COF Lower Extremity Orthotics 2 — Questions and Answers
Question 1: A patient with drop foot following a peroneal nerve injury is best managed with which orthotic device?
- Supramalleolar orthosis (SMO)
- Ankle-foot orthosis (AFO) with dorsiflexion assist (Correct answer)
- Knee-ankle-foot orthosis (KAFO) with drop-lock knee joint
- Rigid carbon fiber foot orthosis
Correct answer: Ankle-foot orthosis (AFO) with dorsiflexion assist
An AFO with a dorsiflexion assist (spring-loaded or dynamic) compensates for absent tibialis anterior function, clearing the foot during swing phase.
Question 2: Which trimline position on a posterior leaf spring (PLS) AFO increases mediolateral ankle stability?
- Trimline moved anterior to the malleoli (Correct answer)
- Trimline moved posterior to the malleoli
- Trimline at the metatarsal heads
- Trimline at the fibular head
Correct answer: Trimline moved anterior to the malleoli
Moving the trimline anterior to the malleoli widens the brim, encasing the malleoli and providing greater mediolateral stability.
Question 3: A ground reaction AFO (GRAFO) is primarily indicated for a patient exhibiting:
- Excessive knee hyperextension during stance
- Crouch gait with excessive knee flexion during stance (Correct answer)
- Valgus knee collapse at terminal stance
- Foot drop during swing phase
Correct answer: Crouch gait with excessive knee flexion during stance
The GRAFO applies an anterior tibial force that creates a knee extension moment, correcting crouch gait caused by excessive knee flexion in stance.
Question 4: When fabricating a total contact AFO for a patient with significant spasticity, the fitter should ensure the ankle is positioned at:
- 5° plantar flexion
- Neutral (0°) or slight dorsiflexion (Correct answer)
- 10° dorsiflexion
- Maximum dorsiflexion tolerated
Correct answer: Neutral (0°) or slight dorsiflexion
Setting the ankle at neutral or slight dorsiflexion inhibits plantarflexor spasticity and promotes functional gait without excessive toe catch.
Question 5: The primary biomechanical purpose of a KAFO with an offset knee joint is to:
- Limit knee hyperextension
- Shift the ground reaction force anterior to the knee to promote passive extension (Correct answer)
- Provide active assistance during swing phase
- Control tibial rotation
Correct answer: Shift the ground reaction force anterior to the knee to promote passive extension
The offset joint places the knee mechanical axis posterior to the anatomical joint, moving the GRF anterior and allowing stance-phase stability without locking.
Question 6: A patient with a painful subtalar joint arthritis would most benefit from which foot orthotic design?
- Rigid longitudinal arch support only
- Custom total-contact foot orthosis with a medial heel wedge (Correct answer)
- Flexible prefabricated arch support
- Metatarsal pad alone
Correct answer: Custom total-contact foot orthosis with a medial heel wedge
A custom total-contact orthosis limits subtalar motion by distributing load evenly and a medial heel wedge can reduce inversion stress on the joint.
Question 7: Which material property is MOST important when selecting a thermoplastic for a dynamic AFO intended to store and return energy during gait?
- High creep resistance
- High elastic modulus with good resilience (Correct answer)
- Low Shore hardness
- High moisture absorption
Correct answer: High elastic modulus with good resilience
Energy-storing AFOs require materials with high stiffness (modulus) and the ability to spring back (resilience) to propel the foot into swing.
COF Lower Extremity Orthotics 2
A patient with drop foot following a peroneal nerve injury is best managed with which orthotic device?