top of page

Prosthetics 

Step 1 Preparing the residual limb

​Before you can start using a prosthetic leg you will need to prepare your R.L (Residual limb previously referred to as the Stump). These preparations are crucial to reduce post operative swelling. There are various ways of preparing your R.L. namely:

Conning bandages

This is the most common method of shaping your R.L. It is important to be consistent and wear the elasticised bandages day and night. Normally a new amputee (Primary) will begin conning 2/3 weeks post-surgery (Varies from person to person)  and continue conning for 4/5 weeks.

Circumferential measures are taken every week (Normally by the amputee and sent to the Prosthetist). These measurements are crucial for deciding when to start the prosthetic measurement process. The R.L is stable once the circumferential measurements doesn't change from one week to the next.

Your prosthetist will show you how to apply your bandages in a figure 8 method. 

Warning:

  1. Diabetic amputees – Do not make the bandages too tight, the sensation around your R.L is compromised due to your medical condition.

  2. Open wounds and skin grafts amputees- make sure the skin has healed completely before you start bandaging and gradually ramp up the pressure over a period of time.

  3. The bandage will begin slipping a few minutes after you have applied it to your R.L, to prevent slippage you can use Baby rash cream (Fissan Paste, Bennetts Bum cream, Bepanthen). You can apply the cream liberally to the whole R.L.  

  4. If you feel your pulse throbbing in the R.L, you have made the bandages too tight.

neil profile pic _edited.jpg

Orthotist Prosthetist 

20231202_100714_edited.jpg
20231202_095927_edited.jpg
20240106_102223_edited.jpg

Copyright Mobility Assist 

Stump shrinker

The use of Stump shrinkers is a good method for shaping a residual limb if bandages cannot be used, but this method takes longer to prepare the R/L than using bandages. One of the problems with the stump shrinkers is that they need to be continuously modified to maintain pressure. This can extend the R.L preparation time considerably.

Rigid Ossur dressing

The (ORD) Össur Rigid Dressing immobilizes, protects and controls post-operative oedema in the R.L immediately following transtibial amputation surgery.

Immobilisation and oedema control are achieved by providing a firm dressing formed to match the volume and shape of the residual limb.

Step 2. Casting a negative impression

Once the residual limb has stabilised, the amputee is ready to be casted (Plaster of Paris impression).

I believe that casting should be done while pressure is applied while standing on an Otto Bock casting Jig. While this process can be done by hand, it’s almost impossible to emulate full pressure, total contact and anatomical alignment with hands alone.

Note: 3D scanning technology has not developed far enough to take a scan whist the R.L is weight bearing and pressurised. The 3D scan will only take the outer circumference measurements and convert them into a 3D mesh. The scan still needs to be modified with specialised 3D modelling software, but the R.L is still not under normal standing pressure.

Copyright Mobility Assist 

The casting jig can be used for Transtibial or Transfemoral amputees and provides an objective measurement, applying scientific methods.

Before casting the prosthetist must decide what type of prosthetic suspension would be best suited for the amputee. Determining the suspension method is critical as casting is done over the suspension systems.

Suspension types

A. Transtibial (Below Knee amputees)

B. Transfemoral (Above knee amputee)

Determining the suspension method is critical as casting is done over the suspension systems.

Step 3. Modifying and fitting the negative impression.

Once the plaster of paris bandages have cured, I remove the cast and begin the negative cast modification process. The main aim for doing the modifications is to create a quasi-test socket that can be applied onto the amputee while they are present for the first casting.

Trims lines are established and total contact is determined as a result of negative impression modifications.

1. Negative cast Fig. 1 Identification of anatomical landmarks to consider for modification.

2. Negative cast Fig. 2 Different colour (Reddish brown oxide) Plaster of Paris is used to mark areas of new added plaster of Paris  

Copyright Mobility Assist 

Fig. 2

Step 4. Modifying the positive impression

Once the negative impression is filled with liquid POP (Plaster of Paris), it is left to set and harden with a pole centred in the middle (Fig.1) 

When the POP is completely set, I remove the POP bandages and begin to transfer the anthropometric measurements onto the positive cast.(Fig. 2)

Plaster of Paris is coloured with Iron oxide and applied onto the positive mould. (Fig 3 & 4)

The excess plaster is removed, with the white areas showing the original mould and the brown areas are the build ups for later pressure relief. (Fig. 5)

Fig. 5 

Fig. 1 

Fig. 2

Fig. 3 

Fig. 4

Copyright Mobility Assist 

Step 5. Manufacture of the test (Diagnostic) socket

What is a socket ? A rigid finite size container which interfaces directly onto the residual limb.  

A test or diagnostic socket is normally manufactured for the amputee to walk with for a few weeks (Up to 4 months) before the definitive (Final socket) is produced. The test socket can be made from low temperature clear plastic or carbon composite. The clear plastic (Fig. 1 PTEG) is not suitable to be used for extended periods of time, so I rather use a composite socket which is a lot safer to walk with under normal conditions (Fig. 2 Composite socket is made from a combination of glass / carbon fibre and nylon)

Fig. 1 

20210901_154948_edited_edited.jpg
20210901_152513_edited.jpg

Fig. 2 

There are multiple reasons for manufacturing a diagnostic socket.

1.     To reduce postoperative swelling (Oedema), thereby reducing volume over the whole R.L.

2.     Used to diagnose pressure area problems (As the residual limb looses volume due to normal walking, the amputee will experience an increase of pressure on at           the bottom of their R.L as it begins to “sink” into the socket. Stump socks are used to increase the volume during the testing phase,

         i.e. Loose fitting test socket  + Stump socks = better fitting test socket.

3.    To check active alignment of the foot in relationship to the socket. (Gait anaysys and alignment) 

4.    A prosthetic test socket facilitates proprioception. (Proprioception is your body's ability to sence movement,action and location.) 

5.    Reduces overall prosthetic rehabilitation costs. (If the amputee moves onto to a definitive socket too soon, the socket will become loose very quickly, which                   means that the amputee will require an additional socket.)

R.L (Stump) socks are designed to compensate for volume fluctuations and to add cushioning to the R.L. They are available in many diffrent sizes. The stump socks are normally worn over the silicone suspension or in certain cases directly onto the skin if a siclicone liner is not used.

 

Component choice

The two main differences between a Transtibial and Transfemoral prosthesis is that the Transfemoral prosthesis has an addition prosthetic knee. When deciding on prosthetic components, the prosthetist will begin planning from the foot upwards.

Transtibial prosthesis consists of the following components (Below knee amputation).

Prosthetic foot

Tube adapter

Tube clamp adapter

Lamination anchor 

 

1.Prosthetic foot

 

Prosthetic feet can make a big difference to the amputees walking experience. A basic SACH (Solid Ankle cushion heel) foot will not store much energy in its wooden or plastic keel, while a carbon composite keel (Blade) will store energy at heel strike and toe off and release the energy at toe off. This energy storing and releasing capacity of carbon composite feet allows for a faster and less effort walking experience.

A. Solid ankle cusion heel (SACH foot)

B, C & D - Energy Storing feet (ESR)

E &F- Microprocessor Feet 

K1 

K2& 3 

K2& 3 

A

B

C

D

E

F

Amputees are categorised according to their range of mobility. The high the level of mobility, the more dynamic the prosthesis could be.

K0- Does not have ability to use a prosthetic leg. (This can be temporary as increased strength will increase mobility.

K1- Walking short distances ( The prosthesis is useful for amputees who want to be independent for standing and walking short distances inside their home.  

K2&K3- Amputees who actively walk on any terrain and normally use their prosthesis the whole day, removing it when they go to sleep.

K4- Sport and high energy activities. (Kite boarding, mountain biking, jogging and running.

K4

2. Tube adapter and tube clamp adapter

 

These adapters are used to assemble an Endo skeletal prosthetic leg, the tube is adjusted for height and the tube clamp adapter allows the fixture of the tube to the lamination anchor adapter.

3. Lamination anchor 

 

The lamination anchor is the critical component that attaches the prosthetic socket to the rest of the components. Great care should be taken when attaching the anchor to the socket, with bolts and nuts and special glue that sets in 60 seconds.

Transfemoral prosthesis consists of all the componsts listed above and below (Above knee amputation). 

1.      The prosthetic knee- Prosthetic knees are classified into 2 main types, namely,

a.      Mechanical

b.      Microprocessor (Electronic)

Prosthetic knees are further classified according to their internal mechanisms, namely,

a.      Single axis

b.      Multi axis

c.      4 Bar linkage

d.      Hydraulic

e.      Pneumatic

There is no doubt that Microprocessor knees will benefit all Transfemoral amputees regardless on R.L length , but unfortunately due to the high costs, these prosthetic knees are rarely fitted for above knee amputees.

A basic Microprocessor knee cost ranges from R 250.000.00 to R 1.3 Million (Just the kneee, not the entire prosthetic leg).

There are thousands of different types of prosthetic knees and feet on the market, however, its less important to know about all the different types of knees and feet, as it is what knee and foot combination will be best suited for you.

 

In a better world (Hopefully one day) all above knee amputees will have microprocessor knees regardless of financial status, and there may be a time when bioengineering becomes so advanced that they will grow a human leg in space and transplant it into the amputee with the aid of Artificial intelligence robots. In the meantime, amputees around the world will have to settle for a prosthetic knee that suites their pocket.  

1. Low cost 

K1 & K2 

Saftey knee with dynamic SACH

2. Low cost 

K1 & K2 

Mechanical lock knee with single axis foot

3. Low/medium cost 

K1 & K2 

Saftey knee with Balance foot

4. Low/medium cost 

K1 & K2 

Pneumatic knee with dynamic foot

5. Medium cost 

K1, K2 & K3 

Saftey knee with dynamic SACH

6. Medium/ high cost

K1, K2 & K3 

Hydraulic knee with Energy storing  foot

7. Medium/ high cost 

K4

Sport knee with sport blade

8. High cost 

K1, K2, K3 & K4 

Microprocessor knee with Energy foot 

bottom of page