Dynamic response foot

this slide is about prosthetic dynamic response foot.

1. DYNAMIC RESPONSE FOOT DIBYA RANJAN SWAIN MPO 1 st year SVNIRTAR

2. INDEX: Human feet and its function Prosthetic foot and its classification Dynamic response foot History Components Factors for selection of DRF Biomechanics Classification of dynamic response foot Pros and cons 10.Controversies 11.Conclusion

3. Human feet and its functions: The feet are the flexible structures of bones, joints, muscles, and soft tissues that let us stand upright and perform activities like walking, running and jumping. Muscles, tendons and ligaments that run beneath surface of the feet allow complex movements needed for motion and balance. It produces balance and propulsion along with providing foundation for the rest of the body.

4. Prosthetic foot: The primary purpose of prosthetic foot is to serve in place of anatomic foot and ankle. The function of prosthetic foot and ankle unit is to allow smooth and natural transition of the body during walking. Functions : Joint simulation Shock absorption A stable weight bearing BOS Muscle simulation A pleasing appearance

5. CLASSIFICATION STRUCTURALLY:

6. FUNCTIONALLY FOOT

7. Dynamic response foot Introduction: Dynamic Response Foot stores and releases energy with ambulation. They function as sophisticated springs that cushion at initial contact and provide propulsion at terminal stance, enhancing the ability to walk long distances, run , and jump. Individuals with more-active lifestyles require dynamic response feet.

8. COMMON FEATURES : Good shock absorption during heel strike. Dynamic roll over action during ambulation. Elastic axial compression under load. Compensation for uneven walking surfaces. Flexible restoring force of the forefoot during fast walking and running. Pleasing cosmetic appearance.

9. History Initially, the conventional foots like SACH foot, single axis foot etc. were used adversely for most of the amputees besides of the activity level and interest. Mainly amputees having athletic lifestyle had no other options. As the conventional designs were too stiff to permit comfortable ambulation at more then a moderate pace for high level activities and similar recreational activities.

10. Finally, in 1984 American inventor Van Philips introduced first ever dynamic response foot as Flex foot. He( born in 1954) lost his leg below the knee at the age of 21 who was an athlete himself. For a young and active individual the options were stiff and uncomfortable. So, he ultimately created a foot made from carbon fiber which stored kinetic energy from wearers steps as potential energy, like a spring.

11. Factors for selecting dynamic response foot: Amputation level Age Weight Foot size Activity level Economical conditions Environmental conditions Occupation Goals and recreational activities

12. Amputation level: - There is no certain limitations according to the length of the stump as long as the lower limb muscles are strong and give a good range of motion. - For ankle disarticulation ( symes ) specially designed foots are present in the form of low profile DRF - For partial foot amputations only carbon fiber foot plates are present but they don’t come under DRF - For specific high energy sports with strong demands, different types of dynamic response foot are present along with specified keels.

13. Age: - Mainly for adults are specified with high energy activities who need unrestricted foot motion for those who want not just standing and compromised walking, as after certain age the muscles weaken which cannot controlled the energy given off by the foot. - But, people with very good musculature and strength who easily don’t compromise with the age, use this foot in a very sufficient manner.

14. Weight - Specific weight is also considered for using dynamic response foot as the spring are used where they can provide a balanced push off at an optimum shape and position as well as transforming the body weight to the ground. - If weight is too much, the push off will not be enough - If weight is less, the compression will not be enough - The ideal weight is specific for different designs

15. Foot size : according to the measurements Activity level :

16. Economical conditions: surely the dynamic response feet are expensive then the conventional designs but there are so many variables that can be accepted by amputees with different economical conditions. Environmental conditions : these kind foot are mainly designed for athletic activities so good for smooth as well as uneven and inclined surfaces but show some laxicity in muddy, sandy and humid environments.

17. Occupation : for persons with official or other lower activity level occupation this foot is not ideal. having occupations were activity level is k3 and k4, the dynamic response foot provides great support.

18. STRUCTURAL MECHANISM OF DRF Hybridizing the properties of different classes, primarily by combining dynamic response feet with multi-axis attributes. The traditional classification system has become outdated. Proposed subsets could include: Forefoot keel Heel lever Hind-foot roller Flexing strut Forefoot inversion/eversion Multi-axis hind foot Integrated shock

19. Forefoot keel The forefoot keel is characteristic of the most basic ESAR foot/ankle mechanism with any number of materials and configurations. The forefoot keel can be a single-bladed member or consist of multiple separate members. Stiffness is directly dependent on the cross-section, material, keel length, and geometry. Some designs use multiple layers that collapse progressively. Others use a urethane sandwich, which has a smoothing effect on the load progression.

20. Heel lever The heel lever emulates the heel rocker, which contributes to load acceptance and ankle plantar flexion characteristics. Many foot/ankle mechanisms simply use a cushion heel that simulates plantar flexion by compression. Such as flexfoot , a heel lever projects posteriorly from the forefoot keel or midfoot attachment, and often provides stiffer support than a cushion heel. Recent designs have used multiple levers, linkages, urethane bumpers or a urethane sandwich to simulate the progressive stiffness of the anatomical foot and ankkle .

21. Hind foot roller A hind foot roller mechanism used by many foot/ankle mechanism uses a rocker element mounted on a footplate to approximate the ankle rocker from loading response to mid-stance. This mechanism emphasizes the rotary motion of the ankle rocker to ease the transition from loading response. When configured as a complete circular mechanism that wraps superiorly, the hind-foot roller can also function indirectly in shock absorption by emulating mid-tarsal dorsiflexion. Excessive rocker function in late mid stance would be non-physiologic, leading to a loss of support in late stance.

22. Flexing strut A flexing strut proximal socket attachment originated with the flex-foot design. Incorporate the forefoot keel in one integrated structure. The strut is usually a wide rectangular cross section. Using continuous fibers in the strut composition insures maximum flexibility and strength. All these flexing strut designs offer the greatest amount of energy return. The longer the continuous fibers are in the lay-up of the composite, the greater the amount of bending flexion that can occur.

23. Forefoot Inversion-Eversion Forefoot inversion-eversion split-toe design. Other designs are more integrated, molding different durometer materials or members together within the foot, so there are not necessarily articulating parts. Some designs create a forefoot composite urethane sandwich. The damping characteristics of the fore foot may limit the desired energy return.

24. Multi-axis hind foot A multi-axis hind foot as an articulating component with urethane rubber bumpers, bushings, spherical snubbers , large rings to dampen motion. Separate modular ankle unit that can be used with a variety of prosthetic feet, or it may be integrated into the foot/ankle mechanism itself. Multi-axis articulating designs often need regular maintenance and servicing. Some variants extend the urethane sandwich from the forefoot to the hind foot.

25. Integrated shock absorbers It incorporates shock absorbers in parallel or series configuration. A series confg . Is usually found with a damper more proximal to the spring-like foot. A parallel design has a damper and spring at same level. The telescoping nature of many shock absorbers considered non-physiologic. Design will be able to provide more variable stiffness or flexibility characteristics. Future components are sure to continue this blending of qualities to provide greater foot function and movement. Absorbers in series Absorbers in parallel

26. FUNCTIONAL MECHANISM OF DRF During the gait cycle, 1.At heel strike, The dorsi -flexion movement of the foot allows the keel to compress or distort The keel which acts as a spring( leaf spring or coiled spring), absorbs kinetic energy. Helps in shock absorption

27. 2.During mid-stance, the kinetic energy is converted in static energy there by giving stability and balance to the body weight. Inversion and eversion is simulated by flexibility of the keel and some designs also have split in the middle to accommodate it. As the tibia or the shin starts to advance, the keel begins to bend and foot starts to dorsiflex .

28. 3.During heel off , As the dorsiflexion advances, the energy again transforms and aids in forward propelling. The heel rise is controlled by the stiffness of the keel and when weight is transformed onto forefoot, the keel extends all the way to the toe area. The flexible keel eliminates the need for rocker effect and provides a smooth roll over. Gives the wearer a subjective sense of push off in pre-swing Helps in the initiation of the swing phase Gives the fine trajectory to the foot during swing phase.

29. The shank and foot deflection pieces are linked using spectralon fibers, which holds them at their shortest length and the system is able to retain the foots absorbed energy. By attaching the deflexion plates around the axle, the system ensures the linear GRF is converted to the torque. while the lower plate controls energy during normal to moderate walking and jogging the upper deflection plate resists the torque and absorbs energy during high level activities like running etc and helps the foot to return to equilibrium after each successive step.

30. ANATOMICAL FOOT The PF and DF of the foot is carried out by specific group of muscles and are also controlled by antagonistic group of muscles in very controlled manner. CONVENTIONAL DRF There are mainly 2 deflection plates, the lower one controlls the foot during normal to moderate activies and the upper one specially controlls the lower plate during vigorous activities as an antagonistic muscle group. ADVANCED DRF Here , along with the deflection plates, extra components are added like bumpers, cylinders and electrical motors which control the higher torques more efficiently. HIGHER PROFILE DRF These designs only depend upon the stiffness of blade and the architechture ( C & J) to controll the torque.

31. Classification of dynamic response foot: EARLY DRF ARTICULATED DRF ADVANCED DRF

32. Early drf designs : Flex foot: The first dynamic response foot invented by Van Philips in1984. made from carbon fiber with leaf spring design. It is a long keel design where the foot is directly attached to the socket or to the knee portion of the prosthesis. It requires sufficient space between residuum and floor.

33. The shock absorbing function of the carbon fiber along with active heel reduces the stress on the proximal joints, the knee, the hips and the spine while walking or participating in higher impact activities. The full length keel permits flex foot users to spend equal time on their prosthetic and sound limbs, enabling a full length step eliminating drop off.

34. Flex foot cheetah: Following the design of flex foot, in 1996 flex foot cheetah was created also by V an Philips under Ossur . About 90% of the athletes in Paralympics wear flex foot cheetah and variations. It have been worn by Oscar Pistorius and other athletes. Made from carbon fiber along with epoxy polymer. The blade is a combination of 30 to 90 layered sheets of carbon fiber depending upon the weight of the person which reduces air bubbles that can cause breaks

35. Seattle foot: Seattle foot was introduced by 1981 in a course organized by American Orthopaedic Association. The main concept of the foot is to stores energy at the initial part of the stance phase and releases the same at push off. The keel is made up of Derlin like a multileaf automobile suspension spring with anterior deflection plate. This is the 1 st energy storing foot and commercial production strated in october 1985. Materials Used: Derlin Kevlor toe pad PU foam shell

36. Springlite Foot: The Springlite foot is simmilar in design to the flex foot and consists of two layers of carbon and fiberglass filaments surrounded by a soft cover. Indication : Vigorous sports activity Advantages: Light weight Allowed vertical jumping. Provides med. And lat. Stability Symes and pedeatric models are avaliable .

37. Sabolich foot: - Developed by John Sabolich of Sabolich prosthetic center , Oklahoma. - The foot design resembles the human anatomy of the longitudinal arch with a bridge like structure fabricated from Delrin . - During heel contact the energy is stored as the person progresses to foot flat during mid-stance the arch is flattened again and energy is released later in the gait cycle. - This assists in propelling the CG up and forward. - The foot is custom manufactured according to the activity level and weight appropriate for the amputee.

38. Carbon copy ll : - Mauch laboratory with Ohio willow wood designed a foot shell for mauch hydraulic ankle unit. With engineered carbon composite ke el they released carbon copy I. - But, after further development, carbon copy II was the first cosmetically appealing energy storing foot brought to market.

39. - The keel is composed of two strong deflection plates, made out of carbon graphite plate. - The longer deflection plate terminate at the distal IP joint. - Shorter upper plate is activated under high load. - Plates are available in 3 levels of resistance. Provides little medio -lateral stability.

40. Quantum foot: - it was introduced in September 1988 by Hanger. - The keel is in the form of spring module consisting of a lower and upper deflection plates attached to ankle base from where the plates project forward to the MTP joints and backward to the heel. - The lower plate stores and returns energy during last half of the stance phase. - The upper plate acts as a spring in case of high forces .

41. C-walk: - A new generation innovative design made from carbon composite dynamic response foot which provides walking at different speeds, walking uphill or down heel with a secure feeling and harmonious roll over on uneven grounds. - It consists of, C-spring(coiled) Base spring Control ring Heel elements

42. PROPERTIES : Large controlled PF up to 12degrees Multi axis motion for uneven surfaces Reduced strain on sound leg Cushioned heel strike Physiological rollover Harmonious transition from stance to swing Comfortable walking uphill and down hill.

43. ARTICULATED designs : - These feet are the combination of multi-axial ankle with a dynamic response foot, in an effort to offer the advantages of both concepts. Total concept foot: - Developed by OSSURE, Sweden -Provides 10 degree DF to 25 degree PF -Heel height from 0-2 inches

44. Advanced DESIGNS: College park true step foot: - It designed to mimic the anatomic foot and ankle. - It contains, 1.PF and DF bumpers 2.Ankle alignment bushings 3.The bumpers are easily changed to accommodate variable weights, thereby providing the correct resistance for smooth gait.

45. Luxon max foot: It incorporates computerized knee or c-leg Pathfinder foot: - It combines with adjustable pneumatic heel spring with two carbon fiber springs for dynamic response. Proprio foot: An adaptive microprocessor controlled ankle Have different types of modes Weatherproof Controlled by smart application

46. COMPARISON OF PROSTHETIC FOOT PROSTHETIC FOOT INDICATION ADVANTAGES DISADVANTAGES PICTURES Single axis Enhances the knee stability K1 Adjustable bumpers Rapid PF Increased wt Non cosmetic Debris can enter the jt. Multi axis Accommodates uneven surfaces K2 Allows multidirectional motion Good shock absorption Increased wt Less stability on smooth surfaces SACH foot General use K1 K2 Large variety of heels Reliable Less maintenance Limited dorsiflexion due to rigid keel No propulsion at terminal stance.

47. CONTD Flex foot Vigorous sports K3 K4 Light wt Vertical jumping Med- lat stability high cost Complex fabrication and alignment Difficulties in hell height changes Spring-lite foot Same as flex foot K3 K4 Same as flex but less expensive Same as flex Seattle foot General sports Active wearer K3 K4 Dynamic response improves cosmetic appearance Increased weight

48. CONTD Carbon copy II Active wearer Smooth stance roll over K3 K4 Good med- lat stability Light weight Increased cost College park true step High activity level K3 K4 Increased stability Adjustable bumpers Increased maintenance Expense Avl only for adult sizes and low heeled shoes C- Walk High activity level Active patient K3 K4 Large controlled PF up to 12degrees Increased maintenance Expense Increased wt

49. Controversies: Do dynamic response foot give the athletes some kind of unfair advantages ? In 1980s, initially a J-shaped foot was introduced which was build out of stiff carbon fiber meant to imitate the strength and springiness of the anatomical calf-muscles with flexible-deep-firm fitting socket to minimize energy loss. Then Ossure , get rid-off the heel spring making it fully j shaped with increased stiffness and came out with flex sprint.

50. IFAA - international federation of athletic association , changed the rule: ‘Use of any devices that incorporates springs, wheels or any other element that provides the user with an advantage over another athlete not using such device is not permissible’. But, runners with prosthetics run differently than able bodied runners. Then, a group of German researchers worked with Oscar Pistorius analyzed that, Prosthetic DRF store and release energy more efficiently then actual anatomical muscles.

51. But, they did not measured any metabolic factors like heart rate, oxygen consumption etc. It was based only on kinetic factors. Again, researchers of RICE university did a follow-up study focused on metabolic factors performed with both types of runners and came out that; Yes, the prosthetic foot gives different mechanics but does not gives physiologic edge which the Germans predicted. This study ruled IFAA decision, and allowed Oscar Pisturious to run in the events.

52. Study on, running economy with heart rate response showed that; running with prosthetic foot is better in everything due the groundbreaking change in the design of foot .

53. Again, in 2018 studies showed that, as the angle of impact increases, the stiffness in the spring decreases. Which gave rise to a new question, Does different designs give more advantage then others? As a result which again AFAA announced,

54. New studies with bilateral trans- tibial amputees variations like, different models, height, stiffness and shape found that, The only thing that influenced speed is, the shape of the blade.

55. Conclusion: By February 2020, IFAA still not allows to use any such devices. But, Able and disable runners have different biomechanics The disable runners compromise in physiology Mostly all the studies are based on small sample sizes as its difficult to get specific samples the future goal of the athletes still counts on .

56. REFERENCES A publication of the amputee coalition of america in partnership with the U.S Army Amputee patient care and programme . Michelle M. Lucardi , Orthotics and Prosthetics in rehabilitation, 2 nd edition, 422 Perry J. Gait Analysis ; Normal and Pathological function. New York, Mcgraw-Hill,1992, 11-16. www.collegepark.in www.ottobock.com www.endoliteindia.in

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