CPO CPO Materials Science & Technology 2 — Questions and Answers
Question 1: Which lamination resin type is most commonly used in structural prosthetic sockets due to its balance of strength, weight, and ease of fabrication?
- Polyester resin
- Acrylic (PMMA) resin (Correct answer)
- Epoxy resin
- Polyurethane resin
Correct answer: Acrylic (PMMA) resin
Acrylic (PMMA) resin is the most widely used lamination resin in prosthetics because it offers excellent strength, good workability, and proven clinical durability.
Question 2: Polypropylene is preferred over polyethylene for definitive AFO fabrication primarily because it offers:
- Lower cost
- Greater flexibility at lower temperatures
- Higher stiffness and better memory retention under cyclic loading (Correct answer)
- Easier heat-molding at lower temperatures
Correct answer: Higher stiffness and better memory retention under cyclic loading
Polypropylene provides greater stiffness and superior elastic memory compared to polyethylene, maintaining its shape better under the repetitive loads of ambulation.
Question 3: In prosthetic socket fabrication, what is the purpose of using a 'check socket' (diagnostic socket)?
- To provide the final cosmetic finish
- To verify fit, alignment, and comfort before fabricating the definitive socket (Correct answer)
- To test suspension mechanisms
- To measure socket volume for billing
Correct answer: To verify fit, alignment, and comfort before fabricating the definitive socket
A check (diagnostic) socket made from clear thermoplastic allows the prosthetist to verify fit, alignment, and pressure distribution before committing to the final definitive socket.
Question 4: Which characteristic of titanium makes it an excellent choice for endoskeletal pylon components in active prosthetic users?
- Lower cost than aluminum
- Higher strength-to-weight ratio combined with excellent corrosion resistance (Correct answer)
- Ease of field adjustment
- Radiolucency for imaging
Correct answer: Higher strength-to-weight ratio combined with excellent corrosion resistance
Titanium offers an excellent strength-to-weight ratio and outstanding corrosion resistance, making it ideal for high-activity users exposed to varied environments.
Question 5: A prosthetist notes that a patient's silicone liner is showing signs of delamination at the proximal trim line. What is the most likely cause?
- Improper donning technique causing shear stress at the proximal edge (Correct answer)
- Insufficient liner thickness
- Socket volume that is too large
- Excessive prosthetic foot plantarflexion
Correct answer: Improper donning technique causing shear stress at the proximal edge
Repeated shear stress from improper donning — particularly rolling the liner while gripping the proximal edge — causes delamination of the fabric backing from the silicone at the trim line.
Question 6: What is the functional purpose of a 'PETG' (glycol-modified polyethylene terephthalate) check socket compared to traditional polyethylene check sockets?
- Greater opacity for cosmetic assessment
- Higher heat resistance allowing autoclaving
- Greater clarity and lower forming temperature enabling easier fabrication and visual assessment (Correct answer)
- Superior structural strength for long-term use
Correct answer: Greater clarity and lower forming temperature enabling easier fabrication and visual assessment
PETG offers excellent optical clarity and a lower vacuum-forming temperature than conventional polyethylene, making it easier to fabricate clear check sockets that allow visual skin assessment.
CPO CPO Materials Science & Technology 2
Which lamination resin type is most commonly used in structural prosthetic sockets due to its balance of strength, weight, and ease of fabrication?