Prosthetics

Prosthesis - replaces a missing limb or body segment (Orthotic supports a body segment)

Amputations should be considered constructive procedure rather than destructive.

Amputation Levels (for prosthesis fitting):	Optimum	Shortest	Longest
Transradial (forearm)	junction prox 2/3 & distal 1/3	3cm below biceps insertion	5cm above wrist joint
Transhumeral	middle third	4cm below axillary fold	10cm above olecranon
Transfemoral	middle third	8cm below pubic ramus	15cm above medial joint line of knee
Transtibial	8cm for every metre of height	7.5cm below medial joint line of knee	level at which myoplasty can be done

Disarticulations

Advantages:

1. retention of WBing surface

2. bulbous stump assists prosthetic suspension

Disadvantages:

1. compromise the choice & siting of joint

2. bulky appearing prosthesis

Ideal Stump:

1. Healed, mobile scar

2. Sensate

3. Cylindrical or conical shape

4. Myoplastic procedure

5. Nerves sectioned under tension

6. Bone ends bevelled

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Elements of a Prosthesis:

1. Socket

• transmits forces between the stump & the prosthesis in all planes

• may be proximal, distal or total bearing

2. Means of Suspension

1. suction socket

2. suspension belts

3. neoprene sleeve

4. elastic stocking

5. silicone sleeve

3. Joint mechanism (knee)

1. Stance phase control

   • Simple:

     • aligns the prosthesis so the ground reaction force passes in front of the knee

     • locks in hyperextension; 2 drums lock at 0-15deg.

     • for elderly

   • Mechanical stabilisers

     • braking mechanism activated by the WBing load or hydraulics

2. Swing phase control

   1. Pneumatic cylinder

   2. Hydraulic cylinder

   3. Intelligent prosthesis - computer adjusts rate of swing to cadence (steps/min)

4. Terminal device (hand / foot)

• Foot

  1. non-articulated

  2. solid ankle cushoin heel (SACH)

  3. articulated (uniaxial / multi-axial)

  4. energy storing