RESUMO
Herniated disc (HD) is a common health problem that is resolved by surgery unless spontaneous resorption occurs. HD tissue contains abundant macrophage infiltration and high levels of matrix metalloproteinases (MMPs) MMP-3 and MMP-7. We developed a model system in which disc tissue or isolated chondrocytes from wild-type or MMP-null mice were cocultured with peritoneal macrophages and used this system to investigate the role of MMPs and chondrocyte/macrophage interactions in disc resorption. We observed a marked enhancement of MMP-3 protein and mRNA in chondrocytes after exposure to macrophages. Chondrocytic MMP-3, but not MMP-7, was required for disc resorption, as determined by assaying for a reduction in wet weight and proteoglycan content after 3 days of coculture. Surprisingly, chondrocyte MMP-3 was required for the generation of a macrophage chemoattractant and the subsequent infiltration of the disc tissue by proteolytically active macrophages. We conclude that macrophage induction of chondrocyte MMP-3 plays a major role in disc resorption by mechanisms that include the generation of a bioactive macrophage chemoattractant.
Assuntos
Deslocamento do Disco Intervertebral/enzimologia , Macrófagos Peritoneais/enzimologia , Metaloproteinase 3 da Matriz/metabolismo , Animais , Western Blotting , Inibição de Migração Celular , Condrócitos/citologia , Condrócitos/enzimologia , Técnicas de Cocultura , Meios de Cultivo Condicionados/farmacologia , Cultura em Câmaras de Difusão , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Disco Intervertebral/citologia , Disco Intervertebral/efeitos dos fármacos , Disco Intervertebral/enzimologia , Deslocamento do Disco Intervertebral/genética , Deslocamento do Disco Intervertebral/patologia , Macrófagos Peritoneais/citologia , Macrófagos Peritoneais/efeitos dos fármacos , Metaloproteinase 3 da Matriz/genética , Metaloproteinase 7 da Matriz/genética , Metaloproteinase 7 da Matriz/metabolismo , Camundongos , Camundongos Endogâmicos , Camundongos Knockout , Técnicas de Cultura de Órgãos , RNA Mensageiro/metabolismo , Ratos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Fator de Necrose Tumoral alfa/farmacologia , Regulação para CimaRESUMO
Herniated disc (HD), one of the major causes of low back pain, is often resolved spontaneously without surgical intervention. Resorption is associated with a marked increase in infiltrating macrophages, and the matrix metalloproteinases (MMP) MMP-3 and MMP-7 have been implicated in this phenomenon. We developed a murine organ culture model in which intact intervertebral discs were cocultured with peritoneal macrophages to investigate the role of MMPs in HD resorption. Using macrophages isolated from MMP-null mice, we report that macrophage-produced MMP-7 was required for proteoglycan degradation, loss of wet weight, and macrophage infiltration of cocultured discs. The inability of MMP-7-deficient macrophages to infiltrate discs could not be attributed to a defect in macrophage migration. MMP-7 was required for the release of the cytokine TNF-alpha from peritoneal macrophages. The generation of soluble TNF-alpha was essential for the induction of MMP-3 in disc cocultures, which in turn is required for the generation of a macrophage chemoattractant and subsequent macrophage infiltration. TNF-alpha release from macrophages was necessary but insufficient for disc resorption, which required macrophage infiltration. We conclude that there is extensive communication between macrophages and chondrocytes in HD resorption and that an essential component of this communication is the requirement for MMPs to release soluble bioactive factors.
Assuntos
Deslocamento do Disco Intervertebral/enzimologia , Metaloproteinase 7 da Matriz/metabolismo , Fator de Necrose Tumoral alfa/metabolismo , Animais , Reabsorção Óssea/enzimologia , Inibição de Migração Celular , Células Cultivadas , Técnicas de Cocultura , Cultura em Câmaras de Difusão , Modelos Animais de Doenças , Indução Enzimática , Disco Intervertebral/citologia , Disco Intervertebral/enzimologia , Deslocamento do Disco Intervertebral/genética , Deslocamento do Disco Intervertebral/patologia , Macrófagos Peritoneais/citologia , Macrófagos Peritoneais/efeitos dos fármacos , Macrófagos Peritoneais/enzimologia , Metaloproteinase 3 da Matriz/biossíntese , Camundongos , Camundongos Endogâmicos , Camundongos KnockoutRESUMO
A quantitative serial sectioning technique and a video-imaging procedure were used to obtain precise (20-microns voxels, in a 5 mm x 6 mm x 7 mm test volume) digital images of lumbar vertebral cancellous bone specimens. Conventional stereological image analyses were performed on this data to determine multiplanar (bulk) and surface planar variations in cancellous structural properties. Based upon an error analysis of subgroups of the complete serial planar images, our findings suggest that, for a plane resolution of 20 microns, sectioning at an increment < or = 100 microns along an axis is necessary to obtain accurate data of bulk structural properties of cancellous bone. Planar structural variations obtained from the serial sections of cancellous bone revealed a high degree of complexity and heterogeneity of the bone architecture. Bone area centers deviated from the section centroid and showed a helical variation along the primary or superior--inferior loading axis of samples. In comparison with the base planes (perpendicular to the superior-inferior axis), the lateral planes (parallel to the superior-inferior axis) of spine samples showed smaller mean values of structural indices and a more oriented structure. This structural anisotropy may be related to the functional mechanical anisotropy of the samples.
Assuntos
Vértebras Lombares/anatomia & histologia , Adulto , Fenômenos Biomecânicos , Humanos , Processamento de Imagem Assistida por Computador , Pessoa de Meia-Idade , Resistência à TraçãoRESUMO
The Young's modulus, bending strength, apparent density, and ash content of 155 human compact bone bending specimens were determined. Both Young's modulus (E) and bending strength (S) were strongly correlated to tissue dry apparent density (rho a). Based upon the correlation coefficient (R) and the percent deviation of the data from the regression curve (% dev.), these correlations were best described by power law relationships: E infinity rho a 1.54 (R2 = 0.79, % dev. = 2.4) and S infinity rho a 2.18 (R2 = 0.80, % dev. = 6.4). Bending strength was related to Young's modulus raised to the 1.26 power, implying a nonlinear relationship for these variables. We found a weak correlation between ash content and the mechanical behavior of the compact bone specimens, particularly Young's modulus, but could not statistically justify formulation of a more complex multivariate power model incorporating both density and ash content. Regional variations in strength and stiffness along the femoral shaft and within the cortex were also noted and were attributed primarily to differences in apparent density. The relationships formulated for the mechanical behavior of human compact bone are discussed in terms of the results of previous investigations of the mechanical behavior of nonhuman compact bone and human cancellous bone.
Assuntos
Osso e Ossos/fisiologia , Idoso , Fenômenos Biomecânicos , Densidade Óssea/fisiologia , Osso e Ossos/citologia , Feminino , Humanos , Masculino , Matemática , Pessoa de Meia-Idade , Modelos Biológicos , Análise Multivariada , Estatística como AssuntoRESUMO
The in vitro viscoelastic "creep" behavior was examined in 18 cadaveric human lumbar motion segments subjected to static axial compressive loads. Axial deformation was followed for 30 min under constant applied load. Compressive material constants (moduli and viscosity coefficients) were then determined for each intervertebral disc using a linearization method based on a Taylor series expansion of experimental data for the "three parameter" viscoelastic creep model. The degree of disc degeneration and bone mineral content (BMC) were also assessed. Good correlation between the experimentally determined and model predicted strain values were found, with the average error less than 1%. We found that motion segments from older and more degenerated lumbar discs were less stable and had lower material constants than segments from younger and less degenerated discs. Material constants and BMC correlated closely, suggesting that an interdependency of disc and vertebral body properties exists. No correlation between the creep characteristics and disc height, disc area, segment level, or sex were noted.
Assuntos
Disco Intervertebral/fisiologia , Vértebras Lombares/fisiologia , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Elasticidade , Feminino , Humanos , Técnicas In Vitro , Disco Intervertebral/patologia , Disco Intervertebral/fisiopatologia , Vértebras Lombares/fisiopatologia , Masculino , Pessoa de Meia-Idade , Modelos Biológicos , Movimento , Fatores Sexuais , Osteofitose Vertebral/fisiopatologia , Estresse Mecânico , ViscosidadeRESUMO
Seventeen cadaveric human lumbar motion segments from eight spines were cyclically loaded in vitro under axial compression. Loading frequency and magnitude were chosen to simulate rigorous activity within an in vivo physiological level. The load magnitude was determined as a percentage of the ultimate compressive load, the latter estimated from the bone mineral content (BMC) of lumbar vertebrae determined by dual-photon absorptiometry. Following testing, the degree of macroscopic disc degeneration was assessed and the type of fracture in each specimen was determined from serial sagittal sections. Fractures were found in all but one specimen. Three types of fractures were formed: the node of Schmorl and Junghanns (type I), central endplate fracture (type II), and a crush or burst fracture (type III). The results suggested that type I fractures were predominantly associated with segments with normal discs, type II fractures were found primarily in segments with moderately degenerated discs, and type III fractures were associated with segments that failed on the first cycle. Segment stiffness and fatigue strength (cycles to failure) were correlated with disc degeneration, age, and segment BMC, the latter an in vivo measure of bone density. Fatigue strength also decreased in proportion to a power coefficient with increasing relative stress (cyclic stress range/ultimate stress).
Assuntos
Disco Intervertebral/fisiologia , Vértebras Lombares/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Transtornos Traumáticos Cumulativos/fisiopatologia , Elasticidade , Feminino , Humanos , Técnicas In Vitro , Disco Intervertebral/fisiopatologia , Vértebras Lombares/análise , Vértebras Lombares/lesões , Vértebras Lombares/fisiopatologia , Masculino , Pessoa de Meia-Idade , Minerais/análise , Movimento , Estresse MecânicoRESUMO
Geometric, elastic, and structural properties of growing rat femora were determined from bending and torsion tests followed by bone sectioning and measurement of areal properties. Rosette strain gages bonded to the bone surface measured the strain during testing. A computer generated elliptical cross-sectional representation of the cross section geometry was used for calculation of material and structural properties. All structural and material properties increased with increasing age, exhibiting age-related changes that were best represented by an allometric or "heterauxic" growth pattern (y = axb) up to maturity. The femoral axial, flexural, and torsional rigidity increased 5.7, 10.1, and 14.8 fold, respectively, during maturation from 21 to 119 days of age. The increase in whole bone rigidity during maturation was caused primarily by changes in geometry. The bone tissue tensile longitudinal elastic modulus and shear modulus approximately doubled, and the shear strength increased approximately fourfold over this same period. Following maturity, a much slower increase in bending and torsional properties was noted. The results suggest that bone structural properties are regulated by changes in both geometric and material properties.
Assuntos
Fêmur/crescimento & desenvolvimento , Envelhecimento , Animais , Fenômenos Biomecânicos , Elasticidade , Fêmur/anatomia & histologia , Masculino , Matemática , Métodos , Ratos , Ratos Endogâmicos , Estresse MecânicoRESUMO
The use of an internal fixation plate in the presence of a bone defect was studied using a theoretical model of an idealized long bone having a circular cross section and loaded using a combination of axial and bending loads. The analysis showed that the "bending-open" loading mode does not occur if, in the normal unplated bone, the line of action of the resultant axial load passes within the outer cortex at the location where the plate is to be applied. In this situation the fracture will deform in a "bending-closed" mode regardless of whether the plate is attached to the tension or the compression side. If bony contact cannot be achieved, lower plate stress is always encountered when the plate is attached to the compression side instead of the tension side. In vivo verification of the model was addressed in a pilot experiment using instrumented metal plates applied bilaterally to the femora of one dog. Bilateral bone defects were created in the midfemoral canine diaphysis. On one leg the plate was applied to the lateral aspect ("tension" side), and on the other leg the plate was applied to the medial aspect ("compression" side). The plate attached to the lateral aspect deformed plastically in the bending-closed mode. The contralateral plate that was attached to the medial aspect (compression side) of the femur did not show signs of plastic deformation. Furthermore, the plate strains were lower in the plate attached to the medial aspect than those in the plate attached to the lateral aspect.(ABSTRACT TRUNCATED AT 250 WORDS)
Assuntos
Placas Ósseas , Fixação Interna de Fraturas , Animais , Fenômenos Biomecânicos , Cães , Fraturas do Fêmur/diagnóstico por imagem , Fraturas do Fêmur/etiologia , Fraturas do Fêmur/cirurgia , Matemática , Modelos Biológicos , RadiografiaRESUMO
In order to evaluate radiographic methods for diagnosing central lumbar stenosis, we reviewed the computed tomography scans and myelograms of twenty-four patients who underwent surgical decompression for central lumbar stenosis. In the diagnosis of central lumbar stenosis, the measurement of the anterior-posterior diameter of the osseous canal by computed tomography was less reliable than the measurement of the dural sac by myelography. The dimensions of the canal derived from computed tomography provided a correct diagnosis in 20 per cent of the patients, while myelography was accurate 83 per cent of the time. The effectiveness of computed tomography was improved when the cross-sectional area of the dural sac was measured. We suggest that a narrow dural sac, demonstrated by myelography or by computed tomography, reliably indicates central spinal stenosis.
Assuntos
Mielografia , Estenose Espinal/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Adulto , Idoso , Humanos , Metrizamida , Pessoa de Meia-Idade , Canal Medular/diagnóstico por imagemRESUMO
An objective evaluation for the assessment of patients who have persistent low-back pain and sciatica was tested in eighty-four patients who were operated on by one of us (D.M.S.). In this scoring system, there are four major categories for preoperative assessment: neurological signs, sciatic-tension signs, psychological factors, and imaging studies. When the preoperative scores of the eighty-four patients were correlated with the findings at operation, the three patients who had the lowest scores were the only ones in whom the operative findings were negative. As shown by statistical analysis, the score for imaging studies correlated best with the operative findings. In contrast, in the sixty-one patients who were followed sufficiently to determine the clinical outcome, the psychological score was the best predictor of the outcome of treatment. On the basis of these studies, we concluded that the use of this objective scoring system reduced the incidence of negative findings at exploration of the disc and improved the clinical result after elective discectomy. The higher the score was preoperatively, the more likely the patient was to have a good result after discectomy.
Assuntos
Deslocamento do Disco Intervertebral/cirurgia , Adolescente , Adulto , Idoso , Análise de Variância , Distribuição de Qui-Quadrado , Feminino , Humanos , Deslocamento do Disco Intervertebral/diagnóstico , Deslocamento do Disco Intervertebral/patologia , Vértebras Lombares/cirurgia , MMPI , Masculino , Pessoa de Meia-Idade , Mielografia , Exame Neurológico , Valor Preditivo dos Testes , Análise de Regressão , Ciática/fisiopatologia , Tomografia Computadorizada por Raios XRESUMO
In vivo beta-aminopropionitrile treatment caused significant changes in the mechanical properties of rat femora. In femora treated with beta-aminopropinitrile as compared with controls, there was a 44 per cent decrease in bone stiffness and a 47 per cent increase in bone deformation to failure. Bone ash was decreased 5 per cent in the treated group. It is likely that the decrease in bone ash was secondary to impaired intermolecular bone-collagen cross-linking, which is a well established consequence of treatment with beta-aminopropionitrile. Thus, beta-aminopropionitrile influences bone mechanical properties directly by impairing collagen cross-linking and indirectly by altering bone-matrix mineralization.
Assuntos
Aminopropionitrilo/farmacologia , Fenômenos Biomecânicos , Fêmur/efeitos dos fármacos , Animais , Matriz Óssea/efeitos dos fármacos , Cálcio/sangue , Masculino , Fósforo/sangue , RatosRESUMO
A technique for the fabrication of encapsulated micro-miniature rosette strain gages for in vivo implantation is described. The gage units have an overall area of ten square millimeters (2.5 mm X 4.0 mm), and hence can be installed in very small experimental animals, particularly rodents. Using a rat model, strain data for up to 12 days have been obtained and in vitro studies have validified the in vivo strain recordings.
Assuntos
Osso e Ossos/fisiologia , Eletrônica Médica/instrumentação , Marcha , Animais , Fenômenos Biomecânicos , Osso e Ossos/cirurgia , Masculino , Ratos , Ratos EndogâmicosRESUMO
Bone in vivo stresses and moments were determined from rosette strain recordings obtained from the mid-diaphysis of growing exercising rats. Two activity groups were examined beginning at 3 weeks of age: 2 min day-1 and 45 min day-1 at 0.2 ms-1 in an exercise wheel. In vitro moment-strain curves were obtained during mechanical calibration tests on intact femora, and area inertial properties were determined from the mid-diaphysis cross-sections. The mechanical calibration and histomorphometry procedures were then used to compute functional stresses and moments based on the in vivo rosette strain recordings. During the period 6-30 weeks of age the rats increased in body weight over threefold, but no significant changes in principal strain and stress magnitude or orientation were found. Peak in vivo compressive and tensile moments increased during growth in proportion to the animal mass squared, but the ratio of these moments to animal body weight times bone length (BWBL) remained constant throughout growth and in the adult. The parameter BWBL appears, therefore, to be a useful predictor of long bone functional strength. Peak torsional moments remained a constant 8.1 +/- 3.0% of the ultimate torsional strength, providing a safety factor of approximately 12. Differences in the in vivo moments between the two activity groups were found, which were due primarily to adaptive, but not significant, changes in bone geometry. These findings support the hypothesis that long bones model and model during growth and altered activity in order to regulate the functional strains at a predefined level.
Assuntos
Peso Corporal , Desenvolvimento Ósseo , Fêmur/fisiologia , Envelhecimento , Análise de Variância , Animais , Fenômenos Biomecânicos , Técnicas In Vitro , Masculino , Condicionamento Físico Animal , Ratos , Ratos Endogâmicos , Estresse Mecânico , Fatores de TempoRESUMO
The influence of load-bearing surface layers on Young's modulus was determined for cancellous bone and polyurethane foam specimens of three different heights cut from each material: 16, 9, and 5 mm for bone specimens (cross-sectional area A = 81 mm2) ranging in density from 0.04 to 0.32 g cm-3; 20, 10, and 5 mm for foam specimens (A = 100 mm2) ranging in density from 0.064 to 0.64 g cm-3. The compressive elastic modulus of the 5 mm bone specimens was significantly smaller (42%) than that of the 16 mm bone specimens. A similar change in elastic modulus was also observed for the foam specimens, but the height effect diminished in a relatively linear manner as the foam density increased. For a height change from 20 to 5 mm, the foam modulus difference ranged from a 41% decrease for the lowest density specimens (p = 0.064 g cm-3) to an insignificant change (< 1.8%) for the highest foam density specimens (p = 0.64 g cm-3). The specimen height effect on elastic modulus was hypothesized to result from a higher deformation (compliance) of the cellular materials in the load-bearing or contacting surface layer than in the bulk. A mathematical formula was derived to predict the variation in measured elastic modulus (E) caused by the contacting surface layer modulus (Ecs) to bulk modulus (Eb) ratio (Y = Ecs/Eb) and contacting surface layer height (hcs) to sample height (h) ratio (t = hcs/h): E/Eb = Y/[Y(1-t)+t]. Predicted differences in the measured modulus associated with graduated specimen heights were verified experimentally by regional strain measurements of the foam and bone samples using an optical microscope. The influence of free-surface layers was also determined for the foam specimens with cross-sectional areas 1.21 and 10 times the load-bearing area of a load platen, but the measured differences were small (< 10%) compared to that of the load-bearing surface layer influence. In future compressive mechanical testing of cellular materials, specimens < 10 mm in height should be avoided, particularly specimens with low bulk density or high porosity.
Assuntos
Vértebras Lombares/fisiologia , Poliuretanos/química , Adulto , Densidade Óssea , Elasticidade , Previsões , Humanos , Vértebras Lombares/anatomia & histologia , Pessoa de Meia-Idade , Modelos Biológicos , Porosidade , Estresse Mecânico , Propriedades de Superfície , Suporte de Carga/fisiologiaRESUMO
Histomorphometric and biomechanical changes in bone resulting from hypogravity (simulated weightlessness) were examined in this study. Using a head-down hindlimb suspension model, three groups of six male rats underwent simulated weightlessness for periods of one, two and three weeks while a fourth recovery group was suspended for two weeks followed by two weeks of normal activity. Biomechanical data were collected during static and dynamic bending and torsion tests on intact femora. Histomorphometric values were determined from midshaft bone cross sections and material properties were obtained using ash and calcium assays. The experimental groups exhibited significantly lower geometric and material properties than the controls, resulting in structural hypotrophy; geometric and material changes contributed equally to the structural changes. Recovery following a return to normal activity was indicated, although full recovery may take longer than the weightlessness period. In the rat, altered maturation and reduced bone strength were the sequelae of weightlessness.
Assuntos
Osso e Ossos/fisiopatologia , Ausência de Peso/efeitos adversos , Envelhecimento/fisiologia , Animais , Fenômenos Biomecânicos , Desenvolvimento Ósseo , Osso e Ossos/análise , Osso e Ossos/patologia , Cálcio/análise , Fêmur/análise , Fêmur/patologia , Fêmur/fisiopatologia , Masculino , Ratos , Ratos Endogâmicos , Anormalidade TorcionalRESUMO
A new technique incorporating a motion analysis system and a materials testing machine was used to investigate regional differences in the tensile mechanical properties of the lumbar spine anterior longitudinal ligament (ALL). Bone-ALL-bone specimens were prepared from young human cadaveric motion segments with no disc or bony pathology. Each specimen was distracted until failure at a constant crosshead displacement rate of 2.5 mm s-1 (approximately 1.0% strain per second). Strains were evaluated from digitized video recordings of markers attached to the ALL at 12 sites along its length and width, including the ligament substance and insertions. The 'overall' strain in the ligament was calculated from the outermost pairs of markers along the ligament length. The average tensile strength, the 'overall' tensile modulus and the 'overall' strain of the ALL at failure were 27.4 MPa (S.D. 5.9), 759 MPa (S.D. 336) and 4.95% (S.D. 1.51), respectively. Large and significant variations in the strains were present along the width and length of the ALL. Peak substance strains were over twofold greater than peak strains at the ligament insertion sites, whereas across the ligament width, peak strains in the outer portion of the ligament were over 40% greater than in the central region. Failure consistently occurred in the ligament mid-substance and ultimate strains at the ligament failure site averaged 12.1% (S.D. 2.3). These results indicate that the strains are highly nonuniform in the normal ALL.
Assuntos
Ligamentos/fisiologia , Vértebras Lombares/fisiologia , Adulto , Humanos , Masculino , Estresse Mecânico , Resistência à Tração/fisiologiaRESUMO
Strain-controlled uniaxial fatigue and monotonic tensile tests were conducted on turned femoral cortical bone specimens obtained from baboons at various ages of maturity. Fatigue loading produced a progressive loss in stiffness and an increase in hysteresis prior to failure, indicating that immature primate cortical bone responds to repeated loading in a fashion similar to that previously observed for adult human cortical bone. Bone fatigue resistance under this strain controlled testing decreased during maturation. Maturation was also associated with an increase in bone dry density, ash fraction and elastic modulus. The higher elastic modulus of more mature bone meant that these specimens were subjected to higher stress levels during testing than more immature bone specimens. Anatomical regions along the femoral shaft exhibited differences in strength and fatigue resistance.
Assuntos
Desenvolvimento Ósseo , Osso e Ossos/fisiologia , Animais , Fenômenos Biomecânicos , Feminino , Técnicas In Vitro , Masculino , Papio , Resistência à TraçãoRESUMO
Fifty-four consecutive patients who underwent limited lumbar discectomy, based on specific objective criteria, were reviewed. Sixteen of these patients had a limited foraminotomy performed in addition to the limited discectomy. The postoperative results in these patients were good, and the fair to poor results appear to be related primarily to subjective factors, rather than to persistent objective impairment of neuromuscular function. These data do not support prior concern over an increased incidence of recurrent disc herniation with a limited discectomy. Lumbar discectomy performed with limited disc excision is a safe, effective, and reliable method for treating selected patients with herniated lumbar discs.
Assuntos
Deslocamento do Disco Intervertebral/cirurgia , Estudos de Avaliação como Assunto , Humanos , Vértebras Lombares , Métodos , Complicações Pós-OperatóriasRESUMO
A reproducible method is presented for selecting patients with low-back pain and sciatica for lumbar discectomy based on specific objective criteria in four categories: neurologic signs, sciatic tension signs, personality factors (MMPI scores), and lumbar myelography. Operative findings for 50 consecutive cases selected using this method revealed complete nucleus pulposus herniation in 43 cases. This contrasts with complete herniation in only 5 of 26 patients undergoing lumbar discectomy before the method was employed. This objective preoperative evaluation method reduced negative disc explorations and improved early surgical results. We recommend its use for patients being considered for elective lumbar discectomy.
Assuntos
Deslocamento do Disco Intervertebral/cirurgia , Adolescente , Adulto , Feminino , Humanos , Deslocamento do Disco Intervertebral/diagnóstico , Vértebras Lombares , MMPI , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Estudos Retrospectivos , Ciática/psicologia , Ciática/cirurgiaRESUMO
In order to register pressure changes within the cauda equina, a highly sensitive pressure measuring catheter was inserted through a hole in the dural sac. Its tip was placed among the nerve roots of the cauda equina at levels L2, L3, and L4 in seven freshly removed human specimens. The cross-sectional area of the dural sac then was decreased gradually by constriction of a circular clamp. The inside diameter of the clamp and the corresponding area was determined when further reduction of the circumference of the clamp caused the first signs of a pressure increase, the critical size, among the nerve roots. The average critical size was 76.9 mm2 at the L2 level, corresponding to a diameter of 11.4 mm At the L3 level, the corresponding figures were 71.5 mm2 and 11.1 mm, and at the L4 level 64.8 mm2 and 10.6 mm, respectively. It seemed reasonable to assume that the critical sizes determined in this way could be threshold values below which a further constriction of the size of the dural sac would cause an impairment of the circulatory and/or the nerve function of the cauda equina.