Transtibial Prostheses
Amputations
WHAT IS AN AMPUTATION
Is the removal of a body extremity by trauma or surgery. As a surgical measure, used to control pain or a disease process in the affected limb, such as malignancy or gangrene. In some cases, it is carried out on individuals as a preventative surgery for such problems.
Its not very easy for a patient to prepare him or herslef for amputation because it causes the limitations in his/her life. Now by giving the patient an option of Prostheses you may support him/her morally and physically for ambulation and social integration.
A prosthetist must know the types and levels of amputation best for the prosthetic fitting and which type of flaps or stump clousers are required in different pathological or traumatic conditions. There should be a patient prosthetist meeting before the elective surgery to address the reservations of patient and determination of amputation level and type. Although its a team efforts and decisions but Prosthetist is a person who has to work after amputation with amputee and he/she know what problems they are facing during Prosthetic management.
Its not very easy for a patient to prepare him or herslef for amputation because it causes the limitations in his/her life. Now by giving the patient an option of Prostheses you may support him/her morally and physically for ambulation and social integration.
A prosthetist must know the types and levels of amputation best for the prosthetic fitting and which type of flaps or stump clousers are required in different pathological or traumatic conditions. There should be a patient prosthetist meeting before the elective surgery to address the reservations of patient and determination of amputation level and type. Although its a team efforts and decisions but Prosthetist is a person who has to work after amputation with amputee and he/she know what problems they are facing during Prosthetic management.
FACTORS LEADING TO AN AMPUTATION
Diabetic foot infection or gangrene is one of the most common cause of amputation in Pakistan and also in developing countries. The reason is poor hygein and education. People do not know the importance of foot care and hygein procedures and secondly the cost of the services is very high, so patients are unable to bear their medical expenditures.
Cancerous bone or soft tissue tumours confirms the surgical approch and often the amputation depending on the extension and type of tumor. Severe limb injuries in which the limb cannot be spared or attempts to spare the limb have failed. Peripheral Circulation problems aid the decision of amputatioon in PVDs. Congenital deformities of digits and/or limbs for example Poly ductile (Extra digits and/or limbs). Any advanced cancers Bone infections (osteomyelitits) or Traumatic amputation. Amputation in utero due to amniotic band and sometimes professional athletes may choose to have a non-essential digit amputated to relieve chronic pain and impaired performance.
SITE OF AMPUTATION
Before World War II, the majority of lower-limb amputations were Transfemoral because such procedures yielded healing rates approaching 100% in ischemic limbs. In the 1960s and early 1970s, several factors combined to reverse the ratio of Transfemoral to trans-tibial amputations. The use of a long posterior myofascio cutaneous flap in dysvascular patients, with its increased blood supply, improved the success rate in transtibial amputations. In addition, the development of preoperative objective criteria for amputation site viability allowed more distal amputations to be done.
BELLOW KNEE AMPUTATIONS
· PARTIAL TOE
· TOE DISARTICULATION
· PARTIAL FOOT/RAY EXCESSION
· TRANS METATARSALS
· SYMES
· LONG TRANSTIBIAL (> 50 % LENGTH)
· TRANSTIBIAL B/W (20-50 % OF LENGTH)
· SHORT TRANSTIBIAL (<20 %)
SELECTION OF AMPUTATION LEVEL
· General guidelines
· Considerations with PVD
· Considerations with trauma
· Considerations with malignant tumor
· Considerations with deformity
· Considerations with congenital limb deficiency/deformity revision
INVESTIGATIONS
· Angiography of the arteries in the legs (arteriography)
· Blood pressure measured in the arms and
· legs for comparison(ankle/brachial index)
FACTORS LEADING TO POSTOP INFECTION
Diabetes, Renal failure, Steroid medications, Immunosuppressive agents, Smoking and Preoperative infection.
Diabetes, Renal failure, Steroid medications, Immunosuppressive agents, Smoking and Preoperative infection.
PREOPERATIVE PREPARATION
· Informing the patient about the risks and benefits of the surgery.
· Providing necessary pain control and discussing pain control options.
· Patient should quit smoking at least 2 weeks before surgery.
· Patient should quit herbal supplements mentioned at least 2 weeks before surgery.
· Bowel preparation in advance might be Helpful.
· Nothing by mouth at least 8 hours before surgery Labs and x-rays.
· Prepare blood (if necessary)
· Sedation and pre-op anesthetic meds
· Hydration and IV access
· Enema, Foley catheter
· Prophylactic antibiotics
· Invasive catheters
· Consent for surgery
Basic principles
Skin flaps are as broad as possible and the scar should be pliable, painless, and non adherent. For most Transfemoral and nondysvascular transtibial amputations, equal length anterior and posterior flaps are used, placing the scar at the distal end and Long posterior flaps are often used in dysvascular transtibial amputations. Muscle stabilization may be achieved by myofascial closure, Myoplasty, Myodesis, or tenodesis. Several peripheral nerves form Neuromas (a collection of nerve ends) in the residual limb. The Neuroma must be well surrounded by soft tissue. Homeostasis is achieved ligating major veins and arteries where as Cauterization is used only for small bleeders.
SURGICAL PROCEDURES
Soft-Tissue Envelope
The soft-tissue envelope is the interface between the hard prosthetic socket and the hard bone of the residual limb. Most late breakdowns in residual limbs, however, are due to tissue shear, not direct pressure. To minimize late tissue breakdown, the soft-tissue envelope should be formed with a mobile, nonadherent muscle mass and full-thickness skin in the areas of load transfer.
Sagittal Flaps
Knee disarticulation, as advocated by Wagner and others, allows the patient to be operated upon in the supine position under regional anesthesia. This technique is well suited to the dysvascular patient since the skin flaps, being equal, each have minimal length. On closure, the surgical scar lies posteriorly, between the femoral condoyle. The Gastrocnemius is retained to provide a cushioned soft-tissue envelope that will allow comfortable direct load transfer. Sagittal skin flaps equal in length to half of the transverse diameter of the limb at the midpatellar tendon level are created with their anterior junction midway between the distal pole of the patella and the tibial tuberosity and the posterior junction directly opposite unless the knee has a major flexion contracture. In this case, the posterior junction is placed more distally to achieve equal sagittal flaps. Each flap is mobilized proximal to the knee joint. The patellar ligament is isolated and skived off the tibial tubercle. The knee joint capsule is incised circumferentially at the level of the joint, and the cruciate ligaments are skived from their attachments on the tibia. The vascular bundle components are ligated at this level, and the tibial and peroneal nerves are transected proximally and allowed to retract. The Gastrocnemius is divided distally to form a flap long enough to allow Gastrocnemius myofascia to be sutured to the remaining knee joint capsule. The skived patellar ligament is sutured to the stumps of the cruciate ligaments, with care taken to ensure that the distal pole of the patella does not extend distally into the weight-bearing plane of the knee joint. The menisci can be removed because their shock-absorbing function will be replaced by the Gastrocnemius muscle flap. The posterior fascia of the Gastrocnemius is then sutured to the remaining knee joint capsule, and the skin is reapproximated. The suture line assumes a midline posterior position between the femoral condoyle. A soft compression or rigid plaster or fiberglass dressing is applied.
Anterior and Posterior Skin Flaps
The incision for the anterior flap begins posteromedially just proximal to the joint line and extends convexly, anteriorly, and distally to a point approximately 2.5 cm distal to the tibial tuberosity. It then curves proximally and posterolaterally to end just proximal to the joint line. The posterior flap is also convex but somewhat shorter than the anterior flap. The patellar ligament is incised at its insertion, and the knee joint capsule is incised circumferentially. The cruciate ligaments are severed from their attachment on the tibia. The vascular bundle is ligated at the joint level, and the sciatic nerve is severed proximally. The Gastrocnemius is removed from its origin on the femur. The semimembranosus, semitendinosus, and biceps femoris muscles are divided at a level leaving adequate length for suturing to the patellar tendon without undue tension. The ilio-tibial band and pes anserinus are sutured to the remaining anterior retinaculum. The skin is reapproximated and an appropriate dressing applied.
Circumferential Incision
The main value of this technique is that no flaps are produced; however, the operation must be performed with the patient in the prone position. The knee is flexed to 90 degrees, and a circumferential skin incision is performed approximately 1.3 cm (½ in.) distal to the tibial tuberosity. Anteriorly and medially, the incision is carried down to bone, with the patellar tendon and pes anserinus elevated before the knee joint is entered. The capsule and ligaments are incised circumferentially at the joint level. The cruciate ligaments are skived from the tibia, the origins of the Gastrocnemius from the femur, and the biceps femoris from the fibular head. The patellar tendon and biceps femoris are sutured to the stumps of the cruciate ligaments. The antero-medial portion of the retinaculum is sutured to the posterior part of the capsule and semimembranosus. The skin is closed longitudinally, and an appropriate dressing is applied.
Reduction Osteoplasty
Reduction Osteoplasty decreases the bulk of the distal end of the residual limb to permit fabrication of a more cosmetic prosthetic socket. This is accomplished at the cost of decreased suspension from the expanded femoral condoyle, so auxiliary suspension might be required. The distal articular surface can be retained, as advocated by Mazet and Hennessy, simply by trimming the medial, lateral, and posterior protuberances. Burgess advocates shortening the femur by removing the distal portion of the condoyle in order to keep the knee centers level. By maintaining the expanded metaphyseal region of the distal end of the femur, direct load transfer can still be accomplished. Any of the described surgical approaches can be modified to incorporate these options.
Prescription Guide Line in Transtibial Prosthesis
There are many factors to be considered when a new prosthesis is prescribed, including weight bearing, suspension, activity level, general prosthesis structure, components, expense, and certain unique considerations. These will be discussed in order.
Weight bearing
For lower-limb prostheses, the weight-bearing characteristics of the socket are the first concern.
If the patient has scars, Neuromas, or sensitive areas, specific provisions of relief must be made in the design of the socket. Special shock-absorbing materials may be used, or modifications may be necessary to spread the load over a greater area. For example, in a Tran’s tibial (below-knee) prosthesis, a thigh corset might be considered if weight bearing causes severe problems with the residual limb.
Suspension
There are many methods of suspension, ranging from very basic leather belts to sophisticated suction sockets. Each alternative must be evaluated individually; anticipated volume change in the residual limb is a key factor. It is important to review any previous experience with other suspensions to determine the optimum recommendation.
Activity level
A person using the prosthesis only indoors obviously presents different considerations from someone who anticipates being active in his job and in competitive sports. Activity level influences weight bearing, suspension, and structural strength of the prosthesis.
Structure of the prosthesis
There are two basic structural types: endo skeletal and exo skeletal.
• Endo skeletal prostheses consist of internal tubes and components covered with soft cosmetic foam formed outer cover. They are now becoming popular because of their relatively light weight, and the good cosmoses they offer as well as the replacement and the repair of the component is very easy
• Exo skeletal prostheses on the other side consist of wood or polyurethane covered with a rigid plastic lamination.
Prosthetic components
Components need to be matched with the amputee's activity level, body weight, and functional goals. Obviously, the person with good strength and balance does not require a stance-control knee, while someone who intends to compete in the Boston marathon would require an artificial foot designed for a high activity level. Due to the large and expanding number of options now available in prosthetic componentry, close consultation with the Prosthetist is imperative.
Economy
The expense of prosthesis may vary greatly, primarily depending on the need for lightweight or sophisticated componentry. Lightweight prostheses are often made from titanium or carbon fiber, aerospace materials that are both expensive to obtain and difficult to manufacture, which may increase the cost of componentry 50% and more. Sophisticated componentry such as hydraulic knees will increase the cost of the prosthesis as well. Each feature of the prosthesis should be considered carefully to provide the most cost-effective solution that fully meets the needs of the individual amputee.
Unique considerations
Many patients present unique factors that need to be considered in the design of the prosthesis.
For example, the finish carpenter needs more comfort from the prosthesis in the kneeling position than the average wearer does. Cultural background is also significant; Asian amputees require a foot that allows the shoes to be removed easily when entering a home since that is customary. Such personal factors must be added to the more generic factors discussed previously to ensure the proper match between prosthetic configuration and amputee goals.
Stump Preperation Protocols
POSTOPERATIVE CONSIDERATIONS
In the immediate postoperative period, amputation stumps should be splinted with well-padded rigid dressings to prevent joint contractures. The use of an immediate postoperative prosthesis (IPOP) has been advocated to allow early prosthetic ambulation, decrease stump edema, and diminish post amputation depression. However, others have found significant wound problems with IPOP. In general, IPOP should probably be reserved for young, traumatic amputees. The most basic decision following wound healing in amputees is determination of appropriate candidacy for prosthetic ambulation. Moore et al. evaluated the variables associated with successful prosthetic ambulation in lower-limb amputees. The presence of coronary artery disease in Transfemoral amputees precluded prosthetic ambulation, presumably because of insufficient cardiac reserve for the increased energy demands of prosthetic ambulation. In this study, 32% of lower-limb amputees fit with prosthesis did not utilize it.
An overall assessment of the lower-limb amputee should be done prior to prosthetic fitting. The patient's social situation should be evaluated. Such factors as impaired vision from diabetic retinopathy, poor balance from concomitant cerebral vascular accidents, significant psychological problems, or additional musculoskeletal problems such as rheumatoid arthritis should be considered prior to prosthetic fitting. In an elderly, dysvascular lower-limb amputee with significant coronary artery disease, optimum planning in amputation surgery may involve wheelchair locomotion, which has been shown to be equivalent in energy expenditure to normal bipedal gait.
After the amputation there are several ways of dressing the residual limb. The most common way of dressing the limb is with the use of simple gauze dressings. This is typically done in the operative room by your physician immediately following surgery. These dressings will then be changed periodically.
Prosthetic shirkers
At some point after the surgery, healthcare providers will discuss several things with the amputee including the use of shirkers, desensitization, positioning, contracture prevention, exercise, phantom sensation and phantom pain. Basically it prevents the edema formation. It is used to manage post-operative edema, you may be prescribed a Shrinker or ice wrap as a Means of compression therapy. Shirkers are elastic garments that are simply pulled on or wrapped around the limb. They are typically used when the suture line is reasonably healed. Until that time, crape bandage can be use. Both methods help to expel excess fluid that remains inside the limb. This helps to prepare the amputee to wear prosthesis by providing an appropriate limb shape.
Desensitization is important to prepare the residual limb for the forces that will soon Be applied with prosthesis. The most common and easiest way to desensitize the limb is to gently massage the entire area several times a day; this will decrease the skins sensitivity. Cold and warm water therapy (contrast bath therapy) is also very helpful for that purpose.
Positioning
Positioning is extremely vital to help prevent contractures that can cause problems When fitting a prosthesis. If the amputee is going to be sitting in a wheelchair, he/she should always have the knee straight (extended) as opposed to hanging down (flexed). If amputee sit with knee bent (flexed) for a long period of time, the limb may develop a Contracture and edema which prolong the necessary therapy. This will negatively effect the rehabilitation. Contractures can cause discomfort in prosthesis and/or effect how well amputee is able to walk. If a severe enough contracture occurs, this will limit the prosthetic options and candidacy.
Proper positioning can be achieved with the use of an extension board that will be provided by the physical therapist or Prosthetist. When lying in bed remember to keep the knee as straight as possible and amputee should place a pillow under the stump to prevent edema formation. Never place a pillow under the knee because this can also cause unwanted contractures.
Phantom limb sensation
Almost every amputee experiences the sensation that the amputated limb is still present. These feeling can occur due to a variety of factors including pressure or even weather changes. These sensations may disappear quickly or in some cases can remain for quite sometime. Phantom sensations are different for everyone and should not present any problems to Prosthetic fittings. Contrast bath therapy is recommended for that.
Phantom limb pain
In addition to phantom sensations, some people experience various types of phantom pain in the amputated limb. The causes of these phantom pains remain unknown but there are treatments available to help manage symptoms. If you experience phantom pain you should contact your physician so that they can Recommend the appropriate treatment. Psychological reassurance is recommended for that.
Exercise
After an amputation it is common to feel weak and unsteady. This is why it is important to begin stretching and exercise as soon as amputee is able. There are many different types of exercises; some can be done while lying in bed, some standing, some sitting, and more. At times, home exercise is important and at other times amputee may need to visit the physical therapy clinic. Physical therapist will be able to explain and demonstrate these and/or other exercises that is appropriate and beneficial for the amputee.
CONTRAINDICATIONS
Inadequate vascularity at amputation sites between the knee and ankle, for any reason, is an absolute contraindication to transtibial amputation. Dependent rubor or gangrenous changes about the upper portion of the tibia, whether gradual or sudden in onset, should lead to consideration of a primary Transfemoral amputation. Severe rest pain in the proximal portion of the calf may indicate the need for a primary Transfemoral amputation as well.
A knee flexion contracture severe enough to prevent use of transtibial prosthesis may be best served by a knee disarticulation, provided that the skin at that level is viable and will heal primarily. A relative contraindication to transtibial amputation is prolonged nonambulatory status. If the patient is bed bound, a knee flexion contracture will very likely develop. A knee disarticulation can be a good choice in this situation because it provides much better sitting balance than a Transfemoral residual limb does.
Person, however, maintains that the tibial portion of the limb will still be useful in transfer and wheelchair sitting activities and is reluctant to remove it on the basis of nonambulation alone. There are several conditions mistakenly thought of as relative contraindications to transtibial amputation. A diabetic or a patient with Hansen's disease (leprosy) need not be denied a transtibial level on the basis of insensate skin.
With good prosthetic fitting and regular observation of the skin for areas of pressure, the amputee should do extremely well. Hemiparetic patients can often manage household ambulation with a transtibial prosthesis. Even poor knee control can be managed easily with a hybrid "prosthesis" that combines transtibial prosthesis with orthotic knee control componentry, provided that flexion or extension patterning is not extreme and that reasonable balance is present.
If they are able to comprehend and follow instructions, they can do quite well. Even if they are not prosthetic candidates, sitting and kneeling activities will be enhanced by leaving as much of the leg as possible. Children with congenital foot deformities requiring revision for use of prosthesis are not well served by transtibial amputation.
This will interfere with the growth of the residual limb and make its relative length less in adulthood. In these cases, disarticulation at the ankle joint will preserve end weight-bearing capability and allow a moderate increase in length over time. In addition to the goal of obtaining the most distal amputation site possible, the stump should have sufficient soft-tissue coverage to resist the shear forces involved in prosthetic ambulation. Weight bearing occurs at the distal part of the stump in Transfemoral amputations and knee disarticulations. Painful Neuromas should be avoided at the site of weight bearing by sharply dividing nerves and allowing their retraction into sufficient soft-tissue cover.
Clinical Assesment for Transtibial Prosthesis
Personal information
Name, father name, age, gender, nationality, profession, religion, address and contact# are the information’s required under the heading of personal information.
Past history, family history& socio-economic history is also required before present complain to be noted.
Than we go for mental, physical& psychological status of the amputee. General body condition is assessed. Than we come to the concerning problem.
Muscle testing & grading:
Muscles are graded from 0 to 5 with 0 at no movement and 5 at movement against full resistance.
we have to check the grading of lower limb muscles especially,
· Knee flexors
· Knee extensors
· Hip flexors
· Hip extensors
· Hip adductors
· Hip abductors
· Medial rotators of hip
· Lateral rotators of hip
On sound side we have to check the grading of:
· Above mentioned
&
· Dorsiflexors
· Planter flexors
· Invertors of foot
· Evertors of foot
Range of movement:
Range of movement is to be checked in the affected and sound side in reference to
Serial number.
|
joint
|
Movement
|
Normal
|
Patient range:
|
1
|
Hip
|
Flexion—o--extension
|
140—o—20
| |
Adduction—o—abduction
|
20—o—45
| |||
Medial—o—lateral rotation
|
60—o—30
| |||
2
|
Knee
|
Flexion—o--extension
|
160—o—2
| |
3
|
Ankle
|
Planter—o—dorsiflexion
|
50—o—20
|
Stump size:
Stump can be divided into 3 main types with respect to its sizes.
Short stump
If the remaining stump size is less than 1/3rd of the tibial length, it is called short stump.
Medium stump OR Ideal stump
• If the remaining stump size is more than 1/3rd and less than 2/3rd of the tibial length, it is called medium or ideal stump.
Long stump
• If the remaining stump size is more than2/3rd of the tibial length, it is called long stump.
Stump shape
Trans-tibial stumps can be divided into 3 types with respect to shape. These are:
Bulbous
In this type of stump, the distal part of the stump is more in circumference than the proximal one. Mostly occurs in Myoplasty type of amputation. Bulbous stump shrinks the most, in the distal portion.
Cylindrical
In this type of stump, the stump is uniform in circumference throughout its length. It mostly occurs in Myodesis type of amputation.
Conical
In this type of stump, the proximal part of the stump is more in circumference than the distal one. It shrinks the least, and mostly occurs in Myodesis type of amputation. Most of the matured stumps are conical in shape. Any shape other than these three is considered irregular.
General conditions of the stump
For general conditions of the stump we look for:
Abrasion
The rubbing between the socket and the stump causes abrasions especially on the bony prominences. They should not be a factor in first fitting, but with continued wearing of the prosthesis any source of friction must be eliminated. Abrasions may result in blisters or denuded skin.
Boils & skin infections
Boils are the pus filled infections, with residue of dead tissue usually around the hair root. Other follicular lesions or pimples may be seen in these areas. Small opening & sinuses give evidence of old cyst. Medical care may be required before prescription of new prosthesis, and fitting may be postponed until infection is cleared up.
Bone spur
The bony outgrowths usually abnormal are referred to as bone spurs. They can be found on palpation but x-ray is the required investigation for proper diagnosis. The common spot of bone spur formation in TT stump is end of fibula. The typical spur is thin, tapered and pointed downward toward the end of tibia. Prominent spur must be avoided in fitting.
Bursa
A bursa is a sac filled of viscous fluid; it lies between the skin and a bony prominence to reduce friction on movement. Naturally occurring Bursa are located over patella and round the tendons of the knee flexors. These Bursa may get infected in which case medical care is required.
Discoloration
Discoloration is mainly due to pressure and stress. Also may be due to broken blood vessels in subcutaneous tissue. Edema damage reddens the skin, if prolonged turn to blue and finally brown stain is left. For Prosthetist, discoloration is the guideline for distribution of stress on the stump. If the pressure is born on the undesired areas than re-distribution of the pressure is carried out.
Edema
It is the collection of fluid in soft tissue of the stump. It can be postoperative or due to poor fitting of the prosthesis. If prosthesis causes too much constriction proximally the edema is inevitable. The edema should be reduced to a minimal level before casing because otherwise the socket fitted will become too loose. The shrinkage is achieved by wrapping the stump; the period of wrapping varies from hour to days, depending upon the individual case.
Pressure points
The areas of the stump that responds painfully to the pressure are called pressure points. For example fibular head these areas need relief in the socket.
Scars
Scars are of two types,
o Atrophic: they are thin, fragile and prone to be torn easily.
o Hypertrophic: they are thickened, adherent and painful.
All scar tissue is inelastic and care should be taken not to cause stretching and rubbing on the scar which will result in tearing the scar.
Trigger point
The spot on the stump that is painful to light touch is called trigger point. Although intermittent pressure is painful steady pressure is often tolerated.
Distal padding
The tissue covering the cut bones may vary in thickness from a thin cover of skin to a considerable amount of redundant tissue. When cover is sparse, care is needed in fitting especially when the cut bones are prominent or sharp. The bottom of the socket without discomfort can usually contain redundant tissue. Because this tissue often tends to become edematous, containment by the socket important for improved circulation. Redundant tissue should be pulled upwards when casting so that the constricting turns of plaster bandage don’t elongate the stump, otherwise it will be difficult to push the stump into the finished socket.
Subcutaneous tissue
The main problem of the subcutaneous tissue is shrinkage. It may b heavy or light. With heavier tissue more shrinkage is possible.
Skin
Skin may be delicate or rough. Skin of pressure areas like knee and elbow are rough while skin of the palm is termed as delicate. Delicate skin needs more time to adapt to the socket pressure.
Musculature
Mature trans-tibial stump has poor musculature, but stump of the fresh amputee has mass of muscles. This will atrophied, the stump can be expected to start shrinking soon after the fitting of the prosthesis. Atrophy will take longer if the musculature is firm (strong).
Condition of knee
Factors to be seen in condition of knee are:
Stability:
Stability of the knee is very important. Sometimes ML stability is not enough, in such conditions the ML walls of the socket are to be kept high enough to provide side-to-side stability.
ROM:
Prosthesis is aligned in such a way to provide maximum ROM at knee.
Patella:
Absence of patella or split patella may be encountered. These conditions are problems only if they affect the position and availability of the weight bearing patellar tendon. If they do other support areas need to be used more carefully.
Contractures:
Contracture is a problem only when it is severe. 15 – 20* of contracture can be accommodated through fitting and alignment of the prosthesis. In other words the flexion has to be given in the socket following the stump conditions.
Condition of cut bone:
The fibula is usually shorter than tibia. It is problematic only when the end of fibula moves with the knee flexion and end may be sharp rather than beveled.
Type of prosthesis recommended
Keeping in mind the social, economical and psychological status of the patient and all the assessment made a Prosthetist will prescribe the suitable prosthetic device for the amputee.
Types of Transtibial Sockets
Historic below knee Prosthesis
Consists of a leather thigh corset + side bars+ open ended socket.
Weight bearing is carried on the residual limb and through the suspension mechanism.
Advantages
The thigh corset supports some of the weight bearing. Prevent hyperextension at the knee. Provides lateral-medial stability. The socket is cooler than the total contact PTB because of lack of total contact pressure.
Disadvantages
Edema, Bulky and heavily, Uncosmetic, Atrophy, Relative motion causing
irritation, Ischemia, The hinge breaks frequently and abnormal gait.
Slip Socket Prosthesis
Design to minimize relative motion between the socket and skin. The socket is either elastically suspended from the sidebars or is attached to shank by a compression spring. The socket can rotate and piston up and down. Is used for only for those people with short or tender limb.
ADVANTAGES
The amputee with the slin graft can ambulate early. It preserves the knee joint.
DISADVANTAGES
Uncosmetic, Bulky and heavy, Produce atrophy, Tear of clothing, Walk more like an A.K
amputees.
PATELLAR TENDON BEARING
Was developed at the University of California (1959). More intimate fit and more efficient than historic. Total contact socket(prevent edema). Weight on patellar tendon.
Laminated/moulded Medial/lateral walls higher then the anterior. wall for Medio-lateral stability. Thigh corset is used for suspension
ADVANTAGES
Total contact design. Improve circulation of the stump. Prevent edema formation. To distribute the W.B. Better proprioception. Lighter than the historic. More freedom of movement than the thigh corset. More cosmetic gait. Gait looks essentially normal except for the lack of push off. More cosmetic. Easier to don and remove. Require less time for fabrication.
DISADVANTAGES
Require more critical fit. Excessive perspiration is needed. There is a tendency for the amputee to hyperextend the knee. Frequent readjustments may be necessary.
K.B.M (Kondylen Bettlung Munster)
It is modified form of patellar tendon bearing type of socket which has all the advantages of
the P.T.B type and is modified to avoid the disadvantages.
Total contact is provided in KBM type socket. Medial supra condylar wedge is provided for suspension. Triangular in shape for proper contact. Weight is distributed mainly on patellar tendon, medial and posterior flares of the tibia counter pressure are provided by the high popletial wall and from lateral flare of tibia.
Suspension prosthesis (Sc/sp)
Advantages
Better M_L stability is available in Sc/Sp type prosthesis. Also called supra condylar and supra patellar type. The patellar shelf is less pronounced in the PTS than in the PTB. Suitable for short stump: <7.5cm. Less restrictive & Easier to don. Prevents genu recurvatum. Cosmetically good.
Disadvantages
The prosthesis tend to slip down when the knee is flexed 90. Patellar enclosure may inhibit extreme knee flex. Is not suitable for long stump. Difficult for obese limb.
Posterior brim
The posterior brim is generally 0.6 to 1.3 cm (1/2 to ¼ in) higher than the patellar shelf tendon shelf. For very short limbs the posterior brim may be so high that flexion is limited to 60 degrees.
Anterior brim
The anterior brim comes to the midpatellar level.
Medial and lateral brim
Medio-Lateral brims come to about the level of the proximal edge of the patella. The proximal aspect of the medial and lateral walls supports the femoral condoyle and is usually 6.5 cm (2.5in) above the medial tibial plateau in height.
Ultralight below knee
Socket:
P.P is vacuum-formed.
Foot:
A sole and heel cushion like that used with any SACH can be used for it.
Advantages:
Require less energy to walk. Less pistoning and Can be worn in and around water
Disadvantages:
Not durable and Difficult to modify.
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