Upper Prosthetics Troubleshooting

Question 1

Pain at sound side axilla

Answer 1

-Cause: optimal placement may cause discomfort
-Solutions: add axilla loop pad, add Hessing pad, add double Northwestern ring, add crossback strap

Question 2

Harness pinches sound side axilla

Answer 2

-Cause: Northwestern ring is placed too close to the sound side
-Solutions: widen axilla loop, move Northwestern ring closer to prosthetic side

Question 3

Harness is not providing efficient excursion

Answer 3

-Cause: Northwestern ring is placed too close to prosthetic side
-Solution: tighten axilla loop, move Northwestern ring closer to sound side

Question 4

Inverted Y-strap slides lateral off shoulder

Answer 4

Cause:
1 - the two inverted Y-straps are too tight
2 - Northwestern ring is too proximal on patient’s back
Solution:
1 - loosen the strap
2 - add crossback strap, add double Northwestern ring

Question 5

Inverted Y-strap is cutting into patient’s shoulder soft tissue

Answer 5

Cause:
1 - attachment to triceps pad is too lateral
2 - triceps pad is too wide
Solution:
1 - bring attachment point more medially on triceps pad
2 - ensure triceps pad’s proximal width is 1/2 the circumference of the arm at that level, if too wide re-fabricate

Question 6

With elbow flexed at 90 deg and weight applied to the terminal device, pain at distal radius and proximal ulna/olecranon

Answer 6

Cause:
1 - socket fit issue
Solution:
1 - ensure appropriate contours are in socket, add pads/socks to optimize socket fit

Question 7

Terminal device does not fully open or opens the same amount regardless of force applied

Answer 7

Cause:
1 - too much force required to open terminal device
2 - housing clearance issue
3 - issue with harness efficiency
Solution:
1 - remove rubber bands
2 - ensure there is 1/2” clearance proximally (functionally long) and distally (functionally short), shorten cable as needed
3 - adjust cable strap to distal half of scapula w/ double Northwestern ring, increase tension on control strap, replace cable if broken, switch to spectra cabling with Teflon lined housing

Question 8

Terminal device opens with forearm pronation

Answer 8

Cause:
1 - cable is too tight
2 - housing clearance issue
3 - baseplate too proximal and lateral
Solution:
1 - loosen control attachment strap
2 - ensure there is 1/2” clearance proximally (functionally long), shorten cable as needed
3 - move baseplate anterior and distal

Question 9

Difficulty flexing elbow unit

Answer 9

Cause:
1 - forearm lift tab is too proximal/posterior; requires too much force to flex elbow
2 - terminal device is too heavy
3 - cable is aligned through/posterior to elbow joint axis
4 - baseplate and retainer is very proximal on humeral socket d/t limb length
5 - issue with harness efficiency
Solution:
1 - move forearm lift tab distally
2 - change to lighter terminal device (aluminum), shorten forearm section of socket
3 - adjust housing anchors and forearm lift tab to realign cable
4 - add second baseplate/retainer to distal/lateral socket to guide cable more efficiently
5 - adjust cable attachment strap position

Question 10

Terminal device doesn’t open at mouth

Answer 10

Cause:
1 - forearm lift tab is too distal/anterior, requires too much excursion to open TD w/elbow flexed
2 - issue with harness efficiency
3 - baseplate and retainer is very proximal on humeral socket d/t length of limb
4 - TD requires too much force to open
5 - lack of appropriate clearance b/w split housing or housing and triple swivel
Solution:
1 - move forearm lift tab proximally, add lift assist at a more proximal location
2 - adjust cable attachment strap position, replace cable if broken
3 - add second base plate/retainer to distal/lateral socket to guide cable more efficiently
4 - remove rubber bands
5 - ensure there is 1/2” clearance proximally (functionally long) and distally (functionally short), shorten cable as needed

Question 11

Terminal device opens when elbow flexion is the desired movement

Answer 11

Cause:
1 - forearm lift tab is too proximal/posterior, force to flex the elbow unit is greater than the force to open the TD
2 - TD is too heavy
3 - cable is aligned through/posterior to the elbow joint axis
4 - too little force required to open the TD
5 - issue with harness efficiency
Solution:
1 - move forearm lift tab distally (elbow flexion requires 9 lbs to flex, TD requires 15 lbs to open)
2 - change to lighter TD (aluminum), shorten forearm section of socket
3 - adjust housing anchors and forearm lift tab to realign cable anterior to elbow
4 - add rubber bands
5 - adjust control attachment strap position, increase tension of control strap, adjust Northwestern ring position, replace cable if broken, switch cable

Question 12

Elbow does not flex and terminal device does not open with humeral flexion

Answer 12

Cause:
1 - issue with harness efficiency
Solution:
1 - adjust control strap position, increase tension of control strap, adjust Northwestern ring position, replace cable if broken, switch cable