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Biomedical subjects

D J Pratt

Publications and source records attributed to D J Pratt.

At least 19 recordsLinked to original sources
PubMed2000

Dynamic foot orthoses. Principles and application.

Previous research has identified areas under the foot where stimulation evokes specific tonic reflexes. The term "tonic" is used because these reflex movements occur slowly, as if tonus or tension were accumulating, in contrast to the abrupt phasic response of a tendon jerk. The concept of tonic reactions has now been incorporated into the design of dynamic foot orthoses to help provide improved orthotic treatment with a better functional outcome. This article describes the background of this technique, briefly describes the manufacture of the dynamic orthosis, and outlines some of its uses.

Equipment Design↗
PubMed1996

Soft-tissue balance and recovery of proprioception after total knee replacement.

Decreasing proprioception of the knee is multifactorial and is a function of age and degenerative joint disease. Soft-tissue release during total knee replacement may have an influence. We have quantified soft-tissue imbalance at the time of knee replacement and attempted to eliminate it at full extension, using established methods. We studied the influence of residual soft-tissue imbalance on postoperative proprioception, assessing this in 38 patients before total knee replacement and at three and six months postoperatively. We found that proprioception improved in varus knees at three and six months after soft-tissue balancing procedures. Knees balanced in full extension and in flexion (< +/- 2 degrees) showed a significant improvement in proprioception (p < 0.0005) whereas those which were not balanced in flexion but fully balanced in extension had no significant improvement. We conclude that soft-tissue balance in both flexion and extension is important to allow satisfactory postoperative proprioception of the knee.

Arthritis↗
PubMed1995

British standard (BS) 5750--quality assurance?

BS5750 is the British Standard on "Quality Systems". Its equivalent in European Standards is EN29000 and in the International Standards Organisation ISO9000. This paper points out that these standards lay down formalised procedures and require documentation but do not ipso facto lead to quality assurance. The author points to the Japanese post-war industrial success as being an example of Total Quality Management within the framework provided by the philosophy of Dr. W. Edwards Deming (1988 and 1993). This philosophy on the management of "systems" to provide high quality products and services is briefly outlined. The author argues that improvement in prosthetic and orthotic services will not be reached through implementation of BS5750 but rather through radical rethinking and the adoption and application of the Deming philosophy.

England↗
PubMed1994

Some aspects of modern orthotics.

Orthotics is changing more rapidly than ever before, largely resulting from improved understanding of the human requirements and the current state of technological abilities. Walking is always seen as a basic requirement for normal activity and as such it is in this area that most research and development effort is expended. This paper outlines some of the current developments in this interesting topic and includes seating and posture as these are often viewed as precursors to successful standing and then, possibly, gait.

Humans↗
PubMed1990

Long term comparison of some shock attenuating insoles.

The effect of one years general use on the performance of four shock attenuating insoles is reported. Testing was carried out using the JP Biomechanics Shock Meter on twelve volunteers on a timed oval course at eight intervals during the year. The results show that two of the insoles perform well (Viscolas and PPT) although deterioration does occur after 6-9 months use; the other two insoles (Plastazote and Gait Aid) perform poorly. It is suggested that manufacturers provide some information to the user or supplier regarding the effective life of their products.

Adult↗
PubMed1988

Medium term comparison of shock attenuating insoles using a spectral analysis technique.

In view of the current interest in skeletal shock and the damage it could cause, this paper illustrates the value of a new device for measuring shock transients reliably during gait. Four orthotic insoles were tested (Viscolas, PPT, Plastazote and Gait Aid) during walking on a timed oval course at intervals during 1 month using the J.P. Biomechanics Shock Meter. The 'shock factor' for each insole was recorded and the data show that Viscolas and Gait Aid do not appear to deteriorate in use whereas PPT and Plastazote do. Viscolas and PPT perform well; Viscolas is just superior; Plastazote (after 2 days) and Gait Aid both perform poorly. It is suggested that manufacturers should acknowledge the effect of use on the insole properties because this information is of paramount interest to the users of their products.

Adult↗
PubMed1987

The effects of medullary reaming on the torsional strength of the femur.

The authors have investigated the effect on the torsional strength of the bone of reaming the medulla of the femur from 12 to 16 mm in steps of 1 mm. Five groups of femurs, with 10 pairs in each, were tested comparatively in torsional loading and the torque required to cause fracture and the angle through which the bone had twisted at fracture were directly recorded for each pair. The results of maximum torque at failure (expressed as a proportion of the same parameter for the unreamed femur) plotted against the ratio of bone shaft diameter to reamed diameter showed a good correlation. The proportional maximum torque was found to range from 0.63 (at 12 mm) to 0.36 (at 16 mm) with a sharp transition between 14 and 15 mm. This drastic reduction was felt to be important for both the surgeon and the patient.

Biomechanical Phenomena↗
PubMed1987

Derby intramedullary nail: further biomechanical comparison.

This paper is the second part of a study into the mechanical effectiveness of a new intramedullary femoral nail (the Derby nail). The results of three point bending tests have shown that the Derby nail is stronger and stiffer than both the K and Zickel nails and offers advantages over the AO plate, despite the latter's higher load carrying ability when used on the compressively loaded bone face. Previous work by the authors has shown the Derby nail to be superior in torsional loading and it is felt that this intramedullary device offers sound clinical advantages over the other designs, this being confirmed by extensive clinical trials.

Biomechanical Phenomena↗
PubMed1986

Assessment of some shock absorbing insoles.

Due to the increase in prescription of insoles to relieve symptoms due to skeletal shocks at heel strike a pilot study was initiated to look at some materials used for this purpose. Five materials were examined (Plastazote, Spenco, Sorbothane, Poron (PPT) and Viscolas) by two methods. The first method used an accelerometer mounted between the teeth of one of the authors (PR) to record skeletal shock. The second method used a force plate to record the shock produced by dropping a ball-bearing onto the insoles from a standard height. The results showed that Plastazote is poor at absorbing shock with Spenco and Sorbothane being quite good. The best insole materials tested were Poron (PPT) and Viscolas with the latter being marginally superior. No account was taken of degradation of the materials in use except that Plastazote worn for 72 hours was also used in the study, this producing the worst results.

Evaluation Studies as Topic↗
PubMed1985

Energy of gait in below-knee casts with different soles.

This study aims to provide some guidelines for the use of soles on below-knee walking casts. Whole-body energy changes during the single limb support phase of the gait cycle have been quantified in twenty volunteer subjects fitted with below-knee casts and each wearing one of five soles in turn. Simple gait analysis was carried out with a Kistler force plate and an Apple II microcomputer, the data were sampled at 50 Hz. Three commercial soles and two 'home made' ones were used; it was generally found that the commercial products produced a more energy efficient gait. Some recommendations are included regarding the design of soles to be used in this clinically demanding situation.

Adult↗
PubMed1985

Derby intramedullary nail--a biomechanical comparison.

This paper describes the design and function of the Derby intramedullary nail and its biomechanical testing, comparing it with the K nail and reamed unfractured femurs. The Derby nail is designed to transmit torsional loads and apply compression to the fracture site using a sliding proximal collar and distal extendable 'wings'. Femurs fixed with Derby, K and Zickel nails and AO plates were tested in torsion and the rotation and torsional load at failure recorded and compared with unfractured control femurs. The results show that the strength of the Derby nail in torsion is approximately equal to 4 times and the energy to failure 2.3 times that of the K nail.

Biomechanical Phenomena↗
PubMed1984

Water fittings as sources of Legionella pneumophila in a hospital plumbing system.

An extensive study of the plumbing systems in Kingston Hospital was made over the three years following the 1980 outbreak of legionnaires' disease. The introduction of chlorination and raising the water temperature controlled the outbreak but failed to decontaminate water outlets in the wards. Legionella pneumophila was isolated from rubber washers in shower fittings, and laboratory experiments demonstrated the ability of L pneumophila to grow in water in contact with these rubber components. All the components in the hospital's fittings were replaced with an approved type, and since then L pneumophila has not been isolated from water or components.

Chlorine↗
PubMed1984

RTV silicone insoles.

A cheap and fast method of providing long term accommodating insoles is described. Room temperature vulcanizing (RTV) silicone rubber is used, with suitable coverings, to provide pain relief and support for feet and ankles. The combination of physical properties of the finished item provides a useful balance between support and flexibility which results in these insoles being readily accepted by the patients.

Equipment Design↗
PubMed1981

A biomechanical study of cast-brace treatment of femoral shaft fractures.

The off-loading characteristics of the cast-braces of 30 patients with fractures of the shaft of the femur have been investigated, during axial loading, using strain-gauge transducers. These were applied at the level of the fracture, where the cast was circumferentially split, and to the hinges of the brace at the knee. They measured the load transferred between the two portions of the thigh cast, and between the thigh cast as a whole and the below-knee cast; by subtraction from the total load on the limb, the skeletal force at the fracture level and at the knee could be calculated. In all patients there was an increase in the fracture load as union progressed which was thought to be due to physiological feedback mechanism from the fracture site. The load carried by the two portions of the thigh cast and by the thigh cast as a whole was proportionately high at first and stabilised at an average of 35 per cent of body weight.

Adolescent↗