Weight change and adverse event incidence with a low-dose oral contraceptive: two randomized, placebo-controlled trials.

Changes in body weight and the incidence of estrogen-related side effects with low-dose oral contraceptives (OCs) containing 20 microg ethinyl estradiol (EE) have not been demonstrated in placebo-controlled trials. Two placebo-controlled, randomized trials demonstrated the efficacy of a low-dose OC for the treatment of acne in healthy females (n = 704; >or=14 years old) with regular menstrual cycles and moderate facial acne. Patients were randomized to receive 20 microg EE/100 microg levonorgestrel (LNG) or placebo for six cycles. Body weight was measured at baseline and during Cycles 1, 3, and 6. The occurrence of adverse events was recorded at each visit. Mean changes in weight from baseline were similar with 20 microg EE/100 microg LNG [0.72 kg +/- 2.64 (SD; n = 349)] and placebo [0.56 kg +/- 2.64 (SD; n = 355; p > 0.05)] for the last measured weight of each patient. Rates of headache, nausea, weight gain, and breast pain, side effects commonly attributed to OCs, were also similar between groups (p > 0.05). No serious, unexpected, drug-related adverse events occurred during the study. The low-dose OC containing 20 microg EE/100 microg LNG is safe, well tolerated, and does not cause weight gain.

Reliability of lateral bending and axial rotation with validity of a new method to determine axial rotation on anteroposterior cervical radiographs.

OBJECTIVE: To investigate the reliability of a new radiographic measurement of axial rotation and lateral bending on anterior-posterior cervical views by using a computer and sonic digitizer. DESIGN: A blind, repeated-measure design was used. Anteroposterior cervicothoracic radiographs were presented to each of 3 examiners in random order. Each film was digitized, and 1 week later the films were randomized for a second run. SETTING: Private, primary-care chiropractic clinic. MAIN OUTCOME MEASURES: The interclass and intraclass correlation coefficients (ICC) for intraexaminer and interexaminer reliability were calculated from measurements on radiographs for determining axial rotations (Ry) and lateral bending (Rz) of C3 to T3. RESULTS: When the new axial rotation method was applied to small rotations of a C3 plastic model, the average error was less than 1 degrees. For the calculations of axial rotation (Ry), the ICC values were in the good to excellent range. For axial rotation, the intraclass correlation coefficients were ICCs > or =0.78, and the interclass correlation coefficients were ICCs > or =0.67. For lateral flexions (Rz) of C3 to T3, all intraclass and interclass correlation coefficients were in the excellent range (ICCs > 0.87). CONCLUSIONS: Methods of calculating axial rotations in the spine have been reported for large angles (5 degrees to 30 degrees ) but not for smaller angles. A new method for determining axial rotations of the cervical segments on AP views, based on the chord across the arc displaced by the spinous-lamina junction, had reliability (ICC values) in the good to excellent range. Compared with measured rotations of a C3 model (-5 degrees to +5 degrees ), the new method had an average error of less than 1 degrees and approximately 11.5%. The reliability for the axial rotation measurements was in the good to excellent range, and the lateral bending measurements were all in the excellent range.

A randomized, controlled trial of a low-dose contraceptive containing 20 microg of ethinyl estradiol and 100 microg of levonorgestrel for acne treatment.

OBJECTIVE: To evaluate the efficacy of a low-dose oral contraceptive (OC) containing 100 microg of levonorgestrel (LNG) and 20 microg of ethinyl estradiol (EE) compared with placebo for the treatment of moderate acne. DESIGN: Multicenter, randomized, double-blind, placebo-controlled clinical trial. SETTING: Outpatient dermatology clinics. PATIENT(S): Women (> or =14 years old; n = 350) with normal menstrual cycles and moderate acne were randomized to receive LNG/EE or placebo for six cycles. INTERVENTION(S): Twenty microg of EE and 100 microg of LNG. MAIN OUTCOME MEASURE(S): Acne lesion counts and clinician global assessment were performed at baseline and at each cycle. Patient self-assessment was carried out at baseline and at cycles 4 and 6; blood pressure and weight were measured at baseline and at cycles 1, 3, and 6. RESULT(S): Inflammatory, noninflammatory, and total lesion counts at cycle 6 with LNG/EE were significantly lower compared to placebo. Patients in the LNG/EE group also had significantly better clinician global and patient self-assessment scores than those in the placebo group at cycle. Changes in weight from baseline were similar between patients in the LNG/EE and placebo groups at all measured time points. CONCLUSION(S): This double-blind, placebo-controlled study demonstrates that a low-dose OC containing 20 microg of EE and 100 microg of LNG is an effective and safe treatment for moderate acne.

Reliability of centroid, Cobb, and Harrison posterior tangent methods: which to choose for analysis of thoracic kyphosis.

STUDY DESIGN: Thirty lateral thoracic radiographs were digitized twice by each of the three examiners. OBJECTIVES: To determine the reliability of the centroid, Cobb, and Harrison posterior tangent methods when applied to analysis of thoracic kyphosis. BACKGROUND DATA: Reliability studies on measurements of thoracic kyphosis are rare. METHODS: Blind, repeated-measures design was used. Thirty lateral thoracic radiographs were digitized twice by each of three examiners. To evaluate reliability of determining global and segmental alignment, vertebral bodies of T1-T12 were digitized. Centroids at the intersection of vertebral body diagonals and tangents to posterior vertebral bodies were constructed by computer. Also the computer constructed global and segmental centroid angles, Cobb angles (two-line method), and posterior tangent intersection angles from T1 to T12. Interclass and Intraclass correlation coefficients for these data were calculated and interpreted. RESULTS: From the points selected by examiners, all three methods have similar high ICC values for the global angles (> 0.94). For the segmental angles, the interobserver and intraobserver reliability is also very similar for all three methods, with ICCs in the good and excellent ranges (0.59-0.75 and 0.75-1.0, respectively). The mean absolute differences of observers' measurements are low, similar, and in the range of 0.9 degrees to 2.5 degrees. CONCLUSIONS: The centroid, two-line Cobb, and Harrison posterior tangent methods, when applied to measurements of kyphosis, are all reliable and have similar small error ranges. The centroid method does not give an accurate segmental analysis, uses more points and more time in clinical applications, and results in smaller angles of total kyphosis than the Cobb or posterior tangent methods. The posterior tangents are the slopes along the curve.

Radiographic analysis of lumbar lordosis: centroid, Cobb, TRALL, and Harrison posterior tangent methods.

STUDY DESIGN: Delayed, repeated measures, with three examiners each twice digitizing thirty lateral lumbar radiographs. OBJECTIVES: To determine the reliability and clinical utility of the centroid, Cobb, tangential radiologic assessment of lumbar lordosis (TRALL), and Harrison posterior tangent line-drawing methods for analysis of lumbar lordosis. BACKGROUND DATA: Cobb's method is commonly used for curvature analysis on lateral lumbar radiographs, whereas the centroid, TRALL, and Harrison posterior tangent methods are not widely used. METHODS: Thirty lateral lumbar radiographs were digitized twice by each of three examiners. To evaluate reliability of determining global and segmental alignment, all four vertebral body corners of T12-S1 and the superior margin of the femur head were digitized. Angles created were segmental and global centroid, (two-line) Cobb angles, and intersections of posterior tangents. A global TRALL angle was determined. Means, standard deviations, mean absolute differences, interclass and intraclass correlation coefficients (ICC), and confidence intervals were calculated. RESULTS: The interobserver and intraobserver reliabilities of measuring all segmental and global angles were in the high range (ICCs > 0.83). The mean absolute differences of observers' measurements were small (0.6 degrees -2.0 degrees ). Distal segmental (L4-S1) and global angles of lumbar curvature were dependent on the method of measurement. CONCLUSIONS: All four radiographic methods had high reliability and low mean absolute differences of observers' measurements. Because it lacks a segmental analysis, the TRALL method is not recommended. The centroid, Cobb, and Harrison posterior tangent methods provide global and segmental angles. However, the centroid segmental method requires three segments and is less useful for a stability analysis.

Atypical expiratory flow volume curve in an asthmatic patient with vocal cord dysfunction.

BACKGROUND: Vocal cord dysfunction can coexist with or masquerade as asthma. Vocal cord dysfunction, when coexistent with asthma, contributes substantially to the refractory nature of the respiratory problem. OBJECTIVE: To report a case of an asthmatic patient with vocal cord dysfunction and a previously unreported unique expiratory flow volume curve. RESULTS: A 16-year-old female, known to have asthma, developed increased frequency of her asthma exacerbations. Spirometry, during symptoms, showed an extrathoracic airway obstruction with a reproducible unique abrupt drop and rise in the expiratory flow volume loop. Laryngoscopy showed adduction of the vocal cords during inspiration and expiration. CONCLUSIONS: We report a unique expiratory flow volume curve in an asthmatic with vocal cord dysfunction that resolved with panting maneuvers. Speech and psychological counseling helped prevent future attacks.

Slight head extension: does it change the sagittal cervical curve?

It is commonly believed that slight flexion/extension of the head will reverse the cervical lordosis. The goal of the present study was to determine whether slight head extension could result in a cervical kyphosis changing into a lordosis. Forty consecutive volunteer subjects with a cervical kyphosis and with flexion in their resting head position had a neutral lateral cervical radiograph followed immediately by a lateral cervical view taken in an extended head position to level the bite line. Subjects were patients at a spine clinic in Elko, Nevada. All radiographs were digitized. Global and segmental angles of the cervical curve were compared for any change in angle due to slight extension of the head. The average extension of the head required to level the bite line was 13.9 degrees. This head extension was not substantially correlated with any segmental or global angle of lordosis. Subjects were categorized into those requiring slight head extension (0 degree-13.9 degrees) and those requiring a significant head extension (> 13.9 degrees). In the slight head extension group, the average change in global angle between posterior tangents on C2 and C7 was 6.9 degrees, and 80% of this change occurred in C1-C4. In the significant head extension group, the average change in global angle between posterior tangents on C2 and C7 was 11.0 degrees, and the major portion of this change occurred in C1-C4. Out of 40 subjects, only one subject, who was in the significant head extension group and had only a minor segmental kyphosis, changed from kyphosis to lordosis. The results show that slight extension of the head does not change a reversed cervical curve into a cervical lordosis as measured on lateral cervical radiographs. Only small extension angle changes (mean sum = 4.8 degrees) in the upper cervical segments (C2-C4) occur in head extension of 14 degrees or less.

Comparison of axial and flexural stresses in lordosis and three buckled configurations of the cervical spine.

OBJECTIVE: To calculate and compare combined axial and flexural stresses in lordosis versus buckled configurations of the sagittal cervical curve. DESIGN: Digitized measurements from lateral cervical radiographs of four different shapes were used to calculate axial loads and bending moments on the vertebral bodies of C2-C7.Background. Osteoarthritis and spinal degeneration are factors in neck and back pain. Calculations of stress in clinically occurring configurations of the sagittal cervical spine are rare. METHODS: Center of gravity of the head (inferior-posterior sella turcica) and vertebral body margins were digitized on four different lateral cervical radiographs: lordosis, kyphosis, and two "S"-shapes. Polynomials (seventh degree) and stress concentrations on the concave and convex margins were derived for the shape of the sagittal cervical curvatures from C1 to T1. Moments of inertia were determined from digitizing and the use of an elliptical shell model of cross-section. Moment arms from a vertical line through the center of gravity of the head to the atlas and scaled neck extensor moment arms from the literature were used to compute the vertical component of extensor muscle effort. Segmental lever arms were calculated from a vertical line through C1 to each vertebra. RESULTS: In lordosis, anterior and posterior stresses in the vertebral body are nearly uniform and minimal. In kyphotic areas, combined stresses changed from tension to compression at the anterior vertebral margins and were very large (6-10 times as large in magnitude) compared to lordosis. In kyphotic areas at the posterior vertebral body, the combined stresses changed from compression (in lordosis) to tension. CONCLUSIONS: The stresses in kyphotic areas are very large and opposite in direction compared to a normal lordosis. This analysis provides the basis for the formation of osteophytes (Wolff's Law) on the anterior margins of vertebrae in kyphotic regions of the sagittal cervical curve. This indicates that any kyphosis is an undesirable configuration in the cervical spine. Relevance. Osteophytes and osteoarthritis are found at areas of altered stress and strain. Axial and flexural stresses at kyphotic areas in the sagittal cervical spine are abnormally high.

The role of human papillomavirus deoxyribonucleic acid assay and repeated cervical cytologic examination in the detection of cervical intraepithelial neoplasia among human immunodeficiency virus-infected women. Cervical Disease Study Group of the American Foundation for AIDS Research Community Based Clinical Trials Network.

OBJECTIVES: We sought to measure the characteristics of a quantitative human papillomavirus deoxyribonucleic acid assay and repeated cervical cytologic examination in screening for cervical intraepithelial neoplasia among human immunodeficiency virus-infected women. STUDY DESIGN: Human immunodeficiency virus-infected women with screening CD4+ lymphocyte counts of < or = 500 cells/mm3 (n = 103) were examined by quantitative human papillomavirus deoxyribonucleic acid assay and serial cervical cytologic examination and by colposcopy with biopsy and endocervical curettage during the course of 1 year. RESULTS: Quantitative measures of total human papillomavirus deoxyribonucleic acid and high-risk human papillomavirus deoxyribonucleic acid were strongly associated with any cervical intraepithelial neoplasia (P = .005) and high-grade cervical intraepithelial neoplasia (P = .0006), but they improved the sensitivity and negative predictive value of baseline screening only slightly when combined with cervical cytologic examination. Incident cervical intraepithelial neoplasia occurred frequently (20%) during 1 year of follow-up and was more common among human papillomavirus-infected women. Repeated cytologic examination identified 60% of women with new cervical intraepithelial neoplasia. CONCLUSION: Human immunodeficiency virus-infected women with at least mild immunosuppression have a high incidence of cervical intraepithelial neoplasia, which warrants close follow-up. Those with high baseline human papillomavirus deoxyribonucleic acid levels may be at the highest risk for incident cervical intraepithelial neoplasia.

Chiropractic biophysics digitized radiographic mensuration analysis of the anteroposterior cervicothoracic view: a reliability study.

OBJECTIVE: To investigate the reliability of a radiographic measurement procedure that uses a computer and sonic digitizer to determine projected spinal displacements from an ideal, normal position. DESIGN: A blind, repeated-measure design was used. Anteroposterior cervicothoracic spine radiographs were presented in random order to each of 3 examiners. Each film was digitized, and the films were randomized for a second examination. SETTING: Private, primary care chiropractic clinic. MAIN OUTCOME MEASURES: Intraclass correlation coefficients for intraexaminer and interexaminer reliability for measures on radiographs comparing the perpendicular distance (T(x)) from a vertical axis line drawn through the center of T4 and the center of C2, the linear distance (vertebra(apex)) from the center of the vertebra most displaced from a line connecting the centers of C2 and T4, the angle (Rz) formed by the intersection of the vertical axis line and the upper thoracic line, and the angle of intersection (CDA) between the upper thoracic line and the cervical line. RESULTS: Intraexaminer reliability for T(x) distance was 0.99 to 1.00, with confidence intervals from 0.98-1.00; for vertebra(apex) was 0.96 to 0.97, with confidence intervals from 0.92-0.98; for Rz was 0.94 to 0.98, with confidence intervals from 0. 89-0.99; and for CDA was 0.92 to 0.95, with confidence intervals from 0.84-0.97. Interexaminer reliabilities for the 3 examiners ranged from 0.97 to 0.99. CONCLUSIONS: Measures similar to those described in this study are commonly used to quantify and categorize spinal displacements from true vertical alignment (i.e., scoliosis measurements). Intraclass correlation coefficient values >0.70 are considered accurate enough for use in clinical and research applications. The measures tested here would fit within these guidelines of reliability. Establishing reliability is an important first step in evaluating these measures so that future studies of validity may be undertaken.

Cobb method or Harrison posterior tangent method: which to choose for lateral cervical radiographic analysis.

STUDY DESIGN: Thirty lateral cervical radiographs were digitized twice by three examiners to compare reliability of the Cobb and posterior tangent methods. OBJECTIVES: To determine the reliability of the Cobb and Harrison posterior tangent methods and to compare and contrast these two methods. SUMMARY OF BACKGROUND DATA: Cobb's method is commonly used on both anteroposterior and lateral radiographs, whereas the posterior tangent method is not widely used. METHODS: A blind, repeated-measures design was used. Thirty lateral cervical radiographs were digitized twice by each of three examiners. To evaluate reliability of determining global and segmental alignment, vertebral bodies of C1-T1 were digitized. Angles created were two global two-line Cobb angles (C1-C7 and C2-C7), segmental Cobb angles from C2 to C7, and posterior tangents drawn at each posterior vertebral body margin. Cobb's method and the posterior tangent method are compared and contrasted with these data. RESULTS: Of 34 intraclass and interclass correlation coefficients, 28 were in the high range (>0.7), and 6 were in the good range (0.6-0.7). The Cobb method at C1-C7 overestimated the cervical curvature (-54 degrees ) and, at C2-C7 it underestimated the cervical curve (-17 degrees ), whereas the posterior tangents were the slopes along the curve (-26 degrees from C2 to C7). The inferior vertebral endplates and posterior body margins did not meet at 90 degrees (C2: 105 degrees +/- 5.2 degrees, C3: 99.7 degrees +/- 5.2 degrees, C4: 99.9 degrees +/- 5.8 degrees, C5: 96.1 degrees +/- 4.5 degrees, C6: 97.0 degrees +/- 3.8 degrees, C7: 95.4 degrees +/- 4.1 degrees ), which caused the segmental Cobb angles to underestimate lordosis at C2-C3, C4-C5, and C6-C7. CONCLUSIONS: Although both methods are reliable with the majority of correlation coefficients in the high range (ICC > 0.7), from the literature, the posterior tangent method has a smaller standard error of measurement than four-line Cobb methods. Global Cobb angles compare only the ends of the cervical curve and cannot delineate what happens to the curve internally. Posterior tangents are the slopes along the curve and can provide an analysis of any buckled areas of the cervical curve. The posterior tangent method is part of an engineering analysis (first derivative) and more accurately depicts cervical curvature than the Cobb method.

Bioavailability of iron in two prenatal multivitamin/multimineral supplements.

OBJECTIVE: To determine the iron bioavailability in two popular prenatal multivitamin/multimineral supplement tablets containing 27 mg elemental iron. STUDY DESIGN: Iron absorption during an eight-hour period following ingestion of a multivitamin/multimineral formulation, both fasting and with a standardized meal, was measured in a group of 30 pregnant women (24-32 weeks of gestation) and statistically compared. The prenatal formulations were Stuartnatal Plus and Materna (Wyeth-Ayerst Pharmaceuticals, Philadelphia, Pennsylvania), and each contains 27 mg of elemental iron. A placebo was included in the study for the control group in this crossover, single-blind study. RESULTS: The net iron bioavailability (mean +/- SE) of Stuartnatal Plus and Materna, accounting for diurnal variation, and the iron ingested with the standardized meal was 5.4 +/- 0.4 and 4.6 +/- 0.2 mg, respectively, while fasting and 2.9 +/- 0.4 and 2.7 +/- 0.4 mg, respectively, postprandially. The total amount of iron absorption in the fasting states from both prenatal formulations exceeded the 3 mg of supplemental iron absorption per day recommended by the National Academy of Sciences. CONCLUSION: The results of this study indicate that these two prenatal multivitamin/multimineral formulations provide > 3.0 mg of supplemental iron absorption (fasting) as recommended by the National Academy of Sciences and 2.7 mg of iron absorption above the levels achieved following ingestion of a standard, low-iron test meal.

Cervical coupling during lateral head translations creates an S-configuration.

OBJECTIVE: To determine cervical coupling during the posture of lateral head translation relative to a fixed thoracic cage. DESIGN: Digitized measurements from anteroposterior cervical radiographs of 20 volunteers were obtained in neutral, left, and right lateral translation posture of the head compared to a fixed thorax. BACKGROUND DATA: Clinically, lateral translation of the head is a common posture. Ranges of motion and spinal coupling have not been reported for this movement. METHODS: Vertebral body corners, mid-lateral articular pillars and the superior spinous-lamina junction of C3-T4 were digitized on 60 radiographs. Using the orthogonal axis of positive x-direction to the left, vertical as positive y and anterior as positive z, digitized points were used to measure projected segmental z-axis rotation, y-axis rotation, and segmental lateral translations of each vertebra. RESULTS: Subjects translated their heads laterally a mean of 51 mm. The major coupled motion was lateral bending (z-axis rotation), which changed direction at the C4-C5 disc space creating an S-shape. Upper cervical (C3-C4) lateral bending was contralateral to the main motion of head translation direction. Lower cervical and upper thoracic lateral bending were ipsilateral. Other segmental motions averaged less than 1 mm and 1 degrees. CONCLUSIONS: Lateral head translations (x-axis) compared to a fixed thoracic cage can be large with a mean of 51 mm to one side. The major spinal coupling was lateral bending which changed direction at C4-C5 resulting in an S-configuration. This might have application in side impacts. All other segmental movements were small, less than 1 mm and 1 degrees. RELEVANCE: The clinically common posture of lateral head translation results in an S-shaped cervical spine and may occur in side impact trauma. This posture has not been studied for cervical coupling patterns or range of motion (ROM).

Sitting biomechanics, part II: optimal car driver's seat and optimal driver's spinal model.

BACKGROUND: Driving has been associated with signs and symptoms caused by vibrations. Sitting causes the pelvis to rotate backwards and the lumbar lordosis to reduce. Lumbar support and armrests reduce disc pressure and electromyographically recorded values. However, the ideal driver's seat and an optimal seated spinal model have not been described. OBJECTIVE: To determine an optimal automobile seat and an ideal spinal model of a driver. DATA SOURCES: Information was obtained from peer-reviewed scientific journals and texts, automotive engineering reports, and the National Library of Medicine. CONCLUSION: Driving predisposes vehicle operators to low-back pain and degeneration. The optimal seat would have an adjustable seat back incline of 100 degrees from horizontal, a changeable depth of seat back to front edge of seat bottom, adjustable height, an adjustable seat bottom incline, firm (dense) foam in the seat bottom cushion, horizontally and vertically adjustable lumbar support, adjustable bilateral arm rests, adjustable head restraint with lordosis pad, seat shock absorbers to dampen frequencies in the 1 to 20 Hz range, and linear front-back travel of the seat enabling drivers of all sizes to reach the pedals. The lumbar support should be pulsating in depth to reduce static load. The seat back should be damped to reduce rebounding of the torso in rear-end impacts. The optimal driver's spinal model would be the average Harrison model in a 10 degrees posterior inclining seat back angle.

Lumbar coupling during lateral translations of the thoracic cage relative to a fixed pelvis.

OBJECTIVE: To determine lumbar coupling during lateral postural translations (lumbosacral list) of the thoracic cage relative to a fixed pelvis. DESIGN: Digitized measurements from anteroposterior lumbar radiographs of 17 volunteers were obtained in neutral, maximal left lateral translation and maximal right lateral translation posture of the thoracic cage compared to a fixed pelvis. Subjects were constrained with two sets of clamps at the lateral borders of the pelvis and lower ribs. BACKGROUND: Data. Clinically, lumbosacral list is a common posture. Range of motion and spinal coupling results have not been reported for the lumbosacral list movement. METHODS: Four vertebral body corners, mid narrow-waisted body margins, superior and inferior pedicle margins, and spinous-lamina junction of T12-L5 were digitized on 51 anterior-posterior lumbar radiographs. Using the orthogonal axes of positive x-direction to the left, vertical as positive y, and anterior as positive z, digitized points were used to measure projected segmental z-axis rotation, y-axis rotation, and segmental lateral translations of each vertebra. RESULTS: Using the displacement of T12, subjects could translate 35-70 mm left or right along the x-axis with an average of 53.2 mm to the left and 52.1 mm to the right. Using superior endplates to superior sacral base, lateral flexion was largest at L1 and decreased from L1 to L5, but the segmental rotation angles for lateral flexion were largest at L2-L3 (3.9 degrees ), L3-L4 (6.2 degrees ) and L4-L5 (5.7 degrees ) and were in the same direction as the main motion translation. The relative z-axis rotation of T12 was opposite to the direction of L1-L5. The coupled y-axis rotations were less than 1 degrees and coupled segmental lateral translations were averaging less than 1 mm. CONCLUSIONS: Thoracic cage x-axis translations compared to a fixed pelvis are significant, between 35 and 70 mm. The z-axis lumbar coupled rotation was largest at L2-L3, L3-L4 and L4-L5 and to the same side of the main motion translation in L1-L5, but opposite the main motion direction for T12. All other movements were small, averaging less than 1 degrees or 1 mm. RELEVANCE: The clinically common posture of lateral translation of the thoracic cage (lumbosacral list) is often associated with disc herniation. Yet normal lumbar coupling patterns and total range of motion of this movement have not been established in the literature. Normal values for lumbar segmental coupling on anterior-posterior lumbo-pelvic radiographs during trunk list might be important for an analysis of segmental instability since segmental translations were determined to be 1 mm or less.

A review of biomechanics of the central nervous system--Part III: spinal cord stresses from postural loads and their neurologic effects.

OBJECTIVE: To review literature pertaining to neurologic disorders stemming from abnormal postures of the spine. DATA COLLECTION: A hand search of available reference texts and a computer search of literature from Index Medicus sources was performed, with special emphasis placed on spinal cord stresses and strains caused by various postural rotations and translations of the skull, thorax, and pelvis. RESULTS: Spinal postures will often deform the neural elements within the spinal canal. Spinal postures can be broken down into four types of loading: axial, pure bending, torsion, and transverse, which cause normal and shear stresses and strains in the neural tissues and blood vessels. Prolonged stresses and strains in the neural elements cause a multitude of disease processes. CONCLUSION: Four types of postural loads create a variety of stresses and strains in the neural tissue, depending on the exact magnitude and direction of the forces. Transverse loading is the most complex load. The stresses and strains in the neural elements and vascular supply are directly related to the function of the sensory, motor, and autonomic nervous systems. The literature indicates that prolonged loading of the neural tissue may lead to a wide variety of degenerative disorders or symptoms. The most offensive postural loading of the central nervous system and related structures occurs in any procedure or position requiring spinal flexion. Thus flexion traction, rehabilitation positions, exercises, spinal manipulation, and surgical fusions in any position other than lordosis for the cervical and lumbar spines should be questioned.

A review of biomechanics of the central nervous system--part II: spinal cord strains from postural loads.

OBJECTIVE: To review spinal cord strains arising from postural loads. DATA COLLECTION: A hand search of available reference texts and a computer search of literature from the Indexed Medicus sources were collected, with special emphasis placed on spinal cord strains caused by various postural rotations and translations of the skull, thorax, and pelvis RESULTS: All spinal postures will deform the neural elements within the spinal canal. Flexion causes the largest canal length changes and, hence, the largest nervous system deformations. Neural tissue strains depend on the spinal level, the spinal movement generated, and the sequence of movements when more than one spinal area is moved. CONCLUSIONS: Rotations of the global postural components (head, thoracic cage, pelvis, and legs) cause stresses and strains in the central nervous system and peripheral nervous system. Translations of the skull, thorax, and pelvis, as well as combined postural loads, need to be studied for their effects on the spinal canal and neural tissue deformations. Flexion of any part of the spinal column may generate axial tension in the entire cord and nerve roots. Slight extension is the preferred position of the spine as far as reducing the magnitude of mechanical stresses and strains in the central nervous system is concerned.

Chiropractic biophysics digitized radiographic mensuration analysis of the anteroposterior lumbopelvic view: a reliability study.

OBJECTIVE: To investigate the reliability of a radiographic measurement procedure that uses a computer and sonic digitizer to determine projected spinal displacements from an ideal normal position. DESIGN: A blind, repeated-measure design was used. Anteroposterior lumbopelvic radiographs were presented to each of 3 examiners in random order. Each film was digitized, and the films were randomized for a second run. SETTING: Private, primary-care chiropractic clinic. MAIN OUTCOME MEASURES: The angle of the sacral base in comparison to a true horizontal line (horizontal base angle), lumbodorsal angle, lumbosacral angle, and the thoracic translational displacement from true vertical determined as the perpendicular distance from the center of T12 to a vertical axis line drawn from the center of the S1 spinous process cephalad and parallel to the lateral edge of the x-ray film. RESULTS: Intraexaminer reliability for the (a) horizontal base angle was .72 to .94, with confidence intervals included in the range of .52 to .97; (b) lumbodorsal angle was .90 to .96, with confidence intervals in the range of .82 to .98; (c) lumbosacral angle was .84 to .96, with confidence intervals in the range of .72 to .98, and (d) thoracic translational displacement from vertical was .95 to.97, with confidence intervals included in the range of .91 to .99. Interexaminer reliability for the three examiners ranged from .71 to .97. CONCLUSIONS: Measures similar to those described in this study are commonly used to measure and categorize spinal displacements from true vertical alignment (ie, scoliosis measurements). Most patient assessment methods used in chiropractic have poor or unknown reliability. The one possible exception to this rule is spinal displacement analysis performed on radiographs. In chiropractic, intraclass correlation coefficients values greater than .70 are considered accurate enough for use in clinical and research applications. The measures tested here would fit within these guidelines of reliability. Establishing reliability is an important first step in evaluating these measures so that future studies of validity may be undertaken.