摘要:

Study Design.The authors performed a correlative macroscopic, histologic, and immunohistochemical investigation on human lumbar intervertebral discs using complete motion segment slices, including all age groups and stages of degeneration.Objectives.To identify markers for age-related changes of human lumbar intervertebral discs. In particular, to investigate changes in the distribution pattern of collagen Types I, II, III, IV, V, VI, IX, and X. In addition, to study posttranslational protein modification by the immunolocalization of N-(carboxylmethyl)lysine (CML), which is regarded as a biomarker for oxidative stress.Summary of Background Data.Data on a correlation of age-related changes in disc morphology and disc matrix composition is sparse. So far, no comprehensive analysis considered a correlation of macroscopic, histologic, and biochemical age-related alterations using complete sections of intervertebral discs (i.e.,including nucleus pulposus, anulus fibrosus, endplates, and vertebral bodies). In addition, there is need for specific markers for these disc changes to allow for a better correlation with disc function.Methods.After photodocumentation of the macroscopic appearance, 229 sagittal lumbar motion segments obtained from 47 individuals (fetal to 86 years) during routine autopsy were processed for histologic and immunohistochemical analysis. All slices were investigated for histologic alterations of disc degeneration. A randomly selected subset of these specimens (n = 45) was used for a correlative analysis of interstitial collagens and molecular modifications of matrix proteins.Results.The presence of CML-modification of extracellular matrix proteins, mainly collagen, was observed first in the nucleus pulposus of a 13-year-old individual and increased significantly with age. In elderly people, both the nucleus pulposus and the anulus fibrosus showed extensive CML deposition. This CML deposition was accentuated in areas of macroscopic and histologic disc degeneration. After the occurrence of CML in the nucleus pulposus, we found a change in the collagen type pattern. An initial increase in nuclear collagen Types II, III, and VI staining was followed by a loss of collagen Type II, the occurrence of collagen Type I, and the persistence of high collagen Type III and VI levels, which were finally decreased again. The nuclear chondrocytes revealed significant changes in their immediate pericellular matrix, indicating phenotypic changes. Thus, exclusively in the nucleus pulposus of adolescents and young adults a significant proportion of cells positively stained for the basement membrane collagen Type IV. Collagen Type X was expressed by nuclear chondrocytes at a higher age and was associated with advanced degenerative disc alterations.Conclusions.The authors present the first study in which age-related changes are correlated on a macroscopic, histologic, and molecular level using complete sections of lumbar motion segments. They reconfirm the notion that disc degeneration starts as early as in the second decade of life. Therefore, only early prevention of disc damage may inhibit disc degeneration and its sequelae. Phenotypic alterations of nuclear chondrocytes as monitored by collagen Type IV in young adults with minor lesions and collagen Type X in advanced lesions indicate distinct cellular reactions, possibly as a reaction to enhanced oxidative stress. The degree of this oxidative stress is reflected by the CML-staining pattern which, in turn, indicates that the disc undergoes an accumulative stress, possibly leading to altered properties of the collagen fibrils and, thereby, tissue destruction. The deposition of CML proved to be the best marker for ongoing age-related changes in the intervertebral disc.

ISSN:0362-2436    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Study Design.Experimental models of intervertebral disc and facet joint degeneration were createdin vivoin the porcine lumbar spine for studying spinal kinematics, using a dynamic technique.Objectives.To quantify the changes in spinal kinematics and the stabilizing capacity of the lumbar musculature caused by chronic lesions in the intervertebral disc and facet joints.Summary of Background Data.Segmental kinematics are detrimentally altered by acute injury to passive structures of the motion segment. However, stimulation of the surrounding musculature adds stability to the motion segment. Thein vivokinematics of a degenerated lumbar motion segment and the stabilizing function of the surrounding musculature have not been quantified dynamically.Methods.Forty-four pigs were used in six chronic lesion models: sham, disc anulus, disc nucleus, facet capsule, facet joint slit, and facet joint wedge. Three months after injury, an instrumented linkage was used to measure continuously the sagittal kinematics of the L3-L4 motion segment during flexion-extension, with and without stimulation of the lumbar paraspinal musculature. Flexion-extension end point and maximum ranges of motion, and hysteresis were analyzed.Results.Significant alterations in the kinematics caused by chronic lesions were observed, particularly when using the maximum range of motion and when comparing changes in axial translation. Muscular stimulation reduced the hysteresis in the sham, facet capsule, and disc nucleus groups; however, increased hysteresis was observed in the remaining lesion groups.Conclusions.The kinematic behavior of motion segments with chronic lesions was established. The maximum range of motion, which must be measured using a dynamic technique, was a more sensitive parameter for identifying changes in segmental kinematics caused by chronic lesions than was the end range of motion. The lumbar musculature was less efficient overall in stabilizing the motion segment, possibly because of altered mechanisms in the neuromuscular feedback system.

ISSN:0362-2436    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Study Design.This prospective study analyzed the influence of transpedicular instrumented on the operative treatment of patients with degenerative spondylolisthesis and spinal stenosis.Objectives.To determine whether the addition of transpedicular instrumented improves the clinical outcome and fusion rate of patients undergoing posterolateral fusion after decompression for spinal stenosis with concomitant degenerative spondylolisthesis.Summary of Background Data.Decompression is often necessary in the treatment of symptomatic patients who have degenerative spondylolisthesis and spinal stenosis. Results of recent studies demonstrated that outcomes are significantly improved if posterolateral arthrodesis is performed at the listhesed level. A meta-analysis of the literature concluded that adjunctive spinal instrumentation for this procedure can enhance the fusion rate, although the effect on clinical outcome remains uncertain.Methods.Seventy-six patients who had symptomatic spinal stenosis associated with degenerative lumbar spondylolisthesis were prospectively studied. All patients underwent posterior decompression with concomitant posterolateral intertransverse process arthrodesis. The patients were randomized to a segmental transpedicular instrumented or noninstrumented group.Results.Sixty-seven patients were available for a 2-year follow-up. Clinical outcome was excellent or good in 76% of the patients in whom instrumentation was placed and in 85% of those in whom no instrumentation was placed (P= 0.45). Successful arthrodesis occurred in 82% of the instrumented casesversus45% of the noninstrumented cases (P= 0.0015). Overall, successful fusion did not influence patient outcome (P= 0.435).Conclusions.In patients undergoing single-level posterolateral fusion for degenerative spondylolisthesis with spinal stenosis, the use of pedicle screws may lead to a higher fusion rate, but clinical outcome shows no improvement in pain in the back and lower limbs

ISSN:0362-2436    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Study Design.A prospective randomized clinical study.Objectives.To evaluate supplementary pedicle screw fixation (Cotrel-Dubousset) in posterolateral lumbar spinal fusion.Summary of Background Data.The rationale behind lumbar fusion is to eliminate pathologic motion to relieve pain. To improve fusion rates and to allow reduction, a rigid transpedicular screw fixation may be beneficial, but the positive effect of this may be counter-balanced by an increase in complications.Methods.The inclusion criteria were severe, chronic low back pain from spondylolisthesis Grades 1 and 2 or from primary or secondary degenerative segmental instability. One hundred thirty patients were randomly allocated to receive no instrumentation (n = 66) or Cotrel-Dubousset instrumentation (n = 64) in posterolateral lumbar fusion. Variables were registered at the time of surgery and at 1 and 2 years after surgery.Results.Follow-up was achieved in 97.7% of the patients. Fusion rates deduced from plain radiographs were not significantly different between instrumented and noninstrumented groups. The functional outcome assessed by the Dallas Pain Questionnaire improved significantly in both groups, and there were no significant differences in results between the two groups, except for significantly better (P< 0.05) functional outcome in relation to daily activities in the instrumented group when neural decompression had been performed. The global patients' satisfaction was 82% in the instrumented groupversus74% in the noninstrumented group (not significant). Fixation of instrumentation increased operation time, blood loss, and early reoperation rate significantly. Patients experienced only a few minor postoperative complications; none were major. Two infections appeared in the Cotrel-Dubousset group. Significant symptoms from misplacement of pedicle screws were seen in 4.8% of the instrumented patients.Conclusions.Lumbar posterolateral fusion with pedicle screw fixation increases the operation time, blood loss, and reoperation rate, and leads to a significant risk of nerve injury. The functional outcome improves significantly with high patient satisfaction, with or without instrumentation. No significant differences were observed between the two groups in functional outcome and fusion rate. The only gain in functional outcome from instrumentation was found in the daily activity category in patients with supplementary neural decompression. The results of this study do not justify the general use of pedicle screw fixation alone as an adjunct to posterolateral lumbar fusion.

ISSN:0362-2436    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Study Design.A combined morphologic and finite-element study on vertebral trabecular bone.Objective.To relate the form and function of vertebral trabecular bone, in an attempt to better understand the mechanical function of a lumbar vertebra.Summary of Background Data.The architecture of bone is closely related to its mechanical function (Wolff's Law). In the human spine, vertebrae are subjected to a large variety of loads. Yet, these bones show a typical architecture, which means that they carry typical loads.Methods.Five trabecular bone cubes from specific sites of a lumbar vertebra were 3D-reconstructed for computerized analysis. The architecture of the specimens was quantified by the bone volume fraction and a measure of anisotropy, the mean bone length. A finite element model was used to calculate internal stresses within a homogeneous vertebral body under basic loads. For each load case, bone volume fraction of the specimens was compared with the equivalent von Mises stress, and mean bone length was compared with the principal stress directions.Results.Bone volume fraction poorly related to the von Mises stress in the physiologic load case of axial compression. However, high bone volume fractions exist at locations wheremultipleload situations occur (e.g.,near the pedicles and endplates). Remarkably, these sites also show finer architectures. Comparison of mean bone length with principal stresses revealed that the vertebral trabecular bone architecture particularly, but not entirely, corresponds to the stress field under axial compression. The horizontal struts near the endplates were found to be due to the function of the healthy intervertebral disc, and facetal joint loads introduce stress components that relate well with the bone structures near the pedicle bases.Conclusions.The trabecular bone architecture and the vertical orientation of the facet joints suggest that walking may be the main activity that determines the lumbar vertebral bone architecture.

ISSN:0362-2436    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Study Design.A porcine model was used to study whether muscular activation in the paraspinal muscles caused by nerve stimulation in the anulus fibrosus of a lumbar intervertebral disc could be altered by saline injection into the zygapophysial (facet) joint.Objectives.To elucidate possible mechanisms regarding the nerve pathways and interactions between the intervertebral disc, zygapophysial joints, and the paraspinal musculature.Summary of Background Data.The physiologic basis for chronic low back pain, including muscular spasm, is uncertain. Although extensive research involving the lumbar motion segments and the surrounding tissues has been performed, the neuromuscular connection has not been sufficiently investigated.Materials and Methods.Twenty-three adolescent pigs were used to measure the electromyographic response in the paraspinal musculature to electrical stimulation of the posterolateral L3-L4 anulus fibrosus, before and after introduction of physiologic saline into the zygapophysial joint. Motor unit action potentials were recorded using three sets of needle electrodes placed into the deepest fascicles of the multifidus, bilateral to the L4 and L5 spinous processes, and into the central longissimus musculature, bilateral to the L4 spinous process.Results.Stimulation of the nerves within the posterolateral anulus of the disc elicited reactions in the paraspinal muscles, namely the lumbar multifidus and longissimus. Introduction of physiologic saline into the zygapophysial joint resulted in a reduction in the motor unit action potential amplitude. This reduction was manifested as an immediate and constant reduction, a graded reduction, or a delayed reaction, during which the reduction occurred an average of 5 minutes after the saline injection.Conclusions.Introduction of physiologic saline into the zygapophysial joint reduced the stimulation pathway from the intervertebral disc to the paraspinal musculature. The zygapophysial joints may therefore have a regulating function, controlling the intricate neuromuscular balance in the lumbar motion segment.

ISSN:0362-2436    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Study Design.Human lumbar functional spinal units (FSUs) were moved throughout their range of motion in sagittal and lateral bending while the dynamics of this movement were computedin vitro.Functional spinal units were tested intact and after subsequent discectomy and unilateral facetectomy.Objective.To establish "normal" velocity and acceleration curves during lumbar intersegmental bending in the intact FSU and then evaluate the changes of this dynamic behavior due to surgically induced component instability.Summary of Background Data.In preliminary clinical studies, researchers have provided evidence that dynamic motion measurements may be useful in the assessment of spinal impairment.Methods.Human lumbar FSUs moved from extension to flexion, flexion to extension, left to right, and right to left by a pure moment. Range of motion, as well as velocity and acceleration patterns of the main and coupled motions, were evaluated in six degrees of freedom by position changes of attached infrared light-emitting diodes recorded by cameras. Functional spinal units were tested in three surgical conditions (intact, discectomy, and unilateral facetectomy) under two preload conditions (no preload and 400 N preload).Results.Motion of intact FSUs progressed with velocity and acceleration patterns that were relatively independent from motion direction and preload condition. After surgery, however, the dynamic motion became unequal between opposite motion directions (even if range of motion was equal between directions) and more sensitive to preload condition.Conclusion.The results suggest that equilibrium of dynamic motion parameters within a range of motion is an element of segmental stability. From this approach, segmental instability appears to change intersegmental acceleration and velocity patterns as a function of motion direction and load conditions. Whereas dynamic motion patterns in an intact FSU are relatively invariable between reversed motion directions, instability is characterized by a considerable diversity of dynamic motion parameters between reversed motion directions.

ISSN:0362-2436    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Study Design.Human lumbar functional spinal units (FSUs) were moved throughout their range of motion in sagittal and lateral bending, while the dynamics of this movement were computedin vitro.Functional spinal units were tested intact and after subsequent discectomy and unilateral facetectomy.Objective.To determine whether the patterns of small jerks observed during intersegmental motion are sensitive to spinal instability.Summary of Background Data.Small jerks have been observed as hesitation during increasing velocity and as giving way during decreasing velocity in the experiments described in Part I of this study.Methods.Human lumbar functional spinal units were moved from extension to flexion, flexion to extension, left to right, and right to left, by a pure moment. Range of motion and velocity and acceleration patterns of the main and coupled motions were evaluated in six degrees of freedom by position changes of attached infrared light-emitting diodes recorded by cameras. Functional spinal units were tested in three surgical conditions (intact, discectomy, and unilateral facetectomy) under two preload conditions (no preload and 400-N preload). Discontinuous accelerations and decelerations (jerks) were computed in these motions and their location in relation to the main angular motion determined.Results.Jerks were observed in almost all motions, in the intact functional spinal units and after surgery. The parameters describing the magnitude of the jerk decreased with increasing component instability. In the sagittal plane, there was a surgical condition by motion direction interaction (P< 0.014) regarding the location of the jerk. Independent from the motion direction, the jerk occurred around the neutral position (in relation to the primary angular motion) in the intact functional spinal units, whereas it shifted from the neutral position toward the beginning of the motion with increasing component instability.Conclusion.The results suggest that a small jerk is a normal component of fast intersegmental motion. The jerk has a certain magnitude and location in an intact functional spinal unit, whereas both of the parameters describing the jerk are sensitive to component instability.

ISSN:0362-2436    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Study Design.A biomechanical study of the compressive creep behavior of the porcine intervertebral disc before and after frozen storage.Objective.To determine whether frozen storage alters the creep response, hydration, and nuclear swelling pressure of the intact intervertebral disc.Summary of Background Data.The mechanical response of the disc is dominated by swelling and fluid flow, whose effects are time-dependent. Because fluid content, which may change during storage, plays a significant role in the disc's time-dependent behavior, changes in mechanical response due to freezing may have been missed in previous studies that focused on time-independent behavior only.Methods.Porcine intervertebral discs were tested in repeated cycles of compressive creep either immediately postmortem or after 3 weeks of frozen storage. Swelling pressure and nuclear hydration were also measured in fresh and frozen discs. A fluid transport model was used to analyze the creep data.Results.The creep behavior of the intact porcine intervertebral disc is dramatically affected by frozen storage. The apparent permeability of the frozen discs was 82% higher than that of the fresh discs, and the swelling pressure of frozen discs was 25% lower in frozen discs (P< 0.01). The behavior of fresh and frozen discs became more dissimilar with repeated cycles of creep.Conclusions.In vitrotests of frozen porcine intervertebral discs do not represent fresh behavior. Frozen storage appears to permanently alter disc behavior. The precise nature of any freezing-induced damage, and whether frozen storage similarly affects human discs, remains to be seen.

ISSN:0362-2436    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Study Design.Biochemical study of human intervertebral discs collected at surgery from patients with low back pain associated with disc degeneration or scoliosis. Matrix metalloproteinases were studied by quantitative zymography.Objective.To determine whether changes in the expression of matrix metalloproteinases will bring about tissue remodelling that contributes to the progressive nature and pathology of these diseases of the intervertebral disc.Summary of Background Data.The diseases of the intervertebral disc, degenerative disc disease and scoliosis, are both characterized by changes in the extracellular matrix components that will affect the mechanical function of the tissue. Matrix metalloproteinases are known to have the capability of degrading all the known extracellular matrix components of the disc.Methods.Matrix metalloproteinases 2 and 9 were detected by gelatin-gel zymography and quantified by laser scanning densitometry. Both pro and active forms of the enzymes were measured. Thirty-four discs from patients with low back pain and 29 from patients with scoliosis were investigated.Results.A correlation was found between the increasing levels of matrix metalloproteinases 2 and 9 and the grade of degenerative disc disease. In addition, the levels of these enzymes show a differential expression across the scoliotic disc with the highest levels in samples taken from the convexity of the curve.Conclusions.The difference between the concave and convex side of the scoliotic curve indicates that mechanical loads might influence the expression of these enzymes. The increased expression of these enzymes in both degenerative disc disease and scoliosis strongly suggests that they may affect the progressive nature of these diseases.

ISSN:0362-2436    

出版商:OVID    

年代:1997

数据来源: OVID