Abstract
A prospective study was carried out on the clinical application and features of a carbon fibre reinforced plastic leg orthosis (carbon orthosis) for polio survivors. The subjects comprised 9 polio survivors, and 11 carbon knee-ankle-foot orthoses (KAFOs) were prescribed, fabricated, and checked out at the authors' post-polio clinic. Walking was classified based on the functional ambulatory category, and the features of walking with a carbon orthosis were self-evaluated by using a visual analogue scale. The period from modelling a cast to completion was 55 ± 25 days; the weight of a carbon KAFO was 27.8% lighter than that of the ordinary KAFO; the standard carbon KAFO was 50% more expensive than the ordinary KAFO. The carbon KAFO remained undamaged for at least 2 years. It improved the scores in the functional ambulation categories, but there was no difference between walking with an ordinary and with a carbon KAFO. The self-evaluation of walking with a carbon KAFO revealed that the subjects using a carbon KAFO were satisfied with their carbon KAFO. The carbon KAFO is lightweight, durable, slim and smart, and is positively indicated for polio survivors.
Introduction
Poliomyelitis is a highly communicable disease causing acute flaccid paralysis of the limbs and/or the trunk, and many children suffering from it have undergone rehabilitative treatments including an orthosis, a cane and/or a wheelchair for gait disturbance (Hachisuka 2002). Although there were epidemics of poliomyelitis in the 1940s and 1950s in the United States, and during 1949 – 1951 and 1958 – 1960 in Japan, new outbreaks have ceased in industrial countries.
About 30 years after the poliomyelitis epidemics, polio survivors are encountering new problems, including generalized fatigue, muscle weakness, and decreased functional capacity in daily and social life. These new problems are known as post-polio syndrome, which is a neurological disorder that produces a cluster of symptoms in persons who had previously been infected with poliomyelitis (Halstead and Wiechers 1985; Dalakas et al. 1986; Hachisuka et al. 1988; Hachisuka 2002). According to a recent survey in Kitakyushu, Japan (Takemura et al. 2004) major physical complaints were difficulty in climbing stairs (57.2%), muscle weakness (55.1%), difficulty in walking (52.1%), fatigue (50.4%), joint pain (38.6%), cold intolerance/numbness (25.8%), muscle pain (24.6%), and shortness of breath (21.2%). Management of post-polio syndrome consists of appropriate exercise to prevent disuse causing muscular weakness, avoidance of muscular overuse, loss in body weight to eliminate excessive loads on the muscles of the lower limbs, use of a suitable light brace to gain stability during standing and walking and to improve gait efficiency, use of assistive devices to maintain independence in daily and social life, and alteration of lifestyle to cope with the syndrome and to conserve energy (Hachisuka 2002; Trojan and Cashman 2004).
The authors have prescribed lower limb orthoses for 83 polio survivors at their post-polio clinic during the past 5 years, and the number of patients who have an orthosis prescribed is increasing because some polio survivors want to wear a lighter brace in ageing, and others have noticed symptoms of post-polio syndrome in recent years, requiring a new lower limb orthosis. Although polio survivors who used an orthosis for gait disturbance have already grown accustomed to it, they still often complain about it: “heavy when walking,”“uncomfortable to walk,” and “unattractive appearance”. A typical polio survivor may not be satisfied with a lower limb orthosis, even if it fits very well and improves gait disturbance (Hachisuka 2002; Aeillo 2004).
A recent development in the field of orthosis is a carbon fibre reinforced plastic leg orthosis (carbon orthosis), which may reduce the complaints of polio survivors regarding orthoses. Carbon fibre has been applied to prostheses and orthoses (Nelham 1981) and carbon orthoses have been prescribed for myopathic patients (Granata et al. 1990), polio survivors (Heim et al. 1997; Hachisuka 2002; Steinfeldt et al. 2003) and stroke patients (Danielsson and Sunnerhagen 2004). In general, a carbon orthosis looks good, and is lightweight, but is unable to be adjusted or modified during or after fabrication to improve the fit. Therefore, clinical indicators need to be examined for carbon orthoses for polio survivors, and whether such an orthosis is really useful for improving gait efficiency in polio survivors needs to be confirmed. As a first step in the study on carbon orthotic management for polio survivors, the authors proposed a procedure of manufacturing a carbon orthosis which polio survivors were satisfied with, investigated problems encountered by rehabilitation doctors, orthotists, and polio survivors, and performed a prospective study on the features of the carbon orthosis, using a visual analogue scale.
Materials and methods
The subjects comprised 9 consecutive polio survivors (2 men and 7 women) who came to the authors' post-polio clinic and had a carbon orthosis prescribed, fabricated, and checked out, and were 52.1 ± 8.9 (mean ± standard deviation) years of age. Onset of polio was 1.3 ± 0.7 years of age, and 9 patients had bilateral leg paralysis. Three of them had never previously used a leg orthosis, and 5 were diagnosed as having post-polio syndrome, according to the criteria (Halstead 2004).
Because it is not possible to modify the fit and alignment of a carbon orthosis during or after fabrication, the authors adopted the following procedure for prescription, fabrication and checking out:
A physical examination including assessment of any discrepancy in leg length, muscle strength, range of motion, and gait;
An X-ray examination of the hip, knee and ankle joints, if necessary;
The patient's preference regarding an orthosis;
Prescription of the carbon orthosis: A knee-ankle-foot orthosis (KAFO) or ankle-foot orthosis (AFO), with locked or off-set knee joints and with free-motion or solid ankle joints;
Fabrication of a temporary orthosis consisting of metal uprights and polypropylene (Figure 1 (left));
Trial use of the temporary orthosis for 2 – 4 weeks;
Modification of the temporary orthosis to match the figure and alignment of the prospective carbon orthosis;
Trial use of the modified temporary orthosis for 2 – 4 weeks, including admission and gait training under the supervision of a physical therapist if necessary; and
Fabrication of the carbon orthosis with acrylic resin (C-Orthocryl, Otto Bock, Germany) and carbon fibres in the same alignment and shape as the modified temporary orthosis based on discussion with the patient.
Temporary and carbon KAFOs. Left: the temporary KAFO for case 3 consists of bilateral metal uprights, Swiss lock knee joints, free-motion ankle joints, a posterior half shell and a pre-tibial shell made of polypropylene, and a sole. Right: the standard carbon KAFO for case 6 consists of a posterior half shell and a pre-tibial shell made of carbon fibre-reinforced plastic, Swiss lock knee joints, and free-motion ankle joints.
Walking without any orthosis, with an ordinary KAFO and with a carbon KAFO was classified into five categories by a board-certified physiatrist in order to evaluate the severity of gait disturbance, based on functional ambulation categories (Tyson and Thornton 2001): (i) continuous support, (ii) intermittent support, (iii) supervision, (iv) independent on level ground only, and (v) independent anywhere.
Six subjects who had experienced both ordinary and carbon KAFOs performed a self-evaluation of walking with a carbon KAFO. Comparing their own carbon KAFO with their previous ordinary KAFO, they were asked to respond to the questionnaire, which was developed based on the questionnaire on lower limb management for post-polio patients (Waring et al. 1989). The original questionnaire rated “fatigue, weakness, ability to walk, overall pain, knee pain, back pain, hip pain, foot pain and perceived walking safety” based on a 5-point scale. Considering the features of the carbon orthosis, the authors replaced “weakness” with “awareness of the weight of the orthosis”, divided “ability to walk” into “walking distance” and “speed”, and replaced “overall pain” with “appearance of the orthosis”, and adopted a visual analogue scale instead of a 5-point scale. If the patients considered the carbon orthosis completely superior to the previous ordinary orthosis as regards an item in the questionnaire, they were instructed to mark the right end of the 10 cm line, and if completely inferior, they were instructed to mark the left end of the line.
Results
Eleven carbon KAFOs were fabricated for nine subjects (Table I) who had a muscle strength score of less than 3 for quadriceps and ankle extensor and/or flexor in the lower limbs involved. Six of the 11 carbon KAFOs were standard, consisting of a posterior shell, Swiss lock knee joints, a pre-tibial shell, free-motion ankle joints, and a sole (Figure 1 (right)). Two of the 11 carbon KAFOs had off-set knee joints for two subjects with slight instability in their knee joints, one carbon KAFO had ring lock knee joints because of personal preference, and two carbon KAFOs had a solid ankle for two subjects with arthrodesis at their ankle joints. One subject had a standard carbon KAFO for his left leg and a KAFO with off-set knee joints for his right leg. One subject using a carbon KAFO with off-set knee joints had another carbon KAFO with Swiss lock knee joints made after one year to gain more stability in her knee joint.
Subjects' profiles.
A standard carbon KAFO consisted of a posterior shell, Swiss lock knee joints, a pre-tibial shell, free-motion ankle joints, and a sole; 2One subject wore two orthoses: a standard carbon KAFO for his left leg and a carbon KAFO with off-set knee joints for his right leg; 3One subject had two orthoses for her right leg, because she wanted to exchange off-set knee joints with Swiss lock knee joints to gain more stability after one year.
The period from modelling a cast to completion of a carbon orthosis was 55 ± 25 days (range: 19 ∼ 80). The weight of a carbon KAFO was 990 ± 203 g, that is, 27.8% lighter than an ordinary KAFO. The price of a standard carbon KAFO was 180,000 yen (US$1,700), 50% more expensive than the ordinary KAFO.
From the results of the functional ambulation categories, a carbon KAFO as well as an ordinary KAFO improved gait disturbance in those subjects who had already used an ordinary KAFO (Figure 2), but no inter-category difference was found between walking with an ordinary KAFO and with a carbon KAFO. All subjects regarded their carbon KAFO as being comfortable, and seven of the subjects always used their carbon KAFO both indoors and outdoors and two used theirs only outdoors.
Functional ambulation category. Gait disturbance was evaluated based on the functional ambulation category when a polio survivor came to see a doctor at the post-polio clinic. The following categories were used: (i) continuous support, (ii) intermittent support, (iii) supervision, (iv) independent on level ground only, and (v) independent anywhere. Cases 1 ∼ 6 had already used an ordinary KAFO, and cases 7 ∼ 9 had never used one before.
From the self-evaluation of walking with a carbon KAFO (Figure 3), the subjects using a carbon KAFO were more satisfied with their carbon KAFO than with their previous ordinary KAFO, especially, as regards “fatigue during walking, safety during walking and appearance”.
Self-evaluation of walking with a carbon KAFO. Six polio survivors were asked to respond to the visual-analogue scale of the questionnaire, comparing their own carbon KAFO with their previous ordinary KAFO. Zero and 100% meant completely unsatisfied and completely satisfied, respectively, and the bars in the graph are standard errors.
During the follow-up of the subjects for at least two years, the carbon KAFO remained undamaged, but a plastic cable and two steel springs of the Swiss lock knee joints needed to be changed.
Discussion
The small number does not permit a statistical analysis and the results cannot be extrapolated to all polio survivors, but the results of this prospective study show clear positive indicators for a carbon orthosis.
The authors confirmed that a good fit of the carbon KAFO and excellent outcomes were obtained using the procedures described for prescription, fabrication, and checking out, although the procedure was a time-consuming process and much effort and patience were spent by the polio survivors, in particular, and by the orthotists and physiatrists.
The carbon KAFO has been proven to have desirable features: Lightweight, durable, slim and smart, and polio survivors seem to consider walking with a carbon KAFO as being safer and less tiring due to the good fit and solid support of the carbon KAFO. The carbon KAFO may increase walking distance and speed as supported by the self-evaluation results, because the carbon KAFO is lighter in weight, fits better, and gives more support. These advantages of the carbon KAFO may compensate for the amount of time, effort, and patience required during the prescription, fabrication, and checking out and the 50% higher cost for completion of the carbon orthosis. However, placebo effects or satisfaction with something new may bias the self-evaluation, and further investigation including objective measurements is needed to confirm the advantages of the carbon KAFO.
An off-set knee joint may be attractive for a polio survivor who has never used a KAFO before, and may be convenient for an office worker, who frequently has to stand up and sit down. A KAFO with off-set knee joints brings considerable stability during the stance phase on a flat floor, but an active polio survivor would ultimately choose a Swiss lock knee joint to ensure stability when walking on an uneven road or a downhill slope. Before an off-set knee joint is prescribed, the authors must deliberate on whether it will really relieve the polio survivor of any instability in his/her knee joint, because no changes can be made afterwards with a carbon KAFO, for example, one cannot switch knee joints.
The carbon KAFO is quite a new development in the orthotics field, it has clear advantages, it is light in weight, durable, slim and smart, and is appropriate for patients with a lower motor neuron lesion especially polio survivors. However, it is not suitable for all persons with lower limb disabilities at the present time. A lightweight durable orthosis may not be essential for persons suffering from an upper motor neuron lesion, for example, hemiplegia, as much as for those suffering from a lower motor neuron lesion because spastic paralysis brings voluntary or involuntary muscle contraction. Some persons may make their choice based on the price of an orthosis. The manufacturing procedure of a carbon KAFO is time-consuming, requires a lot of effort, and it is unable to be repaired afterward.
In order to make the carbon KAFO more popular in the foreseeable future, it would be desirable to reduce its cost, to invent a less time-consuming method for prescribing, fabricating, and checking it out, to develop a new Swiss lock knee as durable as carbon-reinforced plastic, and to demonstrate the superiority of efficiency of walking with a carbon KAFO.
Conclusion
The carbon KAFO is lightweight, durable, slim and smart, and if it is appropriately prescribed, fabricated, and checked out, it should be a good option for polio survivors who need a KAFO.
Footnotes
Acknowledgements
The clinical study was performed in cooperation with Saburo Ohmine, RPT, at the Department of Rehabilitation, University Hospital of Occupational and Environmental Health and Kenji Arai, CPO, at Arai's PO Ltd.