Prosthesis fitting - socket fabrication, switch placement, etc.

Prosthetists: C. Karthikeyan, Kavitha, Sathish, Arul, Anand, Radhakrishnan

Steps involved in Socket fabrication

1. Residual limb assessment
2. Selection of residual Limb movements
3. Casting and measurement
4. Rectification of positive
5. Building up of forearm shell
6. Lamination or sheet draping
7. Socket trial
8. Placement of switches
9. Fixing terminal device to forearm
10. Checkout
11. Cosmetic covering

Residual Limb movement assessment

Residual Limb movement assessment is vital in switch placement.

• Supination / Pronation
• Muscle contraction of flexors / extensors

Different methods in operating the switches

• Muscle contraction
• Residual limb movements alone
• Combination of muscle contraction and residual limb movements

Placement of switches by muscle contraction method

Ask patient to contract flexors by imaginarily "flexing wrist" on amputated side

Mark maximum muscle bulging point for Switch S1

Ask patient to contract extensors by imaginarily "extending wrist"

Mark maximum muscle bulging point for Switch S2

Placement of switches using residual limb movements alone

Casting residual limb

Rectification of positive

Mark the positions and rectify the positive

Paste two foam pieces 15mm dia & 3mm thick on the marked positions

Building up of forearm shell

Make a cylinder with a plastic sheet (used transparency slide or X-ray film) of the same diameter as the motor casing

Laminate or Sheet Drape (with the bulge of the switch markers showing)

Drill two 20mm holes in the socket over the bulges

Suspension: Proper suspension will prevent displacement of control switches from the desired contact area of the residual limb

Fixing the motorised hand to the socket

Drill a hole on the socket just proximal to the hand motor (M1), to pass switch wires out of socket

Alignment for fixing hand
Align first web space of motorised hand with radius in mid prone position

Now insert motorised hand in the socket & drill two 4mm holes for the screws to fix the hand in socket. Ensure alignment of the holes in the shell with the holes in the motorised hand

A sheet of 1mm polythene is used to make the switch holder plate. Fit the switch in the switch plate. Fix switch plate with the switch (polythene sheet) with 3mm screws; add spacing washers to make adjustments so that the switch is in proper contact with the muscle when the socket is worn.

Assembled artificial hand with the socket, switches and battery

Fully fitted transhumeral prsothesis: