Transpedicular stabilization in spinal and vertebral column injuries in thoracic and lumbar spine segments

The authors present their own experience in application of transpedicular internal stabilization of the thoracic and lumbar spine. Clinical analysis was carried out in a group of 12 patients after vertebral column and spinal trauma managed surgically in the Department of Neurosurgery in Poznań between 1.06.95 and 31.12.96. Age of patients ranged from 19 to 56 years (mean age 35.08 +/- 13.04 yrs.). The level of vertebral fracture was as follows: thoracic (2 cases), thoraco-lumbar (6 cases) and lumbar (4 cases). Three patients were completely paraplegic. All patients underwent posterior or posterolateral surgical approach. The fractured parts of bones, translocated into vertebral canal were removed and nervous structures were decompressed. Transpendicular stabilization was performed after the decompression. Improvement of neurological condition was observed in 8 patients.     

Stability of posterior spinal instrumentation and its effects on adjacent motion segments in the lumbosacral spine

STUDY DESIGN: An in vitro biomechanical analysis of three anterior instability patterns was performed using calf lumbosacral spines. Stiffness of the constructs was compared, and segmental motion analyses were performed. OBJECTIVES: To clarify the factors that alter the stability of the spinal instrumentation and to evaluate the influence of instrumentation on the residual intact motion segments. SUMMARY OF BACKGROUND DATA: Recently, many adverse effects have been reported in fusion augmented with rigid instrumentation. Only few reports are available regarding biomechanical effects of stability provided by spinal instrumentation and its effects on residual adjacent motion segments in the lumbar-lumbosacral spine. METHODS: Eighteen calf lumbosacral spine specimens were divided into three groups according to instability patterns--one-level, two-level, and three-level disc dissections. Six constructs were cyclically tested in rotation, flexion-extension, and lateral bending of intact spines, of destabilized spine, and of spines with four segmental posterior instrumentation systems used to extend the levels of instability (Cotrel-Dubousset compression hook and three transpedicular screw fixation systems). During each test, stiffness values and segmental displacements were measured. RESULTS: The rigidity of the instrumented construct increased as the fixation range became more extensive. Although application of the instrumentation effectively reduced the segmental motion of the destabilized vertebral level, the motion at the destabilized level tended to increase as the number of unstable vertebral levels increased, and the fixation range of the instrumentation became more extensive. Instrumented constructs produced higher segmental displacement values at the upper residual intact motion segment when compared with those of the intact spine. In contrast, the instrumented constructs decreased their segmental displacement values at the lower residual intact motion segment with higher magnitude of the translational (shear) motion taking place compared with the intact spine in flexion-extension and lateral bending. These changes in the motion pattern became more distinct as the fixation range became more extensive. CONCLUSIONS: As segmental spinal instrumentation progresses from one level to three levels, the overall torsional and flexural rigidity of the system increases. However, segmental displacement at the site of simulated instability becomes more obvious. Application of segmental instrumentation changes the motion pattern of the residual intact motion segments, and the changes in the motion pattern become more distinct as the fixation range becomes more extensive and as the rigidity of the construct increases.     

Quantitative assessment of the motion of the lumbar spine in the low back pain population and the effect of different spinal pathologies of this motion

There are few objective means by which disability caused by low back pain (LBP) can be quantified. The purpose of this study was to investigate the usefulness of motion measurements in the assessment of LBP. The motion characteristics of 138 LBP subjects were investigated, and the data compared with a previously published database of normal subjects. Values of range of motion and angular velocity were obtained for all subjects in each plane of motion. Analysis of these motion characteristics demonstrated significant differences (P < 0.0001) between the two populations; however both populations demonstrated considerable intersubject variation. Multiple regression analysis revealed that some of the variance in the LBP population was attributable to the underlying diagnosis. Patients with a spondylolisthesis tended to be hypermobile whilst those with spinal stenosis, disc prolapse or degenerative disc disease tended to be hypomobile. All diagnostic groups showed impairments in their velocity characteristics.     

Poroelastic creep response analysis of a lumbar motion segment in compression

The nonlinear three-dimensional poroelastic creep response of a lumbar motion segment under a constant axial compression (400, 1200, or 2000 N) is investigated for a period of 2 h. The role of facet joints, strain-dependent variable permeability, boundary pore pressure, and coupled sagittal rotation on response is studied. Biomechanics of annulus excision, nucleotomy, and facetectomy are also investigated. Both material and geometric nonlinearities are considered. The annulus bulk is modelled as a nonhomogeneous composite of collagenous fibers and annulus bulk. As time progresses, axial displacement increases, pore pressure decreases, annulus bulk undergoes larger compressive stresses, fiber layers become slack, and facets carry larger loads. Surgical alterations markedly soften the temporal response and increase facets forces. In contrast, the strain-dependent variable permeability and boundary pore pressure stiffen the response and decrease forces on the facets. Changes in the nucleus fluid content, facet joints, boundary pore pressure, and disc permeability markedly influence the lumbar biomechanics.     

Surgical treatment of lumbar spinal stenosis in the elderly

148 elderly patients, aged 70 years or more, diagnosed as having lumbar spinal stenosis, were operated upon at our institution during 1983 to 1995. Totally 161 operative procedures were performed. We analysed retrospectively the results of the surgical treatment. The most frequently performed procedure was multisegmental laminectomy, in 32% interlaminar fenestration and laminotomy were done. In 9 cases fusion was indicated, two of them being secondary operations. The mean hospital stay was 11 days. The morbidity was 6%, and there was one fatality (0.6%). The outcome was determined according to the six-grade classification proposed by Pappas and Sonntag [25]. Overall, in 91% of cases satisfactory-to-excellent results could be achieved. We conclude, that in elderly patients with symptomatic lumbar spinal stenosis, with no evidence of instability, decompressive surgery without stabilisation can be done in the majority of patients with low morbidity and high expectation of clinical improvement.     

Measurement properties of a self-administered outcome measure in lumbar spinal stenosis

STUDY DESIGN: The measurement properties and validity of a newly developed patient questionnaire for the assessment of patients with lumbar spinal stenosis was tested in an ongoing prospective multicenter observational study of patients undergoing decompressive surgery in three teaching hospitals. OBJECTIVE: The goal of the study was to develop a short, self-administered questionnaire on symptom severity, physical functional status, and patient satisfaction. SUMMARY OF BACKGROUND DATA: The measure is intended to complement existing generic measures of spinal-related disability and health status. The questionnaire includes three scales with seven questions on symptom severity, five on physical function, and six on satisfaction. METHODS: The internal consistency of the scales was assessed with Cronbach's coefficient alpha on cross-sectional data from 193 patients before surgery. The test-retest reliability was assessed on data from a random sample of 23 patients using Spearman's rank correlation coefficient. The responsiveness was assessed on 130 patients with 6-month follow-up data using the standardized response mean. RESULTS: The test-retest reliability of the scales ranged from 0.82 to 0.96, the internal consistency from 0.64 to 0.92, and the responsiveness from 0.96 to 1.07. The direction, statistical significance, and strength of hypothesized relationships with external criteria were as expected. CONCLUSIONS: This short self-administered spinal stenosis measure is reproducible, internally consistent, valid, and highly responsive. It can be used to complement generic instruments in outcome assessment of patients with lumbar spinal stenosis.     

Influence of load orientation on the posteroanterior stiffness of the lumbar spine

OBJECTIVE: To compare the posteroanterior (PA) stiffness of the lumbar spine when the load is applied in a vertical direction with the stiffness when the load is applied perpendicular to the spinal curve. DESIGN: The PA stiffness of the lumbar spine was assessed at L1, L3 and L5 on 24 normal subjects using a mechanical spinal mobilization apparatus. The PA stiffness was measured when the load was applied in a vertical direction and when the load was applied perpendicular to the spinal curve at the level being tested. SETTING: A university biomechanics laboratory. DESIGN: A repeated-measures design with pseudorandomization of the order of testing. MAIN OUTCOME MEASURES: Stiffness variable derived from force-displacement curve. RESULTS: The difference in PA stiffness between the two loading conditions was small at all three levels tested. The stiffness of L5 was significantly lower when the load was applied in the vertical direction compared with the application of the load in the perpendicular direction (p = .0001). Altering the angle of inclination of PA load had no statistically significant effect on PA stiffness at L1 and L3. The mean PA stiffness of the lumbar spine increased in a caudal direction (L1 = 10.4 N/mm, L3 = 11.4 N/mm, L5 = 11.6 N/mm). CONCLUSION: The orientation of the PA load had only a small effect on the measured PA stiffness and would be unlikely to be detected during manual examination of the spine. However, changes in the orientation of the PA load may be important when considered in relation to the symptom response.     

Biphasic response of spinal GABAergic neurons after a lumbar rhizotomy in the adult rat

The expression of gamma-aminobutyric acid (GABA) and of the isoforms of the enzyme involved in its synthesis, glutamic acid decarboxylase (GAD), is modified in several rat brain structures in different injury models. The aim of the present work was to determine whether such plasticity of the GABAergic system also occurred in the deafferented adult rat spinal cord, a model where a major reorganization of neural circuits takes place. GABAergic expression following unilateral dorsal rhizotomy was studied by means of non-radioactive in situ hybridization to detect GAD67 mRNA and by immunohistochemistry to detect GAD67 protein and GABA. Three days following rhizotomy the number of GAD67 mRNA-expressing neurons was decreased in the superficial layers of the deafferented horn, while GABA immunostaining of axonal fibres located in this region was highly increased. Seven days after lesion, on the other hand, many GAD67 mRNA-expression neurons were bilaterally detected in deep dorsal and ventral layers, this expression being correlated with the increased detection of GAD67 immunostained somata and with the reduction of GABA immunostaining of axons. GABA immunostaining was frequently found to be associated with reactive astrocytes that exhibited intense immunostaining for glial fibrillary acidic protein (GFAP) but remained GAD67 negative. These results indicate that degeneration of afferent terminals induces a biphasic response of GABAergic spinal neurons located in the dorsal horn and show that many spinal neurons located in deeper regions re-express GAD67, suggesting a possible participation of the local GABAergic system in the reorganization of disturbed spinal networks.     

A case of a lumbar spinal synovial cyst located on the midline]

We report a case of lumbar spinal synovial cyst located on the midline. A 72-year-old man was admitted to our hospital with the chief complaint of low back pain radiating to the left buttock and posterior thigh. An MR image revealed an extradural cystic lesion adjacent to the dorsal side of the dural sac at the L4-5 level. The cyst was remote from the facet joints and existed on the midline just in front of the L4 lamina. A CT scan showed a concave deformity of the ventral aspect of the L4 lamina because of compression by the cyst. The patient underwent L4 laminectomy and total removal of the cyst. The cyst was in contact with the anterior surface of the ligamentum flavum and it had no connection with the facet joint. In the histological examination, the cyst was multilobular and lined with synovial epithelium. Therefore the cyst was diagnosed as a synovial cyst. After the operation, the pain radiating to the buttock and thigh completely disappeared. Intraspinal synovial cysts are usually located in the lower lumbar spine and most of them are adjacent to the facet joint. The cysts that are located on the midline are very rare. We review previous reports and discuss clinical and pathological features of spinal synovial cysts.     

Reliability of pain and stiffness assessments in clinical manual lumbar spine examination

BACKGROUND AND PURPOSE: The purpose of this study was to determine the intertherapist reliability of judgments of stiffness and pain at L-1 to L-5 made using posteroanterior (PA) central pressure testing. SUBJECTS: Three pairs of manipulative physical therapists with a minimum of 5 years of experience were asked to rate pain and stiffness in a total of 90 patients with low back pain. METHODS: Each pair of therapists assessed 30 patients within their own clinic, using their preferred technique to perform an examination using the PA central pressure test at the five lumbar levels. Each pair of therapists recorded their ratings of pain and stiffness. Reliability of judgments was evaluated by intraclass correlation coefficients (ICC) and percentage of exact agreement scores. RESULTS: The ICC values for pain judgments for the group as a whole ranged from .67 to .72, with agreement scores ranging from 31% to 43%. The ICC values for stiffness judgments ranged from .03 to .37, with agreement scores ranging from 21% to 29%. CONCLUSION AND DISCUSSION: Judgments of stiffness made by experienced manipulative physical therapists examining patients in their own clinics were found to have poor reliability, whereas pain judgments had good reliability. Further investigation of this test is required in order to develop a more reliable method of assessing PA stiffness.     

Role of ligaments and facets in lumbar spinal stability

STUDY DESIGN: The issue of segmental stability using finite element analysis was studied. Effect of ligament and facet (total and partial) removal and their geometry on segment response were studied from the viewpoint of stability. OBJECTIVES: To predict factors that may be linked to the cause of rotational instabilities, spondylolisthesis, retrospondylolisthesis, and stenosis. SUMMARY OF BACKGROUND DATA: The study provides a comprehensive study on the role of facets and ligaments and their geometry in preserving segmental stability. No previous biomechanical study has explored these issues in detail. METHODS: Three-dimensional nonlinear finite element analysis was performed on L3-L4 motion segments, with and without posterior elements (ligaments and facets), subjected to sagittal moments. Effects of ligament and facet (partial and total) removal and their orientations on segment response are examined from the viewpoint of stability. RESULTS: Ligaments play an important role in resisting flexion rotation and posterior shear whereas facets are mainly responsible for preventing large extension rotation and anterior displacement. Facet loads and stresses are high under large extension and anterior shear loading. Unlike total facetectomy, selective removal of facets does not compromise segmental stability. Facet loads are dependent on spatial orientation. CONCLUSIONS: Rotational instability in flexion or posterior displacement (retrospondylolisthesis) is unlikely without prior damage of ligaments, whereas instability in extension rotation or forward displacement (spondylolisthesis) is unlikely before facet degeneration or removal. The facet stress and displacement distribution predicts that facet osteoarthritis or hypertrophy leading to spinal stenosis is most likely under flexion-anterior shear loading. Selective facetectomy may restore spinal canal size without compromising the stability of the segment. A facet that is more sagittally oriented may be linked to the cause of spondylolisthesis, whereas a less transversely oriented facet joint may be linked to rotational instabilities in extension.     

An investigation of the relationship between low back pain and lumbar posteroanterior stiffness

OBJECTIVE: To investigate the relationship between low back pain (LBP) and lumbar posteroanterior (PA) stiffness. DESIGN: A repeated-measures design was used to measure lumbar posteroanterior stiffness on two occasions in subjects with and without LBP. SUBJECTS: Twenty-five subjects with acute or subacute LBP and twenty-five pain-free subjects participated. Pain subjects reported pain on the application of a manual PA force to the lumbar spine and had no contraindication to PA stiffness testing. Pain-free subjects reported no history of LBP requiring treatment, and obtained a score of 0 on the McGill Pain Questionnaire. METHODS: PA stiffness was measured in subjects with LBP when (a) they first presented with pain and (b) when pain had resolved by more than 80%. Pain-free subjects, matched with pain subjects on gender, age, vertebral level to be tested and time between tests, were also measured on two occasions, to control for the effects of repeated stiffness testing and the passing of time. RESULTS: In subjects with low back pain stiffness decreased by 1.21 N/mm between test 1 and test 2. A paired t test found a significant difference between the tests (t = 3.04, df = 24, p = .006). In subjects without pain, there was an increase in stiffness of 0.74 N/mm between test 1 and test 2; a paired t test found no significant difference between the tests (t = -1.673, df = 24, p = .107). CONCLUSIONS: Subjects with LBP showed increased PA stiffness compared with when they had little or no pain, whereas pain-free subjects showed unchanged PA stiffness over time.     

Localization of last-order premotor interneurons in the lumbar spinal cord of rats

There is strong evidence that neural circuits underlying certain rhythmic motor behaviors are located in the spinal cord. Such local central pattern generators are thought to coordinate the activity of motoneurons through specific sets of last-order premotor interneurons that establish monosynaptic contacts with motoneurons. After injections of biotinylated dextran amine into the lateral and medial motor columns as well as the ventrolateral white matter at the level of the upper and lower segments of the lumbar spinal cord, we intended to identify and localize retrogradely labelled spinal interneurons that can likely be regarded as last-order premotor interneurons in rats. Regardless of the location of the injection site, labelled interneurons were revealed in laminae V-VIII along a three- or four-segment-long section of the spinal gray matter. Although most of the stained cells were confined to laminae V-VIII in all cases, the distribution of neurons within the confines of this area varied according to the site of injection. After injections into the lateral motor column at the level of the L4-L5 segments, the labelled neurons were located almost exclusively in laminae V-VII ipsilateral to the injection site, and the perikarya were distributed throughout the entire mediolateral extent of this area. Interneurons projecting to the lateral motor column at the level of the L1-L2 segments were also located in laminae V-VII, but most of them were concentrated in the middle one-third or in the lateral half of this area. Following injections into the medial motor column at the level of the L1-L2 segments, the majority of labelled neurons were confined to the medial aspect of laminae V-VII and lamina VIII, and the proportion of neurons that were found contralateral to the injection site was strikingly higher than in the other experimental groups. The results suggest that the organization of last-order premotor interneurons projecting to motoneurons, which are located at different areas of the lateral and medial motor columns and innervate different muscle groups, may present distinct features in the rat spinal cord.     

Axial loading of the spine during CT and MR in patients with suspected lumbar spinal stenosis

PURPOSE: To evaluate the effect of compressive axial loading in imaging of the lumbar spine in patients with clinically suspected spinal stenosis. MATERIAL AND METHODS: A total of 84 patients were examined, 50 with CT (after intrathecal contrast administration) and 34 with MR. First the dural sac cross-sectional area (CSA) was determined with the patient in the supine psoas relaxed position (PRP). Then the CSA was determined during supine axial compression in slight extension (ACE), obtained with a specially designed loading device. A measurement error study was performed. RESULTS: A minimum difference in CSA of 15 mm2 between PRP and ACE was found to be significant. In 40/50 (80%) of CT-examined patients and in 26/34 (76%) of MR-examined patients a significant difference in CSA was found. In 25/84 (30%) of the patients there was a significant difference at more than one level. CONCLUSION: For an adequate evaluation of the CSA, CT or MR studies should be performed with axial loading in patients who have symptoms of lumbar spinal stenosis.     

The effects of immobilization of long segments of the spine on the adjacent and distal facet force and lumbosacral motion

Long levels of spinal instrumentation and fusion are common in surgery for spinal deformity. The effect on the remaining mobile segments is not well understood. The changes in lumbar facet loading and lumbosacral motion were evaluated as the number of immobilized levels increased. Four fresh canine cadaveric spines from T6 to sacrum were used. Lumbosacral motion was measured with an instrumented spatial linkage device, and facet loads were measured at L1, L4, and L7 using a strain gauge technique. Lumbosacral motion and facet loading were significantly increased (P < 0.05) after immobilization of proximal segments, and the amount of the increase was dependent on the number of immobilized segments (P < 0.05). This indicates that immobilization of long segments of the spine influences the remaining mobile segments by increasing the load and motion not only at the immediately adjacent segment but also at the distal segments.     

Dimensions of the lumbar spinal canal: variations and correlations with somatometric parameters using CT

The aim of this study was to investigate the correlation of vertebral dimensions with somatometric parameters in patients without clinical symptoms and radiological signs of central lumbar spinal stenosis. One hundred patients presenting with low back pain or sciatica were studied with CT. In each of the L3, L4 and L5 vertebra three slices were taken with the following measurements: 1. Slice through the intervertebral disc: (a) spinal canal area; (b) interarticular diameter; (c) interligamentous diameter. 2. Slice below the vertebral arcus: (a) dural sac area; (b) vertebral body area. 3. Pediculolaminar level: (a) anteroposterior diameter and interpedicular diameter of the spinal canal; (b) spinal canal area; (c) width of the lateral recesses. The Jones-Thomson index was also estimated. The results of the present study showed that there is a statistically significant correlation of height, weight and age with various vertebral indices. The conventional, widely accepted, anteroposterior diameter of 11.5 mm of the lumbar spinal canal is independent of somatometric parameters, and it is the only constant measurement for the estimation of lumbar spinal stenosis with a single value. The present study suggests that there are variations of the dimensions of the lumbar spinal canal and correlations with height, weight and age of the patient.     

Characterization of commissural interneurons in the lumbar region of the neonatal rat spinal cord

Neurons with axons that extend to the contralateral side of the spinal cord--commissural interneurons (CINs)--coordinate left/right alternation during locomotion. Little is known about the organization of CINs in the mammalian spinal cord. To determine the numbers, distribution, dendritic morphologies, axonal trajectories, and termination patterns of CINs located in the lumbar spinal cord of the neonatal rat, several different retrograde and anterograde axonal tracing paradigms were performed with fluorescent dextran amines and the lipophilic tracer 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI). CINs with ascending (aCINs) and descending (dCINs) axons were labeled independently. The aCINs and dCINs occupied different but overlapping domains within the transverse plane. The aCINs were clustered into four recognizable groups, and the dCINs were clustered into two recognizable groups. All dCINs and most aCINs were located within the gray matter, with somata ranging from 10-30 microm in diameter and with large, multipolar dendritic trees. One group of aCINs was located outside the gray matter along the dorsal and dorsolateral margin and had dendrites that were nearly confined to the dorsolateral surface. All CIN axons traversed the ventral commissure at right angles to the midline. CIN axons coursed up to six or seven segments rostrally and/or caudally in the ventral and ventrolateral white matter and gave off collaterals over a shorter range, predominantly to the ventral gray matter. These findings show that the lumbar spinal cord of the neonatal rat contains substantial numbers of CINs with axon projections and collateral ranges spanning several segments and that CINs projecting rostrally vs. caudally have different distributions in the transverse plane. The study provides an anatomical framework for future electrophysiological studies of the spinal neuronal circuits underlying locomotion in mammals.