DIFFERENT TYPES OF BELLOW KNEE SOCKET

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.

CASTING TECHNIQUE IN TRANSTIBIAL PROSTHESIS

It is the basic step in the manufacturing of the prosthesis after the assessment of the amputee and prescription of the right type of prosthesis for him. Casting provides a modifiable model to be worked upon.

There are many methods of casting conventionally casting is done by means of sketching the stump on the paper. As it is not the precise way of casting so other methods are used e.g. sand casting & plaster wrapping cast. Plaster wrapping cast is the most commonly used procedure now days.

Plaster wrapping cast is the most convenient and versatile 7 is used in all types of plaster cast work. It’s very simple to make cast of variable thickness and tightness using the plaster.The important features of the plaster wrap cast are:

•       Stump is placed in flexed condition and is marked to highlight certain anatomical areas.

•       Bandage is applied with a moderate and even tension to achieve a relatively undistorted cast.

•       Finger pressure is applied on the weight bearing areas so that resulting indentation helps in modification guidance.

Things needed for casting:

Following things are needed for a plaster wrap cast;

Tools:

Couch to sit the patient

Stool for Prosthetist to sit

Plastic sheet to be placed under the patient

Towel to cover the sound side of patient

Steel ruler to mark the reference lines

Basin of clean water to wet the bandages

Cast cutting scissor to start cutting the cast

Surgical knife to cut the cast

Venire calipers to take the AP and ML measurements

Measuring tape to take circumferences

Cutting aid to help in cutting

Materials:

Vaseline used as separating agent

Stockinet to shift the markings on cast

An indelible pencil to mark the important land marks

Pop bandages for casting

Clean swaps for cleaning the patient after casting

Measurement chart to fill in the measurements

Procedure:

Casting is divided in to:

Place preparation

         In place preparation the student have to clean the casting area and place the plastic sheet on the couch a place the material to be used in the casting in proper place change the water in the water basin and place measurement tools apart from cutting tools.

Patient preparation

         First patient is assessed and counseled about the procedure. And then is sufficiently exposed to take the casting and seated on the couch.

Casting

         After the preparation I thin layer of the Vaseline is applied over the stump. Then pull a thin, moist sock over the stump. The stump is held at about 20*-30* flexion during entire process of casting for certain bony prominences, aids in definition of the patella tendon and will locate the insertion of hamstring tendons. Place the cutting aid under the sock. Mark the wet sock with indelible pencil, indicating prominences and other sensitive areas. The prosthetic information form must be completed before the cast is taken

Marking areas

•       Patella

•       Patellar tendon

•       Tubercle of tibia

•       Head of fibula

•       Tibial crest

•       Distal end of fibula

•       Anteriodistal end of tibia

•       Proximal end of medial condoyle

Sensitive areas

•       The sensitive areas are to be provided relief, these are:

•       Tubercle of tibia

•       Head  of fibula

•       Tibial crest

•       Distal end of fibula

•       Distal end of tibia

•       Any other area showing any deformity( bone spur, Neuroma, adherent scar tissue etc

Relief on these areas is provided by pop straps

         Unwrap the pop bandage 15 cm (as many as needed) and place them on the floor beside the water basin. Apply the cut pieces of the pop over the pressure sensitive areas to provide relief on those areas in casting, cover the pieces of pop with thin layer of Vaseline. Submerge the pop bandages individually in the water basin for few sec. until the bubbles stop coming out of the bandage now squeeze it gently before applying to the stump. Now apply the pop on the stump with no tension in wrapping and wrap it from mid patella down to the stump end, overlapping one half the width of plaster bandage with each layer. Make sure that 4 to 6 layers of the bandage have been applied throughout the stump. Smooth the cast by massaging it up and down. Ask the patient to relax his muscles and keep on massaging the cast to make the bony areas of the stump prominent keep on working until the cast hardens. As the plaster hardens place the end of the thumbs to deepen the impressions for patellar tendon on both sides the thumbs should be placed at 30*-45* to tibia on both sides and counter pressure is applied by the fingers from popletial area. Now start wrapping the cast from the base of patella to cover the lover ¼th of thigh. Then a force just above the medial condoyle of the femur is applied for suspension purpose. Now the cast is cut at the cutting aid and cutting aid is remover and then the cast is remover off the patient and is trimmed to a desirable position now the reliefs are removed from the cast, this is the negative cast. The check socket is than fitted to the patient. Ask the patient to bare weight on the socket supporting the socket by your hands. This will help in getting the idea for modifications to be made in the positive cast after filling. Now transfer the reg. no. and names of the patient and Prosthetist to the cast.

Patient cleaning

         This is one of the most important steps of casting. After the removal just after closing the cast properly closed and refreshing the markings carefully, the stump of the patient should be cleaned using proper antiseptic solution. Prepare the cast for filling.

NORMAL GAIT & BIOMECHANICS

NORMAL GAIT

•       It is the series of rhythmical, alternating movements of limb and trunk, which results in the forward progression of the center of gravity.

•       The gait cycle is the period of time between any two identical events in the walking cycle  e.g.: Time from heel strike to the next ipsilateral heel strike.  The gait cycle is divided into two periods

•       Stance Phase

o   It is the phase of gait cycle in which the foot is in contact with the ground and is bearing the body weight.

o   It is 60% of the total gait cycle.

•       Swing Phase

o   it is the phase of gait cycle in which the foot is not in contact with the ground and is not bearing the body weight.

o   It is 40% of the total gait cycle.

•       Step length

o   It is the linear distance in the plane of progression between corresponding successive contact points of opposite feet.

•       Stride length

o   It is the linear distance between the corresponding successive points of heel contact of the same foot.

•       Single support

o   It refers to the period when only one foot is in contact with floor.

•       Double support (20% of gait cycle)

o   It occurs when both feet are in contact with floor.

o   The absence of period of double support distinguishes running from walking.

•       Cadence

o   It is the number of steps taken per minute. It may vary from 70 in slow walking to 130 in fast walking,

o   Adult male covers 2.50 miles or 4 km in one hour.

 Sub divisions of stance phase

•       Heel contact

o   The instant when the heel of the reference limb touches the floor.

•       Ball contact

o   When the bases of the metatarsals of the reference limb’s foot touches the floor

•       Foot flat

o   The initial contact of the forefoot with the floor.

•       Mid stance

o   When the greater trochanter is in vertical alignment with the vertical bisector of foot.

•       Heel off

o   When the heel of the reference foot leaves the floor.

•       Toe off

o   When the toe of the reference foot leaves the floor.

OR

It can be divided into

•       Weight acceptance phase

o   begins at heel contact and ends with foot flat position.

•       Mid stance

o   Begins with foot flat and ends with heel off.

•       Push off

o   Extends from heel off to toe off.

•       Sub divisions of swing phase:

It can be divided in to:

•       Acceleration:

It is characterized by the rapid acceleration of the lower end of the limb shortly after the toe off.

•       Mid swing:

It is the interval when the swinging limb over takes and moves ahead of the limb in stance face (contra lateral limb).

•       Deceleration:

It is the interval when the swinging limb approaches the end of interval and slows down for heel contact.

 Path of center of gravity:

         The laws of mechanics make it clear that the least amount of energy is required when a body moves along straight lines, with center of gravity neither deviating neither up and down or side ways. Which is not possible in human beings?  So the body’s center of gravity deviates from straight line but for the sake of energy conservation, deviation should be kept to an optimal level. This is done by the muscles and ligaments of the body.

 Vertical displacement:

          In the normal walking pattern the center of gravity goes trough a rhythmical ups and downs as it moves forward but it is extremely smooth with no abrupt change in direction. The highest point is in the mid stance and the lowest point is in double support. The average amount of vertical displacement is 5cm or 2 inches.

Lateral displacement:

          As weight is transfers from one limb to the other one the pelvis also shifts to the weight bearing side and with it COG also shifts. The total amount of sideway movement of pelvis is 5cm or 2 inches. The limit is achieved in the mid stance and the path followed by the COG is extremely smooth.

Gait characteristics that influence the path of COG:

The characteristics that influence the path of COG are:

•       Flexion on knee during stance

Just after the heel contact, flexion of knee begins and continues until it reaches 20*. This characteristic of normal gait helps to smoothen the path of COG and limits it’s up and down osilation to an optimal level

•       Pelvic depth

In normal walking the pelvis drops on the swing side, i.e: stance hip adducts slightly. The amount of displacement of the pelvis from the horizontal is controlled with in 5* by the abductors of the hip of the contralateral side. In standing this dip found is the positive trendelenberg sign, in walking it is normal and serves to reduce the upward displacement of COG.

•       Pelvic rotation

In addition to the dipping the pelvic rotates forward in the horizontal plane. This rotation is 4* on each side of the COG. This helps to reduce the vertical displacement of COG.

•       Width of the walking base

In figure WB is the width of the walking base that falls within the range of 5-10cm or 2-4 inches. As the pelvic shifts towards the supporting side to maintain the stability so the normal narrow walking base minimizes the lateral shifting of the COG.

Parts of Transtibial Prosthesis

Transtibial prosthesis consist the following parts

•       Socket

•       Socket adopter

•       Shank

•       Foot adopter

•       Foot

Note: All the above mentioned components are discussed in detail.

Prosthetics sockets

•       Prosthetic socket connect the residual limb to the prosthesis.

•       It provides optimum support to the patient and ensures a good prosthesis fitting.

•       The prosthetic socket consists of a liner and a matching closure system.

•       The liner acts as a sort of “second skin” between the movable soft tissue of the residual limb (muscles, tissue, skin) and the hard shell of the socket.

•       It is custom–made according to the shape and condition of the residual limb and the respective mobility grade.

OBJECTIVES OF SOCKET

•       Total Contact.

•       Good sensory feed back.

•       Loading Pressure Tolerant Areas.

•       Relieving Pressure Sensitive Areas.

•       Light in Weight.

•       Cosmetically Acceptable.

•       Strong enough for weight bearing.

•       Suspend the prosthesis.

•       5-10° of socket flexion exposes more of the anterior wall for weight bearing.

PARTS OF SOCKET

•       Prosthetic socket consist of

o   Soft inliner(second skin)

o   Laminated socket 

SECOND SKIN

The “second skin” is

•       thin protective membrane

•       made of a flexible material

•       Rolled over the residual limb.

•       It connects the residual limb of patient to the socket.

•       Selection of right liner is essential so that prosthesis fits well and is comfortable to wear.

•       For optimum patient safety and comfort there should be a good combination of liner and closure system.

The single most critical aspect of any
prosthesis is the quality of the interface
between the residual limb and the
prosthesis.” Marks & Michael (2001)

FORCE ACTS ON A SOCKET

There are three types of forces act on socket during normal gait.

·          Impact forces generated when heel strikes the ground.

§  Soft liner and shock-absorbent feet minimize impact forces.

·         Rotation forces occur during the stance phase can cause rotation in the socket. The shape of the socket combined with special connective techniques (e.g. negative pressure) can be used to minimize rotation forces.

·         Shear forces also known as lifting forces. Occur during the swing-through phase, and can be controlled with the help of the right liner material and correct closure system. 

    MATERIALS USED IN A SOCKET

•       P.V.A files

•       Stockinet

o   Perlone

o   Nylone

o   Dacron

o   Cotton

•       Fiber glass/carbon fiber

•       Risins

•       Hardner

•       Accelerator(catalyst)

•       Socket adapter

TYPES OF SOCKET

•       Leather sockets(Provide flexibility and Adjustment),

•       Wooden Sockets.

•       laminated/moulded

o   They are total contact sockets.

•       Flexible

•       Rigid

•       Mainly there are four types of sockets

1.       Patellar Tendon Bearing (PTB).

2.       Kondylen buttlen munster (KBM)

3.       Supra condylar (medial wedge).

4.    Supra-condylar and supra-patellar. 

TYPES OF PROSTHESES

TYPES OF PROSTHESES 

·         There are five generic types of prostheses: postoperative, initial, preparatory, definitive, and special-purpose prostheses.

·         Although progression through all five levels may be desirable, only selected amputees will receive the postoperative or initial prostheses, which are directly molded on the residual limb.

·         Most amputees will have preparatory and definitive prostheses, but a much smaller number will receive special-purpose prostheses for showering or for swimming and other sports.

1.       Postoperative prosthesis.

2.       Initial prosthesis.

3.       Preparatory prosthesis.

4.       Definitive prosthesis.

5.       Special use prosthesis.

Initial Postoperative Prostheses (IPOP)

 There are more aggressive approaches to post operative care that may include the use of a rigid

Dressing or what is termed an Immediate Post-Operative Prosthesis or IPOP. An IPOP is an

Immediate postoperative prosthesis that is used as an early form of prosthetic intervention.

•       The benefit of being fit with IPOP prosthesis is early ambulation if allowed by your physician. IPOP prosthesis is also said to help with phantom limb sensation, because you can see that there is a leg, or in this sense, prosthesis attached.

•       IPOP prostheses also protect the residual limb from being injured.

•       Many times, a patient will wake up in the middle of the night to use the restroom, and

Forget that their limb has been amputated.

•       When they get out of bed and try to stand on both limbs, they fall down and re-injure

The surgery site.

•       An IPOP prosthesis will protect the end of the residual limb should this occur.

•       There are many different types of postoperative care and your physician will help you choose which the best is for you.

•       Postoperative prostheses are, by definition, provided within 24 hours of amputation.

•       These are often referred to by various acronyms including immediate postsurgical fitting (IPSF) and immediate postoperative prosthesis (IPOP).

•       Although technically feasible for virtually any amputation, postoperative fittings are currently most commonly prescribed for the younger, healthier individual undergoing amputation due to tumor, trauma, or infection.

•       Its use in the elderly or dys-vascular individual is controversial but can be successful when meticulous technique and close supervision are available.

Initial Prosthesis

•       The initial prosthesis is sometimes used for the postsurgical fitting and is provided as soon as the sutures are removed.

•       This is sometimes referred to as an early postsurgical fitting (EPSF). Due to the usual rapid atrophy of the residual limb, the EPSF is generally directly molded on the residual limb by using plaster of paris or fiberglass bandages.

•       An alternative is to use a weight-bearing rigid dressing. Such devices are used during the acute phase of healing, generally from 1 to 4 weeks after amputation, until the suture line is stable and the skin can tolerate the stresses of more intimate fitting.

•       Postoperative and initial prostheses are most commonly used in rehabilitation units or in hospitals with very active amputee programs. 

Preparatory Prosthesis

•       Preparatory prostheses are used during the first few months of the patient's rehabilitation to ease the transition into a definitive device.

•       They are also used in marginal cases to assess ambulatory or rehabilitation potential and help to clarify details of the prosthetic prescription.

•       The preparatory prosthesis accelerates rehabilitation by allowing ambulation before the residual limb has completely matured.

•       Preparatory prostheses may be applied within a few days following suture or staple removal, and limited gait training is started at that point.

•       Originally, the preparatory prosthesis was a very rudimentary design containing only primitive components.

•       The modern preparatory limb, however, usually incorporates definitive-quality endoskeletal componentry but lacks the protective and cosmetic outer finishing to reduce the cost.

•       It allows the therapist and Prosthetist to work together to optimize alignment as the amputee's gait pattern matures.

•       Different types of knee mechanisms or other components can be tested to see whether individual patient function is improved.

•       Preparatory prostheses are generally used for a period of 3 to 6 months following the date of amputation, but that time can vary depending on the speed of maturation of the residual limb and on other factors such as weight gain, weight loss, or health problems.

•       The new amputee may begin by wearing one thin prosthetic sock in the preparatory prosthesis; after 3 months, he may be wearing ten plies of prosthetic socks to compensate for atrophy.

•       When the number of plies of prosthetic socks the patient must wear remains stable over several weeks, it is usually an indication that the definitive prosthesis can be prescribed.

 Definitive Prosthesis 

•       The definitive prosthesis is not prescribed until the patient’s residual limb has stabilized to ensure that the fit of the new prosthesis will last as long as possible.

•       The definitive prescription is based primarily upon the experience the patient had when using the preparatory prosthesis.

•       The information learned during those months will demonstrate to the clinic team the patient's need for a lightweight design, special types of feet or suspension, or any special weight-bearing problems that may arise.

•       Unless a suction socket is used, the amputee wears prosthetic socks over the residual limb for the same reason that people wear socks when wearing shoes: the textile fibers provide cushioning and comfort, take up shear forces, and absorb perspiration.

•       An additional advantage is the ability to accommodate minor volume fluctuations by wearing more or fewer layers (plies) of prosthetic socks.

•       Once the amputee is wearing ten plies of prosthetic socks, the fit has degraded sufficiently that socket replacement should be considered.

•       A definitive prosthesis is not a permanent prosthesis since any mechanical device will wear out, particularly one that is used during every waking hour.

•       The average life span for a definitive prosthesis is from 3 to 5 years.

•       Most are replaced due to changes in the amputee's residual limb from atrophy, weight gain, or weight loss.

•       Substantial changes in the amputee's life-style or activities may also dictate a change in the prosthetic prescription.

•       Overall physical condition is also a factor since the more debilitated individual generally requires a very lightweight and stable prosthesis.

Special-Use Prostheses

·         A certain number of patients will require special-use prostheses designed specifically for such activities as showering, swimming, or skiing.

·         It is most economical if special-use devices are prescribed at the same time as a definitive replacement is necessary since both can be fabricated from the same positive model.

·         Most require specialized alignment. For example, swimming prostheses are made waterproof and aligned so that the patient can walk without a shoe.

·         In some cases the foot can be plantar-flexed and have a swim fin attached.

·         Snow skiing prostheses require an increase in dorsi-flexion at the ankle and may incorporate additional knee support or auxiliary suspension.

·         Special-use prostheses can be valuable to the amputee who wishes to expand his activities and participate in a full range of sports and recreational activities.