Posterior Tangent Method Research Articles

Cross-sectional study of neck pain and cervical sagittal alignment in air force pilots.

There is a high prevalence of neck pain in air force pilots; however, the causes are not clear and are considered work-related. Kyphotic changes in the cervical spine have been known to cause neck pain. In this study, we investigated the association between neck pain and cervical kyphosis in air force pilots. This is a cross-sectional study of 63 Republic of South Korea Air Force pilots. We examined the C2-7 absolute rotation angle (ARA) using the posterior tangent method and other radiologic parameters on whole spine lateral radiographs. We divided the participants into a neck pain group (N = 32) and no neck pain group (N = 31), and subsequently analyzed the difference in radiographic parameters and clinical data between the two groups. There were no significant differences found in age, body mass index, total flight time, or aerobic or anaerobic exercise between the neck pain and control groups. The fighter pilots had higher 1-yr prevalence of neck pain than nonfighter pilots (84.4% vs. 15.6%). The lower C2-7 ARA (OR = 0.91, 95% CI 0.846, 0.979) and fighter type aircrafts (OR = 3.93, 95% CI 1.104, 13.989) were associated with neck pain. Fighter pilots experienced neck pain more frequently than the nonfighter pilots. Those fighter pilots suffering from neck pain were shown to have more kyphotic changes in the cervical spine than control pilots through evaluation of whole spine lateral radiographs using the posterior tangent method. These key findings suggest that the forces involved in flying a fighter type aircraft may affect cervical alignment and neck pain.

Retrospective observational comparative study of Hemilaminectomy versus Laminectomy for intraspinal tumour resection; Shorter Stays, Lower Analgesic Usage and Less Kyphotic Deformity

Introduction. Intraspinal tumours are rare and principally managed surgically. Laminectomy, employed for access to the spinal canal, destroys the posterior tension band leading to a risk of kyphosis. Hemilaminectomy as an alternative may be less destructive, potentially reducing the risk of deformity and causing less post-operative pain. Method. We investigated this hypothesis by retrospectively reviewing a case series of 56 surgeries for a disparate and unselected group of intraspinal tumours utilizing a laminectomy or hemilaminectomy approach. Results. No difference was found in length of operation, completeness of resection, complication rate and Frankel-score improvements. Hemilaminectomy (n = 22) is associated with reduced hospital stay (post-op days) 4.5 (2–6) versus 6 (3–8), (p = 0.026, Mann–Whitney), and a reduction in post-operative morphine use (mg) 10 (3.5–28) versus 30 (10–90), (p = 0.005, Mann–Whitney).Post-operative kyphosis was measured with the Harrison posterior tangent method on T2-weighted sagittal MR images. The average change in kyphosis angle was greater in the laminectomy group compared with the hemilaminectomy group, 3.6 (0.8–6.2) versus 0.4 (-0.2–1.2), statistically significant (p = 0.004, Mann–Whitney). Conclusion. Hemilaminectomy is as effective an access procedure for the resection of unselected intraspinal tumours as laminectomy, but is associated with shorter post-operative stays, lower analgesic requirements and less post-operative kyphosis.

Apoptosis of endplate chondrocytes in post-laminectomy cervical kyphotic deformity

The present study was performed to establish an animal model of cervical kyphosis after laminectomy (C2-C5), and to determine the role of endplate chondrocytes apoptosis in cervical kyphosis after laminectomy. Twenty-four 3-month-old sheep were randomly divided into two groups: the laminectomy group (n = 12), and the control group (n = 12). The cervical spine alignment was evaluated on a lateral cervical spine X-ray using Harrison's posterior tangent method before surgery and at follow-up. Cartilaginous endplate chondrocyte apoptosis was confirmed using transmission electron microscopy and terminal deoxyribonucleotidyl transferase (TdT)-mediated dUTP nick-end labelling. The mean preoperative cervical curvature (C2-5) in the surgery group was -15.8°. The cervical curvature was 19.1° at 3 months post-operation and decreased to 20.2° at the final follow-up postoperatively. The cervical curvature was significantly decreased in the laminectomy group compared with the control group at the last follow-up (P < 0.001), which was a direct indication of kyphotic change. The incidence of apoptotic cells in the surgery group was significantly higher at the 3- and 6-month follow-up than the incidence in the control group. The frequency of endplate chondrocyte apoptosis in the laminectomy group was significantly higher than in the control group, indicating that chondrocyte apoptosis may play a pivotal role in the progress of post-laminectomy cervical kyphosis.

Reproducibility of Radiographic Measurements for Subaxial Cervical Spine Trauma

Radiographic measurement study. To assess the interobserver reliability of radiographic measurements for subaxial cervical spine trauma; to compare the reliability of measurements made on computed tomography (CT) versus those made using plain radiographs. Despite the importance of imaging and classification of subaxial cervical injuries, the persistent lack of a uniform measurement protocol remains an obstacle. Recently, the Spine Trauma Study Group published a proposal for a standardized set of measurement techniques for the radiographic evaluation of subaxial cervical spine trauma. While a worthwhile venture, the observer error of these methods was not tested. Lateral cervical plain radiographs and CT images of 30 patients who sustained a broad spectrum of subaxial cervical spine injuries were distributed to surgeons. Participants were asked to measure kyphosis, translation, vertebral body height loss, and facet joint apposition. Each rater was provided with a pictorial diagram illustrating the prescribed measurement technique. All measurements were made using plain radiographs and CT images with the exception of facet joint apposition, which was assessed using only CT. Reliability was examined by calculating the ICC and Pearson correlation coefficients. RESULTS.: Vertebral body translation was the most reproducible method on both CT images and plain radiographs. Kyphosis measurements were less reproducible, though the endplate method demonstrated superior reliability to the posterior tangent method. Plain radiographic measurement of anterior vertebral body height loss demonstrated moderate reliability while all other height loss measurements were found to show poor reliability. Facet joint apposition measurement demonstrated poor reproducibility. Despite a consensus regarding their importance in directing treatment, radiographic measurements for subaxial cervical spine trauma demonstrate inconsistent reliability. Even in the idealized setting used in this investigation, there was limited agreement between observers. Although translation and kyphosis showed satisfactory reproducibility, results for vertebral body height loss and facet joint apposition were unreliable. On the basis of these findings, it may be more appropriate to describe facet joint apposition binomially as "present" or "not present" instead of a numerical value; vertebral body height loss may be more appropriately characterized in quaternary terms, such as less than 25%, 25% to 50%, 50% to 75%, and more than 75%. Though simpler, such descriptions would need to be validated in future studies.

Reliability of Lumbar Lordosis Measurement in Patients With Spondylolisthesis

A radiologic analytical study. To compare the reliability of lumbar lordosis (LL) measurement in cases of spondylolisthesis using the Cobb, vertebral centroid, and posterior tangent methods. Interobserver and intraobserver reliabilities of the several different types of lumbar curvature analysis have been reported using various methods for measurement; however, in patients with spondylolisthesis, it has not been studied till yet. A radiologic analytical study was performed in 50 patients who had spondylolisthesis (28 at L4-L5, 22 at L5-S1) with lysis in the lumbar spine. All patients had instability of more than 10 degrees on the lumbar spine flexion and extension radiogram. A total of 26 patients who presented for backache without spondylolisthesis were considered as control group. Three observers measured the global and segmental angle for LL using various methods for measuring the LL using the Cobb, vertebral centroid, and Harrison's posterior tangent methods. All measurements were done by each of the observers on the same computer by keeping at least 2 weeks of interval between 2 sets of measurements. The interobserver and intraobserver reliability was calculated among all the 3 observers' 2 sets of measurements by using the inter- and intraclass correlation coefficient (ICC) test on SPSS program. Five global and 17 segmental angles measured overall. Results showed an excellent ICC (>0.7) while measuring the global LL using any method, the Cobb (T12-S1 or L1-L5), vertebral centroid, and Harrison's posterior tangent (T12-S1 or L1-L5) methods, in both subject and control groups. Similarly measuring the segmental angles, it exhibited excellent intraclass correlation (ICC, >0.7) coefficient by using all 3 methods for all segmental angles in both groups. However, interclass correlation coefficient was excellent (ICCs, >0.7) in both global as well as segmental angles for vertebral centroid and posterior tangent methods in subject and control groups, but it was poor or fair for the Cobb methods in segmental angles and good or excellent in global angles. Measuring the segmental angles, standard error of mean (SEM) was <2 degrees at all the levels by all methods in both subject and control group except the L4-L5-S1 level by centroid method in subject group where SEM >2 degrees was found. Posterior tangent method should be used for the global and segmental angle analysis for the LL in cases with spinal instability because of (a) higher correlation coefficient for segmental angle measurements; (b) lower SEM at the instability level than the centroid method despite similar correlation coefficients; and (c) similar to the engineering analysis.

Observer Variability of Radiographic Measurements of C2 (Axis) Fractures

Radiographic measurement study. To assess the inter- and intraobserver reliability of angulation and displacement measurements for odontoid fractures and traumatic spondylolistheses (Hangman fractures) of C2, and to compare the reliability of measurements made on computerized tomography (CT) versus those made using plain radiographs. Measurements of various parameters of C2 injuries can influence treatment decision making. However, there is a paucity of data regarding the reproducibility of these measurements. A series of 19 cases, representing 10 odontoid fractures and 9 Hangman fractures, were prepared and distributed to surgeon raters on 2 occasions. Each rater was provided with a pictorial diagram illustrating the prescribed measurement technique(s). For odontoid fractures, raters were asked to measure angulation, translation, atlanto-dens interval (ADI), and posterior ADI. For Hangman fractures, angulation and C2-C3 translation were assessed. Measurements were made using plain films and CT images. Reliability was reflected by calculation of intraclass correlation coefficients and Pearson correlation coefficients. Intrarater analysis for both odontoid and Hangman fractures demonstrated high reproducibility. Interobserver evaluation showed that the posterior ADI was the most reproducible method, whereas all other measurements for odontoid fractures were found to have poor reproducibility. For Hangman fractures, the endplate method of angulation measurement had higher interrater reproducibility than the posterior tangent method. The interrater reliability for C2-C3 translation using plain films was higher than for measurements made using CT images. Despite widespread acceptance of their importance, radiographic measurements for C2 fractures have, at best, only moderate reliability. Even in the ideal situation created in this study, there is limited agreement. Further work to substantiate the importance and improve the reliability of these measurement parameters is needed.

Effective lordosis: analysis of sagittal spinal canal alignment in cervical spondylotic myelopathy

Analysis of cervical sagittal deformity in patients with cervical spondylotic myelopathy (CSM) requires a thorough clinical and radiographic evaluation to select the most appropriate surgical approach. Angular radiographic measurements, which are commonly used to define sagittal deformity, may not be the most appropriate to use for surgical planning. The authors present a simple straight-line method to measure effective spinal canal lordosis and analyze its reliability. Furthermore, comparisons of this measurement to traditional angular measurements of sagittal cervical alignment are made in regards to surgical planning in patients with CSM. Twenty preoperative lateral cervical digital radiographs of patients with CSM were analyzed by 3 independent observers on 3 separate occasions using a software measurement program. Sagittal measurements included C2-7 angles utilizing the Cobb and posterior tangent methods, as well as a straight-line method to measure effective spinal canal lordosis from the dorsal-caudal aspect of the C2-7 vertebral bodies. Analysis of variance for repeated measures or Cohen 3-way (kappa) correlation coefficient analysis was performed as appropriate to calculate the intra- and interobserver reliability for each parameter. Discrepancies in angular and effective lordosis measurements were analyzed. Intra- and interobserver reliability was excellent (intraclass coefficient > 0.75, kappa > 0.90) utilizing all 3 techniques. Four discrepancies between angular and effective lordotic measurements occurred in which images with a lordotic angular measurement did not have lordosis within the ventral spinal canal. These discrepancies were caused by either spondylolisthesis or dorsally projecting osteophytes in all cases. Although they are reliable, traditional methods used to make angular measurements of sagittal cervical spine alignment do not take into account ventral obstructions to the spinal cord. The effective lordosis measurement method provides a simple and reliable means of determining clinically significant lordosis because it accounts for both overall alignment of the cervical spine as well as impinging structures ventral to the spinal cord. This method should be considered for use in the treatment of patients with CSM.

Analysis of accuracy of kyphotic angle measurement for vertebral osteoporotic compression fractures

A reliable and reproducible measurement technique for the sagittal contour in vertebral fractures is paramount to clinical decision-making. This study was designed to determine the most reliable measurement technique in osteoporotic vertebral compression fracture. Fifteen lateral radiographs of thoracic and lumbar fractures were selected and measured on two separate occasions by three spine surgeons using six different measurement techniques (centroid, Harrison posterior tangent method and 4 different types of modified Cobb method). The radiograph quality was assessed and the center beam location was determined. The inter- and intraobserver variance of the Cobb method 4 and the Harrison posterior tangent method were significantly lower than for the other four methods. The intraobserver correlation coefficients were the most consistent using the Cobb method 4 (0.982), followed by the Harrison posterior tangent method (0.953) and Cobb method 1 (0.874). The intraobserver agreement (% of repeated measures within 5° of the original measurement) ranged from 42% to 98% for each technique for all three observers, with the Cobb method 4 showing the best agreement (97.8%) followed by the Harrison posterior tangent method (93.7%). The Cobb method 4 and Harrison posterior tangent method, when applied to measuring the kyphosis, were reliable and had a similar small error range. The Cobb method 4 showed the best overall reliability. The centroid method and the other Cobb methods using a fractured endplate did not produce an accurate result due to inter- and intraobserver differences in determining the baseline.

Answer to the letter to the editor of Dr. D.E. Harrison et al. regarding “The association between cervical spine curvature and neck pain” (D. Grob et al., Eur Spine J, published online Nov 18, 2006)

Answer to the letter to the editor of Dr. D.E. Harrison et al. regarding “The association between cervical spine curvature and neck pain” (D. Grob et al., Eur Spine J, published online Nov 18, 2006)

The association between cervical spine curvature and neck pain.

Degenerative changes of the cervical spine are commonly accompanied by a reduction or loss of the segmental or global lordosis, and are often considered to be a cause of neck pain. Nonetheless, such changes may also remain clinically silent. The aim of this study was to examine the correlation between the presence of neck pain and alterations of the normal cervical lordosis in people aged over 45 years. One hundred and seven volunteers, who were otherwise undergoing treatment for lower extremity problems in our hospital, took part. Sagittal radiographs of the cervical spine were taken and a questionnaire was completed, enquiring about neck pain and disability in the last 12 months. Based on the latter, subjects were divided into a group with neck pain (N = 54) and a group without neck pain (N = 53). The global curvature of the cervical spine (C2-C7) and each segmental angle were measured from the radiographs, using the posterior tangent method, and examined in relation to neck complaints. No significant difference between the two groups could be found in relation to the global curvature, the segmental angles, or the incidence of straight-spine or kyphotic deformity (P > 0.05). Twenty-three per cent of the people with neck pain and 17% of those without neck pain showed a segmental kyphosis deformity of more than 4 degrees in at least one segment--most frequently at C4/5, closely followed by C5/6 and C3/4. The average segmental angle at the kyphotic level was 6.5 degrees in the pain group and 6.3 degrees in the group without pain, with a range of 5-10 degrees in each group. In the group with neck pain, there was no association between any of the clinical characteristics (duration, frequency, intensity of pain; radiating pain; sensory/motor disturbances; disability; healthcare utilisation) and either global cervical curvature or segmental angles. The presence of such structural abnormalities in the patient with neck pain must be considered coincidental, i.e. not necessarily indicative of the cause of pain. This should be given due consideration in the differential diagnosis of patients with neck pain.

Determining the Relationship Between Cervical Lordosis and Neck Complaints

To investigate the presence of a "functionally normal" cervical lordosis and identify if this and the amount of forward head posture are related to neck complaints. Using the posterior tangent method, an angle of cervical lordosis was measured from C2 through C7 vertebrae on 277 lateral cervical x-rays. Anterior weight bearing was measured as the horizontal distance of the posterior superior body of the C2 vertebra compared to a vertical line drawn superiorly from the posterior inferior body of the C7 vertebra. The measurements were sorted into 2 groups, cervical complaint and noncervical complaint groups. The data were then partitioned into age by decades, sex, and angle categories. Patients with lordosis of 20 degrees or less were more likely to have cervicogenic symptoms (P < .001). The association between cervical pain and lordosis of 0 degrees or less was significant (P < .0001). The odds that a patient with cervical pain had a lordosis of 0 degrees or less was 18 times greater than for a patient with a noncervical complaint. Patients with cervical pain had less lordosis and this was consistent over all age ranges. Males had larger median cervical lordosis than females (20 degrees vs 14 degrees) (2-sided Mann-Whitney U test, P = .016). When partitioned by age grouping, this trend is significant only in the 40- to 49-year-old range (2-sided Mann-Whitney U test, P < .01). We found a statistically significant association between cervical pain and lordosis < 20 degrees and a "clinically normal" range for cervical lordosis of 31 degrees to 40 degrees. Maintenance of a lordosis in the range of 31 degrees to 40 degrees could be a clinical goal for chiropractic treatment.

Increasing the cervical lordosis with chiropractic biophysics seated combined extension-compression and transverse load cervical traction with cervical manipulation: nonrandomized clinical control trial

Background Cervical lordosis has been shown to be an important outcome of care; however, few conservative methods of rehabilitating sagittal cervical alignment have been reported. Objective To study whether a seated, retracted, extended, and compressed position would cause tension in the anterior cervical ligament, anterior disk, and muscle structures, and thereby restore cervical lordosis or increase the curvature in patients with loss of the cervical lordosis. Study design Nonrandomized, prospective, clinical control trial. Methods Thirty preselected patients, after diagnostic screening for tolerance to cervical extension with compression, were treated for the first 3 weeks of care using cervical manipulation and a new type of cervical extension-compression traction (vertical weight applied to the subject’s forehead in the sitting position with a transverse load at the area of kyphosis). Pretreatment and posttreatment Visual Analogue Scale (VAS) pain ratings were compared along with pretreatment and posttreatment lateral cervical radiographs analyzed with the posterior tangent method for changes in alignment. Results are compared to a control group of 33 subjects receiving no treatment and matched for age, sex, weight, height, and pain. Results Control subjects reported no change in VAS pain ratings and had no statistical significant change in segmental or global cervical alignment on comparative lateral cervical radiographs (difference in all angle mean values < 1.3°) repeated an average of 8.5 months later. For the traction group, VAS ratings were 4.1 pretreatment and 1.1 posttreatment. On comparative lateral cervical radiographs repeated after an average of 38 visits over 14.6 weeks, 10 angles and 2 distances showed statistically significant improvements, including anterior head weight bearing (mean improvement of 11 mm), Cobb angle at C2-C7 (mean improvement of −13.6°), and the angle of intersection of the posterior tangents at C2-C7 (mean improvement of 17.9°). Twenty-one (70%) of the treatment group subjects were followed for an additional 14 months; improvements in cervical lordosis and anterior weight bearing were maintained. Conclusions Chiropractic biophysics (CBP) technique’s extension-compression 2-way cervical traction combined with spinal manipulation decreased chronic neck pain intensity and improved cervical lordosis in 38 visits over 14.6 weeks, as indicated by increases in segmental and global cervical alignment. Anterior head weight-bearing was reduced by 11 mm; Cobb angles averaged an increase of 13° to 14°; and the angle of intersection of posterior tangents on C2 and C7 averaged 17.9° of improvement.

Further reliability analysis of the Harrison radiographic line-drawing methods: Crossed ICCs for lateral posterior tangents and modified Risser-Ferguson method on APViews

Objective: To determine whether the newly derived interclass and intraclass correlation coefficients (ICCs)would overstate or understate the results from 2 previously published studies, which used better known ICCs that assume nested factors, and to determine mean absolute differences of observers' measurements for 3 previous studies. Study Design: Retrospective analysis of data from 2 blind studies with repeated-measure design. Two newly derived ICCs, appropriate to situations with 3 random factors (patients, examiners, and occasions) that bear a crossed (as opposed to nested) interrelationship, were applied to data from an experiment with random crossed factors. Main Outcome Measures: Observer reliability is determined with ICCs, 95% CIs, and observer error analysis (mean absolute differences of observers' measurements) for angles and distances derived from Harrison's modified Risser-Ferguson line-drawing method on anteroposterior (AP) lumbar and AP cervical radiographic views. Observer error analysis for angles and distances derived from Harrison's posterior tangent method on lateral cervical views was also determined. Results: The majority of ICCs for reliability of line drawing on both AP cervical and AP lumbar radiographs were in the high range; 13 of 16 ICCs were greater than 0.88. The other 3 ICC values (0.61, 0.76, 0.78) concerned determining the sacral base on AP lumbar views. The new ICCs underestimated observer reliability compared with previously published results (intraclass ICCs lower by 0.01-0.02 and interclass ICCs lower by 0.03-0.10). For an error analysis on data from both AP views, the mean absolute differences of observers' measurements were 1.1° to 1.8° for angles and 1.2 mm to 2.3 mm for distances. For the lateral cervical analysis, the observer error was in the interval 0.8° to 3.2° for angles and <1 mm for distances. Conclusions: The ICCs assuming random crossed factors understate reliability compared with previously published ICC results assuming nested factors. Reliability of the Harrison modified Risser-Ferguson method of line-drawing analysis on AP views is in the high range, with the majority of ICCs >0.88. For both the Harrison modified Risser-Ferguson method on AP views and posterior tangent method on lateral cervical views, the mean absolute differences of observers' measurements are small.