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Biomedical subjects

R G Ellenbogen

Publications and source records attributed to R G Ellenbogen.

29 records · Page 2Linked to original sources
PubMed1998

Revision pedicle screws. Bigger, longer shims--what is best?

STUDY DESIGN: To evaluate the effect of change in screw dimensions and hole augmentation in pedicle screw revisions, the insertional torque was determined, and results were compared with those in control specimens in an in vitro study using cadaveric thoracolumbar spines. OBJECTIVES: To determine the best method of salvage for failed pedicle screws, by evaluating the insertional torque after placing a larger diameter or longer screw into a stripped hole. Use of a shim and use of larger and longer screws were also investigated. Finally, the effect on insertional torque of simply removing and replacing a pedicle screw in its original hole was investigated. SUMMARY OF BACKGROUND DATA: The effects of using bigger or longer screws and shims to salvage failed pedicles have been studied. The interaction between how much larger, how much longer, and inserting with or without shims, has not been well studied. Optimizing reinsertional torque through the use of bigger screws risks exceeding the pedicle capacity. Using longer screws risks violation of the anterior vertebral body, thereby placing the great vessels and viscera at risk. By knowing the relative contribution of increase in length and diameter, the surgeon can optimize the risk-benefit ratio. METHODS: Eight cadaveric spines from T10 to S1 were harvested. The specimens underwent radiographic screening and bone densitometry. A modified Latin square randomization was designed to evaluate the screw diameters and lengths. Each pedicle was its own control. A 35- x 6.5-mm screw was used as a control. Test screws were placed after pedicle screw hole failure was achieved and documented by stripping. For the test screws, the diameters were increased by 1 mm and 2 mm, the lengths were increased by 5 mm and 10 mm. Shims were added randomly. The peak insertional torque was measured for each control screw and test screw placement. In addition, during each screw placement, the screw was removed and replaced to determine the effect. RESULTS: Insertional torque, after the pedicle screw is removed and replaced in the same hole, was decreased by 34% (P < 0.000005). Increasing the diameter of the salvage screw by 2 mm caused the insertional torque to be increased by 8.4% of the original. Increasing the length of the screw did not improve the salvage screw insertional torque. There was an interaction effect for the 1-mm increase in diameter and the increase in length. At this diameter, increasing the length had a significant effect (P = 0.009) on the salvage torque. Using a shim created no improvement in salvage insertional torque (P = 0.77). There was a poor linear correlation between torque and bone mineral density (r = 0.18) in these osteoporotic specimens. CONCLUSIONS: Removing and replacing a pedicle screw in its original hole substantially decreases its mechanical fixation. For pedicle salvage, increasing the diameter causes the greatest restoration of strength. Shims had no effect in pedicle salvage in osteoporotic specimens.

Absorptiometry, Photon↗
PubMed1997

Endoscopic management of a pineal and suprasellar germinoma with associated hydrocephalus: technical case report.

A patient with a synchronous pineal and suprasellar germinoma and symptomatic hydrocephalus underwent a minimally invasive endoscopic biopsy and third ventriculostomy. We performed multiple biopsies of both tumors and fenestration of the floor of the third ventricle with a flexible fiberoptic endoscope through a single burr hole. Postoperative quantitative cine-mode magnetic resonance imaging (MRI) confirmed the patency of the fenestration. Selected pineal/posterior third ventricle region tumors, especially radiosensitive germinomas, could be treated with this approach thereby obviating the need for either stereotactic or craniotomy/open biopsy and the subsequent placement of a permanent cerebrospinal fluid (CSF) shunt. The endoscopic approach to tumors in the pineal/posterior third ventricle region provides an accurate straightforward, and safe method of obtaining a diagnosis and treating the associated increased intracranial pressure.

Adult↗
PubMed1997

Detection of titanium in human tissues after craniofacial surgery.

Generally, titanium fixation plates are not removed after osteosynthesis, because they have high biocompatability and high corrosion resistance characteristics. Experiments with laboratory animals, and limited studies of analyses of human tissues, have reported evidence of titanium release into local and distant tissues. This study summarizes our results of the analysis of soft tissues for titanium in four patients with titanium microfixation plates. Energy dispersive x-ray analysis, scanning electron microscopy, and electrothermal atomic absorption spectrophotometry were used to detect trace amounts of titanium in surrounding soft tissues. A single metal inclusion was detected by scanning electron microscopy and energy dispersive x-ray analysis in one patient, whereas, electrothermal atomic absorption spectrophotometry analyses revealed titanium present in three of four specimens in levels ranging from 7.92 to 31.8 micrograms/gm of dry tissue. Results from this study revealed trace amounts of titanium in tissues surrounding craniofacial plates. At the atomic level, electrothermal atomic absorption spectrophotometry appears to be a sensitive tool to quantitatively detect ultra-trace amounts of metal in human tissue.

Biocompatible Materials↗
PubMed1994

Quantitative cine-mode magnetic resonance imaging of Chiari I malformations: an analysis of cerebrospinal fluid dynamics.

Quantitative cine-mode magnetic resonance imaging of the craniocervical junction was performed in 17 patients with a Chiari I malformation to evaluate cerebrospinal fluid (CSF) dynamics, including 8 patients who underwent surgery. The cine-mode magnetic resonance images of these patients were compared with those of 12 normal pediatric and adult subjects. The craniocervical junction was imaged by 16 cardiac-gated velocity-encoded images arranged in a cine loop. These images allowed the measurement of both the magnitude and direction of CSF velocity. Velocity measurements were made in four regions of interest--the foramen Magendie, the foramen magnum, and ventral and dorsal to the spinal cord at C2--and were plotted in relation to the cardiac cycle to produce a CSF velocity profile. All patients who underwent surgery had the same procedure: a posterior fossa craniectomy with C1 laminectomy, lysis of arachnoid adhesions, and duraplasty. Normal subjects had unobstructed flow around the craniocervical junction: a short period of cranial CSF flow was followed by a sustained period of caudal CSF flow. Patients with tonsillar herniation of more than 5 mm had obstructed CSF flow, decreased CSF velocity, and shorter periods of caudal CSF flow. These patients also had preferential cranial CSF flow as compared with the controls. Postoperatively, there was a substantial increase in both the velocity of CSF flow and in the period of caudal CSF flow in the foramen magnum. The postoperative changes mirrored the velocity profiles of the normal subjects. These changes in CSF velocity and direction correlated with a more normal-appearing foramen magnum, a reduction in syrinx size, and an improvement in symptoms.

Adolescent↗
PubMed1991

Transfalcine approach to a callosomarginal artery aneurysm.

We describe a transfalcine approach to clipping and subsequently excising an expanding mycotic callosomarginal aneurysm. The patient had a devastating dominant (left) hemispheric spontaneous intracranial hemorrhage and was neurologically improving at the time of surgery nearly 2 months later. To avoid retracting the left hemisphere, we approached this left callosomarginal aneurysm from the nondominant side through the falx. The approach was straight-forward, and the result was satisfactory.

Adult↗
PubMed1991

Cervical spondylotic myelopathy: treatment with posterior decompression and Luque rectangle bone fusion.

Cervical spondylotic myelopathy appears to result from a combination of factors. The two major components are 1) compressive forces resulting from narrowing of the spinal canal, and 2) dynamic forces owing to mobility of the cervical spine. There is substantial evidence to suggest that the repetitive trauma to the spinal cord that is sustained with movement in a spondylotic canal may be a major cause of progressive myelopathy. Utilization of extensive anterior procedures that remove the diseased ventral features as well as eliminate the dynamic forces owing to the accompanying fusion have grown in popularity. Cervical laminectomy enlarges the spinal canal, but does not reduce the dynamic forces affecting the spinal cord, and may actually increase cervical mobility, leading to a perpetuation of the myelopathy. The authors propose the combination of posterior decompression and Luque rectangle bone fusion to deal with both the compressive and the dynamic factors that lead to cervical spondylotic myelopathy. Ten patients who had advanced myelopathy underwent the combined procedures. Nine of the 10 experienced significant neurological improvement, and the 10th has had no progression. The combination of posterior decompression and Luque rectangle bone fusion may offer a simple, safe, and effective alternative treatment for cervical spondylotic myelopathy.

Adult↗
PubMed1990

Precocious puberty following head injury. Case report.

A 6-year-old girl developed secondary sexual characteristics 5 months after severe closed head injury. Endocrinological tests confirmed a pubertal sexual condition; there was also diminution of serum melatonin and disruption of the diurnal pattern. Magnetic resonance imaging demonstrated focal hypothalamic injury; this is believed to be the first time such a posttraumatic lesion has been demonstrated by imaging techniques. The pathophysiology of this condition is discussed.

Brain Stem↗
PubMed1989

Tumors of the choroid plexus in children.

Primary neoplasms of the choroid plexus in children are surgically treatable, and the encouraging results of surgical removal, even for carcinoma, justify an aggressive surgical approach. Forty cases operated on over a span of 45 years have been reviewed in detail, including a rereading of all microscopic slides. The prognosis for children with papilloma has been excellent. The 5-year survival rate for children with carcinoma of the choroid plexus was 50%, and all deaths occurred within 7 months of operation. The patients whose carcinomas were totally removed had a better prognosis than did those with subtotal removal.

Adolescent↗
PubMed1988

Group B streptococcal infections of the central nervous system in infants with myelomeningocele.

Three cases of group B streptococcal infection of the central nervous system (CNS) occurred among 147 neonates treated for myelomeningocele at The Children's Hospital in Boston from 1970 to 1985. This pathogen was responsible for one third of the nine CNS infections noted in these patients over the 15-year study period. All three children with group B streptococcal CNS infections subsequently required multiple CNS shunting procedures and prolonged hospitalizations. Two children suffered major neurological sequelae. In neonates with myelomeningocele, group B streptococci have direct access to the CNS, perhaps explaining the high incidence of serious meningitis and ventriculitis in this population. Antibiotic prophylaxis for early myelomeningocele repair should be adjusted accordingly.

Central Nervous System Diseases↗
PubMedDate not supplied

Occult intraspinal anomalies in congenital scoliosis.

Thirty consecutive patients with congenital spinal deformity underwent magnetic resonance imaging (MRI) to determine the incidence of occult intraspinal anomaly. These congenital spinal deformities included 29 cases of congenital scoliosis and one case of congenital kyphosis. Physical examination findings and plain radiographs were reviewed in an attempt to correlate these findings with subsequent intraspinal pathology. Nine patients had intraspinal anomalies identified on MRI consisting of five with tethered cord, four with syringomyelia, three with lipoma, and one with diastematomyelia. One patient required surgery for diastematomyelia; another underwent release of his tethered cord. Only one patient, with diastematomyelia associated with a syrinx and bifocal tethering, had his anomaly suggested by physical examination and plain radiographs. Two other patients had findings on plain radiographs previously associated with high prevalence of occult intraspinal anomalies; one patient with congenital kyphosis had a tethered cord, and one patient with a unilateral hemivertebrae associated with a contralateral bar had a tethered cord. Two of nine patients with occult intraspinal anomalies required surgery for their anomaly. In patients with a congenital spinal deformity, we found nine (30%) of 30 to have an associated anomaly within the spinal canal. Only three of these nine had plain radiographs and physical examination findings suggestive of their subsequent MRI findings. Given the poor correlation between findings on physical examination, plain radiographs, and subsequent occult intraspinal anomalies on MRI, we believe that MRI is helpful in evaluating patients with congenital spinal anomalies.

Adolescent↗