Upright static pelvic posture as rotations and translations in 3-dimensional from three 2-dimensional digital images: validation of a computerized analysis.

PURPOSE: The aim of this study was to determine the accuracy in measuring the pelvic orientations of a phantom model using the PosturePrint method. METHODS: In the Université du Québec à Trois-Rivières biomechanics laboratory, Trois-Rivières, Quebec, Canada, a mannequin was fixed on a rotating platform. For a set of 3 photographs (left lateral, anterior to posterior, right lateral) of each position, the mannequin pelvis was placed in 68 different postures on a stand, 61 cm from a wall, in front of a digital camera. The camera was at 83.8 cm in height and at 3.35 m from a calibrated wall grid. Mannequin postures were in 5 degrees of freedom: lateral translation (Tx), lateral flexion (Rz), axial rotation (Ry), flexion-extension (Rx), and anterior-posterior translation (Tz). Average errors were the differences of the positioned postures to the PosturePrint computed values. RESULTS: Mean and SD of computational errors for rotation displacements were Rx = 0.5 degrees +/- 0.8 degrees , Ry = 1.3 degrees +/- 0.8 degrees , and Rz = 0.5 degrees +/- 0.3 degrees , and for translation, Tz = 1.2 +/- 0.6 mm and Tx = 0.9 +/- 0.5 mm. CONCLUSIONS: The PosturePrint system allowed for accurate postural measurement of rotations and translations of a mannequin pelvis. The next step in evaluation of this product would be a reliability study on human subjects.

Validity of a computer postural analysis to estimate 3-dimensional rotations and translations of the head from three 2-dimensional digital images.

OBJECTIVE: The purpose of this study is to describe and evaluate the validity/accuracy of the computerized system PosturePrint for measuring head posture. METHODS: Computer analysis was compared with 125 measured positions of a mannequin head in 5 degrees of freedom. For each mannequin position, 3 digital photographs were obtained (left lateral, anteroposterior, and right lateral) and were processed through the PosturePrint computer system. For the head analysis, a headgear with 3 reflective markers was placed on a subject; and there were additional click-on markers at the ear tragus, upper lip, acromioclavicular joints, and episternal notch. Head postures were calculated as lateral translation (T(x)), lateral flexion (R(z)), axial rotation (R(y)), flexion-extension (R(x)), and anterior-posterior translation (T(z)). For an error analysis, PosturePrint algorithm calculations were compared with the true mannequin head positions. Furthermore, average head posture was determined in student volunteers (n = 40). RESULTS: Mean computational errors were R(x) = 1.3 degrees (SD 0.6 degrees) and T(z) = 1.1 mm (SD 0.5 mm) for sagittal displacements and R(y) = 1.1 degrees (SD 0.7 degrees), R(z) = 0.6 degrees (SD 0.4 degrees), and T(x) = 1.1 mm (SD 0.5 mm) for frontal view displacements. For the normal group, mean head displacements were 1.1 degrees or less for all rotations and 1 mm or less for lateral translations (T(x)); and forward head posture (T(z)) averaged 3 cm. CONCLUSION: From the mannequin positions, small mean errors indicate that the PosturePrint system is accurate. In the future, statistical research determining the correlation between head displacements, neck pain, function, and health status should be performed.

Validation of a computer analysis to determine 3-D rotations and translations of the rib cage in upright posture from three 2-D digital images.

Since thoracic cage posture affects lumbar spine coupling and loads on the spinal tissues and extremities, a scientific analysis of upright posture is needed. Common posture analyzers measure human posture as displacements from a plumb line, while the PosturePrint claims to measure head, rib cage, and pelvic postures as rotations and translations. In this study, it was decided to evaluate the validity of the PosturePrint Internet computer system's analysis of thoracic cage postures. In a university biomechanics laboratory, photographs of a mannequin thoracic cage were obtained in different postures on a stand in front of a digital camera. For each mannequin posture, three photographs were obtained (left lateral, right lateral, and AP). The mannequin thoracic cage was placed in 68 different single and combined postures (requiring 204 photographs) in five degrees of freedom: lateral translation (Tx), lateral flexion (Rz), axial rotation (Ry), flexion-extension (Rx), and anterior-posterior translation (Tz). The PosturePrint system requires 13 reflective markers to be placed on the subject (mannequin) during photography and 16 additional "click-on" markers via computer mouse before a set of three photographs is analyzed by the PosturePrint computer system over the Internet. Errors were the differences between the positioned mannequin and the calculated positions from the computer system. Average absolute value errors were obtained by comparing the exact inputted posture to the PosturePrint computed values. Mean and standard deviation of computational errors for sagittal displacements of the thoracic cage were Rx=0.3+/-0.1 degrees , Tz=1.6+/-0.7 mm, and for frontal view displacements were Ry=1.2+/-1.0 degrees , Rz=0.6+/-0.4 degrees , and Tx=1.5+/-0.6 mm. The PosturePrint system is sufficiently accurate in measuring thoracic cage postures in five degrees of freedom on a mannequin indicating the need for a further study on human subjects.

Radiographic pseudoscoliosis in healthy male subjects following voluntary lateral translation (side glide) of the thoracic spine.

OBJECTIVE: To determine projected Cobb angles associated with trunk list (side shift) posture, hypothesizing that the side shift "scoliotic" curvature would be similar to true scoliotic curvature in the early stages. DESIGN: Anteroposterior (AP) radiographs of volunteers in neutral, in left, and right lateral translations of the thoracic cage (trunk list) were digitized. SETTING: Computer laboratory. PARTICIPANTS: Fifteen healthy male volunteers. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Cobb and Risser-Ferguson angles determined from digitizing vertebral body corners from T12 to L5 on 51 AP lumbar radiographs. RESULTS: Using the horizontal displacement of T12 from S1, subjects could translate an average of 54.0 mm to the left and 52.5 mm to the right. The average digitized Cobb T12-L5 angle produced for the 30 translated postures was 16 degrees. Angles ranged from 2.6 degrees to 27.0 degrees. Risser-Ferguson angles averaged 10 degrees between T12 and L5. Statistical correlations were found between Cobb L1-5 and translation to the left (P=.015), Cobb T12-L5 and translation to the right (P=.024), Risser-Ferguson angle and translation to the left (P=.021), and the lumbosacral angle to the right and trunk translation to the right (P=.027). CONCLUSIONS: During lateral translation of the thorax (trunk list), coupled lumbar lateral flexion resulted in the appearance of a pseudoscoliosis on AP radiographs. For this trunk list posture, Cobb angles are considerable (16 degrees ) and increase as the magnitude of trunk translation increases. Differentiating true structural scoliosis from this pseudoscoliosis would be clinically important. The small coupled axial rotation in trunk list is in contrast to the considerable degree of axial rotation observed in structural idiopathic scoliosis.

Concurrent validity of flexicurve instrument measurements: sagittal skin contour of the cervical spine compared with lateral cervical radiographic measurements.

OBJECTIVES: The aim of this study was to compare flexicurve surface contour measurements of the cervical spine with radiographic measurements of cervical lordosis. METHODS: One examiner evaluated 96 patients with chronic neck pain in neutral posture using a flexible ruler, flexicurve, to measure sagittal contour of the skin over the cervical spine from the external occipital protuberance to the vertebra prominens. The flexicurve skin contour and neutral lateral radiographs were digitized and compared. The flexicurve and radiographs were categorized into height-length ratio, curve angle, curve depth, sum of depths, modified Ishihara's index, and inverse of radius. Mean values, SDs, mean differences, and limits of agreement were calculated. The differences between flexicurve measurement mean values and x-ray mean values were deemed significant if the lower limit of agreement exceeded 15% of the mean values for the x-ray measurements. RESULTS: For all variables, except the height-length ratio, the mean values of the flexicurve variables differed significantly from the corresponding mean values of the radiographic measurements. All Pearson correlation coefficients were in the very poor range (r < 0.15). CONCLUSION: The flexicurve sagittal skin contour measurement has poor concurrent validity compared with established radiographic measurements of the cervical lordosis. The flexicurve tracings always predicted lordosis, overestimated the lordosis compared with x-ray values, and cannot discriminate between radiographic lordosis, straightened, S curves, and kyphotic alignments of the cervical curve.

A non-randomized clinical control trial of Harrison mirror image methods for correcting trunk list (lateral translations of the thoracic cage) in patients with chronic low back pain.

Spinal trunk list is a common occurrence in clinical practice, but few conservative methods of spinal rehabilitation have been reported. This study is a non-randomized clinical control trial of 63 consecutive retrospective subjects undergoing spinal rehabilitation and 23 prospective volunteer controls. All subjects presented with lateral thoracic-cage-translation posture (trunk list) and chronic low back pain. Initial and follow-up numerical pain rating scales (NRS) and AP lumbar radiographs were obtained after a mean of 11.5 weeks of care (average of 36 visits) for the treatment group and after a mean of 37.5 weeks for the control group. The radiographs were digitized and analyzed for a horizontal displacement of T12 from the second sacral tubercle, verticality of the lumbar spine at the sacral base, and any dextro/levo angle at mid-lumbar spine. Treatment subjects received the Harrison mirror image postural correction methods, which included an opposite trunk-list exercise and a new method of opposite trunk-list traction. Control subjects did not receive spinal rehabilitation therapy, but rather self-managed their back pain. For the treatment group, there were statistically significant improvements (approximately 50%) in all radiographic measurements and a decrease in pain intensity (NRS: 3.0 to 0.8). For the control group, no significant radiographic and NRS differences were found, except in trunk-list displacement of T12 to S1, worsened by 2.4 mm. Mirror image (opposite posture) postural corrective exercises and a new method of trunk-list traction resulted in 50% reduction in trunk list and were associated with nearly resolved pain intensity in this patient population. The findings warrant further study in the conservative treatment of chronic low back pain and spinal disorders.

Modeling of the sagittal cervical spine as a method to discriminate hypolordosis: results of elliptical and circular modeling in 72 asymptomatic subjects, 52 acute neck pain subjects, and 70 chronic neck pain subjects.

STUDY DESIGN: Computer analysis of digitized vertebral body corners on lateral cervical radiographs. OBJECTIVES: Using elliptical and circular modeling, the geometric shape of the path of the posterior bodies of C2-C7 was sought in normal, acute pain, and chronic pain subjects. To determine the least squares error per point for paths of geometric shapes, minor axis to major axis elliptical ratios (b/a), Cobb angles, sagittal balance of C2 above C7, and posterior tangent segmental and global angles. SUMMARY OF BACKGROUND DATA: When restricted to cervical lordotic configurations, normal, acute pain, and chronic pain subjects have not been compared for similarities or differences of these parameters. Conventional Cobb angles provide only a comparison of the endplates of the distal vertebrae, while geometric modeling provides the shape of the entire sagittal curves, the orientation of the spine, and segmental angles. METHODS: Radiographs of 72 normal subjects, 52 acute neck pain subjects, and 70 chronic neck pain subjects were digitized. For normal subjects, the inclusion criteria were no kyphotic cervical segments, no cranial-cervical symptoms, and less than +/- 10 mm horizontal displacement of C2 above C7. In pain subjects, inclusion criteria were no kyphotic cervical segments and less than 25 mm of horizontal displacement of C2 above C7. Measurements included segmental angles, global angles of lordosis (C1-C7 and C2-C7), height-to-length ratios, anterior weight bearing, and from modeling, circular center, and radius of curvature. RESULTS: In the normal group, a family of ellipses was found to closely approximate the posterior body margins of C2-C7 with a least squares error of less than 1 mm per vertebral body point. The only ellipse/circle found to include T1, with a least squares error of less than 1 mm, was a circle. Compared with the normal group, the pain group's mean radiographic angles were reduced and the radius of curvature was larger. For normal, acute, and chronic pain groups, the mean angles between posterior tangents on C2-C7 were 34.5 degrees, 28.6 degrees, and 22.0 degrees, C2-C7 Cobb angles were 26.8 degrees, 16.5 degrees, and 12.7 degrees, and radius of curvature were r = 132.8 mm, r = 179 mm, and r = 245.4 mm, respectively. CONCLUSIONS: The mean cervical lordosis for all groups could be closely modeled with a circle. Pain groups had hypolordosis and larger radiuses of curvature compared with the normal group. Circular modeling may be a valuable tool in the discrimination between normal lordosis and hypolordosis in normal and pain subjects.

Conservative methods for reducing lateral translation postures of the head: a nonrandomized clinical control trial.

Fifty-one retrospective, consecutive patients were compared to twenty-six prospective volunteer controls in a nonrandomized clinical control trial. Both groups had chronic neck pain and lateral head translation posture. For treatment subjects, beginning and follow-up pain scales and anteroposterior (AP) cervical radiographs were obtained after 12.8 weeks of care (average of 37 visits), while the duration was a mean of 12 months for control subjects. Digitized radiographs were analyzed for Risser-Ferguson angles and a horizontal translation distance of C2 from a vertical line through T3. For treatment, patients received the Harrison mirror-image postural methods, which include mechanically assisted manipulation, opposite head posture exercise, and opposite head translation posture traction. While no significant differences were found in the control group subjects' pain scores and AP radiographic measurements, statistically significant improvements were observed in the treatment group subjects' pain scores and lateral translation displacements of C2 compared to T3 (pretrial score: 13.7 mm, posttrial score: 6.8 mm) and in angle measurements.

Do alterations in vertebral and disc dimensions affect an elliptical model of thoracic kyphosis?

STUDY DESIGN: Mathematical modeling, using least squares method, of thoracic kyphosis was constructed as digitized points from radiographs of 50 healthy patients. OBJECTIVE: To determine a simple geometric model of the thoracic kyphosis. SUMMARY OF BACKGROUND DATA: Thoracic kyphosis is an important parameter of health, but geometric models of kyphosis are rare. Few papers report vertebral body and disc height data. METHODS: Thoracic vertebral bodies were digitized on lateral radiographs of 50 healthy patients. The average path of the posterior vertebral body corners of T1 through T12 was modeled, in the least squares sense, with a portion of an ellipse. The best-fit ellipse was sectioned with different model partitions using four sets of vertebral body heights and disc heights. Segmental and global angles derived from these four models were compared with reported values in the literature. RESULTS: A 72 degrees portion of an ellipse, with a minor-to-major axis ratio of 0.69, can closely approximate the path of the posterior body corners from the inferior of T1 to the superior of T12. The posterior vertebral body heights and disc heights have an average ratio of approximately 5:1. Segmental angles from T3-T4 through T11-T12 for all four models are close to other reported values. The thoracic spine has a height-to-length ratio of approximately 0.96. CONCLUSIONS: Thoracic kyphosis from inferior-posterior T1 to superior-posterior T12 can be closely modeled (least squares error per point < 1 mm) with a 72 degrees piece of an ellipse with a minor-to-major axis ratio of 0.69. The major axis is parallel to the posterior body margin of T12, whereas the minor axis passes through the superior endplate of T12. Segmental angles derived from this elliptical modeling are in the range of values from healthy patients.

Changes in sagittal lumbar configuration with a new method of extension traction: nonrandomized clinical controlled trial.

OBJECTIVE: To determine if a new method of lumbar extension traction can increase lordosis in chronic low back pain (LBP) subjects with decreased lordosis. DESIGN: Nonrandomized controlled trial with follow-up at 3 months and 1(1/2) years. SETTING: Primary care spine clinic in Nevada. PATIENTS: Beginning in mid-1998, the first 48 consecutive patients, who met the inclusion criteria of chronic LBP with decreased lordosis and who completed the treatment program were matched for sex, age, height, weight, and pain scores to 30 control subjects with chronic LBP, who received no treatment. INTERVENTIONS: A new form of 3-point bending lumbar extension traction was provided in-office 3 to 4 times a week for 12+/-4 weeks. Per session, traction duration was started at 3 minutes and was increased to a maximum of 20 minutes. For short-term pain relief, torsion lumbar spinal manipulation was provided in the initial 3 weeks. MAIN OUTCOME MEASURES: Pain as measured on a visual analog scale (VAS) and standing lateral lumbar radiographic measurements. RESULTS: Pain scales and radiographic measurements did not change in the control subjects. In the traction group, VAS ratings decreased from mean +/- standard deviation of 4.4+/-1.9 pretreatment to 0.6+/-0.9 posttreatment (P<.001), and radiographic angles (except at T12-L1) showed statistically significant changes. Mean changes were 5.7 degrees at L4-5 (P<.001), 11.3 degrees between posterior tangents on L1 and L5 (P<.001), 9.1 degrees in Cobb angle at T12-S1 (P<.001), 4.6 degrees in pelvic tilt (P<.001), and 4.7 degrees in Ferguson's sacral base angle (P<.001). At long-term follow-up (17(1/2)mo), 34 of the 48 (71%) subjects returned. Improvements in lordosis were maintained in all 34. CONCLUSIONS: This new method of lumbar extension traction is the first nonsurgical rehabilitative procedure to show increases in lumbar lordosis in chronic LBP subjects with hypolordosis. The fact that there was no change in control subjects' lumbar lordosis indicates the stability of the lumbar lordosis and the repeatability of x-ray procedures. Because, on average, chronic LBP patients have hypolordosis, additional randomized trials should be performed to evaluate the clinical significance of restoration of the lumbar lordosis in chronic LBP subjects.

Can the thoracic kyphosis be modeled with a simple geometric shape? The results of circular and elliptical modeling in 80 asymptomatic patients.

Many Cobb measurements have been reported at various levels for the thoracic kyphosis, but geometric models of the shape of kyphosis are rare. Thoracic vertebral bodies were digitized on 80 normal lateral full-spine radiographs to obtain the mean thoracic kyphosis. Global and segmental angles were determined. Computer iteration processes passed geometric shapes through the posterior body coordinates of the mean thoracic kyphosis to determine the best fit model in the least squares sense. The kyphosis was closely modeled with ellipses. The T1 and T12 areas tended to be flatter in curvature when compared with T2-T11, indicating these are inflection points. Mean global angles were Cobb(T1-T12) = 44.2 degrees, Cobb(T2-T11) = 39.9 degrees, and Cobb(T3-T10) = 33.3 degrees. The T2-T11 kyphotic region was closely modeled with approximately a 70-degree portion of an ellipse, with minor axis to major axis ratios of 0.6 to 0.72, and with major axis parallel to the posterior body margin of T11.

How do anterior/posterior translations of the thoracic cage affect the sagittal lumbar spine, pelvic tilt, and thoracic kyphosis?

Anterior and posterior thoracic cage translations in the sagittal plane have not been reported for their range of motion and effects on the lumbar spine and pelvis. Twenty subjects volunteered for full-spine radiography in neutral, anterior, and posterior thoracic cage translation postures in a standing position. While grasping an anterior vertical pole, with hands at elbow level, subjects were instructed on how to translate their thoracic cage without any flexion/extension, utilizing a full-length mirror. On the radiographs, all four vertebral body corners of T1 through S1 and the superior margin of the acetabulum were digitized. Segmental and global angles of thoracic kyphosis, sagittal lumbar curvature, and pelvic flexion/extension in translation postures were compared to alignment in the neutral posture. Using the femur heads as an origin, the mean range of thoracic cage translation, measured as horizontal movement of T12 from neutral posture, was found to be 85.1 mm anterior and 73 mm posterior. In anterior translation, the thoracic kyphosis is hypokyphotic (Cobb T1-T12 reduced by 16 degrees). In posterior translation, the segmental angles at T12-L1 and L1-L2 flexed, creating an "S" shape in the sagittal lumbar spine, while the thoracic kyphosis increased by 10 degrees. Using posterior tangents from L1 to L5 and T12 to S1, and Cobb angles at T12-S1, the lumbar curve reduced slightly (by less than 3.3 degrees for all global angle measurements) in anterior translation and reduced by 7.4 degrees, 5.7 degrees, and 8.1 degrees respectively in posterior thoracic translation. The angle of pelvic tilt (measured as the angle of intersection of a line through posterior-inferior S1 to the superior acetabulum and the horizontal) reduced by a mean of 15.9 degrees, and Ferguson's sacral base angle to horizontal reduced by a mean of 13.1 degrees in posterior translation. In anterior translation, pelvic tilt and Ferguson's sacral base angle increased by 15.1 degrees and 12.8 degrees, respectively. The findings of this study show that thoracic cage anterior/posterior translations cause significant changes in thoracic kyphosis (26 degrees ), lumbar curve, and pelvic tilt. An understanding of this main motion and consequent coupled movements might aid the understanding of spinal injury kinematics and spinal displacement analysis on full spine lateral radiographs of low back pain and spinal disorder populations.

Reliability and measurement error of the BioTonix video posture evaluation system--Part I: Inanimate objects.

OBJECTIVE: To investigate the reliability, concurrent validity, and error of a new video digitizing system for evaluating posture when applied to inanimate objects. DESIGN: Delayed repeated measures of digital images of inanimate objects. SETTING: University laboratory. METHODS: Digital video images of inanimate objects (5 parallelograms) of different sizes and shapes were obtained with the BioTonix postural evaluation system. Three examiners digitized video images of inanimate objects twice; the second data collection was 1 week after the first set. The objects were digitized with both high- and low-resolution settings of the video screen. The Tonix's measurements were statistically compared with the actual object dimensions. Statistical evaluations of reliability and validity were conducted. RESULTS: For distances, both intraclass and interclass correlation coefficients were very high, 0.99 for the estimate. The low- versus high-resolution settings were comparable for distances. For angles, on the low-resolution setting, both intraclass and interclass correlation coefficients were very high: 0.969 and 0.953. On the high-resolution setting, for angles, both intraclass and interclass coefficients were well above 0.99. The difference of the actual size and the means of the digitized measurements of the means were small: at most 1.5 degrees for angles and 3.3 mm for distances. The standard deviations were small, and the confidence intervals were narrow. CONCLUSIONS: Our results demonstrate that the BioTonix's video system has high degrees of reliability and validity. Thus this system would seem suitable for clinical use in the analysis of posture.

A new 3-point bending traction method for restoring cervical lordosis and cervical manipulation: a nonrandomized clinical controlled trial.

OBJECTIVE: To evaluate a new 3-point bending type of cervical traction. DESIGN: Nonrandomized controlled trial of prospective, consecutive patients compared with control subjects. Follow-up patient data were obtained at 3 and 15(1/2) months, and 8 1/10 months for controls. SETTING: Data were collected at a spine clinic in Nevada. PATIENTS: Volunteer subjects consisted of 30 patients and 24 controls. Subjects had cervicogenic pain (neck pain, headaches, arm pain, and/or numbness). Subjects were included if their Ruth Jackson radiographic stress lines measured less than 25 degrees but were excluded if they had suspected disk herniation or canal stenosis. All subjects completed the first follow-up examinations, and 25 of 30 patients completed the long-term follow-up examination. INTERVENTIONS: Spinal manipulation for pain and a new form of 3-point bending cervical traction to improve lordosis. Cervical manipulation was provided for the first 3 to 4 weeks of treatment. Traction treatment consisted of 3 to 5 sessions per week for 9 +/- 1 weeks. MAIN OUTCOMES MEASURES: Besides pain visual analog scale (VAS) ratings, pre- and posttreatment lateral cervical radiographs were analyzed. RESULTS: Control subjects reported no change in the pain VAS ratings and had no statistically significant change in segmental or global radiographic alignment. For the traction group, VAS ratings were 4.3 pretreatment and 1.6 posttreatment. Traction group radiographic measurements showed statistically significant improvements (P <.008 in all instances of statistical significance), including anterior head weight bearing (improved 6.2mm), Cobb angle at C2-7 (improved 12.1 degrees ), and angle between posterior tangents at C2-7 (improved 14.2 degrees ). For the treatment group, at 15(1/2)-month follow-up, only minimal loss of C2-7 lordosis (3.5 degrees ) was observed. CONCLUSIONS: Sagittal cervical traction with transverse load at midneck (2-way cervical traction) combined with cervical manipulation can improve cervical lordosis in 8 to 10 weeks as indicated by increases in segmental and global cervical alignment. Magnitude of lordosis at C2-7 remained stable at long-term follow-up.