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P J Kyberd

Publications and source records attributed to P J Kyberd.

13 recordsLinked to original sources
PubMed2002

A wireless telemetry system for training users of upper limb prostheses.

Telemetry from prosthetic systems is useful in aiding the users and clinical team in setting up and training and monitoring in the use of a prosthesis. The different forms are discussed and a new radio frequency based telemetry system is described. This system uses a computer to display the data and a video mixer to place the information on the same screen as the image of the user so that their actions and control signals can be simultaneously recorded for later study.

Amputation, Surgical↗
PubMed1997

A method of examining the magnitude and origin of "soft" and "hard" tissue forces resisting limb lengthening.

Complications arising from limb-lengthening procedures such as muscle contracture, axial malalignment of the bone and traction injuries to the nerves and vessels, are often severe. Often complications arise from the build-up of forces in the biological tissues which are resisting lengthening. Little is known about the origin and magnitude of these forces, although three studies have identified the regenerate (new bone tissue) as the dominant resisting tissue. This study describes the development of a method to examine these forces. It employs load measurement devices in the structural columns of Ilizarov fixators which measure the compressive load on the frame exerted by the biological tissues. The distribution of this load between the columns of the frame, in conjunction with a transverse radiograph of the limb at the regenerate site, is used to examine the origin of the resisting force. Accuracy was determined by a laboratory simulation which found the predicted position of the force to be within 5 mm of the actual position in all four cases tested. Mean error in the total measured force was 2 N (SD, 1 N). A pilot study on a patient undergoing a 60 mm femoral lengthening revealed a peak force of 717 N originating in the Vastus Lateralis or the illiotibial tract. Negligible contribution to resistance was provided by the regenerate, contrary to that found with other studies.

Adult↗
PubMed1997

The population of users of upper limb prostheses attending the Oxford Limb Fitting Service.

There is no central database that records the changing provision of prostheses in the United Kingdom. Experience suggests there have been some shifts in the population, particularly in the past decade. Because the detailed records of these changes are contained in the patients' medical records it is difficult to assess the substance of these data except on an individual basis; the larger picture the sifting of a centre's or many centres' data. This paper describes the analysis of one such set of records at the Oxford Limb Fitting Centre. It relates the profile of the population that attends the centre to the general population, and compares the information with that obtainable from other sources. The possible causes for the findings are discussed.

Adolescent↗
PubMed1996

An instrumented spacial linkage for monitoring relative three-dimensional motion between fracture fragments.

A mechanical linkage with electro-magnetic sensors (a displacement transducer) is described, which may be used to measure accurately the relative motion at a bony junction such as a fracture. The linkage may be fixed to bone screws of externally-fixated fractures during routine patient activity, to measure three-dimensional inter fragmentary displacements arising from dynamic loading. Movements of the linkage are monitored by six Hall Effect devices for the six degrees of freedom (three orthogonal translations and three rotations about the translating axes). Measurements are made within error bounds of +/- 0.025 mm and +/- 0.025 deg over a range of 5 mm for the two orthogonal transverse translations, 8 mm for axial translation and 8 deg for the three rotations. Movements at the linkage, remote from the fracture, are then translated mathematically to the fracture site, assuming rigid screw contact with the bone. Displacements of the distal fragment in relation to the proximal, at the fracture center, can then be expressed anatomically through anterior, medial, and distal translations, and rotations in the sagittal, coronal, or transverse planes.

Biomechanical Phenomena↗
PubMed1995

A measurement system for the recognition of arm gestures using accelerometers.

This paper describes a strategy to measure arm movements using accelerometers for the computer recognition of arm gestures. Gesture recognition is being investigated as an alternative method of computer input for people with severe speech and motor impairment; the emphasis is on the needs of people with athetoid cerebral palsy who have difficulties with existing computer input devices. An initial model-based approach to estimate the kinematic motion of the arm from acceleration measurements is given, followed by the chosen measurement scheme. The current system considers the forearm as a rigid body and uses two data streams derived from four linear accelerometers. By treating these signals as outputs from postulated mechanical models, the data are reduced to two series of step inputs that are appropriate for pattern classification and recognition. Although this does not in any way model the arm, the concepts used are based on the type of driving signals expected in the control of arm gestures. Initial experimental results show that the information content of gestures is preserved by this data parameterization.

Arm↗
PubMed1994

Reflex hamstring contraction latency in anterior cruciate ligament deficiency.

Decreased dynamic stability of the knee joint associated with functional disability is a feature of anterior cruciate ligament deficiency (ACLD). The purposes of this study were to examine the between-limbs difference in reflex contraction latency of the hamstring muscles in patients with unilateral ACLD and to investigate its relationship with instability and function. Fifty patients with arthroscopically diagnosed unilateral ACLD were measured bilaterally for reflex hamstring contraction latency (RHCL), and 20 normal volunteers were similarly tested. The subjects were measured in a position of single-limb full weight-bearing with the knee flexed 30 degrees. An anteriorly directed shear force was applied to the tibia, and surface electromyographs (EMGs) recorded the activity of the hamstrings in response to the applied force. The latency of contraction was defined as the time from initial tibial movement, identified by accelerometry, to the onset of increased hamstring EMG activity. Both legs were tested and a between-limbs difference was computed. A significant difference in RHCL was found between the limb with ACLD and the control limb. The mean RHCL of the limb with ACLD was nearly double that of the unaffected limb, for a significant mean between-limbs difference (p < 0.05). The mean between-limbs difference for the control subjects was not statistically significant. The conclusion is that patients with ACLD have an increased RHCL of the injured leg. As the RHCL is dependent on proprioceptive activity around the joint, it can be used as a measure of proprioceptive ability. The loss of the neurophysiological protective reflex involving the anterior cruciate ligament and hamstrings in patients with ACLD is likely to be a contributory factor in the decreased joint stability experienced by these patients.

Adult↗
PubMed1994

The Southampton Hand: an intelligent myoelectric prosthesis.

The form of the control and structure of the mechanism of an artificial hand are important factors which tend to dictate the prosthesis' level of use. Conventional prostheses are simple devices with limited functional range and a control format that requires high levels of user concentration for successful operation. The Southampton Adaptive Manipulation Scheme (SAMS) is a hierarchical control format that allows a larger number of independent motions to be controlled while requiring a smaller degree of user input. The SAMS control has been applied to different hand mechanisms, both custom-made and modified commercial systems. Their application with users shows them to have a performance on a par with, or superior to, other conventional devices. The form of prosthesis control is reviewed and the development of, and clinical experiments with, the Southampton Hand are outlined.

Artificial Limbs↗
PubMed1993

Proprioception after rupture of the anterior cruciate ligament. An objective indication of the need for surgery?

Failure of conservative treatment is the usual indication for the reconstruction of a knee with deficiency of the anterior cruciate ligament (ACL) and this depends on subjective judgement. The ability of muscles to protect the subluxing joint by reflex contraction could provide an objective measurement. We have studied 30 patients with unilateral ACL deficiency by measuring the latency of reflex hamstring contraction. We found that the mean latency in the injured leg was nearly twice that in the unaffected limb (99 ms and 53 ms respectively). There was a significant correlation between the differential latency and the frequency of 'giving way' indicating that functional instability may be due, in part, to loss of proprioception. Measures of proprioception, including reflex hamstring latency, may be useful in providing an objective assessment of the efficacy of conservative treatment and the need for surgery.

Adult↗
PubMed1993

A clinical experience with a hierarchically controlled myoelectric hand prosthesis with vibro-tactile feedback.

UNLABELLED: Improved performance of externally powered myoelectric hands is possible when the direct control of the digit flexion and grip force are given over to an electronic controller which frees the operator to concentrate on other demands. DESIGN: A commercial myoelectric hand was modified to take the new touch and slip sensors and novel control method. SUBJECT: An adult male with a traumatic mid-forearm amputation. OUTCOME MEASURE: The range and ease of use of the prosthetics system. RESULT: The hand was easily and usefully operated in the home and work environment. CONCLUSION: Hierarchical control of a hand is possible using sensory feedback to a sophisticated electronic controller. Such a control method reduces the demands on the user's concentration and enhances the hand's range.

Adult↗
PubMed1991

Prehensile control of a hand prosthesis by a microcontroller.

The functional replacement of a natural hand and wrist is usually achieved by a split hook or an electrically powered and myoelectrically controlled artificial hand with one degree of freedom. In contrast to the commercial devices, this paper describes an experimental hand with four electric motors, nineteen sensors, and control algorithms which are written for a microcontroller. The hand significantly improves the prehension capabilities of an artificial device and leads to a design which is easily controlled by a user as it mimics the control system of the natural hand.

Algorithms↗
PubMed1987

Control of a single degree of freedom artificial hand.

A commercial single degree of freedom artificial hand has been fitted with touch, slip and position sensors, which permit low-level control tasks to be performed by a microprocessor; little conscious effort is required by the wearer. Hardware and software for the microprocessor system are described.

Biomedical Engineering↗
PubMedDate not supplied

Sensory control of a multifunction hand prosthesis.

The current generation of prostheses that are fitted to limb deficient individuals have only a single degree of freedom which limits their functional range. Furthermore, electrically powered prostheses have a limited user input. Electrical signals generated by the contraction of muscles in the user's stump open and close the hand in an 'on and off' fashion. Since the only feedback is visual, the prostheses tend to be used less dexterously than body powered devices. A different approach has been adopted by the Control Engineering Group at Southampton University. They have retained a single electromyographic input channel, but added sensory feedback to an electronic controller, which decides on the grip posture and tension. Satisfactory operation of the hand depends on the sensors employed. A review of transducers used on previous prostheses at Southampton is followed by a description of recent sensor developments. Finally the intentions for a new generation of prostheses are outlined. These include combining sensory input with an integrated circuit microcontroller to provide a more reliable system.

Biomedical Engineering↗