ARRT Lower Extremity Procedures 5 — Questions and Answers
Question 1: A patient presents with a suspected Lisfranc injury. Which projection of the foot is most useful for initial evaluation?
- Lateral projection of the foot
- AP oblique projection of the foot
- Weight-bearing AP projection of the foot (Correct answer)
- Plantodorsal axial projection
Correct answer: Weight-bearing AP projection of the foot
Weight-bearing AP projections best reveal Lisfranc (tarsometatarsal) instability by demonstrating diastasis under physiologic load.
Question 2: For the bilateral frog-leg (modified Cleaves) projection of the hips, the patient's thighs are abducted approximately how many degrees from vertical?
- 10-15 degrees
- 20-30 degrees
- 40-45 degrees (Correct answer)
- 60-70 degrees
Correct answer: 40-45 degrees
The frog-leg position requires 40–45 degrees of bilateral thigh abduction from vertical to profile the femoral necks.
Question 3: Bohler's angle (tuber-joint angle) is assessed on which projection of the calcaneus?
- AP projection
- Plantodorsal axial projection
- Lateral projection (Correct answer)
- Medial oblique projection
Correct answer: Lateral projection
Bohler's angle (normally 20–40 degrees) is measured on the lateral calcaneus projection and is decreased in calcaneal compression fractures.
Question 4: For the AP projection of the pelvis, the lower limbs are placed in how many degrees of internal rotation?
- 5 degrees
- 10 degrees
- 15 degrees (Correct answer)
- 30 degrees
Correct answer: 15 degrees
Internal rotation of 15 degrees counteracts femoral neck anteversion, placing the femoral necks parallel to the IR for a true AP pelvis.
Question 5: Which projection of the knee specifically evaluates the posterior tibial plateau for impaction fractures?
- AP projection
- Lateral projection
- Sunrise (tangential) projection
- Posteroanterior axial (Rosenberg) weight-bearing projection (Correct answer)
Correct answer: Posteroanterior axial (Rosenberg) weight-bearing projection
The Rosenberg weight-bearing PA flexion view at 45 degrees is sensitive for early joint space narrowing and posterior tibial plateau lesions.
Question 6: For a tangential (Merchant) projection of the patella, the knee is flexed approximately how many degrees and the CR is directed:
- 20 degrees; perpendicular to the IR
- 45 degrees; 30 degrees caudad from horizontal (Correct answer)
- 60 degrees; 20 degrees cephalad
- 90 degrees; parallel to the IR
Correct answer: 45 degrees; 30 degrees caudad from horizontal
The Merchant method uses 45 degrees of knee flexion with the CR angled 30 degrees caudad from horizontal to project the patellofemoral groove.
Question 7: When imaging the sesamoids of the great toe using the tangential projection, the foot is dorsiflexed and the CR is directed:
- Perpendicular to the plantar surface of the foot
- Parallel to the plantar surface and tangent to the first MTP joint (Correct answer)
- 15 degrees cephalad to the sole of the foot
- 30 degrees caudad to the dorsum of the foot
Correct answer: Parallel to the plantar surface and tangent to the first MTP joint
The CR is directed tangentially along the plantar surface of the foot at the level of the first MTP joint to profile the sesamoid bones free of superimposition.
ARRT Lower Extremity Procedures 5
A patient presents with a suspected Lisfranc injury.
Which projection of the foot is most useful for initial evaluation?