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Biomedical subjects

D J Maiman

Publications and source records attributed to D J Maiman.

At least 55 records · Page 3Linked to original sources
PubMed1988

Magnetic resonance imaging in the diagnosis of lower thoracic disc herniation.

The diagnosis of thoracic disc herniation can be difficult due to the lack of a characteristic clinical presentation. In six recent cases, magnetic resonance imaging (MRI) provided excellent noninvasive definition of the pathology and its level, in spite of atypical clinical presentation, and also provided anatomic information allowing surgical planning. Two examples are presented in which myelography was not helpful, but MRI was diagnostic. MRI scanning is the radiographic procedure of choice when thoracic disc herniation is in the differential diagnosis.

Adult↗
PubMed1987

Spinal cord stimulation for amelioration of spasticity: experimental results.

Fourteen cats underwent 500-g/cm dorsal impact injuries to the spinal cord and the placement of stimulating electrodes above and below the level of injury at T8. After recovery from the surgical procedure and the development of spasticity, each animal participated in several trials of spinal cord stimulation (SCS). Cord stimulation was provided above or below the level of injury using currents of less than 0.75 mA at 100 Hz. Electromyogram changes in hamstring and quadricep muscles (during spasms induced by dorsiflexion of the paw) were monitored. All animals showed complete paraplegia and, at 3 weeks, severe spasms. Spasticity was aggravated by SCS delivered above the level of injury. Spasms were markedly suppressed by monopolar stimulation delivered below the level of the lesion. Effects were maximal with the negative electrode applied to the cord and were slightly less with reversal of polarity. Muscle excitation was seen before diminution of spasms when bipolar currents were used. All effects lasted only as long as currents were delivered. These animal trials suggest that the effects of SCS are directly related to the current and its type. Beneficial effects were seen only when currents were delivered below the level of injury; this suggests that SCS activates local inhibitory processes or depolarizes local excitatory pathways. The poor results with bipolar stimulation do not support action on a multisynaptic cord system in short term stimulation.

Animals↗
PubMed1986

Experimental spinal injuries with vertical impact.

Fifteen fresh, intact, human male cadavers suspended head down were dropped vertically from a height of 0.9-1.5 meters. In eight specimens the heads were restrained to simulate muscle forces. The head-neck complex was oriented for maximal axial loading of the cervical and upper thoracic spine. In several cadavers, load cells were placed in cervical bodies. Head impact forces of 3,000-7,000 N in the unrestrained, and 9,800-14,600 N in the restrained, cadavers were recorded. There were more cervical and upper thoracic fractures in the restrained cadavers than in the nonrestrained subjects. The biomechanic and pathologic findings, including results of cryomicrotomography and computed tomography (CT), are discussed.

Aged↗
PubMed1986

Management of bilateral locked facets of the cervical spine.

A total of 28 cases of cervical spine dislocation with bilateral locking of facets treated between 1976 and 1984 were analyzed to determine whether treatment modality had any effect on outcome based on cord or root function. Motor vehicle accidents were responsible for 19 cases; the most common levels of dislocation were C-5, C-6 and C-6, C-7, with 10 each. Twenty patients were admitted with complete myelopathies. Ten patients whose dislocations were successfully reduced with traction had no neurological changes, but 1 reduced elsewhere deteriorated from a C-5 to C-2 level. Eleven of these patients underwent posterior cervical fusions after delays of 1 to 17 days (mean = 6.3); 2 died, and 1 patient achieved slight root return. Seven underwent anterior decompression and fusion or combined anterior and posterior approaches after delays of 9 to 120 days. One patient died in the postoperative period, 1 had substantial recovery of cord function, and 5 had recovery of root function. There was no operation or improvement in 2 patients. Eight patients had incomplete myelopathies; 4 were initially reduced, with 2 improving slightly as a result. Three patients underwent posterior fusions with foraminotomies with minimal improvement. Five had anterior or combined approaches; these patients improved at least one neurological grade each, including 3 who became newly ambulatory. All 24 surviving patients achieved spinal stability, although it occurred slightly earlier in the anterior fusion groups. Surgical approaches designed to provide spinal stability and restore the normal anatomy of the spinal canal and neural foramina may be of functional benefit in the management of these dislocations.

Adolescent↗
PubMed1986

BSS Plus: a potential irrigating solution for neurosurgery.

BSS Plus is a pH-stable balanced salt solution similar to glutathione bicarbonate Ringer's solution. Extensively used in ophthalmology, it is of potential value in neurosurgery. In comparative tests of its effectiveness, 28 cats underwent bilateral irrigation of the surface of the cerebral cortex with normal saline on one side and BSS Plus on the other. After 2 hours, a marked decrease was seen in the surface pH of the hemisphere irrigated with normal saline but not of the hemisphere treated with BSS Plus. Blood-brain barrier changes (measured with Evans blue dye techniques) were more evident following saline irrigation. Somatosensory evoked potentials and cerebral blood flow were not significantly altered. Conventional light microscopy using three standard stains did not reveal a significant difference. Transmission electron microscopy studies were performed in 14 animals and scanning electron microscopy in six. In five animals both transmission and scanning electron microscopy studies were conducted after irrigation with both agents without a cottonoid cover and with immediate harvest of superficial layers from the living brain and immersion-fixation in glutaraldehyde. Tissue preservation was superior on the BSS Plus side in all studies. This agent may represent an improved irrigation solution for neurosurgery, but further studies are required.

Animals↗
PubMed1985

Nonoperative management of traumatic facial nerve palsy.

Forty-five patients with facial nerve palsy resulting from head injury were treated nonoperatively between 1975 and 1981. Of 31 patients who had polytomography, temporal bone fractures were demonstrated in 29. In 44 of 45 injuries, satisfactory clinical improvement in motor function was noted, including 65% (overall) who showed complete recovery. Fracture direction on polytomography, results of electromyography (performed in ten cases), and time of onset of paralysis were not correlated with outcome. The present findings suggest a limited role for early surgery in closed traumatic facial nerve palsy.

Adolescent↗
PubMed1985

Comparison of the failure biomechanics of spinal fixation devices.

The failure biomechanics of Harrington distraction rods, modified Weiss springs, and Luque rods were studied in intact cadavers and isolated spinal columns using flexion-compression loading. Most spines fractured at T-11 or T-12 at applied loads ranging between 556 and 4220 newtons (mean = 1833 N). After Harrington distraction rod placement, the same spines failed at a mean load of 859 N (42% of control), always as a result of hook extrusion and often including lamina fracture (seven cases). When modified Weiss springs were used, the spines failed at a mean load of 1128 N (54% of control) by allowing the spine to bend to the initial failure angle; in most instances, deformities resolved when the load was reduced. Luque rods were tested in four specimens; these provided the most rigid stabilization and failed at 83% of control values. Modified Weiss springs often maintain spinal stability better than Harrington distraction rods.

Aged↗
PubMed1984

Lateral extracavitary approach to the spine for thoracic disc herniation: report of 23 cases.

Twenty-three patients were operated upon for thoracic disc herniation between 1973 and 1982. The lateral approach to the vertebral column was used in each. Most patients had severe local pain; 13 had severe myelopathy or complete motor paralysis, including 4 who had become paraplegic after laminectomy. Eleven patients had calcified discs or osteophytic ridges. Air myelography and computed tomography were diagnostic in all cases. Postoperatively, 17 patients achieved significant relief of pain, 20 improved neurologically, and none became worse. Complications of the operation were minimal. The lateral extracavitary approach to the spine is a valuable technique for the management of thoracic disc herniation.

Adolescent↗
PubMed1984

Neurological improvement associated with late decompression of the thoracolumbar spinal cord.

We reviewed the cases of 20 patients admitted to our institution with thoracolumbar spinal cord injury who had previously undergone laminectomy and/or spinal instrumentation. Thirteen patients had a mass in the spinal canal, and 7 had kyphotic deformities. The lateral extracavitary approach to the spine and posterior stabilization when indicated were done in each. Seventeen patients obtained substantial neurological improvement. All 7 patients with kyphosis regained the ability to walk, as did all but 3 of the nonambulatory patients with a mass in the spinal canal. Morbidity was limited to pneumothorax and 1 case of late kyphosis associated with premature removal of the spinal fixation devices. Elective anterior approaches for reconstruction of the spinal canal with appropriate stabilization afford the best opportunity for neurological improvement in cases of thoracolumbar spinal cord injury.

Fracture Fixation↗
PubMed1984

Electrophysiological effects of lumbar dorsal root stimulation.

Electrical stimulation was applied to the L-5 and L-6 dorsal root ganglia of 14 monkeys with concurrent monitoring of cortical and intralaminar thalamic evoked potentials. Both responses were decreased by root stimulation, although cortical suppression required current levels 50 to 100% higher. The evoked potentials remained suppressed for periods of up to 60 minutes after 10- to 15-minute stimulation of the lumbar root electrodes. There was no increase in the duration of transmission block with longer stimulation periods. These results and available clinical data suggest that a local conduction block may be responsible for the pain relief produced by peripheral electrical stimulation. Further studies to identify more precisely the neural systems affected are required.

Afferent Pathways↗
PubMed1984

The biomechanics of spinal injuries.

This manuscript is directed to review the epidemiology of spinal trauma, the anatomy of the vertebral column, spinal ligaments, muscles, motion of the spine and spinal cord. Because little information is available on the material properties of ligaments and the components of the vertebral column, this material is also included. A review of the experimental spinal cord injury models is given because of the concerted interest in this area today. Laboratory studies conducted in animals to develop typical spinal cord injury models and the corresponding alterations in perfusion and metabolic pathways, forces, and changes in the evoked potentials are discussed. Light and electron microscopy evaluations of the spinal cord are also treated. Clinical classifications of spinal injuries, pathology, and typical examples of upper cervical injuries, atlanto-axial disc locations and fractures, lower cervical spine injuries, injuries to thoracolumbar column with mathematical models, and typical force levels are given. The final section, investigation examples, provides a review of typical spinal injuries associated with sports injuries, motorcycle helmets, industrial helmets, and swimming pools investigated in our laboratories and by those of others. With lumped parameter mathematical model which predicts cervical compression, force, the various energies encountered in a one-dimensional impact is given. Typical examples of studies conducted on football helmets, motorcycle helmets, and industrial helmets are also included. Because of the importance of crash dummies used in the analysis of spinal injuries, a separate appendix is included, as well as an appendix reviewing motorcycle standards which are often dispersed throughout the literature. Considerable emphasis is placed upon actual experimental values of force and energy measured in the living animal and the most recent studies conducted in the fresh human cadaver to delineate the biomechanical mechanisms of spinal injury.

Accidents, Traffic↗
PubMed1983

Compression injuries of the cervical spine: a biomechanical analysis.

Three intact cadavers and 10 isolated cervical spinal columns underwent compression, with forces directed vertically, forward, or rearward. Failure modes were often different than force directions. The loads required to produce bony injury or ligamentous disruption ranged from 645 to 7439 N. Flexion and extension injuries were produced at approximately 50% of the loads required for axial compression failures. The direction of force delivery correlated only partially with the resulting pathological condition. Clinical decisions based on retrospective analysis of roentgenograms may not account for the variability of forces and the prominence of ligament injuries seen in spinal trauma. Some of the difficulties encountered in biomechanical analyses of spinal trauma are discussed.

Accidents, Traffic↗
PubMed1982

Management of odontoid fractures.

Fifty-one adults with odontoid fractures were treated between 1966 and 1979. Approximately 50% had additional trauma; over half of the patients were younger than 40 years old. Three patients presented with myelopathy: 1 was complete at C-2 and the others recovered. Cervical roentgenograms were initially considered normal in 4 patients. The fracture was through the base of the odontoid process (Type 2) in 49 patients and was into the body of C-2 (Type 3) in 2 patients. Thirty-four patients underwent early posterior cervical fusion, whereas the others were treated initially with external immobilization. Only the 2 patients with Type 3 fractures healed in Minerva casts. All 15 Type 2 fractures initially treated conservatively failed to heal and were fused. There were no age, sex, or radiological characteristics (other than fracture location) peculiar to the nonunion group. Two patients died after operation, and there was 1 minor infection in an iliac crest donor site. All patients who were operated upon demonstrated evidence of fusion within 6 weeks after operation; 16 demonstrated healing of the fracture at 6 months. After follow-up ranging from 16 months to 15 years, 7 patients complain of neck pain, of whom 6 do not require regular analgesics. Of 40 patients tested, 7 have evidence of decreased range of motion in the neck, of whom 6 have loss of less than 15% of normal motion. Traction followed by posterior cervical fusion is effective treatment for Type 2 odontoid fractures. The surgical and long term morbidity is low, and satisfactory fusion can be expected.

Adolescent↗
PubMed1980

Stereotactic aspiration of deep cerebral abscesses after CT-directed labeling.

Multiple, deep cerebral abscesses were treated in 2 patients by stereotactic aspiration after CT-guided needle labeling of single cavities. Separation of labeling from stereotactic manipulations avoids CT artifact generated by standard frame components; the technique will, therefore, accommodate most stereotactic instruments in current use. Alignment of CT and stereotactic coordinates hinged upon coidentification of the Pantopaque-labeled cavity on CT scans and on routine skull films with the stereotactic frame in place. Proximity of the label to targets eliminated the need for special head fixation or complex baseline correction.

Adult↗