New technical advances in swivel walkers.

Swivel walkers were commonly prescribed for children with complete thoracic lesion myelomeningocele in the 1970s and 80s, when the incidence of spina bifida in the UK was of the order of 3 per 100,000 live births. The advent of reciprocal walking orthoses provided a more suitable alternative for those with good upper limb and trunk function, and swivel walkers were then used primarily for very young or more severely disabled patients. Pre-natal screening has dramatically reduced the incidence of spina bifida in the UK and subsequently swivel walkers have been used in a wider range of pathology, including spinal muscular atrophy, multiple sclerosis, muscular dystrophy and other neurological conditions that lead to lower limb dysfunction. The detail design of these devices has been adapted to accommodate the specific problems encountered in these conditions. In particular the designs have been updated to: enable very young patients to be more readily fitted at the age of 1 year; allow the walking mechanisms to be conveniently adjusted for easier ambulation when weakness or lack of confidence inhibits performance; permit simple adjustment to a standing frame mode to enhance stability in situations of increased risk; promote manual handling practice that is compatible with the National Health Service (NHS) policy of compliance with relevant regulations. To underpin appropriate prescription and safe supply the NHS Procurement Agency have encouraged the development of a common course for all types of swivel walker.

Evaluation of safety and reliability in an infant reciprocal walking orthosis.

In response to new demands for infant walking orthoses consideration was given to the development of a device for this category of patient. A specially developed hip joint with the required structural properties (Woollam et al., 2001) provided an opportunity for this development. Earlier structural assessment, and limited cyclic load testing of key elements of the orthosis (primarily the body brace), confirmed that a safe device for evaluation with patients could, theoretically, be produced. A provisional prototype was therefore designed and manufactured for initial structural testing of the complete infant orthosis (Stallard et al., 2001). Efficiency of walking is strongly influenced by the lateral rigidity of the orthosis. Monitoring the structural performance of the provisional infant design indicated it would equal or improve on the stiffness of that achieved in the adult specification. Additionally, relative strength was comparable with the adult version, which has proven to be safe and reliable in many years of routine prescription. This, together with the limited cyclic testing of the complete orthosis (Stallard et al., 2001), gave confidence that it was safe to proceed with controlled field evaluation of the infant design when supplied as a rehabilitation engineering device within the provisions of an ISO9001 and EN46001 QA System. This additional study of controlled patient use, and further representative cyclic load testing in parallel with the field evaluation, had established the long-term structural safety of the orthosis. Wider application is now to be introduced through completion of the EC (European Community) Medical Devices Directive formalities.

An infant reciprocal walking orthosis: engineering development.

The growing trend of prescription of reciprocal walking orthoses for children under the age of 5 years has created a requirement for a new design of orthosis in this category. In response to this new demand, a prototype orthosis for infants, incorporating a specially developed hip joint and manufactured as a rehabilitation engineering device within the provisions of the EC Medical Devices Directive, has been produced and tested. A design feature that strongly influences the efficiency of walking is the rigidity of the body brace structure. Monitoring the specific structural performance of the body brace intended for infants showed that it would equal or improve the stiffness achieved in an orthosis for adults. Additionally its strength was comparable with the adult design, which has proven to be safe and reliable in many years of routine prescription. Incorporation of the infant body brace within a complete orthosis provided a structure of more acceptable physical dimensions for these more diminutive patients. The orthosis showed no incipient sign of failure after 100,000 cycles of representative service loading equivalent to that imposed by a 20 kg (5-year-old) patient. The results of structural assessment and cyclic load testing confirm that the design of the orthosis sufficiently satisfies the statutory requirements for devices that are safe and fit for purpose to permit field trials with patients.

The ORLAU VCG (variable centre of gravity) swivel walker for muscular dystrophy patients.

Swivel walkers are being increasingly used for muscular dystrophy patients in order to prolong the period of their ambulation. Existing designs did not address the special problems of accommodating such patients comfortably and providing the easier and more assured ambulation which their weakened condition requires. The ORLAU VCG (variable centre of gravity) swivel walker has been developed so that the walking mechanics can be adjusted independently of patient posture. Additional patient support features permit the patient to be secured in their chosen position of comfort prior to setting the ambulation mechanics. Patients using the device, which is now approved for supply by the Department of Health in England and Wales, have improved their walking performance and extended their period of walking.