Paraplegic Abstracts

Electrical Stimulation To Enable Sit To Stand Following Paraplegia - A Case Report.

Experience In Using Knee Angles As Part Of A Closed-Loop Algorithm To Control
Fes-Assisted Paraplegic Standing.

Results from bone mineral density scans in paraplegics.

Apparatus to simultaneously measure fourteen isometric leg joint moments. Part 2: Multi-Moment Chair System.

Wheelchair Accessory Standing Support.

Limb Blood Flow, Cardiac Output and Quadriceps Muscle bulk Following Spinal
Cord Injury And The Effect Of Training For The Odstock Functional Electrical Stimulation Standing System.

Dunkerley AL MSc & Wood DE PhD

Research Physiotherapist & Clinical Engineer

Department of Medical Physics & Biomedical Engineering, Salisbury District Hospital

16th Guttmann Multi-Disciplinary Meeting, 1999

Electrical stimulation has been used as an exercise to maintain lower limb muscle bulk following spinal cord injury, both for cosmesis and observed physiological benefits. Some subjects have strengthened the quadriceps & gluteal muscles sufficiently to enable electrically assisted standing. Standing with this method may provide greater accessibility and enable tasks to be carried out more easily than other standing systems, such as calipers. It has been suggested that standing achieved dynamically by electrically assisted muscle contraction may be more favourable in promoting retention of bone mineral density than the widely followed practice of passive standing in a frame.

The results obtained with one subject, from a larger group selected through strict criteria for a possible implanted stimulator, are presented. Our subject is aged 40 years and sustained a traumatic T10 complete spinal cord injury in 1994.

A three month period of muscle retraining was completed. Measurements of muscle bulk, force and spasticity were taken at baseline and regular intervals throughout the programme. Increases in quadriceps muscle depth were observed and peak extension torque increased from 42.6Nm to 70.2Nm (right) and from 41.41Nm to 59.4Nm (left), at the end of the training period. Spasticity has remained relatively constant.

Standing between parallel bars with FES assistance was possible after three months. During the following three months, standing was conducted in the laboratory in order for the subject to perfect his technique and to optimise the closed loop system. Daily stimulation of the abdominal muscles was introduced which was found to reduce spasticity and enabled easier standing.

The aim is to fine tune the parameters of the closed loop surface standing system to allow short duration functional stands outside the clinical setting for specific tasks. A portable, integral frame attached to the lightweight wheelchair will provide hand holds for standing up and steadying with minimum one hand during each stand.

This work was funded by the Welcome Trust.

Wood DE1, Harper VJ1, Barr FMD2, Taylor PN1, Phillips GF2, Ewins DJ3

1 Dept. of Medical Physics and Biomedical Engineering, Salisbury District Hospital, Salisbury

2 FES Research Unit, Spinal Injuries Unit, Royal National Orthopaedic Hospital, Stanmore

3 Biomedical Engineering Group, University of Surrey, Guildford

6th Vienna International Workshop on Functional Electrostimulation

SUMMARY

Using electrical stimulation of lower limb muscles to assist paraplegics to stand has been successful in many centres. However, it does have its problems; primarily the maintenance of stable balance in response to muscle spasms and fatigue, postural changes and external perturbations. These need to be addressed for an FES-based system to be safe for a paraplegic to stand and remove one hand to perform a task. A standing system has been developed for mid-low thoracic complete lesion paraplegics, which implements a closed-loop algorithm. Measurements of the knee angles are used to monitor the stand and changes to these act as an input to the controller, which responds by adjusting the stimulation levels to the quadriceps. The performance of the controller, based on a PID design, is evaluated by subjective assessments of the stand, both when quiet and during physiological and enforced disturbances. Optimisation of the PID algorithm is based on general rules used to calculate initial estimates and from clinical experience. This technique has been used successfully to control standing with 23 paraplegics, 14 of whom have used it at home.

Wood DE, Dunkerley AL, Tromans AM

Presented at the 16th Guttmann Multi-Disciplinary Meeting, Southport, 1999

A rapid loss of calcium occurs in sub-lesion bones during the first weeks following traumatic SCI. Studies have shown that with time the rate of calcium loss decreases, but even after three years it is still above that of an age matched control subject. It is generally thought that this may lead to osteoporosis, with increased risk of secondary medical complications and fractures from minor trauma. We have scanned 16 male paraplegics (complete traumatic T3-T12, >1 year post-injury) for selection onto a FES-assisted standing programme. Subjects who show indications of osteoporosis in the femoral neck or the lumbar vertebrae are not recruited because of a perceived increased risk of fracture if they stood. The scans reported are by dual energy X-ray absorptiometry (DEXA) and T-scores are calculated. This expresses the deviation of the bone mineral density value from a young adult mean, with osteoporosis being defined when this is more than 2.5 standard deviations; T<-2.5 (for interest a normal density is indicated by T>-1.0). Our results showed that 15 of the femoral necks were below normal, but only 5 indicating osteoporosis. Only 1 of the lumbar scans was below normal, but not osteoporotic. No correlation was found between T-scores and age, time post-injury and level of lesion. The results contradict the generally held belief that osteoporosis, to some degree, is present below the level of the lesion. We recognise that this group of subjects may not be representative of the paraplegic population, but comparative results are not available because scanning is not routinely done at spinal units. Further studies are required to see if these findings are representative. The possible risks could then be assessed and interventions currently used for its management, such as standing or passive and weight bearing exercises, evaluated.

Wood DE, Donaldson NdeN1, Perkins TA1 1

Department of Medical Physics and Bioengineering, University College London, London, U.K.

Medical and Biological Engineering and Computing, 37(2): 148-154, 1999

Read in conjunction with: Donaldson NdeN, Munih M, Perkins TA, Wood DE. Apparatus to simultaneously measure fourteen isometric leg joint moments - Part 1: design and calibration of 6-axis load cells for the forces and moments at the ankle. Medical and Biological Engineering and Computing, 37(2): 137-147, 1999.

An apparatus has been developed that measures isometrically the fourteen lower limb joint moments corresponding to the degrees of freedom of the hips, knees and ankles. This is the second of two papers describing the development of the Multi-Moment Chair System (MMCS). It presents the overall design and changes that were implemented to compensate for problems. These were primarily to improve the accuracy of hip joint moments; a compromise between accuracy and practicalities, because of force-moment responses being measured at the ankles. All joint moment errors have been calculated to be of the order of a few Nm. Since these represent errors of less than 10% when considering peak joint moment responses, this is considered sufficiently accurate for our application. The MMCS is being used in a programme to investigate the restoration of lower limb functions, principally standing, in paraplegics by electrical stimulation of the lumbosacral anterior roots.

Anderson JA 1, Dunkerley AL, Wood DE

1 Industrial Design Engineering, Royal College of Art, London SW7 2EU

Presented at the 5th IPEM Annual National Conference, Nottingham, 1999

The Abilizer is 'a standing device for wheelchair users to enhance social interaction and functional ability'. The device provides assistance during ascend and descend of standing and helps the user to maintain balance while performing single-handed actions. Primarily for use with mid-thoracic paraplegics using electrical stimulation to achieve standing, it is the intent to extend this to other groups, e.g. with neurological or arthritic conditions. An existing frame used at Salisbury applies most of the force vertically through support sticks attached to the wheelchair frame. However, three key concerns exist, i.e. ease of use and portability, adaptability to different types of wheelchairs and occasional problems with the mechanism. The Abilizer addresses these concerns and attempts to meet the functional needs of a standing system as well as the users' needs and expectations. Challenges to meet the design criteria have resulted in sliding, rotating and locking mechanisms with the major forces still being applied through vertical supports. These are housed on extender arms which locate the support at the minimum user distance. To set up, the user pulls the support sticks forward and than rotate the quick release arm through 90 degrees. This is than extended, re-locked and the sticks are released to ground. Side braces, mounted between the seat and front frame, uses flexible fittings to accommodate different wheelchair frame angles. Concept testing has been with a Quickie GPS wheelchair. Additional testing is required with the cast prototype and paraplegic standing patient, providing the necessary feedback for concept finalisation.

Paraplegia 31 (1993) 303-310

Limb Blood Flow, Cardiac Output and Quadriceps Muscle bulk Following Spinal Cord Injury And The Effect Of Training For The Odstock Functional Electrical Stimulation Standing System.

P.N.Taylor, BSc, MSc, MBES, D.J.Ewins BSc,Ph.d, MBES, B.Fox,* SRP,GRAD DIP PHYS, MCSP, D.Grundy,* FRCS, I.D.Swain, BSc, Ph.D, CEng, MIEE, MBES.

Department of Medical Physics and Biomedical Engineering,

*Duke Of Cornwall Spinal Treatment Centre,

Odstock Hospital, Salisbury, Wiltshire, SP2 8BJ.

Abstract

As part of the assessment of the Odstock Functional Electrical Stimulation (FES) Standing system for mid to low thoracic lesion spinal cord injured (SCI) subjects, cardiac output, thigh blood flow and quadriceps muscle thickness were measured before and following an electrical stimulation muscle retraining programme. The same parameters were also measured in a group of uninjured subjects and in SCI subjects. It was found that there was no difference in cardiac output between the groups. However thigh blood flow was found to be around 65% of normal values in the spinally injured group. This returned to normal values following the retraining programme. The quadriceps muscle wasted to approximately 50% of its original thickness in the first three weeks following spinal cord injury. The retraining programme increased the muscle thickness to near normal values.