PubMed Health⌕ Search

Biomedical subjects

R Whitehill

Publications and source records attributed to R Whitehill.

45 records · Page 3Linked to original sources
PubMed1978

Arterial hypertension induced by femoral lengthening. A canine model.

In a canine experimental model, femora were lengthened 2.5 to 3.0 centimeters over a one-minute period. Systolic blood-pressure elevation averaged forty millimeters of mercury and diastolic blood-pressure elevation, twenty-two millimeters of mercury. The average peak arterial pressure was 193/115 millimeters of mercury. The effects of sympatholytic agents on the experimental model were tested. Alpha-adrenergic blockade by phenoxybenzamine, total-body catecholamine depletion by reserpine, and sympathetic ganglionic blockade by trimethaphan camphorsulfonate all inhibited the rise in arterial pressure, but beta-adrenergic blockade by propranolol did not. A differential spinal anesthetic with Xylocaine solution dramatically decreased the elevation in arterial pressure.

Anesthesia, Spinal↗
PubMed1977

Evaluation of the painful hip by aspiration and arthrography.

The preoperative or postoperative painful hip can present a difficult diagnostic problem. In a series of 46 aspirations on such hips, one instance of Staphylococcus aureus, three instances of Staphylococcus albus, one instance of Escherichia coli and one instance of tuberculous infections were diagnosed. In addition, in a series of 22 fluoroscopically controlled arthrograms performed on patients with painful total hip replacements, six instances of loose acetabular components and one instance of a broken femoral stem were found.

Biopsy, Needle↗
PubMedDate not supplied

Spinal evoked potentials from the cervical spine.

Spinal cord evoked potentials were recorded from spinous processes of the lumbar, thoracic, and cervical levels of the spinal column of normal cats in response to direct stimulation of the sciatic nerve and subcutaneous stimulation of the posterior tibial nerve. The typical primary response was altered by changes in location, magnitude, and frequency of the stimulation. Further changes in the primary response could be associated with spinal level of observation. Reduction in amplitude and decrease in signal complexity with increasing frequency of stimulus indicated the loss of the slower components of the primary response of average evoked potentials. Sharp reduction of signal amplitude and increase in latency was evident as the recording moved from L1 to C3 and C2.

Animals↗
PubMedDate not supplied

A biomechanical analysis of posterior cervical fusions using polymethylmethacrylate as an instantaneous fusion mass.

Three posterior fusion reconstruction procedures for a canine experimental model of the C4-C5 bilateral facet dislocation are herein mechanically tested. The two procedures utilizing polymethylmethacrylate have increased angular stiffness as compared with the normal posterior soft tissue structures and the reconstruction procedure utilizing wire alone. Their ultimate moments are not significantly greater. These findings lead us to predict an increased incidence of fixation failure when polymethylmethacrylate acrylic cement preparations are used for instantaneous posterior "fusions" as compared with the more traditional wire and bone graft procedure.

Animals↗
PubMedDate not supplied

The evolution of stability in cervical spinal constructs using either autogenous bone graft or methylmethacrylate cement. A follow-up report on a canine in vivo model.

Thirty-six adult mongrel dogs underwent either a posterior C4-C5 bone graft or methylmethacrylate-cerclage wire construction procedure to simulate the analogous human stabilization procedures. The dogs were divided into groups of six and allowed to live 1, 2, or 3 months after surgery. At the appropriate time they were killed and their C4-C5 spinal segments excised and studied radiologically, mechanically, and histologically. In addition, the C4-C5 spinal segments from 15 other mongrel dogs were excised and either left intact as normal (five) or prepared as one of the two constructs (five each) described above. They were also tested mechanically to provide immediate postoperative stability data. At some time during the first postoperative month the methylmethacrylate constructs lost mechanical stability. In addition, fibrous tissue was noted to have grown between the posterior laminal surface and the cement mass during this same time. Radiologically, loosening was obvious by the second postoperative month. The bone graft constructs were mechanically equivalent to or superior to the normal dogs by the second postoperative month. Likewise, they were well on their way to solid fusion radiologically and histologically by the same time. Impressed by the rapidity of deterioration in mechanical stability for the methylmethacrylate constructs, the authors further questioned their usefulness in cases of traumatic cervical spinal instability. The bone graft constructs continued to appear to be a reliable way to achieve ultimate spinal stability.

Animals↗
PubMedDate not supplied

Posterior strut fusions to enhance immediate postoperative cervical stability.

UNLABELLED: In an attempt to enhance the immediate stability of posterior interspinous fusion constructs, the authors conducted the following project. Twenty-four adult mongrel dogs underwent a posterior C4-C5 fusion using iliac crest autogenous graft and internal fixation using either ulna struts (12) or metallic struts (12) fixed into position by sublaminar wires. Half of the animals were killed at either 1 week or 3 months postoperatively, and their C4-C5 motion segments were excised and studied radiologically, mechanically, and histologically. Both fusions created immediate and 3-month stability equivalent or superior to normal C4-C5 canine spinal segments. However, three dogs were rendered completely and two dogs incompletely quadriplegic by the surgery. CLINICAL RELEVANCE: Because of the relatively high rate of neurologic injury associated with these procedures in normal dogs, the authors hesitate to endorse their use in all but complete quadriplegic patients.

Animals↗
PubMedDate not supplied

Posterior cervical fusions using cerclage wires, methylmethacrylate cement and autogenous bone graft. An experimental study of a canine model.

UNLABELLED: Forty-eight adult mongrel dogs underwent posterior exposure of C4-C5, fixation of the two posterior spinous processes together with a no. 20-gauge cerclage wire, posterior element decortication, wound irrigation and the following: bone fusions (application of a standard volume of iliac crest autograft), polymethylmethacrylate (PMMA) fusions (application of a standard volume of methylmethacrylate cement), Combination 1 fusions (application of one-half the volume of graft used in the bone fusions, over the facet joints. Methylmethacrylate cement was pressed into position centrally to surround the posterior spinous processes and cerclage wire), Combination 2 fusions (application of the same volume of graft used in the bone fusions, over the facet joints. Methylmethacrylate cement was applied as in the Combination 1 fusions). For each preparation, six animals survived 2 weeks or 3 months. All had monthly lateral cervical radiographs. At the appropriate times, they were killed and their C4-C5 segments excised and studied mechanically and histologically. At 2 weeks all of the above preparations were mechanically inferior to normal C4-C5 segments in respect to at least one of the parameters studied. At 3 months, the bone fusions and both combination fusions had developed sufficient mechanical stability so that they were equivalent to normal segments. At this time, the PMMA fusions remained inferior to the "normals." The mechanical data for the PMMA and both combination fusions was corroborated by the histology which demonstrated a fibrosynovial layer between the cement masses and underlying posterior element bone. In the 3-month combination fusions, the lateral aspects of the posterior elements had been spanned by a fusion mass. CLINICAL RELEVANCE: Previously, the authors defined some of the problems associated with constructs modeled by their PMMA fusions. This work confirms the previous research. It also demonstrates that ultimate spinal stability is produced by combination constructs. Because of the 2-week mechanical data, it is recommended that when combination constructs are used clinically, the patient's neck be protected by an external orthosis in the early postoperative period.

Animals↗
PubMedDate not supplied

The treatment of fracture dislocations of the thoracolumbar spine with halofemoral traction and Harrington rod instrumentation.

Although function does not return after complete spinal cord injuries, partial recovery is possible after incomplete lesions Halofemoral traction may produce early decompression of injured neural elements in the spinal canal by anatomic realignment of the spinal column. It also acts to stabilize the very unstable thoracolumbar fracture dislocation and prevent displacement as well as further neurologic trauma. The body jacket is easy to make and apply. It allows early mobilization of patients when utilized in conjunction with the posterior spinal fusion and Harrington rod fixation.

Adolescent↗