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Biomedical subjects

P Bowker

Publications and source records attributed to P Bowker.

At least 19 recordsLinked to original sources
PubMed2003

Effect of foot orthoses on the kinematics and kinetics of normal walking gait.

Despite their wide clinical application and success, our understanding of the biomechanical effects of foot orthoses is relatively limited. The aim of this study was to assess the effect of medially wedged and laterally wedged foot orthoses on the kinematics and joint moments of the rearfoot complex, knee, hip and pelvis and the ground reaction forces. The principal effect of the foot orthoses was on the rearfoot complex, where significant changes in joint rotations and moments were observed. Medially wedged orthoses decreased rearfoot pronation and increased the laterally directed ground reaction force during the contact phase, suggesting reduced shock attenuation. The laterally wedged orthoses increased rearfoot pronation and decreased the laterally directed ground reaction force during the contact phase, suggesting increased shock attenuation. The effects of the orthoses on knee, hip and pelvis kinematics were generally minimal. In view of the minimal effect the orthoses had on joints proximal to the foot, it is suggested that the orthoses may have additional effects on the passive and active soft tissues of the lower limb and it is these changes that result in the documented clinical success.

Adult↗
PubMed2001

Effect of foot orthoses on rearfoot complex kinematics during walking gait.

The aim of this study was to quantify the effect of anti-pronatory and anti-supinatory foot orthoses on the angular displacement, velocity and accelerations of the rearfoot complex during gait. The transverse plane motion of the leg relative to the foot was used to indicate rearfoot complex pronation and supination. Three dimensional gait analysis on 12 subjects was used to derive the changes in the rearfoot kinematics due to the orthoses. The anti-pronatory orthoses decreased the range of pronation during the contact phase (p=0.0002) and the total range of rearfoot complex motion (p=0.000002), whereas anti-supinatory orthoses increased the range of pronation during the contact phase (p=0.00006) and the total range of rearfoot motion (p=0.049). Anti-pronatory orthoses also decreased the initial peak in pronation velocity during the contact phase of gait (p=0.006). Neither orthosis had a statistically significant effect on rearfoot complex acceleration.

Adult↗
PubMed2001

Scientific approach to the axis of rotation at the midtarsal joint.

Current biomechanical models of the midtarsal joint describe it as having two axes of rotation, the oblique and the longitudinal. The considerable freedom of movement available at the midtarsal joint means that kinematic assessment of its function and determination of its axis of rotation must be conducted under conditions that enable the joint to function as normally as possible. The assessments on which the concepts of the longitudinal and oblique axes are based do not meet this criterion. Understanding of the motions at the midtarsal joint will improve as techniques of kinematic assessment improve. Future descriptions of the midtarsal joint should adopt the standard terms applied to the other joints in the lower limb, which will facilitate the study of the midtarsal joint in relation to the function of the rest of the lower limb.

Biomechanical Phenomena↗
PubMed2000

Shank rotation: A measure of rearfoot motion during normal walking.

Motion of the shank in the transverse plane is coupled with pronation and supination of the rearfoot, and so its motion relative to the foot can be used as an indicator of the pattern of motion in the rearfoot. Compared to the more commonly used assessment of motion in the frontal plane between the heel and the shank, motion of the shank in the transverse plane relative to the foot provides a more complete measure of the pattern of motion of the rearfoot because it reflects the motion in all three joints of the rearfoot (the ankle, subtalar joint and mid-tarsal joint) not solely the ankle and subtalar components. This work aimed to provide normative data for this alternative measure of rearfoot function. Data on angular displacement, angular velocity and angular acceleration were derived from motion-analysis conducted on 25 subjects. The results suggest a difference between the pattern of angular displacement indicated when motion of the shank relative to the foot is examined and the pattern of angular displacement indicated when motion in the frontal plane between the shank and heel is examined. Specifically, the former suggests that resupination of the rearfoot after rearfoot pronation during the initial period of gait, starts at the beginning of mid-stance, while the latter suggests resupination beginning in late mid-stance. Where comparisons were possible, data on the velocity and acceleration appeared reasonable and provide further parameters with which to investigate the role of motion in the rearfoot in the development of pathologic conditions and the effects of intervention on motion in the rearfoot.

Ankle Joint↗
PubMed1999

Dimensional change in muscle as a control signal for powered upper limb prostheses: a pilot study.

The vast majority of externally powered prostheses are controlled from the myoelectric signal, measured at the skin surface using socket-located electrodes. This signal has been well researched and sophisticated signal processing methods developed. Nevertheless, the inherent properties of the signal, such as its broad bandwidth and low voltage amplitude, make its use less than straightforward in the control of low frequency activity such as powered prosthetic hand movement. This paper reports on a pilot study of an alternative, a signal derived from dimensional change in muscle. A new socket-located sensor was designed to measure dimensional change in muscle, the linearised output of which is termed the myokinemetric (MK) signal. This was used in a series of tasks aimed at investigating the potential for its use in upper-limb prosthesis control. Six amputee subjects were tested, of whom one was a regular user of the myoelectric hand, one had some experience, and four had little or no previous experience of controlling devices using their residual limb. Data is presented on the problems of shift in signal range with time and socket donning and doffing and on the ability of subjects to control the amplitude of the signal. The results show that subjects were able to control the magnitude of the MK signal to a significant degree, with typical errors averaging 0.1-0.3 mm, around 10% of the signal range. The principal problem encountered was the shift in signal with time and socket donning and doffing.

Adult↗
PubMed1997

Quantitative assessment of anterior cruciate ligament deficiency: applied load versus applied displacement.

The Salford static knee instrument (SSKI) was developed to determine the quantitative assessment of the human knee joint in vivo by utilizing the technique of applied displacement and measurement of resistive load as proposed by Butler et al. (1). The instrument was used in parallel with the device developed by Al-Turaiki (2) which utilized the opposite method of assessment. The objective of the research was to examine which of the two techniques provided the more reliable and accurate method of knee assessment. Fourteen patients with suspected isolated rupture of the anterior cruciate ligament (ACL) were subjected to anterior-posterior drawer testing on both devices. The results showed that each instrument produced results which confirmed the clinical diagnosis by indicating a significant decrease in anterior stiffness when comparing the injured and uninjured knees. [SSKI device (p = 0.000) and Al-Turaiki (2) device (p = 0.002) statistical significant difference testing with Bonferonni Alpha correction p = 0.0125]. The results showed the Salford static knee instrument indicated a 58 per cent decrease in anterior stiffness and the Al-Turaiki (2) device a 35 per cent decrease when comparing the injured and uninjured knees. In conclusion it is suggested that the application of displacement and measurement of load as proposed by Butler et al. (1) may be the most appropriate technique for precise clinical diagnosis of pathological human knee joint instability.

Adult↗
PubMed1995

Lightweight, modular knee-ankle-foot orthosis for Duchenne muscular dystrophy: design, development, and evaluation.

OBJECTIVE: The study aimed to design and construct a modular system of knee-ankle-foot orthotics (KAFOs) that could be quickly and easily assembled and provided to children with Duchenne muscular dystrophy. A pilot study would then compare the modular orthotics with the childrens' existing devices. DESIGN: Measurements from the legs of a consecutive sample of 26 Duchenne boys were taken to determine the sizing of the modular system. Nine boys with Duchenne muscular dystrophy were randomly selected to take part in a pilot study that focused on a comparison between their original and modular KAFOs of supply time, weight, energy expenditure during gait, gait speed, and ease of don/doff. SETTING: The supply and fitting of the KAFOs can be done either in the hospital, clinic, or school. PATIENTS: Boys with Duchenne muscular dystrophy, referred by the clinician for provision of KAFOs. Nine boys were approached to take part in the pilot study; all accepted. Their age range was 5 to 13 years. MAIN OUTCOME MEASURES: It is possible, by use of a modular KAFO system, to provide long leg orthoses to boys with Duchenne muscular dystrophy in approximately 1 hour. RESULTS: The pilot study also showed that the modular KAFOs provided a 23% weight saving, resulting in a 10% energy saving during ambulation and an 8% increase in walking speed. They were easier to don/doff and were preferred by all involved.

Adolescent↗
PubMed1993

Dire straits.

Orthotics, the Cinderella of the NHS, needs a radical restructuring if it is to give patients the best serviice, argue Peter Bowker and colleagues.

Administrative Personnel↗
PubMed1993

The physiological benefits of paraplegic orthotically aided walking.

A group of first-time paraplegic users of a particular ambulatory orthosis was studied to assess the physiological benefits of changing from a wholly sedentary lifestyle to one which included regular periods of upright weight-bearing and walking. Little clinically apparent benefit was noted in respiratory mechanics. There was a subjective reduction in urinary tract infections, but without a corresponding reduction in the level of bacteria. A possible improvement in bone density was noted in a small subgroup. It is concluded that, at least in the shorter term, the physiological benefits to paraplegics of using walking orthoses are not as great as has generally been claimed in the literature.

Adolescent↗
PubMed1993

A method for the kinematic evaluation of the knee following anterior cruciate ligament injury and reconstruction.

A quantitative method for assessing the kinematics of the knee in the sagittal plane has been developed in order to evaluate the role of the anterior cruciate ligament following injury and reconstruction. Measurements were made on a series of lateral radiographs obtained at different angles of flexion with the limb weight-bearing and the foot and ankle rotated so that the condyles of the femur overlapped. The kinematics of the joint were then defined by recording the path of the tip of the medial tibial spine as flexion proceeded, using a coordinate system based on the femur. This method overcomes the problems inherent in quantifying knee kinematics by using the pathway of the centre of rotation. In an amputated knee, tibial positions could be specified to within approximately 1.2 mm. There were no significant differences between results obtained at the beginning and end of a six month period for the normal knees of two patients; the standard deviation of the measured tibial positions was approximately 1.6 mm.

Anterior Cruciate Ligament↗
PubMed1992

A clinical evaluation of plaster-of-Paris and eight synthetic fracture splinting materials.

A number of new synthetic orthopaedic splinting materials, all claiming substantial advantages over the traditional plaster-of-Paris, have been introduced in recent years. However, although their properties have been extensively measured in the laboratory, little has been documented concerning their performance in clinical use. This study was therefore initiated as a comparative evaluation of the clinical characteristics and ease of use of these relatively expensive materials in the fabrication of below-knee weight-bearing casts. The study encompassed nine materials--seven based on water-activated polyurethanes, one thermoplastic and plaster-of-Paris, and involved a total of 203 patients. It was concluded that plaster-of-Paris should be used for all routine splinting applications, but that in cases in which cast weight, cast bulk, or the time to bearing weight is important, a synthetic material, chosen principally on the basis of cost, is indicated.

Adolescent↗
PubMed1992

Energetics of paraplegic walking.

A group of 35 paraplegic subjects using reciprocating walking orthoses have been examined in order to gain an insight into the potential functional benefits of using such devices. Measurements have been made of walking speeds and of the energy costs of ambulation using an established technique based on heart rate recordings. It was found that orthotically aided walking for paraplegics was slow and energy costly compared with both normal walking and wheelchair propulsion and, as it additionally requires the use of a walking aid in both hands, cannot be considered to confer the functional benefits frequently claimed for it. Nevertheless, the majority of the subjects studied liked their orthosis and did well in it, with many subjectively reporting improvements in mobility and independence.

Adolescent↗
PubMed1991

A quantitative assessment of orthoses for stabilization of the anterior cruciate ligament deficient knee.

Knee braces are used to restore functional stability to joints which have become unstable as a result of the traumatic disruption of the anterior cruciate ligament. A number of quite different designs of knee brace have evolved and are used clinically in the management of these injuries although to the authors' knowledge little quantitative data are available on their relative mechanical characteristics. This paper reports the results of static testing carried out to determine the stiffness characteristics of 24 commonly used braces. The data obtained indicated clear differences between different brace designs with the stiffest having values closely approaching that achieved physiologically in uninjured joints, and the least effective having minimal stiffnesses. It was found that the mechanical performance of any individual brace was determined by three factors: the mechanical characteristics of the individual components from which it was constructed, the structural integrity of its design, and the interaction of the brace with the limb during loading.

Anterior Cruciate Ligament↗
PubMed1989

Effects of ambulation on the blood flow in paralysed limbs.

Non-invasive transcutaneous blood gas monitoring techniques have been used as indicators of the effect of standing exercise on circulation in paraplegic subjects. Oxygen (tPO2) and carbon dioxide (tPCO2) electrodes were positioned on the chests and legs of a group of normal control subjects and a group of paraplegic subjects in both rested sitting and post-ambulatory standing. It has been shown that, with one possible exception, there is no significant difference in the transcutaneous blood gas partial pressures of O2 and CO2, and thus, by inference, in the circulation of paraplegics when either sitting or standing.

Adolescent↗
PubMed1989

Classification of tachykinin receptors in muscularis mucosae of opossum oesophagus.

1. Muscularis mucosae of the distal oesophagus of the opossum contracts in response to substance P and to a variety of tachykinins. To delineate the nature of the receptors present in this tissue, we evaluated contractile responses to substance P, neurokinin A, neurokinin B, eledoisin and analogues believed to be highly selective for NK-1, NK-2 and NK-3 receptors. In addition, the effects of prolonged exposure to each of these agents (10(-6) M or 10(-5) M) on contractile responses to substance P and to itself were evaluated. Similarly effects of prolonged exposure to the various tachykinins and their analogues on the field-stimulated responses of this muscle were studied. 2. All naturally occurring tachykinins were full agonists and differed in potency (comparing ED50 values) by less than ten fold. In nearly all cases there was cross tachyphylaxis between substance P and the other tachykinins and each reduced tonic responses to field stimulation, a response previously shown to be mediated by a substance P like agent. Eledoisin failed to cause tachyphylaxis under the conditions of these experiments. 3. When highly selective tachykinin analogues were used, only that believed to activate NK-1 receptors was a full agonist. [beta-Ala4,Sar9,MetO2(11)]SP(4-11) was also only slightly less potent than substance P. In contrast, an agonist selective for NK-2 (NK-A) receptors, [Nle10]NKA(4-10), and one selective for NK-3 (NK-B) receptors, [beta-Asp4, MePhe7]NKB(4-10) were unable to produce a response equal to 50% of the maximum even at 10(-5) M. However, all three selective tachykinin analogues reduced responses to substance P but not to carbachol. They usually reduced both phasic and tonic responses to field stimulation. 4. We conclude, based on this and earlier study, that the tachykinin receptors of opossum oesophagus muscularis mucosae recognize all naturally occurring tachykinins but may represent only NK-1 receptors. The ability of analogues selective for other types of tachykinin receptors to reduce responses to substance P raises the possibility that their selectivity depends in part on diminished efficacy rather than totally on diminished affinity at some classes of receptor.

Animals↗