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Biomedical subjects

J H Calhoun

Publications and source records attributed to J H Calhoun.

12 recordsLinked to original sources
PubMed1992

Infection in the diabetic foot.

A 56-year-old woman presented with a chronic infection of her right first toe. The woman had a 15-year history of diabetes mellitus and had been insulin dependent for the past five years. Her toe had been injured one month earlier when hit by a frozen chicken that fell out of the freezer. The accident caused a bruise and a small cut. Serous to purulent drainage then developed. When she presented, the toe was reddened and draining. Physical examination showed a nonobese woman with no fever or other evidence of systemic infection. The wound showed no evidence of necrotizing fasciitis. Peripheral pulses were 2+ and capillary refill was slow. Sensation in both feet was decreased. The transcutaneous oxygen tension in the feet was reduced at 20 mm Hg. Relevant laboratory findings included a serum glucose of 250 and creatinine of 1.5. X-rays of the foot were compatible with diffuse osteomyelitis of the distal phalanx of the great toe. Technetium and indium scans were positive, with increased uptake localized to the area of x-ray changes (Figure 1). The patient was admitted to the hospital.

Adult↗
PubMed1992

Rigidity of half-pins for the Ilizarov external fixator.

The success of the Ilizarov technique is due to the combination of the biomechanics of its external fixator and the biology of distraction osteogenesis. The stability and stiffness of the conventional Ilizarov fixator is attributed to its use of a K-wire cross structure. The disadvantages of this structure include pain, and possible neurologic and vascular injuries when the wires are introduced into crucial neurovascular areas, as well as increased frame complexity and construction. Reducing the number of wires decreases these problems, but also decreases the stiffness of the system. Hybrid (wire and half-pins) Ilizarov fixators and half-pin fixators are also being used in an attempt to alleviate these problems. Half-pins have been described by Fleming et al. and Green as causing minimal transfixation of the surrounding soft tissues and capable of and being inserted into anatomically safe areas. The stiffnesses of the hybrid systems have not been measured. This study reports on the stiffness of different wire and half-pin systems that were biomechanically tested in axial loading, anterior-posterior bending, medial-lateral bending, and torsional loading. The results demonstrated that the conventional Ilizarov fixator with wires possesses a high axial stiffness, whereas the fixator with half-pins possesses higher stiffness under bending and torsional loads. To obtain adequate stability, the use of hybrid Ilizarov frames with one wire and two or more half-pins (5 or 6 mm in diameter), or larger half-pin frames (5 or 6 mm) with three pins is recommended.

Biomechanical Phenomena↗
PubMed1992

Techniques for the management of burn contractures with the Ilizarov Fixator.

The Ilizarov fixator was used to correct chronic burn deformities of the foot and ankle. These contractures can be classified as "simple" or "complex" based on associated deformities and musculoskeletal function. The simple, undirectional deformities of equinus, cavus, rockerbottom, and toe dislocations are fairly easy to correct and maintain. Correction and maintenance of complex deformities with varus or valgus angulation, bone abnormality, or muscle loss are more difficult.

Burns↗
PubMed1992

Biomechanics of the Ilizarov fixator for fracture fixation.

Compression, distraction, and torsion stiffness of the Ilizarov external fixator was measured in two fracture models in autopsy specimens of tibia and fibula. A transverse model was tested in six frame constructions with the osteotomy site preloaded in four different positions. An oblique model was tested in four frame constructions also with four preloaded positions. Stiffness was more dependent on bone preload than wire number, wire type, or frame design. High stiffness was achieved by bone preloading, by compressing the rings together, by increasing the number of wires, and by using olive wires. The stiffness can be decreased (dynamization) by separating the rings and by removing wires. This data is helpful for frame design of the Ilizarov fixator.

Biomechanical Phenomena↗
PubMed1991

The Ilizarov technique in the treatment of osteomyelitis.

Seventy-five patients with bone infection have been treated at The University of Texas Medical Branch at Galveston (UTMB) with the Ilizarov external fixator. Multiple deformities were present in many patients. Thirty-four patients had infected nonunions, 22 were short, 18 were angulated, 15 needed joint fusions, 12 had open fractures, 10 had segmental defects, 5 had knee problems and equinus deformities, 4 had rotational problems, 2 had hip problems, and 1 had a translational problem. The average number of deformities per patient was 1.71. Problems with the device include length of therapy (6.8 months average time in device), pin tract infection (superficial, 41.3%; deep, 2.7%), pain (narcotic use, 2.7 months average), and device adjustment. Successful results were obtained in a high percentage of cases. The infection was arrested in 92.0% of the patients and the deformities were corrected in 85.1%. We found that the Ilizarov fixator was effective in the reconstruction of difficult deformities that result from osteomyelitis.

Adult↗
PubMed1991

Does hyperbaric oxygen have a place in the treatment of osteomyelitis?

There are several specific mechanisms by which HBO restores normal cellular processes that are compromised by hypoxia, or by which HBO augments bactericidal events. All of these are potentially applicable to, and beneficial for, the osteomyelitis patient. At the University of Texas Medical Branch, we find that early osteomyelitis is usually amenable to appropriate medical and surgical therapy. Adjunctive HBO is generally reserved for treatment of advanced stages of osteomyelitis (3B and 4B). In addition, HBO is occasionally used when patient circumstances dictate suppression of osteomyelitis rather than definitive treatment. Our clinical impression is that HBO has a beneficial effect on treatment outcome in these selected patients. Fault-free clinical studies are difficult to perform in this complex and varied patient population. Several studies have suggested a beneficial effect with the addition of adjunctive hyperbaric oxygen to usual osteomyelitis treatment regimens, whereas other clinical studies have failed to demonstrate such a benefit. No study has shown any harmful effect of adjunctive HBO on the outcome of osteomyelitis treatment. We hope that clinical researchers will continue to address this question, despite the research design problems inherent in the osteomyelitis population.

Clinical Trials as Topic↗
PubMed1990

Signs distinguishing spasmus nutans (with and without central nervous system lesions) from infantile nystagmus.

Clinical findings as well as eye and head movement recordings were analyzed from 23 patients with spasmus nutans without central nervous system (CNS) changes, 10 patients with spasmus nutans-like disease (head nodding, intermittent nystagmus associated with intracranial anomalies or visual pathway disorders), and 25 patients with infantile nystagmus. Ten diagnostic signs were established to differentiate between the patient groups. Although they were helpful in separating patients with infantile nystagmus from those with spasmus nutans, no difference was found between the patients with spasmus nutans with and without CNS lesions. This study indicates that eye and head movement recordings do not allow differentiation between benign spasmus nutans and spasmus nutans-like disease. The differentiation must be made on the basis of neuroimaging.

Child↗
PubMed1990

Hyperbaric oxygen as adjunctive therapy for osteomyelitis.

Mechanistically, hyperbaric oxygen (HBO) appears useful for the treatment of osteomyelitis. HBO increases the oxygen tension in infected tissue, including bone. An adequate oxygen tension is necessary for oxygen-dependent killing of organisms by the polymorphonuclear leukocytes and for fibroblast activity leading to angiogenesis and wound healing. HBO has a direct bacteriocidal or bacteriostatic effect on anaerobic organisms. In addition, HBO augments the killing of Pseudomonas aeruginosa by the aminoglycoside--tobramycin. At the University of Texas Medical Branch at Galveston, adjunctive HBO is used for the Cierny Mader stage 3B and 4B osteomyelitis.

Animals↗
PubMed1977

Cutting-aspiration instruments.

Cutting-aspiration instruments are discussed in relation to design and principles of action. Experience with the Roto-extractor in over 100 cases is reviewed. Large pupillary openings were achieved in nearly all cases. No vitreous was attached to the wound postoperatively. Retinal detachment has not occurred to date in nontraumatic lenticular opacities.

Adolescent↗
PubMed1975

The roto-extractor in pediatric ophthalmology.

The Roto-Extractor, designed by Nicholas Douvas, M.D., was used by the authors in 66 eyes for cataracts, secondary membranes, and persistent hyperplastic primary vitreous. The average age of the patients with congenital cataracts was 2.4 years, for traumatic cataracts 16.4 years. The pupil wal cleared well in 63 of these eyes. There was no vitreous to the wound in any of the eyes. Unplanned iridectomies and prolonged inflammation were the major complications.

Adolescent↗
PubMedDate not supplied

A new rationale for the management of large angle esotropia.

It is not only possible but safe to exceed the traditional 5 mm maximum recession of each medial rectus muscle to correct large angle esotropia. It is possible to grade the amount of recession to the preoperative deviation, similar to that which is done for esotropia less than 35 prism diopters. The results of this series indicate that alignment to within 10 prism diopters with one procedure is more likely by large recessions of the medial rectus than by other approaches. If a reoperation is necessary, there still remain two other untouched horizontal muscles on which to operate.

Child↗