CO Orthotic Assessment, Prescription & Device Design 3 — Questions and Answers
Question 1: A practitioner is designing a cervical orthosis for a C5–C6 fracture that requires strict motion restriction in all planes. Which orthosis provides the highest level of cervical immobilization?
- Soft foam cervical collar
- Philadelphia collar
- Miami J collar
- Halo vest orthosis (Correct answer)
Correct answer: Halo vest orthosis
The halo vest provides the greatest restriction of cervical motion in all planes by rigidly attaching to the skull via pins and to the thorax via a vest.
Question 2: During orthotic gait analysis, a patient with an AFO demonstrates a forward trunk lean during mid-stance. Which orthotic modification is most likely to correct this compensatory movement?
- Increase AFO plantar flexion stop to limit dorsiflexion
- Reduce AFO dorsiflexion resistance to allow more forward tibial progression (Correct answer)
- Add a supramalleolar extension to the AFO
- Apply a metatarsal pad inside the AFO
Correct answer: Reduce AFO dorsiflexion resistance to allow more forward tibial progression
Excessive resistance to dorsiflexion prevents forward tibial progression, forcing the trunk to lean forward to advance the center of mass; reducing resistance restores normal sagittal kinematics.
Question 3: When selecting shell material for a custom spinal orthosis for a heavy laborer requiring lumbar support during lifting, which material property is most critical?
- High elastic modulus to resist deformation under cyclic load (Correct answer)
- Low density to minimize device weight
- High optical clarity for aesthetics
- Low melting temperature for ease of fabrication
Correct answer: High elastic modulus to resist deformation under cyclic load
A high elastic modulus (stiffness) ensures the orthotic shell maintains its shape and provides consistent support rather than deforming under repeated heavy loads.
Question 4: A patient with rheumatoid arthritis has MCP joint subluxation with ulnar drift. A resting hand orthosis is prescribed. What is the primary design goal?
- Immobilize the wrist in slight extension and position MCP joints in neutral alignment to reduce deforming forces (Correct answer)
- Maximize grip strength by positioning all joints in full flexion
- Provide dynamic resistance to encourage active extension
- Restrict sensory feedback to reduce pain perception
Correct answer: Immobilize the wrist in slight extension and position MCP joints in neutral alignment to reduce deforming forces
A resting hand orthosis positions the wrist in slight extension and MCP/IP joints near neutral to relieve pain, reduce inflammation, and counteract the ulnar deforming forces.
Question 5: The neutral calcaneal stance position (NCSP) differs from the relaxed calcaneal stance position (RCSP) in that NCSP:
- Measures the calcaneal angle with the subtalar joint in its fully pronated position
- Measures the calcaneal angle with the subtalar joint positioned in neutral, typically showing less valgus than RCSP (Correct answer)
- Is always identical to RCSP in patients with normal arch height
- Represents the calcaneal position during active push-off
Correct answer: Measures the calcaneal angle with the subtalar joint positioned in neutral, typically showing less valgus than RCSP
NCSP is measured with the subtalar joint in neutral, so it typically shows a less everted (or even inverted) calcaneus compared to RCSP which reflects the weight-bearing pronated position.
Question 6: A floor reaction AFO is indicated for which of the following clinical presentations?
- Spastic equinus with clonus
- Crouch gait secondary to weak quadriceps and plantarflexors in a child with cerebral palsy (Correct answer)
- Isolated foot drop with normal proximal strength
- Severe spasticity requiring maximum dorsiflexion block
Correct answer: Crouch gait secondary to weak quadriceps and plantarflexors in a child with cerebral palsy
A floor reaction AFO applies an anteriorly directed force at the pretibial shell during stance, generating a knee extension moment that compensates for quadriceps weakness in crouch gait.
Question 7: When using a computerized pressure mapping system for orthotic prescription, peak pressure values above which threshold (kPa) are generally considered clinically significant in diabetic foot management?
- 100 kPa
- 200 kPa (Correct answer)
- 500 kPa
- 700 kPa
Correct answer: 200 kPa
A threshold of approximately 200 kPa is commonly used in diabetic foot literature as the upper limit of safe plantar pressure; values above this are associated with increased ulceration risk.
CO Orthotic Assessment, Prescription & Device Design 3
A practitioner is designing a cervical orthosis for a C5–C6 fracture that requires strict motion restriction in all planes.
Which orthosis provides the highest level of cervical immobilization?