Posterior Tangent Method Research Articles

A New Index for Cervical Curvature Evaluation - Relative Cervical Curvature Area

ObjectiveTo put forward a new index of cervical curvature evaluation - relative cervical curvature area,and a new classification of cervical spine was proposed according to the relative cervical curvature area. MethodsA total of 167 subjects with cervical spondylosis were included in the study. Firstly, 119 subjects were selected to measure C2-C7 lordosis angle by Cobb angle method, Harrison posterior tangent method and Jackson physiological stress line method, and then their relative cervical curvature area, C1-C7 Cobb angle, C7 slope and T1 slope were measured.The correlation between relative cervical curvature area and three measurement methods and common sagittal parameters was analyzed.According to the angle classification method, we calculated the diagnostic boundary value of the relative cervical curvature area classification, and selected 48 subjects to evaluate its diagnostic efficacy.Finally, 119 subjects were re-evaluated according to the diagnostic threshold and the number of intersections to verify the feasibility of the new classification. ResultsThe results showed that the relative cervical curvature area index had good intra-observer and inter-observer repeatability. Relative cervical curvature area was correlated with Harrison posterior tangent method ( r = 0.930 ), Cobb angle method ( r = 0.886 ) and Jackson physiological stress line method ( r = 0.920 ), and correlated with C1-C7 Cobb angle, C7 slope and T1 slope.The relative cervical curvature area has a good diagnostic performance for distinguishing patients with lordosis, straightening and kyphosis.According to the new classification of cervical spine, 119 subjects were divided into 57 simple lordosis, 11 simple straightening, 4 simple kyphosis, 26 S-type and 21 RS-type. ConclusionThe relative cervical curvature area uses the area parameter instead of the original angle parameter and distance parameter to incorporate the change of segmental curvature, which makes up for the shortcomings of the Cobb angle method that only evaluates the curvature of two vertebrae, and better reflects the cervical curvature.Studies have shown that relative cervical curvature area has good repeatability and diagnostic value, and found that it has a good correlation with common cervical sagittal parameters.The new classification of cervical spine makes up for the disadvantage that the angle classification method cannot distinguish between S-type and RS-type, and initially proposes to use the number of intersections and the relative absolute value area to reflect the severity of S-type.

Biomechanical and Clinical Study of Rod Curvature in Single-Segment Posterior Lumbar Interbody Fusion.

Objective: Pedicle screw fixation is a common technique used in posterior lumbar interbody fusion (PLIF) surgery for lumbar disorders. During operation, rod contouring is often subjective and not satisfactory, but only few studies focused on the rod-contouring issue previously. The aim of the study was to explore the effect of the rod contouring on the single-segment PLIF by the finite element (FE) method and retrospective study. Methods: A FE model of the lumbosacral vertebrae was first reconstructed, and subsequently single-segmental (L4/5) PLIF surgeries with four rod curvatures (RCs) were simulated. Herein, three RCs were designed by referring to centroid, Cobb, and posterior tangent methods applied in the lumbar lordosis measurement, and zero RC indicating straight rods was included as well. Clinical data of patients subjected to L4/5 segmental PLIF were also analyzed to verify the correlation between RCs and clinical outcome. Results: No difference was observed among the four RC models in the range of motion (ROM), intersegmental rotation angle (IRA), and intradiscal pressure (IDP) under four actions. The posterior tangent model had less maximum stress in fixation (MSF) in flexion, extension, and axial rotation than the other RC models. Patients with favorable prognosis had larger RC and positive RC minus posterior tangent angle (RC-PTA) of fused segments with respect to those who had poor prognosis and received revision surgery. Conclusion: All RC models had similar biomechanical behaviors under four actions. The posterior tangent-based RC model was superior in fixation stress distribution compared to centroid, Cobb, and straight models. The retrospective study demonstrated that moderate RC and positive RC-PTA were associated with better postoperative results.

Apoptosis of endplate chondrocytes in cervical kyphosis is associated with chronic forward flexed neck: an in vivo rat bipedal walking model

BackgroundThis study was undertaken to establish a rat bipedal walking model of cervical kyphosis (CK) associated with chronic forward flexed neck and assess the effects of chronic forward flexed neck on endplate chondrocytes.MethodsForty-eight 1-month-old Sprague-Dawley rats were randomly divided into 3 groups: forward flexed neck group (n = 16), bipedal group (n = 16), and normal group (n = 16). Cervical curves were analyzed on a lateral cervical spine X-ray using Harrison’s posterior tangent method before the experiment and at 2-week intervals for a 6-week period. Histologic changes in cartilaginous endplate chondrocytes were observed using hematoxylin and eosin (H&E) staining, transmission electron microscopy (TEM), and terminal deoxyribonucleotidyl transferase (TdT)-mediated dUTP nick-end labeling.ResultsRadiographic findings suggested a significantly decreased cervical physiological curvature in the forward flexed neck group over the 6-week follow-up; normal cervical curves were maintained in other groups. The average cervical curvature (C2–C7) was − 7.6 ± 0.9° in the forward flexed neck group before the experiment, − 3.9 ± 0.8° at 2 weeks post-experiment, 10.7 ± 1.0° at 4 weeks post-experiment, and 20.5 ± 2.1° at the last follow-up post-experiment. Histologically, results of H&E staining unveiled that cartilaginous endplate chondrocytes were arranged in an irregular fashion, with the decreased number at the observation period; the incidence of apoptotic cells in the forward flexed neck group was noticeably higher at the 6-week follow-up than that in other groups.ConclusionsCK developed as the result of chronic forward flexed neck. Histologic changes suggested that chondrocyte apoptosis may play a critical role in the development of cervical kyphotic deformity associated with chronic forward flexed neck.

Clinical and radiological outcomes of kinesiotaping in patients with chronic neck pain: A double-blinded, randomized, placebo-controlled study.

Objectives In this study, we aimed to evaluate the efficacy of kinesiotaping (KT) in patients with chronic non-specific neck pain (NSNP) in terms of pain, disability, cervical range of motion (ROM), and cervical lordosis. Patients and methods Between October 2013 and March 2014, a total of 50 patients (10 males, 40 females; mean age 35.1±9.9 years; range, 17 to 62 years) with chronic NSNP were randomized into the KT (n=25) or the sham KT intervention (n=25) groups. Both groups were additionally given a therapeutic exercise (TE) program. The Visual Analog Scale (VAS) and Neck Disability Index (NDI) scores and ROM measurements were recorded at baseline, at the end of treatment, and at one month. Lateral cervical digital radiographs were analyzed by the Cobb, posterior tangent and effective lordosis methods at baseline and at one month after the treatment. Results There was a statistically significant decrease in the VAS scores compared to baseline in the KT group. The NDI scores significantly decreased in both groups. The patients in the KT group experienced a significant increase in all planes of cervical ROM after the treatment. Cervical radiographs revealed a significant increase in the Cobb and posterior tangent angles only in the KT group. Conclusion Our study results suggest that KT significantly improves VAS, NDI scores, ROM and cervical lordosis angles. The combination of TE and KT is useful in reducing pain and disability and improving ROM and cervical lordosis loss in patients with chronic NSNP.

Effect of age and gender on anterior cervical plating

Objective To investigate the effect of age and gender on anterior cervical plating (ACP) in light of radiological findings. Methods The degree of lordosis angle was calculated using the posterior tangent method both in early (one month) and late postoperative period (6–12 months) and the difference between pre- and post-operative values was accepted as the degree of lordosis correction. The results were compared between patients below and over 45 years and between males and females. Interbody height was measured as the distance between the upper-end plate of the superior vertebral body and the lower-end plate of the inferior vertebral body. Based on this distance, both segmental height loss (mm) and the degree of total height loss (%) were calculated and were compared between groups. Results The mean degree of lordosis correction was higher in the ACDF-CP group than in the ACDF-CA group and was higher in women than men in the ACDF-CP group compared to the control group. Moreover, the mean degree of lordosis correction was higher in patients aged below 45 years compared to patients aged over 45 years. Similarly, segmental height loss was lower in the ACDF-CP group compared to the ACDF-CA group, in women compared to men, and in patients aged below 45 years compared to patients aged over 45 years. Conclusions The implementation of ACDF-CP provided more beneficial outcomes compared to ACDF-CA with regard to lordosis correction and graft height loss. Moreover, ACDF-CP provided more favorable effects in women than in men and in patients aged below 45 years than in patients aged over 45 years.

Measurement of Lumbar Lordosis: A Comparison of 2 Alternatives to the Cobb Angle

ObjectiveThe purpose of this study was to compare 2 alternative methods, the radiologic Harrison Posterior Tangent Method (HPTM) and the nonradiologic Spinal Mouse (SM), to the Cobb angle for measuring lumbar lordosis. MethodsSixteen participants with previously existing lateral lumbopelvic radiographs underwent nonradiographic lordosis assessment with a Spinal Mouse. Then 2 investigators analyzed each radiograph twice using the Harrison Posterior Tangent Method and Cobb angle. Correlations were analyzed between HPTM, the Cobb angle, and SM using the Spearman rank correlation coefficient; intraexaminer and interexaminer agreement were analyzed for HPTM and the Cobb angle using intraclass correlation coefficients. ResultsThe HPTM correlated highly with the Cobb angle (Spearman ρ = 0.936, P < .001); SM had moderate to strong correlations with the Cobb angle (ρ = 0.737, P = .002) and HPTM (ρ = 0.707, P = .003). Intraexaminer and interexaminer agreement for the Cobb angle and HPTM were excellent (all intraclass correlation coefficients > 0.90). One participant had slight kyphosis according to HPTM and SM analyses (which consider the entire lumbar region), whereas the Cobb angle, based only on L1 and L5, reported mild lordosis for that participant. ConclusionIn this sample, HPTM measurements showed high correlation with the commonly used Cobb angle, but this method requires more time and effort, and normal values have not been established. The SM may be an alternative when radiographs are inappropriate, but it measures soft tissue contours rather than lordosis itself.

Efficacy of Modified Cervical and Shoulder Retraction Exercise in Patients With Loss of Cervical Lordosis and Neck Pain.

ObjectiveTo explore if the modified cervical and shoulder retraction exercise program restores cervical lordosis and reduces neck pain in patients with loss of cervical lordosis.MethodsThis study was a retrospective analysis of prospectively collected data. Eighty-three patients with loss of cervical lordosis were eligible. The eligible patients were trained to perform the modified cervical and shoulder retraction exercise program by a physiatrist, and were scheduled for a follow-up 6 to 8 weeks later to check the post-exercise pain intensity and lateral radiograph of the cervical spine in a comfortable position. The parameters of cervical alignment (4-line Cobb’s angle, posterior tangent method, and sagittal vertical axis) were measured from the lateral radiograph.ResultsForty-seven patients were included. The mean age was 48.29±14.47 years. Cervical alignment and neck pain significantly improved after undergoing the modified cervical and shoulder retraction exercise program (p≤0.001). The upper cervical lordotic angle also significantly improved (p=0.001). In a subgroup analysis, which involved dividing the patients into two age groups (<50 years and ≥50 years), the change of the sagittal vertical axis was significantly greater in the <50 years group (p=0.021).ConclusionThe modified cervical and shoulder retraction exercise program tends to improve cervical lordosis and neck pain in patients with loss of cervical lordosis.

Progression of local kyphosis after conservative treatment for compressive cervical spine fracture with spinal cord injury

IntroductionCompressive-flexion type cervical spine fracture is typically accompanied by apparent dislocation of the facet joints, undesirable cervical alignment, and devastating neurological dysfunction, which provides strong rationale for rendering prompt operative treatment. However, the validity of conservative treatment for compressive-flexion cervical spine injury in cases with preserved congruity of the facet joints has yet to be elucidated. The purpose of this study is to evaluate the long-term outcome of cervical alignment following conservative treatment for compressive-flexion cervical spine injury with preserved congruity of the facet joints.MethodsA total of 662 patients who experienced spinal cord injury from 2007 to 2017 were included and underwent retrospective review in a single institute. Thirteen patients were identified as receiving conservative therapy following compressive-flexion cervical spine fractures with spinal cord injury. Clinical and radiological results were collected, including vertical fractures of the vertebral column, laminar fractures, progression of local kyphosis, and neurological status. The degree of the local cervical kyphosis was evaluated with two methods: the posterior tangent method and the endplate method.ResultsAll 13 patients were male, and the mean age at the time of injury was 28.4 years. The mean follow-up period was 3 years. Although none of the patients presented neurological deterioration after the injury, the degree of local kyphosis was increased at the time of final follow-up compared to what was observed at the time of injury. Patient age at the time of injury and concurrent vertical fracture of vertebral body could have been influencing factors for the progression of the kyphosis. While laminar fracture affected the kyphosis at the time of injury, it was not a strong influencing factor of the overall progression of local kyphosis.ConclusionsThe conservative option for the compressive-flexion cervical injury allowed us to treat without exacerbating neurological symptoms as long as the facet joints are preserved. However, in terms of cervical alignment, surgical stabilization may have been desirable for these patients. Notably, the younger patients and the patients with vertical fracture of the cervical vertebral column in this type of injury required closer observation to help prevent the progression of local kyphosis.

Cervical lordosis in asymptomatic individuals: a meta-analysis

BackgroundCervical lordosis has important clinical and surgical implications. Cervical spine curvature is reported with considerable variability in individual studies. The aim of this study was to examine the existence and extent of cervical lordosis in asymptomatic individuals and to evaluate its relationship with age and gender.MethodsA comprehensive literature search was conducted in several electronic databases. Study selection was based on pre-determined eligibility criteria. Random effects meta-analyses were performed to estimate the proportion of asymptomatic individuals with lordosis and the effect size of cervical lordotic curvature in these individuals which followed metaregression analysis to examine the factors affecting cervical lordosis. Data from 21 studies (15,364 asymptomatic individuals, age 42.30 years [95% confidence interval 36.42, 48.18], 54.2% males) were used in the present study.ResultsIn this population, 63.99% [95% confidence interval 44.94, 83.03] individuals possessed lordotic curvature. Degree of lordotic curvature differed by method of measurement; 12.71° [6.59, 18.84] with Cobb C2–C7 method and 18.55° [14.48, 22.63] with posterior tangent method. Lordotic curvature was not significantly different between symptomatic and asymptomatic individuals but was significantly higher in males in comparison with females. Age was not significantly associated with lordotic cervical curvature.ConclusionMajority of the asymptomatic individuals possesses lordotic cervical curvature which is higher in males than in females but have no relationship with age or symptoms.

The Reliabilities of Several Measurement Methods of Cervical Sagittal Alignment in Cases with Cervical Spine Rotation Using X-ray Findings in Cervical Spine Disorders.

Introduction Several measurement methods designed to provide an understanding of cervical sagittal alignment have been reported, but few studies have compared the reliabilities of these measurement methods. The purpose of the present study was to investigate the intraexaminer and interexaminer reliabilities of several cervical sagittal alignment measurement methods and of the rotated cervical spine using plain lateral cervical spine X-rays of patients with cervical spine disorders. Methods Five different measurement methods (Borden's method; Ishihara index method (Ishihara method); C2-7 Cobb method (C2-7 Cobb); posterior tangent method: absolute rotation angle C2-7 (ARA); and classification of cervical spine alignment (CCSA)) were applied by seven examiners to plain lateral cervical spine X-rays of 20 patients (10 randomly extracted cases from a rotated cervical spine group and 10 from a nonrotated group) with cervical spine disorders. Case 1 and Case 2 intraclass correlation coefficients (ICCs) were used to analyze intraexaminer and interexaminer reliabilities. The necessary number of measurements and the necessary number of examiners were also determined. The target coefficient of correlation was set at ≥0.81 (almost perfect ICC). Results In both groups, an ICC(1, 1) ≥ 0.81 was obtained with Borden's method, the Ishihara method, C2-7 Cobb, and ARA by all examiners. The necessary number of measurements was 1. With CCSA, a kappa coefficient of at least 0.9 was obtained. In both groups, with Borden's method, the Ishihara method, C2-7 Cobb, and ARA, the ICC(2, 1) was ≥0.9, indicating that the necessary number of examiners was 1. The standard error of measurement (SEM) was lowest with Borden's method, and the Ishihara method and C2-7 Cobb had almost the same values. Conclusions Among cervical sagittal alignment measurement methods for cervical spine disorders, regardless of cervical spine rotation, Borden's method, Ishihara method, and C2-7 Cobb offer stronger reliability in terms of the ICC and SEM.

Non-surgical improvement of cervical lordosis is possible in advanced spinal osteoarthritis: a CBP® case report.

[Purpose] To present a case of the non-surgical improvement in cervical kyphosis in a patient with history of cervical spine trauma and advanced osteoarthritis. [Subject and Methods] A 38 year old male presented with a chief complaint of chronic neck pain that was not substantially relieved by recent previous traditional physiotherapy and chiropractic manipulation. The cervical radiograph demonstrated a cervical hypolordosis of 5° as measured by the Harrison posterior tangent method from C2–C7. There was a 15° kyphosis at C4–C6 with advanced degenerative changes consistent with previous spine trauma. The patient was treated by CBP® methods incorporating cervical extension traction, extension exercises, and spinal manipulation for 30 sessions over an 18 week period. [Results] After the treatment sessions, there was a substantial (27°) increase in global C2–C7 lordosis, and 5° decrease in C4–C6 degenerative kyphosis corresponding to the reduction in neck pain and disability, and an improvement in overall health status as indicated on the SF-36 health questionnaire. [Conclusion] Although degenerative spondylosis of the cervical spine will have physical limitations to non-surgical correction, this case serves as an example that it is possible to reduce degenerative kyphosis and increase global cervical lordosis corresponding to health improvements in these patients.

Test-retest reliability and validity of a motion capture (MOCAP) system for measuring thoracic and lumbar spinal curvatures and sacral inclination in the sagittal plane.

To evaluate the test-retest reliability and validity of the MOCAP system for measuring spinal sagittal thoracic and lumbar curvatures and sacral inclination in a standing posture. Twenty-five male adults were evaluated on lateral standing radiographs. The thoracic and lumbar curvatures were calculated by Harrison's posterior tangent method. The sacral inclination was defined as the angle between the tangent line of the sacral and vertical plane. In addition, MOCAP was used to calculate the spinal curvatures and sacral inclination. The thoracic and lumbar spine and sacral inclination demonstrated excellent reliability, with mean ICCs levels greater than 0.980 and low CVs (mean: 2.15%). Systematic biases were not significant and were very near 0, and the mean standard errors were 0.257∘. ANOVA of the radiographic and MOCAP measures did not report any statistically significant differences in the comparisons. The systematic biases and mean random errors were lower than 1∘, with CVs lower than 5% and mean ICCs higher than 0.90 between sessions. The MOCAP system delivered consistently reliable and valid results for standing curvatures compared with a radiographic technique. This system could be used with confidence in research and clinical environments for sagittal spinal curvature measurements.

The Assessment of Upright Cervical Spinal Alignment Using Supine MRI Studies.

This is a prospective, single-centre study. The purpose of this study is researching whether there is a correlation or not between the cervical alignment in the examinations of magnetic resonance imaging (MRI) in lying position and the alignment in the cervical direct radiography and whether the cervical alignment in standing position could be estimated or not through MRI measurements in the supine position. Cervical spinal alignment is a parameter required for deciding the surgical procedure particularly in patients with cervical myelopathy and deformity. However, cervical alignment angles change according to lying and standing positions. Therefore, the direct standing radiograph is taken as basis for this examination. Cervical alignments were measured with 3 different methods with the standing lateral radiographies and lying MRI of 51 patients with cervical disorder. A high correlation was found between the measurements in standing and lying positions for the spinal alignments measured through the Cobb angle and posterior tangent method. It was found that standing Cobb angle (in plain graphy)=Cobb angle (in MRI)×0.489+7.13 and posterior tangent angle (in plain graphy)=posterior tangent angle (in MRI)×0.54+9.37. It is possible to estimate the spinal alignment in standing position with the measurements of cervical spinal alignment in the MRI at supine position. And this may render having cervical graphy in standing position unnecessary.

Test-retest reliability and validity of a motion capture (MOCAP) system for measuring thoracic and lumbar spinal curvatures and sacral inclination in the sagittal plane

To evaluate the test-retest reliability and validity of the MOCAP system for measuring spinal sagittal thoracic and lumbar curvatures and sacral inclination in a standing posture. Twenty-five male adults were evaluated on lateral standing radiographs. The thoracic and lumbar curvatures were calculated by Harrison's posterior tangent method. The sacral inclination was defined as the angle between the tangent line of the sacral and vertical plane. In addition, MOCAP was used to calculate the spinal curvatures and sacral inclination. The thoracic and lumbar spine and sacral inclination demonstrated excellent reliability, with mean ICCs levels greater than 0.980 and low CVs (mean: 2.15%). Systematic biases were not significant and were very near 0, and the mean standard errors were 0.257∘. ANOVA of the radiographic and MOCAP measures did not report any statistically significant differences in the comparisons. The systematic biases and mean random errors were lower than 1∘, with CVs lower than 5% and mean ICCs higher than 0.90 between sessions. The MOCAP system delivered consistently reliable and valid results for standing curvatures compared with a radiographic technique. This system could be used with confidence in research and clinical environments for sagittal spinal curvature measurements.

A Radiographic Analysis of Cervical Sagittal Alignment in Adolescent Idiopathic Cervical Kyphosis.

The aim of this study was to analyze the radiologic features of adolescent idiopathic cervical kyphosis. There are few previous reports about radiographic analysis of cervical sagittal alignment of adolescent idiopathic cervical kyphosis. A new method was proposed in this article to evaluate the severity of cervical kyphosis. A total of 41 adolescent patients with cervical kyphosis were reviewed. Several angles were measured from the radiographs utilizing the 2-line Cobb method and Harrison posterior tangent method. Ishihara's Curvature Index (CI), Kyphosis Index (KI), kyphosis levels, and the apex of the kyphosis were also measured. The results showed that the apex of the kyphosis is located at the posterior-superior edge of C4 (70.7%) and C5 (29.3%). C2-C7 angles ranged from 4.7 to 71.3 degrees (36.2±13.6 degrees) and from 9.8 to 83.1 degrees (36.4±15.1 degrees) in the above 2 methods, respectively. Local angles of kyphotic area ranged from 21.8 to 96.3 degrees (50.5±23.7 degrees) in 2-line Cobb method and from 19.8 to 105.6 degrees (52.0±19.5 degrees) in Harrison posterior tangent method. CI and KI ranged from 8.6 to 79.8 (36.8±16.7) and 15.2 to 141.9 (50.6±23.7), respectively. Statistical analysis showed that there was significant positive correlation between KI and kyphosis angle. In adolescent idiopathic cervical kyphosis, the alteration of the sagittal profile only occurs on partial cervical alignment rather than the whole cervical spine. The apex of the kyphosis locates at posterior-superior edge of the vertebrae. It seems that KI can accurately depict the severity of cervical kyphosis.

ANALYSIS OF INTERVERTEBRAL ANGULATIONS AND MUSCULOSKELETAL SYMPTOMS OF THE SPINE IN THE MILITARY AIRCREWS OF TAIWAN

Background: The purpose of this study is to investigate the prevalence of neck and low back discomfort and its association with intervertebral angulations of cervical and lumbar during neutral and flexion among aircrews. Methods: There were 283 subjects participating in this survey. All participants finished one questionnaire each regarding complaints about musculoskeletal symptoms, and three sagittal plane radiographs. The measurements of intervertebral angulations were completed using the Cobb method for lumbar spine and the Harrison posterior tangent method for the cervical spine. Results: In the questionnaire, 26.5% subjects self-reported neck discomfort and 33.2% subjects self-reported low back discomfort. Based on categorization by self-reported complaints, there was significant decrease in two intervertebral flexion angles of the Discomfort group than those of the Regular group, including C3/C4 and C2/C7. Based on categorization by radiological diagnoses, the abnormal group revealed significant decreases in the regular range of motion from neutral to flexion at C3/C4 segment. Lordotic angles between L1 and L5 were also found to be significantly different between the Discomfort group and the Regular group. Conclusions: A high prevalence of neck and low back discomfort among the aircrews is revealed and needs more suitable intervention. A certain level of association between spinal discomfort and the intervertebral angulations of the lumbar spine and the cervical spine in aircrews was found when compared to the normal group.

An assessment of the most reliable method to estimate the sagittal alignment of the cervical spine: analysis of a prospective cohort of 138 cases.

OBJECTIVE Although there is increasing recognition of the importance of cervical spinal sagittal balance, there is a lack of consensus as to the optimal method to accurately assess the cervical sagittal alignment. Cervical alignment is important for surgical decision making. Sagittal balance of the cervical spine is generally assessed using one of two methods; namely, measuring the angle between C-2 and C-7, and drawing a line between C-2 and C-7. Here, the best method to assess sagittal alignment of the cervical spine is investigated. METHODS Data from 138 patients enrolled in a randomized controlled trial (Procon) were analyzed. Two investigators independently measured the angle between C-2 and C-7 by using Harrison's posterior tangent method, and also estimated the shape of the sagittal curve by using a modified Toyama method. The mean angles of each quantitative assessment of the sagittal alignment were calculated and the results were compared. The interrater reliability for both methods was estimated using Cronbach's alpha. RESULTS For both methods the interrater reliability was high: for the posterior tangent method it was 0.907 and for the modified Toyama technique it was 0.984. For a lordotic cervical spine, defined by the modified Toyama method, the mean angle (defined by Harrison's posterior tangent method) was 23.4° ± 9.9° (range 0.4°-52.4°), for a kyphotic cervical spine it was -2.2° ± 9.2° (range -16.1° to 16.9°), and for a straight cervical spine it was 10.5° ± 8.2° (range -11° to 36°). CONCLUSIONS An absolute measurement of the angle between C-2 and C-7 does not unequivocally define the sagittal cervical alignment. As can be seen from the minimum and maximum values, even a positive angle between C-2 and C-7 could be present in a kyphotic spine. For this purpose, the modified Toyama method (drawing a line from the posterior inferior part of the vertebral body of C-2 to the posterior upper part of the vertebral body of C-7 without any measurements) is a better tool for a global assessment of cervical sagittal alignment. Clinical trial registration no.: ISRCTN41681847 ( https://www.isrctn.com ).

The evaluation of cervical spinal angle in patients with acute and chronic neck pain.

Clinicians associate the changes in cervical lordosis with neck pain, but there is no clear consensus on this. We aimed to investigate the relationships of cervical angles, neck pain, disability, and the psychological status of the patients with acute and chronic neck pain. A total of 110 patients with neck pain were included in this study. Demographic and clinical characteristics of the patients were recorded. The lordosis angle was determined by the posterior tangent method. A visual analog scale (VAS), the Neck Disability Index (NDI), and the Hospital Anxiety and Depression (HAD) scale were administered to all patients. The mean cervical lordosis angle was 23.10 ± 8.07 degrees. A statistically negative correlation was detected between cervical angle and duration of disease (P < 0.05). The cervical angle of the acute neck pain group was higher than that of the chronic pain group (P < 0.05). There was no difference between the acute and chronic neck pain groups with respect to VAS, NDI, and HAD scores (P > 0.05). We found that the cervical angle was significantly lower in chronic neck pain patients when compared to acute patients, and patients with higher pain scores had more severe disability and that disability increased with the duration of disease.

The Reliabilities of Radiographic Measurements of Cervical Sagittal Alignment in Ankylosing Spondylitis.

This is a prospective study design. To test the interobserver and intraobserver reliabilities of 5 specific measures of global cervical sagittal alignment in patients with ankylosing spondylitis (AS), and to suggest a better means of measuring cervical sagittal alignment. The intraobserver and interobserver reliabilities of several different methods of measuring cervical lordosis have been reported. However, they have not been studied till yet in patients with AS. Interobserver and intraobserver reliabilities of 5 specific measures of cervical lordosis were evaluated in patients with AS. Eighty patients with AS were allocated to a nonankylosis or an ankylosis group, and the reliabilities of the Cobb C1-C7, Cobb C2-C7, centroid, posterior tangent, and Ishihara index methods were evaluated. The intraclass and interclass correlation coefficients (ICCs) of all 5 methods were generally high. For the 80 study subjects, ICCs were ≥0.84 (excellent) for all 5 radiographic methods. However, comparison of the ICCs, 95% confidence intervals, and mean absolute differences (MAD) between groups with varying degrees of ankylosis showed that the reliability of lordosis measurements decreased as the severity of ankylosis increased. The 5 methods consistently demonstrated higher ICCs for both interobserver and intraobserver comparisons in the nonankylosis group. However, in the ankylosis group, the Cobb C1-C7 method demonstrated high ICCs for both interobserver and intraobserver comparisons, whereas the other 4 methods had high ICCs only for intraobserver comparisons. The intraobserver MADs were similar for the 5 methods (2.4-3.9), but the interobserver MADs of measurement methods in both groups showed low measurement reliability except for the Cobb C1-C7 methods. This study provides a reliability analysis of different cervical lordosis measurement methods in AS, and shows that the Cobb C1-C7 method provides a reliable means for measuring cervical lordosis in AS.

Reliability of cervical lordosis measurement techniques on long-cassette radiographs.

Lateral radiographs are commonly used to assess cervical sagittal alignment. Three assessment methods have been described and are commonly utilized in clinical practice. These methods are described for perfect lateral cervical radiographs, however in everyday practice radiograph quality varies. The aim of this study was to compare the reliability and reproducibility of 3 cervical lordosis (CL) measurement methods. Forty-four standing lateral radiographs were randomly chosen from a lateral long-cassette radiograph database. Measurements of CL were performed with: Cobb method C2-C7 (CM), C2-C7 posterior tangent method (PTM), sum of posterior tangent method for each segment (SPTM). Three independent orthopaedic surgeons measured CL using the three methods on 44 lateral radiographs. One researcher used the three methods to measured CL three times at 4-week time intervals. Agreement between the methods as well as their intra- and interobserver reliability were tested and quantified by intraclass correlation coefficient (ICC) and median error for a single measurement (SEM). ICC of 0.75 or more reflected an excellent agreement/reliability. The results were compared with repeated ANOVA test, with p<0.05 considered as significant. All methods revealed excellent intra- and interobserver reliability. Agreement (ICC, SEM) between three methods was (0.89°, 3.44°), between CM and SPTM was (0.82°, 4.42°), between CM and PTM was (0.80°, 4.80°) and between PTM and SPTM was (0.99°, 1.10°). Mean values CL for a CM, PTM, SPTM were 10.5°±13.9°, 17.5°±15.6° and 17.7°±15.9° (p<0.0001), respectively. The significant difference was between CM vs PTM (p<0.0001) and CM vs SPTM (p<0.0001), but not between PTM vs SPTM (p>0.05). All three methods appeared to be highly reliable. Although, high agreement between all measurement methods was shown, we do not recommend using Cobb measurement method interchangeably with PTM or SPTM within a single study as this could lead to error, whereas, such a comparison between tangent methods can be considered.