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Biomedical subjects

Michael Y Wang

Publications and source records attributed to Michael Y Wang.

7 recordsLinked to original sources
PubMed2003

Intradural spinal arachnoid cysts in adults.

BACKGROUND: Idiopathic arachnoid cysts are rare lesions not associated with trauma or other inflammatory insults. To date, there have been few large series describing the presentation and management of these lesions. METHODS: Twenty-one cases of intradural spinal arachnoid cysts were identified (1994-2001). Pediatric patients and cases with antecedent trauma were excluded. There were eight women and 13 men with an average age of 52 years. Follow-up averaged 17 months. RESULTS: Cysts were most commonly found in the thoracic spine (81%). Fifteen cysts were dorsal to the spinal cord and six were ventral to the spinal cord. All patients underwent laminectomy with cyst fenestration and radical cyst wall resection. Based upon intraoperative ultrasonography, four cysts were also shunted to the subarachnoid space, and seven patients had an expansile duraplasty with freeze-dried dural allograft. Of the seven patients with syringomyelia, three resolved with extramedullary cyst resection alone. Four required syrinx to subarachnoid shunting. Follow-up MRI demonstrated cyst resolution in all cases. All seven intramedullary syrinxes were decreased in size and four resolved completely. Weakness (100%), hyperreflexia (91%), and incontinence (80%) were more likely to improve than neuropathic pain (44%) and numbness (33%). One patient had increased numbness postoperatively. CONCLUSIONS: Ventral cysts are more likely to cause weakness and myelopathic signs. Preoperative symptoms of neuropathic pain and numbness are less likely to improve than weakness and myelopathy. Utilizing intraoperative ultrasound to guide aggressive surgical treatment with the adjuncts of shunting and duraplasty results in a high rate of cyst and syrinx obliteration.

Adolescent↗
PubMed2003

Minimally invasive lateral mass screws in the treatment of cervical facet dislocations: technical note.

OBJECTIVE: The technique of lateral mass screw and rod or plate fixation is a major advancement in the posterior instrumentation of the cervical spine. This technique provides rigid three-dimensional fixation, restores the dorsal tension band, and provides highly effective stabilization in patients with many types of traumatic injuries. METHODS: Patient 1 was a 32-year-old man who had been in a motor vehicle accident. He presented with right C5 radiculopathy. X-ray findings included 45% anterolisthesis of C4 on C5, bilateral facet disruption, and right unilateral C4-C5 facet fracture and dislocation. The patient was placed in Gardner-Wells tongs, and the fracture was reduced with 25 pounds of traction. Patient 2 was a 56-year-old woman who had been in a motor vehicle accident that resulted in complete quadriplegia. Her initial imaging studies revealed a C3-C4 right unilateral facet fracture with subluxation. She was placed in traction, and her neurological status was reassessed. The findings of her neurological examination revealed improvement: she was found to have Brown-Séquard syndrome. Patient 3 was a 33-year-old man who was involved in a diving accident that resulted in bilaterally jumped facets at C3-C4. The patient was neurologically intact, and attempts at closed reduction were not successful. RESULTS: Patients 1 and 2 underwent anterior cervical discectomy with iliac crest autograft fusion and plating. They were then placed in the prone position, and a dilator tubular retractor system was used to access the facet joint at the level of interest. The facet joints were then denuded and packed with autograft. Lateral mass screws were then placed by means of the Magerl technique, and a rod was used to connect the top-loading screws. Patient 3 underwent posterior surgery that included only removal of the superior facet, intraoperative reduction, and bilateral lateral mass screw and rod placement. CONCLUSION: This technical note describes the successful placement of lateral mass screw and rod constructs with the use of a minimally invasive approach by means of a tubular dilator retractor system. This approach preserves the integrity of the muscles and ligaments that maintain the posterior tension band of the cervical spine.

Adult↗
PubMed2003

Minimally invasive cervical expansile laminoplasty: an initial cadaveric study.

OBJECTIVE: Expansile laminoplasty has been successfully used to treat cervical myelopathy attributable to canal stenosis. However, detachment of the posterior cervical muscles is thought to contribute to postoperative axial neck pain and kyphosis. Minimizing the amount of muscular dissection might reduce the likelihood of these sequelae. METHODS: Six human cadaveric spines were used to assess the feasibility of a minimally invasive laminoplasty technique. A 22-mm tubular dilator port was used to access the lamina-facet junctions from C2 to C7, through bilateral stab incisions at C4-C5 and C5-C6. Troughs at the lamina-facet junctions were drilled bilaterally, and the contiguous laminae were lifted en bloc from one side. Ten-millimeter rib allograft spacers were inserted to maintain a gap on the open side. RESULTS: Exposure of six cervical levels was easily accomplished with two small incisions on each side. Drilling was achieved without dural violations. The midsagittal spinal canal diameter was increased by a mean of 38% and the spinal canal area was increased by an average of 43% at the level of C5. CONCLUSION: A minimally invasive approach for cervical laminoplasty could be performed in human cadavers. The measured increases in spinal canal space approximated those demonstrated to be associated with stabilization or improvement of neurological status.

Bone Transplantation↗
PubMed2003

Adjacent segment disease: an uncommon complication after cervical expansile laminoplasty: case report.

OBJECTIVE AND IMPORTANCE: Adjacent segment disc disease is a well-described phenomenon that occurs after anterior cervical spinal fusion. One of the advantages of cervical laminoplasty over anterior approaches is that although the treated segments are stiffened, no formal fusion is performed. This is thought to reduce the biomechanical stresses placed on adjacent levels and thus decrease the likelihood of adjacent level degeneration. CLINICAL PRESENTATION: A 62-year-old man presented with myelopathy attributable to cervical spondylosis and underwent a C3-C7 laminoplasty. Improvements in gait were followed 2 years later by symptomatic disc degeneration and spinal cord compression at T1-T2, which rendered him wheelchair bound. INTERVENTION: The patient was treated with a laminectomy at the level of stenosis accompanied by posterior instrumentation and fusion from C5 to T3. This resulted in clinical improvement, and the patient was returned to his baseline ambulatory status. CONCLUSION: Adjacent segment disease is an uncommon complication that occurs after laminoplasty. Careful attention to preserving facet joint motion in the cervical spine may minimize the stresses placed on adjacent motion segments.

Cervical Vertebrae↗
PubMed2002

Polylactic acid mesh reconstruction of the anterior iliac crest after bone harvesting reduces early postoperative pain after anterior cervical fusion surgery.

OBJECTIVE: Autologous iliac crest bone enhances the rate of spinal arthrodesis. However, graft site complications are common, with donor site pain being particularly troublesome. Reconstruction of the hip defect with an absorbable polylactic acid mesh to restore the bony cortical contour has been proposed to reduce hip pain. METHODS: Thirty-nine consecutive patients treated by a single senior surgeon (BAG) during a 14-month period were studied. All patients had cervical spondylosis treated through an anterior approach supplemented with an autologous hip graft. Patients with preexisting hip pain were excluded. Pain was rated on a scale of 1 to 10 at 1 week and 3 months after surgery via a questionnaire. Postoperative pain medication regimens were standardized. RESULTS: Thirty patients were available for follow-up, 15 with mesh implantation and 15 without. Hip pain in the mesh-treated group averaged 4.7 and 1.6 at 1 week and 3 months, respectively. Hip pain in the standard-treatment group averaged 6.9 and 2.5 at 1 week and 3 months, respectively. These differences were statistically significant (P = 0.004 at 1 wk and 0.055 at 3 mo). Hospital length of stay was shorter in the mesh-treated group (2.1 versus 3.2 d, respectively), but this difference was not statistically significant. Two patients without mesh treatment complained of the cosmetic defect resulting from absent bone, and three had temporary difficulty with hip eversion or flexion. Two patients in the mesh-treated group developed seromas, which were treated conservatively. CONCLUSION: Reconstruction of the iliac crest reduces early postoperative pain. Other potential benefits may include shorter hospitalizations and a reduced incidence of hip weakness; however, careful attention to wound closure is necessary to prevent seroma formation.

Cervical Vertebrae↗
PubMed2002

Brain death documentation: analysis and issues.

OBJECTIVE: Specific guidelines for documenting the complete loss of brain function, for the declaration of brain death, have been established for 3 decades. This study assessed the quality and completeness of brain death notes and the effects of delays between notes on organ procurement. METHODS: A retrospective review of brain death declarations at a major medical center was performed. Fifty-eight cases, with a total of 121 brain death notes, were identified in a 12-month period. Notes were assessed for clinical and confirmatory tests of brain and brainstem function. Adverse physiological events that occurred in the time intervals between notes were also identified. RESULTS: The clinical tests most likely to be documented were tests of pupillary (86%) and gag (78%) reflexes. Corneal reflexes were tested in only 57% of cases, and motor responses were noted in only 66%. Documentation by the neurosurgery department was generally more complete. The delays between brain death declarations were highly variable but did not result in any loss of donor organs because of hemodynamic derangements. CONCLUSION: To meet the needs of organ recipients and donor families and to comply with hospital, legal, and legislative mandates, hospitals may need to increase quality assurance activities with respect to declarations of brain death. Increased physician education should improve awareness of uniform brain death declaration guidelines.

Adolescent↗