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Biomedical subjects

K T Foley

Publications and source records attributed to K T Foley.

29 records · Page 2Linked to original sources
PubMed1996

Image-guided spine surgery.

Conventional imaging techniques are of limited usefulness in spinal navigation, due to their lack of a "three-dimensional perspective." An interactive image-guided approach has been developed that provides a three-dimensional image-space representation of surgical space, using a specially designed referencing system and computer workstation. The system is described and results from laboratory tests and clinical cases are reported. It is concluded that interactive image-guided stereotaxis can be a valuable tool in spinal localization because of its degree of precision and the increased margin of safety it can offer.

Bone Screws↗
PubMed1995

Cannulated screws for odontoid screw fixation and atlantoaxial transarticular screw fixation. Technical note.

Cannulated screw systems use thin Kirschner wires (K-wires) that have been drilled into the bone to direct screw trajectories accurately into small bone fragments. Use of the K-wires avoids overdrilling the pilot holes and allows fixation of adjacent bone fragments during screw insertion. Hollow tools and hollow screws are inserted into the bone over the K-wires. Cannulated screw fixation is useful in the cervical spine to stabilize odontoid fractures and to treat atlantoaxial instability. This report describes techniques for successful cannulated screw insertion and methods to minimize complications. Cannulated screws have several distinct advantages compared to noncannulated screws: 1) the K-wires guide the screw position into the bone; 2) the K-wire trajectory can be repositioned easily if the original trajectory was not ideal; 3) the K-wires allow continuous fixation of adjacent unstable bone fragments; and 4) the K-wires prevent migration of unstable bone fragments during screw insertion. Complications associated with the K-wire (breakage, repositioning, and advancement) can be minimized using precise operative techniques, a specialized tool system, and intraoperative fluoroscopic monitoring. A unique cannulated screw tool system was developed specifically for upper cervical fixation to allow percutaneous drilling using long tunneling devices, tissue sheaths, drill guides, and long K-wires. These tools allow delivery of cannulated fracture-fixation screws at a low angle to the spine through long soft-tissue trajectories. Cannulated screws have significant advantages compared to noncannulated screws for fixation of the unstable cervical spine.

Bone Screws↗
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

Pulmonary embolism from a venous thrombosis distal to the popliteal vein.

A case of pulmonary embolism from a venous thrombosis distal to the popliteal vein is reported. This occurred despite venographic and ultrasound verification that the thrombus had not extended to the popliteal vein. The medical literature supports expectant treatment of "calf-only" venous thrombi. Our case clearly demonstrates that clinically significant pulmonary emboli can arise from calf vein thrombi without popliteal involvement.

Adult↗
PubMed1990

Receptor interactions in modulating ventilatory activity.

The ventilatory control system utilizes a variety of sensory receptor groups, including chemoreceptors and mechanoreceptors, to provide feedback concerning the status of controlled variables. Most ventilatory responses to altered receptor inputs generally involve a complex interaction between several receptor groups, central integrative mechanisms, and other modulatory inputs (e.g., "state," hormonal, or neurotransmitter status). Because the control system is complex, nonlinear, and dynamic, the ultimate ventilatory response elicited by a given stimulus is not easy to predict based on the reflex effects of individual receptor groups studied in isolation. A full understanding of the role that sensory receptors play in ventilatory control requires information concerning interactions among receptor groups and with other elements of the control system. The complexity of the problem and the lack of a uniform definition of the term "interaction" has hindered research in this area. An interaction is defined as a nonadditive relationship between independent inputs to the system. Within this definition, five domains of interaction are described. 1) Algebraic interactions occur in ventilation and/or its components because of their multiplicative and nonlinear relationship. 2) Closed-loop interactions occur because of the prevalence of feedback loops within the respiratory control system. 3) Neural interactions reflect central nervous system integration of simultaneous receptor inputs and are demonstrated when feedback loops are opened. Three subdomains of neural interactions are defined: modulatory, dynamic, and range-specific neural interactions. 4) Mechanical interactions result from nonlinear transformations of motoneuron output into mechanical actions. 5) Adaptive interactions occur when paired receptor or modulatory inputs alter future responses. To understand the role of any sensory receptor group in ventilatory control, it is necessary to define its interactions with other control system elements in each of these domains. Understanding the mechanisms of these interactions requires detailed information about the physical system subserving ventilatory control (mechanics and gas exchange) and the relevant properties of the neural network coordinating their actions.

Adaptation, Physiological↗
PubMed1989

Progression of hydrocephalus during corticosteroid therapy for neurosarcoidosis.

We describe a patient with sarcoid meningitis and hydrocephalus who improved rapidly after initiation of oral prednisone therapy, but who later decompensated acutely and required an emergency ventriculoperitoneal shunt. Hydrocephalus associated with neurosarcoidosis may progress despite steroid treatment, even when symptoms have improved. If hydrocephalus associated with neurosarcoidosis is treated with corticosteroids and without a shunt procedure we suggest that the corticosteroids should be continued at high doses for a prolonged period.

Adult↗
PubMed1989

A comparison of the effects of suxamethonium, atracurium and vecuronium on intracranial haemodynamics in swine.

Sixteen Yorkshire swine weighing 15-20 kg were studied to compare the effects of suxamethonium, atracurium and vecuronium on intracranial pressure (ICP), heart rate (HR), arterial blood pressure (BP), and cerebral perfusion pressure (CPP) in swine with normal or elevated ICP. In each animal an intracranial pressure-volume curve was produced by the inflation of an epidural balloon. The baseline ICP (Po), the ICP at the inflection point (Pi) and on the steep portion (Pmax) of the pressure-volume curve were identified and the balloon volumes recorded. The animals were assigned to receive either suxamethonium 1.0 mg/kg, atracurium 0.6 mg/kg, vecuronium 0.2 mg/kg, or saline placebo intravenously at three conditions: First, with the epidural balloon deflated Po, next at Pi, then at Pmax. Neither atracurium, vecuronium, nor placebo produced any statistically significant effect on HR, BP, ICP, or CPP at any baseline level of ICP. Suxamethonium produced an early fall in ICP (0.8 +/- 0.3, 2.6 +/- 1.0 and 3.5 +/- 1.3 mmHg at Po, Pi and Pmax respectively: P = .0005) followed by a rapid rise above the pre-infusion level (1.8 +/- 0.6, 2.8 +/- 0.6 mmHg, and 2.2 +/- 0.5 mmHg at Po, Pi and Pmax respectively: P = .0005). A fall in BP coupled with the rise in ICP resulted in a fall in CPP (5.8 +/- 2.3, 6.1 +/- 1.2, and 6.3 +/- 1.8 mmHg at Po, Pi and Pmax respectively: P = .0005). Although the fall in CPP was not large, in the presence of elevated ICP, where CPP already is marginal, such a decrease may compromise cerebral blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Intraoperative angiography using a portable digital subtraction unit. Technical note.

A portable digital subtraction unit has been used in the operating room as an important improvement in obtaining high-quality intraoperative angiograms. This digital subtraction system offers several advantages over previously described techniques for intraoperative studies. Not only are the images of good quality, but also the dose of contrast medium is reduced and a real-time imaging capability allows the surgeon to visualize the passage of contrast agent dynamically. Arterial injections may be performed by selective femoral cerebral catheterization, puncture of the cervical carotid artery, retrograde catheterization via the superficial temporal artery, or puncture of an intracranial vessel at the time of surgery.

Cerebral Angiography↗
PubMed1980

Selective management of extracranial carotid arterial aneurysms.

Aneurysms of the extracranial carotid arteries are rare vascular lesions that produce a high incidence of unfavorable neurologic sequelae. In the past 24 years, 19 patients at UCLA Hospital were treated for angiographically demonstrable extracranial carotid arterial aneurysms. These cases were reviewed to determine the natural history of these lesions as influenced by various modes of therapy in order to develop a logical treatment plan for these difficult patients. Because of the varied location of these lesions, proper treatment requires a diversity of techniques. Gratifying results can be achieved when a carefully selected operative approach is undertaken.

Adult↗