The Orlau swivel walker
J. Stallard *
G. K. Rose *
I. R. Farmer *
Abstract
A new design of swivel walker for the severely disabled is described which has advantages over previous types. Increased rigidity improves the confidence of apprehensive patients, greater strength gives better reliability for those with good ambulation function and a novel construction gives more opportunity for independent transfer into and out of the orthosis, besides easing the burden of those caring for users of swivel walkers.
Introduction
Swivel walkers have long been established as a means of ambulation for severely disabled children (Motloch, 1966). In the 1960's Rose introduced a design (Fig. 1 ) for paraplegics which was described by Edbrooke (1970), and the D.H.S.S. published Notes for Guidance (1973), setting out the biomechanical and medical criteria to ensure that the relevant details were available to consultants wishing to prescribe the device. As a result of early experiences, Rose and Henshaw (1972 and 1973) described an updated design which, with modifications, has subsequently been adopted by the D.H.S.S. for prescription on the National Health Service in kit form.
All these devices greatly increased mobility for many patients, but proliferation showed that the early designs provide only limited independence and are not sufficiently stable for timid or apprehensive children. Other patients discovered that the structural strength was sufficient only for swivel walking ambulation and that more adventurous activities such as swing through gait with crutches or independent transfer carried the penalty of early structural failure.
The attempts of many orthotic firms to produce swivel walkers to their own design confirmed the wisdom of the kit approach advocated by Rose and Henshaw. Many swivel walkers have been constructed with scant regard for the mechanical principles with consequently discouraging results. Other firms have produced very satisfactory swivel walkers but have found the individual approach increasingly costly.
A major use for swivel walkers is for paraplegic patients in special schools for the handicapped. It enables them to ambulate with their hands free so that many school activities are much easier to perform. Whilst many of these schools accepted the advantages of swivel walkers, all complained of the difficulty of transferring patients into and out of the orthosis.
In ah attempt to limit the number of times a patient needed to transfer, designs began to incorporate hinges in the structure, ostensibly to permit patients to sit whilst wearing a swivel walker. Experience soon showed that patients were unable to use this facility independently and that physiotherapists were reluctant to operate the mechanism because of the stress on themselves and the patient. Patients using swivel walkers in the special schools were thus standing in the orthosis for most of the day, but were not complaining of tiredness from this activity. Since no musculature is involved in standing upright in an exo-skeleton of the type used, this was—on reflection—not surprising. Joints in swivel walkers were therefore not being used and had the disadvantage of decreasing the rigidity of the exo-skeleton.
Necessary improvements
A study of the problems of patients and physiotherapists in the special schools showed that the most important need was for independent transfer into and out of a swivel walker from a wheelchair in order to limit the physiotherapist's intervention and so increase the efficiency of the school's staff particularly at arrival and departure times. Some highly motivated patients had developed an ability to do this by first descending to the ground, rolling into the device whilst laid down and then turning over face down to raise themselves laboriously into a standing position by using a dining chair. This technique held the promise of increased independence for a few, but it was enormously energy consuming and not practical for the majority of swivel walker patients.
Other factors were seen to inhibit the independence of some patients. Many appeared apprehensive when standing in a swivel walker due to a lack of rigidity in the structure and were most reluctant to commence ambulation. On the other hand some highly motivated patients developed the ability to use swing through gait with crutches, but were severely hampered by the constant need for repair of a structure not designed for that activity.
It became increasingly obvious that for the full potential of swivel walkers to be realised improvements in four areas needed to be made :
Independent transfer.
Structural rigidity.
Strength.
Ease of construction.
Two modes of transfer had been evolved for patients using swivel walkers:
Transfer from standing to sitting and vice versa.
Transfer to and from the device.
The first type of transfer was never achieved independently and without joints at three levels this is unlikely to occur.
When a normal person sits (Fig. 2 ), they flex their hips, knees and ankles in order to maintain their centre of gravity over the support area of their feet until the last possible moment, when they rock backwards into the chair, probably under the control of their arms on the sides of the chair. Thus swivel walkers require joints at the level of the hips, knees and ankles if loss of balance is not to occur in the very early stages of descent (Fig. 3 ) and existing designs incorporated joints only at the level of hips and knees.
No existing design gave the facility of easy independent transfer of the second type. Patients who could, found that it was time consuming because of all the buckles and straps and that it was expensive in energy. A typical time for transfer from wheelchair to orthosis for those who were capable was 4 1/2 minutes, whilst the reverse process took approximately 1 minute. The two major tasks were securing all the buckles and raising themselves with the orthosis into the vertical position. The need to provide simple location devices for the four support areas was apparent, as was the need to eliminate raising the body from the ground.
A study of orthoses which demonstrated lack of rigidity causing patients to become apprehensive showed that it usually emanated from a combination of low structural stiffness in lateral and sagittal planes coupled with footplate bearing play and low footplate stiffness.
All existing designs of swivel walkers were ostensibly strong enough for their normal mode of operation, although most required adjustment and repair once or twice a year. None were capable of withstanding the rigours of swing through gait. The bearings were unable to cope with the extra bending moments applied by the impact loading on the front and back edges of the footplates and excessive play and bearing damage occurred very rapidly. Some structures failed under buckling and twisting from the additional loads imposed. Footplate covering materials were inadequate to cope with the extra abrasion at the front and rear and as a result the footplates themselves soon began to wear away. Swivel walkers used in this way required frequent attention to keep them operational.
Early designs of swivel walkers were manufactured individually for each patient. This had the advantage that idiosyncracies could easily be overcome and that a good fit should always be possible. However, the approach demanded a level of understanding and expertise of which only a few companies were capable. This made the provision of swivel walker kits an attractive proposition, especially if construction could be made simple.
Orlau swivel walker
The Orlau swivel walker (Fig. 4 ) provides an answer to the problems which occurred with the earlier designs. It consists of a rigid stable frame with improved lateral, sagittal and torsional rigidity, and presents an open aspect at the front for ease of transfer.
The body stabilizing frame is constructed from a base plate of 10 swg half hard BS 1470 aluminium sheet with pressed strengthening ribs, to which are bolted two sand cast side brackets of LM6M aluminium. Side members of l"1/2"1/8" (25 x 12 x 3 mm) HE30TF alu-minium alloy channel section locate into the brackets and are bolted at one of two positions to permit some height adjustment. These side members are braced by 5/8"(15mm)O.D. x 16swg HT19-WP aluminium alloy tubes which pick up on spigoted brackets machined from BS 1476 EICM aluminium alloy which bolt to the rear-ward facing side of the channel section. The tube is located by a cross rivet through the bracket spigot and is bonded with Loctite 601 Superfast Retaining Compound. A depth suitable to clear the patient's knees are supported by hinged sections from each side of the orthosis, a development of the Parapodium (Motloch, 1971) as used on the Breda Splint (Orlau, 1976). These are located on the front facing side of the channel section. The hinged sections consist of BS1476 HE 30TF aluminium alloy strip 1 3/4" (44 mm) wide and 1/8" (3 mm) thick to which are bonded 2" (50 mm) thick medium density Plastazotc blocks. These are cut away to fit over the patient's knees and the two sections are locked together by means of an over centre toggle clamp. Protex 30593/02-502.
Chest fixation is achieved by means of a leather strap to which is attached a Plastazote pad, and this is anchored to one of the uprights by means of a clamp plate and screws. The second, shorter chest strap is similarly located to the second upright and the two straps are buckled together by means of a Britax car safety harness clip—the shorter strap being threaded through the tongue and the clip being riveted to the leather part of the chest pad.
Foot location is provided by a two hooped bar which is attached to an over centre tooling clamp, De Sta. Co. No. 202. This arrangement keeps the feet positioned with the heels adjacent to the bottom of the leg shute to maintain fore and aft location and also prevents the swivel walker from sliding off the body during swing through.
The footplates consist of a sand cast aluminium ribbed construction incorporating a machined bearing housing in which is fitted a FAG 3202 double row ball bearing located by an Anderton NAM 1300/137 circlip. This assembly is completed with Black 12 Iron Estasol bonded on to the bottom face with Evostik to give good grip combined with wear resistance for both normal swivel walking and swing through gait with crutches.
The footplates are attached to the baseplate with flanged cadmium plated M.S. bearing pins located into the inner race with an Anderton AM 1400/56 circlip. Four tapped holes in each flange pick up with four clearance holes in the base plate and take 5 mm diameter screws.
To give parallel footplate motion a spring loaded linkage connects the two footplates and a stop mechanism operating between the bearing pin flange and the footplate on each side permits a degree of overtravel to facilitate manoeuvrability.
Sacral fixation is provided by a 2 mm polypropylene band which is clamped to the side members with M5 x 12 mm countersunk screws and nuts. A series of holes permits limited adjustment so that an appropriate band depth can be easily achieved.
Fig. 5 shows an exploded view of the Orlau swivel walker and indicates the relationship of all the components in the proposed kit.
In order to permit ease of transfer a moulded 1 1/2 mm thick polypropylene leg shute is provided which is riveted to the sacral band and screwed to the base plate. The shape has been developed so that the legs are guided into position as the patient slides down the shute. They do this from their wheelchair with the swivel walker top bracing tube lodged into the seat of the chair (Fig. 6 A-D ). Having lifted their legs into the shute, they control a sliding descent onto the base plate by grasping the side members (Fig. 6 A-D ). With their feet firmly held onto the base plate by gravity they are able to simply operate the footclamp lever, fasten the toggle clamp on the knee bar and clip the chest strap (Fig. 6 A-D ). By pushing up behind them on the wheelchair they rise to the standing position (Fig. 6 A-D ) and are quickly ready for swivel walker ambulation or swing through gait with crutches.
Clinical trials
Five patients were selected for early clinical trials of the Orlau swivel walker. Each of these patients were experiencing problems with their existing swivel walker which the Orlau design was intended to overcome. All the patients were within the immediate care regime of Orlau and this enabled particular aspects of the design to be tested in a controlled manner. The physiotherapists responsible for the children were closely involved both in the monitoring and further development of the device.
The experience with each patient is reported below, and Table 1 shows both the details of the children concerned and, briefly, the changes brought about by the Orlau swivel walker.
Patient A
This patient, aged 10 1/2, had been using a swivel walker from the age of 2 1/2 years and had developed a degree of skill and endurance which gave him a high level of function.
Using crutches he was able to ambulate for distances up to half a mile with swing through gait. In addition he could transfer entirely independently into his swivel walker from a wheelchair and back again. This was achieved by sliding onto the floor from his wheelchair then, after preparing his swivel walker, rolling into it so that he was supine and then, by sitting up, securing the footstraps and knee bands. The chest strap was then buckled by lying down and the patient rolled into the prone position. A nearby dining room chair was then used to "climb" into the vertical position.
This procedure took approximately 4 1/2 minutes, was extremely energy consuming and left the patient in a tired condition.
Both swing through gait and the mode of transfer imposed stresses on the swivel walker structure for which it was not designed. Foot-plates and their bearings suffered frequent failures, as did the curved dural side sections of the body frame. In one period of three months his swivel walker had major repairs on four occasions with numerous minor adjustments.
When supplied with an Orlau swivel walker this patient quickly developed the new slide-in technique of transfer. This procedure took approximately 1 minute, and left the patient fresh for his activities.
In addition the extra rigidity improved his swivel walking performance so that typically he was able to ambulate 6.1 m in 18 seconds as opposed to 24 seconds in his conventional swivel walker.
In a nine month trial, during which all his activities and independence were maintained, the Orlau swivel walker did not require a single repair or adjustment, apart from a minor change after one week.
Patient B
As a younger child this patient had been a good swivel walker, but as he became taller and heavier his ability diminished to the stage when he was extremely apprehensive and required somebody close at hand before he would ambulate.
Standing still in his swivel walker the patient could be seen to feel insecure, making frequent adjustments to his arm positions in order to stave off an imagined loss of balance.
With this device the patient could ambulate 6.1 m in 47 seconds and had to be transferred entirely by a physiotherapist, this taking 4 1/2 minutes.
When supplied with an Orlau swivel walker the patient's confidence increased very rapidly and within two weeks he managed to ambulate 6.1 m in 25 seconds, this time improved to 18 seconds in the following months.
Because of feelings of vertigo this patient was initially reluctant to adopt the slide-in transfer method. However, he did manage to roll into his orthosis and secure himself despite considerable finger disfunction. This took 1 minute 50 seconds, entirely independently, as opposed to 4 1/2 minutes physiotherapist assisted with his previous device. The time to attain an upright posture using a chair was approximately 30 seconds with both swivel walkers. The patient is now content to slide into his swivel walker directly from his wheelchair and is developing the technique of pushing himself into the vertical position.
Patient C
This very young patient could not master the art of swivel walking due to a great feeling ol insecurity and had to be very closely watched whenever he was using his conventional swivel walker. His mother was never more than a couple of paces away because he was prone to over-balancing.
After he was supplied with the Orlau swivel walker he became much more independent and his mother was happy to leave him in a room by himself.
The child was too young to manage independent transfer, but the mother felt the benefit of much easier transfer of the patient.
Patient D
Despite months of training this very poorly motivated patient would not ambulate in a conventional swivel walker without somebody in very close attendance, preferably holding the swivel walker as he rocked from side to side.
After a little training with the Orlau swivel walker the patient was prepared to ambulate without a physiotherapist in close attendance. However, his speed was still very poor and initially constant urging was required for him to indulge in sustained ambulation. With further training this patient became more willing to ambulate and was timed at 2 1/2 minutes for 6.1 m.
Because of poor motivation this patient is unlikely to become capable of independent transfer.
Patient E
This very tall patient suffers with spinal instability. Existing swivel walkers gave her feelings of insecurity and presented restrictions to spinal orthoses of the type she required.
The Orlau swivel walker gave her much greater confidence and she became keen to use the device in contrast to her previous reluctance to use a swivel walker.
Spinal instability still caused her discomfort and a spinal orthosis was made to fit within the swivel walker to overcome that problem.
Discussion
The Orlau swivel walker offers the following specific advantages over earlier designs:
Ease of independent transfer.
Improved strength to withstand extra stresses of transfer and swing through gait.
Increased rigidity to give confidence to apprehensive patients.
Experience has shown that to eliminate problems of poor construction and incorrect mechanical adjustment of swivel walkers it is necessary to make them available in kit form. The Orlau design has been created for this method of assembly and a trial batch of 25 sets has proven to be simple to construct. To reduce the amount of small batch production, each component has, as far as possible, been standardized for the complete size range. Off the shelf components, for example, the foot-plate bearing, have been used wherever possible to increase reliability and reduce supply problems.
At 4.76 kg the Orlau swivel walker is heavier at the top end of its size range than the 4.66 kg of the lightest design of equivalent size, but significantly lighter than the heavier types.
The price of the kit is likely to be similar to existing kit designs, but reductions in assembly time should be possible.
Acknowledgments
The authors wish to express their gratitude to the physiotherapy staff at the following schools and departments for all the help and advice during the development of the Orlau swivel walker. Without their willing co-operation progress could not have been made:
The Katherine Elliot School, Shrewsbury.
The Thomas Parker School, Telford.
Paediatric Physiotherapy Department, Shrewsbury.
References:
D.H.S.S. (1973). Shrewsbury walking appliance.
Notes for guidance. Ref. No. SAL 73/10. Blackpool. Edbrooke, H. (1970). Clicking splint. Physiotherapy,
56: 4, 148-153. Motloch, W. M. and Elliott, J. (1966). Fitting and training children with swivel walkers. Art. Limbs, 10: 2, 27-38.
Motloch, W. M. (1971). The parapodium: an orthotic device for neuromuscular disorders. Art. Limbs, 15: 2, 36-47.
Orlau (1976). Clinical assessment of the Breda splint. Annual Progress Report, No. 2. The Robert Jones and Agnes Hunt Orthopaedic Hospital, Oswestry, Salop, England.
Rose, G. K. and Henshaw, J. T. (1972). A swivel walker for paraplegics: medical and technical considerations. Biomed. Eng., 7 : 9, 420-425.
Rose, G. K. and Henshaw, J. T. (1973). Swivel walkers for paraplegics: considerations and problems in their design and application. Bull. Pros. Res., BPR, 10-20, 62-74.
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