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Edward C. Benzel, Kevin M. Sittig and Mansour Mirfakhraee

✓ Nineteen patients underwent a total of 21 stump angioplasty procedures for an occluded internal carotid artery. Indications for surgery included the preparation of the donor vessel for a subsequent extracranial-intracranial bypass procedure, the occurrence of emboli to the intracranial vasculature from the external carotid artery circulation, and the association with symptomatic occlusive disease of the external carotid artery accompanying occlusion of the ipsilateral internal carotid artery.

The technique utilized and the results obtained in these 19 patients are presented. In select patients, the removal of an occluded internal carotid artery stump via a stump angioplasty is beneficial in preventing the catastrophic sequela of embolic cerebrovascular disease.

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Edward C. Benzel, Theresa A. Hadden and Carla M. Saulsbery

✓ The motion at each intervertebral level permitted by the halo jacket and the thermoplastic Minerva body jacket was compared in 10 ambulatory patients with an unstable cervical spine. The thermoplastic Minerva body jacket is a new lightweight modification of a Minerva jacket which is fabricated from Polyform (a splinting material made of a polyester polycaprolactone) and Polycushion (a closed-cell foam for padding). Each patient served as his/her own control. The average movement from flexion to extension at each intervertebral level was significantly less in the thermoplastic Minerva body jacket (2.3° ± 1.7°) than in the halo jacket (3.7° ± 3.1°) (p < 0.0025). This difference is attributable to the “snaking phenomenon” encountered with halo jacket immobilization and should be taken into account when considering an external splint for an unstable cervical spine. The thermoplastic Minerva body jacket also offered a substantial improvement in comfort for the patient over that experienced in the halo jacket. The apparent advantage with respect to stability and comfort of the thermoplastic Minerva body jacket over the halo jacket suggests that the former device is the orthosis of choice for ambulatory stabilization of most patients with an unstable posttraumatic cervical spine injury.

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Edward C. Benzel and Lee Kesterson

✓ A technique of posterior cervical interspinous compression wiring and fusion, which offers significant immediate stability, is presented. Its efficacy in 50 consecutive cases illustrates its utility. The technique involves the passage of an interspinous cerclage wire. Rather than placement of onlay laminar and facet grafts, a split-thickness tricortical iliac-crest graft is compressed against the involved medial laminae and spinous processes bilaterally. These grafts are held in place by a compression wire, which encircles the grafts and thus sandwiches the spinous processes between them. This virtually ensures subsequent bone fusion and offers substantial acute stability. The compression wire offers an added advantage of encircling the cerclage wire, thus pulling it dorsally. This significantly diminishes translational mobility at the unstable segment. It also minimizes hyperextension at the unstable segment via medial compression of the grafts into the interspinous space.

The fusion of a minimal number of spinal segments is emphasized. This substantially diminishes the chance of flexible kyphosis and degenerative changes, both above and below the fusion site. A three- or four-level fusion was performed in only 11 patients. The remaining 39 patients underwent two-level fusion. A solid bone fusion was achieved in all cases, with a follow-up period of at least 6 months. In one patient, the spinous process fractured, necessitating an anterior fusion procedure. The technique presented here appears to acutely offer a very stable construct and, in addition, is a simple and straightforward procedure for the treatment of the unstable cervical spine.

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Edward C. Benzel, Charles D. Gross, Theresa A. Hadden, Lee Kesterson and Michael D. Landreneau

✓ By conventional criteria, an apneic patient's PaCO2 must be greater than 60 mm Hg before apnea can be attributed to brain death. The rate of a PaCO2 increase in the apneic patient traditionally has been thought to be in the range of 3 mm Hg/min. In order to assess the validity of these data and the validity of the “apnea test” for determination of brain death, the results of this test were reviewed in 20 patients. In all patients, arterial blood samples were drawn for blood gas measurements every 2 minutes following the cessation of volume ventilation (with an oxygen cannula at 6 liters O2/min passed into the tracheobronchial tree).

The rate of PaCO2 increase was noted to be very erratic. The average rate of rise was 3.7 ± 2.3 mm Hg/min (± standard deviation). This, however, varied from 0.5 to 10.5 mm Hg/min and was not predictable from the variables evaluated. The rate of PaCO2 increase was noted to decline throughout the duration of the test. This ranged from 3.9 ± 1.2 mm Hg/min (for patients with baseline PaCO2 ≤ 30 mm Hg) and 4.5 ± 1.9 mm Hg/min (for patients with baseline PaCO2 ≥ 30 mm Hg) in the first 4 minutes of the test to an average of 0.92 mm Hg/min for patients with test lasted longer than 12 minutes. These unpredictable results might be related to CO2 washout, atelectasis, cardiac ventilations, or other yet-undefined parameters.

The nonlinear relationship between rate of PaCO2 increase and time following onset of apnea resulted in the test being prolonged in several patients. In these patients, the PaCO2 approached 60 mm Hg in an asymptotic fashion. These lengthy tests could have been avoided by utilizing a standardized apnea test with a baseline PaCO2 of 40 mm Hg or greater.

The observation that a high baseline PaCO2 greatly augments the efficiency and safety of the test allows criteria that have previously been based on conjecture to be documented and applied clinically. A standardized apnea test, utilizing these principles, may satisfy many of the criticisms regarding brain-death testing that have been raised by neurologists, neurosurgeons, and transplant surgeons.

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Edward C. Benzel

✓ A three-quarter prone position for the lateral extracavitary operative approach to the thoracic and lumbar spine is described. This approach has been used in 40 patients with anterior spinal cord compressive lesions in the thoracic and/or lumbar region. In this patient population, it has allowed a safe ventral decompression of the spinal cord. It also allows placement of spinal instrumentation through the same incision. Both the operating surgeon and the assistant have an excellent view of the operative site, including the dural sac. Patient positioning and the operative approach are described and illustrated.

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Edward C. Benzel, Lee Kesterson and Erich P. Marchand

✓ The authors present their experience with 28 patients who had incurred unstable thoracic or lumbar spine fractures and who were intraoperatively stabilized with the Texas Scottish Rite Hospital (TSRH) universal instrumentation system. These patients were treated over a 1-year period and reflect an evolving insight into the treatment of thoracic and lumbar spine trauma with universal instrumentation. The TSRH instrumentation system appears equivalent to the more established Cotrel-Dubousset system in most respects.

The construct design of the TSRH system facilitates the safe application of a rigid spinal implant. No cases of instability or pseudoarthrosis were observed during an average follow-up period of 9 months, (minimum 3 months). As the surgical treatment plan evolved, shorter and more compact constructs were increasingly utilized. There were no cases of instrumentation failure, regardless of the number of spinal levels fused or the number of levels instrumented. The value of using short rods when possible is emphasized: they may decrease the incidence of delayed instability and discomfort related to loosening at the hook/bone interface compared to that observed when long-rod systems are used in association with short spine fusions causing a fusion/instrumentation mismatch.

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Edward C. Benzel, Jay P. Mashburn, Steven Conrad and Denise Modling

✓ The absence of spontaneous respirations at a PaCO2 of 60 mm Hg or above has traditionally been accepted as the respiratory criteria for the determination of brain death. The testing of patients for the presence or absence of apnea has been complicated because the rate of PaCO2 elevation may vary substantially from patient to patient, and a nonlinear relationship exists between the rate of PaCO2 increase and the duration of apnea.

In an attempt to refine the apnea test and to further elucidate the physiology of hypercapnia in humans, 11 patients who met all but the respiratory criteria for brain death were evaluated using a modification of a previously utilized apnea testing protocol. All patients were brought to a PaCO2 of 40 mm Hg or above prior to the apnea test. Baseline PaCO2 ranged from 40 to 45 mm Hg in six patients (Group I) and from 46 to 51 mm Hg in five patients (Group II). The mean rate of PaCO2 increase was 5.1 ± 1.4 mm Hg/min in Group I and 6.7 ± 3.1 mm Hg/min in Group II. No problems with cardiovascular instability or hypoxia were encountered during testing in this series. This refinement of the apnea test allows for a streamlined and safe approach to brain death detection.