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Biomedical subjects

J L Cunningham

Publications and source records attributed to J L Cunningham.

At least 19 recordsLinked to original sources
PubMed1992

Glove wearing in Northern Ireland and an assessment of the loss of tactile perception.

The increased awareness of the need for cross-infection control in dentistry has led to recommendations that operating gloves be worn routinely by dental surgeons. A survey conducted amongst general dental practitioners in Northern Ireland showed a drop in glove wearing from 100% in the newly qualified to 47% in those who had qualified between 15 to 35 years ago. A frequently stated reason for the non wearing of gloves in this group is the diminution of tactile sense. To test this, a blind tutor was engaged to read a random standard length Braille passage whilst wearing selected gloves and the reading time recorded and compared with ungloved reading. The wearing of gloves increased reading time and, by implication, the loss of tactile perception, by between 14% and 37%, depending on the glove used. The thickness and stiffness of the gloves were also determined and the results suggest a relationship between these quantities and the loss of tactile perception.

General Practice, Dental↗
PubMed1991

Sorption determination of hollow VLC resin obturators.

Visible light cured (VLC) resin can be used to produce hollow dental obturators but the quantity of water absorbed by this material, in comparison to heat cured acrylic, as reported in previous studies, may make the appliance unhygienic. A model was designed to compare sorption and permeability. It was found that the VLC resin had a lower sorption value than heat cured acrylic, making it a more suitable material for producing hollow obturators.

Acrylic Resins↗
PubMed1991

Axial movement and tibial fractures. A controlled randomised trial of treatment.

Diaphyseal fractures of the tibia in 80 patients were treated by external skeletal fixation using a unilateral frame, either in a fixed mode or in a mode which allowed the application of a small amount of predominantly axial micromovement. Patients were allocated to each regime by random selection. Fracture healing was assessed clinically, radiologically and by measurement of the mechanical stiffness of the fracture. Both clinical and mechanical healing were enhanced in the group subjected to micromovement, compared to those treated with frames in a fixed mode possessing an overall stiffness similar to that of others in common clinical use. The differences in healing time were statistically significant and independently related to the treatment method. There was no difference in complication rates between treatment groups.

Adolescent↗
PubMed1990

Design and testing of external fixator bone screws.

In external fixation, bone screw loosening still presents a major clinical problem. For this study, the design factors influencing the mechanics of the bone-screw interface were analysed and various experimental screws designed with the intention of maximizing the strength and stiffness of the inserted screw. Push-in, pull-out and bending tests were then carried out on the three experimental screws, and on two commercially available screws in both a synthetic material and in cadaveric bone; photoelastic tests on different screw threadforms were also performed. The results of the push-in and pull-out tests indicate that both the screw threadform and cutting head have a significant effect on the holding strength of the screw. The photoelastic tests show that most of the applied load is distributed over the first few threads closest to the load, and that the area between the thread crests is subjected to high shear stresses.

Biomechanical Phenomena↗
PubMed1990

Response of the growth plate to distraction close to skeletal maturity. Is fracture necessary?

Axial force applied during epiphyseal distraction has been measured close to skeletal maturity in patients having leg lengthening, in a rabbit model, and in vitro from an amputation specimen. In the patient study, both slow distraction rates and low constant distraction loads were applied. For all the distraction regimens, it was not possible to lengthen the limb significantly without evidence of fracture as demonstrated by a sudden decrease in distraction force. Growth plate failure was observed from 600 to 800 N, these levels being lower than those recorded from the in vitro tests. In the animal study, three distraction regimens (0.13, 0.26, and 0.53 mm/day) were applied across the upper tibial growth plate of New Zealand white rabbits close to skeletal maturity. Distraction was applied and force measured using a strain-gauge dual-frame external fixator. The force-time results revealed two distinct patterns. One pattern, in which the forces rapidly increased to maximum values of approximately 25 N and then suddenly decreased, indicated fracture of the growth plate, which was confirmed histologically. In the other pattern, forces increased steadily throughout distraction, reaching maximum values at the end of distraction of approximately 16 N. Histologic observations indicated hyperplasia of the growth plate without fracture, however, only a small increase in limb length was detectable. Hence, if a significant increase in leg length is required close to skeletal maturity, then fracture of the growth plate must occur.

Adolescent↗
PubMed1989

Measurement of fracture movement in patients treated with unilateral external skeletal fixation.

Axial movement occurring at the fracture site has been determined in a group of healing tibial fractures treated by external skeletal fixation. Fracture movement was determined via a strain gauge transducer which was attached to the column of the external fixator and measured the deflection of the bone screw adjacent to the fracture site and the active loading or weight bearing given by the patient to the fractured limb was monitored using a force platform. The results for 27 subjects show that, with a rigid unilateral fixator, the axial movement occurring at the fracture site was initially small (mean = 0.28 mm at 5 weeks post fracture). This movement increases to reach a mean maximum value of 0.43 mm at 11 weeks post-fracture and then decreases, despite increased weight bearing, as fracture healing progresses. In the early stages of healing, the movement can be increased slightly if the fixator is fitted with a module which permits additional fracture site movement, although the resultant increase in movement is only a small proportion of the potential available with this module.

Bone Screws↗
PubMed1989

The differentiation of loose and secure femoral implants in total hip replacement using a vibrational technique: an anatomical and pilot clinical study.

ANATOMICAL STUDY: The common pathway to failure in total hip replacements is loosening of the acetabular and femoral components. The reliable diagnosis of this loosening is difficult. A non-invasive technique has been developed which analyses a vibration signal transmitted through the femur. This can distinguish between a femoral component which is loose and one which is firmly fixed. Charnley femoral components were cemented securely into ten cadaver femurs and the transmitted vibration signal recorded. The prostheses were then loosened first at the cement-prosthesis and then at the cement-bone interface. The tests were then repeated. Consistent and distinct differences between output vibration signals were observed between the firmly implanted and the loss prostheses. PILOT CLINICAL STUDY: Seven patients admitted for revision surgery because of clinical and radiological evidence of femoral implant loosening were tested using this technique. A further four patients with secure femoral components were tested approximately two weeks after total hip replacement. The differences in output signal, which had been observed between firmly implanted and loose prostheses during the anatomical study, were again demonstrated.

Adult↗
PubMed1989

Distraction physiolysis in the rabbit.

Axial forces across the growth plate of the upper tibia during controlled distraction were studied in 24 rabbits close to skeletal maturity. Distraction rates of 0.13, 0.26, and 0.53 mm every 24 hours were applied through a dual-frame external fixator. Strain gauges were bonded to the fixator, and axial forces were estimated prior to and following distraction. The results demonstrate two distinct patterns. In one group, forces increased to maximum values of 20-32 newtons and then suddenly decreased on subsequent distraction. This force pattern indicated fracture of the growth plate with associated hyperplasia. In the other group, lower maximum forces of 6-18 newtons were produced at the end of the distraction period, which were associated with physeal hyperplasia without fracture. These results showed that response to controlled distraction was dependent upon both the level of force acting across the growth plate and the rate of distraction; hyperplasia was achieved with lower rates of distraction up to a critical peak force above which fracture occurred.

Animals↗
PubMed1989

A mechanical assessment of applied compression and healing in knee arthrodesis.

The applied compression and stiffness of a knee arthrodesis treated with unilateral external fixation can be mechanically assessed. Of ten patients in whom arthrodesis bending stiffness measurements were obtained during healing, nine had a minimum bending stiffness of 5 Nm/degree and sound clinical fusion. In seven of these nine patients, a bending stiffness of at least 10 Nm/degree was obtained, suggesting that this stiffness value is a safe and reliable indicator for successful arthrodesis. Arthrodesis compression declined rapidly; daily adjustments were required to maintain a compression of 500 Newtons. A small but significant loss of length was associated with this high value of compression. On reduction of the compression to 200 Newtons, the rate of decrease of compression and the loss of length across the arthrodesis were simultaneously reduced.

Arthrodesis↗
PubMed1988

Design and performance of a fracture monitoring transducer.

The answer to the question, 'when is a fracture healed?' is not simple, since the healing process is progressive and it is not possible to specify a time when the fracture can be said to have healed. In the past the assessment of fracture healing has, in the main, been subjective, relying upon the skill of the interpreter. A more objective method would be an advantage for many reasons, and since the bone is intended to be load bearing it is reasonable to assess healing by measuring the mechanical integrity of the bone. To do this a 'clamp on' transducer has been developed which, when fitted to the support column of an external fixator, enables the stiffness of a fracture to be determined during the healing process. Over the past 6 years this system has been used for both clinical and research work. It has enabled various forms of treatment to be evaluated in terms of 'rate of healing' and it also indicates the safe point at which the fixator can be removed.

Biomechanical Phenomena↗
PubMed1988

Critical care orientation: a comparison of two teaching methods.

The purpose of this study was to determine differences in knowledge, performance, and study time between critical care orientees after use of two types of teaching methods: lecture and self-directed learning package. This study had a nonequivalent control group design. The sample consisted of 24 nurse orientees employed in critical care areas of a large teaching hospital on the Eastern Seaboard. Group A (n = 13) used a self-directed learning package and group B (n = 11) attended a lecture. Data were collected during an 8-week orientation. During week 2 the knowledge pretest was administered, the demographic data questionnaire was completed, and group A was given the self-directed learning package. During week 6 group A completed the self-directed learning package and group B attended the lecture. During week 8 the knowledge and performance simulation posttests were administered, and the study time questionnaire was completed. A paired t test revealed a difference in pretest and posttest knowledge in all participants, t (23) = 6.6, p less than 0.001, indicating that learning occurred among all participants. ANCOVA showed no significant differences between groups in knowledge and performance. A t test showed no significant differences in total study time between the two groups. Group A reported significantly (p less than 0.001) greater at-home study time than group B. Results of this study indicate that nurse orientees' knowledge and performance may be similar with the use of either lecture or self-directed learning package.

Critical Care↗
PubMed1986

Haemochromatosis presenting with a double Yersinia infection.

A patient suffering from diabetes mellitus presented with Yersinia pseudotuberculosis septicaemia and serological evidence of concomitant infection with Yersinia enterocolitica. He was later shown to have idiopathic haemochromatosis.

Antibodies, Bacterial↗
PubMed1974

Acetanilide oxidation in phenylbutazone-associated hypoplastic anaemia.

Acetanilide like phenylbutazone is paraoxidized by the liver endoplasmic reticulum as a primary biotransformation step. Both compounds were given at different times to each of 10 healthy volunteer subjects and the plasma disappearances measured. Correlation was shown between plasma clearance values of the two compounds (r = + 0.7067; P < 0.05).Eight patients with hypoplastic anaemia after phenylbutazone therapy were investigated. Plasma clearance values and half lives of acetanilide were measured in this group of patients and compared with those of a group of 30 healthy volunteer controls. There was a significant decrease in clearance (P < 0.01) and lengthening of half lives (P < 0.001 in the patients with phenylbutazone-associated hypoplasia. Five patients with idiopathic aplastic anaemia-that is, without history of antecedent phenylbutazone ingestion-were similarly investigated with acetanilide and there was no significant difference between the results in these patients and those in the control group.It is suggested that relatively poor paraoxidation of phenylbutazone producing high blood concentrations on a given dose may be a factor responsible for the drug-associated hypoplasia even though it does not explain the similar pattern of adverse reactions reported in association with oral administration of the metabolite oxyphenbutazone.

Acetanilides↗