Prosthetics and Orthotics International

The purpose of this study was to look at the current epidemiological trends of lower limb amputees in 1995 and the trends since 1984 in the area of Southern Finland with 1.3 million inhabitants.

During the one-year period, the lower limb amputation was performed on 366 patients. The overall amputation rate has been unchanged since 1984 being 28.0 per 100,000 inhabitants in 1995. The mean age was 71.4 years. The overall amputation rate was 28.0 per 100,000 inhabitants. Of the 366 patients in the study 30% had arteriosclerosis without diabetes mellitus and 49% had diabetes. Diabetes mellitus has become the most common cause of amputation since 1985. Tumours were the cause in 2% and trauma in 4%. The most common unilateral amputations were trans-femoral amputations (29%) followed by trans-tibial amputations (28%) and toe amputations (24%). The unilateral trans-tibial/trans-femoral ratio was 0.54 in 1984 and 0.95 in 1995. The one-year mortality rate was 39% in 1984 and 40% in 1995.

The rate of amputation has been relatively constant over the last ten years. The age related incidence in the older age groups has also been unchanged over the last ten years. Better control of diabetes and prophylactic foot care of diabetics can have a positive contribution in preventation of lower limb amputations. The current rehabilitation and prosthetic services of the lower limb amputees can be planned in the south of Finland on the basis of the incidence of 28 per 100,000 inhabitants.

This study aims to improve the quality and effectiveness of follow-up data on prosthetics in developing countries. In order to bridge the gap between members of non-governmental organizations and their international patients, a field survey was conducted via direct interviews in Vietnam. Eighty-three (83) patients in 5 different geographic regions were interviewed using a standardized assessment tool designed by the author. Demographic information, questions of prosthetic history, inquiries into function, lifestyle and occupation, and queries of social and family integration were asked of each patient.

While the overall results prove salutary for those who serve the amputees of developing countries, it is clear that amputation presents a substantial challenge to the Vietnamese patient. On one hand, respondents wore their prostheses over 12 hours each day on average, rated their prostheses as quite comfortable, and were altogether satisfied with their prosthetic treatment. In addition, the provision of care for Vietnamese with amputations has improved markedly over the past few decades. On the other hand, many patients related the barriers they encountered due to their amputation, including their departure from previous careers, inability to perform rigorous physical activities, and difficulties with social interactions. Furthermore, discrepancies in care were noted between demographic groups and amongst different regions.

The questionnaire developed for this study may provide a useful evaluative tool for agencies working throughout the developing world. The use of such a standardized questionnarie could greatly improve the evaluation and comparison of prosthetic programmes and help guide the efforts of such organizations in developing countries.

The purpose of this study was to assess the overall financial cost of the prosthetic care which war amputees have incurred since the injury occurred.

Records of 98 war veteran amputees who had attended the Dundee Limb Fitting Centre were scrutinised, they revealed 52 survivors and 46 who had died by 1997 and represented all the records available at the time of the review. The number and nature of visits, the number of prosthetic limbs ordered were counted and using today's costs, the cost of these services calculated.

The costs of stump socks, transport and social security payments were not included.

The cost of the artificial limbs was calculated at £(GBP)69 million with the recognition that it is an underestimate and approximation. Despite this it shows that the cost, allowing for the underestimation, has been relatively insignificant in the total cost of a major war and the war machinery.

The cost however to the individuals has been considerable with a substantial disability occurring at the prime of life resulting in a significant handicap.

It is a continuing legacy that society is responsible for, as a direct result of armed conflict.

Force sensing resistors (FSR) have been used to measure dynamic stump/socket interface pressures during the gait of a trans-tibial amputee. A total of 350 pressure sensors were attached to the inner wall of a hydrocast socket. Data were sampled at 150Hz during approximately 0.8 seconds of prosthetic stance of gait. The dynamic pressure distributions within a hand cast socket reported by Convery and Buis (1998) are compared with those monitored within a hydrocast socket for the same amputee. The pressure gradients within the hydrocast socket are less than that of the hand cast Patellar-Tendon-Bearing (PTB) socket. The proximal “ring” of high pressure in the hand cast PTB socket is replaced with a more distal pressure in the hydrocast socket.

The purpose of this investigation was to quantify the structural strength of various trans-tibial composite sockets. To conduct the study, loading parameters and methods were developed that emulate the International Standards Organisation (ISO) standards for structural testing of lower limb prostheses since specific guidelines for the testing of the trans-tibial socket portion of a prosthesis have not yet been established. The experimental set-up simulated the instant of maximum loading during the late stance phase of gait. Ten trans-tibial sockets were evaluated. Five different reinforcement materials and two resin types were used to construct the sockets. A standard four hole distal attachment plate was used to connect the socket and pylon. Each sample was loaded to failure in a servo-hydraulic materials test machine at 100 N/s.

None of the composites in the study met the ISO 10328 standards for level A100, loading condition II (4025 N), as required for other prosthetic componentry. All failures occurred at the site of the pyramid attachment plate. Ultimate strength and failure type were material dependent. Load point deflection was significantly different for the resin variable (p < 0.05). Statistical differences according to reinforcement material were noted in composite weight and strength-to-weight ratio (p < 0.05).

The fibre volume fraction was also estimated and recorded. Reinforcement material type was the primary determinant of performance for the tested samples. Carbon reinforcements performed better than fibreglass reinforcements of similar weave type. The greatest ultimate strength and strength-to-weight ratio was observed with the unidirectional carbon reinforcement.

For the purpose of improving the efficiency of a body-powered prosthesis, a control cable system was developed which uses a pulley and a cable housing which includes a highly slippery plastic liner. Improvements were also made to the harness. In this paper, the mechanism of these systems is firstly described and then, the results of a clinical evaluation test of a practical model is presented along with an efficiency evaluation by a testing instrument. For the design of each system, the material and size suitable for the conditions of cosmetic and general versatility were considered. The clinical test was performed on 12 subjects to prove the effectiveness of the system. This test procedure was repeated. These tests proved the effectiveness of the systems.

This study was performed to investigate the efficacy of prosthetic rehabilitation in children with congenital malformations, also to determine whether there were any factors related to family history and pregnancy which could have affected the formation of such deficiencies.

Twenty-five (25) limb deficient children were provided with prostheses and received rehabilitation. A detailed family and pregnancy history was researched through the records. The ability of performing activities of daily living was scored on a four point scale.

Thirteen (13) lower and 12 upper limb deficient children with a mean age of 4.88±2.52 years were included in the study. Ten (10) children had longitudinal and 15 transverse deficiencies. Traditional marriages amongst close cousins were observed in 31%. Five (5) mothers used medications, 2 received radiodiagnostic tests and 2 had bleedings during pregnancy.

Some 84.7% of the lower limb group became independent walkers without requiring walking aids while 15.3% of them required Canadian crutches for independent ambulation. A total of 61.5% of these children actively participated in recreation with peers. In the upper limb group 41.6% were completely independent in self-care, feeding and hand skills; 33.3% showed independence with self-help devices while 25% tended to use the prostheses for assistive purposes. Participation in recreational activities was 58.2%.

The author's results have shown that the children gained a functional activity level although the prostheses were provided in a late period. It can be concluded that success in rehabilitating these children is a true challenge.

In vivo frictional properties of human skin and five materials, namely aluminium, nylon, silicone, cotton sock, Pelite, were investigated. Normal and untreated skin over six anatomic regions of ten normal subjects were measured under a controlled environment. The average coefficient of friction for all measurements is 0.46±0.15 (p < 0.05). Among all measured sites, the palm of the hand has the highest coefficient of friction (0.62±0.22). For all the materials tested, silicone has the highest coefficient of friction (0.61±0.21), while nylon has the lowest friction (0.37±0.09).

The introduction of modern synthetic casting bandages for splinting of fractures and soft tissue injuries has allowed the development of new casting techniques. Casts can be constructed with a greater degree of function so that controlled motion and stabilisation can be provided within the same cast. This study has shown that a very efficient gait can be achieved with modern synthetic bandages, if they are correctly applied. The authors have compared the gait of volunteer subjects fitted respectively with below-knee walking casts constructed from a rigid glass fibre bandage and a flexible glass fibre bandage which is reinforced. These casts were wrapped so that minimal amounts of bandage were used whilst appropriate strength and stiffness was provided. The temporal and spatial factors of cast gait were not statistically different from normal gait. The cast gait was found to be slightly more asymmetrical (dominant versus non-dominant leg) when a cast was worn and there was also a greater Physiological Cost Index (PCI). The flexible bandage has some advantages compared with the rigid bandage as normal footwear can be worn, the casts are more comfortable and they could be removed with shears, obviating the need for a power saw.

Reciprocally linked orthoses used for paraplegic walking have some form of linkage between the two hip joints. It has been assumed that flexion of the swinging leg is driven by extension of the stance leg. The aims of this study were to investigate the moments generated around the hip joint by the two cables in a Louisiana State University Reciprocating Gait Orthosis (LSU-RGO). Six (6) subjects were recruited from the Regional Spinal Injuries Centre at Southport, who were experienced RGO users. The cables were fitted with strain gauged transducers to measure cable tension. Foot switches were used to divide the gait into swing and stance phases. A minimum of 20 steps were analysed for each subject. Moments about the hip joint for each phase of gait were calculated.

There were no moments generated by the front cable in 4 of the subjects. In only 2 subjects did the cable generate a moment that could assist hip flexion during the swing phase. These moments were very low and at best could only have made a small contribution to limb flexion. The back cable generated moments that clearly prevented bilateral flexion. It was concluded that the front cable, as used by these experienced RGO users, did not aid flexion of the swinging limb.

Joint contractures which do not respond to conventional physiotherapy can be difficult to treat. Serial plastering has been used effectively but is expensive, inconvenient to the patient and does not permit daily hygiene or clinical inspection. A mechanical device has been developed consisting a hinged orthosis which spans the affected joint to which is attached a gas strut to provide a corrective moment about the anatomical joint. Such an arrangement enables prescribed corrective moments to be applied accurately following clinical assessment using routine physiotherapy techniques. The inherently low spring rate of a gas strut ensures that the specified corrective torque is maintained as correction occurs.

Initial treatment experience under the control of the developers had generated wider interest in the system. A geographically distant independent orthotic supply centre was trained in the techniques of application. They treated nine elbow and three knee joints in patients who had not responded to physiotherapy treatment. All of the patients experienced improvement. The average for elbow joints was a reduction in the contracture of 25.6° with a corrective moment of 6.8Nm over a period of 3.9 weeks. For the knee joints the averages were a reduction in contracture of 10.7° with a corrective moment of 12.7Nm over a period of 4 weeks.

The results confirmed the practicality of transferring the system to independent clinical centres and provide evidence to support funding for a formal prospective clinical trial of the treatment approach.

In this technical note, an overview of RTV (room-temperature-vulcanising) silicone elastomers is provided. The properties and applications of 3 different types of RTV silicones in producing prostheses for the hand are discussed. Vinyl polysiloxanes are excellent silicone impression materials that offer the advantages of a rapid cure, near exact duplication of fine details and ease of removal of the cured impression without permanent deformation. RTV-2 dimethyl polysiloxanes are ideal for mould-making and fabricating prostheses given their favourable qualities that range from ease of pigmentation, adjustable consistency, manageable curing rate and accuracy in recording fine details in the liquid state to excellent stain-resistance, elasticity and biodurability in the vulcanised state. RTV-1 dimethyl polysiloxanes are self-curing, readyfor-use silicones that adhere adequately well to most substrates and are useful for extrinsic hue modifications and waterproofing of the prosthesis. The basic techniques for each of these applications are also discussed.

The cure-inhibition of addition-curing RTV silicones by sulphur-, tin- and nitrogen-containing contaminants and its damaging consequence is highlighted. A compilation of known contaminating agents is provided so that prior contact with these objects can be avoided when working with addition-curing silicones. The precautionary measures to prevent the problem are also outlined.

This study looks at the effect of metamerism in colour-matching and the assessment of multi-layered silicone rubber finger prostheses. The aim was to identify the choice of illuminants for colour matching the prostheses that would give rise to the least metameric effect between the prostheses and the human skin or the best colour match. The prostheses were prepared and colour matched to a fair-skinned subject under 3 reference illuminants — TL84, D65, F and a combination of illuminants — TL84, D65 and F. The prostheses were then measured for colour using a spectrophotometer based on the CIE indices L∗ a∗, b∗ with each prosthesis assessed separately against the subject's index finger under the reference illuminants-TL84, D65 and F. The prostheses were also assessed by a panel of 50 observers and scored according to colour-match. Colour differences between the skin and prosthesis were measured in the illuminant under which the prostheses were prepared and then under the other reference illuminants. A relationship was obtained between the measured mean colour difference, δE∗, and the mean visual assessment score for each prosthesis. This paper points out the concerns related to the optical phenomenon of metamerism with the colour pigments used. This can affect the colour match of the prosthesis as perceived by the patient. The findings seem to suggest that this metameric colour difference can be minimised if the prosthesis is matched under a combination of lights, which were found to give the best-perceived match.

Hugh G. Watts, Mary Williams Clark The American Academy of Orthopaedic Surgeons Illinois, USA, 1998 ISBN 0–89203–179–4, pp59