Biomechanics of the Lumbosacral Nerve Roots

Does Improvement towards a Normal Cervical Sagittal Configuration Aid in the Management of Lumbosacral Radiculopathy: A Randomized Controlled Trial

A randomized controlled study with a six-month follow-up was conducted to investigate the effects of sagittal head posture correction on 3D spinal posture parameters, back and leg pain, disability, and S1 nerve root function in patients with chronic discogenic lumbosacral radiculopathy (CDLR). Participants included 80 (35 female) patients between 40 and 55 years experiencing CDLR with a definite hypolordotic cervical spine and forward head posture (FHP) and were randomly assigned a comparative treatment control group and a study group. Both groups received TENS therapy and hot packs, additionally, the study group received the Denneroll cervical traction orthotic. Interventions were applied at a frequency of 3 x per week for 10 weeks and groups were followed for an additional 6-months. Radiographic measures included cervical lordosis (CL) from C2–C7 and FHP; postural measurements included: lumbar lordosis, thoracic kyphosis, trunk inclination, lateral deviation, trunk imbalance, surface rotation, and pelvic inclination. Leg and back pain scores, Oswestry Disability Index (ODI), and H-reflex latency and amplitude were measured. Statistically significant differences between the groups at 10 weeks were found: for all postural measures, CL (p = 0.001), AHT (p = 0.002), H-reflex amplitude (p = 0.007) and latency (p = 0.001). No significant difference for back pain (p = 0.2), leg pain (p = 0.1) and ODI (p = 0.6) at 10 weeks were identified. Only the study group’s improvements were maintained at the 6-month follow up while the control groups values regressed back to baseline. At the 6-month follow-up, it was identified in the study group that improved cervical lordosis and reduction of FHP were found to have a positive impact on 3D posture parameters, leg and back pain scores, ODI, and H-reflex latency and amplitude.

The effect of spinal position on sciatic nerve excursion during seated neural mobilisation exercises: an in vivo study using ultrasound imaging

Objectives

Research has established that the amount of inherent tension a peripheral nerve tract is exposed to influences nerve excursion and joint range of movement (ROM). The effect that spinal posture has on sciatic nerve excursion during neural mobilisation exercises has yet to be determined. The purpose of this research was to examine the influence of different sitting positions (slump-sitting versus upright-sitting) on the amount of longitudinal sciatic nerve movement during different neural mobilisation exercises commonly used in clinical practice.

Methods

High-resolution ultrasound imaging followed by frame-by-frame cross-correlation analysis was used to assess sciatic nerve excursion. Thirty-four healthy participants each performed three different neural mobilisation exercises in slump-sitting and upright-sitting. Means comparisons were used to examine the influence of sitting position on sciatic nerve excursion for the three mobilisation exercises. Linear regression analysis was used to determine whether any of the demographic data represented predictive variables for longitudinal sciatic nerve excursion.

Results

There was no significant difference in sciatic nerve excursion (across all neural mobilisation exercises) observed between upright-sitting and slump-sitting positions (P = 0.26). Although greater body mass index, greater knee ROM and younger age were associated with higher levels of sciatic nerve excursion, this model of variables offered weak predictability (R² = 0.22).

Discussion

Following this study, there is no evidence that, in healthy people, longitudinal sciatic nerve excursion differs significantly with regards to the spinal posture (slump-sitting and upright-sitting). Furthermore, although some demographic variables are weak predictors, the high variance suggests that there are other unknown variables that may predict sciatic nerve excursion. It can be inferred from this research that clinicians can individualise the design of seated neural mobilisation exercises, using different seated positions, based upon patient comfort and minimisation of neural mechanosensitivity with the knowledge that sciatic nerve excursion will not be significantly influenced.

Slump Test: Effect of Contralateral Knee Extension on Response Sensations in Asymptomatic Subjects and Cadaver Study

STUDY DESIGN

Part 1: A randomized, single-blind study on the effect of contralateral knee extension on sensations produced by the slump test (ST) in asymptomatic subjects. Part 2: A cadaver study simulating the nerve root behavior of part 1.

OBJECTIVE

Part 1: Test if contralateral knee extension consistently reduces normal stretch sensations with the ST.Part 2: Ascertain in cadavers an explanation for the results.

SUMMARY OF BACKGROUND DATA

In asymptomatic subjects, contralateral knee extension reduces stretch sensations with the ST. In sciatica patients, contralateral SLR also can temporarily reduce sciatica. We studied this methodically in asymptomatic subjects before considering a clinical population.

METHODS

Part 1: Sixty-one asymptomatic subjects were tested in control (ST), sham, or intervention (contralateral ST) groups and their sensation response intensity compared.Part 2: Caudal tension was applied to the L5 nerve root of 3 cadavers and tension behavior of the contralateral neural tissue recorded visually.

RESULTS

Part 1: Reduction of stretch sensations occurred in the intervention group but not in control and sham groups (P ≤ 0.001).Part 2: Tension in the contralateral lumbar nerve roots and dura reduced in a manner consistent with the responses in the intervention (contralateral ST) group.

CONCLUSION

Part 1: In asymptomatic subjects, normal thigh stretch sensations with the ST reduced consistently with the contralateral ST, showing that this is normal and may now be compared with patients with sciatica.Part 2: Contralateral reduction in lumbar neural tension with unilateral application of tension-producing movements also occurred in cadavers, supporting the proposed explanatory hypothesis.

Chronic pain and the thoracic spine

In recent years there has been an increased interest in pain neuroscience in physical therapy.1,2 Emerging pain neuroscience research has challenged prevailing models used to understand and treat pain, including the Cartesian model of pain and the pain gate.2-4 Focus has shifted to the brain's processing of a pain experience, the pain neuromatrix and more recently, cortical reorganisation of body maps.2,3,5,6 In turn, these emerging theories have catapulted new treatments, such as therapeutic neuroscience education (TNE)7-10 and graded motor imagery (GMI),11,12 to the forefront of treating people suffering from persistent spinal pain. In line with their increased use, both of these approaches have exponentially gathered increasing evidence to support their use.4,10 For example, various randomised controlled trials and systematic reviews have shown that teaching patients more about the biology and physiology of their pain experience leads to positive changes in pain, pain catastrophization, function, physical movement and healthcare utilisation.7-10 Graded motor imagery, in turn, has shown increasing evidence to help pain and disability in complex pain states such as complex regional pain syndrome (CRPS).11,12 Most research using TNE and GMI has focussed on chronic low back pain (CLBP) and CRPS and none of these advanced pain treatments have been trialled on the thoracic spine. This lack of research and writings in regards to the thoracic spine is not unique to pain science, but also in manual therapy. There are, however, very unique pain neuroscience issues that skilled manual therapists may find clinically meaningful when treating a patient struggling with persistent thoracic pain. Utilising the latest understanding of pain neuroscience, three key clinical chronic thoracic issues will be discussed - hypersensitisation of intercostal nerves, posterior primary rami nerves mimicking Cloward areas and mechanical and sensitisation issues of the spinal dura in the thoracic spine.

Diagnostic Accuracy of the Slump Test for Identifying Neuropathic Pain in the Lower Limb

STUDY DESIGN

Diagnostic accuracy study with nonconsecutive enrollment.

OBJECTIVES

To assess the diagnostic accuracy of the slump test for neuropathic pain (NeP) in those with low to moderate levels of chronic low back pain (LBP), and to determine whether accuracy of the slump test improves by adding anatomical or qualitative pain descriptors.

BACKGROUND

Neuropathic pain has been linked with poor outcomes, likely due to inadequate diagnosis, which precludes treatment specific for NeP. Current diagnostic approaches are time consuming or lack accuracy.

METHODS

A convenience sample of 21 individuals with LBP, with or without radiating leg pain, was recruited. A standardized neurosensory examination was used to determine the reference diagnosis for NeP. Afterward, the slump test was administered to all participants. Reports of pain location and quality produced during the slump test were recorded.

RESULTS

The neurosensory examination designated 11 of the 21 participants with LBP/sciatica as having NeP. The slump test displayed high sensitivity (0.91), moderate specificity (0.70), a positive likelihood ratio of 3.03, and a negative likelihood ratio of 0.13. Adding the criterion of pain below the knee significantly increased specificity to 1.00 (positive likelihood ratio = 11.9). Pain-quality descriptors did not improve diagnostic accuracy.

CONCLUSION

The slump test was highly sensitive in identifying NeP within the study sample. Adding a pain-location criterion improved specificity. Combining the diagnostic outcomes was very effective in identifying all those without NeP and half of those with NeP. Limitations arising from the small and narrow spectrum of participants with LBP/sciatica sampled within the study prevent application of the findings to a wider population.

LEVEL OF EVIDENCE

Diagnosis, level 4-.

Tibial nerve excursion during lumbar spine and hip flexion measured with diagnostic ultrasound

Ultrasound imaging provides a method for non-invasive in vivo measurement of nerve motion resulting from joint movement. This study measured the proximal excursion of the tibial branch of the sciatic nerve at the popliteal fossa during forward bending in healthy subjects. Long-axis image sequences of the nerve were analysed using frame-by-frame cross-correlation software that calculated the longitudinal and axial movement of the nerve. Proximal excursion was calculated from the hypotenuse of these values. The mean proximal excursion recorded was 12.2 mm (SD 2.2 mm, n = 24). The reliability of three repeat measurements was found to be excellent (ICC 0.97, 95% CI 0.93-0.99; SEM 0.7 mm, n = 21). The protocol described provides a reliable method for analysing tibial nerve movement that could prove useful in future clinical studies.

Comparison of longitudinal sciatic nerve movement with different mobilization exercises: an in vivo study utilizing ultrasound imaging

STUDY DESIGN

Controlled laboratory study using a single-group, within-subjects comparison.

OBJECTIVES

To determine whether different types of neural mobilization exercises are associated with differing amounts of longitudinal sciatic nerve excursion measured in vivo at the posterior midthigh region.

BACKGROUND

Recent research focusing on the upper limb of healthy subjects has shown that nerve excursion differs significantly between different types of neural mobilization exercises. This has not been examined in the lower limb. It is important to initially examine the influence of neural mobilization on peripheral nerve excursion in healthy people to identify peripheral nerve excursion impairments under conditions in which nerve excursion may be compromised.

METHODS

High-resolution ultrasound imaging was used to assess sciatic nerve excursion at the posterior midthigh region. Four different neural mobilization exercises were performed in 31 healthy participants. These neural mobilization exercises used combinations of knee extension and cervical spine flexion and extension. Frame-by-frame cross-correlation analysis of the ultrasound images was used to calculate nerve excursion. A repeated-measures analysis of variance and isolated means comparisons were used for data analysis.

RESULTS

Different neural mobilization exercises induced significantly different amounts of sciatic nerve excursion at the posterior midthigh region (P<.001). The slider exercise, consisting of the participant performing simultaneous cervical spine and knee extension, resulted in the largest amount of sciatic nerve excursion (mean ± SD, 3.2 ± 2.0 mm). The amount of excursion during the slider exercise was slightly greater (mean ± SD, 2.6 ± 1.5 mm; P = .002) than it was during the tensioner exercise (simultaneous cervical spine flexion and knee extension). The single-joint neck flexion exercise resulted in the least amount of sciatic nerve excursion at the posterior midthigh (mean ± SD, -0.1 ± 0.1 mm), which was significantly smaller than the other 3 exercises (P<.001).

CONCLUSION

These findings are consistent with the results of previous research that has examined median nerve excursion associated with different neural mobilization exercises. Such nerve excursion supports theories of nerve motion associated with cervical spine and extremity movement, as generalizable to the lower limb.

Pathomechanisms of sciatica in lumbar disc herniation: effect of periradicular adhesive tissue on electrophysiological values by an intraoperative straight leg raising test

STUDY DESIGN

This study is aimed to investigate the changes of nerve root functions during the straight leg raising (SLR) test in vivo.

OBJECTIVE

To investigate the relationship between nerve root movement and the electrophysiological values during an intraoperative SLR test.

SUMMARY OF BACKGROUND DATA

The SLR test is one of the most significant signs for making a clinical diagnosis of lumbar disc herniation. A recent study showed that intraradicular blood flow apparently decreased during the SLR test in patients with disc herniation.

METHODS

The study included 32 patients who underwent microdiscectomy. During the surgery, the nerve root motion affected by the hernia was observed during the SLR test. The patients' legs were allowed to hang down to the angle at which sciatica had occurred and the change of nerve root action potentials was measured. After removal of the hernia, a similar procedure was repeated. The periradicular specimens collected during surgery were examined by light and electron microscope.

RESULTS

In all patients intraoperative microscopy revealed that the hernia was adherent to the dura mater of the nerve roots. During the SLR test, the limitation of nerve root movement occurred by periradicular adhesive tissue and amplitude of action potential showed a sharp decrease at the angle that produced sciatica. After removal of the hernia, all the patients showed smooth gliding of the nerve roots during the test, and there was no marked decrease of amplitude. Our data suggest that temporary ischemic changes in the nerve root cause transient conduction disturbances. Pathologic examination showed that the periradicular tissue consisted of the granulation with vascularization and many inflammatory cell infiltrations.

CONCLUSION

The presence of periradicular fibrosis will compound the nerve root pain by fixing the nerve in one position, thereby increasing the susceptibility of the nerve root to tension or compression.

PATHOANATOMIC BASIS FOR STRETCH-INDUCED LUMBAR NERVE ROOT INJURY WITH A REVIEW OF THE LITERATURE

OBJECTIVE

Persistent pain originating from a dysfunctional lumbar motion segment poses significant challenges in the clinical arena. Although the predominance of the existing spine literature has addressed nerve root compression as the principal cause of pain, it is equally likely that a stretch mechanism may be responsible for all or part of the pathology.

METHODS

The literature supporting the role of stretch damage as a primary cause of nerve root injury and pain was systematically reviewed. Pathoanatomic considerations between nerve roots and juxtaposed environment are described and correlated with the available literature. Potential anatomic relationships that may lead to stretch-induced injury are delineated.

RESULTS

A dynamic lumbar functional spinal unit that encloses a tethered nerve root can create significant stretch and/or compression. This phenomenon may be present in a variety of pathological conditions. These include anterior, posterior, and rotatory olisthesis as well as degenerative conditions such as the loss of disc interspace height and frank multisegment spinal deformity. Although numerous studies have demonstrated that stretch can result in nerve damage, the pathophysiology that may associate nerve stretch with chronic pain has yet to be determined.

CONCLUSION

The current literature concerning stretch-related injury to nerve roots is reviewed, and a conceptual framework for its diagnosis and treatment is proposed and graphically illustrated using cadaveric specimens. The dynamic biomechanical and functional interrelationships between neural structures and adjacent connective tissue elements are particularly important in the face of spinal deformity.

Physical assessment of lower extremity radiculopathy and sciatica

OBJECTIVE

The purpose is to describe active and passive physical maneuvers that provoke or alleviate lumbosacral radiculopathy and/or sciatica to demonstrate how these maneuvers function in common orthopedic and neurological tests/signs.

METHODS

Descriptions of the maneuvers and their countermaneuvers are provided to establish an understanding of their mechanisms and influence on lumbosacral nerve roots and the sciatic nerve. Common tests and signs for lower extremity radiculopathy and sciatica are described to demonstrate the clinical application of the maneuvers. Combinations of common tests are also offered to improve examination efficiency.

RESULTS

Understanding how each maneuver contributes individually or in combination with standard tests will enhance the reader's examination skills.

CONCLUSION

Improved examination skills lead to improved diagnosis and differential diagnosis of lower extremity radiculopathy and sciatica.

Conservative treatment of a patient with syringomyelia using chiropractic biophysics protocols

OBJECTIVE

To present a case of a 41-year-old man with syringomyelia and intractable pain and the subsequent reduction of symptoms.

CLINICAL FEATURES

This patient acquired a traumatically induced syrinx in his upper cervical spinal cord after he fell approximately 9 feet and landed on his head, upper back, and neck 9 years before presenting for care. He was diagnosed with a spinal cord cyst (syrinx), located at approximately C2 through C4 after magnetic resonance imaging. In 1995, the patient underwent occipitoatlantal decompression surgery, which improved his symptoms for a short time.

INTERVENTION AND OUTCOMES

The patient was treated using Clinical Biomechanics of Posture protocol. The patient was seen 26 times over the course of 3 weeks. His scale for pain severity decreased 50% and other subjective complaints decreased. His posture improved based upon pretreatment and posttreatment lateral cervical radiographs, showing a change from a 10 degrees lordosis with midcervical kyphosis to a 30 degrees lordosis. One-year follow-up examination showed stable improvement in the cervical lordosis and pain intensity.

CONCLUSION

This case represents a change in subjective and objective measurements after conservative chiropractic care. This case provides an example that structural rehabilitation may have a positive effect on symptoms of a patient with syringomyelia.

Intrathecal Movement and Tension of the Lumbosacral Roots Induced by Straight-Leg Raising

OBJECTIVE

To obtain quantitative biomechanical data on the effects of different angles of straight-leg raising on intrathecal movements and tensions in the lumbosacral nerve roots in human cadavers.

DESIGN

Eight embalmed human cadavers with no gross spinal pathology and no limitations in hip motion were used. We performed reverse straight-leg raising by hanging the left leg down from the table with the knee extended while measuring the movement and tension of nerve roots L2, L3, L4, L5, and S1 in 10-degree intervals for straight-leg raising from 0 to 70 degrees.

RESULTS

The mean intrathecal movements at 70 degrees were 0.55 mm, 0.54 mm, 0.96 mm, 1.54 mm, and 2.31 mm for roots L2, L3, L4, L5, and S1, respectively. The movements were statistically significant at >50 degrees for root L5 and at >40 degrees for root S1 (P < 0.05). The tension in the nerve roots with increasing angle of straight-leg raising increased from roots L2 to S1. The mean tensions at 70 degrees of straight-leg raising were 141.25 g, 168.75 g, 228.75 g, 280.00 g, and 493.75 g for roots L2, L3, L4, L5, and S1, respectively. The difference in tension was significant at >70 degrees for roots L2, L3, and L4 roots, at >40 degrees for root L5 root, and at >10 degrees for root S1 (P < 0.05).

CONCLUSIONS

The intrathecal movement and tension of the lumbosacral roots induced by straight-leg raising were <2.5 mm and <500 g, respectively. The movement and tension induced by straight-leg raising tended to be greater in more distal segmental roots.

Changes in nerve root motion and intraradicular blood flow during intraoperative femoral nerve stretch test. Report of four cases

OBJECT

It is not known whether changes in intraradicular blood flow (IRBF) occur during the femoral nerve stretch test (FNST) in patients with lumbar disc herniation. An FNST was conducted in patients with lumbar disc herniation to observe the changes in IRBF, and results were then compared with clinical features.

METHODS

The study was composed of four patients with L3-4 disc herniation who underwent microdiscectomy. Patients were placed prone immediately before surgery, so that their knee flexed on the operating table with the hip joint kept in hyperextension, and the FNST was performed to confirm at which region pain developed in the anterolateral thigh. During the operation, the hernia-affected nerve roots were visualized under a microscope. The needle sensor of a laser Doppler flowmeter was then inserted into each nerve root immediately above the hernia, and the change in IRBF was measured during the intraoperative FNST. After removal of the herniated disc, a similar procedure was repeated and IRBF was measured again. The intraoperative FNST showed that the hernia compressed the nerve roots and there was marked disturbance of gliding, which was reduced to only a few millimeters. During the test, IRBF decreased by 92.8 to 100% (mean 96.9 +/- 3.7% [+/- standard error of the mean]) relative to the blood flow before the test. This study demonstrated that the blood flow in the nerve root is reduced when the nerve root is compressed in vivo.

CONCLUSIONS

The intraoperative FNST showed that the hernia compressd the nerve roots and there was marked disturbance of gliding, which was reduced to only a few millimeters. During the test, IRBF decreased by 92.8 to 100% (96.9 +/- 3.7% [mean +/- standard error of the mean]).

Three-dimensional analysis of the movement of lumbar spinal nerve roots in nonsimulated and simulated adhesive conditions

STUDY DESIGN

Biomechanical analysis of the movement of the lumbar spinal nerve roots (NRs).

OBJECTIVES

The characteristics of the movement of lumbar spinal NRs corresponding to the change of posture were three-dimensionally analyzed in nonsimulated and simulated adhesion conditions using a porcine model.

SUMMARY OF BACKGROUND DATA

There is a paucity of data on the movement of NRs.

MATERIALS AND METHODS

Thirty two NRs of four pig cadavers were investigated. (study 1) Two tantalum beads were sutured on respective NRs from L3 to L6. Five beads were put into each bony structure as reference points. The porcine body was put on the cage designed for three-dimensional radiostereometric analysis. Two oblique radiographs were simultaneously taken at flexion, neutral, and extension. (study 2) After study 1, either L4 NR was ligated onto the adjacent bone to mimic monoradicular adhesion. Radiographs were taken in the same manner. The movements of the beads on NRs relative to immobile standard points in each vertebra were analyzed.

RESULTS

The movement of NRs was characterized as a combination of stretching/slackening and pendulum motion. The distance that NRs were stretched/slackened, the excursion, and the angles that NRs moved were: 0.39 +/- 0.29 mm, 1.81 +/- 0.63 mm, and 10.46 +/- 5.93 degrees (in nonadhesion), and 0.30 +/- 0.20 mm, 1.02 +/- 0.50 mm, and 7.13 +/- 3.79 degrees (in simulated adhesion), respectively.

CONCLUSION

Adhesion might play a part in the pathogenesis of lumbar spinal disorders because mechanical irritation secondary to stretching/slackening and pendulum motion might be concentrated at the distal part of NRs, adjacent to adhesion site, which has less cerebrospinal fluid and is close to dorsal root ganglion.

Application of expanded inert polytetrafluorethylene membrane in prevention of post laminectomy fibrosis in wistar rats

Post laminectomy fibrosis in spine surgery has been responsible for a high rate of failure in a short or long term. Many of this patients develop chronic or recurrent pain after surgery of discal herniation, canal stenosis etc. Although there some doubts about the etiology of this problem, it was known that fibrosis interfere with the normal mobility of roots and spinal cord. This factor is considered as the most important aspect in the genesis of the surgical failures. To avoid postoperative fibrosis, a lot of materials of interposition between posterior spine muscles and dura mater were studied, without good response. This paper studied comparatively post laminectomy fibrosis in Wistar rats with the addition of the following materials to avoid it: control group (without interposition) and expanded inert polytetrafluoroethylene membrane (Preclude Spinal Membrane®). It was observed that accurate surgical technique apparently is an important factor to prevent the formation of abundant scar tissue and that the expanded inert polytetrafluoroethylene membrane is an inert material.

Differential Diagnosis and Management of Spinal Nerve Root-related Pain

Pain originating from spinal nerve roots demonstrates multiple pathogeneses. Distinctions in the patho-anatomy, biomechanics, and pathophysiology of spinal nerve roots contribute to pathology, diagnosis, and management of root-related pain. Root-related pain can emerge from the tension events in the dura mater and nerve tissue associated with primary disc related disorders. Conversely, secondary disc-related degeneration can produce compression on the nerve roots. This compression can result in chemical and mechanical consequences imposed on the nervous tissue within the spinal canal, lateral recess, intervertebral foramina, and extraforminal regions. Differences in root-related pathology can be observed between lumbar, thoracic, and cervical spinal levels, meriting the implementation of different diagnostic tools and management strategies.

Effects of ankle dorsiflexion on range and reliability of straight leg raising

The effect of dorsiflexion was investigated on range of passive straight leg raising (SLR) and on inter-rater reliability with 35 patients reporting unilateral lumbar pain with or without ipsilateral leg symptoms. Ranges of SLR and SLR with dorsiflexion (SLR/DF) to onset of lumbar or leg symptoms (P1) were independently measured using a gravity goniometer by pairs of different physiotherapists at two clinics. Dorsiflexion significantly reduced SLR range by a mean of 9 degrees across both samples. Similar high inter-rater reliability was found for SLR and SLR/DF in both pairs of physiotherapists. These data show that SLR and SLR/DF are reliable procedures when measured to P1 in the clinical environment and support previous findings that dorsiflexion reduces range of SLR.

The response to the slump test in a group of female whiplash patients

This study was undertaken to assess the difference between the response to the slump test in 40 asymptomatic and 20 symptomatic female subjects with cervical pain after whiplash injury. Areas and alterations of pain responses during the test, and ranges of movement of knee extension, were analysed. The results demonstrated that the addition of knee extension and left ankle dorsiflexion during the slump test produced a significant increase in the intensity of comparable cervical symptoms in the whiplash group. The whiplash group also showed a greater limitation in knee extension range of movement during the test than did the control group. These differences suggest that pathological changes of the neural system itself or adjacent tissues, affecting the mechanics of the neural system, may be a contributing factor to these patients' cervical symptoms.

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.

Use of lumbar extension, slump test, physical and neurological examination in the evaluation of patients with suspected herniated nucleus pulposus. A prospective clinical study

This prospective and consecutive study was designed to evaluate the validity of different clinical tests, e.g. lumbar extension in lying and slump test for patients with suspected herniated nucleus pulposus, in comparison with findings on computed tomography (CT) and/or magnetic resonance imaging (MRI) scan. There were 105 patients who were seen and examined by the senior author (for the sake of the study) at the Orthopaedic Physiotherapy Department, on an average of 5.5 days (range 0-21 days) before CT and/or MRI examination were carried out. There were 36 women and 69 men with an average age of 42.7 +/- 9.8 (range 19-64) years. According to the radiological findings on CT and/or MRI, the patients were divided into three groups: 52 patients with disc hernia, 41 patients with bulging discs and 12 patients without positive findings. The mean values with standard deviations of 25 variables of three diagnostic groups were studied. Multiple comparison adjustment according to Bonferroni showed significant differences for three variables that were of diagnostic value (lumbar range of motion for forward flexion, left side-bending in standing, and pain distribution during extension in standing). The agreement between clinical and radiological findings for type and level of diagnosis of disc herniation was accurate in 72 patients (69%). The diagnostic sensitivity for disc herniation was 82.6% and the specificity 54.7%.

[Models of pain development in radicular compression.]

The problem of nociception and pain development in radicular pain syndromes is not clarified. In the pathophysiology of pain of radicular compression caused by stenosis or disc prolapse, morphological complex nerve root/ganglion is the key structure. Chronic compression forces on the nerve structure cause structural changes. Structural deterioration is linked with a change in the electrical membrane properties of the affected nerve root. The membrane threshold shift in nociceptive fibers is an important prerequisite for pain perception in nerve root compression. New biochemical aspects in the pathophysiology of radicular syndromes are presented, which could explain the discrepancy between pain and objective clinical findings. The article concludes that a better understanding of the nerve root pathophysiology will bring a more differentiated pain-management strategy.

Evaluation of a new work seat for industrial sewing operations: results of three field studies

A newly developed work seat for industrial sewing operations was compared with a traditional sewing work seat to evaluate the effectiveness of design features. The new seat was designed with special seat-pan and backrest features to accommodate the musculoskeletal geometry of a low sit-stand posture. The seat-pan consisted of a pelvic support which supported the ischial tuberosities and areas behind them, and a thigh support which maintained the thighs at a 15 degrees downward angle, resulting in a 105 degrees trunk-thigh angle. The backrest consisted of a lumbar support which preserved lumbar lordosis and a thoracic support which supported the upper back during backward leaning. The traditional work seat was similar to an office chair (i e, a large horizontal seat-pan and a wide backrest) with the exception of having a higher than normal seat-height. This investigation consisted of three studies to compare the seats: (1) A user comfort and acceptance experiment which compared the initial psychophysical responses of 50 industrial sewers when introduced to the new seat; (2) a backrest usage experiment which compared the duration of backrest use among 10 industrial sewers; and (3) a follow-up experiment to evaluate chair preference after extended use of the new seat. The results of the user comfort and acceptance experiment found that the new work seat had greater comfort and user preference; the results of the backrest usage experiment found that the new seat had greater backrest use than the traditional seat; the results of the follow-up experiment found that the preference for the new seat was maintained over time and not due to a Hawthorne Effect.

Biomechanics of the lumbar spinal canal

The normal mobility of the vertebral column, particularly in the cervical and lumbar regions, gives rise to major changes in the length and lumen of the spinal canal and of its volume. Its contents must therefore adapt to these changes without disturbance to their several functions. The contents are partly fluid, partly neural tissue, but also connective tissue: all with differing physical characteristics. Thus, all respond differently to changes in the space in which they are contained. When pathological changes supervene, the spinal meninges, the spinal cord and nerve roots may be adversely affected by the increases in the resting tension, by compression or bending stresses. Because the mechanical state of one region of the spine has a more than local effect, all these factors have to be considered-particularly for the interpretation of the symptoms and clinical signs of lumbosacral root pathology.

Vascular and neural pathology of lumbosacral spinal stenosis

During a study of the intrinsic vasculature of the lumbosacral spinal nerve roots in cadavers, a typical case of spinal stenosis was encountered. A review of the antemortem anamnesis revealed that this patient had had an intermittent claudication of the cauda equina. Investigation of the concomitant vascular and histopathological alterations of the affected nerve roots suggested that the claudication may have resulted from ectopic nerve impulse discharges elicited by rapid changes in the blood supply following exertion. The unexpectedly slight apparent neural deficit relative to observed root damage may be attributed to a neuronal plasticity within the spinal cord that permitted functional compensations to develop during the slow acquisition of the chronic nerve root pathology.

Recent advances in the treatment of low back pain

There is at the present time an epidemic of low back pain in the industrialized countries. Although the exact origin of such pain is still unknown, there is increasing awareness that the outcome is usually favourable. Only some 10% of those suffering an acute episode of back pain are incapacitated for more than 6 weeks. The causes of long standing back pain are being identified in an increasing number of patients. They include anatomical and pathological disturbances in the motion segment as well as psychological, social and political causes. There are numerous factors which influence the pathophysiology of the motion segment. The degree of loading has been successfully measured and delineated for various postures and exercises, including those at work. The nutritional pathways to the disc have been established and the effect of various external factors measured. Movement is good for the disc and the importance of continuous passive motion for the healing of diseased or injured connective tissues is not established. Activation of large muscle groups increases the production of the body's pain reducing encephalins. Early diagnosis and early mobilisation of the patient should be of benefit, and long term bed rest and inactivity must be prevented. Fewer cases will need operation in the future. Improved imaging techniques and better methods of operation and fixation will help those few who have a definite pathological lesion amenable to surgery.

The mechanism of sciatic pain relief by chemonucleolysis

Chemonucleolysis must relieve sciatic pain by some means other than the removal of the disc protrusion from the neural canal, because the protrusion characteristically persists despite the resolution of sciatic pain. This paper analyzes the mechanism of symptom production in sciatica and identifies how chemonucleolysis relieves these symptoms.Pressure can be exerted on a nerve root by a disc protrusion without compression against the posterior wall of the neural canal. This pressure is the result of tension produced in the nerve root when it is deformed by the disc protrusion. A previously unrecognized principle of nerve root-disc protrusion mechanics is identified. For a given disc protrusion, narrowing the disc reduces the tension in the nerve root and therefore the pressure on the nerve root; conversely, widening the disc increases the tension and pressure on the nerve root. Disc narrowing is in itself a mechanism by which chemonucleolysis relieves sciatic pain.

A surgical approach through the pedicle to protruded thoracic discs

Three cases of thoracic disc herniation presenting with signs of spinal cord compression are reported. The patients were operated on by an approach through a midline incision in which a pedicle is removed. Two patients were cured and one has improved.

Lateral extracavitary approach to traumatic lesions of the thoracic and lumbar spine

The lateral extracavitary approach to the spine was used for resection of displaced bpne and disc located anterior to the dura in 62 patients with traumatic lesions of the thoracic and lumbar spine. Fifty-two patients had closed vertebral fractures and 10 had gunshot wounds. The spinal cord was involved in 44 patients, and the cauda equina in 18. A spinal subarachnoid block was demonstrated in 17 of 57 preoperative gas myelograms. Evoked potential recordings, although related to preception of joint rotation, tended to reflect the overall neurological condition and had some prognostic value. Significant improvement followed surgery in 46 patients with incomplete neurological lesions, and one was transiently worse. Before operation 18 patients were able to walk; nine with assistance and nine without. After operation 47 patients were able to walk; 12 with assistance and 35 without. Adequate bladder function was present in 17 patients before surgery, and in 44 after surgery. A laminectomy had been done previously in 16 patients, 11 of whom improved significantly after anterior resection. Spine fusions were required in 26 patients, five of whom had a prior laminectomy. The major factor in the pathogenesis of the incomplete neurological deficit appeared to be distortion of the cord and roots by displaced bone and disc. Consequently, the primary object of treatment was the restoration and maintenance of normal anatomical relationships between the spinal cord or cauda equina and the spinal canal.

Spontaneous incarcerated herniation of the spinal cord into a vertebral body: a unique cause of paraplegia. Case report

✓ A case of progressive paraparesis is reported in which the normal spinal cord herniated through a defect in the ventral meninges and dura and became incarcerated in a cavity in the dorsal aspect of the body of T-7. Progress of the paraparesis was arrested by reduction of the hernia.