Factors determining cervical spine sagittal balance in asymptomatic adults: correlation with spinopelvic balance and thoracic inlet alignment

Is there a connection between spine alignment, chest mobility, shoulder joint and respiratory parameters of patients with ankylosing spondylitis?

INTRODUCTION

Ankylosing spondylitis is chronic progressive disease, which decrease functions of musculoskeletal system including chest area. Those changes influences respiratory mechanics, worsen conditions of proper ventilation of lungs.

OBJECTIVES

Rating of functional and respiratory parameters and dependence between them at patients with ankylosing spondylitis.

MATERIALS & METHODS

The study included 45 patients with diagnosed ankylosing spondylitis. Chest and upper limbs mobility, resting spinal curvature alignment were assessed, and respiratory parameters were measured in a plethysmographic chamber JAGGER MasterScreen Body.

RESULTS

Ankylosing spondylitis patients had lower respiratory parameters especially sReff, and FRC. Restriction of chest and upper limbs mobility was also demonstrated. Forward head extension was observed based on the occipital wall test. Correlations between functional parameters and correlations between functional and respiratory parameters were shown, in particular MIP, MEP, sReff, Rtot, TLC, ERV.

CONCLUSIONS

The study confirmed a decrease in functional and respiratory parameters in the examined patients with ankylosing spondylitis compared to the applicable standards. A significant relationship was found between functional parameters in the upper body and respiratory parameters, which worsen with increasing thoracic dysfunction. The obtained results indicate the directions of therapy that should be taken into account to improve respiratory parameters and reduce respiratory dysfunction in these patients. Chest-focused physiotherapy appears to be an important element in improving function in patients with ankylosing spondylitis.

Normal spinopelvic parameters and correlation analysis in 217 asymptomatic children

BACKGROUND

Understanding spinal sagittal balance is crucial for assessing and treating spinal deformities in pediatric populations.

OBJECTIVE

The aim of the present observational study is to examine the parameters of sagittal alignment of the regional spine and spinopelvic region in asymptomatic pediatric populations and the characteristics of these parameters with age and sex.

METHODS

We enrolled 217 participants, consisting of 112 males (51.6%) and 105 females (48.4%), aged between 4 and 15 years, with an average age of 12.19 years. Pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, thoracic kyphosis, T1 slope, C7 slope, cervical sagittal vertical axis, and C2-7 Cobb angle were measured. Three spine surgeons conducted radiographic measurements utilizing the PACS software. The measurement reliability was assessed through ICCs.

RESULTS

Our results show significant age-related changes in pelvic tilt and cervical sagittal vertical axis, with notable gender differences in pelvic tilt, lumbar lordosis, and thoracic kyphosis. Girls have larger PT, boys have larger cSVA. PI, PT, and cSVA also differ among different age groups. Correlation analysis shows that a series of relationships that align with adult population patterns between pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, and thoracic kyphosis.

CONCLUSION

Significant variations in PT and cSVA across diverse age cohorts highlights notable disparities in the distribution of PT and cSVA values within the pediatric population. Gender-based differences in PT, LL, and TK and correlation in spinopelvic parameter could enhances our understanding of compensatory mechanisms.

Utilizing machine learning to predict post-treatment outcomes in chronic non-specific neck pain patients undergoing cervical extension traction

This study explored the application of machine learning in predicting post-treatment outcomes for chronic neck pain patients undergoing a multimodal program featuring cervical extension traction (CET). Pre-treatment demographic and clinical variables were used to develop predictive models capable of anticipating modifications in cervical lordotic angle (CLA), pain and disability of 570 patients treated between 2014 and 2020. Linear regression models used pre-treatment variables of age, body mass index, CLA, anterior head translation, disability index, pain score, treatment frequency, duration and compliance. These models used the sci-kit-learn machine learning library within Python for implementing linear regression algorithms. The linear regression models demonstrated high precision and accuracy, and effectively explained 30-55% of the variability in post-treatment outcomes, the highest for the CLA. This pioneering study integrates machine learning into spinal rehabilitation. The developed models offer valuable information to customize interventions, set realistic expectations, and optimize treatment strategies based on individual patient characteristics as treated conservatively with rehabilitation programs using CET as part of multimodal care.

Sagittal Full-Spine vs. Sectional Cervical Lateral Radiographs: Are the Measurements of Cervical Alignment Interchangeable?

(1) Background: This study assessed the relationship between cervical spine parameters taken on standing full-spine lateral radiographic images compared to sectional lateral cervical radiographs. (2) Methods: Full-spine (FS) and sectional lateral cervical (LC) radiographs from four spine treatment facilities across the USA retrospectively provided data collected on 220 persons to assess the comparison of three sagittal cervical radiographic measurements between the two views. The measures included cervical lordosis using the absolute rotation angle from C2-C7, sagittal cervical translation of C2-C7, and atlas plane angle to horizontal. Linear correlation and R2 models were used for statistical comparison of the measures for the two views. (3) Results: The mean values of the three measurements were statistically different from each other: C2-C7 translation (FS = 19.84 ± 11.98 vs. LC = 21.18 ± 11.8), C2-C7 lordosis (FS = -15.3 ± 14.63 vs. LC = -18.32 ± 13.16), and atlas plane (FS = -19.99 ± 8.88 vs. LC = -22.56 ± 8.93), where all values were p < 0.001. Weak-to-moderate-to-strong correlations existed between the full-spine and sectional lateral cervical radiographic variables. The R2 values varied based on the measurement were R2 = 0.768 (p < 0.001) for sagittal cervical translation of C2-C7 (strong), R2 = 0.613 (p < 0.001) for the absolute rotation angle C2-C7 (moderate), and R2 = 0.406 (p < 0.001) for the atlas plane line (weak). Though a linear correlation was identified, there were consistent intra-person differences between the measurements on the full spine versus sectional lateral cervical radiographic views, where the full-spine view consistently underestimated the magnitude of the variables. (4) Conclusion: Key sagittal cervical radiographic measurements on the full spine versus sectional lateral cervical radiographic views show striking intra-person differences. The findings of this study confirm that full spine versus sectional lateral cervical radiographic views provide different biomechanical magnitudes of cervical sagittal alignment, and caution should be exercised by health care providers as these are not interchangeable. We recommend the LC view for measurement of cervical sagittal alignment variables.

Capturing the cervical spine shape: Angular measurements versus geometric morphometric methods

The cervical spine manifests a wide shape variation. However, the traditional methods to evaluate the cervical spine curve were never tested against its actual shape. The study's main aim was to determine whether the shape classification of the cervical spine, based on traditional angular measurements, coincides with each other and with the shape captured by the 2D landmark-based geometric morphometric method. The study's second aim was to reveal the associations between the cervical spine shape and the demographic parameters, the head's position, and the spine's sagittal balance. CT scans of the cervical spine of 163 individuals were evaluated to achieve these goals. The shape was assessed by measuring the C2-C7 Cobb angle (CA), the C2-C7 posterior tangent angle (PTA), the curvedness of the arch, and by a 2D landmark-based geometric morphometric method. The position of the head and the sagittal balance of the spine were evaluated by measuring the foramen magnum-C2 Cobb angle (FMCA) and the T1 slope angle (T1SA), respectively. Based on the size of the angle measured, each individual was classified into one of the three cervical 'shape groups' (lordotic, straight, and kyphotic). We found that cervical lordosis was the dominant shape regardless of the measuring methods utilized (46.6%-54.6%), followed by straight neck (28.2%-30.1%), and kyphosis (15.3%-25.2%); however, about a third of the 163 individuals were classified into a different shape group using the CA and PTA methods. The cervical spine angle was sex-independent and age-dependent. The T1SA was significantly correlated with CA and PTA (r = 0.640 and r = 0.585, respectively; p < 0.001). In conclusion, the cervical spine shape evaluation is method-dependent and varies with age.

Usefulness of the preoperative thoracic inlet angle in comparison to the T1 slope for predicting cervical kyphosis after laminoplasty

PURPOSE

Thoracic inlet angle (TIA) is a sagittal radiographic parameter with a constant value regardless of posture and is significantly correlated with the sagittal balance of the cervical spine. However, the practical use of TIA has not been studied. This study aimed to investigate the usefulness of the preoperative TIA for predicting the development of kyphotic deformity after cervical laminoplasty in comparison to the preoperative T1 slope (T1S).

METHODS

A total of 98 patients who underwent cervical laminoplasty without preoperative kyphotic alignment were included (mean age, 73.7 years; 41.8% female). Radiography was evaluated before surgery and at the 2-year follow-up examination. The cervical sagittal parameters were measured on standing radiographs, and the TIA was measured on T2-weighted MRI in a supine position. Cervical alignment with a C2-C7 angle of ≥ 0° was defined as lordosis, and that with an angle of < 0° was defined as kyphosis.

RESULTS

Postoperative kyphosis occurred in 11 patients (11.2%). Preoperatively, the kyphosis group showed significantly lower values in the T1S (23.5° vs. 30.3°, p = 0.034) and TIA (76.1° vs. 81.8°, p = 0.042). We performed ROC curve analysis to clarify the impact of the preoperative TIA and T1S on kyphotic deformity after laminoplasty. The optimal cutoff angles for TIA and T1S were 68° and 19°, respectively, with similar diagnostic accuracy.

CONCLUSION

This study demonstrated the clinical utility of the preoperative TIA for predicting the risk of postoperative kyphotic deformity after cervical laminoplasty. These findings suggest the importance of the preoperative assessment of thoracic inlet alignment in cervical spine surgery.

Predicting cervico-thoraco-lumbar vertebra positions from cutaneous markers: Combining local frame and postural predictors improves robustness to posture

Predictions of vertebra positions from external data are required in many fields like motion analysis or for clinical applications. Existing predictions mainly cover the thoraco-lumbar spine, in one posture. The objective of this study was to develop a method offering robust vertebra position predictions in different postures for the whole spine, in the sagittal plane. EOS radiographs were taken in three postures: slouched, erect, and subject's usual sitting posture, using 21 healthy participants pre-equipped with opaque cutaneous markers. Local curvilinear Frenet frames were built on a spline fitted to spinous processes' cutaneous markers. Vertebra positions were expressed as polar coordinates in these frames, defining an angle (α) and distance (d). Multilinear regressions were fitted to explain α and d from anthropometric predictors and predictors presumed to be linked to spinal posture, the predictors' effects being considered both locally and remotely. Anthropometric predictors were the main predictors for d distances, and postural predictors for α angles, with postural predictors still showing a marked influence on d distances for the cervical spine. Vertebra positions were then predicted by cross-validation. The average RMSE on vertebra positions was 11.0 ± 3.7 mm across the entire spine, 13.4 ± 4.1 mm across the cervical spine and 10.1 ± 3.1 mm across the thoraco-lumbar spine for all participants and postures, performances similar to previous models designed for a single posture. Our simple geometrical and statistical model thus appears promising for predicting vertebra positions from external data in several spinal postures and for the whole spine.

Optimizing Surgical Strategy for Cervical Spinal Deformity: Global Alignment and Surgical Targets

Cervical spinal deformity (CSD) is a complex condition characterized by abnormal curvature and cervical spine alignment. It can lead to a multitude of symptoms, including chronic pain, neurological deficits, and functional impairments, severely impacting an individual's health-related quality of life (HRQoL). Surgical intervention is often necessary to address the deformity and alleviate symptoms, but optimal surgical strategies remain a topic of ongoing research and debate. This narrative review aims to provide an in-depth overview of the surgical management of CSD, focusing on optimizing patient outcomes and enhancing readers' understanding of the complexities involved. We begin by discussing the importance of preoperative assessment, including comprehensive radiographic evaluation and careful consideration of the global spinal alignment. The relationship between the cervical spine and the reciprocal changes that occur are explored to guide surgeons in their decision-making process. Furthermore, we delve into the selection of fusion levels, emphasizing the significance of identifying the primary driver of deformity. We review the current literature on optimal alignment targets and strategies to optimize surgical planning. By providing a comprehensive analysis of the surgical management of CSD, this review aims to enhance the readers' knowledge and assist surgeons in making informed decisions when planning and executing surgical interventions. Understanding the intricacies of CSD correction and the latest advancements in the field can ultimately improve patient outcomes and enhance HRQoL for individuals suffering from this challenging condition.

Health-related quality of life 2 years after pedicle subtraction osteotomy for sagittal imbalance: a single-center experience of 65 patients

PURPOSE

Pedicle subtraction osteotomy (PSO) as an invasive procedure with high reoperation and complication rates in an often elderly population has often been questioned. The purpose of our study was to evaluate the impact of PSO for sagittal imbalance (SI) on patient-reported outcomes including self-reported satisfaction and health-related quality of life 2 years postoperatively.

METHODS

Consecutive patients who underwent correction of their spinal deformity by thoracolumbar PSO were assessed using self-reporting questionnaires 2 years postoperatively. Outcome was measured by visual analogue scale (VAS) for back and leg pain, Oswestry Disability Index (ODI), and EQ-5D scores. Additionally, a Patient Satisfaction Index (PSI) rated in four grades (A: very satisfied to D: not satisfied), walking range, and the Timed Up and Go (TUG) Test were evaluated.

RESULTS

Sixty-five patients were included, and each parameter was assessed preoperatively and 24 months postoperatively. The intervention led to significant improvements in back pain (8.1 ± 1.2 vs. 2.9 ± 1.9; p < 0.001), as well as ODI scores (57.7 ± 13.9 vs. 32.6 ± 18.9; p < 0.001), walking range (589 ± 1676 m vs. 3265 ± 3405 m; p < 0.001), and TUG (19.2 s vs. 9.7 s; p < 0.05). 90.7% of patients (n = 59/65) reported a PSI grade "A" or "B" 24 months postoperatively.

CONCLUSION

Patient satisfaction 24 months after PSO for SI is high. Quality of life improved significantly by restoring sagittal balance.

Sagittal spinal alignment varies with an individual's race: results of the multi-ethnic alignment normative study (MEANS)

PURPOSE

Assess normative values of sagittal spinal and lower extremity alignment in asymptomatic volunteers of three difference races.

METHODS

Asymptomatic volunteers between the ages of 18-80 years were enrolled prospectively and then analyzed retrospectively from six different centers. Volunteers included reported no significant neck or back pain, nor any known spinal disorder(s). All volunteers underwent a standing full-body or full-spine low dose stereoradiograph. Volunteers were grouped into three main races; Asian (A), Arabo-Bèrbère (B), and Caucasian (C). The Asian volunteers included in this study were from Japan and Singapore.

RESULTS

There were statistical differences in the Age, ODI, and BMI of the volunteers from the three different races. Asian volunteers had the lowest age (A: 36.7, B: 45.5, C: 42.0) and BMI (A: 22.1, B: 27.1, C: 27.3). Pelvic morphology including pelvic incidence (A: 51.0, B: 52.0, C: 52.5, p = 0.37), pelvic tilt (A: 11.9, B: 12.3, C: 12.9, p = 0.44), and sacral slope (A: 39.1, B: 39.7, C: 39.6, p = 0.77) were similar amongst the 3 races. Regional spinal alignment was different between the groups. Thoracic Kyphosis (A: 32.9, B: 43.3, C: 40.0, p < 0.0001) and Lumbar lordosis (A: - 54.2, B: - 60.4, C: - 59.6, p < 0.0001) were lower in Asians compared to Caucasian and Arabo-Bèrbère volunteers despite having similar pelvic incidence.

CONCLUSION

Volunteers in the Asian group had lower lumbar lordosis and thoracic kyphosis when compared to the Arabo-Bèrbère and Caucasian groups while all groups had similar pelvic morphology. Thoracic Kyphosis had no correlation with Pelvic Incidence, while Lumbar Lordosis correlated well with both Thoracic Kyphosis and Pelvic Incidence. Thoracic kyphosis may be an independent variable in establishing adequate lumbar lordosis and varies based on an individual's race.

Positive Outcomes Following Cervical Acceleration-Deceleration (CAD) Injury Using Chiropractic BioPhysics® Methods: A Pre-Auto Injury and Post-Auto Injury Case Series

This series illustrates how rear-end impact motor vehicle collisions (MVCs) alter the cervical spine's alignment and demonstrates therapeutic use of cervical extension traction to improve lordotic alignment and other outcomes. This is a retrospective reporting of 7 adult patients (4 males and 3 females, 28-42 years) treated for cervical hypolordosis. These subjects received Chiropractic BioPhysics® (CBP®) rehabilitation and then were involved in a rear-end MVC. All cases had radiographic assessment that quantified the buckling of the cervical spine, presumably resulting directly from the CAD trauma. After an average of 3 years and 9 months (range: 1-7.6 years) following their initial program of care, the 7 patients sought care for a second time after the MVC. At this time, compared with their previously recorded post-treatment spine radiographs, there was an average 18.7° (range: 7.6-35.4°) reduction in cervical lordosis, a 9.2 mm (range: 3.6-19.8 mm) increase in anterior head translation (AHT), an 11.3° (range: 0.2-19.9°) decrease in the atlas plane line (APL), as well as a 35.7% (range: 22-52%) average neck disability index score (NDI) measured after the MVC. After the crash, a second round of CBP rehabilitation was administered, resulting in an average 15.1° improvement in cervical lordosis, 10.9 mm reduction in AHT, 10.4° increase in APL, and a 23.7% drop in NDI after an average of 35 treatments over 9 weeks. Treatment was universally successful, as an average 80% re-establishment of the lordosis toward its pre-injury state was found. There were no adverse events reported. This case series demonstrates that motor vehicle collisions may alter the alignment of the cervical spine. Rehabilitation of the cervical curve using extension traction improved the patients' initial pre-crash alignments toward their pre-injury alignments and was likely responsible for improvement in the patients' conditions. Clinical trials are needed to confirm these findings.

Spinopelvic Alignment: Importance in Spinal Pathologies and Realignment Strategies

Sagittal spinal malalignment can lead to pain, decreased function, dynamic imbalance, and compromise of patient-reported health status. The goal of reconstructive spine surgery is to restore spinal alignment parameters, and an understanding of appropriate patient-specific alignment is important for surgical planning and approaches. Radiographic spinopelvic parameters are strongly correlated with pain and function. The relationship between spinopelvic parameters and disability in adult spinal deformity patients is well-established, and optimal correction of sagittal alignment results in improved outcomes regarding patient health status and mechanical complications of surgery.

Comparison of Cervical Sagittal Parameters Between Radiographs and Magnetic Resonance Images in Patients With Cervical Spondylotic Myelopathy

STUDY DESIGN

Observational study.

OBJECTIVE

As an important consideration of surgery, cervical sagittal balance is believed to be better assessed using standing radiograph than supine magnetic resonance imaging (MRI). However, few studies have researched this. Our study aimed to observe the correlations and differences in cervical sagittal parameters between radiograph and MRI in patients with cervical spondylotic myelopathy (CSM), and evaluate whether the change of position affects them.

METHODS

We analyzed 84 patients, measuring Cobb angle (CA), T1 slope (T1S), neck tilt (NT), and thoracic inlet angle (TIA). Inter- and intra-parameter analyses were performed to identify any difference between standing radiograph and supine MRI. Statistical correlations and differences between the parameters were compared.

RESULTS

There were excellent inter-observer agreement for each parameter (interclass correlation coefficient >.75), and significant differences were observed in each parameter between radiograph and magnetic resonance imaging (P < .05). Strong correlations were noted between the same parameters in radiograph and MRI. Cobb angle, T1S, and neck tilt were significantly correlated with thoracic inlet angle on both radiograph and MRI, and CA was significantly correlated with T1S on both radiograph and MRI (r: -1.0 to -.5 or .5 to 1.0).

CONCLUSION

Supine MRI obviously underestimated the value of CA, T1S, and TIA. Therefore, standing cervical radiographs should be obtained in CSM patients to assess and determine surgical strategy, not only supine MRI. Moreover, we observed that NT and TIA were not constant morphological parameters.

Effect of T1 Slope on Disappearance of Cervical Lordosis after Posterior Cervical Double-Door Laminoplasty Based on Medical Informatics

Cervical sagittal balance plays a pivotal role in spine surgeries as it has a significant impact on the clinical outcomes in cervical spine surgery. Image processing techniques have significantly improved the accuracy and precision of cervical surgical techniques. This study aims to investigate the effects of T1 slope (T1s) on the disappearance of cervical lordosis after posterior cervical double-door laminoplasty using medical informatics and radiographic measures. To do so, we determined and measured the loss of T1s and cervical lordosis during the postoperative follow-up period in patients with double-door posterior cervical laminoplasty. Patients (n = 40) who underwent posterior cervical double-door laminoplasty participated in this study. For all patients, the difference between the preoperative T1s (angle between the upper edge of T1 and the horizontal line) and preoperative and postoperative cervical lordosis (Cobb method) was estimated, and the linear relationship between the two was statistically analyzed to observe the influence of preoperative T1s on postoperative cervical lordosis disappearance. The average preoperative T1s was 23.54°, and the average preoperative cervical lordosis angle was 8.50°. After 1-20 months of follow-up (mean = 9.53 months), the average postoperative cervical lordosis was 8.50°, and the average loss of cervical lordosis was 0.22°. Twenty cases had different degrees of lordosis angle loss after the operation, with an average loss of 9.31°. All patients were divided into groups A and B, according to a mean value of T1s = 23.54°, of which T1S > 23.54° was group A and T1s < 23.54 was group B. Cervical lordosis was quantified by the C2-C7 Cobb angle. The Cobb angle difference of cervical lordosis was measured before and after the operation, and its correlation with preoperative T1s was assessed. The preoperative Cobb angle and cervical curvature changes in the two groups were statistically compared, and the difference between the two groups was statistically significant (p < 0.05). The group with a T1s > 23.54° had greater loss of preoperative Cobb angle and cervical curvature. In group A, the mean preoperative cervical disability index (NDI) was 32.4 ± 3.4, and the mean postoperative NDI score was 16.5 ± 2.1. The mean preoperative VAS scores of neck pain and neck pain were 5.41 ± 1.1 and 5.55 ± 0.3, respectively, and the improvement in neck pain was -0.2%. The mean preoperative NDI in group B was 30.1 ± 2.9, and the mean postoperative NDI score was 11.5 ± 3.1. The mean VAS score for preoperative neck pain was 5.11 ± 1.2, that for postoperative neck pain was 4.18 ± 0.7, and that for neck pain improved by 18%. There was a significant difference between the two groups (p < 0.05). The disappearance of cervical lordosis after posterior cervical double-door laminoplasty is an important cause of postoperative cervical spine pain. The T1s is meaningful for predicting the loss of postoperative curvature in patients undergoing posterior cervical double-door laminoplasty. This is especially true for patients with good preoperative cervical curvature without ankylosis and kyphosis but with a wide T1s.

Can C7 Slope Accurately Substitute for an Invisible T1 Slope According to Age and Cervical Morphology in Cervical Lateral Radiographs?

STUDY DESIGN

A retrospective radiologic study.

OBJECTIVES

To identify age-associated changes in T1 slope (T1S) and C7 slope (C7S), as well as the difference between T1S and C7S (△, which was defined as T1S minus C7S) and to explore the cervical morphology that C7S can be the most accurate alternative for the invisible T1S.

METHODS

625 asymptomatic Chinese volunteers received cervical lateral radiographs from August 2021 to May 2022. Occipito-C2 angle (O-C2), C2-7 angle (C2-7), cranial arch, caudal arch, C7S, and T1S were examined. Thereafter, the △ was established. The correlations among T1S, C7S, △ and other cervical sagittal parameters, and between age and other cervical sagittal parameters were evaluated with the Pearson correlation coefficient analysis. Then, analysis of variance (ANOVA) was conducted to compare variations in cervical sagittal parameters among volunteers aged 40 to 59 years, 60 to 64 years, 65 to 69 years, 70 to 74 years, and ≥75 years of age, and among volunteers with 1 lordotic morphology, 2 lordotic morphology, straight morphology, kyphotic morphology, 1 sigmoid morphology, and 2 sigmoid morphology. Linear regression modeling of the correlation between C7S and T1S in various cervical alignment patterns was then established.

RESULTS

△ had the strongest correlation with caudal arch (r = .646), and weakest correlation with cranial arch (r = -.082). Age was significantly correlated with T1S (r = .250), C7S (r = .244), and △ (r = .112). Among them, △ was stable until 74 years after which it showed an elevation from 3.3° in the group 70-74 years to 4.1° in the group over 75 years. Moreover, there was marked variation between T1S and C7S at 1 lordotic, 2 lordotic, straight and 2 sigmoid alignment patterns, but no difference was seen between T1S and C7S at kyphotic and 1 sigmoid alignment patterns.

CONCLUSIONS

There was a progressive increase in T1S, C7S, and △ with age. Linear regression equations for accurate prediction of T1S were developed based on the C7S in 1 lordotic, 2 lordotic, straight and 2 sigmoid alignment patterns. C7S may be a reliable proxy for T1S in kyphotic and 1 sigmoid alignment patterns.

Initial study on an expert system for spine diseases screening using inertial measurement unit

In recent times, widely understood spine diseases have advanced to one of the most urgetn problems where quick diagnosis and treatment are needed. To diagnose its specifics (e.g. to decide whether this is a scoliosis or sagittal imbalance) and assess its extend, various kind of imaging diagnostic methods (such as X-Ray, CT, MRI scan or ST) are used. However, despite their common use, some may be regarded as (to a level) invasive methods and there are cases where there are contraindications to using them. Besides, which is even more of a problem, these are very expensive methods and whilst their use for pure diagnostic purposes is absolutely valid, then due to their cost, they cannot rather be considered as tools which would be equally valid for bad posture screening programs purposes. This paper provides an initial evaluation of the alternative approach to the spine diseases diagnostic/screening using inertial measurement unit and we propose policy-based computing as the core for the inference systems. Although the methodology presented herein is potentially applicable to a variety of spine diseases, in the nearest future we will focus specifically on sagittal imbalance detection.

Factors related to T1 slope: spinopelvic balance and thoracic compensation

OBJECTIVE

To identify factors associated with T1 slope (T1S).

METHODS

A total of 215 patients over 18 years old who underwent whole-spine X-rays to evaluate lower back pain were enrolled in this study. T1S, pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), thoracic kyphosis (TK), lumbar lordosis (LL), cervical lordosis (CL), thoracolumbar kyphosis (TLK), and sagittal vertical axis (SVA) were measured. Patients were divided into balance, compensatory balance, thoracic compensation, and thoracic decompensation groups.

RESULTS

TK (p < 0.001), SVA (p < 0.001), and CL (p = 0.020) were significantly related to high T1S. The balance group had the smallest PT, largest SS and largest LL of the four groups (p < 0.001). The thoracic compensation group had the smallest TK of all groups (p < 0.001). There was no significant difference in T1S between the balance and thoracic compensation groups (p = 0.099). The thoracic decompensation group had a larger T1S than the balance group (p = 0.023).

CONCLUSIONS

Caudal spine segments had a sequential effect on cranial spine segments. T1S reflected the compensation ability of the spine. The absence of balance tended to increase the T1S. Pelvic posterior rotation and thoracic compensation were two crucial factors protecting against increased T1S in patients with ASD.

Odontoid Fracture as Proximal Junctional Failure in Patients With Multilevel Spine Fusions

STUDY DESIGN

Retrospective study.

OBJECTIVE

Proximal junctional failure (PJF) commonly occurs as a recognized potential outcome of fusion surgery. Here we describe a unique series of patients with multilevel spine fusion including the cervical spine, who developed PJF as an odontoid fracture.

METHODS

We performed a single site retrospective review of patients with prior fusion that included a cervical component, who presented with an odontoid fracture between 2012 and 2019. Radiographic measurements included C2-C7 SVA, C2-C7 lordosis, T1 slope, Occiput-C2 angle, proximal junctional kyphosis, and cervical mismatch. Associated fractures, medical comorbidities, and treatments were determined via chart review after IRB approval.

RESULTS

Nine patients met inclusion criteria. 5 reported trauma with subsequent onset of pain. All patients sustained a Type II odontoid fracture. 5 with associated C1/Jefferson fractures. In all patients, pre-injury Occiput-C2 angle was outside normative range; C2-C7 SVA was greater than 4 cm in 6 patients; T1-slope minus cervical lordosis was greater than 18.5 degrees in 6 patients. 7 patients were treated operatively with extension of fusion to C1 and 2 patients declined operative treatment.

CONCLUSION

In this series of 9 patients with multilevel fusion with type II odontoid fractures, all patients demonstrated abnormal pre-fracture sagittal alignment parameters and a greater than normal association of C1 fractures was noted. Further study is needed to establish the role of poor sagittal alignment with compensatory occiput-C2 angulation as a predisposing factor for odontoid fracture as a proximal junctional failure mechanism.

The effect of ethnicity on the age-related changes of spinopelvic characteristics: a systematic review

Aims

Spinopelvic characteristics influence the hip’s biomechanical behaviour. However, to date there is little knowledge defining what ‘normal’ spinopelvic characteristics are. This study aims to determine how static spinopelvic characteristics change with age and ethnicity among asymptomatic, healthy individuals.

Methods

This systematic review followed the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines to identify English studies, including ≥ 18-year-old participants, without evidence of hip or spine pathology or a history of previous surgery or interventional treatment, documenting lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI). From a total of 2,543 articles retrieved after the initial database search, 61 articles were eventually selected for data extraction.

Results

When all ethnicities were combined the mean values for LL, SS, PT, and PI were: 47.4° (SD 11.0°), 35.8° (SD 7.8°), 14.0° (SD 7.2°), and 48.8° (SD 10°), respectively. LL, SS, and PT had statistically significant (p < 0.001) changes per decade at: −1.5° (SD 0.3°), −1.3° (SD 0.3°), and 1.4° (SD 0.1°). Asian populations had the largest age-dependent change in LL, SS, and PT compared to any other ethnicity per decade at: −1.3° (SD 0.3°) to −0.5° (SD 1.3°), –1.2° (SD 0.2°) to −0.3° (SD 0.3°), and 1.7° (SD 0.2°) versus 1.1° (SD 0.1°), respectively.

Conclusion

Ageing alters the orientation between the spine and pelvis, causing LL, SS, and PT to modify their orientations in a compensatory mechanism to maintain sagittal alignment for balance when standing. Asian populations have the largest degree of age-dependent change to their spinopelvic parameters compared to any other ethnicity, likely due to their lower PI.

Cite this article: Bone Joint Res 2023;12(4):231–244.

Analysis of Sagittal Thoracic Inlet Measures in Relation to Anterior Access to the Cervicothoracic Junction

STUDY DESIGN

Retrospective radiographic study.

OBJECTIVE

The aim of this study was to define the association between thoracic inlet measures in relation to anterior access to the cervicothoracic junction.

METHODS

Trauma CT scans in patients >16 years were analyzed. The projection angle (PA), defined as the angle subtended by a line along the superior endplate of the vertebral body and the line from the anterosuperior corner of the vertebral body to the manubrium, was measured at C7, T1 and T2; angles were positive if the projection was above the manubrium. Thoracic inlet angle (TIA), thoracic inlet distance (TID) and pelvic incidence (PI) were measured.

RESULTS

65 scans were assessed (33 males; mean age 47.7 years (s.d. 8.7)). The mean TIA 79.9° (s.d. 13.4°; range 52.6° - 112.2°), mean TID 66.1 mm (s.d. 6.6 mm) and mean PI was 50.5° (s.d. 10.2°). Mean values for the projection angles at C7, T1 and T2 were 24.2°, 7.6° and -8.3° respectively. PA were positive in 95% at C7, 73% at T1 and 30% at T2. PA at each level correlated significantly with age (mean r=-0.371; P = .015) and TIA (mean r=-0.916; P < .001) but neither TID nor PI. TIA correlated with age (r = 0.328; P = .008).

CONCLUSIONS

The projection angles of the CTJ vertebrae are influenced by thoracic inlet angle and a lesser degree age. Understanding sagittal spinal parameters in the CTJ can aid in planning surgical strategy and approach.

The Effect of Cervical Fusion on Functional Sagittal Spinal Alignment Based on the Inflection Point: Case Series Study

STUDY DESIGN

A retrospective radiologic study.

OBJECTIVE

The inflection point is the disc space between a lordotic and kyphotic segment of spine. To our knowledge, there has been no study evaluating changes in functional sagittal alignment determined by inflection points after cervical fusion surgery. The purpose is to identify changes in functional sagittal alignment after cervical fusion as determined by functional segments between cervicothoracic and thoracolumbar inflection points.

METHODS

Standing radiographs of the sagittal whole spine were taken in 62 patients who underwent cervical fusion procedures. We identified cervicothoracic and thoracolumbar inflection points in the sagittal plane and measured Cobb angles of resulting "functional" cervical, thoracic, and lumbar segments. We also measured the C2 and T1 sagittal vertical axis (SVA) distance to S1 and the anatomic cervical lordosis, thoracic kyphosis, lumbar lordosis, spinopelvic parameters, and T1 sagittal slope. We compared the pre- and post-op values.

RESULTS

The functional cervical segment and T1 sagittal slope increased postoperatively. C2 and T1 SVA distance to S1 decreased postoperatively. In patients with a single level fusion or lower instrumented vertebra (LIV) proximal or equal to C6, functional cervical segment, and anatomic cervical lordosis increased postoperatively. In those with multiple level fusion or LIV distal or equal to C7, the C2 SVA distance to S1 decreased postoperatively.

CONCLUSIONS

After cervical fusion surgery, functional cervical sagittal parameters determined by the inflection point improve without changes in the anatomic sagittal parameters. Postoperative changes in functional sagittal parameters were affected by the number of fused levels and LIV.

Examining Clinical Opinion and Experience Regarding Utilization of Plain Radiography of the Spine: Evidence from Surveying the Chiropractic Profession

Plain Radiography of the spine (PROTS) is utilized in many forms of healthcare including the chiropractic profession; however, the literature reflects conflicting opinions regarding utilization and value. Despite being an essential part of Evidence-Based Practice (EBP), few studies assess Doctors of Chiropractic (DCs) clinical opinions and experience regarding the utilization of (PROTS) in practice. In this study, DCs were surveyed regarding utilization of PROTS in practice. The survey was administered to an estimated 50,000 licensed DCs by email. A total of 4301 surveys were completed, of which 3641 were United States (US) DCs. The Clinician Opinion and Experience on Chiropractic Radiography (COECR) scale was designed to analyze survey responses. This valid and reliable scale demonstrated good internal consistency using confirmatory factor analysis and the Rasch model. Survey responses show that 73.3% of respondents utilize PROTS in practice and 26.7% refer patients out for PROTS. Survey responses show that, among US DCs, 91.9% indicate PROTS has value beyond identification of pathology, 86.7% indicate that PROTS is important regarding biomechanical analysis of the spine, 82.9% indicate that PROTS is vital to practice, 67.4% indicate that PROTS aids in measuring outcomes, 98.6% indicate the opinion that PROTS presents very low to no risk to patients, and 93.0% indicate that sharing clinical findings from PROTS studies with patients is beneficial to clinical outcomes. The results of the study indicated that based on clinical experience, the majority of DCs find PROTS to be vital to practice and valuable beyond the identification of red flags.

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.

Effect of Anterior Cervical Decompression Fusion and Partial Resection of Uncinate Vertebra Joint on Cervical Sagittal Sequence in Patients with Non-Single-Segment Radiculopathy and its Correlation with Curative Effect: A Retrospective Analysis

OBJECTIVE

Analyze the effect of preservation or resection of the partial uncinate joint on the sagittal sequence of the cervical vertebrae in patients with non-single-segment radiculopathy and the correlation between the sagittal sequence of the cervical vertebrae and the long-term effect after surgery, we explored whether it is necessary to perform partial resection of the uncinate joint in patients with cervical spondylotic radiculopathy undergoing anterior cervical decompression and fusion (ACDF).

METHODS

The study retrospectively analyzed 96 patients with cervical spondylotic radiculopathy with more than two segments from August 2016 to January 2021, who underwent ACDF (ACDF group, 45 patients) or ACDF combined with partial uncinate joint resection (ACDF + UT group, 51 patients). Partial resection of the uncinate joint indicated removal of part of the uncinate joint and osteophyte based on the compression of the nerve root during surgery, whereas the uncinate joints in the ACDF group were retained completely. The imaging data and functional scores of the two groups were recorded before surgery, 1 month after surgery, and at the last follow-up. A paired t-test or rank sum test was applied to analyze the data. In addition, the correlation between the imaging parameters and functional scores was validated using the Pearson's test.

RESULTS

All 96 patients successfully completed the surgery and were followed up for at least 12 months, with an average follow-up time of 14 months. At the last follow-up, the pain visual analog scale (VAS), neck disability index (NDI), and neck pain and disability scale (NPAD) scores of the two groups were significantly lower than those before surgery, and the Japanese Orthopaedic Association (JOA) score was significantly higher than that before surgery. At the last follow-up, compared with the ACDF+UT group, the NDI and NPAD scores in the ACDF group decreased more significantly (p < 0.05), and C2-7SVA, △C2-7SVA (the difference between C2-7 SVA at last follow-up and before operation), and T1S values decreased significantly (p < 0.05). The C2-7 Cobb angle was positively correlated with the JOA score and T1S (p < 0.05) and negatively correlated with the VAS, NDI, and NPAD scores and CGH-C7SVA (p < 0.05). C2-7SVA was positively correlated with CGH-C7SVA and T1S (p < 0.05).

CONCLUSION

Patients with non-single-segmental cervical spondylotic radiculopathy and ACDF with or without uncinate joint resection can have effective improvement in the clinical effect and sagittal balance; however, partial uncinate joint resection has a certain negative impact on the long-term reconstruction of sagittal balance and long-term effects in patients after surgery.

Comparison of Sensorimotor Integration and Skill-Related Physical Fitness Components Between College Athletes With and Without Forward Head Posture

OBJECTIVE

To evaluate sensorimotor integration and skill-related physical fitness components for participants with forward head posture (FHP) compared with strictly matched controls with normal head alignment.

MATERIAL AND METHODS

We measured FHP, sensorimotor processing, and skill-related physical fitness variables in 50 participants with FHP and in 50 participants matched for age, gender, and body mass index with normal FHP, defined as having a craniovertebral angle >55°. Sensorimotor processing and integration variables were: (1) amplitudes of the spinal N13, (2) brainstem P14, (3) parietal N20 and P27, and (4) frontal N30 potentials. The skill-related physical fitness variables selected for the study were (1) T-test agility, (2) leg power, (3) stork static balance test, and (4) Y-balance test.

RESULTS

There was a statistically significant difference between the FHP group and control group for the sensorimotor integration variable: frontal N30 potentials (P < .05). Additionally, between-group differences were found for the sensorimotor processing variables: amplitudes of spinal N13, brainstem P14, and parietal N20, and P27 (P < .05). Statistically significant differences between groups for the skill-related physical fitness variables were also identified: T-test agility, leg power, stork static balance test, and Y-balance test (P < .05). The magnitude of the craniovertebral angle showed a correlation with all measured variables (P < .05).

CONCLUSION

College athletes with FHP exhibited altered sensorimotor processing and integration measurements and less efficient skill-related physical fitness compared with athletes with normal sagittal head posture alignment.

Clinical significance of the C2 slope after multilevel cervical spine fusion

OBJECTIVE

The C2 slope (C2S) is one of the parameters that can determine cervical sagittal alignment, but its clinical significance is relatively unexplored. This study aimed to evaluate the clinical significance of the C2S after multilevel cervical spine fusion.

METHODS

A total of 111 patients who underwent multilevel cervical spine fusion were included in this study. The C2S, cervical sagittal vertical axis (cSVA), C2-7 lordosis, and T1 slope (T1S) were measured in standing lateral cervical spine radiographs preoperatively and 2 years after the surgery. Clinical outcome measures were visual analog scale (VAS) neck and arm pain scores, Neck Disability Index (NDI), Japanese Orthopaedic Association (JOA) scale score, and patient-reported subjective improvement rate (IR) percentage. Statistical analysis was performed using a paired-samples t-test and Pearson's correlation, and a receiver operating characteristic (ROC) curve to determine the cutoff values of C2S.

RESULTS

C2S demonstrated a significant correlation with the cSVA, C2-7 lordosis, T1S, and T1S minus cervical lordosis. C2S revealed a significant correlation with the JOA, neck pain VAS, and NDI scores at 2 years after surgery. Change in the C2S correlated with postoperative neck pain and NDI scores. ROC curves demonstrated the cutoff values of C2S as 18.8°, 22.25°, and 25.35°, according to a cSVA of 40 mm, severe disability expressed by NDI, and severe myelopathy, respectively.

CONCLUSIONS

C2S can be an additional cervical sagittal alignment parameter that can be a useful prognostic factor after multilevel cervical spine fusion.

Reciprocal Changes Following Cervical Realignment Surgery

Over the last few decades, the importance of the sagittal plane and its contour has gained significant recognition. Through full-body stereoradiography, the understanding of compensatory mechanisms, and the concept of global balance and reciprocal change has expanded. There have been a few reports describing how cervical realignment surgery affects global spinal alignment (GSA) and global balance. Despite the research efforts, the concept of reciprocal change and global balance is still perplexing. Understanding the compensatory status and main drivers of deformity in a patient is vital because the compensatory mechanisms may resolve reciprocally following cervical realignment surgery. A meticulous preoperative evaluation of the whole-body alignment, including the pelvis and lower extremities, is paramount to appreciate optimal GSA in the correction of spinal malalignment. This study aims to summarize relevant literature on the reciprocal changes in the whole body caused by cervical realignment surgery and review recent perspectives regarding cervical compensatory mechanisms.

Clinical Impact and Correlations of Odontoid Parameters Following Multilevel Posterior Cervical Fusion Surgery

OBJECTIVE

C2 slope (C2S), a cervical parameter mathematically approximated as T1 slope minus cervical lordosis (T1S-CL), predicts functional improvement in cervical deformity patients. Nonetheless, C2S is a positional parameter based only on the horizontal axis. The current study aims to introduce novel odontoid parameters and establish their relationships with patient-reported health-related quality of life (HRQoL).

METHODS

Lateral plain radiographs of 32 adults who underwent multilevel posterior cervical fusion were analyzed. The odontoid parameters included odontoid incidence (OI), C2S, odontoid tilt (OT), and gravity line-C2 distance (GL-C2), while the cervical parameters were the Cobb angle at C0-1, C1-2, C0-2, C2-7, C2-7 sagittal vertical axis (cSVA), T1 slope, and T1S-CL. The range of motion (ROM) of the occipito-atlantoaxial complex was measured in flexion and extension plain radiographs. Scores on the Neck Disability Index (NDI) and visual analogue scale (VAS) for axial neck (VASn) and arm pain were measured.

RESULTS

Compared to asymptomatic subjects, patients had larger C2S, cSVA, and T1S-CL, and smaller OT. Preoperatively, OI was significantly correlated with the ROM of C1-2 (r = 0.37, p < 0.05) and C0-2 (r = 0.46, p < 0.01). OT and C2S had significant correlations with the C0-1, C1-2, and C0-2 angles, GL-C2, and T1S-CL. Postoperative NDI scores were significantly correlated with OI (r = -0.40, p < 0.05) and OT (ρ = -0.37, p < 0.05). VASn was significantly correlated with GL-C2 (r = -0.35, p < 0.05).

CONCLUSION

The odontoid parameters were significantly correlated with established cervical parameters and HRQoL measures. OI is a constant parameter representing the individual's compensatory reservoir at the upper cervical spine.

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.

Postoperative proximal junctional kyphosis correlated with thoracic inlet angle in Lenke 5c adolescent idiopathic scoliosis patients following posterior surgery

Background

Proximal junctional kyphosis is a common complication after posterior fusion in patients with adolescent idiopathic scoliosis and is correlated with postoperative changes of thoracic kyphosis. In lenke 5c patients, higher postoperative LL and spontaneous change of TK may produce an effect on final PJK. However, no studies has been performed to evaluate the correlation of PJK with thoracocervical parameters in patients with AIS.

Methods

Data from 98 patients who underwent posterior fusion for Lenke 5C AIS with 2 years of follow-up were retrospectively reviewed. Patients in the extended fusion group underwent fusion at levels higher than upper-end vertebra + 2 (n = 38), and those in the thoracolumbar/lumbar (TL/L) fusion group underwent fusion at UEV + 2 or lower (n = 60).

Results

During an average follow-up of 38.1 months, 23 of 98 patients developed PJK. The extended fusion group had a higher incidence of PJK than the TL/L fusion group (14/38 vs. 9/60, respectively; P = 0.01) and a significantly greater decrease in thoracic kyphosis than the TL/L group (P < 0.01). Patients with PJK had a significantly larger preoperative thoracic inlet angle (TIA) than those without PJK (P < 0.01). Multivariate analysis showed that a greater preoperative TIA and extended fusion were associated with PJK. The Scoliosis Research Society 22-item questionnaire score did not significantly differ between the PJK and non-PJK groups.

Conclusions

The preoperative TIA could be a predictor of PJK. Among patients with Lenke 5C AIS, those with a TIA of > 71° are more likely to develop PJK. Additionally, extended fusion in patients with Lenke 5C may increase the risk of PJK.

Sagittal alignment of the cervical spine: radiographic analysis of 111 asymptomatic adolescents, a retrospective observational study

Purpose

To describe the cervical spine morphology and explore its relationship to global sagittal alignment parameters in the asymptomatic adolescent population. 

Methods

A total of 111 adolescent subjects were included. Sagittal alignment parameters, including C7 Slope, C2-C7 Cobb, C2-7 plumb line (PL), C2-S1 Sagittal Vertical Axis (SVA), C7-S1 SVA, T5-12 Cobb, T10-L2 Cobb, L1-S1 Cobb, pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS), were obtained from lateral radiographs. 

Results

Forty-four males and sixty-seven females with a mean age of 16.12 ± 2.40 years were included in this study. The mean values of C7 Slope, C2-7 Cobb and C2-7PL were 20.45 ± 8.88°, -7.72 ± 12.10°, and 13.53 ± 11.63 mm, respectively. C2-7 Cobb, C7 Slope showed significant differences between the male and female groups. Correlation analysis showed that C7 slope was significantly correlated with C2-7 Cobb (r = -0.544, P < 0.001), C2-S1 SVA (r = 0.335, P < 0.001), and C7-S1 SVA (r = 0.310, P = 0.001), but not lumbosacral parameters(L5-S1 Cobb, PI, PT, SS). Using a modified method of Toyama to describe the cervical spine morphology, there were 37 cases (33.3%) in the Lordotic group, and C7 slope, C2-7 Cobb and C2-7PL showed significant differences between groups. According to C2-C7 Cobb, there were 80 Lordotic cases (72.1%). C7 slope and C2-7PL were significantly different between the two groups.

Conclusion

The cervical spine morphology of asymptomatic adolescents varies widely, from lordotic to kyphotic. Combining different classification methods provides a better understanding of the morphology of the cervical spine. C7 slope is an important predictor of global sagittal balance and C2-7PL is a key parameter for restoring cervical lordosis, which should be considered pre-operatively and for conservative treatment. Cervical regional sagittal alignment parameters are not correlated with lumbosacral parameters, and C2-7 Cobb, C7 Slope showed significant differences between males and females.

[Normative values of cervical sagittal alignment according to the whole spine balance: Based on 126 asymptomatic Chinese young adults]

OBJECTIVE

To explore the normal distribution of cervical sagittal alignment and the relationship between cervical alignment and global spine balance in asymptomatic young adults.

METHODS

A cohort of 272 asymptomatic Chinese adults (including 161 males and 111 females, with an average age of (23.2±4.4) years, ranging from 18 to 45 years) were prospectively recruited from November 2011 to December 2014. The C₀-C₂ angle, disk angles from C₂-C₃ to C₆-C₇, vertebral angles from C₃ to C₇, T₁ slope, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), C₂-C₇ sagittal vertical axis (C₂-C₇SVA), center of gravity of head to C₇SVA (CGH-C₇SVA), C₇-S₁SVA were measured and statistically analyzed. All the subjects were categorized with the Roussouly classification and the cervical morphologies were evaluated as lordotic, straight, sigmoid or kyphotic. Spinal sagittal alignment parameters were compared between different sexes and Roussouly classifications with independent student t test, analysis of variance (ANOVA) or Chi-square test. Correlations between cervical sagittal alignment and global spine sagittal alignment were calculated using the Pearson and Spearman correlation coefficient. Linear regression analysis was performed.

RESULTS

Sixty-seven males and 59 females aged from 18 to 30 years old were included in the study. The mean value of C₀-C₇ was 26.0°±12.8°, composed of 15.2°±6.7° for C₀-C₂, 9.1°±12.1° for sum of disk angles from C₂-C₃ to C₆-C₇, and 1.4°±10.2° for sum of vertebral angles from C₃ to C₇. C₂-C₇SVA [(18.6±7.9) mm] and CGH-C₇SVA [(22.9±12.3) mm]were offset ideally by C₇-S₁SVA [(-21.6±31.0) mm]. Males had a larger T₁ slope (P < 0.05) and accordingly, a larger cervical lordosis C₂-C₇ (P < 0.01) and C₀-C₇ angle (P < 0.01) than females. Males had a smaller C₇-S₁SVA (P < 0.01) and accordingly, a smaller CGH-C₇SVA (P=0.165) than females. Significant difference was found between cervical alignment of different Roussouly types (P < 0.01). In general, a larger LL was consistent with a set of larger TK, C₂-C₇angle, C₀-C₇ angle, and vice versa. There was no significant correlation between cervical morphology and the Roussouly classification (Chi-square=10.548, P=0.308). There was significant correlation between cervical alignment and T₁ slope (P < 0.01), TK (P < 0.01). There was significant correlation between adjacent segmental angles from T₁ slope up to C₀-C₂ angle (P < 0.05).

CONCLUSION

Normative values of each vertebral angle and disk angle were established. The cervical lordosis occurred mainly at C₀-C₂ and disk levels, which was influenced by parameters of other parts of the spine, such as T₁ slope, TK and the Roussouly classification. There was significant correlation between adjacent disk angles.

Sagittal Balance Using Position and Orientation of Each Vertebra in an Asymptomatic Population

STUDY DESIGN

A monocentric, retrospective radiographic study with 99 asymptomatic volunteers.

OBJECTIVE

The authors performed the postural analysis commonly scheduled when evaluating sagittal balance in a vertebra-by-vertebra manner by enrolling an asymptomatic population. They measured the position and angulation of each vertebra to reveal those for which the spatial positioning could be relevant during spinal surgeries.

SUMMARY OF BACKGROUND DATA

Several recent publications detailed the sagittal alignment parameters and focus on global analysis parameters. Some patients with identical commonly evaluated spinal parameters have exhibited very different profiles, with notable differences in vertebral positions and orientations. Therefore, a fine segmental analysis of position of each vertebra could be interest to gain understanding of spine alignment.

MATERIALS AND METHODS

The authors obtained full-spine EOS x-rays of 99 volunteers in the standard free-standing position. We used a validated three-dimensional reconstruction technique to extract current spinal parameters and the positions and angulations of all vertebrae and lumbar discs. Particular attention was paid to the positions and angulations of the apical and transitional vertebrae in the general population and in subgroups according to pelvic incidence (PI).

RESULTS

T1 was the most common transitional cervicothoracic vertebra (in 89.9% of subjects) and was oriented downwards by an average of 22.0° (SD=7.3°, minimum=2.3°, maximum=40.1°). The thoracic apex trio of T5 (22.2%), T6 (28.3%), and T7 (36.4%) were equally found. The transitional thoracolumbar vertebrae were L1 (39.4%) and T12 (33.3%). The lumbar apex was usually the L3-L4 disc (36.4%). T1 seemed to be the transitional vertebra (90%) irrespective of the PI. For the other relevant vertebrae, the greater the PI, the more cranial the vertebra.

CONCLUSIONS

We performed a detailed three-dimensional assessment of overall spinal balance using positional and rotational parameters. The positions and orientations of all vertebrae were specified, particularly the apical and transitional vertebrae.

LEVEL OF EVIDENCE

Level 3.

The Difference of Sagittal Correction of Adult Subaxial Cervical Spine Surgery According to Age: A Retrospective Study

Objective

At present, the true sagittal alignment of the cervical spine is uncertain, resulting in no standard reference for subaxial cervical surgery. So, we aimed to explore the age difference of normal cervical sagittal alignment and to further investigate the mid‐and long‐term changes of sagittal alignment after subaxial cervical spine surgery.

Materials and Methods

This was a retrospective study and 1223 asymptomatic volunteers and 79 patients undergoing subaxial cervical spine surgery were retrospectively reviewed in total. Asymptomatic volunteers and patients were divided into six subgroups: 20–29, 30–39, 40–49, 50–59, 60–69 and ≥70 groups. The age difference and trend with age of cervical sagittal parameters of asymptomatic volunteers were assessed by cervical lateral radiography and analyzed by ANOVA test, and the regression equation of C2‐7 Cobb was established via multiple linear regression. Based on the C2‐7 Cobb regression equations of different ages, the theoretical value, deviation value, loss value of the C2‐7 Cobb, and JOA recovery rate of patients were calculated, and the correlation among the loss value, deviation value of the C2‐7 Cobb, and JOA recovery rate of the 79 patients was evaluated by Pearson correlation analysis.

Results

For the asymptomatic volunteers, the C0‐2 Cobb decreased gradually with increasing age. The C2‐7 Cobb, C2‐7 SVA, T1S, NT, and TIA increased gradually with increasing age. The CBVA fluctuated with increasing age. T1S demonstrated a moderate correlation with C2‐7 Cobb (r = 0.60, p < 0.01); C0‐2 Cobb, C2‐7 SVA, CBVA, and TIA demonstrated a fair correlation with C2‐7 Cobb (r = −0.30, −0.33, 0.41, 0.40, p < 0.01); age demonstrated a poor correlation with C2‐7 Cobb (r = 0.19, p < 0.01). The regression equations of C2‐7 Cobb were established using C0‐2 Cobb, C2‐7 SVA, CBVA, and T1S. For the patients with subaxial cervical spine surgery, the loss of C2‐7 Cobb was moderately correlated with the deviation of C2‐7 Cobb (r = 0.33, p < 0.01).

Conclusion

The age difference of cervical sagittal alignment was obvious, and the C2‐7 Cobb increased with age especially. The closer the postoperative C2‐7 Cobb was to the theoretical value of corresponding age, the smaller the loss of correction angle was, and the better the mid‐ and long‐term outcomes. The personalized sagittal reconstruction should be performed according to age difference for subaxial cervical spine surgery.

Odontoid Incidence: A Novel Cervical Parameter Influencing Cervical Alignment From Top to Bottom

Objective

By using angulation of the axis itself, this study aims to define and analyze odontoid incidence (OI) and odontoid tilt (OT) as novel cervical alignment parameters and investigate their correlations with cervical alignment.

Methods

Novel and existing parameters were measured with whole-spine lateral plain radiographs and EOS images of 42 adults without cervical symptoms. The correlations of OI, OT, C2 slope (C2S), and T1 slope (T1S) were calculated.

Results

The OI, OT, and C2S showed significant correlations with C2–7 angle (r = 0.43, r = -0.42, r = 0.62, respectively) and C0–2 angle (r = -0.33, r = 0.48, r = -0.61, respectively). OI, OT, T1S were independent predictors of the C2–7 angle in univariate regression analysis (adjusted-R² = 0.17, R² = 0.15, R² = 0.28, respectively). OI, OT, and T1S were independent predictors in the multivariable regression analysis with estimated standardized coefficients of 0.36, -0.67, -0.69, respectively (adjusted- R² = 0.80, p < 0.001). Regarding the C0–2 angle, OI and OT were independent predictors in the univariate regression analysis (adjusted-R² = 0.08, R² = 0.21, respectively).

Conclusion

OI, OT, and C2S had significant correlations with cervical alignment. As the pelvic incidence, the OI is the only anatomical and constant parameter that could be used as a reference point related to the cervical spine from the rostral end. The study results may serve as baseline data for further studies on the alignment and balance of the cervical spine.

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.

Relationship between TIA minus C0-7 angle and C2-7 SVA: analysis of 113 symptomatic patients

Background

Measurement of T1 slope (T1S) can be difficult due to the anatomical positioning of the shoulders. And thoracic inlet angle (TIA) was a morphological parameter and not changed by the position. We proposed a new parameter, TIA minus C0-7 angle (TIA-C07), to evaluate C2-7 SVA in order to overcome the T1S imperfection.

Methods

This was a retrospective radiological analysis of symptomatic subjects. The following cervical parameters were measured: Cervical lordosis angle (CL), C0-7 angle (C0-7), occiput-C2 lordosis angle (O-C2), C2-7 sagittal vertical axis (C2–7 SVA), TIA and TIA-C07. The Pearson correlation test was calculated, and the stepwise multiple regression analysis was conducted to determine the best predictor for C2-7 SVA. A paired sample t test was used to compare the predicted and measured C2-7 SVA.

Results

The mean age of 113 patients was 60.02 ± 9.67. The average O-C2, CL, C0-7, TIA, TIA-C07 and C2-C7 SVA was 29.24 ± 8.48°, 13.67 ± 11.22°, 42.91 ± 11.44°, 76.07 ± 9.54°, 33.16 ± 13.18° and 21.34 ± 11.42 mm. The predictive formula was founded: C2-7 SVA = 2.80 + 0.56 * (TIA—C07) (R = 0.645, R2 = 0.416). There was no statistical difference between the predicted and the measured C2-7 SVA (t = 0.085, P = 0.933).

Conclusions

TIA and C0-7 mismatch may significantly impact cervical alignment, and a greater T1A-C07 was related to a greater degree of C2-7 SVA. TIA-C07 may be a more important predictor for C2-7 SVA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05301-0.

Mechanisms of compensatory for cervical lordosis changes after laminectomy with fusion

Background

The compensatory mechanisms for cervical lordosis change after laminectomy with fusion was not clear. The objective of this study was to evaluate the compensatory behaviors for cervical lordosis change after laminectomy with fusion.

Methods

This was a retrospective radiological analysis of 43 patients with cervical spondylotic myelopathy who underwent laminectomy with fusion (LCF). The following cervical parameters were measured: C2-7 Cobb angle (C2-7), occiput-C2 angle (O-C2), the cervical sagittal vertical axis (cSVA), and T1 slope (T1S). The difference was calculated for all angle parameters between the two time points using the following formula: the amount of change (Δ) = (value at the follow-up)—(preoperative value). Non-parametric tests and the t-test were used to compare the difference. The Pearson correlation test was performed, and stepwise multiple regression analysis was performed to determine the best correlation between ∆cSVA and ∆T1S.

Results

The mean age of 43 patients was 65.51 ± 9.80 years. All patients were classified into two subgroups based on ΔcSVA: Group M (maintained) and, Group I (increased). The preoperative O-C2, C2-7, T1S, and cSVA were similar between Group M and group I (p = 0.950, p = 0.731, p = 0.372, and p = 0.152, respectively). Postoperative O-C2 and postoperative cSVA were significantly different (p = 0.036 and p = 0.004, respectively). ∆O-C2, ∆T1S and ∆cSVA were significantly different between the two groups (p = 0.006, p = 0.000, and p = 0.000, respectively). ΔcSVA had significant correlations with ΔO-C2 neutral angle (r = 0.377) and ΔT1S (r = 0.582). A linear regression equation was established: ΔcSVA = 0.602 + 0.103 * ΔT1S (R = 0.582, R² = 0.339).

Conclusions

The decrease of TIS should be the first and foremost compensation for the loss of lordosis in C2-7 segments after LCF. When the change of T1S alone can not prevent the deterioration of cervical sagittal balance, further increases in the O-C2 segment occur.

Investigation of Titanium Mesh and Nano-Hydroxyapatite/Polyamide 66 Bone Graft in Cervical Reconstruction of Spondylosis After Sub-Total Vertebral Body Resection

The nano-hydroxyapatite/polyamide 66 (n-HA/PA66) bionic bone column, as a high-performance tissue repair and replacement material, introduced as a high osteo-induction ability agent. Nanomaterial has significantly taken a place in orthopedic surgery, however, the efficacy of using n-HA/PA66 is yet to be established. In this regard, this study evaluated various sagittal parameters (such as imaging measurement) and clinical efficacy in postoperative patients, whom underwent cervical reconstruction surgery due to cervical spondylosis myelopathy (CSM). In this study, total 62 CSM cases were enrolled between October 2016 to March 2020, and were hospitalized for cervical reconstruction surgery. 31 cases were grafted with titanium mesh and 31 cases were grafted with n-HA/P66. The sagittal parameters such as cervical spine lateral radiographs (C_0-2Coob, C_2-7Coob, T1S, CSVA, and TIA) were taken before operation, after operation (within 1 week), 3, 6, and 9 months after operation. In order to evaluate the clinical efficacy, we used JOA scores before, after, 3 months, 6 months and 9 months after operation. Results showed that JOA scores after the re-examination in the two groups (titanium and n-HA/P66) were significantly higher than before the operation, suggesting a well postoperative functional recovery after surgery in both groups; however, there was no significant difference in JOA score and JOA improvement index between the two groups. In regard of angles measurement (C_0-2Cobb, C_2-7Cobb, T1S, CSVA, and TIA), we observed no significant difference between these two groups before and after the operation. In addition, we showed that C_0-2Cobb and C_2-7Cobb angle had a significant positive correlation; and C_0-2Cobb angle is positively correlated with T1S, and negatively correlated with CSVA. Both titanium mesh and n-HA/PA66 can be well improved and maintained within 9 months after surgery with clinical efficacy, however, using n-HA/PA66 might have more benefits.

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

Background

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

Methods

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

Results

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

Conclusions

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

Differences in Demographic and Radiographic Characteristics between Patients with Visible and Invisible T1 Slopes on Lateral Cervical Radiographic Images

Introduction: The T1 slope is important for cervical surgical planning, and it may be invisible on radiographic images. The prevalence of T1 invisible cases and the differences in demographic and radiographic characteristics between patients whose T1 slopes are visible or invisible remains unexplored. Methods: This pilot study aimed to evaluate the differences in these characteristics between outpatients whose T1 slopes were visible or invisible on radiographic images. Patients (n = 60) who underwent cervical radiography, whose T1 slope was confirmed clearly, were divided into the visible (V) group and invisible (I) group. The following radiographic parameters were measured: (1) C2-7 sagittal vertical axis (SVA), (2) C2-7 angle in neutral, flexion, and extension positions. Results: Based on the T1 slope visibility, 46.7% of patients were included in group I. The I group had significantly larger C2-7 SVA than the V group for males (p < 0.05). The C2-7 SVA tended to be larger in the I group, without significant difference for females (p = 0.362). Discussion: The mean C2-7 angle in neutral and flexion positions was not significantly different between the V and I groups for either sex. The mean C2-7 angle in the extension position was greater in the V group. The T1 slope was invisible in males with high C2-7 SVA.

Correlation between the cervical sagittal alignment and spine - pelvic sagittal alignment in asymptomatic adults

Background

Although there are studies that adequately document the linear correlation between pelvic incidence (PI), sacral slope, lumbar lordosis, and thoracic kyphosis, few have analyzed the pelvic-spine correlation including the cervical spine.

Methods:

This is a cross-sectional study, wherein the cervical spine was evaluated using radiography and computed tomography (CT) scans, the lumbosacral spine and the pelvis was evaluated using radiography, in adult patients without spinal pathology. Using the Surgimap tool, cervical and spinopelvic parameters were calculated by several investigators. To evaluate the correlation between cervical and spinopelvic parameters, Spearman's coefficient was calculated. To evaluate the concordance correlation of the measured parameters of cervical sagittal alignment on tomography and conventional radiography, Lin's coefficient was calculated and Bland–Altman plots were performed.

Results:

A total of 51 healthy adults were included in a follow-up from January 2019 to December 2020. Cervical sagittal alignment and sagittal spinopelvic alignment were assessed using radiography, and a correlation was observed between T1 slope (T1S) and lumbar mismatch (coefficient of 0.28, P = 0.047). Then, cervical sagittal alignment was evaluated using CT and sagittal spinopelvic alignment using radiography, and no correlation was observed between PI and thoracic inlet angle or cervical mismatch with lumbar mismatch.

Conclusion:

In asymptomatic patients, in whom cervical sagittal alignment and spinal-pelvic alignment were evaluated, only a positive correlation was found between lumbar mismatch and T1S, which lacks clinical significance. No concordance was identified between lumbar mismatch and cervical mismatch. Therefore, it is inferred that there is an independence between the sagittal spine-pelvic alignment with respect to the sagittal cervical alignment.

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.

Cervical Spinal Alignment Change Accompanying Spondylosis Exposes Harmonization Failure with Total Spinal Balance: A Japanese Cohort Survey Randomly Sampled from a Basic Resident Registry

The relationship between spinal posture and quality of life has garnered considerable attention with the increase in older community-dwelling residents. However, details of this association remain insufficient. A recent Japanese population cohort epidemiological locomotion survey (the Obuse study) revealed that the C2–C7 cervical sagittal vertical axis (CSVA) began to increase in males from their 60s, but not in females. This study aimed to clarify the pathology of these cervical spondylotic changes. A total of 411 participants (202 male and 209 female) aged between 50 and 89 years were selected by random sampling from a cooperating town’s resident registry. All participants underwent lateral X-ray photography in a standing position for the measurement of several sagittal spinal alignment parameters, including CSVA, C2–C7 cervical lordosis (CL), T1 slope (T1S), and sagittal vertical axis (SVA). The presence of cervical spondylotic changes was also recorded. Associations of cervical sagittal spinal alignment with cervical spondylosis and between cervical and total sagittal spinal alignment were examined. The prevalence of cervical spondylosis was significantly higher in males (81%) than in females (70%) (p = 0.01). CL was significantly smaller in cervical spondylosis subjects when adjusted by age (3.4 degrees less; p = 0.01). T1S minus CL displayed a moderate positive correlation with CSVA in both males and females (r = 0.49 and 0.48, respectively, both p < 0.01). In males only, CSVA and CL showed weak positive correlations with SVA (r = 0.31 and 0.22, respectively, both p < 0.01) independently of age. Cervical spinal misalignment was more clearly associated with diminished SF-8^TM scores in females than in males. In community-dwelling elderly residents, cervical sagittal spinal alignment change accompanying cervical spondylosis manifested as hypofunction to compensate for whole-spine imbalance.

Analyzing the Significance of T1 Slope minus Cervical Lordosis in Patients with Anterior Cervical Discectomy and Fusion Surgery

Objective

Accurate measurement of T1 slope (a component of T1s minus cervical lordosis [CL]) is often constrained by anatomical limitations. In this situation, efforts should be made to find the exact meaning of T1s-CL and whether there are any alternatives to it.

Methods

We enrolled 117 patients who received two-level anterior cervical discectomy and fusion (ACDF). Occipital slope, C2 slope (C2s), C7 slope (C7s), T1, O-C2 angle (O-C2A), C2-7 angle (C2-7A), O-C7 angle (O-C7A), T1s-CL, C7-T1 angle (C7-T1A), and C2-7 sagittal vertical axis were measured. We determined 16° (T1s-CL) as the reference point for dividing subjects into the mismatch group and the balance group, and a comparative analysis was performed.

Results

The mean value of C7-T1A was constantly maintained within 2.6° peri-operatively. In addition, C2s and T1s-CL showed the same absolute change (Δ|0.8|°). The mean values of T1s-CL of the mismatch and balance groups were 23.0° and 7.6°, respectively. The five factors with the largest differences between the two groups were as follows : C2s (Δ13.3°), T1s-CL (Δ15.4°), O-C2A (Δ8.7°), C2-7A (Δ14.7°), and segmental angle (Δ7.9°) before surgery. Only four factors showed statistically significant change between the two groups after ACDF : T1s-CL (Δ4.0° vs. Δ0.2°), C2s (Δ3.2° vs. Δ0.7°), O-C2A (Δ2.6° vs. Δ1.3°), C2-7A (Δ6.3° vs. Δ1.3°). A very strong correlation between T1s-CL and C2s was also found (r=|0.88–0.96|).

Conclusion

C2s itself may be the essential key to represent T1s-CL. The amounts and directions of change of these two factors (T1s-CL and C2s) were also almost identical. The above phenomenon was re-confirmed once again through the correlation analysis.

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.

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

BACKGROUND

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

HYPOTHESIS

Cervical parameters measured on full-body radiographs are reliable.

PATIENTS AND METHODS

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

RESULTS

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

DISCUSSION

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

LEVEL OF EVIDENCE

III; retrospective analysis of prospectively collected data.

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

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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