Relation between alignments of upper and subaxial cervical spine: a radiological study

Upper and lower cervical alignment parameters measured on supine magnetic resonance imaging with the occipital slope as a key marker of cervical alignment

Objectives

Cervical spine alignment is evaluated by measuring the cervical angles or parameters on standing plain radiography. In this study, we aimed to evaluate mainly the upper cervical alignment and the correlation between upper and lower cervical sagittal parameters measured on supine magnetic resonance imaging (MRI).

Materials and Methods

Cervical MRIs of 210 outpatients were reviewed to measure the upper and lower cervical sagittal parameters. Their mean values were compared with normative values measured on standing X-ray from the literature. Correlations between the parameters were analyzed using the Pearson's correlation coefficient.

Results

The C0 slope was correlated with all other parameters, except for the C2-7 sagittal vertical axis. The strongest correlations (r > 0.500) were between the CL and C2 slope, between the CO2 and C0 slope, and between the C2 slope and C0 slope.

Conclusion

On supine MRI, the C0 slope is a key marker of cervical spinal alignment. A strong correlation was observed between the C2 slope and C0 slope; therefore, the relationship between upper and lower cervical alignment could be assessed using slopes on MRI.

The Relationship Between Cervical Sagittal Balance and Type of Atlantoaxial Dislocation Secondary to Os Odontoideum

OBJECTIVE

To analyze the effect of cervical sagittal balance on the direction and type of atlantoaxial dislocation.

METHODS

Data of 55 patients seen at our hospital for atlantoaxial instability/dislocation caused by os odontoideum were reviewed. Radiographic variables, including T1 slope (T1S), C1-C2 angle, C2-C7 angle, C1-C2 sagittal vertical axis (SVA), C2-C7 SVA, and atlanto-dens interval (ADI), were measured preoperatively. Patients were divided into three groups according to ADI: anterior atlantoaxial dislocation, atlantoaxial instability, and posterior atlantoaxial dislocation. Differences within and between groups in radiographic variables and relationships between the investigated variables were analyzed.

RESULTS

ADI was strongly negatively associated with C1-C2 angle (r = -0.805, P < 0.05); whereas ADI had a medium-strength positive relationship with C2-C7 angle (r = 0.425, P < 0.05) and a medium-strength negative relationship with C2-C7 SVA (r = -0.411, P < 0.05). However, ADI was not significantly correlated with T1 slope (r = -0.092, P > 0.05).

CONCLUSIONS

The type and direction of atlantoaxial dislocation is closely associated with cervical sagittal balance. C2-C7 SVA is an important factor in assessing the direction of atlantoaxial subluxation secondary to os odontoideum. ADI decreases with increasing C2-C7 SVA. The larger the C2-C7 SVA, the more likely the atlantoaxial dislocation is to be posterior.

Comparison of three methods for measuring C0-1 angles and C0-2 angles

BACKGROUND

The mutual compensatory relationship between the upper cervical sagittal alignment and the lower cervical sagittal alignment has been repeatedly reported. However, the evaluation of the upper cervical sagittal parameters are varied in previous studies. This retrospective study was performed to compare three methods for measuring the upper cervical sagittal parameters.

METHODS

A total of 263 individuals with standing neutral lateral cervical radiographs were included in this study. The Frankfort horizontal line (FHL), foramen magnum line (FML), and McGregor line (ML) were separately used as the reference lines for measuring the C0-1 angle and C0-2 angle. Intraclass correlation (ICC) values were used to compare the consistency and repeatability of the three methods. Pearson's correlation analysis was used to analyze the correlation between the sagittal parameters of the upper and lower cervical spine.

RESULTS

The interobserver and intraobserver ICC values obtained from using the ML to measure the C0-1 angle and C0-2 angle were both higher than those obtained from using the FML or FHL. The C0-1 angle and C0-2 angle measured by the three methods were negatively correlated with the C2-7 angle. The upper sagittal parameters measured by the FHL were the most correlated with the C2-7 angle. The correlation between the C0-1 angle measured by the three methods and the C0-2 angle measured with the FHL or ML and the C2-7 angle increased with aging.

CONCLUSION

Use of the ML to measure the C0-1 angle and C0-2 angle has higher reliability. Use of the FHL to measure the sagittal alignment of the upper cervical spine is more suitable for evaluating the compensation mechanism between the upper and the lower cervical spine.

Analysis of Components of Upper Cervical Lordosis in Asymptomatic Lordotic and Kyphotic Subjects

BACKGROUND

Upper cervical lordosis (CL) can be divided into 2 components: C2 slope (C2S) and McGregor slope (MGS) or C0-1 and C1-2 angles. The aim of this study was to investigate the components of upper CL in asymptomatic kyphotic and lordotic subjects.

METHODS

CL, C0-2 Cobb angle, MGS, C2S, C1 Slope, C0-1 Cobb angle, C1-2 Cobb angle, T1 slope angular parameters, and the C2-7 sagittal vertical axis distance of 78 asymptomatic subjects were measured.

RESULTS

Sixty subjects had lordotic curvature and 18 had kyphotic curvature. There was a significant difference between the kyphotic and lordotic groups in all parameters, except for C0-1 Cobb angle and C2-7 sagittal vertical axis. In lordotic subjects, MGS and C2S accounted for 58% and 42% of the C0-2 angle, whereas in kyphotic subjects, 86% of C0-2 was accounted for by C2S. There was a strong negative correlation between C2S and MGS.

CONCLUSIONS

In asymptomatic subjects, as CL decreases, MGS decreases, C2S increases, and the C0-2 angle turns down on the horizontal plane to maintain the horizontal gaze. Turning down the C0-2 angle is more important than its value for maintaining horizontal gaze; thus, the slopes (MGS and C2S) can better represent the upper and lower cervical alignment than angle values can. The relationship between upper and lower cervical alignment should be evaluated in terms of slope angles rather than simple angles. The lack of significant difference between the C0-1 angles in the kyphotic and lordotic groups suggests that only the C1-2 angle is involved in the compensatory mechanism for the horizontal gaze.

Severe dysphagia after a posterior cervical spine fusion at the C1–C3 level and its improvement after correction surgery for malalignment: a case report

Background

The development of dysphagia and trismus following posterior C1–C3 fusion is rare compared to occipitocervical fusion, and there are very few reports in the literature.

Case presentation

A 75-year-old Thai man who had an extradural tumor at the C1/C2 level developed severe dysphagia and trismus immediately after tumor resection and C1–C3 fusion. During the surgery for malalignment correction, the C1–C2 screws were re-aligned into an increased lordotic position. The symptoms resolved immediately post-surgery.

Conclusions

Short upper cervical fusion can produce trismus and dysphagia in a relatively flexed position. Preoperative planning should be individualized based on the patient’s resting neutral alignment to prevent complications.

Cervical Sagittal Alignment in Patients With Basilar Invagination

STUDY DESIGN

Retrospective study.

OBJECTIVE

To present a morphological map of cervical sagittal alignment in basilar invagination (BI), a congenital anomaly of the craniovertebral junction, and contribute to a comprehensive understanding of cervical sagittal alignment in congenital cervical deformities.

SUMMARY OF BACKGROUND DATA

Ideal cervical sagittal alignment and surgical targets are debated by scholars. However, most of the literature focuses on the description of cervical sagittal alignment in acquired cervical diseases and normal subjects and few on congenital cervical spine deformities.

MATERIALS AND METHODS

This study analyzed cervical spine lateral radiographs of 87 BI patients and 98 asymptomatic subjects. They were analyzed for cranial, cervical spine, and thoracic inlet parameters.

RESULTS

Patients with BI manifested significantly larger values for the following parameters than asymptomatic subjects: cranial tilt, cranial incidence angle, sagittal vertical axis (SVA) CGH-C7, C2-C7 angle, cervical tilt, and significantly smaller values for the following parameters: cranial slope, C0-C2 angle, C0-C7 angle, SVA C2-C7, spine tilt, thoracic inlet angle, and neck tilt. In the BI group, SVA C2-C7 was the cervical parameter most strongly correlated with the cranial, cervical spine, and thoracic inlet parameters, and was smaller in BI patients with fusion (atlanto-occipital assimilation) than in those without.

CONCLUSION

A significant difference was observed between BI patients and asymptomatic subjects. BI patients have craniums tilted forward and downward, smaller upper cervical lordosis, larger lower cervical lordosis, and smaller thoracic inlet angle. In BI patients, the SVA C2-C7 is an important parameter in cervical sagittal alignment. In both individuals with congenital anomalies of the craniovertebral junction and the asymptomatic population, cervical spine alignment is significantly associated with cranial alignment, particularly thoracic inlet alignment.

Is gender a factor affecting long-term heterotopic ossification incidence after single-level cervical disc arthroplasty?

BACKGROUND

Cervical disc diseases have been treated by means of cervical disc arthroplasty (CDA). Nevertheless, some patients will experience a mobility failure in their cervical prostheses over time because of heterotopic ossification (HO). Aim of this study is to investigate the role of gender in long-term outcomes after CDA.

MATERIALS AND METHODS

A retrospective, single-center study including patients who underwent single-level CDA with a Bryan prosthesis was performed, including a narrative review about gender differences in both structural and biomechanical features of the cervical spine.

RESULTS

Study patients (14M, 30F) had an average follow-up period of 9,8 ± 3,2 years. Significant differences emerged between genders for specific items in Neck Disability Index (NDI) preoperative evaluation, with females reporting worse pain scores (p=0.05). After stratification by age we report a higher preoperative overall NDI score for female patients under 36 years of age (p=0.03). In an intergender, BMI-specific comparison we also found a significant difference in NDI preoperative score with normal-weight male patients faring worse than overweight ones (p= 0.05). At a radiological level, we found a tendency towards a higher HO incidence in male patients (62% males, 17% females, p=0.06). Women's cervical spine has peculiar features including bone structure, muscular action, soft-tissue response, genetic and epigenetic response to osteoarthritis.

CONCLUSION

The incidence of mobility failure in our series of single-level CDA was lower in females. Several gender specific factors both in static and dynamic features may play a significant role in spinal pathology and CDA long-term radiological outcome.

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.

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.

Sequential sagittal alignment changes in the cervical spine after occipitocervical fusion

BACKGROUND

There are few studies regarding sequential changes in the sagittal alignment of the upper and lower cervical regions of the spine after occipitocervical fusion (OCF). In addition, no comparisons of cervical sagittal alignment (CSA) between patients with craniocervical junction disorders (CJDs) and normal populations have been reported.

AIM

To compare the CSA of patients with CJDs with that of normal controls and investigate the sequential changes in the CSA of the upper and lower cervical spine after OCF.

METHODS

Eighty-four patients who underwent OCF (OCF group) and 42 asymptomatic volunteers (control group) were included. Radiographic parameters, including the occipital to C2 angle (O-C2a), occipital and external acoustic meatus to axis angle (O-EAa), C2–7 angle (C2-7a), and pharyngeal inlet angle (PIA), were measured and compared pre- and postoperatively. The correlations among the parameters were analyzed using Pearson’s correlation test.

RESULTS

The O-C2a and PIA of the OCF group were smaller than those of the control group, while their O-EAa and C2-7a values were larger than those of the normal controls. There were no significant differences in O-C2a, C2-7a, or PIA in the OCF group at baseline, 1 mo, or the final follow-up after surgery. The Pearson’s correlation results showed that there were significant correlations between the O-C2a and C2Ta, C2-7a, C2-7 sagittal vertical axis (SVA), and PIA at 1 mo after OCF surgery and between O-C2a and O-EAa, C2Ta, C2-7a, C2-7 SVA, and PIA at the final follow-up.

CONCLUSION

Patients with CJDs have a more kyphotic upper CSA and a more lordotic lower CSA than normal controls. The effectiveness of OCF surgery in restoring CSA may be limited by the realignment of the craniocervical junction being neglected. The reduction in O-C2a after OCF surgery may increase C2-7a and decrease PIA.

Surgical resection of intradural extramedullary tumors in the atlantoaxial spine via a posterior approach

BACKGROUND

The anatomical features of the atlantoaxial spine increase the difficulty of complete and safe removal of atlantoaxial intradural extramedullary (IDEM) tumors. Studies concerning surgical interventions via a posterior approach are limited.

AIM

To investigate the safety and efficacy of atlantoaxial IDEM tumor resection using a one-stage posterior approach.

METHODS

We retrospectively analyzed clinical databases for one-stage atlantoaxial IDEM tumor resection via a posterior approach between January 2008 and January 2018. The analyzed data included tumor position, histopathological type, pre- and post-operative Japanese Orthopedic Association (JOA) scores and Nurick grades, postoperative complication and recurrence status.

RESULTS

A total of 13 patients who underwent C1-C2 Laminectomy and/or unilateral facetectomy via the posterior approach were enrolled in the study. In all cases reviewed, total tumor resection and concomitant C1-C2 fusion were achieved. The average follow-up was 35.3 ± 6.9 mo (range, 26-49 mo). A statistically significant difference was noted between the preoperative JOA score (11.2 ± 1.1) and the score at the last final follow-up (15.6 ± 1.0) (P < 0.05). A statistically significant difference was noted between the preoperative Nurick grade (2.3 ± 0.9) and that at the last follow-up (1.2 ± 0.4) (P < 0.05). However, no statistically significant difference was noted between the preoperative and last follow-up C1-2 Cobb angle and C2-7 Cobb angle (P > 0.05). No mortalities, severe complications or tumor recurrence were observed during the follow-up period.

CONCLUSION

Total resection of atlantoaxial IDEM tumors is feasible and effective via a posterior approach. Surgical reconstruction should be considered to avoid iatrogenic kyphosis and improve spinal stability and overall clinical outcomes.

Cervical deformity patients with baseline hyperlordosis or hyperkyphosis differ in surgical treatment and radiographic outcomes

Background

Patients with symptomatic cervical deformity (CD) requiring surgical correction often present with hyperkyphosis (HK), although patients with hyperlordotic curves may require surgery as well. Few studies have investigated differences in CD corrective surgery with regard to HK and hyperlordosis (HL).

Objective:

The objective of the study is to evaluate patterns in treatment for CD patients with baseline (BL) HK and HL and understand how extreme curvature of the spine may influence surgical outcomes.

Materials and Methods:

Operative CD patients with BL and 1-year (1Y) radiographic data were included in the study. Patients were stratified based on BL C2–C7 lordosis (CL) angle: those >1 standard deviation (SD) from the mean (−6.96 ± 21.47°) were hyperlordotic (>14.51°) or hyperkyphotic (<−28.43°) depending on directionality. Patients within 1SD were considered control group.

Results:

102 surgical CD patients (61 years, 65% F, 30 kg/m²) with BL and 1Y radiographic data were included. 20 patients met definitions for HK and 21 patients met definitions for HL. No differences in demographics or disability were noted. HK had higher estimated blood loss (EBL) with anterior approaches than HL but similar EBL with posterior approach. Operative time did not differ between groups. Control, HL, and HK groups differed in BL TS-CL (36.6° vs. 22.5° vs. 60.7°, P < 0.001) and BL-SVA (10.8 vs. 7.0 vs. −47.8 mm, P = 0.001). HL patients had less discectomies, less corpectomies, and similar osteotomy rates to HK. HL had 3x revisions of HK and controls (28.6 vs. 10.0 vs. 9.2%, respectively, P = 0.046). At 1Y, HL patients had higher cSVA and trended higher SVA and SS than HK. In terms of BL-upper cervical alignment, HK patients had higher McGregor's slope (MGS) (16.1° vs. 3.3°, P = 0.002) and C0–C2 Cobb (43.3° vs. 26.9°, P < 0.001), however, postoperative differences in MGS and C0–C2 were not significant. HK drivers of deformity were primarily C (90%), whereas HL had primary CT (38.1%), UT (23.8%), and C (14.3%) drivers.

Conclusions:

Hyperlodotic patients trended higher revision rates with greater radiographic malalignment at 1-year postoperative, perhaps due to undercorrection compared to kyphotic etiologies.

Efficacy of a Lateral Mass Fusion Device Combined with a Three-Dimensional-Printed Model in the Treatment of Craniovertebral Junction Abnormalities

OBJECTIVE

To investigate the efficacy of a lateral mass fusion device combined with a three-dimensional-printed model in treatment of craniovertebral junction abnormalities.

METHODS

This retrospective study comprised 56 patients with irreducible atlantoaxial dislocation who underwent posterior fixation between January 2016 and December 2019. Patients were divided into 2 groups according to whether or not cages were used-cage group and autograft group. Visual analog scale score, Japanese Orthopaedic Association score, health-related quality of life, American Spinal Injury Association spinal cord injury grade, atlas-dens interval, space available for the cord, cervicomedullary angle, and fusion rate were compared between groups.

RESULTS

Medical follow-up was >1 year. There was no statistical difference between groups in preoperative visual analog scale score, Japanese Orthopaedic Association score, 12-Item Short Form Health Survey score, American Spinal Injury Association grade, atlas-dens interval, space available for the cord, and cervicomedullary angle, and these indexes significantly improved after surgery (P < 0.05). Visual analog scale score and atlas-dens interval were lower in the cage group than in the autograft group (P < 0.05). Japanese Orthopaedic Association score, 12-Item Short Form Health Survey score, space available for the cord, and cervicomedullary angle were significantly higher in the cage group than in the autograft group (P < 0.05). Fusion rate of the cage group 4-6 months after surgery was higher than that of the autograft group (P = 0.068). American Spinal Injury Association grade was significantly higher in the cage group than in the autograft group (P < 0.05).

CONCLUSIONS

During 1-year follow-up, neurological function improvement and atlantoaxial joint reduction were satisfactory. The lateral mass fusion device combined with a three-dimensional printed model may be a clinically useful technique.

Cervical deformity patients with baseline hyperlordosis or hyperkyphosis differ in surgical treatment and radiographic outcomes

Introduction:

Patients with symptomatic cervical deformity (CD) requiring surgical correction often present with hyperkyphosis (HK), though patients with hyperlordotic curves may require surgery as well. Few studies have investigated differences in CD-corrective surgery with regards to HK and hyperlordosis (HL).

Materials and Methods:

Operative CD patients (C2-C7 Cobb >10°, cervical lordosis [CL] >10°, cervical sagittal vertical axis [cSVA] >4 cm, chin-brow vertical angle >25°) with baseline (BL) and 1Y radiographic data. Patients were stratified based on BL C2-7 lordosis (CL) angle: those >1 standard deviation (SD) from the mean (−6.96° ±21.47°) were hyperlordotic (>14.51°) or hyperkyphotic (≤28.43°) depending on directionality. Patients within 1 SD were considered the control group.

Results:

One hundred and two surgical CD pts (61 years, 65%F, 30 kg/m²) with BL and 1Y radiographic data were included. Twenty pts met definitions for HK and 21 pts met definitions for HL. No differences in demographics or disability were noted. HK had higher estimated blood loss (EBL) with anterior approaches than HL but similar EBL with the posterior approach. Op-time did not differ between groups. Control, HL, and HK groups differed in BL TS-CL (36.6° vs. 22.5° vs. 60.7°, P < 0.001) and BL-sagittal vertical axis (SVA) (10.8 vs. 7.0 vs. −47.8 mm, P = 0.001). HL pts had less discectomies, less corpectomies, and similar osteotomy rates to HK. HL had × 3 revisions of HK and controls (28.6 vs. 10.0 vs. 9.2%, respectively, P = 0.046). At 1Y, HL pts had higher cSVA, and trended higher SVA and SS than HK. In terms of BL-upper cervical alignment, HK pts had higher McGregor's-slope (16.1° vs. −3.3°, P = 0.001) and C0-C2 Cobb (43.3° vs. 26.9°, P < 0.001), however postoperative differences in McGregor's slope and C0-C2 were not significant. HK drivers of deformity were primarily C (90%), whereas HL had primary computed tomography (38.1%), upper thoracic (23.8%), and C (14.3%) drivers.

Conclusions:

Hyperlodotic patients trended higher revision rates with greater radiographic malalignment at 1Y postoperative, perhaps due to undercorrection compared to kyphotic etiologies.

Sagittal wedging of intervertebral discs and vertebral bodies in the cervical spine and their associations with age, sex and cervical lordosis: A large-scale morphological study

Many recent studies have focused on the functional and clinical importance of cervical lordosis. However, there is little accurate knowledge of the anatomical parameters that constitute cervical lordosis (i.e., the sagittal wedging angles of intervertebral discs and vertebral bodies) and their associations with age and sex. Standing lateral cervical radiographs of 1020 subjects (424 males, 596 females) with a mean age of 36.6 ± 17.0 years (range 7-95 years) were evaluated retrospectively. Cervical lordosis, the sum of intervertebral disc wedging angles from C2/C3 to C6/C7 and the sum of vertebral body wedging angles from C3 to C7 were measured. The sum of intervertebral disc wedging and the sum of vertebral body wedging were 20.6° ± 14.7° and -12.8° ± 10.3°, respectively. The sum of intervertebral disc wedging increased significantly with age and was significantly greater in males than females, whereas there was no sex-related difference in the sum of vertebral body wedging. The sum of intervertebral disc wedging was negatively correlated with sum of vertebral body wedging. Wedging of discs contributed to C2-C7 cervical lordosis more significantly than wedging of vertebral bodies. There were moderate positive correlations between cervical lordosis and intervertebral disc wedging angles at C3/C4, C4/C5 and C5/C6; weak correlations were observed at C2/C3 and C6/C7. This study constitutes the largest currently available analysis comprehensively documenting the anatomical characteristics of sagittal wedging of intervertebral discs and vertebral bodies in the cervical spine. The findings could improve understanding of the internal architecture of cervical lordosis among clinicians.

Radiological changes in sagittal parameters after C1-C2 arthrodesis and their clinical correlation: Is there a difference between traumatic and non-traumatic causes?

Background: Compensatory changes in cervical sagittal alignment after C1-C2 arthrodesis have been reported in a few studies. No studies have explored the differences in these compensatory changes between traumatic and non-traumatic pathologies. Conflicting reports exist on the correlation between cervical sagittal parameters and neck pain or function.Methodology: Medical records of 81 consecutive patients [Jan 2010 - Dec 2018] who underwent Harms arthrodesis were retrospectively reviewed. 53 patients were included in the final analysis. Radiological parameters [C0-C1, C1-C2, C2-C7 angles and T1 slope] and clinical parameters [VAS (Visual analogue scale) and NDI (Neck disability index)] were compared between the two groups, Group A (traumatic) and Group B (non-traumatic).Results: The 53 patients [Group A (n = 24,) and Group B (n = 29)] had a mean age of 49.98 ± 21.82 years (42 males, 11 females). Mean follow up duration was 48.9 months. Δ C1-C2 angle is significantly correlated with ΔC2-C7 angle (Group A, p = 0.004; Group B, p = 0.015) but not with ΔC0-C1 angle (Group A, p = 0.315; Group B, p = 0.938). Though significant improvement in the clinical parameters (VAS/NDI) has been noted in both groups, Group A showed a greater improvement in VAS scores [Group A, (p < 0.001); Group B, (p < 0.023)].Conclusions: The sub-axial sagittal profile was strongly correlated with the ΔC1-C2 angle in both groups. Group B showed greater changes in sagittal parameters after Harms fixation and Group A showed greater improvement in long-term functional outcomes. The final functional outcomes were not related to the initial or final radiological sagittal profile in both groups.

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

BACKGROUND

Atlantoaxial fusion has been widely used for the treatment of atlantoaxial instability (AAI). However, atlantoaxial fusion sacrifices the motion of atlantoaxial articulation, and postoperative loss of cervical lordosis and aggravation of cervical kyphosis are observed. We investigated various factors under the hypothesis that the atlantodental interval (ADI) and T1 slope may be associated with sagittal alignment after atlantoaxial fusion in patients with rheumatoid arthritis (RA).

METHODS

We retrospectively investigated 64 patients with RA who underwent atlantoaxial fusion due to AAI. Radiological factors, including the ADI, T1 slope, Oc-C2 angle, cervical sagittal vertical axis, and C2-C7 angle, were measured before and after surgery.

RESULTS

The various factors associated with atlantoaxial fusion before and after surgery were compared according to the upper and lower preoperative ADIs. There was a significant difference in the T1 slope 1 year after surgery (p = 0.044) among the patients with lower preoperative ADI values. The multivariate logistic regression analysis showed that the preoperative ADI (> 7.92 mm) defined in the receiver-operating characteristic curve analysis was an independent predictive factor for the increase in the T1 slope 1 year after atlantoaxial fusion (odds ratio, 4.59; 95% confidence interval, 1.34-15.73; p = 0.015).

CONCLUSION

We found an association between the preoperative ADI and difference in the T1 slope after atlantoaxial fusion in the patients with RA. A preoperative ADI (> 7.92 mm) was an independent predictor for the increase in the T1 slope after atlantoaxial fusion. Therefore, performing surgical treatment when the ADI is low would lead to better cervical sagittal alignment.

The 3 Sagittal Morphotypes That Define the Normal Cervical Spine: A Systematic Review of the Literature and an Analysis of Asymptomatic Volunteers

BACKGROUND

Cervical alignment is vital for maintaining horizontal gaze and sagittal balance. The aims of this study were to summarize previously published descriptions of normative cervical alignment and to analyze a cohort of asymptomatic volunteers in order to identify natural clusters of normal radiographic parameters.

METHODS

We performed a systematic review of the literature on radiographic measurements of asymptomatic volunteers through a search of MEDLINE and ScienceDirect databases. We then performed an analysis of demographic and radiographic parameters of volunteers without back or neck complaints. Only subjects with a chin-brow vertical angle (CBVA) within previously published normal limits were retained for analysis. A 2-step cluster analysis was used to find natural groups of cervical alignment. Differences among groups were investigated with a post hoc analysis of variance (ANOVA).

RESULTS

We included 37 articles in our analysis. There was a broad spectrum of both C2-C7 lordosis-kyphosis and T1 slope across ages and sexes. Of the 119 asymptomatic volunteers who were available for analysis, 84 (with a mean age [and standard deviation] of 49.0 ± 17.1 years) had a CBVA ranging from -4.7° to 17.7°. The cluster analysis identified 3 alignment groups based on cervical lordosis-kyphosis and T1 slope (silhouette measure of cohesion, >0.6). Twenty-seven volunteers (32.1%) were identified as the "kyphotic curve cohort" (KCC) (mean C2-C7 Cobb angle, -8.6° ± 7.3°; mean T1 slope, 17.4° ± 6.6°), 43 volunteers (51.2%) were identified as the "medium lordosis cohort" (MLC) (mean C2-C7 Cobb angle, 8.7° ± 7.2°; mean T1 slope, 26.6° ± 4.0°), and 14 volunteers (16.7%) were identified as the "large lordosis cohort" (LLC) (mean C2-C7 Cobb angle, 21.2° ± 7.2°, mean T1 slope, 39.5° ± 6.4°) (p < 0.001 for both). Moving from KCC to LLC, there was a significant decrease in C0-C2 lordosis (p = 0.016). Examination of the cervical vertebral orientation demonstrated that C4 had a constant orientation relative to the horizontal (p = 0.665). Correlation analysis between C2-C7 and vertebral orientations again demonstrated that C4 orientation was independent of C2-C7 alignment.

CONCLUSIONS

We have identified 3 morphotypes of the cervical spine based on C2-C7 alignment and T1 slope. These findings demonstrate the broad definition of normal cervical alignment and the range of cervical lordosis-kyphosis that is acceptable.

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?

Immersive Surgical Anatomy of the Craniocervical Junction

With the advent and increased usage of posterior, lateral, and anterior surgical approaches to the craniocervical junction (CCJ), it is essential to have a sound understanding of the osseous, ligamentous, and neurovascular layers of this region as well as their three-dimensional (3D) orientations and functional kinematics. Advances in 3D technology can be leveraged to develop a more nuanced and comprehensive understanding of the CCJ, classically depicted via dissections and sketches. As such, this study aims to illustrate - with the use of 3D technologies - the major anatomical landmarks of the CCJ in an innovative and informative way. Photogrammetry, structured light scanning, and 3D reconstruction of medical images were used to generate these high-resolution volumetric models. A clear knowledge of the critical anatomical structures and morphometrics of the CCJ is crucial for the diagnosis, classification, and treatment of pathologies in this transitional region.

Is it Suitable to Fix the Occipito-C2 Angle and the Posterior Occipitocervical Angle in a Normal Range During Occipitocervical Fusion?

STUDY DESIGN

This is a retrospective study.

OBJECTIVES

The objective of this study was (1) to measure the occipito-C2 angle (OC2A) and the posterior occipitocervical angle (POCA) in a normal population, and (2) to observe the effects of OC2A and POCA selection on postoperative clinical efficacy and lower cervical curvature after occipitocervical fusion (OCF) in patients with basilar invagination (BI) and atlantoaxial fracture and dislocation (AAFD).

SUMMARY OF BACKGROUND DATA

OC2A has received special attention with respect to the clinical efficacy during OCF. However, none of studies have focused on the relationship between OC2A and POCA and have assessed their impact on clinical outcomes in patients with different occipiocervical diseases.

MATERIALS AND METHODS

One hundred fifty healthy subjects without any cervical disease (healthy group) were randomly selected based on sex and age. Three spine surgeons measured the OC2A and POCA in the healthy group and averaged the values. Forty-two patients with BI (BI group) and 32 patients with AAFD (AAFD group) who underwent OCF between January 2012 and January 2017 were reviewed. OC2A, POCA, and cervical spinal angle (CSA) were measured preoperatively, postoperatively immediately after surgery and ambulation, and at the final follow-up visit. The preoperative and final follow-up visual analog scale (VAS), Japanese Orthopaedic Association score (JOA), neck disability index (NDI), and the change of CSA from postoperatively immediately after surgery and ambulation to the final follow-up (dCSA) were recorded.

RESULTS

The values of OC2A and POCA were 14.5±3.7 and 108.2±8.1 degrees in the healthy group, respectively, and the respective 95% confidence intervals were 7.2-21.8 and 92.3-124.0 degrees as the normal range. There was a negative correlation between OC2A and POCA (r=-0.386, P<0.001). The preoperative value of OC2A (5.6±4.3 degrees) in BI group was smaller than that in the healthy group (P<0.05); however, the preoperative value of POCA (123.0±10.4 degrees) in the BI group was larger than that in the healthy group (P<0.05). There was no significantly different of OC2A and POCA between the healthy group and the AAFD group before the operation (P>0.05). The preoperative value of CSA (25.7±9.5 degrees) in the BI group was larger than that in the AAFD group (16.5±5.1 degrees) (P<0.05). In the BI group, 26 patients had ideal OC2A and POCA (both within 95% confidence interval of the healthy group) postoperatively immediately after surgery and ambulation as a subgroup of the ideal angle group. In the remaining patients with BI (nonideal angle group), VAS, JOA, and NDI at the final follow-up were significantly better than those in the ideal angle group (P<0.05). The ideal angle group showed statistically greater dCSA than the nonideal angle group of the BI group (P<0.05). On the contrary, in the AAFD group, the NDI in the ideal angle group (20 patients) was better than that in the nonideal angle group at the final follow-up, and the ideal angle group had a smaller dCSA compared with the nonideal angle group (P<0.05).

CONCLUSIONS

The biomechanical balance of occipitocervical region in patients with occipitocervical diseases with different pathogenesis is different. On the basis of the different types of occipitocervical diseases, an appropriate range of OC2A and POCA should be selected by the surgeon during OCF, which can further improve the clinical efficacy and reduce the loss of the lower cervical curvature after surgery.

Posterior Occipitocervical Fusion for Unstable Upper Cervical Trauma in Old and Elderly Population, Although Decreases Upper Cervical Rotation, Does Not Significantly Increase Neck Disability Index

Background

Despite the research progress in the thoraco-lumbo-pelvic balance, cervical spine balance has only recently gained increasing interest. To our knowledge, there is a lack of research regarding sagittal occipitocervical spine balance restoration following posterior occipitocervical fusion (POCF).

Purpose

The primary outcome measure is the evaluation of sagittal cervical alignment roentgenographic parameters and the secondary is the functional outcome (NDI), following POCF for upper (C1 & C2) cervical trauma (UCT) in coexistence with upper cervical spine degeneration. Patients and Methods. Twenty old and elderly patients aged 62 ± 12 years with evident upper cervical degeneration, who received POCF for upper C1 & C2 unstable cervical spine injuries, were included. C2-C7 lordosis, C2-C7 SVA, spinocranial angle (SCA), T1-slope, neck tilt (NT), thorax inlet angle (TIA), cervical tilt (CT), cranial tilt (CrT), and C0-C1 angle were measured. The subfusion angle was used to study the behavior of the unfused cervical segments below fusion. The Neck Disability Index (NDI) was used for the functional outcome evaluation. 29 age-matched individuals were used as controls for radiographic analysis and self-reported functional status comparison.

Results

The roentgenographic data were measured 3 and 39 ± 12 months postoperatively. Twelve patients showed no disability, and eight showed mild disability. Postoperatively, the patients stood with less C2-C7 lordosis, SCA, and CT (P < 0.02) but with higher NT (P < 0.02) in comparison to the controls. The patient's neck disability (NDI) was increasing as TIA increases (P=0.023). Subfusion angle seems to adapt to C2-C7 lordosis (P < 0.0033) and C0-C2 angle (P < 0.003) without any changes till the last evaluation.

Conclusions

POCF sufficiently restored occipitocervical sagittal balance along with functional outcome similar to controls in adult and elderly individuals with evident upper cervical degeneration. We do not recommend POCF for young active individuals without occipitocervical pathology, but in contrary, we recommend the removal of the spinocranial connection hardware after cervical fusion is completed.

Is Initial Posterior Atlantoaxial Fixation and Fusion Applying Bilateral C1-2 Transarticular Screws and C1 Laminar Hooks Reliable for Acute Pediatric Atlantoaxial Instability?: A Minimal 10-Year Analysis of Outcome and Radiological Evaluation

STUDY DESIGN

A retrospective case series study with at least 10 years of follow-up data.

OBJECTIVE

To validate the reliability of bilateral C1-2 transarticular screws and C1 laminar hooks and a bone autograft for acute pediatric atlantoaxial instability.

SUMMARY OF BACKGROUND DATA

The reliability of initial posterior atlantoaxial fusion in pediatric patients is still controversial. To date, however, only a few published articles with short-term follow-up data are available to help spinal surgeons understand the effects of posterior atlantoaxial fusion in the skeletally immature spine.

METHODS

Five pediatric patients with acute atlantoaxial instability underwent atlantoaxial fusion using the above technique over a 3-year period. During a minimum 10-year follow-up period, not only outcomes and complications were investigated, but the vertical growth of the constructed spine in relation to the growth of the entire cervical spine, overall cervical spinal alignment, and adjacent-segment instability were evaluated.

RESULTS

The clinical follow-up indicated solid fusion and complete clinical relief from symptoms. No neural or vascular impairment was observed. The radiological evaluation showed that all patients had growth within the fusion construct reaching a mean 35.4% of the entire cervical spine. There were no radiological indicators of subaxial instability, even when cervical sagittal alignments became straight with a mean C2-7 angle of 6.4°.

CONCLUSION

The results showed that initial posterior atlantoaxial fusion accomplished with bilateral C1-2 transarticular screws, C1 laminar hooks fixation, and bony autograft is a reliable surgical technique for treating acute pediatric atlantoaxial instability without negative effects on vertical growth at the fused level or the stability of the subaxial spine.

LEVEL OF EVIDENCE

3.

Influence of extending expansive open-door laminoplasty to C1 and C2 on cervical sagittal parameters

Background

For patients with spinal canal stenosis in the upper cervical spine who undergo C3–7 laminoplasty alone, it remains impossible to achieve full decompression due to its limited range. This study explores the extension of expansive open-door laminoplasty (EODL) to C1 and C2 for the treatment of cervical spinal stenosis of the upper cervical spine and its effects on cervical sagittal parameters.

Methods

A retrospective analysis of 33 patients presenting with symptoms of cervical spondylosis myelopathy (CSM) and ossification in the posterior longitudinal ligament (OPLL) of the upper cervical spine from February 2013 to December 2015 was performed. Furthermore, the changes in the C0–2 Cobb angle, C1–2 Cobb angle, C2–7 Cobb angle, C2–7 SVA, and T1-Slope in lateral X-rays of the cervical spine were measured before, immediately after, and 1 year after the operation. JOA and NDI scores were used to evaluate spinal cord function.

Results

The C0–2 and C1–2 Cobb angles did not significantly increase (P = 0.190 and P = 0.081), but the C2–7 Cobb angle (P = 0.001), C2–7 SVA (P < 0.001), and T1-Slope (P < 0.001) significantly increased from preoperative to 1 year postoperative. In addition, C2–7 SVA was significantly correlated with the T1-Slope (Pearson = 0.376, P < 0.001) and C0–2 Cobb angle (Pearson = 0.287, P = 0.004), and the C2–7 SVA was negatively correlated with the C2–7 Cobb angle (Pearson = − 0.295, P < 0.001). The average preoperative and postoperative JOA scores were 8.3 ± 1.6 and 14.6 ± 1.4 points, respectively, indicating in a postoperative neurological improvement rate of approximately 91.6%. The average preoperative and final follow-up NDI scores were 12.62 ± 2.34 and 7.61 ± 1.23.

Conclusions

The sagittal parameters of patients who underwent EODL extended to C1 and C2 included loss of cervical curvature, increased cervical anteversion and compensatory posterior extension of the upper cervical spine to maintain visual balance in the field of vision. However, the changes in cervical spine parameters were far less substantial than the alarm thresholds reported in previous studies. We believe that EODL extended to C1 and C2 for the treatment of patients with spinal canal stenosis in the upper cervical spine is a feasible and safe procedure with excellent outcomes.

The Sagittal Balance of the Cervical Spine: Radiographic Analysis of Interdependence between the Occipitocervical and Spinopelvic Alignment

Study Design

This was a prospective clinical study.

Purpose

Previous studies have indicated that cervical lordosis is a parameter influenced by segmental and global spinal sagittal balance parameters. However, this correlation still remains unclear. Therefore, a better understanding of the normal values and interdependencies between inter-segmental alignment parameters is needed. This is a preliminary analysis that helps to understand these factors.

Overview of Literature

Change in global sagittal alignment is associated with poor health-related quality of life. Questions regarding which parameters play the primary roles in the progression of spinal sagittal imbalance and which might be compensatory factors remain unanswered.

Methods

Prospectively, 420 adults (105 asymptomatic, 105 cervical symptomatic, 105 lumbar symptomatic, and 105 post-surgical) were selected. Whole-spine standing lateral radiographs were taken, and spinopelvic, thoracic, and cervical parameters were measured. Then, the data were analyzed using correlation coefficient test and multiple regression analysis.

Results

All the parameters showed a normal distribution. The mean values of the cervical parameters are as follows: C₁C₂ Cobb angle, −27.07°±4.3°; C₂C₇ Cobb angle, −16.4°±5.6°; O_CC₂ Cobb angle, −14.5°±3.8°; O_CC₇ Cobb angle, −29.8°±5.6°; C₂C₇ Harrison angle, 20.4°±4.3°; and C₇ slope, −25.4°±5.6°. The analysis of these parameters revealed no statistically significant difference between asymptomatic, symptomatic, and post-surgical patients. C₇ sagittal vertical axis (SVA) correlated with the C₂C₇ Cobb angle (r=0.7) in all groups. No significant correlation was noted between cervical and spinopelvic parameters in asymptomatic patients. However, C₁C₂ Cobb angle correlated significantly with pelvic incidence (PI, r=−0.2), lumbar lordosis (LL, r=0.2), and pelvic tilt (PT, r=−0.2) in cervical symptomatic patients. Irrespective of the patient symptom sub-group (n=420), C₁C₂ Cobb angle correlated with LL (r=0.1) and C₂C₇ Harrison angle correlated with PI and PT (r=0.1).

Conclusions

Our results indicate significant interdependence between the spinopelvic and cervical alignment, especially in cervical symptomatic patients. In addition, strong correlation was found between the C₇ SVA and C₂C₇ Cobb angle. Overall, the results of this study could help to better understand the cervical sagittal alignment and serve as preliminary data for planning surgical reconstruction procedures.

Importance of the Occipitoaxial Angle and Posterior Occipitocervical Angle in Occipitocervical Fusion

OBJECTIVE

To observe the effects of occipitoaxial angle (O-C2 angle, OC2A) and posterior occipitocervical angle (POCA) selection on postoperative clinical efficacy and lower cervical curvature in patients with acute acquired atlantoaxial dislocation after occipitocervical fusion (OCF).

METHODS

A total of 150 healthy subjects without cervical disease (healthy group) were randomly selected based on gender and age. Three spine surgeons measured the OC2A and POCA of the healthy group and averaged the values. A total of 30 patients with an average age of 51.0 years (range, 18-70 years; 16 male and 14 female) with trauma or rheumatoid arthritis (disease group) who underwent occipitocervical fusion (OCF) for atlantoaxial dislocation between January 2012 and June 2016 were reviewed. OC2A, POCA, and cervical spinal angle (CSA) were measured postoperative/soon after surgery and ambulation, and at the final follow-up visit. The preoperative and final follow-up visual analog scale (VAS), Japanese orthopedics association score (JOA), neck disability index (NDI), and dCSA (change of CSA from postoperative/soon after surgery and ambulation to final follow-up) were recorded.

RESULTS

The values of OC2A and POCA in 150 healthy subjects were 14.5° ± 3.7° and 108.2° ± 8.1°, respectively, and the 95% confidence interval (CI) were 7.2°-21.8° and 92.3°-124.0°, respectively. There was a negative correlation between OC2A and POCA (r = -0.386, P < 0.001). There were 18 patients (group one) of ideal OC2A and POCA (both within 95% CI of the healthy group) postoperative/soon after surgery and ambulation with a mean follow-up time of 26.3 ± 20.9 months in disease group. The remaining patients (group two) with a mean follow-up time of 31.3 ± 21.3 months. There was no statistically significant difference in the baseline data as well as pre-operative outcomes, including VAS score, JOA score, and NDI between the two groups. Likewise, the post-operative outcomes in final follow-up, including VAS and JOA score, had no distinct difference in the two groups. However, NDI (11.0 ± 2.9) in group two at the final follow-up was significantly higher than that in group one (7.0 ± 2.3) (P < 0.001). And group two showed statistically greater dCSA (5.9 ± 7.5°) than group one (-2.3° ± 6.2°) (P = 0.003).

CONCLUSIONS

The negative correlation between OC2A and POCA plays an important role in maintaining the biodynamic balance of the occipital-cervical region. OC2A and POCA should be controlled of a normal population in patients with acute acquired atlantoaxial dislocation during OCF, which can further improve the clinical efficacy and prevent loss of lower cervical curvature after surgery.

Effect of Sub-axial Cervical Lateral Mass Screw Fixation on Functional Outcome in Patients with Cervical Spondylotic Myelopathy

Background

The role of laminectomy alone as an etiology of postoperative cervical instability is well known. Cervical sagittal malalignment of the spine has been linked to unfavorable functional outcome, so the effect of restoration of sagittal spinal alignment on functional outcomes and treatment effectiveness has recently gained attention.

Objective

This is a prospective observational study aims to observe the possible relation between cervical sagittal alignment and functional outcomes following sub-axial cervical lateral mass screw fixation in patients with cervical spondylotic myelopathy.

Patients and Methods

Thirty patients were included in this study all suffering from cervical spondylotic mylopathy (CSM) who underwent cervical laminectomy and screw-rod fixation and followed up over 6 months. Functional outcome accessed using Nurick myelopathy score and neck disability index (NDI)?. We also used the Cobb angle method (C₂-C₇) as a parameter for radiographic assessment of the cervical sagittal alignment which was measured preoperatively and postoperatively on lateral neutral views of cervical X-ray.

Results

All the patients underwent cervical laminectomy and fixation in a range of 3-5 levels. Two intraoperative facet fractures and four facet joint violations were observed. All the patients were followed-up for at least 6 months. There were significant improvements of the motor power (88.5%), Nurick score (90%), and NDI (90%) postoperatively. The mean preoperative Cobb angle for all patients was -8.51° ± 14.07° standard deviation (SD) which changed to -10.29 ± 12.43 SD at the end of follow-up.

Conclusion

Combing posterior decompression with lateral mass screw- rod in patients with CSM was effective in improving or at least maintaining cervical alignment with the good functional outcome.

Global spinal deformity from the upper cervical perspective. What is "Abnormal" in the upper cervical spine?

Hypothesis

Reciprocal changes in the upper cervical spine correlate with adult TL deformity modifiers.

Design

This was a retrospective review.

Introduction

The upper cervical spine has remarkable adaptability to wide ranges of thoracolumbar (TL) deformity.

Methods

Patients >18 years with adult spinal deformity (ASD) and complete radiographic data at baseline (BL) and 1 year were identified. Patients were grouped into component types of the Roussouly classification system (Type 1: Pelvic incidence [PI] <45° and lumbar lordosis [LL] apex below L4; Type 2: PI <45° and LL apex above L4; Type 3:45°<PI <65°; and Type 4: PI >65°). Patients were categorized by increasing severity of Schwab modifiers at BL (0, +, and ++) and further grouped by regional malalignment moving cranially (P: pelvic only; LP: lumbopelvic; TL: thoracic and LP; C: subaxial and TL). Analysis of variance and Pearson's r assessed changes in BL upper cervical parameters (C0-2, C0 slope, McGregor's Slope [MGS], and CBVA) across groups.

Results

A total of 343 ASD patients were analyzed. When grouped by BL Schwab and Roussouly, Group P had the lowest BL disability compared to other Groups, while Roussouley Type 1 correlated with higher BL disability compared to Type 2. Moving cranially up the spine, Group P, Group LP, and Group TL did not differ in C0-2 angle, C0 slope, MGS, or CBVA. Group C had a significantly smaller C0-C2, and more negative MGS, C0 slope, and CBVA than noncervical groups. Type 1 trended slightly higher CBVA and MGS than types 2-4, but no differences in cervical lordosis, C0-C2, or C0S were found. MGS (r = -0.131, P = 0.015), CBVA (r = -0.473, P < 0.001), and C0S (r = -0.099, P = 0.042) correlated most strongly with sagittal vertical axis (SVA) compared to other Schwab modifiers. We found SVA > 34 mm predicted a 1 unit (°°) decrease in MGS (odds ratio [OR]: 0.970 [0.948-0.993], P = 0.010), while cervical SVA >51 mm predicted a 1 unit increase in MGS (OR: 1.25 [1.12-1.38], P < 0.001).

Conclusions

Our study suggests that upper cervical alignment remains relatively stable through most broad variations of adult TL deformity. Changes in SVA correlated most with upper cervical changes.

Characteristics of deformity surgery in patients with severe and rigid cervical kyphosis (CK): results of the CSRS-Europe multi-centre study project

INTRODUCTION AND PURPOSE

Little information exists on surgical characteristics, complications and outcomes with corrective surgery for rigid cervical kyphosis (CK). To collate the experience of international experts, the CSRS-Europe initiated an international multi-centre retrospective study.

METHODS

Included were patients at all ages with rigid CK. Surgical and patient specific characteristics, complications and outcomes were studied. Radiographic assessment included global and regional sagittal parameters. Cervical sagittal balance was stratified according to the CSRS-Europe classification of sagittal cervical balance (types A-D).

RESULTS

Eighty-eight patients with average age of 58 years were included. CK etiology was ankylosing spondlitis (n = 34), iatrogenic (n = 25), degenerative (n = 9), syndromatic (n = 6), neuromuscular (n = 4), traumatic (n = 5), and RA (n = 5). Blood loss averaged 957 ml and the osteotomy grade 4.CK-correction and blood loss increased with osteotomy grade (r = 0.4/0.6, p < .01). Patients with different preop sagittal balance types had different approaches, preop deformity parameters and postop alignment changes (e.g. C7-slope, C2-7 SVA, translation). Correction of the regional kyphosis angle (RKA) was average 34° (p < .01). CK-correction was increased in patients with osteoporosis and osteoporotic vertebrae (POV, p = .006). 22% of patients experienced a major long-term complication and 14% needed revision surgery. Patients with complications had larger preop RKA (p = .01), RKA-change (p = .005), and postop increase in distal junctional kyphosis angle (p = .02). The POV-Group more often experienced postop complications (p < .0001) and revision surgery (p = .02). Patients with revision surgery had a larger RKA-change (p = .003) and postop translation (p = .04). 21% of patients had a postop segmental motor deficit and the risk was elevated in the POV-Group (p = .001).

CONCLUSIONS

Preop patient specific, radiographic and surgical variables had a significant bearing on alignment changes, outcomes and complication occurrence in the treatment of rigid CK.

The Effect of Aging on Cervical Parameters in a Normative North American Population

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To investigate age-based changes in cervical alignment parameters in an asymptomatic population.

METHODS

Retrospective review of a prospective study of 118 asymptomatic subjects who underwent biplanar imaging with 3-dimensional capabilities. Demographic and health-related quality of life data was collected prior to imaging. Patients were stratified into 5 age groups: <35 years, 35-44 years, 45-54 years, 55-64 years, and ≥65 years. Radiographic measurements of the cervical spine and spinopelvic parameters were compared between age groups. The normal distribution of parameters was assessed followed by analysis of variance for comparison of variance between age groups.

RESULTS

C2-C7 lordosis, C0-C7 lordosis, and T1 slope demonstrated significant increases with age. C0-C7 lordosis was significantly less in subjects <35 years compared with ≥55 years. Significant differences in T1 slope were identified in patients <35 versus ≥65, 35-44 versus ≥65, and 45-54 versus ≥65 years. T1 slope demonstrated a positive correlation with age. Horizontal gaze parameters did not change linearly with age and mean averages of all age groups were within 10° of one another. Cervical kyphosis was present in approximately half of subjects who were <55 compared with approximately 10% of subjects ≥55 years. Differences in pelvic tilt, pelvic incidence-lumbar lordosis, and C7-S1 sagittal vertical axis were identified with age.

CONCLUSIONS

C0-C7 lordosis, C2-C7 lordosis, and T1 slope demonstrate age-based changes while other cervical and horizontal gaze parameters remain relatively constant with age.

Cervical lordosis in asymptomatic individuals: a meta-analysis

Background

Cervical lordosis has important clinical and surgical implications. Cervical spine curvature is reported with considerable variability in individual studies. The aim of this study was to examine the existence and extent of cervical lordosis in asymptomatic individuals and to evaluate its relationship with age and gender.

Methods

A comprehensive literature search was conducted in several electronic databases. Study selection was based on pre-determined eligibility criteria. Random effects meta-analyses were performed to estimate the proportion of asymptomatic individuals with lordosis and the effect size of cervical lordotic curvature in these individuals which followed metaregression analysis to examine the factors affecting cervical lordosis. Data from 21 studies (15,364 asymptomatic individuals, age 42.30 years [95% confidence interval 36.42, 48.18], 54.2% males) were used in the present study.

Results

In this population, 63.99% [95% confidence interval 44.94, 83.03] individuals possessed lordotic curvature. Degree of lordotic curvature differed by method of measurement; 12.71° [6.59, 18.84] with Cobb C2–C7 method and 18.55° [14.48, 22.63] with posterior tangent method. Lordotic curvature was not significantly different between symptomatic and asymptomatic individuals but was significantly higher in males in comparison with females. Age was not significantly associated with lordotic cervical curvature.

Conclusion

Majority of the asymptomatic individuals possesses lordotic cervical curvature which is higher in males than in females but have no relationship with age or symptoms.

Cervical sagittal balance parameters after single-level anterior cervical discectomy and fusion: Correlations with clinical and functional outcomes

Background:

Normal sagittal cervical alignment has been associated with improved outcome after anterior cervical discectomy and fusion (ACDF).

Objective:

The aim of this study is to identify alterations of cervical sagittal balance parameters after single-level ACDF and assess correlations with postoperative functionality.

Methods:

A retrospective chart review was performed between January 2010 and January 2014 to identify adult patients with no previous cervical spine surgery who underwent ACDF at any one level between C2 and C7 for the single-level degenerative disease. Tumor, infection, and trauma cases were excluded from the study. For the included cases, the following data were recorded preoperatively and 6 months–1 year after surgery: sagittal balance-marker measurements of the C1–C2 angle, C2–C7 angle, C7 slope, segmental angle at the operated level, and sagittal vertical axis (SVA) distance between C2 and C7, as well as the neck disability index and visual analog scale of pain.

Results:

The present study included 47 patients (average age: 51.2 years; range: 28–86 years). A moderate negative correlation between a smaller C2–C7 angle and the presence of right arm pain before treatment was found (P = 0.0281). Postoperatively, functionality scores significantly improved in all patients. C1–C2 angle increased with statistical significance (P = 0.0255). C2–C7 angle, segmental angle, C7 slope, and SVA C2–C7 distance did not change with statistical significance after surgery. C7 slope significantly correlated with overall cervical sagittal balance (P < 0.05).

Conclusions:

Single-level ACDF significantly increases upper cervical lordosis (C1–C2) without significantly changing lower cervical lordosis (C2–C7). The C7 slope is a significant marker of overall cervical sagittal alignment (P < 0.05).

Occipital and external acoustic meatus to axis angle as a predictor of the oropharyngeal space in healthy volunteers: a novel parameter for craniocervical junction alignment

BACKGROUND CONTEXT

The occipito-C2 angle (O-C2a) influences the oropharyngeal space. However, O-C2a has several limitations. There is no normal value of O-C2a because of the wide individual variations, and O-C2a does not reflect translation of the cranium to the axis, another factor influencing the oropharyngeal space in patients with atlantoaxial subluxation.

PURPOSE

The objective of this study was to propose a novel parameter that accounts for craniocervical junction alignment (CJA) and the oropharyngeal space.

STUDY DESIGN

This is a post hoc analysis of craniocervical radiological parameters from another study.

PATIENT SAMPLE

Forty healthy volunteers were included in the study.

OUTCOME MEASURES

Craniocervical measurement parameters included the occipital and external acoustic meatus to axis angle (O-EAa), the C2 tilting angle (C2Ta), O-C2a, and the anterior-posterior distance of the narrowest oropharyngeal airway space (nPAS).

MATERIALS AND METHODS

We collected 40 healthy volunteers' lateral cervical radiographs in neutral, flexion, extension, protrusion, and retraction positions. We measured O-C2a, C2Ta (formed by the inferior end plate of C2 and a line connecting the external acoustic meatus and the midpoint of the inferior end plate of C2 [EA-line]), O-EAa (formed by the McGregor line and the EA-line), and nPAS. We evaluated the inter-rater and intrarater reliability of O-EAa and C2Ta, and the associations between each of the measured parameters.

RESULTS

The inter-rater and intrarater reliabilities of measuring O-EAa and C2Ta were excellent. The neutral position O-EAa values remained in a narrower range (mean±standard deviation, 90.0°±5.0°) than O-C2a (15.6°±6.7°) (Levene test of equality of variances, p=.044). In the linear mixed-effects models, sex, O-C2a, C2Ta, and O-EAa were significantly associated with nPAS. The marginal R² values for the mixed-effect models, which express the variance explained by fixed effects, were 0.605 and 0.632 for the O-C2a and O-EAa models, respectively. In all models, the subaxial alignment (C2-C6a) had no significant association with nPAS.

CONCLUSIONS

The O-EAa may be a useful parameter of CJA with several advantages over O-C2a, including less individual variation, easier visual recognition during surgery, and improved prediction of postoperative nPAS after occipitocervical fusion.

Revision surgery after rod breakage in a patient with occipitocervical fusion: A case report

RATIONALE

Rod breakage after occipitocervical fusion (OCF) has never been described in a patient who has undergone surgery for basilar invagination (BI) and atlantoaxial dislocation (AAD). Here, we present an unusual but significant case of revision surgery to correct this complication.

PATIENT CONCERNS

A 32-year-old female presented with neck pain, unstable leg motion in walking, and also BI with AAD. Her first surgery was planned to correct these conditions and for fusion at the occipital junction (C3-4) using a screw-rod system. At the 31-month follow-up after her first operation, the patient complained of severe neck pain and limitation of motion, suggesting rod breakage.

DIAGNOSES

Rod breakage after occipitocervical fusion for BI and AAD.

INTERVENTIONS

The patient underwent reoperation for replacement of the broken rods, adjustment of the occipitocervical angle, maintenance of the bone graft bed, and fusion.

OUTCOMES

At follow-up, the hardware was found to be in good condition, with no significant loss of cervical lordosis. At the 37-month follow-up after her second operation, the patient was doing better and continuing to recover.

LESSONS

We concluded that nonideal choice of occipitocervical angle may play an important role in rod breakage; however, an inadequate bone graft and poor postoperative fusion may also contribute to implant failure.

Comparison of Cervical Alignment and Clinical Outcomes in Patients with Os Odontoideum versus Non-Os Odontoideum after Atlantoaxial Fixation

OBJECTIVE

The purpose of this study was to compare the effect of atlantoaxial fixation on cervical alignment and clinical outcomes in patients with os odontoideum (OO) versus non-os odontoideum (non-OO).

METHODS

A total of 119 patients who underwent atlantoaxial fixation for instability were identified between January 1998 and January 2014. Inclusion criteria included age more than 21 years and diagnosis of OO and non-OO. There were 22 OO patients, and 20 non-OO patients. Measuring the Oc-C1 Cobb angle, C1-2 Cobb angle, C2-7 Cobb angle, and C2-7 sagittal vertical axis (SVA) was assessed. Clinical outcome was assessment of suboccipital pain was determined using a visual analogue scale (VAS), and Japanese Orthopedic Association (JOA) scores were obtained in all patients pre- and postoperatively.

RESULTS

The preoperative C1-2 angle in the OO group (26.02°±10.53°) was significantly higher than the non-OO group (p=0.04). After C1-2 fixation, the OO group had significantly higher kyphotic change in the C1-2 angle (ΔC1-2) (3.2°±7.3° [OO] vs. -1.46°±7.21° [non-OO]) (p=0.04), and higher decrease in postoperative C2-7 SVA (ΔC2-7 SVA) (5.64±11.56 mm [OO] vs. -0.51± 6.57 mm [non-OO]) (p=0.04). Both groups showed improvements in the health related quality of life (HRQOL) after surgery based on the VAS and JOA score (p<0.001).

CONCLUSION

After fixation, kyphotic angular change in atlantoaxial joint and decrease C2-7 SVA were marked in the OO group. Both the OO and non-OO groups improved in neurological function and outcome after surgery.

Long-Term Influence of C1-C2 Pedicle Screw Fixation on Occipitoatlantal Angle and Subaxial Cervical Spine in the Pediatric Population

OBJECTIVE

The goal of this study was to evaluate the impact of C1-C2 pedicle screw fixation on the occipitoatlantal angle and subaxial cervical spine for a pediatric population, and the clinical efficacy and adjacent-segment degeneration after C1-C2 pedicle screw fixation with a minimum of 2 years of follow-up.

METHODS

Twenty-two pediatric patients with atlantoaxial dislocation who were enrolled in this study underwent atlantoaxial pedicle screw fixation. The correlation between C0-C1, C2-C7, and C1-C2 pre- and postoperative sagittal angles was assessed using plain radiographs, and adjacent-segment degeneration (ASD) and JOA scores (Japanese Orthopaedic Association scores) were evaluated after atlantoaxial pedicle screw fixation.

RESULTS

The C1-C2 angle increased from 16.1 ± 13.37 to 28.1 ± 5.1° (p < 0.01). The pre- and postoperative C1-C2 angles were negatively correlated with the pre- and postoperative C0-C1 and C2-C7 angles, respectively. In accordance with the optimal atlantoaxial fusion angle (25-30°) obtained from the literature, postoperative JOA scores were greater in the groups with angles of more than 30° and less than 25°, although the difference in ASD was not statistically significant. Postoperative JOA scores were not relevant to the postoperative C1-C2 angle; however, there was a positive correlation between JOA improvement rate and the change of the C1-C2 angle postoperatively.

CONCLUSION

Atlantoaxial pedicle screw fixation can be used easily to reduce atlantoaxial dislocation in the pediatric population; however, outside the range of the optimal atlantoaxial fusion angle it can change the occipitoatlantal angle and subaxial alignment, which induces ASD and influences the clinical efficacy. It is necessary to achieve an optimal atlantoaxial angle when using atlantoaxial pedicle screw fixation.

Osteotomies in ankylosing spondylitis: where, how many, and how much?

INTRODUCTION

This article presents the current concepts of correction of spinal deformity in ankylosing spondylitis (AS) patients. Untreated AS can be a debilitating disease. In a few patients, disease progression results in severe spinal deformity affecting not only the thoracolumbar, but also the cervical spine. Surgery for correction in AS patients has a long history. With the advent of modern instrumentation, standardization of surgical and anesthesiologic techniques, surgical safety and corrective results could be improved and experiences from lumbar osteotomies could be transferred to the cervical spine.

METHODS

This article presents the current concepts of correction of spinal deformity in AS patients. In particular, questions regarding the localization and number of osteotomies, the optimal surgical target angle as well as planning and prediction of postoperative alignment are discussed.

RESULTS

Insight into recent technical developments, current challenges with correction and geometric analysis of center of rotation (COR) in cervical 3-column osteotomies (3CO) will be presented.

CONCLUSION

The article should encourage readers to improve surgical correction efficacy and provide a better understanding of correction geometry in 3CO for thoracolumbar and cervical spinal deformities.

Surgical overreduction and hyperlordotic fusion of C1-C2 joint are associated with cervical sagittal malalignment

INTRODUCTION

Previous studies have shown that hyperlordotic C1-C2 fusion was related to postoperative subaxial kyphosis. However, most of the patients in these studies were complicated with rheumatoid arthritis (RA). Moreover, no studies have specifically evaluated the relationship between C1-C2 fusion angle and cervical sagittal vertical axis (cSVA), T1 slope or cranial tilt (CRT) after posterior C1-C2 fusion. This study aimed to investigate the cervical sagittal alignment in non-RA patients following posterior C1-C2 fusion and the correlation between C1-C2 fusion angle and postoperative cervical sagittal alignment.

MATERIALS AND METHODS

From August 2004 to December 2015, twenty-eight consecutive patients with an average age of 39.2 years (range 6-70 years) who underwent posterior C1-C2 fusion from a single institution were enrolled. The mean follow-up period was 30.7 months (range 12-77 months). Angles of Oc-C1, C1-C2, C2-C3 and C2-C7, cSVA, T1 slope and CRT were measured in lateral cervical radiographs in neutral position before surgery and at the final follow-up.

RESULTS

C1-C2 angle significantly increased from 13.6° ± 12.4° to 22.0° ± 8.1° at the final follow-up (P < 0.001). A significant decrease was found both in Oc-C1 and C2-C7 angles from pre-operation to the final follow-up (P < 0.001 and P = 0.011, respectively). Moreover, cSVA and CRT dramatically increased from pre-operation to the final follow-up (P < 0.001). C1-C2 fusion angle was significantly associated with Oc-C1, C2-C7 angle, cSVA and CRT at the final follow-up. A significant correlation was also observed between postoperative change of C1-C2 angle and that of Oc-C1, C2-C7 angle, cSVA and CRT.

CONCLUSIONS

Apart from decreased subaxial lordosis, posterior C1-C2 fusion in hyperextension may also lead to kyphotic change of atlanto-occipital alignment and increased tilting forward of the cervical spine. Therefore, intraoperative overreduction of C1-C2 angle and hyperlordotic C1-C2 fusion should be avoided to maintain the physiologic cervical sagittal alignment.

Postoperative Increase in Occiput-C2 Angle Negatively Impacts Subaxial Lordosis after Occipito-Upper Cervical Posterior Fusion Surgery

STUDY DESIGN

Retrospective case series.

PURPOSE

To elucidate the impact of postoperative occiput-C2 (O-C2) angle change on subaxial cervical alignment.

OVERVIEW OF LITERATURE

In the case of occipito-upper cervical fixation surgery, it is recommended that the O-C2 angle should be set larger than the preoperative value postoperatively.

METHODS

The present study included 17 patients who underwent occipito-upper cervical spine (above C4) posterior fixation surgery for atlantoaxial subluxation of various etiologies. Plain lateral cervical radiographs in a neutral position at standing were obtained and the O-C2 angle and subaxial lordosis angle (the angle between the endplates of the lowest instrumented vertebra (LIV) and C7 vertebrae) were measured preoperatively and postoperatively soon after surgery and ambulation and at the final follow-up visit.

RESULTS

There was a significant negative correlation between the average postoperative alteration of O-C2 angle (DO-C2) and the average postoperative alteration of subaxial lordosis angle (Dsubaxial lordosis angle) (r=-0.47, p=0.03).

CONCLUSIONS

There was a negative correlation between DO-C2 and Dsubaxial lordosis angles. This suggests that decrease of mid-to lower-cervical lordosis acts as a compensatory mechanism for lordotic correction between the occiput and C2. In occipito-cervical fusion surgery, care must be taken to avoid excessive O-C2 angle correction because it might induce mid-to-lower cervical compensatory decrease of lordosis.

Biomechanical Comparison of Modified TARP Technique Versus Modified Goel Technique for the Treatment of Basilar Invagination: A Finite Element Analysis

STUDY DESIGN

A finite element analysis.

OBJECTIVE

The aim of this study was to determine the biomechanical differences between atlantoaxial fusion cage combined with transoral atlantoaxial reduction plate fixation (TARP + Cage, modified TARP technique) and that combined with C1 lateral mass screw and C2 pedicle screw fixation (C1LS + C2PS + Cage, modified Goel technique) in the treatment of basilar invagination (BI) by finite element analysis.

SUMMARY OF BACKGROUND DATA

Clinical studies have shown that transoral anterior atlantoaxial release followed by TARP fixation can achieve reduction, decompression, fixation, and fusion of C1-C2 through a transoral-only approach. Although cage has been used to reduce the BI through posterior approach, there are no studies referred to the cage combined with TARP for C1-C2 fusion.

METHODS

A finite element model was used to investigate and compare the stability between TARP + Cage fixation and C1LS + C2PS + Cage fixation in the treatment of BI. Vertical load of 40  N was applied on the C0, to simulate head weight, and 1.5  Nm torque was applied to the C0 to simulate flexion, extension, lateral bending, and rotation.

RESULTS

In comparison with the C1LS + C2PS + Cage model, the TARP + Cage model reduced the ROM by 44.7%, 30.0%, and 10.5% in extension, lateral bending, and axial rotation, while the TARP + Cage model increased the ROM by 30.0% in flexion, and the TARP + Cage model also led to lower screw stress in all motions with one exception (anterior C2PS stress in extension).

CONCLUSION

Our results indicate that the TARP + Cage fixation may offer higher stability to C1LS + C2PS + Cage in extension, lateral bending, and axial rotation but lower stability in flexion. Compared with modified Goel technique, the modified TARP technique not only has the capability of transferring the load and distributing the stress but also can provide neural decompression, stabilization and fusion, and restore C1-C2 normal fusion angle.

LEVEL OF EVIDENCE

N/A.

Age-Related and Degenerative Changes in the Osseous Anatomy, Alignment, and Range of Motion of the Cervical Spine: A Comparative Study of Radiographic Data From 1016 Patients With Cervical Spondylotic Myelopathy and 1230 Asymptomatic Subjects

STUDY DESIGN

A prospective comparative study.

OBJECTIVE

This study aimed to establish cervical spine morphometry, alignment, and range of motion (ROM) and to clarify the impact of these age-related and degenerative changes.

SUMMARY OF BACKGROUND DATA

There are no studies that have evaluated differences in the results of cervical spine radiographs between a large series of cervical spondylotic myelopathy (CSM) patients and healthy subjects.

METHODS

We enrolled 1016 consecutive CSM patients who underwent laminoplasty. CSM patients were also divided based on each decade of life between the fourth and ninth decades. We also enrolled a total of 1230 healthy volunteers as asymptomatic subjects in this study. There were at least 100 men and 100 women in each decade of life between the third and eighth decades. Cervical sagittal alignment on neutral and flexion-extension views was measured by the Cobb method at C2-7. ROM was assessed by measuring the difference in alignment between flexion and extension.

RESULTS

Cervical lordosis in the neutral position increased gradually with age in both groups. CSM patients showed significantly smaller lordotic angles compared with those shown by asymptomatic subjects within each decade. The total ROM decreased with increasing age in both groups. The total ROM of females was larger than males. The ROM of CSM patients was significantly smaller than asymptomatic subjects. The flexion ROM did not change with aging in either group. There was no significant difference in the flexion ROM between males and females in the two groups. However, the extension ROM decreased gradually in both groups. The extension ROM of CSM patients was significantly smaller than asymptomatic subjects.

CONCLUSION

Age-related and degenerative changes in the cervical spine, alignment, and ROM in each decade of life were established between CSM patients and asymptomatic subjects.

Association between preoperative cervical sagittal deformity and inferior outcomes at 2-year follow-up in patients with adult thoracolumbar deformity: analysis of 182 patients

OBJECT

A high prevalence of cervical deformity (CD) has been identified among adult patients with thoracolumbar spinal deformity undergoing surgical treatment. The clinical impact of this is uncertain. This study aimed to quantify the differences in patient-reported outcomes among patients with adult spinal deformity (ASD) based on presence of CD prior to treatment.

METHODS

A retrospective review was conducted of a multicenter prospective database of patients with ASD who underwent surgical treatment with 2-year follow-up. Patients were grouped by the presence of preoperative CD: 1) cervical positive sagittal malalignment (CPSM) C2–7 sagittal vertical axis ≥ 4 cm; 2) cervical kyphosis (CK) C2–7 angle > 0; 3) CPSM and CK (BOTH); and 4) no baseline CD (NONE). Health-related quality of life (HRQOL) scores included the Physical Component Summary and Mental Component Summary (PCS and MCS) scores of the 36-Item Short Form Health Survey (SF-36), Oswestry Disability Index (ODI), Scoliosis Research Society-22 questionnaire (SRS-22), and minimum clinically important difference (MCID) of these scores at 2 years. Standard radiographic measurements were conducted for cervical, thoracic, and thoracolumbar parameters.

RESULTS

One hundred eighty-two patients were included in this study: CPSM, 45; CK, 37; BOTH, 16; and NONE, 84. Patients with preoperative CD and those without had similar baseline thoracolumbar radiographic measurements and similar correction rates at 2 years. Patients with and without preoperative CD had similar baseline HRQOL and on average both groups experienced some HRQOL improvement. However, those with preoperative CPSM had significantly worse postoperative ODI, PCS, SRS-22 Activity, SRS-22 Appearance, SRS-22 Pain, SRS-22 Satisfaction, and SRS-22 Total score, and were less likely to meet MCID for ODI, PCS, SRS-22 Activity, and SRS-22 Pain scores with the following ORs and 95% CIs: ODI 0.19 (0.07–0.58), PCS 0.17 (0.06–0.47), SRS-22 Activity 0.23 (0.09–0.62), SRS-22 Pain 0.20 (0.08–0.53), and SRS-22 Appearance 0.34 (0.12–0.94). Preoperative CK did not have an effect on outcomes. Interestingly, despite correction of the thoracolumbar deformity, 53.3% and 51.4% of patients had persistent CPSM and persistent CK, respectively.

CONCLUSIONS

Patients with thoracolumbar deformity without preoperative CD are likely to have greater improvements in HRQOL after surgery than patients with concomitant preoperative CD. Cervical positive sagittal alignment in adult patients with thoracolumbar deformity is strongly associated with inferior outcomes and failure to reach MCID at 2-year follow-up despite having similar baseline HRQOL to patients without CD. This was the first study to assess the impact of concomitant preoperative cervical malalignment in adult patients with thoracolumbar deformity. These results can help surgeons educate patients at risk for inferior outcomes and direct future research to identify an etiology and improve patient outcomes. Investigation into the etiology of the baseline cervical malalignment may be warranted in patients who present with thoracolumbar deformity.