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Biomedical subjects

E C Benzel

Publications and source records attributed to E C Benzel.

At least 19 recordsLinked to original sources
PubMed1998

Evidence for cerebellar-frontal subsystem changes in children treated with intrathecal chemotherapy for leukemia: enhanced data analysis using an effect size model.

BACKGROUND: Following brain insult in early childhood, the later maturing neocerebellum and frontal lobes frequently show abnormalities. OBJECTIVE: To investigate the morphologic characteristics and function of a proposed cerebellar-frontal subsystem in children treated for acute lymphoblastic leukemia (ALL) with intrathecal methotrexate using quantitative magnetic resonance imaging, neuropsychological measures, nonlinear multiple regression analysis, and a statistical effect size model that augments interpretive validity of nonsignificant statistical findings, particularly from small sample size studies. DESIGN: Comparison and relationship of magnetic resonance imaging morphometry of cerebellar lobuli I-V and VI-VII and prefrontal cortices, and performance on 5 neuropsychological tests assessing visual-spatial attention, short-term memory, and visuomotor organization and coordination between childhood survivors of ALL and a matched control group. PARTICIPANTS: Ten childhood survivors of ALL treated between 1982 and 1989 with standard 3-year intrathecal chemotherapy, and matched control subjects. MAIN OUTCOME MEASURES: Morphometric results of cerebellar lobuli I-V and VI-VII and prefrontal cortices, and results of Trail-Making Tests, Rey-Osterreith Complex Figure Test, WISC-III Coding. RESULTS: Significant effect size model values for outcome measures in the ALL group support deficits in lobuli VI-VII and prefrontal cortices, and neuropsychological performance. Multiple regression analysis results were consistent with hypothesized involvement of a cerebellar-frontal brain subsystem. CONCLUSION: Treatment of children with ALL with intrathecal methotrexate before 5 years of age has structural and functional effects on the developing neocerebellar-frontal subsystem.

Adolescent↗
PubMed1998

Lateral extracavitary approach for thoracic and thoracolumbar spine trauma: operative complications.

BACKGROUND: The lateral extracavitary approach (LECA) to the thoracic and thoracolumbar spine allows ventral decompression and dorsal fixation of the spine through the same incision during a single procedure. The approach, however, is technically demanding and time-consuming. We sought to determine the incidence of complications associated with the LECA in patients with acute thoracolumbar spine injuries. PATIENTS AND METHODS: A retrospective chart review of all patients with acute fractures or dislocations of the thoracic or thoracolumbar spine who underwent surgery via the LECA was conducted to assess the incidence and type of perioperative complications associated with the LECA. RESULTS: Thirty-three patients with thoracic or thoracolumbar spine injuries treated using the LECA between June 1990 and June 1996 were identified and had available medical records. Complications occurred in 18 of these patients. Pulmonary complications predominated. Eleven patients required tube thoracostomy for hemothorax or persistent pleural effusions, and seven patients developed postoperative pneumonia. There were no cases of neurological worsening. There was no mortality. CONCLUSION: Decompression and stabilization of acute thoracolumbar fractures with the LECA in the acute setting is associated with a 55% incidence of morbidity. Whereas some of this morbidity may be attributed to the effects of the injury, there is a certain intrinsic morbidity associated with the LECA. Although this morbidity may compare favorably with that of sequential ventral/dorsal approaches, the biomechanical advantages obtained with a combined ventral and dorsal construct must be balanced against the inherent morbidity of such approaches.

Decompression, Surgical↗
PubMed1997

The management of unilateral lateral mass/facet fractures of the subaxial cervical spine: the use of magnetic resonance imaging to predict instability.

STUDY DESIGN: Retrospective review of the clinical course and cervical spine plain radiographs, computed tomography, and magnetic resonance imaging of 24 consecutive patients for a 2-year period with a unilateral lateral mass/facet fracture. OBJECTIVE: To propose a treatment algorithm for the management of unilateral lateral mass/facet fractures of the subaxial cervical spine based on ligamentous injury detected by magnetic resonance imaging. SUMMARY OF BACKGROUND DATA: There have been no previous reports of the use of magnetic resonance imaging to predict clinical instability. METHODS: A retrospective review of the clinical course of all unilateral mass/facet fractures identified over a 2-year period was conducted. All cervical spine plain radiographs, computed tomography scans, and magnetic resonance images were reviewed by a neuroradiologist blinded to the clinical course of the patient. Magnetic resonance T1-weighted and inversion recovery images were used to evaluate the integrity of the facet region, interspinous ligament, anterior longitudinal ligament, and posterior longitudinal ligament. RESULTS: Twenty-four unilateral lateral mass/facet fractures were identified. Only six initial cervical spine series demonstrated a bony abnormality at the level of the fracture. The fractures were identified by computed tomography and were almost all nondisplaced or minimally displaced. Less than half of the fractures extended ventrally to involve the transverse process or foramen transversarium or dorsally to involve the lamina. Twelve fractures were nonoperatively treated and 12 were treated surgically for stabilization. Ten patients in the operative group presented with or developed a subluxation. Nine of these patients had injury to at least three of the four ligaments evaluated by magnetic resonance imaging. In the nonoperative group, only three patients had extensive ligamentous injury at the level of the fracture. All three of these patients were lost to follow-up. CONCLUSIONS: Plain radiographs of the cervical spine lack sensitivity to detect the presence of lateral mass/ facet fractures. The appearance of the fracture on computed tomography does not indicate instability. The degree of ligamentous injury at the level of the fracture demonstrated on magnetic resonance imaging correlates with instability in this series. Operative stabilization may be indicated for unilateral lateral mass fractures that present with a subluxation or that have injury to at least three of the following ligaments: the facet region, the interspinous ligament, the anterior longitudinal ligament, and the posterior longitudinal ligament. However, before a definitive management plan can be formulated, results from this small series require further validation.

Adult↗
PubMed1997

The metabolic response to spinal cord injury.

The metabolic response to trauma, including neurotrauma in general, has been studied extensively, but the acute metabolic response to spinal cord injury (SCI) has not. Therefore, 12 patients with SCI are presented in whom intensive nutrition assessment and management were instituted immediately after injury. Nitrogen balance (NB), predicted energy expenditure (PEE), and actual energy expenditure (MEE) were calculated or measured in each patient. A persistent negative NB was observed in all but one of the 12 patients. The single patient who did not exhibit persistent negative NB (no positive NB from week 2 to week 4 in the face of appropriate feeding) had an incomplete myelopathy, thus implying that the degree of motor dysfunction correlates with the obligatory nature of the negative NB. The negative NB observed in several of the patients did not occur until the second or third post-injury week. In addition, calculations of PEE by successively multiplying the Harris-Benedict equation by an activity factor of 1.2 and then by a stress factor of 1.6, resulted in excessive feeding (as assessed by metabolic cart measurements; ie indirect calorimetry) in the majority of the patients. In all of the 11 patients with persistent negative NBs, protein administration in the amount of 2 g/k of ideal body weight and aggressive caloric delivery did not alter the negative pattern of the NBs. Therefore, it is concluded that the negative NB following SCI is obligatory. Furthermore, the extent of SCI (extent of myelopathy or of neurological injury) correlates with the obligatory nature of the negative NB. In addition, the results from using the above method for estimating caloric requirements and the delayed manifestation of the negative NB may cause an additional tendency to acutely overfeed SCI patients. Therefore, eliminating the activity factor of 1.2 (due to the diminished activity arising from paralysis) and a diminution of the stress factor is recommended for initial PEE calculations. Serial metabolic cart (indirect calorimetry) measurements are recommended to accurately assess the patient's subsequent metabolic requirements.

Adult↗
PubMed1997

Biomechanics of the thoracolumbar spine.

The thoracolumbar spine is the principal load-bearing structure of the body. As such, it is subject to a wide variety of forces that can be described by biomechanical principles. Forces act through vectors, depending on the direction of force and the relative location of the instantaneous axis of rotation. Patterns of failure due to supraphysiologic loading or through the loss of structural integrity may be predicted based on the applied force vectors and the stabilization components lost. An understanding of these forces and their effects on the spine is crucial for the safe and efficacious treatment of spinal deformities.

Biomechanical Phenomena↗
PubMed1996

Surgical needle design: torsion resistance.

OBJECTIVE: The interface between a surgical needle and forceps affects needle-forceps stability. Stability has become more important with the introduction of blunt-point surgical needles. The stability at the needle-forceps interface can be assessed by quantitating resistance to both rotation and twisting. Two commonly used surgical needles are the MO and CT needles, which are particularly useful for soft tissue closure for which significant strength of closure is required. Their comparison is thus of importance to surgeons. The design of the MO needle (greater flat section width than the CT needle) should allow for a greater resistance to rotation at the needle-forceps junction. This theoretically makes the MO needle a better choice when blunt-point needles (which require a greater force to penetrate tissue) are used. The objective of this study is to document and quantitate the differences, if any, between the CT and MO needles with regard to rotation and twisting at the needle-forceps junction. METHODS: To compare the efficacy of the CT and MO needles with regard to needle-forceps stability, the resistance of the needles to rotation and twisting was assessed using a Hios HP-10 digital torque meter. RESULTS: The resistance to twisting of the CT and MO needles was not significantly different. However, the MO needle is 25% more resistant to rotation than the CT needle. This differed by 10% from the expected difference. CONCLUSION: The resistance to twisting is not significantly affected by needle geometry, whereas the resistance to rotation is significantly affected. The difference between expected and observed differences in rotation is explained by study design.

Equipment Design↗
PubMed1996

Magnetic resonance imaging for the evaluation of patients with occult cervical spine injury.

Because it is often difficult to diagnose accurately the structurally intact cervical spine after acute trauma, a series of patients was evaluated with magnetic resonance (MR) imaging to assess its efficacy for the evaluation and clearance of the cervical spine in a trauma victim in the early posttrauma period. Ultralow-field MR imaging was used to evaluate 174 posttraumatic patients in whom physical findings indicated the potential for spine injury or minor radiographic findings indicated injury. This series includes only those patients who did not appear to harbor disruption of spinal integrity on the basis of a routine x-ray film. None had clinically obvious injury. Of the 174 patients, 62 (36%) had soft-tissue abnormalities identified by MR imaging, including disc interspace disruption in 27 patients (four with ventral and dorsal ligamentous injury, three with ventral ligamentous injury alone, 18 with dorsal ligamentous injury alone, and two without ventral or dorsal ligamentous injury). Isolated ligamentous injury was observed in 35 patients (eight with ventral and dorsal ligamentous injury, five with ventral ligamentous injury alone, and 22 with dorsal ligamentous injury alone). One patient underwent a surgical fusion procedure, 35 patients (including the one treated surgically) were placed in a cervical collar for at least 1 month, and 27 patients were placed in a thermoplastic Minerva jacket for at least 2 months. All had a satisfactory outcome without evidence of instability. The T2-weighted sagittal images were most useful in defining acute soft-tissue injury; axial images were of minimal assistance. Posttraumatic soft-tissue cervical spine injuries and disc herniations (most likely proexisting the trauma) are more common than expected. A negative MR image should be considered as confirmation of a negative or "cleared" subaxial cervical spine. Diagnostic and patient management algorithms may be appropriately tailored by this information. Thus, MR imaging is useful for early acute posttrauma assessment in a very select group of patients.

Adolescent↗
PubMed1995

Anatomy of the thoracic pedicle.

Thoracic pedicle anatomy (interpedicular distance, transverse and sagittal pedicle widths, transverse and sagittal pedicle angles, and the distance from the axis of the pedicle to the axis of the transverse process) was assessed in 11 cadavers of elderly people. The cadaveric spines were extensively dissected to augment the accuracy of the measurements via caliper and goniometer. The results were compared with those of previous studies that assessed pedicle anatomy with computed tomography, direct measurement, and three-dimensional morphometry. Between the studies, significant differences were found in transverse pedicle width and transverse and sagittal pedicle angles. These morphometric differences may reflect either the diversity of the techniques used to measure the pedicle anatomy or sampling variation. This article presents a previously unreported morphometric finding, the rostral-caudal distance from the thoracic pedicle to the midpoint of the base of the transverse process. At T1, the transverse process is 5.45 +/- 1.2 mm rostral to the pedicle. This relationship gradually changes as the thoracic spine is descended, so that at T12, the transverse process is 6.6 +/- 2.4 mm caudal to the pedicle. Crossover consistently occurs at the T6-T7 region. Although the transverse process is a reliable external landmark for the location of the pedicle in the lumbar spine, this relationship in the thoracic spine is variable and only moderately predictable.

Aged↗
PubMed1995

A comparison of fluoroscopy and computed tomography-derived volumetric multiple exposure transmission holography for the guidance of lumbar pedicle screw insertion.

Holographic technology has recently been modified in such a manner that it may now provide clinical use. It allows the visualization of complex structures in three dimensions and permits clinician interaction with the image, which, in turn, provides significant additional geometric and anatomic information. To objectively assess the potential clinical applicability of holography in pedicle screw placement, we studied 11 elderly human cadavers. All of the cadavers, each of which showed significant degenerative disease of the lumbar spine, underwent thin-section computed tomographic scans of the lumbar spine. The acquired digital information was processed, and volumetric multiple exposure transmission holographic images were rendered. Pedicle screws were passed into anatomically acceptable and radiographically visualized L3-L5 pedicles in each cadaver, half using fluoroscopic guidance and half using holographic guidance alone. The accuracy of screw placement was objectively assessed by a three-point grading scale. The total score for the placement of each pedicle screw was determined by both trajectory (location within the pedicle) and accuracy (containment within the vertebral body) of screw tip placement parameters. Three points were possible for each screw placed. Screw placement in the last six cadavers was individually timed for each technique, and fluoroscopic time was also recorded. Each technique was used on 27 pedicles. The total score for fluoroscopic screw placement was 71 (71 of a possible 81; 88%) and for holographic screw placement was 74 (74 of a possible 81; 91%). In the last six cadavers, the screw placement time (per cadaver) was 8 minutes for fluoroscopic placement and 3.6 minutes for holographic placement. Fluoroscopic time averaged 1.9 minutes per cadaver.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Crossed-screw fixation of the unstable thoracic and lumbar spine.

An ideal spinal construct should immobilize only the unstable spinal segments, and thus only the segments fused. Pedicle fixation techniques have provided operative stabilization with the instrumentation of a minimal number of spinal segments; however, some failures have been observed with pedicle instrumentation. These failures are primarily related to excessive preload forces and limitations caused by the size and orientation of the pedicles. To circumvent these problems, a new technique, the crossed-screw fixation method, was developed and is described in this report. This technique facilitates short-segment spinal fixation and uses a lateral extracavitary approach, which provides generous exposure for spinal decompression and interbody fusion. The technique employs two large transverse vertebral body screws (6.5 to 8.5 mm in diameter) to bear axial loads, and two unilateral pedicle screws (placed on the side of the exposure) to restrict flexion and extension deformation around the transverse screws and to provide three-dimensional deformity correction. The horizontal vertebral body and the pedicle screws are connected to rods and then to each other via rigid crosslinking. The transverse vertebral body screws are unloaded during insertion by placing the construct in a compression mode after the interbody bone graft is placed, thus optimizing the advantage gained by the significant "toe-in" configuration provided and further decreasing the chance for instrumentation failure. The initial results of this technique are reported in a series of 10 consecutively treated patients, in whom correction of the deformity was facilitated. Follow-up examination (average 10.1 months after surgery) demonstrated negligible angulation. Chronic pain was minimal. The crossed-screw fixation technique is biomechanically sound and offers a rapid and safe form of short-segment three-dimensional deformity correction and solid fixation when utilized in conjunction with the lateral extracavitary approach to the unstable thoracic and lumbar spine. This approach also facilitates the secure placement of an interbody bone graft.

Adolescent↗
PubMed1995

Failure of a titanium anterior cervical plate implant: microstructural analysis of failure. Case report.

The authors present the case of a failed titanium anterior cervical spine plate. The plate was contoured during implantation. Analysis of the failed implant with electron microscopy showed no metallurgical flaw to have caused the plate fracture. A crack was apparently initiated with the contouring of the plate. It was located at the weakest point in the plate (the position of the intermediate screw hole), and with subsequent stress, it propagated and led to fracture. Techniques for avoiding failure of this type are discussed.

Bone Plates↗
PubMed1994

Metabolic changes following cortical contusion: relationships to edema and morphological changes.

Rats with contusion injury to the right cortex exhibited significant formation of edema 6 and 24 hours after injury which resolved by 8 days and was replaced by cavitation necrosis. The contusions produced hyperglycolysis and ischemia in the impacted cortical tissue and underlying hippocampus immediately through 30 minutes post-injury. Glucose utilization was depressed throughout the contused cortex and in ipsilateral subcortical regions, as was blood flow, at chronic (1 and 10 days) periods after injury.

Animals↗