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Prosthetic CPM EXAM (
updated) QUESTIONS AND
ANSWERS (DETAILED &
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TF Bench Alignment - ANSWER-5* socket flexion (+contracture) 6-7* socket adduction (or match sound) Socket medial wall parallel to line of progression Knee: 5-25 mm posterior to weightline, external rotation 3-5* Foot: 12-37mm outset from IT, 5-7* external rotation TT Bench Alignment - ANSWER-5* socket flexion (+contracture) 5* socket adduction (or match sound) Foot: 37mm posterior to midline (SACH) or 1/3 of foot (DR) Foot: 12 mm inset to midlineder Info for Px Eval - ANSWER-Name, Age, DOB, Sex Ht, Wt Meds, comorbidities Amp site/cause/date ADLs/vocational/avocational Goals! Home status/environment Work status/environment PT/OT, assistive devices used Current/previous px treatment MMT, ROM Sensation Condition of residual limb Condition of contralateral/upper extremities K-level/AMP K0 - ANSWER-The patient does not have the ability or potential to ambulate or transfer safely
K1 - ANSWER-Prosthesis for transfers or ambulation at fixed cadence; household ambulator K2 - ANSWER-Ability to traverse low level environmental barriers; limited community ambulator, fixed cadence K3 - ANSWER-Ambulation at variable cadence; prosthetic utilization beyond simple locomotion; "unlimited" community ambulator, traverse most environmental barriers K4 - ANSWER-Exceeds basic ambulation skills, exhibiting high impact, stress, or energy levels; child, active adult, or athlete. K1 feet - ANSWER-SACH, Single axis, safe K2 feet - ANSWER-Multiaxial, flexible keel K3-4 - ANSWER-Dynamic response (also often multiaxial) With vertical shock Shock & torque absorbers External power feet - ANSWER-K1-3, all cadence/terrain Pros: propulsion, dorsi/plantarflexion Cons: batteries/weight/cost/processing speed Single axis feet - ANSWER-Pros: inexpensive, durable Cons: rigid forefoot, not energy efficient, not suitable for uneven surfaces SACH feet - ANSWER-Pros: provides stability in early stance Cons: DF stop increases knee hyperextesion Flexible keel - ANSWER-Pros: provides easy rollover, smooth transition from heel strike to toe off, allows natural sagittal plane motion, reduces socket foreces on residual limb, improves walking safety, reliable Cons: limited push off, increased cost Multiaxial feet - ANSWER-Pros: Accommodates uneven terrain, decreases stress on skin and prosthesis Con: Increased weight/maintenance, cost Dynamic Response feet - ANSWER-Pros: use with increased activity level, energy storing, reduces impact to joints and the residual limb, decreased walking effort/increased push off Cons: increased cost/weight K1-K2 knees - control - ANSWER-Fiction/mechanical - single speed ambulators May have manual lock feature Weight activated stance control
Building a recommendation: - ANSWER-Socket design Ultralight Acrylic Suspension type Interface (liners, socks, etc) Alignable components Knee Foot Hemipelvectomy Socket Principles - ANSWER-Weightbearing: IT/soft tissue Suspension: Iliac crests Knee disarticulation socket principles - ANSWER-Subischial or 3/4 sockets are appropriate Can use anatomical suspension over the condyles TF Ischial Containment Socket Principles - ANSWER-Femur held in adduction Very intimate fit Triangular shape ML compression Indicated for: shorter limbs, requires less voluntary control Potential for ischial weightbearing, high proximal trimline Gluteal and hydrostatic weightbearing Triangular shape TF MAS (ramal containment) Socket Principles - ANSWER-Hydrostaic weightbearing Lower trimlines Ramal buttress for ML control TF Subischial Socket Principles - ANSWER-Much lower trimlines - KD Use with anatomical suspension or vacuum Long limbs, requires good control and normal ROM of hip TF Quad Socket Principles - ANSWER-4 well-defined walls Rectangular shape Ischial/gluteal weightbearing AP control - Lack of ML support Contours for flexors/extensors
Indicated for longer limbs, good voluntary control, previous user Subischial triangle - ANSWER-Inferior ramus, gracilis, semitendinosis Scarpa's triangle - ANSWER-Inguinal ligament, sartorius, adductor longus Ischial containment trimlines - ANSWER-Anterior 50mm (2") proximal to IT Posterior 25mm (1") proximal to IT Medial at ischial level in line of progression Lateral 90 mm (3") proximal to IT Quad trimlines - ANSWER-Anterior: 2.5" proximal to IT Medial: at ischial level Lateral: 2.5" proximal to IT Posterior: at ischial level KD Suspension - ANSWER-Anatomical with foam liner - Pros: rotational control, increased suspension in swing phase; Cons: suspension localized to one area, not able to use with fluctuating edema Cushion liner Window/door Boa Lacer Seal-in suction Liner + Pin (TF) - ANSWER-Pros: Seated donning, positive lock Cons: difficult due to pin angle, soft tissue movement, pistoning/milking of tissue Liner + Lanyard (TF) - ANSWER-Pros: Seated donning, Great for low mobility/balance, positive lock Cons: pistoning/milking of tissue, single point connection, must have good hand strength Skin fit suction (TF) - ANSWER-Pull sock + expulsion valve Pros: Improved proprioception, Perceived as lighter, Eliminates pistoning Cons: Can be hard on skin, can't have volume fluctuation, must stand to don, need precise fit Seal-in liner (TF) - ANSWER-Pros: Improved proprioception, perceived as lighter, eliminates pistoning, shear forces moderated by liner Cons: must have good hygiene, must have good hand strength, must stand to don, need precise fit Elevated vacuum (TF) - ANSWER-mechanical or electronic
Joint + corset (TT) - ANSWER-Pros: provides max knee stability, very secure, can help with recurvatum. thigh weightbearing & unloading of limb, heavy duty, don sitting Cons: heavy, bulky, ugly, pistoning TT Interfaces - ANSWER-Socks: also for volume management Foam/pelite liner: custom, easily adjustable, durable Gel liners: cushion/flow, hot, prevents shear Flexible inner socket: reduce edge pressure, reliefs in outer Waist belt (TT) - ANSWER-Pros: secure, historic, knee extension assist Cons: bulky, ugly, pistoning Supracondylar (TT) - ANSWER-pelite liner with wedge, can have removable brim (ML-PML >=12) Pros: knee stability (ML), simple, short limbs, good for pts with upper limb involvement, low maintenance, don't need good hygiene, good for less active, easy donning Cons: higher trimlines, bulkier (thicker), restrict knee ROM SC-SP (TT) - ANSWER-Supracondylar with suprapatellar bar (quad bar), easy donning Pros: knee stability (AP and ML), simple, short limbs, good for pts with upper limb involvement, low maintenance, don't need good hygiene, good for less active, easy donning Cons: higher trimlines, bulkier, less cosmetic, restrict knee ROM Supracondylar cuff/strap (TT) - ANSWER-Pros: Simple, suprapatellar suspension, low maintenance, don't need large PML-ML difference, adjustable Cons: Higher trimlines, ugly, bulky, pistoning, may impair circulation Sleeve (TT) - ANSWER-Pros: minimizes pistoning, can be cosmetic by masking trimlines, can be used as auxiliary suspension, can be used for lots of patients Cons: hot, doesn't last very long, can reduce ROM, large thighs may cause it to roll down Liner w/ Lock or Lanyard (TT) - ANSWER-Pros: positive lock, lower profile, liner protects against shear, increased ROM Cons: can get pistoning/milking, must have full function of upper extremities for liner use, need good subcutaneous tissue, Seal-in suction (TT) - ANSWER-Pros: one way valve, solid connection, no pistoning, active patients, very secure Cons: little tolerance for volume fluctuation, must have good hygiene Elevated vacuum (TT) - ANSWER-mechanical or electric pump
Pros: Good for volume management, increased control/proprioception, wound care advantages Cons: requires sleeve, cognitive ability, pump adds weight, precise fit needed Clues: bilstering/discoloration of distal limb (socket fit is correct) - ANSWER- Problem: milking on the limb due to donning the liner incorrectly Solution: don liner without air at distal end Clues: Upper extremity terminal device opening with elbow flexion - ANSWER- Problem: EFA too proximal Solution: move EFA distal Clues: Upper extremity terminal device will not open all the way - ANSWER- Problem: housing is impacting, crosspoint incorrect location, CAS too loose Solution: check housing, move crosspoint distal to C7 and slightly to sound side, tighten CAS Clues: TF pain and redness on lateral distal femur - ANSWER-Problem: lack of ML stability in the socket Solution: ensure ischial containment, pad just proximal to distal lateral femur, adduct socket slightly Clues: Symes pain on medial/lateral malleolus - ANSWER-Problem: too much pressure? Not in socket all the way? Solution: Make sure malleoli are reaching the appropriate reliefs, relieve area if necessary Clues: Transtibial pain/redness on distal end, distal patella, and fib head - ANSWER-Problem: bottoming out Solution: add sock(s) Clues: Knee disarticulation using excessive amount of socks - ANSWER-Problem: Volume too large? Solution: pad socket Clues: Anterior proximal redness - ANSWER-Problem: excessive pressure anterior/proximal Solution: socket too extended (dynamic) flex socket Clues: Anterior distal pressure - ANSWER-Problem: too much pressure Solution: pretibial pads, extend socket Clues: Lateral distal pressure - ANSWER-Problem: Foot too inset Solution: outset foot Clues: Symes pediatric redness on malleoli after growth spurt - ANSWER- Problem: increased pressure due to growth Solution: onion layer socket to allow room for relieving
Attaches over the apex of the shoulder slightly anterior to the acromion Normal anatomical pronosupination - ANSWER-90 supination 80 pronation (preserved if 60% of the limb remains) E400 Elbow - ANSWER-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 - ANSWER-doubles the amount of excursion but requires double the force TR Cable System Validation Criteria - ANSWER->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) - ANSWER-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) - ANSWER-Excursion problem Solutions: check position of cross point, tighten or lower CAS TH Cable Clearances - ANSWER-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 - ANSWER->50% efficiency (force at TD/force at hanger) TD stays closed with elbow flexion <45* GH flexion to activate elbow Shoulder ROM should be 90* abduction, 90* flexion, 30* extension Forearm resists 3lb of internal/external rotation ** requires 4.5-5" of excursion total TD opens before/during elbow flexion (TH) - ANSWER-Force problem
Solution: move EFA distal, more bands, baseplate anterior/prox/lateral, add forearm lift assist, second base plate, lighter TD, shorten forearm section, check housing clearance, teflon/wax TD doesn't fully open at waist/mouth (TH) - ANSWER-Excursion problem Solution: tighten CAS, check housing clearance, move EFA distal, move baseplate posterior/distal/medial, add Northwestern ring/Baha/etc; add Z strap TT socket pressures: prox medial, distal lateral - ANSWER-Too much abduction Foot too inset TT socket pressures: Prox lateral, distal medial - ANSWER-Too much adduction Foot too outset TT socket pressures: proximal posterior, distal anterior - ANSWER-Anything that results in strong knee flexion moment Foot too posterior Foot too dorsiflexed TT socket pressures: proximal anterior, distal posterior - ANSWER-Anything that results in strong knee extension moment Foot too anterior Foot too plantarflexed TT loading response knee flexion - ANSWER-20* TT appropriate amount of varus thrust - ANSWER-1cm TT acceptable amount of pistoning - ANSWER-1cm TT too few socks - ANSWER-Redness: Distal fib head, distal patella, distal end of limb TT too many socks - ANSWER-Redness: tibial tubercle, prox aspect of fib head, verrucose hyperplasia Trouble shooting tools - ANSWER-Lipstick, corset stay, clay/playdough TF max LLD - ANSWER-1/4" Sagittal TF dynamic alignment goals - ANSWER-Knee stability throughout stance Smooth loading response Symmetry of step length and duration Quality of knee flexion during late stance and swing Frontal TF dynamic alignment goals - ANSWER-Adequate suspension Width of base of support Control of pelvis during prosthetic stance
