; UIV below T6). PJK was defined by >10° angle between UIV and UIV + 2 and >10° change in the angle from baseline to post-op.

RESULTS

PJK developed in 29 % (78 of 267) of patients. CTPA was linearly correlated with cervical plumbline (CPL) as a measure of cervical sagittal alignment (R = 0.826, p < 0.001). PJK patients had significantly greater post-operative CTPA and SVA than patients without PJK (NPJK) (p = 0.042; p = 0.021). For UT (n = 141) but not LT (n = 136), PJK patients at 1 year had larger CTPA (4.9° vs. 3.7°, p = 0.015) and CPL (5.1 vs. 3.8 cm, p = 0.022) than NPJK patients, despite similar corrections in PT and PI-LL.

CONCLUSIONS

The prevalence of PJK was 29 % at 1 year follow-up. CTPA, which correlates with CPL as a global analog of cervical sagittal balance, and TPA describe relative proportions of cervical and thoracolumbar deformities. Patients who develop PJK in the upper thoracic spine after thoracolumbar 3CO also develop concomitant cervical sagittal deformity, with increases in CPL and CTPA.

Compensatory modulation for severe global sagittal imbalance: significance of cervical compensation on quality of life in thoracolumbar kyphosis secondary to ankylosing spondylitis

PURPOSE

To investigate the cervical compensation pattern and to clarify relationships between cervical compensation and quality of life (QOL) in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis.

METHODS

A cross-sectional study of consecutive AS patients with thoracolumbar kyphosis was performed. Forty-four patients with hyperlordotic cervical spine were assigned to group A and sixteen with kyphotic cervical spine in group B. Sagittal parameters were measured and compared, including T1 slope, cervical lordosis (CL), cervical sagittal vertical axis (C-SVA), global SVA and global kyphosis (GK). Independent factors for cervical compensation were identified. To exclude confounding variables while comparing QOL between patients with hyperlordotic and kyphotic cervical spine, 31 patients were selected as group A-1, similar to 13 patients in group B-1 in the distribution of matching variables such as age, gender, course of disease, GK, global SVA and radiographic progression assessment for AS. The QOL was assessed by Neck Disability Index (NDI) and other indices.

RESULTS

Mean C-SVA was significantly lower in group A than in group B, whereas mean T1 slope, global SVA and GK were significantly larger in group A. T1 slope (36.0 %) was the independent factor for CL. T1 slope was correlated with CL, GK and global SVA in group A. Group A-1 showed lower NDI score. CL (59.6 %) independently affects NDI.

CONCLUSION

Notable cervical compensation exists in AS patients with thoracolumbar kyphosis. The cervical compensation responsive to global imbalance was mediated by T1 slope. AS patients with hyperlordotic cervical spine present with better QOL than patients with kyphotic cervical spine.

Loss of lordosis and clinical outcomes after anterior cervical fusion with dynamic rotational plates

PURPOSE

The cervical dynamic rotational plating system may induce bone graft subsidence, so it may cause loss of cervical lordosis. However there were few studies for alignments of cervical spines influencing the clinical results after using dynamic rotational plates. The purpose is to evaluate the effect of graft subsidence on cervical alignments due to the dynamic rotational cervical plates and correlating it with the clinical outcomes of patients undergoing anterior cervical fusion.

MATERIALS AND METHODS

Thirty-three patients with disease or fracture underwent anterior cervical decompression and fusion using a dynamic rotational plate. The presence and extent of implant complications, graft subsidence, loss of lordosis were identified and Visual Analog Scale score (VAS score), Japanese Orthopaedic Association score (JOA score), clinical outcomes based on Odom's criteria were recorded.

RESULTS

Fusion was achieved without implant complications in all cases. The mean graft subsidence at 6 months after the surgery was 1.46 mm. The lordotic changes in local cervical angles were 5.85° which was obtained postoperatively. VAS score for radicular pain was improved by 5.19 and the JOA score was improved by 3. Clinical outcomes based on Odom's criteria showed sixteen excellent, ten good and two satisfactory results. There was no significant relationship between clinical outcomes and changes in the cervical angles.

CONCLUSION

Dynamic rotational anterior cervical plating provides comparable clinical outcomes to that of the reports of former static cervical platings. The loss of lordosis is related to the amount of graft settling but it is not related to the clinical outcomes.