Pre- prosthetic training
After the patient has an amputation in the lower extremity, they will remain in the acute care hospital until they are medically stable. After that time they may be either transferred to a skilled nursing facility (SNF), acute inpatient rehabilitation facility or discharged home with homecare services. The patients that are discharged to acute rehabilitation facilities often have better functional outcomes than those patients with any other discharge destination.(1) During the initial time after the acute care hospital the focus is to determine if the patient is a candidate for a prosthesis based on their functional level, potential for progress and to prepare the residual limb for a prosthesis if the patient is a candidate. This includes training in mobility and activities of daily living (ADLs) without the prosthesis, education in skin care, muscle strengthening, pain reduction and management and also shaping and shrinking of the residual limb. Specifically, early range of motion and desensitization of the scar from the amputation are important. There are many different options for discharge after the acute hospital care stay, however, receiving inpatient rehabilitation care immediately after acute care was associated with reduced mortality, fewer subsequent amputations, greater acquisition of prosthetic devices, and greater medical stability than for patients who were sent home or to an SNF.(1) Acute inpatient rehabilitation facilities stabilize chronic problems such as renal failure and diabetes and optimize surgical wound management which may lead to improved outcomes.
Prosthetic Evaluation
Initial evaluation to determine if a patient is a candidate for a lower limb prosthesis should include the following assessment of the patient’s history:
The patient must also be physically and mentally evaluated to determine the appropriate prosthetic prescription, complete assessment includes:
Based on the above gathered information, physical examination, and potential for progress, the amputee patient is classified to a particular functional level. The K levels were adopted by the federal government to clarify which lower limb prosthetic components (knee, foot, and ankle) should be used for patients depending on their functional levels. The higher the K level the more potential for prosthetic ambulation.
K levelDescriptionK0Does not have the ability or potential to ambulate or transfer safely with or without assistance, and a prosthesis does not enhance quality of life or mobility.K1Has the ability or potential to use a prosthesis for transfers or ambulation on level surfaces at fixed cadence. Typical of the limited and unlimited household ambulator.K2Has the ability or potential for ambulation with low-level environmental barriers such as curbs, stairs, and uneven surfaces. Typical of the limited community ambulator.K3Has the ability or potential for ambulation with variable cadence. Typical of the community ambulator who can traverse most environmental barriers and has vocational, therapeutic, or exercise activity that demands prosthetic utilization beyond simple locomotion.K4Has the ability or potential for prosthetic ambulation that exceeds basic ambulation skills, exhibiting high-impact, stress, or energy levels. Typical of the prosthetic demands of the child, active adult, or athlete.The initial prosthetic fitting
When preparing a patient’s residual limb for a prosthesis the process includes healing, shrinking and shaping the residual limb appropriately with the use of ace wraps and eventually an elastic shrinker. During this period often the patient’s residual limbs are protected in a rigid protective device.
The goal of the shrinking and shaping process varies depending on the type of amputation. When there is a plateau in the day to day change in shape of the residual limb the patient with a lower-limb amputation is prescribed and measured for their initial prosthesis. In the past, this was referred to as preparatory or temporary prosthesis, although with the advancement of prosthetic technology this prosthesis is still custom made and can be used for quite some time. It is designed to be strong and can be adjusted for alignment, fit, componentry, etc. With this prosthesis, the patient typically will work with physical and occupational therapists with the goal of achieving independence in ambulation and ADL’s with the prosthesis. While the patient uses this initial prosthesis, the residual limb is expected to continue to shrink, but at a slower pace, and sometimes the shape will change as well. The prosthetic socket often needs to be replaced as the residual limb shrinks, usually within the first 6 months to a year after amputation. When needed, a “definitive” prosthesis is prescribed. This term was often used in the past to describe when the socket, alignment and componentry were no longer requiring change, so that a cosmetic cover could be applied. Most patients at this time choose not to cover their prostheses but to leave the componentry visible. The general public’s acceptance has grown, and this is much more practical for prosthetic management, as continued changes are often necessary. Currently, the semantics of “temporary” and “definitive” prosthesis have fallen by the way-side, as most patients will use their initially prescribed prosthesis until a new one is needed.
The prosthesis prescription
The level of amputation determines which components of the lower extremity prosthesis will need to be prescribed. The two most common lower extremity amputations are the transfemoral (above the knee- AK) and the transtibial (below the knee- BK). The major components of a lower limb prosthesis include the socket, interface (where the liner contacts the skin), suspension, pylon/frame, knee unit (if applicable), foot/ankle complex, hip joint (if applicable).
Prosthetic interface: The interface is where the prosthesis contacts the residual limb; this can be made of either a soft or hard material. Some common interface options are: pelite liners, urethane liners, thermogel/gel liners, silicone liners, or a hard interface directly with the socket.
Pylon/frame: The prosthetic frame is the method of connecting the prosthetic components together. There are two main types: exoskeletal or endoskeletal. The exoskeletal construction is infrequently used in current practice. This design uses a rigid exterior lamination from the socket down and has a light-weight filler inside. The endoskeletal construction is the most commonly used type of prosthetic frame. This construction uses pipes called pylons to connect the prosthetic components. The pylons can be constructed from aluminum, titanium, stainless steel or any hybrid of these materials.
Hip disarticulation and hemipelvectomy prostheses
The socket encases bilateral iliac crests in the hip disarticulation patient and utilizes abdominal compression in the hemipelvectomy patient. These prostheses must include a hip joint, which may be a ball-and-socket joint or single-axis.
Transfemoral Prostheses
Transfemoral Socket Designs
1. Quadrilateral socket is an older socket design that is relatively narrow anterior-to-posterior, with a posterior shelf to enable weight bearing on the ischium.
2. Ischial containment socket is more ovoid in shape, with a smaller mediolateral dimension. The posterior and medial walls encase the ischial tuberosity. When compared with the quadrilateral design, the ischial containment socket may distribute pressures more evenly. There are also several variations of this socket, including a flexible inner socket within a rigid frame. One example is the comfortflex socket from Hanger Clinic.
3. Sub-ischial socket the trimline of this socket falls distal to the ischial tuberosity and relies completely on the thigh musculature for weight bearing.
Transfemoral Suspension
1. Suction is a common choice for transfemoral suspension, utilizing a one-way valve and liner with concentric rings.
2. Elevated Vacuum Suspension is a derivative of the suction suspension; air is actively drawn from within the socket environment.
3. Distal suspension with a pin or lanyard is another option.
4. A pelvic band or silesian belt may be used as the primary suspension or as auxiliary suspension in some patients.
Prosthetic Knees
Knee disarticulation prostheses
This level of amputation preserves the femoral condyles, which allows for supracondylar suspension and a long lever arm. However, the functional length of the thigh becomes much longer when the socket and prosthetic knee are added. This can be partially compensated for by utilizing a low-profile polycentric knee.
Transtibial Prostheses
Transtibial Socket Designs
1. Patellar tendon-bearing socket has an inward contour that uses the patellar ligament as a partial weight-bearing surface. Despite the name, this socket design aims for a total-contact fit and involves weight-bearing throughout the pressure-tolerant areas of the residual limb, including the medial tibial flare and the popliteal fossa region. Raising the proximal trim line of the medial-lateral dimension to above the condyles, additional support for the residual limb is provided with added suspension this raised trim line is classified as a supracondylar/suprapatellar socket.
2. Total surface-bearing socket is designed to distribute pressure more equally across the entire surface of the residual limb, including carrying some of the load on pressure-sensitive areas.
Transtibial Suspension
1. Supracondylar cuff or strap may be helpful for patients with very short residual limbs or may be used as auxiliary suspension in some patients.
2. As noted above, a supracondylar/suprapatellar socket provides supracondylar suspension by encompassing the medial and lateral femoral epicondyles within the socket.
3. Supracondylar Pelite liner with compressible or removable wall: pelite is a type of expanded cross-linked sponge foam which is shaped to fit to residual limb to provide cushioning inside the socket.
4. Auxiliary suspension sleeve, provides additional support to the primary suspension and holds the prosthesis on with material such as neoprene or gel type sleeves.
5. Liner with pin-locking mechanism, a silicone liner with a distal pin system is donned over the residual limb. The pin system consists of a metal or plastic disc with a metal pin in the center. The pin then locks into the bottom of the prosthetic socket.
6. Suction with or without liner, utilizes a one-way valve and slight negative pressure to hold the prosthesis on the residual limb. Another option is a special liner with several concentric rings to create the seal; this eliminates the need for an additional suspension sleeve.
7. Electric vacuum pumps: Suction creates a very secure fit but can be compromised by small holes in the suspension sleeve; the suspension sleeve also increases bulk behind the knee, especially in positions of knee flexion.
8. Thigh corset with side joints may be considered in long-time prosthesis wearers who prefer this style, or those with poor mediolateral stability due to derangement of the knee ligaments. This is an older mode of suspension. It is sometimes considered where additional off-loading of the residual limb is needed such as in a patient with a hypersensitive residual limb, or a residual limb that does not tolerate full weight bearing
Symes and ankle disarticulation prostheses
This amputation level has the advantage of a long lever arm and allows some distal weight-bearing without a prosthesis. The distal residual limb is bulbous due to the presence of the malleoli. Because of the increased length of the residual limb, fitting a prosthetic foot can be challenging. Fortunately, there are several options of low profile feet.
Prosthetic Foot/Ankle
Partial foot prostheses
The various levels of foot amputations may require toe fillers and shoe modifications. Many studies have demonstrated that these can assist in gait mechanics and prevent skin break down and peak plantar pressures specifically studies have recommended: the full length shoe, total contact insert, and Rigid Rocker Bottom sole for most patients with Diabetes Mellitus and Transmetatarsal amputations.(4) One group also described the benefits of a transmetatarsal prosthesis with a carbon fiber plate that improved functional outcomes as well.(5)
Additional componentry considerations
Vertical shock pylons decrease the impact of initial contact.(6) Torsional adapters allow motion in the transverse plane to simulate tibial rotation.(7)
The Genium
by Otto Bock has several features that have biomechanical advantages over the older microprocessor knee designs, including the ability to ascend stairs step over step. A military-grade version of this knee joint, the X3 is ideal for physically demanding occupations, an active family life, swimming, sports activities, and situations where you encounter water, dust, sand, dirt or grime.
Microprocessor feet are becoming more widely used, as well as those that are powered.
Osseointegration is the practice of placing a titanium implant directly into the long bone of the residual limb after amputation, extending outside of the skin. The prosthetic limb can attach directly to it, eliminating the socket-skin interface. This is still in the development stage in the United States and mostly performed in the United Kingdom, Germany, and Canada.
Aosuo Medical Product Page
Sports prostheses can include specialized components for running, cycling, swimming, and many other activities. Prescription and fabrication of these prostheses requires close collaboration between the physiatrist, prosthetist, and patient, in order to meet the demands of the athletic activity and the patient’s desired outcome.
3D printing and Lower extremity prosthetics
3D printing for prosthetic fitting and fabrication began with Ivan Owen, a Bellingham, Washington puppet-maker and Richard Van As, a South African carpenter that had lost some of his fingers. The two developed the first 3D printed prosthetic hand. Initially, 3D printing began with upper extremity prostheses, recently this has progressed to lower extremity prostheses. Currently, some components of the lower extremity prostheses are able to be 3D printed. SHC Design is a Japanese company with a focus on manufacturing prostheses using 3D printing technologies.(8) Another company Art4Leg is designed to work with an amputee’s current, standard prosthetic leg and designs custom artistic covers for lower extremity prostheses.(8)
Bionic prostheses
Össur’s commercially available Bionic prostheses are smart limbs capable of real-time learning and automatically adjusting to their user’s walking style (gait), speed and terrain.(9) Walking with a Bionic prosthesis, however, still typically requires some conscious, intentional thought from the user. Recently, two amputees were the first people in the world able to control their Bionic prosthetic legs with cortical control. This was accomplished via tiny implanted myoelectric sensors (IMES) that have been surgically placed in their residual muscle tissue.(9) The IMES, instantaneously triggers the desired movement, via a receiver located inside the prosthesis. This process occurs subconsciously, continuously and in real-time.(9)
Cambridge Bioaugmentation Systems (CBAS) and their prosthetic interface
The Prosthetic Interface Device (PID) is like a “USB connector for the body”.(10) This integrates with a residual limb through direct implantation into the bone (osseointegration) and electronic connection with the nerves. The hope from this company for this device is to allow full functionality through conscious control of the prosthetic limb and allows sensation to be fed back to the brain.(10)
Bradeigh S. Godfrey, MD. Lower Limb Prosthetics. 9/20/
Karen M. Pechman, MD
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Around , a flexible plastic shell type orthosis was introduced to provide dorsi-flexion assist during the swing phase of gait. Since then, polypropylene has become the most widely used and accepted material for this application.
However, many other types of sheet plastics are being used by orthotists and prosthetists today. Some plastics have more applications than others, but many types of plastics seem to have a particular characteristic which lends itself well to certain disabilities or even to certain body segments.
The decision to use one type of plastic over another, or to use plastic at all, is being determined more frequently by the orthotist and prosthetist. This decision has been placed in the hands of these practitioners by physicians and other health professionals, because it is felt that this could best be decided by the practitioners who work most closely with these materials.
It is important to remember that in many situations, when treating a disability orthotically, any one of several different types of plastic may be utilized. The particular plastic chosen may be a subjective decision based on prior experiences. However, in any event, the responsibility of this decision is one that mostorthotists and prosthetists have willingly accepted.
In order to communicate some basic knowledge of sheet plastic technology to orthotists, prosthetists, physicians, therapists, and other professionals, this article is presented as a guide to the variety of sheet plastics now available. This list may serve as an accurate reference for those sheet plastics most widely used in orthotics and prosthetics.
At the Physical Medicine and Rehabilitation Department at the Hospital of the University of Pennsylvania, orthotics has advanced to incorporate the vast utilization of thermo-plastics. The techniques applied to fabricate an orthosis require that a negative impression of the body segment be taken. After specific laboratory assembly procedures, a custom molded orthotic device is created for the patient's disability. The terminology used to refer to these orthotic devices includes:
Prosthetics differs in the terminology used, but the techniques performed in developing a functional prosthesis are similar to those as practiced in orthotics.
A negative impression is taken of the residual limb and, from that mold, a socket is fabricated to fit the residual limb intimately. The goals achieved by a proper socket fit are maximum function and comfort for the amputee.
The type of prosthesis is referred to as either an endoskeletal or an exoskeletal. The terminology commonly used today includes:
Orthoplast is possibly used in orthotics more frequently than any other sheet plastic. Occupational therapists, orthopedic technicians, and physicians like this material because it can be applied directly to the patient, thereby making a negative impression on the patient unnecessary. Orthotists will use this material often when asked to fabricate orthoses used in the treatment of fractures.
Orthoplast may also be incorporated in a device which may need to be flexible and custom molded over two positive models for an improved fit. However, it is usually not the preferred material because of its shorter life expectancy when compared to the other, more durable flexible sheet plastics. Even so, many orthotists will choose to use orthoplast in the orthotic treatment of scoliosis with a Milwaukee style orthosis or a T.L.S.O. "body jacket" because the material can be easily adjusted with a heat gun even after the finished orthosis has been worn by the patient.
Fig. 1
A rigid plastic, Kydex is an excellent reinforcing material over soft plastic foam. It is also used as the supporting material in Philadelphia collars. Some orthotists prefer its use in upper extremity applications such as the wrist-hand-orthosis with or without articulation at the wrist. In many locales, it is popular for use in spinal orthotic prescriptions. Kydex can be reheated and changed repeatedly over its long life.
Nyloplex is routinely used in upper extremity orthoses. Its use, however, often depends on the practitioner's past training. For example, Nyloplex is popular with practitioners graduated from New York University, while those trained at Rancho Los Amigos might prefer aluminum, which is most frequently used there. Nyloplex is cosmetic and can be reheated repeatedly like Kydex. It is also transparent and durable. Moreover, it has been used for spiral and hemispiral AFO's, but durability is still a problem in these applications.
Standard Grade Polypropylene is the most widely used sheet plastic in orthotics and prosthetics. In most cases, the nonarticulated AFO is fabricated from polypropylene and is referred to locally in Philadelphia as a "MAFO" (molded AFO). It must be remembered, however, that not all MAFO's are solid ankle designs, nor are all nonarticulated MAFO's flexible at the ankle trim. Since metal joints are frequently used when treating certain disabilities, I would emphasize that the metal hinge be attached to the more rigid polypropylene sections as opposed to, for example, the flexible polyethylene anterior shell.
Polypropylene is the strongest sheet plastic available which can be formed over a positive model. Common orthotic uses include upper extremity devices designed for long term use, MAFO's, KAFO's, CTLSO's, TLSO's, pelvic bands and joints, pelvic girdles, and other innovative devices where rigidity and durability are essential.
Fig. 2, Fig. 2
Co-polymer is more rigid after the forming process than orthopedic grade polypropylene, but is slightly more flexible than standard grade polypropylene. Many practitioners appreciate the choice between the slightly different characteristics of these three materials, while others will routinely choose only one type.
Co-polymer would be the plastic of choice when custom molded orthoses are prescribed for permanent orthosis wearers such as post-poliomyelitis patients. In this situation, co-polymer meets the critical needs of durability, cosmesis, light weight design, and intimate fit. I emphasize that the decision to use co-polymer or to use polypropylene may not always be an obvious one for the orthotist formulating the orthotic design.
Orthopedic grade polypropylene is standard grade polypropylene with an additive which makes it more flexible and, therefore, more durable under stress. However, this additional flexibility can be undesirable when maximum rigidity is required. A careful evaluation at the initiation of orthotic treatment is essential to determine the most appropriate material and design. When a custom molded fracture orthosis is prescribed for an active patient, orthopedic grade polypropylene is an excellent choice, which will diminish the incidence of rupture in high stress areas. If desired, a soft foam plastic interface may be positioned on the positive model, and the hot polypropylene will adhere to it during the vacuum forming process.
The most frequent use for ortholen is in the posterior leaf spring type AFO, which is usually used when weak dorsiflexors coexist with active plantarflexors. Durability at the posterior section of the orthosis is questioned by some practitioners who, therefore, prefer not to use this plastic. Subortholen is a new material, which is reported to be more durable than ortholen.
Vitrathene is a pink colored form of polyethylene used by some orthotic practitioners, who feel that this plastic is more durable than the low density polyethylene. The most frequent use of this material is in the custom molded low profile T.L.S.O. "body jacket," as it is commonly called, used in the treatment of idiopathic scoliosis or for stabilization of the spine following surgical treatment, such as Harrington rod placement. In addition, Vitrathene could be used for any upper or lower limb orthoses where flexibility is desired, but caution should be taken when considering this material where high stress conditions may be expected or where rigidity is essential.
Similar in characteristics to Vitrathene, polyethylene is next to polypropylene in popularity with orthotists and prosthetists. One of the reasons the Prosthetic and Orthotic lab of the Hospital of the University of Pennsylvania prefers polyethylene to vitrathene is the color matching which is possible when combining both polyethylene and natural polypropylene in an orthosis.
Other important reasons for its popularity are cost effectiveness, variety of different thicknesses, flexibility and availability through most local plastic manufacturers. It is also relatively easy to work with during fabrication, provides a pleasant appearance, and is easier to smooth the edges on than with many other sheet plastics.
The most frequent uses for polyethylene are the anterior forms on custom molded AFO's and KAFO's, TLSO's, and upper extremity orthoses where joints are seldom used, such as in passive types of HO's, WHO's, and EWHO's. Polyethylene is an excellent choice when immobilization of a joint is required for a patient who needs a durable, flexible, and removable device. An additional advantage is that when vacuum forming over soft plastic foam, the polyethylene will adhere securely to the soft interface, providing improved comfort for the patient.
The most recent addition to the list of sheet plastics used in orthotics and prosthetics is thermo-vac® which has the unique characteristics of flexibility and transparency. It is commonly used as a check socket for trial fittings on difficult cases. It may also be used in the finished orthosis or become a part of the definitive prosthesis.
Thermo-vac can be vacuum formed with a frame, drape vacuum formed, or drape molded without vacuum. Extreme care must be taken when working with this material when it is hot because it will readily adhere to the skin, causing a burn. This caution also applies to sanding and finishing of the material, which will quickly raise an area of the thermo-vac to the melting point.
Orthotists frequently use this material for nonambulatory MAFO's, custom molded knee orthoses without hinges, upper limb fracture orthoses, T.L.S.O.'s, and custom molded cervical orthoses. Prosthetic applications include check sockets for BK, AK, and upper limb amputees, and it may also be used in the socket of an intermediate or definitive prosthesis when an optimum fit has been achieved in the check socket.
Patient acceptance of this material has been favorable compared to other sheet plastics due to the cosmesis of a clear device. However, it will rupture in high stress areas sooner than the other plastics, making it unacceptable for many applications. Moreover, it is much more expensive than the available alternatives.
Fig. 3
Lexan is a very rigid, high impact strength, transparent sheet plastic which has been found to be a good material for prosthetic check sockets. Its clarity is superior to that of thermo-vac, and its rigidity more closely simulates that of the laminated plastic socket it preceeds. Lexan may be bonded to an extension block and attached to an alignment fixture, and safely used for dynamic fit and alignment trials.
The major disadvantage is that, being hydrophilic, this material must be predried for two to six days, requiring a separate drying oven. Moreover, it must be vacuum formed using a holding frame and platen, and, therefore, is not readily accepted by many practitioners who do not already have this equipment. A Lexan check socket may be relieved by grinding, but not by spot heating as may thermo-vac. The Lexan check socket also cannot be used as a part of a definitive prosthesis.
Pelite is a light weight, moisture proof, sponge foam polypropylene with excellent shock absorption characteristics. It is available with invisible ventilation holes, or with visible perforations. It also comes in a wide variety of thicknesses, densities and colors. Pelite is most frequently used as a BK liner material, but is also used in pads or complete liners in pelvic girdles, AFO's, and other orthoses.
Fabrication is relatively simple, requiring only a heat gun (or oven) and an elastic bandage to hold the material in place over the positive model until it cools. Because of its ease of fabrication, durability, and washability, it has largely replaced the Kemblo and leather BK liners in most areas.
Fig. 4
A commonly used soft foam, plastizote is used as a liner material in both orthoses and prostheses. It may be used in insoles, pads in MAFO's, KAFO's, and in spinal orthoses. It may also be used in upper extremity orthoses for arthritic patients. As a BK prosthesis liner material, it should be used only for inactive patients, as plastizote will compress under weight bearing whether in a prosthesis or orthosis. On the other hand, it is very popular in the medical field because it is relatively easy to work with and may be vacuum formed or drape molded.
Aliplast is a lining material that is smoother in appearance than plastizote. It is popular with orthotists because of its softness as an interface, and for its ability to adhere to polypropylene, polyethylene, and thermo-vac during their vacuum forming. Prosthetists have found Aliplast to be of use as a BK liner material for patients who have very sensitive residual limbs or where skin breakdown seems probable. This liner material is not as durable as others and should only be used where these special problems exist.
At the laboratory of the Hospital of the University of Pennsylvania, we use an Aliplast liner for a temporary prosthesis and for patients who have difficulty wearing a hard socket. Whenever it becomes practical, we will use Pelite as the liner for its longer life and superior performance under active wear. The Aliplast liner for prosthetic or orthotic use is fabricated using a drape molding technique, with or without vacuum.
Sincere thanks to Rosemary Kowalski for her help in coordinating this project
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