Patent Application
20190231578
The present invention pertains to production of customized split insole for use by diabetic patients so as to prevent or reduce the chance of formation of foot ulcers and thereby gangrene and amputation.
Lower most part of human body is the foot, which provides balance, supports in mobility and makes human to do numerous activities like walking, running, jumping, climbing and other activities (Healthline, 2015). The complex structure of foot comprises of 26 bones and 33 joints, ligaments, muscle and more than hundred tendons working together to allow the foot to adjust to walk on the uneven surfaces either it is even or uneven, and acts as a shock absorber (Watt, 2009). The interaction between the foot and ground are very important in designing the footwear and orthotic devices (Albert et al., 2011). The ill fit shoe or orthotic device design causes high pressure in the plantar surface of the foot, which interfaces foot and footwear or foot and ground surface. Peak pressure in the contact area leads to foot deformities, ulcers, corns, calluses and bunions (Dunn et al., 2004).
According to International Diabetes Federation (IDF, 2013), 387 million people have diabetes in 2013 and this is expected to rise to 592 million by 2035. Seventy seven percentage of the diabetic people live in low and middle-income countries, every seven seconds a person dies from diabetes and it caused 5.1 million deaths in 2013. Diabetes impacts the humans primarily on three organs, namely kidneys, retina and foot. Foot problems in a person with diabetes can have severe consequences. A study conducted on diabetic foot amputation by Amit kumar et al. (2010), revealed that out of 114 patients 48 had undergone foot amputation. (Hadi et al. 2012), concentrating on foot, revealed that foot forms a primary contact with ground surface and there is a great care to be taken in the plantar region of the foot. Ill-fitting footwear causes injury and deformity and specific care is to be taken while selecting the shoe types and shoe fitting (Watt, 2009).
The primary reason for amputation was identified to be because of lack in preventive measures to reduce the burden of ulceration and amputation in diabetic foot. Discussing about the foot ulceration, it was found to be present in feet of the patients. Stokes et al., (1975) used a segmental force platform to study 37 feet of 22 diabetic patients. High loads were found at the sites of ulcers. Patients with high loads under the feet were also heavier in weight than those with lower loads. Toe loads in patients with ulcers were found to be reduced. A shift of maximum loads to the lateral foot in neuropathic patients was also reported.
With loads that are exerted and pressure that emerges underneath the feet playing major role leading to amputation of the foot/portion of the foot or limb itself. Boulton et al., (1983) employed the optical pedobaragraph for research purposes to examine the relationship between high foot pressures and ulceration. In their study, diabetic patients with and without neuropathy and individuals without diabetes were examined to evaluate the relationships among foot pressures, neuropathy, and foot ulceration. Their results demonstrated that a significantly larger number of patients with diabetic neuropathy had abnormally high foot pressures compared with controls. Furthermore, patients with a previous history of foot ulceration had high pressures at ulcerative sites. As ulceration occurred at sites of high plantar foot pressures, therefore, foot pressure reduction should lead to a reduced incidence of foot ulceration in neuropathic diabetic patients.
Duckworth et al. (1985) working on plantar pressure measurement identified that foot ulcer occur at high pressure regions, and inorder to detect them they suggested static and dynamic pressure measurement devices to measure plantar surface pressure points. In order to measure plantar pressure distribution, Wolfe et al., (1991) suggested, ‘Plantar Pressure Measuring Device’ which is clinically used to scrutinize the asymmetry of plantar pressure distribution in young adults with ankle fractures. They also suggested the use of the same device to measure plantar pressure in diabetic patients with Charcot neuroarthropathy. They used these measures to correct the gait pattern in accident victims, to analyse orthotic problems only and not for any other purpose.
Every person requires an individual assessment of the foot and a customized insole to avoid foot related problem (Zequera and Solomonidis, 2010). Material and shape of the customized insole plays key role in redistribution of plantar peak pressure (Cheung and Zhang, 2007, Tsung et al., 2004).
The custom made insole with a medial arch support may transfer load from the forefoot to the midfoot compared with a flat insole (Bus et al., 2004). The significance of providing arch support is that, it will help in offloading the peak pressures across different anatomical zones. Brown et al. (1996) also found increased midfoot peak pressures in 10 healthy subjects wearing custom made insole or arch supports.
Many podiatrists follow traditional plaster cast mould manufacturing method to fabricate the orthotic device, while cost are high in this method (Crabtree et al., 2009). The design and development of customized footwear has been in practice for the past three decades. Latest development in the field of CAD/CAM and scanner has accelerated the production of orthotic devices (Parreno, 2007). Crabtree et al. (2009) investigating on manufacturing methodology for personalized sports insole; suggested cryogenic machining method as a novel manufacturing method for manufacturing a personalized sport insole. In this method CNC machining is used to produce CAD model from the scanning and assessment methods enables rapid manufacturing of personalized products.
Ability to incorporate the novelty in the design of orthotic device is limited because of the manufacturing methods (Telfer et al., 2012). Recently, we had performed a comparative study of diabetic and non-diabetic population, data were analyzed with respect to different foot types. Plantar pressure values are same for normal and high arch foot for both population. Flat foot diabetic population had a high pressure in the metatarsal region when compared to non-diabetic population. As remedy to overcome the load distribution, the designer has to achieve an optimal design for an individual, with each individual is unique; different in structure, size, movement and gait pattern. An effort was made to aid the design and development of customized split insole using manual masking/zone splitting of the foot plantar region.
One of the very recent surveys conducted by us over a population size of 261 people, 77% is found to diabetic between the ages of 35 to 65. Focus was towards analysis of foot problems of the diabetic patients. Foot problems in a person with diabetes can have severe consequences. Though, recent advances in the management of these problems have increased our abilities to save the lower limb, the best management lacks in taking preventive measure.
This invention is projected towards analyzing diabetic patients about their levels of complication in their lower limb such as foot ulcer, neuropathy and gangrene. Where, foot ulcer is high in the areas of pressure point in the plantar surface leading to gangrene and amputation of lower limb. The pressure point in the plantar surface in the body is dependent on age, weight, lifestyle and further it varies from patient to patient. As the plantar surface differs from person to person and being not the same foot sole can be used for all. This is because of varying pressure point and individual gait pattern.
The gait pattern of a person has a lot to do with the stress and pressure exerted on the foot. Therefore, the gait pattern directly affects the plantar surface of the foot. In normal person, from childhood to middle age the gait pattern does not have any significant harmful effect on the plantar surface of the foot. However, ageing may cause certain orthotic problems which may directly or indirectly affect the plantar surface of the foot. The build-up of pressure on the plantar foot surface has a direct bearing a plantar foot ulcers, especially in diabetic patients. Foot Ulcers occurs at sites of the high pressure on the plantar surface of the foot.
The human foot consists of three parts namely the hind foot, mid foot and the fore foot. The hind foot consists of two bones one on top of the other. The mid foot consists of five bones packed close together, while the fore foot consists of five metatarsals each with phalanges (toes).
The superior surface of the hind foot forms the ankle joint which articulates with the tibia and fibula in the medial and lateral position respectively.
During walking, the entire body weight is mostly borne by one leg at a time. The fibula bone transmits weight to the talus and to the rest of the foot. During walking, when the body first touches the ground, the calcaneus (Head bone) takes the entire weight. But, however, still some body weight is shared by the other foot as well. Once the heal is firmly on the ground, the other foot leads the ground. The fore foot touches the ground, but usually, the lateral border of the foot takes on the weight first transmitting it through the cuboid bone and the base of the fifth metatarsal. Immediately, thereafter, the whole foot is on the ground. Thus, the body weight is transmitted from the calcaneus or head bone to the cuboid bone to the base of the fifth metatarsal and then the heads of all the five metatarsals. Then, when the other foot swings forward, the heal begins to leave the ground and the whole weight is shifted to the forefoot. Thereafter by a strong contraction of the toes, the body is pushed forward to transfer its weight on the other foot which is now in a stable position to receive the transmitted weight. This is one walking cycle.
Therefore it can be said that in one walking cycle, when the foot comes down, it rests back of the heal, then on the lateral side of the metatarsal and finally on the heads of the metatarsal to push off for the next step.
Similarly, when a person is standing, both foot are on the ground where the foot is like an arch sparing the mid foot from weight bearing.
It is therefore fascinating to analyse how instinct the mechanism of walking or standing or running is. The foot therefore displays several motions like acceleration, deceleration, sudden stop, jumping, twisting, turning, kicking, squatting and so on. During all these motions, the pressure exerted on the plantar foot varies.
In diabetic patients, there are combination of various adverse factors which affect the strength and health of the plantar foot. The end result of these various risk factors are neuropathy and tissue damage.
So unlike normal patients, the foot of a diabetic patient is not prepared to handle the pressure build-up on various areas of the plantar foot during various motions in view of its un-healthy state caused due to the said risk factors. Therefore, build-up of plantar pressure at particular areas of the plantar foot will aggravate the neuropathy or tissue damage thus leading to ulcer formation. One way to avoid or reduce the damages of such ulcer formation is by distributing the pressure build-up on the plantar foot to other non-pressure build-up areas by suitably off-loading the pressure
That apart, During leg movement, there is a interlink articulation of one or more of these bones which exerts pressure at various levels on the plantar surface of the foot. Therefore, the gait pattern of a person directly affects the pressure exerted on various areas of the plantar foot surface through the foot bone leading from the leg bone. It varies from person to person depending on his gait pattern and is not uniform for all. The pressure exerted on the various areas of the plantar surface of foot is called plantar pressure. This can be measured by a sensory device and processed by linking it to a computer.
Diabetic patients have a lot of foot related problems. The simplest formation which can lead to greatest complication and loss of limb is the formation of foot ulcers. It is known that have a reduced healing rate when diabetic patients compared to normal healthy persons. So the formation of a foot ulcer tends to progresses ultimately leading to gangrene and amputation of the phalanges or any other part of the foot or the leg itself in extreme cases.
Irrespective of the cause of formation of foot ulcer in diabetic patients, the exertion of pressure on the various areas of the plantar surface of the foot directly affects ulcer formation. This pressure exertion on the various areas of the plantar surface of foot is based on the gait pattern of the person.
When measuring the plantar pressure of a person, it can be seen that there are many pressure build-up areas on his foot. In some of these areas, the pressure build-up is very high. These areas are more prone to foot ulcer formation. By off-loading these pressure in the pressure build-up areas in particular in the peak pressure build-up areas, ulcer formation can be eliminated if not reduced. Off-loading of the pressure build-up is done by dissipating the build-up pressure to the surrounding areas of the plantar surface so that one particular point is not exposed to the pressure build-up which is the cause of ulcer formation.
Further, in diabetic patients, in view of neuropathy or internal tissue damage due to lack of blood supply or deficit blood supply, capillaries get clogged, leading to pressure build-up which aggregates the chances of tissue injury and ulcer formation. So all the more it is necessary to off-load the pressure build-up on the plantar foot surface of diabetic persons to avoid foot ulcers.
More than 15% of the ulcer results in amputation of foot or limb. The treatment of plantar ulcers is also very complex. So the prevention by off-loading of the plantar pressure surface by using customised insoles is a very effective remedy. The inventive customised split insole addresses this issue in a technically better and high cost effective manner as described herein.
Therefore peak pressure in plantar foot surface of diabetic persons is a common route cause for diabetic foot ulcer, leading to gangrene and amputation. To overcome this problem, many insoles for diabetic patients have been designed the world over. However, these insoles are subject to the following limitations;
Further, none of the existing insoles were split insoles focused towards effectively offloading the peak pressure zone wise.
The inventive product is a foot insole for use by diabetic patients. It is custom made to suit individual requirements. Each customized insole has five or six splits, five for persons with high arch and six for persons with normal or flat foot.
These splits are of specific thickness and have hexagonal or oval projections of specific dimension, height, elasticity and are placed on the first split.
The elasticity of the split insole is fixed zone wise based on the pressure build-up in that plantar area of the foot.
For high arch persons, two mounts are also provided on the fourth zone and for normal and flat foot persons in the fifth zone.
The invention is a customized split insole for use by diabetic patients as in
The human foot is classified into three types, namely, normal, flat and high arch foot depending on the arch in the middle inner side of the foot. This is depicted in
For a normal foot, the split insole is split into six different zones as in
The first zone is the bottom zone of the foot insole which acts as a support structure to hold all the other five zones on its top surface, as in
The second zone is located at the head of the split insole, in the phalanges region of the foot, as in
The third zone is located just below the second zone, in the metatarsal region of the foot, as in
The fourth zone is located just below the third with the fifth zone on its inner side, as in
The fifth zone is located on the inner curve of the foot, adjacent to the fourth zone, as in
The sixth zone is at the bottom of the foot insole in the heel region of the foot, and below the fourth zone, as in
For a flat foot person, the split insole is split into six zones similar to the normal foot split insole as in
Similarly, for a high arch foot person, the split zone is split into five zones as in
Working:
The custom made split insole is inserted into the foot wear of the person or patient who is to use the same. He can start moving by wearing the footwear inserted with the custom made split insole. The split insole with the projections and elasticity offloads the pressure build up in certain areas to the other parts of the foot, avoiding concentrating of pressure at particular points of the foot which in due course lead to foot ulceration and in several cases to gangrene and amputation in the diabetic patients.
The distribution of peak pressure to the other parts of the foot is measured using the ‘Plantar Pressure Measuring Device’, which is a machine with a sensor pad used for pressure data collection for both static and dynamic situations. The peak pressure of the bare foot as measured by the ‘Plantar Pressure Measuring Device’ is as shown in
The distribution of peak pressure loads under bare foot and using the custom split foot insole is as illustrated in the following Table 1;
A graphical representation of the comparison of
The pressure build up in the various areas of each zone of plantar surface is as in
From the above Table 2 which is an analysis of
Therefore, pink and red colour is directly proportional to high risk ulcer formation, and poor healing and thereby leading to high possibility of gangrene formation. So the hexagonal and oval projections offload the pressure build up in the pink, red and yellow areas to the other normal, moderate or low pressure areas so as to offload the pressure build up in the said areas.
When a person is static wearing the custom made split insole, the peak pressure applied by his foot on the split insole would first be sensed in the fifth zone, then by the sixth zone, then by the third, second and fourth respectively, and then distributed to the entire foot, as shown in
The application of peak pressure in the bare foot and its distribution in the split foot insole, is as shown in
The above Table 3 describes the pressure values in kPa, which is followed by zone wise pressure point distribution for both bare foot and during custom split insole application. From the above, it is evident that the custom split insole increases the surface area of contact between the foot and the insole, thereby leading to offloading of the peak pressure from few particular points in the feet to the entire feet, thereby reducing stress concentration to the soft foot tissue and the nerve at those particular points, which is the major cause for foot ulceration in diabetic patients, whose, foot is already affected by peripheral neuropathy and tissue damage, due to concentration of peak pressure at a few particular points in the foot.
