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Biomedical subjects

D M Spengler

Publications and source records attributed to D M Spengler.

At least 37 records · Page 2Linked to original sources
PubMed1993

Biomechanical analysis of three surgical approaches for lumbar burst fractures using short-segment instrumentation.

Burst fractures of the lumbar spine that are located below the thoracolumbar junction present a challenge when operative management is indicated. Short-segment instrumentation offers the advantage of incorporating fewer motion segments in the fusion, but may not provide adequate long-term stabilization. The goal of this study was to assess the axial stiffness and torsional rigidity of several short-segment instrumentation procedures. Compressive axial stiffness and torsional rigidity were measured in six intact porcine lumbar spines (L1-L5). A corpectomy was performed to simulate a burst fracture injury and decompression. Posterior instrumentation, posterior instrumentation with an anterior strut (a wood block), and anterior instrumentation with an anterior strut one level above and one level below the fracture site were applied as treatment strategies. VSP plates (Acromed, Cleveland, OH) for posterior instrumentation and the Kaneda system (Acromed, Cleveland, OH) for anterior instrumentation were used. Load-displacement and torque-angle plots were generated and used to calculate 144 estimates of axial stiffness and 144 estimates of torsional rigidity for these constructs. These analyses showed that, in comparison with the intact spine, posterior instrumentation alone was an average of 76% less stiff axially, posterior instrumentation with an anterior strut was 3% more stiff (not significantly different from intact), and anterior instrumentation with an anterior strut was 15% more stiff. Posterior instrumentation alone was an average of 30% less rigid in torsion, posterior instrumentation with an anterior strut was 26% less rigid, and anterior instrumentation with an anterior strut was 24% less rigid than the intact spine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Lumbar spinal stenosis and lower extremity arthroplasty.

Because of their prevalence in elderly patients, the clinical symptoms of acquired lumbar spinal stenosis and degenerative joint disease of the lower extremity can often be present in the same patient. This study reports 14 patients who had diagnoses of both lower extremity degenerative disease and acquired lumbar spinal stenosis. Five of the 14 patients presented with concomitant symptoms, while 9 of 14 patients presented with clinical symptoms of spinal stenosis an average of 9.3 months following joint arthroplasty surgery. Comparison of the preoperative hip and knee scores between the concomitant and sequential groups demonstrated no differences. Seven of the nine patients in the sequential group required subsequent decompression for their spinal stenosis. Stenosis of the lumbar spine must be considered in patients who complain of continuing symptoms of neurogenic claudication in the postoperative period. In addition, these patients should be specifically counseled before their arthroplasty procedures that subsequent spinal surgery may be necessary.

Aged↗
PubMed1993

Short segment transpedicular Cotrel-Dubousset instrumentation: a porcine corpectomy model.

This study examines changes in stiffness in a three-level spinal construct utilizing transpedicular Cotrel-Dubousset instrumentation. In addition, we evaluated the effect of adding offset laminar hooks at the same level as the superior transpedicular fixation. Porcine lumbar spines (L-1 to L-5) were tested as: (a) intact spine, (b) intact spine with instrumentation, and (c) instrumented spine after L-3 corpectomy. Instrumented constructs were tested with and without laminar hooks placed at the level of superior transpedicular fixation. Constructs were tested in modes of axial compression and torsion in a MTS materials testing machine. The fully instrumented intact spines demonstrated a 28.0% stiffness increase over the intact spines in torsion (p < 0.005) and a 23.1% increase in the mode of axial compression (p < 0.0002). There was no statistically significant difference in axial or torsional stiffness in the instrumented intact spine constructs when hooks were added. In the corpectomy model, addition of the laminar hooks increased stiffness in axial compression an average of 26.9% (p < 0.002) and in torsion an average of 28.1% (p < 0.0005). This increase in stiffness may aid in preventing the postoperative progression of kyphosis noted in studies utilizing similar constructs in clinical application for the treatment of lumbar burst fractures.

Animals↗
PubMed1993

Interdependence of lumbar disc and subdiscal bone properties: a report of the normal and degenerated spine.

A nondestructive mechanical testing technique was used to assess midsagittal plane variations in the mechanical properties of human lumbar vertebral bone adjacent to the intervertebral discs of normal and degenerated spines. Bone mechanical properties were compared with midsagittal plane measurements of intervertebral disc (IVD) physical-chemical properties. In the normal spine a heterogeneous midsagittal plane distribution of subdiscal bone stiffness, IVD hydration and fixed charge density was found. Segments with degenerated discs exhibited a lower amount of midsagittal variation in subdiscal bone and IVD properties. A positive linear correlation between subdiscal bone stiffness and IVD fixed charge density was also found, suggesting that an interdependence of IVD and bone properties exists. These results support previous findings and are hypothesized to be an adaptive response to changes in the stress environment in the IVD.

Adult↗
PubMed1992

Mechanical properties of the human lumbar anterior longitudinal ligament.

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.

Adult↗
PubMed1992

Geometric and material property study of the human lumbar spine using the finite element method.

In using the finite element method to examine certain aspects of the mechanical behavior of the human lumbar spine, most investigators have made numerous simplifying assumptions regarding the geometric and material data used to build a model of the spine. Since there are no specific rules for choosing geometric and material data for a "normal" human lumbar spine, considerably different types of models have been used by investigators in their finite element studies. In this study, variations in model geometric and material properties are shown to significantly affect the finite element results of an axisymmetric model of the human lumbar spine under axial compression. The Young's moduli of the cancellous bone and intervertebral disc annulus, Poisson's ratios of the cartilaginous end-plate and disc annulus, the width of the disc annulus, the height of the disc, and the ratio of the disc nucleus pressure and axial pressure are recognized as the parametric variables that most significantly affect the finite element solution.

Biomechanical Phenomena↗
PubMed1992

Distribution and orientation of bone in the human lumbar vertebral centrum.

This article describes regional variations in cancellous bone morphology within the human lumbar spine of a 60-year-old woman. An automated imaging technique, based upon the method of directed secants, was used to quantify variations in bone porosity and trabecular size, distribution, and orientation within serial transverse histological sections of the L1 and L2 vertebral centrum. Several morphologically distinct levels of organization were observed along the axis of the centrum. The superior and inferior sections of the centrum were made up of an open-celled network of trabeculae, while the translational and middle sections consisted primarily of plate-like trabeculae forming a closed-cell structure. The densest and most oriented bone was found in the superior and inferior sections of the posterior-lateral centrum, whereas least dense and least oriented bone was found in the central third of the anterior centrum. Average trabecular thickness did not vary appreciably from level to level, but varied considerably within a given level, particularly in the inferior sections of the centrum. The number of trabeculae was lowest in the central sections of the centrum, where plate-like trabeculae were most prevalent. The topological architecture of different levels within the centrum exhibited a remarkable degree of organization, which suggests that the spine, like other skeletal structures, has adapted to functional stresses produced during daily activities. Detailed morphological data are tabulated and should be of use to investigators interested in modeling the three-dimensional structural and physical properties of the lumbar spine.

Data Display↗
PubMed1992

Transpedicular short-segment fusions for treatment of lumbar burst fractures.

A retrospective review of 13 patients who underwent decompression and transpedicular instrumentation for lumbar burst fractures is presented. Average follow-up was 22.5 months. Eighty-four percent of patients reported little or no pain at follow-up. Sixty-nine percent of patients returned to full preinjury activity. Radiographic review demonstrated an average postoperative progression of kyphosis of 8.7%. Anterior vertebral body height was unchanged between preoperative evaluation and follow-up. Although short-segment posterior transpedicular instrumentation with VSP plates did not reestablish or maintain anatomic alignment of the lumbar spine after burst fractures, the clinical outcome was excellent.

Adolescent↗
PubMed1992

A prospective evaluation of preemployment screening methods for acute industrial back pain.

Preemployment screening methods have been ineffective in predicting those at risk, and in curbing the impact of back problems in industry. Such methods have centered on individual physical factors (capacities and clinical examination). This study evaluates commonly used physical examination measures and simple historical data for its ability to predict individuals at risk for future back injury reporting in the aircraft industry. In this study, once simple historical information about previous pain treatment was known, information gained from physical factors added no significant predictive value.

Adult↗
PubMed1992

A longitudinal, prospective study of industrial back injury reporting.

The authors prospectively evaluated 3020 volunteers of the Boeing-Everett plant to assess risk factors that predispose workers to file industrial back injury claims. During four years of follow-up observation, more than 279 subjects reported acute back problems. The effect of the only predictive physical variable was explainable by a history of medical treatment. The most predictive individual factors were (1) job task dissatisfaction and (2) distress as reported on Scale 3 of the Minnesota Multiphasic Personality Inventory (MMPI). This data perhaps explains why the focus on purely physical and injury-related factors has met with little success in dealing with what has become the most expensive orthopedic problem. Clinically, nonphysical factors that significantly impact the reporting of back injuries may also affect patients' responses to medical treatment.

Accidents, Occupational↗
PubMed1991

Flexion-distraction injuries to the lumbar spine associated with abdominal injuries.

Flexion-distraction injuries to the lumbar spine frequently occur with concomitant abdominal viscus injury. We encountered 16 patients with flexion-distraction lumbar spine injuries. Half of them also suffered abdominal viscus rupture. Lap safety belts were most frequently associated with these injuries; however, the incorrect, underarm use of the shoulder harness was common in our series. The diagnosis of the spinal injury was frequently delayed when abdominal viscus injury occurred together with a flexion-distraction spinal injury. Thorough physical and radiographic examination of the spine as well as a detailed history, including seat belt use, is necessary to diagnose these injuries properly.

Abdominal Injuries↗
PubMed1991

Circumferential fusion for the management of acute cervical spine trauma.

Combined, single-stage anterior and posterior approaches for acute surgical management of cervical spine injury allows for early restoration of anatomic alignment and decompression. Six patients underwent single-stage anterior decompression and posterior instrumentation and fusion at Vanderbilt University Medical Center between 1984-1989. There was no late deformity. Five patients had incomplete neurologic deficits, and each improved a minimum of one Frankel classification. One patient had complete neurologic deficit at the C5 level. The procedure is lengthy, with an average time under anesthesia of 7.7 hs. Since this procedure allows for immediate mobilization, it should be considered for the management of cervical spine fractures with both anterior and posterior column instability.

Adolescent↗
PubMed1991

A prospective study of work perceptions and psychosocial factors affecting the report of back injury.

A longitudinal, prospective study was conducted on 3,020 aircraft employees to identify risk factors for reporting acute back pain at work. The premorbid data included individual physical, psychosocial, and workplace factors. During slightly more than 4 years of follow-up, 279 subjects reported back problems. Other than a history of current or recent back problems, the factors found to be most predictive of subsequent reports in a multivariate model were work perceptions and certain psychosocial responses identified on the Minnesota Multiphasic Personality Inventory (MMPI). Subjects who stated that they "hardly ever" enjoyed their job tasks were 2.5 times more likely to report a back injury (P = 0.0001) than subjects who "almost always" enjoyed their job tasks. The quintile of subjects scoring highest on Scale-3 (Hy) of the MMPI were 2.0 times more likely to report a back injury (P = 0.0001) than subjects with the lowest scores. The multivariate model, including job task enjoyment, MMPI Scale-3, and history of back treatment, revealed that subjects in the highest risk group had 3.3 times the number of reports in the lowest risk group. These findings emphasize the importance of adopting a broader approach to the multifaceted problem of back complaints in industry and help explain why past prevention efforts focusing on purely physical factors have been unsuccessful.

Adult↗
PubMed1991

The treatment of lumbar disc herniation: simple fragment excision versus disc space curettage.

The purpose of this study was to determine whether there was any difference in the clinical outcome between groups of patients treated with lumbar discectomy and vertebral endplate curettage as compared with disc fragment excision without endplate curettage. Eighty-three patients requiring lumbar disc excision for herniated nucleus pulposus were evaluated retrospectively at minimum 2-year follow-up. Forty-three patients had undergone fragment excision and disc space curettage at one center, whereas 40 patients underwent fragment excision without curettage at two other centers. There was no increased rate of reherniation or reoperation in the excision-only group. Vertebral endplate curettage carries a risk of annular penetration and damage to the great vessels. This study shows that this potentially dangerous step of the operation is unwarranted. In addition, patients who underwent endplate curettage had a higher incidence of low-back pain on follow-up.

Adult↗
PubMed1990

Young's modulus, bending strength, and tissue physical properties of human compact bone.

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.

Aged↗
PubMed1990

Herniated intervertebral discs associated with unstable spinal injuries.

To examine the occurrence of traumatic herniated intervertebral discs associated with unstable spinal injuries, the authors reviewed the records of all patients with spinal cord level unstable spine injuries managed at their institution over a 26-month period. Ninety-three patients were identified. All patients had roentgenographic and computed tomographic (CT) evaluation. Magnetic resonance imaging was performed in 48 patients, and revealed the presence of a herniated intervertebral disc in 16, with the highest incidence being in the cervical spine. In the patients who had only plain film and CT scans, no disc pathology was identified. Magnetic resonance imaging provides a noninvasive means of examining intervertebral disc damage in unstable spinal injuries that might otherwise be unidentified and result in spinal cord injury at the time of surgery.

Adult↗
PubMed1990

1990 Volvo Award in experimental studies. The dependence of intervertebral disc mechanical properties on physiologic conditions.

In vivo creep-recovery and disc pressure measurements were performed on the lumbar spine of immature and mature swine. The creep-recovery measurements were performed using a custom materials testing apparatus designed to apply static or dynamic loads to the spine of anesthetized animals. A series of three separate experiments were performed to assess the effects of: (I) animal death, (II) graded injury to the disc anulus, and (III) respiratory mechanics on the biomechanical response of the porcine L1-L3 vertebral unit (VU). In Experiments I and II, creep rate, modulus, and viscosity parameters were computed using a three-parameter solid rheological analysis of the displacement-time response recorded during the application of a 300-N load. In Experiment III, the effects of respiratory volume and frequency changes on disc pressure were assessed in the unloaded, statically loaded, and immobilized porcine VU. Our results indicated that the adult VU tended to be stiffer, deform or creep more slowly, and had a significantly higher viscosity than the VU of immature pigs. The results of Experiment I demonstrated that the biomechanical response for the VU was significantly altered by the death of the animal; the VU of the living animal (adolescent or mature) was more compliant and deformed at a faster rate than the VU of the same animal after death. Disc injury produced changes in stiffness, viscosity, and creep rate analogous to that of aging, and on the basis of the graded injuries created in this study, it appears that a small defect in the annulus is just as deleterious as removing a large section of anular material. The results of Experiment III indicated that respiration plays an important role in the normal, in vivo mechanical and nutritional behavior of the porcine VU. Altogether, these results demonstrate that, in the absence of normal physiologic conditions, one may not be able to reliably predict the mechanical response of the lumbar spine, and suggest that standards for the testing, handling, and storage of biologic tissue should be established.

Animals↗