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PubMed1983

[Experimental study on the post-laminectomy deterioration in cervical spondylotic myelopathy--influences of the meningeal treatment and persistent spinal cord block].

Free, rhythmical movement of cerebrospinal fluid (CSF) is regarded as the inhibitory factor of subarachnoidal adhesion. When the block of CSF flow remains after the laminectomy for cervical spondylotic myelopathy, danger of postoperative subarachnoidal adhesion and ensuing deterioration of operative results is present. Such risk may increase when the meningeal treatment is combined with the laminectomy. The experimental study was practiced on dogs to confirm the surmise mentioned above. First, the gradual anterior cord compression was made at the C4 and C6 levels to produce multiple block of CSF flow. Then, 3 types of posterior surgical decompression, i.e. simple laminectomy, dura mater resection, and arachnoid resection were performed at the C6 level. The fourth type of posterior decompression was also performed, that is, the arachnoid resection at the C6 level accompanied with simple laminectomy up to the level of C4 in order to know the influence of the improvement of CSF passage. Dogs were classified into 4 groups according to the type of the posterior surgery and sacrificed after a certain period to examine the changes around the spinal cord mainly at the C6 level. The results and conclusions are as follows. In the presence of anterior spinal cord compression and CSF flow disturbance, the cord was compressed again by the laminectomy membrane when the dura mater was resected and not compressed when it was preserved. And when the arachnoid was also resected, the scar tissue adhered to the dorsal aspect of the cord and tightly compressed it. The improved CSF passage diminished the extent of subarachnoidal adhesion and the degree of cord compression. From these results, it may be concluded that the laminectomy for the cervical myelopathy should be done sufficiently so as to improve the CSF passage, and at the same time, the meningeal treatment should be avoided as long as possible.

Animals↗
PubMed1995

Laminectomy-induced arachnoradiculitis: a postoperative serial MRI study.

Time-related changes of laminectomy-induced cauda equina adhesions were investigated by MRI in ten patients with degenerative spinal disease who underwent posterior surgery to the lumbar spine; seven had disc herniations and three spinal stenosis. Axial MRI was performed before and 3, 7, 21 and 42 days after surgery. Cauda equina adhesions were most severe at the laminectomised levels L3-4, L4-5 and L5-S1 (n = 16); partial adhesions were found in 9 of 16 levels at 6 weeks after surgery. At the L3-4 or L5-S1 levels (n = 14), the area of laminar exposure without laminectomy, the cauda equina adhesions continued 1 week after surgery, but thereafter resolved; only partial adhesions were seen at 5 of 14 levels 6 weeks after surgery. Shrinkage of the arachnoid sac was also found at the level of the laminectomy, but it re-expanded 3 weeks after surgery in all cases. Cauda equina adhesions and shrinkage of the sac were correlated closely with laminectomy, with or without discectomy, suggesting that an inflammatory process of deep wound healing may be involved in the mechanism of a laminectomy-induced arachnoradiculitis which may be correlated with post-operative leg symptoms.

Adolescent↗
PubMed1991

A carbohydrate polymer that effectively prevents epidural fibrosis at laminectomy sites in the rat.

We demonstrate that a carbohydrate polymer, designated GL402, effectively inhibits epidural fibrosis in a rat laminectomy model. A total laminectomy in Lewis rats was performed at lumbar vertebrae 3 and 5. GL402 or phosphate buffer solutions in gelatin sponges were applied to the laminectomy sites. Epidural fibrosis was measured, using a double-blind protocol, 2 weeks postoperatively either by gross anatomical evaluation (blunt dissection) or by histological evaluation. Local application of GL402 produced nearly complete inhibition of epidural fibrosis, whereas extensive scar formation and bone growth occurred after local application of buffer or other purported anti-fibrotics. In laminectomy sites treated with GL402 the dura mater was essentially free of adhering fibrosis and bone growth was dramatically decreased. With reduction of postlaminectomy fibrosis, the spinal nerve roots are more mobile and therefore may be less prone to recurrent nerve root compression. The dramatic reduction of epidural fibrosis by GL402 will make reoperative disc surgery safer due to greater accessibility of the laminectomy site. This compound may be useful in preventing surgical adhesions in other sites as well.

Animals↗
PubMed2006

Short Form-36 outcomes following focal 1- and 2-level cervical laminectomy with multilevel instrumented fusion.

BACKGROUND: Multilevel laminectomy with instrumented fusion addresses diffuse dorsal cord compression with an adequately preserved cervical lordosis. However, for patients with only 1 to 2 laminar impingement, more "focal" laminectomy and fusion may suffice, the shortened laminectomy allowing for a more simple spinous process fusion skipping the 1 or 2 lamina that have been removed. METHODS: Fourteen patients presented with severe spastic myeloradiculopathy (Nurick grade IV) attributed to magnetic resonance imaging- and CT-documented 1- to 2-level laminar compression, stenosis, and ossification of the yellow ligament. Magnetic resonance images also revealed 1- to 2-level hyperintense signals within the cord at the levels of maximal compromise. Surgical procedures included 1- to 2-level laminectomies and average 6.4-level posterior fusions. Dynamic x-ray/CT studies, which were obtained 3, 6, and up to 12 months postoperatively, followed progression toward fusion. Outcomes were assessed using Nurick grades (0-V) and SF-36 questionnaires assessed preoperatively and up to 12 months postoperatively. RESULTS: Patients improved on all 8 SF-36 Health Scales within the first postoperative year. Maximal improvement was observed on 5 Health Scales within the first 6 postoperative months (physical function, mental health, vitality, general health, role physical). The preoperative average Nurick grade (3.8) improved postoperatively (0.7 at 6 months, 0.5 at 1 year). Dynamic x-ray and CT studies documented fusion for all 14 patients by the sixth postoperative month. CONCLUSIONS: One- and two-level cervical laminectomies with multilevel-instrumented fusion effectively decompressed "focal" cord compression, whereas fusion maintained the cervical lordotic curvature and provided stability to avert future disease progression.

Adult↗
PubMed2004

Epidural hematoma of the cervical spine after cervical laminectomy in a patient with ventriculo-peritoneal shunt.

Cervical laminectomy is one of the most common procedures performed in the sitting position. However in the presence of intracranial hypotension, a negative intradural pressure develops when the patients are in the sitting position. They are therefore at risk of developing cervical spinal epidural hematomas after cervical laminectomy. We report a case of a shunted patient who developed an epidural hematoma 3 days after a cervical laminectomy procedure in a seated position when he began to ambulate. When performing a cervical laminectomy procedure on a shunted patient, an upright position should be avoided during the operation. Intra-operative hypercapnia as well as intra- and post-operative intravenous hydration should be maintained in order to increase intradural pressure, preventing the formation of cervical spinal epidural hematoma after cervical laminectomy.

Hematoma, Epidural, Spinal↗
PubMedDate not supplied

[Experimental study of laminectomy of the cervical spine].

The influence of laminectomy on the statics of the cervical spine was experimentally investigated. Pressure tests were carried out with isolated supravital cervical vertebrae with and without intact vertebral arches. Changes occurring during the pressure test were registered by stretching measurement strips. We tried to determine the relation between the height of laminectomy and the dorsal forces being necessary for the maintenance of lordosis in another series of experiments. The experiments were taken with a model developed by ourselves. Following results were reached: The vertebral arch is involved in the interception of axial forces. It shores up the back bird of the vertebral body. This is only visible with reaching the breaking load. A dorsal flexion wedge tilting over in the spinal canal breaks off at vertebrae without intact vertebral arch. After a laminectomy the lordosis of the cervical spine can only be kept up by the increase of dorsal forces. The necessary increase of forces is biggest with the laminectomy of the second and fifth vertebra. A motion-study shows that there occurs a buckling in the area of laminectomy during flexion.

Adult↗
PubMed2000

Familial incidence of intervertebral disc herniation: an hypothesis suggesting that laminectomy and discectomy may be counterproductive.

OBJECTIVE: To determine (1) if familial and genetic factors play a role in the genesis of disc herniation, (2) the incidence of multiple disc herniations, (3) the incidence of disc reherniation in patients treated with standard laminectomy and discectomy, and (4) to construct a hypothesis that best explains all three. SUMMARY BACKGROUND DATA: It is known that there is a substantial incidence of disc herniation in first order relatives of patients with herniated nucleus pulposa (HNP), that multiple disc herniations are not uncommon, and that disc reherniations and repeat operations after laminectomy and discectomy range from 5 to 37%. Also, there is a recent report of a genetic defect leading to defective cross-linkage of collagen strands in patients with HNP. METHODS: Using the questionnaire method, a group of the author's patients with documented HNP treated with percutaneous laser disc decompression (PLDD) was surveyed as to the existence of known disc herniations among first order relatives. Analysis of the author's series of 621 patients with HNP disclosed the incidence of multiple disc herniations. A comprehensive literature search provided data on reherniations and reoperations following laminectomy and discectomy. RESULTS: In 174 respondents, the number with first order relatives who had HNP was 74 (or 43%). This compares with the national incidence of HNP of 1.7%. The statistical significance yields a P = 0.0001. In the 621 patients with known HNP, the number who had more than one herniated disc was 236 (or 38%). In multiple reports in the literature, the incidence of reherniation after laminectomy and discectomy ranged from 5 to 37%. CONCLUSIONS: The simplest hypothesis explaining all of the above is that intervertebral disc herniation is due to an acute or subacute increase of intradiscal pressure acting against a congenitally weak anulus fibrosus and posterior longitudinal ligament, and therefore laminectomy and discectomy, by further weakening these structures, may be counterproductive.

Collagen↗
PubMed1995

The significance of dorsal migration of the cord after extensive cervical laminectomy for patients with traumatic central cord syndrome.

Central cord syndrome (CCS) resulting from traumatic cervical injury is often associated with cervical stenosis and/or spondylosis. The efficacy of multilevel laminectomy in the treatment of this condition has been controversial. The objective of this study was to validate by magnetic resonance (MR) imaging the occurrence of dorsal cord migration after extensive laminectomy for patients with the clinical syndrome of central cord damage and its relationship to the short-term outcome. During a 28-month period, the authors evaluated 20 patients (mean age 54 years) who sustained CCS after cervical spine trauma. Pre- and postoperative MR imaging assessed the adequacy of cervical cord decompression by multilevel laminectomy. All patients had cervical canal stenosis with complete obliteration of the anterior subarachnoid space over multiple levels. Seventeen patients initially had CCS of different degrees of severity. One had no motor deficit and two had motor complete with sensory deficits greater in their arms. Laminectomy, generally from C2 to C7 without facetectomy, was performed after plateau of neurological recovery (mean 17 days postinjury). Neurological assessment 3 months after operation revealed improvement in 12, stable function in 7, and progression of deficit in one with no mortality. The postoperative midsagittal MR images demonstrated adequate decompression with restoration of anterior cerebrospinal fluid space and posterior cord migration in 12 patients (60% of the 20), but only 8 of them also had improved function. MR imaging demonstrated that, in the presence of multilevel spondylosis/stenosis, laminectomy may provide adequate spinal cord decompression in patients with traumatic CCS.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1997

Quantitative outcome and radiographic comparisons between laminectomy and laminotomy in the treatment of acquired lumbar stenosis.

OBJECTIVE: The objective of this study was to conduct a comparative quantitative analysis of outcomes, radiographic findings, and magnetic resonance imaging results after laminectomy or laminotomy was performed for patients with lumbar stenosis. Such as analysis had not previously been conducted. METHODS: Twenty-six patients with no exclusion criteria who were treated surgically for acquired stenosis at the Division of Neurological Surgery at The Ohio State University from 1990 to 1993 were studied retrospectively. At follow-up examinations, each patient completed a detailed questionnaire that included visual analog scales, functional assessments, and the medical outcome study short form health survey, SF-36. Each patient underwent plain static and dynamic radiography that detailed vertebral body sagittal listhesis and rotation and magnetic resonance imaging that evaluated dural sac compression. RESULTS: The mean follow-up duration was 36.7 months. Good outcome was defined by the presence of three criteria: no greater than mild leg pain (Grades 0-4), the ability to walk more than one block without developing lower extremity pain, and the ability to walk without assistance devices. Fifty-eight percent of the patients who had undergone laminectomies and 50% of the patients who had undergone laminotomies had good outcomes. All were judged to have had adequate decompression. The average maximum postoperative listhesis was 17.3 +/- 9.9% in the laminectomy group and 17.6 +/- 12.5% in the laminotomy group. In contrast to some previous studies, pre- or postoperative listhesis was not statistically related to outcome in either group. Patients in each poor outcome category seemed to have worse comorbid medical conditions than did patients in the good outcome category. The SF-36 measurements of poor functioning because of health factors and bodily pain correlated somewhat with poor outcomes in the patients who had undergone laminectomies. In patients who had undergone laminotomies, the only statistically significant finding among the outcome groups was the effect of poor emotional health on activity for the patients with poor outcomes. CONCLUSION: This study indicates that laminotomy can adequately decompress lumbar canal stenosis, that laminectomy and laminotomy have the same degree of postoperative listhesis, and that the quantitative outcome of any treatment for lumbar stenosis is dependent not only on surgical factors but also on comorbid physical and psychological factors.

Adult↗
PubMed1985

Cost effectiveness of chemonucleolysis versus laminectomy in the treatment of herniated nucleus pulposus.

The hospital and professional charges for 40 consecutive patients who underwent chymopapain chemonucleolysis in 1982-83 at the University of Wisconsin for single-level lumbar disc disease were compared with the charges incurred by 40 consecutive patients who underwent lumbar laminectomy for single-level disc disease during the same period. The average cost per patient was $4,163 for chemonucleolysis and $6,124 for laminectomy. Three chemonucleolysis patients reported poor results, and all subsequently underwent reoperation by laminectomy. Four laminectomy patients reported poor results, and two of these subsequently underwent reoperation. The costs of chemonucleolysis and lumbar laminectomy were calculated to reflect reoperation costs, and we found that the average cost per patient was $1,808 less for chemonucleolysis. The implications of this saving for national cost containment of lumbar disc surgery are discussed.

Adult↗
PubMed1987

The biomechanics of decompressive laminectomy.

The biomechanical effect of laminectomy as a means of relieving compression of the spinal cord-meningeal complex by an anterior mass was studied in ten grossly normal human cadaver spines. The basic experimental set-up involved drilling a sagittal plane hole transversely across a vertebral body to provide direct access to the anterior aspect of the neural canal. After securing a probe and linearly variable differential transformer (LVDT) assembly at each site to be tested, the probe was gently pushed into the neural canal; contact force against the tip of the probe as well as the depth of probe penetration was measured and recorded. Laminectomy did not alter the resulting contact force/anterior penetration plots at the fifth cervical, seventh thoracic, 12th thoracic, or third lumbar vertebra. Using the probe/LVDT assembly to measure anterior dural displacement and a cantilever displacement device to measure posterior dural displacement after laminectomy at the 12th thoracic vertebra, the authors found that although the anterior dura underwent gross displacement as the probe was pushed into the neural canal, the posterior dura displaced to a minimal degree. The extent of the laminectomy was not a factor. The study did not demonstrate any possible mechanism by which laminectomy could reduce the pressure exerted on the dura and neural elements by an anterior mass in a spine with otherwise normal neural canal dimensions.

Biomechanical Phenomena↗
PubMed1993

A biomechanical comparison of cervical laminaplasty and cervical laminectomy with progressive facetectomy.

The effects of multilevel cervical laminaplasty and laminectomy with increasing amounts of facetectomy on stability of the cervical spine were tested with physiologic loading in nine cadaveric specimens. Cervical spines, levels C2-C7, were tested with physiologic loading in a constraint-free test system, the motion of each body being tracked in a three-dimensional coordinate system. Cervical laminectomy with 25% or more facetectomy resulted in a highly significant increase in cervical motion compared to the intact specimens for the dominant motions of flexion/extension (P < 0.003), axial torsion (P < 0.001), and lateral bending (P < 0.001). Cervical laminaplasty was not significantly different from the intact control, except for a marginal increase in axial torsion. Coupled motion did not change with laminaplasty or laminectomy with progressive facetectomy. As little as 25% facetectomy adversely affects stability after multilevel cervical laminectomy. Cervical laminaplasty avoids this problem, while still affording multilevel decompression. Therefore in patients undergoing cervical laminectomy accompanied by more than 25% bilateral facetectomy, concurrent arthrodesis should be performed.

Absorptiometry, Photon↗
PubMed1999

Safety of recombinant human bone morphogenetic protein-2 after spinal laminectomy in the dog.

STUDY DESIGN: This was a randomized, blinded trial of the safety of the application of recombinant human bone morphogenetic protein (rhBMP)-2 or autologous bone graft onto a laminectomy defect of the dog in the presence or absence of a dural membrane puncture. OBJECTIVE: To test the safety of rhBMP-2 in an application in which direct contact of the material with neural tissue occurs. SUMMARY OF BACKGROUND DATA: Application of rhBMP-2 in laboratory animals stimulates local bone formation to effect spinal fusion and healing of segmental bone defects. The use of rhBMP-2 as a bone graft substitute in spinal fusion would eliminate donor site morbidity and may augment the rate of successful fusion. Because rhBMP-2 may unintentionally come in contact with neural tissue, the consequences of such a safety issue must be addressed in an animal model before human trials. METHODS: Twenty skeletally mature beagles underwent spinal exposure followed by bilateral laminectomy at L5. In half of the dogs, a puncture wound was made to the dura with the expression of cerebrospinal fluid at the site of the puncture. In randomly selected animals, the exposed dural elements received either autologous bone graft with the bone removed from the laminectomy site or an implant of the rhBMP-2 device. The animals was observed for 12 weeks with periodic clinical examinations and monthly computed tomographic scans. RESULTS: There was no clinical, radiographic, or histologic evidence of neurologic abnormalities in these animals. The rhBMP-2 stimulated bone growth in the laminectomy defect and came into direct contact with the dural membrane. There was no evidence of abnormal mineralization within the thecal sac or in the spinal cord itself. CONCLUSIONS: The rhBMP-2 implant stimulated bone formation in the laminectomy site. Neither autologous bone, rhBMP-2, nor the dural puncture had deleterious consequences for the animals.

Administration, Topical↗
PubMed1999

Posterolateral lumbar intertransverse process spine arthrodesis with recombinant human bone morphogenetic protein 2/hydroxyapatite-tricalcium phosphate after laminectomy in the nonhuman primate.

STUDY DESIGN: A nonhuman primate lumbar intertransverse process arthrodesis model was used to evaluate recombinant human bone morphogenetic protein 2 (rhBMP-2) in a hydroxyapatite-tricalcium phosphate (HA-TCP) carrier as a complete bone graft substitute. OBJECTIVES: To assess the ability of a ceramic material to serve as a carrier for various doses of rhBMP-2 as a bone graft substitute in a primate model of posterolateral intertransverse process spinal fusion after laminectomy. SUMMARY OF BACKGROUND DATA: The reported non-union rates for posterolateral lumbar spine fusion with autogenous iliac crest bone range from 5-35%. Recombinant human bone morphogenetic protein 2 has shown potential to serve as a bone graft substitute for posterolateral intertransverse process spine fusion. Although a resorbable collagen sponge was a suitable carrier in rabbits and dogs, it was too compressible for the paraspinal muscles in rhesus monkeys. This failure of the collagen carrier has prompted evaluation of the feasibility of an alternative carrier material and the required dose of rhBMP-2. METHODS: Twenty-one adult rhesus monkeys underwent a laminectomy at L4-L5 followed by bilateral intertransverse process arthrodesis via the same midline incision (n = 16) or a minimally invasive video-assisted posterolateral approach (n = 5). Bone graft implants on each side consisted of either 5 cm3 of autogenous iliac crest bone or 60:40 HA-TCP blocks (1.2 x 0.5 x 3.7 cm) loaded with a solution containing 0, 6, 9, or 12 mg of rhBMP-2 per side. The monkeys were killed 24 weeks after surgery. Inspection, manual palpation, radiography, and histology were used to assess fusion and to detect any bony growth into the laminectomy defect. RESULTS: Fusion was not achieved in any of the monkeys treated with autogenous iliac crest bone graft. Both of the monkeys treated with the HA-TCP blocks with 0 mg rhBMP-2 achieved fusion. All 15 monkeys treated with the HA-TCP blocks and either of the three doses of rhBMP-2 achieved solid fusion. Two animals had extension of the fusion on one side because of malpositioned ceramic block. The results in animals fused via the minimally invasive video-assisted technique were the same as inthose fused with the open technique. Histologic analysis showed some ingrowth of bone into the ends but not-through the ceramic block in the absence of rhBMP-2. When the ceramic blocks were loaded with rhBMP-2 there was a dose-dependent increase in the amount and quality of bone throughout the ceramic carrier based on qualitative assessment. No significant bone encroachment on the exposed thecal sac through the laminectomy defect was observed in any of the monkeys. CONCLUSION: Hydroxyapatite-tricalcium phosphate proved to be a suitable carrier for rhBMP-2 in the posterolateral spine fusion model in rhesus monkeys. Even in the presence of a laminectomy defect, there was no evidence of bone induction outside the confines of the ceramic carrier.

Animals↗
PubMed2004

Lumbar laminectomy for the resection of synovial cysts and coexisting lumbar spinal stenosis or degenerative spondylolisthesis: an outcome study.

STUDY DESIGN: Surgeon- and patient-based (SF-36) outcome measures were used to assess the results of decompressive laminectomies for the excision of synovial cysts with coexistent lumbar spinal stenosis (45 patients) or for synovial cysts with coexistent lumbar stenosis and degenerative spondylolisthesis (35 patients). OBJECTIVES: To evaluate the results following laminectomy and the excision of synovial cysts/stenosis with or without olisthy. SUMMARY OF BACKGROUND DATA: SF-36 outcome studies evaluating these surgical results deserve further investigation. METHODS: Before surgery, patients with synovial cysts/ stenosis (45 patients) or cysts/stenosis/degenerative spondylolisthesis (35 patients), respectively, exhibited low back pain (40 and 33 patients), radiculopathy (43 and 33 patients), and neurogenic claudication (41 and 26 patients). Surgery required average 3.8 and 3.5 level laminectomies, respectively, for patients with cysts/stenosis and cysts/stenosis and olisthy. Outcomes were assessed 2 years after surgery. RESULTS: Five of 45 patients undergoing laminectomy alone for cysts/stenosis developed postoperative olisthy. Of 35 patients with cysts/stenosis and preoperative Grade 1 degenerative spondylolisthesis, olisthy increased after surgery to Grade 2 in 11 patients. Good/excellent results (58% and 63%) and SF-36 improvement on the Physical Function Scale (+44 and +38 points) were, respectively, documented for these two groups. CONCLUSIONS: Using both surgeon and SF-36 outcome measures, 2 years following laminectomy for synovial cysts/lumbar stenosis with or without olisthy, patients exhibited a moderate degree of improvement. As synovial cysts reflect disruption of the facet joint and some degree of instability, primary fusion should be considered to improve operative results for patients in both categories.

Aged↗
PubMed2004

Biomechanical effects of C2-C7 intersegmental stability due to laminectomy with unilateral and bilateral facetectomy.

STUDY DESIGN: The biomechanical responses resulting from laminectomy with graded unilateral and bilateral facetectomy were quantified using a three-dimensional nonlinear finite element model of the C2-C7 motion segments. OBJECTIVE: To study the influence of laminectomy with graded unilateral and bilateral facetectomy on the cervical spinal biomechanics. SUMMARY OF BACKGROUND DATA: Cervical spinal stenosis is a condition that is caused by the narrowing of the spinal canal. Laminectomy and facetectomy are commonly used surgical procedures for decompressing cervical spinal stenosis. Resection of the posterior structures causes instability and affects the internal stresses of the cervical spinal components. However, the influence of these surgical procedures on the biomechanical responses of the cervical spine has not been studied. METHODS: A nonlinear finite element model of the intact C2-C7 was constructed and validated. Ten surgically altered models were created from the intact model and were tested under physiologic loading. Because of the inclusion of five motion segments, it was possible to determine the intersegmental responses and internal cortical shell and disc stresses in the adjacent altered and unaltered spinal components. RESULTS: Under combined flexion and extension, intersegmental motions at C4-C5 and C5-C6 increased significantly after C5 laminectomy. Subsequent facetectomy performed at C5 and C6 on the laminectomized model only affected the responses at the C5-C6 segment. Overall, slight intersegmental responses of up to 5% were observed at the adjacent levels of C3-C4 and C6-C7. Laminectomy did not cause any significant increase in the intersegmental motions under lateral bending and axial rotation. Extending the surgical procedures to unilateral and bilateral facetectomy only increased the intersegmental motions slightly. Similar increases in the intervertebral disc and the cortical shell stresses were observed. These findings may partially explain the clinical observations of enhanced osteophytes formation. CONCLUSIONS: This study provides a better understanding of the surgically altered cervical spinal biomechanics and may help formulate treatment strategies such as spinal implants.

Biomechanical Phenomena↗
PubMed1995

Comparison of hemilaminectomy and dorsal laminectomy for thoracolumbar intervertebral disc extrusion in dachshunds.

Neurological improvement after decompressive surgery, without routine therapeutic or prophylactic disc fenestration, was evaluated retrospectively in a consecutive series of 93 dachshunds with thoracolumbar disc extrusion. In 24 per cent of procedures, deep pain sensation was not elicited in at least one hind paw before surgery. Median neurological status one to seven days after surgery, at the time of discharge, was significantly improved after hemilaminectomy compared with dorsal laminectomy (P < 0.05). After hemilaminectomy, deep pain sensation was not elicited in one or both hind paws of 8 per cent of dogs in which pain sensation was elicited before surgery, compared with 21 per cent after dorsal laminectomy (P > 0.05). Improvement in neurological grade at follow-up examination two to 12 weeks after hemilaminectomy was not significantly different compared with dorsal laminectomy (P > 0.05). Of dogs which were unable to walk before surgery, 83 per cent regained the ability to walk after hemilaminectomy, compared with 74 per cent after dorsal laminectomy (P > 0.05). In both groups, 50 per cent of dogs in which deep pain sensation was abnormal before surgery eventually regained the ability to walk after surgery (P = 1). One to two years after the first operation, a second laminectomy was performed in only 5 per cent of dogs because of extrusion of a different intervertebral disc which had not been fenestrated.

Animals↗
PubMed1981

Pathogenesis and prophylaxis of postlaminectomy deformity of the spine after multiple level laminectomy: difference between children and adults.

The pathogenesis of postlaminectomy spinal deformity and instability in children was evaluated by reviewing appropriate roentgenographic findings. First, we reviewed spine roentgenograms of patients below 40 years of age who underwent spinal fusion for deformity and instability of the spine developing after a multiple level laminectomy. Two types of deformity were recognized on the roentgenograms: increased mobility between the vertebral bodies and wedging deformity of the ventral aspect of the vertebral bodies. Second, we did a follow-up study of another group of patients who had undergone laminectomy. We found the same two types of deformity in children, but not in adult patients. The incidence of deformity was higher after laminectomies of the cervical or cervicothoracic region than after lumbar laminectomies. Our data suggest that postlaminectomy spinal deformity can develop in children without irradiation or facet injury. The deformity is due to a wedging change in the cartilaginous portion of the vertebral body and to the viscoelasticity of ligaments in children. When treatment of this complication becomes necessary, anterior fusion may be effective in arresting progression. Prophylactic measures against the development of deformity are discussed. Our hypothesis concerning the mechanism of development of this complication supports the rationale of osteoplastic laminar resection and reconstruction instead of laminectomy, particularly in the management of children.

Adolescent↗