PROSTHETIC CPM STUDY GUIDE 2026 QUESTIONS AND
ANSWERS GRADED A+
✔✔Clues: Symes pediatric redness on malleoli after growth spurt - ✔✔Problem:
increased pressure due to growth
Solution: onion layer socket to allow room for relieving
✔✔Clues: redness at distal patella, loose fit - ✔✔Problem: socket fitting too large
Solution: add socks, educate sock ply management
✔✔Clues: Delivered wearing 3 ply socks, now back wearing 10 ply socks and has
redness/pain - ✔✔Problem: too many socks
Solution: remove socks, educate sock ply management
✔✔Clues: transtibial with fibula > tibia - ✔✔Problem: danger of putting distal pressure
on fibula
Solution: Provide relief for the fibula inside the socket
✔✔Clues: Verrucous hyperplasia on distal end - ✔✔Problem: lack of total contact
Solution: add distal end pad/remake socket to provide total contact
✔✔Clues: patient no longer fitting in socket today but fit yesterday - ✔✔Problem:
swelling (ate salty meal, not wearing shrinker at night)
Solution: educate patient on limb volume changes
✔✔Figure 8 Harness - ✔✔Control and suspension
✔✔Figure 9 Harness - ✔✔Control only
✔✔Base plate position (TH) - ✔✔25mm proximal to end of limb
Posterior lateral quadrant of humerus
Move proximal lateral: fix force problem
Move distal/medial: fix excursion problem
✔✔Elbow flexion attachment position - ✔✔25 mm anterior, 30 mm distal to joint center
Move proximal: less excursion required but more force
Move distal: less force required, but more excursion
✔✔Crosspoint location - ✔✔Inferior to C7 toward the sound side
increased comfort alternatives at cost of excursion: sewn, northwestern ring, dual ring,
expanded crosspoint, baha
, ✔✔Control attachment strap (CAS) location - ✔✔distal 1/3 of scapula
✔✔Anterior suspension strap (inverted Y strap) - ✔✔Location through the delto-pectoral
groove, Y forks 1" inferior to the clavicle
✔✔Shoulder saddle - ✔✔For heavy duty patients
✔✔Lateral suspension strap - ✔✔Crosses at the level of C7
Attaches over the apex of the shoulder slightly anterior to the acromion
✔✔Normal anatomical pronosupination - ✔✔90 supination
80 pronation
(preserved if 60% of the limb remains)
✔✔E400 Elbow - ✔✔Requires 1.5-2" excursion to cycle (2-3 lb of force)
Requires 2.5" to lock/unlock (7-9 lb of force)
Motions: GH flexion, scapular protraction
To lock/unlock: depression, extension, and abduction
✔✔Excursion amplifier - ✔✔doubles the amount of excursion but requires double the
force
✔✔TR Cable System Validation Criteria - ✔✔>70% efficiency (force at TD/force at
hanger)
Elbow flexion w/in 10* of anatomical
Retain >50% available pronosupination
Lift 50 lb or 1/3 of body weight (figure 8)
50 lb axial pull should not displace >12-25mm
✔✔TD too difficult to open (TR) - ✔✔Force problem
Solutions: remove rubber band, check for sharp angles on cabling, add teflon/wax to
housing
✔✔TD doesn't open all the way (TR) - ✔✔Excursion problem
Solutions: check position of cross point, tighten or lower CAS
✔✔TH Cable Clearances - ✔✔Cable 3mm between hanger and proximal housing
(extend and pronate)
Housing 3mm at proximal and distal ends of cabling, 6mm between proximal and distal
housings at elbow (flex, supinate, open TD)
✔✔TH Cable System Validation Criteria - ✔✔>50% efficiency (force at TD/force at
hanger)
TD stays closed with elbow flexion
<45* GH flexion to activate elbow
ANSWERS GRADED A+
✔✔Clues: Symes pediatric redness on malleoli after growth spurt - ✔✔Problem:
increased pressure due to growth
Solution: onion layer socket to allow room for relieving
✔✔Clues: redness at distal patella, loose fit - ✔✔Problem: socket fitting too large
Solution: add socks, educate sock ply management
✔✔Clues: Delivered wearing 3 ply socks, now back wearing 10 ply socks and has
redness/pain - ✔✔Problem: too many socks
Solution: remove socks, educate sock ply management
✔✔Clues: transtibial with fibula > tibia - ✔✔Problem: danger of putting distal pressure
on fibula
Solution: Provide relief for the fibula inside the socket
✔✔Clues: Verrucous hyperplasia on distal end - ✔✔Problem: lack of total contact
Solution: add distal end pad/remake socket to provide total contact
✔✔Clues: patient no longer fitting in socket today but fit yesterday - ✔✔Problem:
swelling (ate salty meal, not wearing shrinker at night)
Solution: educate patient on limb volume changes
✔✔Figure 8 Harness - ✔✔Control and suspension
✔✔Figure 9 Harness - ✔✔Control only
✔✔Base plate position (TH) - ✔✔25mm proximal to end of limb
Posterior lateral quadrant of humerus
Move proximal lateral: fix force problem
Move distal/medial: fix excursion problem
✔✔Elbow flexion attachment position - ✔✔25 mm anterior, 30 mm distal to joint center
Move proximal: less excursion required but more force
Move distal: less force required, but more excursion
✔✔Crosspoint location - ✔✔Inferior to C7 toward the sound side
increased comfort alternatives at cost of excursion: sewn, northwestern ring, dual ring,
expanded crosspoint, baha
, ✔✔Control attachment strap (CAS) location - ✔✔distal 1/3 of scapula
✔✔Anterior suspension strap (inverted Y strap) - ✔✔Location through the delto-pectoral
groove, Y forks 1" inferior to the clavicle
✔✔Shoulder saddle - ✔✔For heavy duty patients
✔✔Lateral suspension strap - ✔✔Crosses at the level of C7
Attaches over the apex of the shoulder slightly anterior to the acromion
✔✔Normal anatomical pronosupination - ✔✔90 supination
80 pronation
(preserved if 60% of the limb remains)
✔✔E400 Elbow - ✔✔Requires 1.5-2" excursion to cycle (2-3 lb of force)
Requires 2.5" to lock/unlock (7-9 lb of force)
Motions: GH flexion, scapular protraction
To lock/unlock: depression, extension, and abduction
✔✔Excursion amplifier - ✔✔doubles the amount of excursion but requires double the
force
✔✔TR Cable System Validation Criteria - ✔✔>70% efficiency (force at TD/force at
hanger)
Elbow flexion w/in 10* of anatomical
Retain >50% available pronosupination
Lift 50 lb or 1/3 of body weight (figure 8)
50 lb axial pull should not displace >12-25mm
✔✔TD too difficult to open (TR) - ✔✔Force problem
Solutions: remove rubber band, check for sharp angles on cabling, add teflon/wax to
housing
✔✔TD doesn't open all the way (TR) - ✔✔Excursion problem
Solutions: check position of cross point, tighten or lower CAS
✔✔TH Cable Clearances - ✔✔Cable 3mm between hanger and proximal housing
(extend and pronate)
Housing 3mm at proximal and distal ends of cabling, 6mm between proximal and distal
housings at elbow (flex, supinate, open TD)
✔✔TH Cable System Validation Criteria - ✔✔>50% efficiency (force at TD/force at
hanger)
TD stays closed with elbow flexion
<45* GH flexion to activate elbow
