Lumbar lordosis in spinal fusion. A comparison of intraoperative results of patient positioning on two different operative table frame types

STUDY DESIGN: One hundred one patients undergoing spine surgery for degenerative conditions were entered into a prospective radiographic evaluation of changes in lumbar lordosis as affected by positioning on two different operative tables. OBJECTIVES: The hypothesis of the present study is twofold: 1) the positioning of patients on specific types of operative tables may affect significantly the overall degree of lumbar lordosis obtainable, and 2) certain operative positioning may more accurately reproduce physiologic standing lateral lumbar lordosis. SUMMARY OF BACKGROUND DATA: In the management of degenerative and post-traumatic spinal deformities, lumbar fusion using posterior instrumentation permits more accurate and physiologic lordotic positioning of the involved fusion segments of the lumbar spine. However, various types of operating frames are available for use in this type of surgery, and despite the overall importance of correct lordotic positioning, there is some question as to what effect on positioning, as measured in degrees of lumbar lordosis, a particular frame might have. METHODS: Total, multisegmental, and unisegmental Cobb angle measurements of preoperative standing lateral radiographs and intraoperative lateral radiographs after positioning on respective operative tables were determined. Fifty-one patients were positioned on an Andrews-type table, and 50 patients were positioned on the four-poster-type frame. Statistical comparison using analysis of variance testing of changes in lordosis before and after surgery between study groups was evaluated. RESULTS: Lumbar lordosis measured from L1 to S1 with standing lateral radiographs showed a combined mean preoperative measurement of 45.18 degrees, with no statistical significance between groups. In comparison, there was a statistically significant difference between intraoperative measurements from L1 to S1 on the Andrews table versus the four-poster frame, revealing an average of 32.81 degrees versus 47.71 degrees, respectively (P < 0.005). Multisegmental lordosis measurement from L2 to S1 displayed statistical significance between groups, with a combined preoperative standing lateral radiograph average of 43.32 degrees, and intraoperative values of 31.28 degrees on the Andrews table versus 45.34 degrees on the four-poster frame (P < 0.005). Multisegmental lordosis measurements from L4 to S1 displayed statistical significance between groups, with a combined preoperative standing lateral radiograph average of 31.40 degrees and intraoperative values of 23.14 degrees on the Andrews table versus 32.94 degrees on the four-poster frame (P < 0.005). Segmental lordosis at L5-S1 was less dependent on frame type, with a combined preoperative standing lateral radiograph average of 20.53 degrees and intraoperative measurements of 20.06 degrees on the Andrews table versus 21.02 degrees on the four-poster frame (P < 0.43). CONCLUSION: Results from the present study display a statistically significant difference between multisegmental and total lumbar lordosis, depending on the type of operative table used in patient positioning. Segmental lordosis at L5-S1 depended less on frame type. This table-dependent positional change in lumbar lordosis could be incorporated easily into a lumbar fusion procedure, especially when supplemented with instrumentation, affecting the permanent overall degree of lordosis. These results suggest that a more physiologic degree of lumbar lordosis is obtained accurately with use of an operative table similar to the four-poster frame.     

The lordotic effect of the OSI frame on operative adolescent idiopathic scoliosis patients

STUDY DESIGN: A prospective evaluation of adolescent idiopathic scoliosis patients undergoing operative treatment on the Orthopedic Systems Incorporated (OSI; Jackson) frame. OBJECTIVES: To investigate prospectively thoracic, thoracolumbar, and lumbar sagittal alignments in patients with adolescent idiopathic scoliosis who undergo an instrumented posterior spinal fusion on the OSI frame. SUMMARY OF BACKGROUND DATA: In several studies, it has been shown that patient positioning on various operative frames is an important component of ultimate lumbar sagittal alignment. However, these studies have all concentrated on the lumbar spine, and no sagittal plane alignment data in adolescent idiopathic scoliosis patients have been reported in the thoracic and thoracolumbar junction as it relates to intraoperative positioning, correction maneuvers and correlative postoperative results. METHODS: Thirty-nine patients with operative adolescent idiopathic scoliosis treated with an instrumented posterior spinal fusion on the OSI frame were prospectively evaluated. Standing preoperative, intraoperative, and postoperative long-cassette lateral radiographs were reviewed with regional and segmental Cobb measurements of the thoracic, thoracolumbar junction, and lumbar spine obtained. RESULTS: Thoracic kyphosis (T1-T12) measured +34 degrees before surgery, +28 degrees during surgery, and +30 degrees after surgery, Thus, a statistically significant decrease was noted in thoracic kyphosis secondary to prone positioning on the OSI frame ( P < 0.05). Thoracolumbar spine measurements from T10 to L2 also showed a lordotic trend from +2 degrees before surgery, to -4 degrees during surgery, to -8 degrees after surgery, which was also statistically significant (P < 0.05). Total lumbar lordosis from T12 to S1 remained relatively unchanged from -60 degrees before surgery, to -59 degrees during surgery, to -60 degrees after surgery. However, segmental lumbar lordosis measured from T12 to the lowest instrumented vertebra showed a statistically significant increase in lordosis from -17 degrees before surgery, to -19 degrees during surgery, to -23 degrees after surgery (P < 0.05). Those patients in whom lumbar pedicle screws were used (vs. hooks alone) had the greatest increase in lumbar instrumented lordosis. CONCLUSIONS: Performing adolescent idiopathic scoliosis correction on the OSI frame tends to decrease thoracic kyphosis, increase thoracolumbar lordosis, and increase segmental instrumented lumbar lordosis, while it maintains total lumbar lordosis.     

Measurements of vertebral shape by radiographic morphometry: sex differences and relationships with vertebral level and lumbar lordosis

OBJECTIVE: To examine sex-related and vertebral-level-specific differences in vertebral shape and to investigate the relationships between the lumbar lordosis angle and vertebral morphology. DESIGN AND PATIENTS: Lateral thoracic and lumbar spine radiographs were obtained with a standardized protocol in 142 healthy men and 198 healthy women over 50 years old. Anterior (Ha), central (Hc) and posterior (Hp) heights of each vertebra from T4 to L4 were measured using a digitizing technique, and the Ha/Hp and Hc/Hp ratios were calculated. The lumbar lordosis angle was measured on the lateral lumbar spine radiographs. RESULTS: Ha/Hp and Hc/Hp ratios were smaller in men than women by 1.8% and 0.7%, respectively, and these ratios varied with vertebral level. Significant correlations were found between vertebral shape and the lumbar lordosis angle. CONCLUSIONS: These results demonstrate that vertebral shape varies significantly with sex, vertebral level and lumbar lordosis angle. Awareness of these relationships may help prevent misdiagnosis in clinical vertebral morphometry.     

Compensatory spinopelvic balance over the hip axis and better reliability in measuring lordosis to the pelvic radius on standing lateral radiographs of adult volunteers and patients

STUDY DESIGN: Sagittal alignments, including lumbar lordosis and spinopelvic balance (measured from C7, S1, and hip axis reference points for the relative positions of the spine and sacropelvis over the hips), were studied on standing 36-in. lateral radiographs of adult volunteers (control subjects) and patients who had specific spinal disorders. OBJECTIVES: To determine the most reliable methods for measuring lumbopelvic lordosis and to define significant spinopelvic compensations for sagittal balance. SUMMARY OF BACKGROUND DATA: Measurements for standing sagittal balance, obtained using a C7 plumb line, and segmental angulations of the spinal vertebrae, including lordosis to the sacrum, have been reported. Absolute values, even for normative data, have had wide variation and limited clinical usefulness. Correlations of sagittal balance with the reported spinopelvic angulations (spinal vertebral and sacropelvic angulations) have not been well defined. In addition, determinates of balance (spinal and pelvic) have not been studied for reliability, and compensatory mechanisms for maintenance of balance have not been carefully evaluated. Better recognition of the correlations and more reliable methods to measure lordosis and balance and the spinopelvic compensations for its maintenance may be beneficial in treating patients who have spinal disorders. METHODS: Measurements on standing 36-in. lateral radiographs were made for sagittal alignments in adult volunteers (n = 50) and in adult patients who had symptomatic degenerative lumbar disc disease (n = 50), low grade L5-S1 isthmic (lytic) spondylolisthesis (n = 30), and idiopathic or degenerative scoliosis (n = 30). All participants exhibited clinical compensation for balance. Data were analyzed for significant correlations within each group to determine compensatory correlations of spinopelvic balance with the other sagittal alignments. Intraobserver and interobserver reliability for the parameters evaluated were calculated. This included two methods for determining lordosis (S1 end-plate and pelvic radius techniques). RESULTS: Plumb line measurements for balance from the S1 and hip axis reference points, as defined, were similar in all four groups. However, the groups appeared to adjust for balance by using common and distinctive spinopelvic compensations that resulted in significantly and characteristically different angular alignments among the four groups. Lordosis and balance measurements were closely correlated, and the correlation was characterized by pelvic rotation and translation around the hip axis. The subjects with less lordosis typically stood with the C7 plumb line anterior to and at a longer distance from the sacral reference point. This was primarily because of posterior sacropelvic translation around the hip axis and not because the sagittal plumb line initially moved anteriorly away from the sacrum. This was true in all four groups and gave the appearance that the sacropelvis was less well balanced over the hips in the subjects with less lordosis. Even small differences in lordosis appeared to be associated with considerable adjustments in the other spinopelvic alignments. Therefore, it was important to determine that lordosis was lumbopelvic more reliably measured by the pelvic radius technique. CONCLUSIONS: Lower lumbar lordosis, by the pelvic radius technique, and compensatory sacropelvic translation around a hip axis, in addition to measurements from this axis to the C7 plumb line, were the primary determinates and most reliable radiographic assessments for sagittal balance. Understanding the common and characteristically different compensations that occur with balance in these patients who had specific spinal disorders may help to improve their care.     

The spinal curve in standing and sitting postures in children with idiopathic scoliosis

STUDY DESIGN: A sample of convenience of children with moderate idiopathic scoliosis without bracing or surgery was studied. The sample consisted of 19 children, aged 9 to 16 years, with mean Cobb angle of 24 degrees. The spinal configurations and paraspinal muscle activity in several commonly assumed postures were examined. OBJECTIVES: To determine how the apex angles, verticality of spine, and muscle activity vary with the assumed posture and whether the location and the number of spinal curves affect these variables. SUMMARY OF BACKGROUND DATA: It has been suggested that the configuration of the spine in commonly assumed postures can affect the spinal curve in scoliosis because of gravitational bending moments. There is, however, a paucity of data obtained in subjects in sitting postures that school-age children assume daily for prolonged periods. Absence of bilateral symmetry in pressure during sitting has been described, but its effect on the spinal apex angle has not been investigated. METHODS: Infrared-emitting markers, whose three-dimensional positions could be tracked by a pair of cameras, were affixed to the spine. The natural postures studied were relaxed standing, relaxed sitting, erect sitting, and writing while seated. Electromyographic activity in muscles close to the spinal apexes was recorded bilaterally for each test posture. RESULTS: Subjects leaned laterally and, in general, anteriorly, in all test postures, rather than placing the C7 vertebra vertically above S1. The direction of lean and the change in the spinal apex angle from standing to sitting varied depending on whether the spinal curve was single or double, thoracic or lumbar. Subjects with single curves, whether thoracic or lumbar, tended to lean laterally toward the convexity of their curve apex--that is, the lean was in a direction that reduced the apex angle. Subjects with double curves (thoracic and lumbar), in all postures except relaxed sitting, tended to lean toward the convexity of the lumbar curve, thereby reducing the lumbar apex angle and exacerbating the thoracic angle. Most subjects' apex angles were smaller in relaxed or erect sitting than in relaxed standing. Electromyographic activity was in general greater on the convex side of the curve, with greatest activity in erect sitting. CONCLUSIONS: The findings indicate that in self-selected postures the gravitational effect of leaning and the muscle activity in paraspinal muscles may serve to reduce the apex angle. Thus, a fully upright, centered posture may not be best for correction of every patient's spinal curve.     

New anterior instrumentation for the management of thoracolumbar and lumbar scoliosis. Application of the Kaneda two-rod system

STUDY DESIGN: The Kaneda multisegmental instrumentation is a new anterior two-rod system for the correction of thoracolumbar and lumbar spine deformities. This system consists of a vertebral plate and two vertebral screws for individual vertebral bodies and two semirigid rods to interconnect the vertebral screws. Clinical results of 25 thoracolumbar and lumbar scoliosis patients treated with this new instrumentation were analyzed. OBJECTIVES: To evaluate the efficacy of the new anterior instrumentation in correction and stabilization of thoracolumbar and lumbar scoliosis. SUMMARY OF BACKGROUND DATA: Since Dwyer first introduced the concept of anterior spinal instrumentation and fusion for scoliosis, anterior surgery has gradually gained acceptance. In 1976, a useful modification for the anterior spinal instrumentation, which reportedly provided means of lordosation and vertebral body derotation, was described. However, some authors reported a high tendency of the implant breakage, loss of correction, progression of the kyphosis, and pseudoarthrosis as the major complications. To overcome the disadvantages of Zielke instrumentation, the authors have developed a new anterior spinal instrumentation (two-rod system) for the management of thoracolumbar and lumbar scoliosis. METHODS: Anterior correction and fusion using Kaneda multisegmental instrumentation was performed in 25 patients with thoracolumbar or lumbar scoliosis. The average follow-up period was 3 years, 1 month (range, 2 years to 4 years, 7 months). There were 20 patients with idiopathic scoliosis (13 adolescents and seven adults) and five patients with other types of scoliosis, including congenital and other etiologies. All patients had correction of scoliosis by fusion within the major curve, and for 16 of the 25 patients, the most distal end vertebra was not included in the fusion (short fusion). Radiographic evaluations were performed to analyze frontal and sagittal alignments of the spine. RESULTS: The average correction rate of scoliosis was 83%. Over the instrumented levels, the correction rate was 90%. Preoperative kyphosis of the instrumented levels of 7 degrees was corrected to 9 degrees of lordosis. Sagittal lordosis of the lumbosacral area beneath the fused segments averaged 51 degrees before surgery and was reduced to 34 degrees after surgery. The trunk shift was improved from 25 mm before surgery to 4 mm at final follow-up evaluation. The average improvement in the lower end vertebra tilt-angle was 97% in those patients whose lower end vertebra was included in the fusion and 83% in patients whose lower end vertebra was not included in the fusion. Apical vertebral rotation showed an average correction rate of 86%. At final follow-up evaluation, all patients demonstrated solid fusion without implant-related complications. There was 1.5 degrees of frontal plane and 1.5 degrees of sagittal plane correction loss within the instrumented area at final follow-up evaluation. CONCLUSIONS: New anterior two-rod system showed excellent correction of the frontal curvature and sagittal alignment with extremely high correction capability of rotational deformities. Furthermore, correction of thoracolumbar kyphosis to physiologic lordosis was achieved. This system provides flexibility of the implant for smooth application to the deformed spine and overall rigidity to correct the deformity and maintain the fixation without a significant loss of correction or implant failure compared with conventional one-rod instrumentation systems in anterior scoliosis correction.     

Spinal deformity in myelodysplasia. Correction with posterior pedicle screw instrumentation

STUDY DESIGN: A retrospective review of transpedicular instrumentation used in a series of 24 patients with myelodysplastic spinal deformities and deficient posterior elements. OBJECTIVE: To describe the usefulness and efficacy of these instruments in the treatment of complicated myelodysplastic spinal deformity. METHODS: The mean preoperative scoliosis was 75.7 degrees (range, 39-130 degrees) in the 22 patients with scoliotic deformities; 4 patients with thoracic hyperkyphoses averaged 70.5 degrees (range, 46-90 degrees) and 10 patients with lumbar kyphoses averaged 80.5 degrees (range, 42-120 degrees). The instrumentation extended to the sacrum in 4 patients and the pelvis in 9; 10 patients also underwent anterior release and fusion and 7 underwent concomitant spinal cord detethering. At an average follow-up of 4.0 years (2.0-7.7 years; one patient died at 8 months), all patients have fused (with the exception of two lumbosacral pseudarthroses). RESULTS: At last follow-up, deformity measured 32.1 degrees scoliosis (range, 6-85 degrees), 30.8 degrees thoracic kyphosis (range, 24-35 degrees), and 0.0 degree lumbar kyphosis (range, 35 degrees kyphosis to 29 degrees lordosis). Three patients lost some neurologic function after surgery; two recovered within 6 months and one has incomplete recovery. No ambulatory patient lost the ability to walk. Five patients required additional surgical procedures; in three cases, there was instrumentation breakage associated with pseudarthrosis or unfused spinal segments. CONCLUSIONS: Pedicle screw instrumentation is uniquely suited to the deficient myelodysplastic spine. Compared with historical control subjects, these devices have proven capable of significant correction of both scoliotic and kyphotic deformities. This instrumentation appears particularly useful in preserving lumbar lordosis in all patients and may preserve more lumbar motion in ambulatory myelodysplasia patients.     

Comparison of the use of supine bending and traction radiographs in the selection of the fusion area in adolescent idiopathic scoliosis

STUDY DESIGN: A study was done to evaluate the use of voluntary supine side bending radiographs and Risser table traction radiographs in adolescent patients undergoing posterior spinal fusion for idiopathic scoliosis. OBJECTIVES: To compare the usefulness of supine side bending and traction radiographs in assessing curve flexibility and determining fusion levels in patients undergoing posterior spinal fusion for adolescent idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Supine side bending radiographs have been used in the preoperative evaluation of idiopathic scoliosis to determine curve flexibility and fusion area. Traction films have been used to determine the flexibility of large curves and neuromuscular curves where active side bending is not possible. No study to date has compared the use of these films in patients with adolescent idiopathic scoliosis undergoing surgery. METHODS: Seventy-five patients with more than a 2-year follow-up period after surgery were included in this study. Preoperative radiographs included a standing posteroanterior and lateral film and both supine maximal voluntary side bending films and a traction film done on a Risser table. A preoperative review of these radiographs was done to determine curve flexibility and fusion levels. At follow-up evaluation, the patients were examined for any evidence of decompensation or "adding-on" of levels. RESULTS: For curves less than 60 degrees, side bending radiographs showed greater curve correction than traction radiographs, whereas the opposite was true for curves greater than 60 degrees. For King I and II curves, side bending radiographs were superior for determination of lumbar curve flexibility and for distinguishing these two types of curves. On traction radiographs, the stable vertebra was 1.4 vertebral levels higher than on the standing film. When the fusion level was moved proximally because of the traction radiograph, decompensation or "adding-on" commonly occurred. CONCLUSIONS: Supine bending radiographs are superior to traction radiographs for assessing curve flexibility except for curves more than 60 degrees. The selection of the distal extent of fusion based on the traction radiograph gave a large number of poor results. The selection of fusion levels in adolescent Idiopathic scoliosis is best determined by a combination of standing posteroanterior and lateral radiographs and the supine maximum voluntary bend films.     

Severe primary HIV-1 infection among black persons in Barbados

The purpose of this long-term follow-up was (1) to investigate disc changes in the olisthetic segment in patients treated conservatively, (2) to compare disc changes above the slipped vertebra in conservatively treated patients with those in operatively treated patients, and (3) to establish possible relations of disc changes to the degree of the slip and to subjective back pain symptoms of the patients. The subjects were 227 patients with isthmic L5 olisthesis diagnosed under 20 years of age (mean 13.8 years) with a mean follow-up of 15.4 (range 5-30) years. Of these, 145 patients had been treated with segmental fusion and 82 had been treated conservatively. At follow-up, standing anteroposterior and lateral radiographs as well as flexion/extension views of the lumbar spine were taken. Disc degeneration was graded semiquantitatively: 0 = normal disc height, 1 = decrease of disc height < 50%, 2 = decrease > or = 50%, and 3 = obliteration of the disc. In the conservatively treated patients degeneration of the olisthetic disc was distributed by grade as follows: O: n = 38, 1: n = 24, 2: n = 14, 3: n = 6. No motion at all was observed in the olisthetic segment in 40 patients (48%) with a mean slip of 30%, segmental motion of 4 degrees-18 degrees was found in 42 patients with a mean slip of 14%. There was a statistically significant association of the degree of slip to the severity of disc degeneration and non-mobility of the segment. Grade 1 degeneration of the L4/5 disc occurred in 25.6% of the conservatively treated patients and in 32% of 48 patients treated with L5-S1 fusion. This correlated with the severity of the slip, but not with pain symptoms or pathologic segmental mobility at the time of follow-up. Out of 84 patients with L4-S1 fusion, in 17% grade 1 degeneration of the L3/4 disc was observed, and 3 out of 13 patients (23%) with L3-S1 fusion had grade 1 degeneration of the disc above the fusion. The disc changes had no correlation with subjective pain symptoms. It is concluded that the natural course of isthmic spondylolisthesis is associated with disc degeneration and spontaneous stabilization of the olisthetic segment. Fusion operations do not significantly increase the rate of disc degeneration in the adjacent disc above the fusion after a mean postoperative follow-up of 13.8 years. No correlation between the number of degenerated discs or the degree of degeneration and subjective low back pain symptoms was found.     

The progression of untreated lumbar kyphosis and the compensatory thoracic lordosis in myelomeningocele

Radiographs of 37 patients with untreated lumbar kyphosis without congenital vertebral anomalies associated with myelomeningocele were analyzed. With an average interval between radiographs of 6.2 years, the kyphosis was noted to increase at a mean rate of 4.3 degrees per year without correlation to its initial magnitude. The compensatory lordosis was more variable and progressed at a mean of 2.5 degrees per year. Children under the age of 2 years were more likely to increase the Cobb angle and the height of their kyphosis. There was an inverse relationship between the height of the kyphus and the lumbar spine height and the resultant growth of each. A modified kyphotic index less than 4 correlated with an increase in the curve and height of the kyphosis and the subsequent desire for surgery. Wide variability in radiographic parameters make predictions for an individual patient difficult.     

A geometric model of the lumbar spine in the sagittal plane

This article describes a geometric model using the skin profile and five anthropometric measurements to estimate the position of S1, T12, and all lumbar vertebrae for all postures assumed in the sagittal plane. This method involves a normalization process by which different skin profiles can be compared between postures and individuals. The skin profile is transformed by taking the differences with the lumbar spine into consideration. The model was developed and validated with 20 and 7 subjects, respectively. An error analysis shows an adequate level of accuracy for the absolute (1.68-1.82 cm) and relative (0.32-0.54 cm) linear positions of vertebrae as well as their absolute (2.6-6.7 degrees) and relative (1.4-3.6 degrees) angular positions except for T12; however, the validity of the model was limited to specific angular motions in flexion for the pelvis (12 +/- 3%), the entire lumbar spine (14 +/- 13%) and the intervertebral motion of L4/L5 (13 +/- 10%). The data obtained are very useful, especially in models designed to evaluate loadings on the lumbar spine.     

Lumbar lordosis measurement. A new method versus Cobb technique

STUDY DESIGN: A historic cross-sectional study of lumbar lordosis in 199 healthy individuals aged 1-30 years. OBJECTIVE: To evaluate the magnitude and rate of the development of the normal lumbar lordotic curve with age using two methods of measurement. SUMMARY OF BACKGROUND DATA: There is no agreement among spine physicians on the range of the normal lumbar lordotic curve. In certain conditions, such as a tethered spinal cord, a change in lordotic curve may indicate or even precede the onset of neurologic symptoms. Reliable measurements of the lumbar lordotic curve may aid in the early diagnosis and management of these conditions, before irreversible neurologic change ensues. METHODS: The lumbar lordotic curve was measured by the traditional Cobb technique and by a newly designed method, tangential radiologic assessment of lumbar lordosis. The data were subjected to the Morgan-Pitman test for correlated variances to observe which of the two methods was more reliable in measuring the magnitude and rate of change in the lumbar lordotic curve. RESULTS AND CONCLUSIONS: The rate of development of the lumbar lordotic curve appears to be nonlinear, increases during first year of life and during puberty, and reaches a plateau of approximately 50 degrees at maturity. The tangential radiologic assessment of lumbar lordosis method is more reproducible and more reliable in the lumbar lordotic curve, providing a smaller range of normal values (8 degrees-16 degrees less) than the Cobb method.     

Measurement of lumbar spine flexion-extension using a low-field open-magnet magnetic resonance scanner

RATIONALE AND OBJECTIVES: The authors investigated the feasibility of using a low-field open-magnet magnetic resonance (MR) scanner to acquire functional flexion-extension images for range of motion (ROM) measurements on the lumbar spine. METHODS: Seventeen healthy subjects with no symptoms of back pain (age range, 22-59 years) were scanned in a low-field open-magnet MR scanner in the flexed, neutral, and extended positions. Each image was downloaded to a computer workstation for subsequent flexion-extension, lordosis, and ROM measurement. RESULTS: Data from two subjects were not analyzed because their images did not show all the lumbar vertebrae. For the remaining 15, there was a large variation in the magnitude of the ROM values (range, 9 degrees-70 degrees; mean 36.4 degrees, SD 16.5 degrees). However, there was a significant correlation between age and ROM (r = -0.63; P < 0.05). CONCLUSIONS: The low-field open-magnet MR scanner provides a method for noninvasive imaging of the lumbar spine, allowing the subject freedom of movement in the horizontal plane. This enables functional flexion-extension images of the lumbar spine to be acquired.     

Evaluation of the assumptions used to derive an ideal normal cervical spine model

OBJECTIVES: To evaluate the accuracy of anatomical assumptions made to derive a geometrical, ideal, normal model of the upright, static, sagittal cervical spine, to make comparisons with other spinal models and to discuss the implications of a normal cervical model. BACKGROUND: Anatomical assumptions were made based on observations to assist in the development of a computerized geometrical model of the ideal upright, static, sagittal cervical spine. These assumptions address the magnitudes of the contribution made by the vertebral bodies and intervertebral discs to the overall magnitude and geometric shape of the cervical lordosis. STUDY DESIGN: (a) Data were collected from 400 lordotic lateral cervical radiographs and compared with the predictions of a geometric normal cervical lordotic model. Angels of intersecting tangent lines, drawn at posterior vertebral body margins, were measured at each disc space and between C2 and C7. Height-to-length ratios and an anterior weight-bearing distance were measured. (b) Literature reviews were obtained through Medline and Chirolars. RESULTS: (a) Modeling: the 400 sample subjects varied from the geometric model by approximately 5%. Subgroup averages, from partitioning the C2-C7 angle into 5 degrees intervals, were less than 8% in error to model predictions. (b) Literature review: lordosis is the normal configuration for the cervical spine and many chiropractic empirical models are similar. CONCLUSIONS: The anatomical assumptions used to derive our normal geometric model of the cervical lordosis seem to be supported by the average values and literature reviewed. Two typical geometric configurations of the cervical spine were identified as a normal circular lordotic arc of 34 degrees and an ideal normal of 42 degrees. Literature reviewed establishes cervical lordosis as a desirable clinical outcome of care.     

Further analysis of the reliability of the posterior tangent lateral lumbar radiographic mensuration procedure: concurrent validity of computer-aided X-ray digitization

OBJECTIVE: To investigate the reliability of a specific method of radiographic analysis of the geometric configuration of the lumbopelvic spine in the sagittal plane, and to investigate the concurrent validity of a computer-aided digitization procedure designed to replace the more tedious and time-consuming manual measurement process. DESIGN: A blind, repeated-measures design was used. The results of radiographic measures derived through the traditional manual marking method were compared with measures derived by computer-aided digitization of lateral lumbopelvic radiographs. SETTING: Private chiropractic clinic. MAIN OUTCOME MEASURES: Pearson's product-moment correlation coefficients, paired sample t tests and intraclass correlation co-efficients (ICC) were used to examine intraexaminer reliability, and repeated measures of analysis of variance were used to examine interexaminer reliability for relative rotation angles for T12-L1, L1-L2, L2-L3, L3-L4, L4-L5, L5-S1, overall lordosis measurement [absolute rotation angle (ARA)] from L1-L5 and Cobb angle of overall lordosis measured from the inferior surface of T12 to the superior surface of S1, Ferguson's sacral base angle to horizontal, angle of pelvic tilt (arcuate angle) to horizontal and anteroposterior thoracic translation (Sz) in millimeters. RESULTS: ICC estimates for intraexaminer reliability were in the range of 0.96-0.98 for the L1-L5 ARA, a range of 0.87-0.99 for the arcuate angle measurement, 0.83-0.94 for the Ferguson's angle measurement, 0.88-0.95 for the Cobb angle measurement from the inferior surface of T12 compared with the superior surface of S1 and 0.98-1.00 for the translation measurement of the lower thoracic spine to S1 (Sz). The intersegmental measurement's (T12-L1, L1-L2, L2-L3, L3-L4, L4-L5, L5-S1) correlations ranged from a low of 0.55 to a high of 0.97. Examination of these findings suggests that the reliability for the three doctors is acceptable with only the T12-L1 intersegmental measure falling below 0.70 for the least experienced examiner. Average ICC of interexaminer reliability for manual and computer-aided digitizing examiners were the following: 0.96 for the L1-L5 ARA; 0.84 for the arcuate angle measurement; 0.82 for the Ferguson's angle measurement; 0.88 for the Cobb angle measurement; 1.00 for the Sz translation measurement; and values of 0.65, 0.73, 0.74, 0.75, 0.89 and 0.81 for relative rotation angle measurements T12-L1, L1-L2, L2-L3, L3-L4, L4-L5 and L5-S1, respectively. CONCLUSION: The data tend to support the reliability of this method of radiographic analysis of the geometric configuration of the lumbopelvic spine as viewed on lateral lumbopelvic radiographs. The additional data presented here tend to support the concurrent validity of the computer-aided digitization method of analysis inasmuch as the measures determined by the digitizing examiners are essentially identical to those determined by the manual method plus or minus the average standard error of measure of each value.     

Repositioning a slumped person in a wheelchair. A biomechanical analysis of three transfer techniques

The purpose of this study was to determine the effect of three lifting techniques (unassisted lift, vertically assisted lift, and horizontally assisted lift) and two patient masses (65 kg and 75 kg) on loads acting on the lifter's spine when repositioning a wheelchair bound patient to a more upright sitting position. A static biomechanical model was used in conjunction with ground reaction force and videographic data to estimate compression and shear forces at the lumbosacral (L5/S1) joint. Results indicated that: L5/S1 compression forces associated with both unassisted and assisted transfers were of sufficient magnitude to warrant mechanical assistance; the two person technique with the assistant pushing the legs toward the back of the chair was associated with the lowest spinal loads; and L5/S1 compression forces were significantly greater for the vertically assisted lift compared to the unassisted lift. If a manual transfer is to be performed, the horizontally assisted lift is recommended to minimize loads on the lumbar spine of the lifter.     

Optimized vertical stereo base radiographic setup for the clinical three-dimensional reconstruction of the human spine

This paper presents a method to determine the stereoradiographic planes and anatomical vertebral landmarks giving the most reliable three-dimensional reconstructions of the thoracic and lumbar spine for clinical studies. The present investigation was limited to stereoradiographic setups with a normal vertical stereo base. Possible X-ray tube positions are thus corresponding to angles ranging from 0 (conventional posteroanterior radiograph) up to 30 degrees (dimension of the X-ray room). An X-ray phantom was used as a specimen from which three-dimensional reconstructions with the direct linear transformation (DLT) algorithm were obtained. Visibility of landmarks located on pedicles, end-plates, transverse and spinous processes was evaluated for the whole thoracic and lumbar spine (T1 to L5). Process landmarks were discarded because their poor visibility on radiographs produced inaccurate three-dimensional reconstructions. Considering the size, shape and orientation of vertebrae, an angle of 20 degrees between the posteroanterior horizontal position and the angled position of the X-ray tube gave optimal results. Landmarks located on pedicles and end-plates produced the most reliable three-dimensional reconstructions of the spine. Pedicles were found to be more reliable landmarks than end-plates. Validation of the technique with reconstructed steel beads reveals three-dimensional errors under 1.0 mm. Since vertebral landmarks were more difficult to identify on radiographs than steel beads, reconstruction results were compared with those obtained with a biplanar orthogonal setup. This shows that three-dimensional errors of 8.0 mm may be expected on actual reconstructions of the spine and errors as large as 15.0 mm may be present on poorly visible landmarks.     

Objective measurement of the height of lumbar intervertebral disks from lateral roentgen views of the spine

OBJECTIVE: Published methods to quantify height of lumbar discs from lateral radiographic views of the lumbar spine yield inaccurate results due to distortion in central projection. Normal values of disc height have not been compiled. METHODS: Starting from an analysis of the imaging properties of vertebral bodies in a lateral view and following a logical evolution of Farfan's proposal, a new protocol for the measurement of disc height is given which is independent of distortion. A database of normal values of the height of lumbar discs from T12/L1 to L5/S1 was compiled from 892 lateral views of healthy male and female subjects in the age range between 16 and 57 years. RESULTS: Employing the new protocol, height of all discs on a lateral view can be measured. Variations in position (standing, side-lying) do not influence the result. Retrospective investigations are feasible. The precision of the disc height measurement amounts to 4.15%. Normal, age-appropriate values for the height of lumbar discs are given for the first time. In the individual case, disc height can be quantitatively evaluated by comparison with the normative database. CLINICAL RELEVANCE: The new protocol can be employed to quantitatively identify processes which effect a decrease of disc height. In the individual case, the new protocol and the comparison with the normal database can be employed to quantitatively assess overload injury to lumbar discs in compensation cases.     

Surgical treatment of idiopathic thoracolumbar and lumbar scoliosis in adolescent patients

The surgical management of idiopathic thoracolumbar and lumbar scoliosis is complex because of the surgeon's desire to achieve curve correction while maintaining normal lumbar lordosis with as many distal mobile lumbar segments as possible. By doing so, the surgeon is able to maintain normal sagittal alignment and decrease the chance of degenerative lumbar spine disease below the scoliosis fusion. This article discusses the surgical treatment of the thoracolumbar and lumbar curve, and, it is hoped, provides a better understanding of this complex problem.     

Expression of human brain myelin basic protein gene cDNA in Escherichia coli]

OBJECTIVE: The objective of this study was to investigate the in vitro radiological prevalence of lumbar intervertebral disc calcification (IDC) in the elderly and its relation to osteoarthritis (OA). MATERIALS AND METHODS: Lumbar spine segments comprising L2-4 were resected from 60 cadavers (30 males, 30 females; average age 67 years) and investigated with high-contrast radiography and computed tomography (CT). RESULTS AND CONCLUSIONS: IDC was found in 58.3% of the patients using high-contrast radiography and in 46.7% of the patients using CT. IDC prevalence and OA grades in the lumbar spine and right hand were found to increase with age. IDC prevalence and OA grades for L2-3 were not significantly different from those for L3-4. No significant sex difference was found for IDC prevalence and OA grades. The results indicate that IDC is significantly underestimated in vivo by conventional radiography and the intervertebral disc calcification may be a common phenomenon in aging. The exact relation IDC to OA remains undetermined.