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14 Evaluation of Socket Fit

1. Before donning the socket

Condition of the residual limb

  • If relevant, changes in skin, shape, muscle tone, soft tissue, bony/sensitive areas since the last visit.
  • Limb circumferences (use table format)
  • Skin condition
    • Prior to fitting:
    • After fitting:

2. Don socket

Use baby powder during the test socket fitting to ease donning and protect the skin.
Place the donning sock over the residual limb to pull the tissue into the socket.
Press up while the pt pushes down.  Pull portions of the donning sock to gradually pull the pts tissue into the socket.

3. Check fit[1]

  • 3a) Overall Fit and Function: Initial impression of socket fit, trimlines etc.  Trimlines will be checked and changed throughout the fitting process.
  • 3b) Suction/Suspension: Initial trial of suction.  This will be tested again once harness and componentry are attached.
  • 3c) Range of Motion / Stability:  No restriction of motion and good translation of motion to socket
3a) Overall Fit and Function: Initial impression of socket fit, trimlines etc.  Trimlines will be checked and changed throughout the fitting process.

  1. Total Contact
    1. Ensure socket is donned completely by checking axilla and tendon compression
    2. No gapping
    3. Skin covering valve seat (slight pooch acceptable)
    4. Tissue not under excessive pressure
  2. Trim Lines
    1. Intimate contact but no excessive pressure

 
3b) Suction/Suspension: Initial trial of suction.  This will be tested again once harness and componentry are attached.

  1. Holds suction without support.
  2. Holds suction with distraction

 
3c) Range of Motion / Stability:  No restriction of motion and good translation of motion to socket

  1. Flexion
    1. no clavicular pressure with active flexion (can also break suction)
    2. replicate weight of prosthesis – no anterior gapping, no anterior distal humeral pressure, no excessive pressure on scapula
  2. Abduction
    1. no excessive pressure from anterior or posterior stabilizers
    2. no distal lateral humeral pressure – replicate weight of prosthesis
  3. Extension
    1. no excessive pressure over scapula
    2. no clavicular pressure with active extension with resistance
  4. Rotational Stability
    1. Rotation limited by anterior and posterior trimlines
    2. Stabilization comfortable

Check for gapping and blanching through ROM.

4. Check length and alignment

Alignment: Mark vertical lines on the test socket to determine placement of turntable. The turntable should be vertical in both frontal and sagittal planes

  • To draw the alignment lines, position the test socket on the patient’s limb and position the limb in neutral alignment. The humerus should be aligned vertically, neutral flexion/extension, abduction/adduction and neutral internal/external rotation (the patient’s comfortable carrying angle).
  • Drop the plumb line from the lateral aspect and draw a vertical line.
  • Draw a second line from the posterior (or anterior).  Measure the horizontal distance from this line to the lateral aspect of the patient’s hip.
  • Eventually, you will use these lines to capture the pre-flexion angle and the clearance for the hip in the final prosthesis.
Length: Place a hatch mark on the socket at 10 cm distal to the acromion.

  • Measure the distance between the acromion and the 10 cm hatch mark on the socket.
  • You will use this mark to determine the position of the elbow joint.

  • Humeral length
    • acromion to lateral epicondle = acromion to center of elbow axis
    • acromium to distal end of forearm, when elbow is flexed to 90’
  • Forearm length
    • lateral epicondyle or olecranon to distal thumb in a relaxed position = lateral epicondyle or olecranon (or elbow joint center) to distal end of TD
  • Functional length – this may be shorter than the patient’s contralateral limb or shorter than the result from the Carlyle index. It may be a length that most easily allows the person to reach their mouth with the prosthesis.
  • For someone with bilateral limb loss, you may use the Carlyle formula
    • Humeral length (AC to lateral epicondyle) = 0.19 times body height
    • Forearm length (lateral epicondyle to thump tip) = 0.21 times body height
  • Be sure to consider clearance for components

 

5. Revisit functional goals/purpose of prosthesis

  1. Written by MacJulian Lang, CPO, Clinical Director at Advanced Arm Dynamics, NW ↵

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Upper Limb Prosthetics and Orthotics: Techniques Copyright © by Sue Spaulding. All Rights Reserved.

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