DISCUSS BRIEFLY THE ADVANCES IN PROSTHETIC KNEE ?
A 3 INTRODUCTION
1 Below-knee (BK) prosthesis will typically consist of a custom-made socket, a pylon and a foot. Sometimes a suspension sleeve or harness may also be necessary.
2 The concept of constructing a below-knee prosthesis with side joints and a thigh lacer was set forth by the Dutch surgeon Verduin in 1696 and followed universally until the advent of the patellar-tendon-bearing prosthesis in the late 1950’s.
3 Although other innovations such as contact over the distal end of the stump, suction suspension, and “muley” sockets were introduced from time to time, they were never widely used, possibly because principles governing their use were not set forth in a systematic manner.
4 In 1957, the predecessor of CPRD, the Advisory Committee on Artificial Limbs, encouraged the University of California at Berkeley to study the problems of the below-knee amputee and to improve the then current management practices.
5 As a result, some of the leading prosthetists in this country were invited to Berkeley later in 1957 for the express purpose of examining in detail the prosthetics practices for BK amputees and rationales for those practices.
6 An analysis of the findings of that conference led to the development of the patellar-tendon-bearing prosthesis, known now as the PTB prosthesis.
7 The original version of the PTB prosthesis was a plastic laminate socket which was formed over a modified plaster-of-Paris model of the stump, and which contained a soft inner liner that contacted the entire surface of the stump.
8 The major weight was borne by the medial flares of the tibia and the patellar tendon.
9 No knee joints or thigh corsets were used, suspension being effected by a fabric strap around the thigh just above the femoral condyles .
10 The PTB concept was offered in formal education programs in this country and gradually gained acceptance, so that by 1961 slightly more than half of the below-knee prostheses provided in the United States were of that type.
11 The concept also has been accepted widely in other countries, and the PTB now is generally considered to be the standard prosthesis for below-knee amputations.
12 In recent years, research groups and individual prosthetists have introduced improvements to the basic concept.
13 Following describes the advanced practices in the management of the below-knee amputee that have been developed since the introduction of the PTB prosthesis.
FEATURES OF ADVANCED KNEE PROSTHESIS
1 The size and weight of these components is small enough so that they can be combined into a package comparable to that of a biological leg and they can duplicate all of its basic functions.
2The electric motors play the role of muscles.
3 The batteries store enough power so the robot legs can operate for a full day on a single charge.
4 The sensors serve the function of the nerves in the peripheral nervous system, providing vital information such as the angle between the thigh and lower leg and the force being exerted on the bottom of the foot, etc.
5 The microprocessor provides the coordination function normally provided by the central nervous system. And, in the most advanced systems, a neural interface enhances integration with the brain.
6 Unlike passive artificial legs, THESE legs have the capability of moving independently and out of sync with its user’s movements. So the development of a system that integrates the movement of the prosthesis with the movement of the user is “substantially more important with a robotic leg,” according to the authors.
6 Not only must this control system coordinate the actions of the prosthesis within an activity, such as walking, but it must also recognize a user’s intent to change from one activity to another, such as moving from walking to stair climbing.
FOLLOWING ADVANCEMENTS HAS BEEN MADE WHICH ARE AS FOLLOWS
A ) The Hard Socket
1 The original PTB socket design called for a lining of leather or Naugahyde backed by sponge rubber.
2 Perspiration caused problems in many instances, however, because Naugahyde does not “breathe” and leather deteriorates rapidly in the presence of sweat.
3 This problem prompted some prosthetists to eliminate the liner, and the “hard” PTB socket has become increasingly popular.
B ) The PTS Socket
1 The suspension strap for the PTB prosthesis, as designed originally, was usually satisfactory, but there were enough dissatisfied amputees to prompt a number of prosthetists to seek improved suspension methods.
2 In addition to developing different strap designs , several groups experimented with new configurations for the proximal border of the socket.
3 The research team at Nancy, France, introduced the “prothese tibiale a emboitage supracondylien,” popularly known as the PTS, in which the proximal border extends above the patella and the femoral condyles , thus holding the socket on the stump.
4 This concept was introduced into the United States by Nitschke and Marschall .
5 The technique may be used with or without a liner.
C ) Wedge Suspension Socket ( v imp - viva q )
1 Another attempt to improve upon the strap type of suspension resulted in the KBM (Kondylen Bettung Munster) prosthesis , in which a small wedge is inserted between the proximal area of the socket and the area of the stump along the medial condyles of the femur
2 Developed at the University of Munster, this concept was introduced into the United States by Fillauer and is now known as the supracondylar-wedge suspension system.
3 The wedge system may be used with or without a socket liner, but generally no liner is used.
D ) Air-Cushion Socket
1 In an effort to develop a socket that would permit the stump to bear the optimum amount of the weight load over its distal end, Wilson and his associates designed and developed the “air-cushion socket”
2 It reduces the magnitude of the vertical components of weight-bearing forces at other points on the stump.
3 The air-cushion PTB consists of an elastic inner sleeve (stockinet impregnated with silicone rubber) suspended from the level of the tibial tubercle in a rigid outer shell that is closed distally.
4 Stump support is provided by the tension of the sleeve itself and by the compression of the air in the chamber between the inner sleeve and outer cap.
5 the air-cushion version of the PTB is particularly useful for patients with very sensitive stumps.
6 the only disadvantages being that slightly more time is required to fabricate the socket and that few modifications can be made after it has been fabricated.
Porous Socket
1 In seeking ways to alleviate the problems caused by perspiration, the U. S. Army Medical Biomechanical Research Laboratory developed a porous plastic laminate.
2 Conventional epoxy resins and filler materials are used in the fabrication, but special care must be taken in controlling the proportions of the ingredients and in curing.
3 The first porous laminates developed by AMBRL were satisfactory for upper-extremity sockets, but they were not strong enough for routine use in lower-extremity sockets.
4 Subsequently, the technicians developed a fabrication technique using epoxy resins that overcame the major shortcomings of the earlier laminates.
5 In addition, the prostheses with porous-laminate sockets weighed less.
6 the two disadvantages cited-slightly increased fabrication time and greater difficulty in maintaining socket cleanliness-were far outweighed by the advantages.
FOLLOWING DEVICES FOR AK AMPUTATION REQUIRING MORE POWERFUL OR STRONG KNEE SUCH AS -
1 symbionic leg -
A ) is a completely bionic leg for above knee amputees which combines a microprocessor knee and foot seamlessly.
B ) This leg allows amputees to explore all terrains safely without the user needing to compensate in any way.
2 Subatmospheric Socket Technology
A ) Based on brimless tenchnology
B ) Brimless transfemoral sockets are more comfortable, feel more secure and are easier to manage, even in high activity.
C in this Flexible socket materials are used in a design that doesn’t push on the pelvis.
3 Genium knee
A ) has dynamic stability component
B ) has gyroscopic sensors
C ) is compact in size
D ) is battery operated - has 5 day battery life
4 Biom foot
A ) The BiOM technology platform is the first true personal bionics solution.
B ) By mimicking muscles and tendons, the BiOM Systems enable smooth, natural human movement.
C ) The artificial muscle power allows people to walk with the same gait and the same effort as non-amputees.
D ) TheBiOM Ankle Systeminstantly improves function, empowering people to do the things they want at their chosen speed with (1) less energy requirements, (2) decreased joint degeneration and (3) fewer aches and pains.
5 Power Knee
1 The first and only motor-powered prosthetic knee, the POWER KNEE works as an integrated extension of the user, designed to restore the power of lost muscles and symmetry of movement that is vital for those with limb loss.
2 POWER KNEE gives users the ability to cover greater distances than they could previously.
3 Confidently negotiating obstacles and inclines has never been easier. With the POWER KNEE ascending stairs foot-over-foot is now possible
6 C leg
A ) designed by ottobock
B ) is driven by microprocessor technology
C ) improves gait by improving knee flexion angle
D ) it adjusts automatically , thus preventing the need for muscular effort
E ) improves peak swing phase knee flexion angles