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Biomedical subjects

E C Benzel

Publications and source records attributed to E C Benzel.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1994

The single burr hole technique for the evacuation of non-acute subdural hematomas.

A 4-year retrospective study was made of 111 consecutive surgically treated patients with chronic or subacute subdural hematomas. All underwent single burr hole evacuation with accompanying saline irrigation of the subdural space. Postoperative outcomes at 6 weeks were 90% excellent, 5.5% fair, and 4.5% poor. Postoperative re-evacuation was performed either by needle aspiration or reoperation via the burr hole on 12 patients; one required a craniectomy and neomembrane stripping. These results compare favorably with previous data and support the use of the single burr hole technique as a simple and effective treatment of subacute and chronic subdural hematomas. This addresses the decompression of the brain parenchyma, the removal of the residual semisolid subdural hematoma component, and the removal, dilution, and inactivation of endogenous fibrinolytic agents.

Chronic Disease↗
PubMed1994

The incidence of vertebral artery injury after midcervical spine fracture or subluxation.

Twenty-six patients with blunt trauma of the cervical spine, producing a subluxation from a "locked" or "perched" facet, facet destruction with evidence of instability, or a fracture involving the foramen transversarium, underwent preoperative vertebral angiography to determine the incidence of vertebral artery injury. The cervical spine injury in all the patients was deemed unstable and in need of surgical stabilization. Spinal cord injury was present in one-half of the patients studied. Vertebral artery injury was identified angiographically in 12 patients (46%). Occlusion of the vertebral artery near its origin or at the level of the spinal injury was identified in nine patients. An intimal flap, arterial dissection, and a pseudoaneurysm were identified in the remaining three patients. The injury involved the left vertebral artery in all but three patients. In none of the patients did the vertebral artery injury clearly result in neurological dysfunction or other sequelae. After cervical spine fracture or dislocation, vertebral artery injury is more prevalent than commonly believed. The possibility of vertebral artery injury should be considered during the establishment of clinical management schemes for blunt trauma of the cervical spine.

Adolescent↗
PubMed1994

A simple method to ensure proper screw position and plate size selection using the Morscher cervical spine locking plate. Technical note.

The use of bone plate instrumentation with screw fixation has proved to be a useful adjunctive measure in anterior cervical spine fusion surgery. Proper fitting, positioning, and attachment of this instrumentation have been shown to be frequently suboptimal if done without radiographic guidance. The most commonly used method of radiographic assistance for placement of this instrumentation is fluoroscopy. While this gives satisfactory technical results, it is expensive and time-consuming, and exposes the patient and the operating room personnel to ionizing radiation. The authors present a simple technique to ensure screw placement and plate fitting using Kirschner wires and a single lateral radiograph. This technique saves time, reduces exposure to radiation, and has led to satisfactory results in over 20 operative cases.

Bone Plates↗
PubMed1994

Fractures of the C-2 vertebral body.

Vertical C-2 body fractures are presented in 15 patients with clinical and imaging correlations that suggest the existence of a variety of mechanisms of injury. In these patients, clinical and imaging correlations were derived by: 1) defining the point of impact by clinical examination; 2) defining the point of impact by soft-tissue changes on cranial magnetic resonance (MR) imaging or computerized tomography (CT); 3) obtaining an accurate history of the mechanism of injury; and 4) spine imaging (x-ray studies, CT, and MR imaging) of the C-2 body fracture and surrounding bone and soft tissue. The cases presented involve the region located between the dens and the pars interarticularis of the axis. Although these fractures are rarely reported, they are not uncommon. An elucidation of their pathological anatomy helps to further the understanding of the mechanistic etiology of upper cervical spine trauma. A spectrum of mechanisms of injury causing upper cervical spine fractures was observed. The type of injury incurred is determined predominantly by the force vector applied during impact and the intrinsic strength and anatomy of C-2 and its surrounding spinal elements. From this clinical experience, two types of vertical C-2 body fractures are defined and presented: coronally oriented (Type 1) and sagittally oriented (Type 2). A third type of C-2 body fracture, the horizontal rostral C-2 fracture (Type 3), is added for completeness; this Type 3 fracture is the previously described Type III odontoid process fracture described by Anderson and D'Alonzo.

Adult↗
PubMed1994

Sacral fixation using iliac instrumentation and a variable-angle screw device. Technical note.

Secure fixation of the sacrum is technically challenging. The bone of the dorsal sacral surface is often thin, making hook fixation tenuous. The use of bone screws in the sacral pedicles has gained popularity, but rigidity is often not achieved and screw pullout is common. Solid constructs have been achieved using angled rods to stabilize the ilium, but these methods are technically difficult and time-consuming to perform. A technique is described that achieves rigid sacral fixation by adding a bone screw placed through both cortical surfaces of the ilium. This bone screw is a new type that allows attachment to a rod at variable angles. It permits easy attachment to an appropriately contoured rod, which is affixed to sacral hooks or screws. The resulting configuration of the bone-metal interface creates a tripod for load distribution. Additionally, the splayed geometry of these purchase sites provides a significant biomechanical advantage preventing the instrument from being pulled out. The technique for this fixation method, particularly for patients with complex spinal disorders, is described. Use of this new technique provides significant advantages to the spine surgeon in situations in which substantial sacral fixation integrity is necessary.

Biomechanical Phenomena↗
PubMed1994

Preoperative spinal angiography for lateral extracavitary approach to thoracic and lumbar spine.

PURPOSE: To establish the safety, efficacy, and value of preoperative angiography in the surgical management of thoracic and lumbar spine disease, in which it is important to avoid injury to the artery of Adamkiewicz or other vessels that supply the spinal cord. METHODS: Sixty-one patients were evaluated primarily using digital subtraction angiography, low-osmolar or nonionic contrast agents, selective catheterization limited to the region of disease, and careful angiographic techniques. RESULTS: Two minor (small hematomas of the groin) and no major complications of angiography were encountered. Arterial supply to the spinal cord was identified in 22 patients. In 17 patients (77%), the arterial supply was in the region of planned surgery. In each of these patients the surgical approach was altered, either by dictating the use of a posterior surgical approach (four patients) or by altering the side of the lateral extracavitary approach (13 patients). CONCLUSION: Spinal angiography is a safe preoperative examination for thoracic and lumbar spine surgery. It is specifically useful when the lateral extracavitary surgical approach to spinal cord decompression and fusion (which predictably interrupts the terminal end-arterial blood supply to the spinal cord, if present) is planned.

Adolescent↗
PubMed1993

The treatment of hydrocephalus in preterm infants with intraventricular haemorrhage.

The hospital charts and clinical course of forty-one patients requiring one or more ventricular drainage procedures for hydrocephalic complications of neonatal intraventricular haemorrhage were evaluated retrospectively. All drainage procedures were performed on patients with intraventricular haemorrhage with ventricular dilatation (Grade III [25 patients]) and intraventricular and intraparenchymal haemorrhage (Grade IV [16 patients]) who were medical management failures. Twenty-six ventricular reservoirs (Rickham or McComb reservoirs) were placed in neonates weighing less than 1500 grams, allowing for a safe but intermittent ventricular access. Eighteen of these reservoirs were subsequently converted to ventriculoperitoneal shunts. Thirty-two percent of the patients incurred a shunt and/or reservoir infection and 59% required a shunt revision during the first year of life. There was no mortality related to the neurosurgical interventions. These results compare favorably with the published literature. No grade IV patients achieved a normal functional level, while 10 grade III patients did. The incidence of severe developmental delay (44% versus 28%) and death (38% versus 12%) was greater in the grade IV than the grade III patients. The placement of ventricular reservoirs is acceptable as an alternative to the early placement of ventriculo-peritoneal shunts. This approach may reduce the incidence of shunt infection as well as noninfectious shunt complications.

Brain Damage, Chronic↗
PubMed1993

Magnetic source imaging: a review of the Magnes system of biomagnetic technologies incorporated.

Magnetic source imaging (MSI) is a new, noninvasive technique for defining the relationship between brain function and structure on a patient-to-patient basis. It achieves this by combining detailed neurophysiological data derived from magnetoencephalography with high-quality neuroanatomical data derived via magnetic resonance imaging. By the use of mathematical models, the spatial locations of those neurons that generate neuromagnetic signals of interest are estimated and subsequently marked on spatially aligned magnetic resonance images. There are three prominent types of clinical MSI examinations. These are: 1) functional mapping examinations in which sensory and motor functions are localized; 2) examinations of interictal epileptiform activity; and 3) examinations of abnormal low-frequency magnetic activity, which has been found to be present in a wide range of pathophysiological conditions. Functional mapping provides useful information regarding the relationship between the cortical representation of eloquent function and the location of pathological lesions that may be surgically resectable. This application is of particular utility in cases of intracortical masses that distort and obscure the local neuroanatomy. By defining the primary sites of interictal epileptiform activity, MSI examinations are useful in the surgical planning for the implantation of depth electrodes and the planning of partial lobectomies. Abnormal low-frequency magnetic activity appears to be a neurophysiological correlate of ischemic penumbra associated with stroke, neoplasms, and vascular malformations. Abnormal low-frequency magnetic activity has also been found to be present in several other conditions, including head trauma and psychiatric dysfunction, although the exact pathophysiological mechanisms are presently unclear.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain Mapping↗