DPM Diagnostic Imaging Interpretation 2 — Questions and Answers
Question 1: On a lateral foot radiograph, which landmark is used to measure the calcaneal inclination angle?
- Inferior surface of the calcaneus and the floor (Correct answer)
- Posterior superior calcaneal tuberosity and the talus
- Anterior process of the calcaneus and the navicular
- Medial calcaneal tubercle and the cuboid
Correct answer: Inferior surface of the calcaneus and the floor
The calcaneal inclination angle is measured between the inferior surface of the calcaneus and the weightbearing surface (floor), normally 18–22°.
Question 2: A stress fracture of the second metatarsal shaft in a dancer would most characteristically appear on plain radiograph as:
- Lytic lesion with periosteal reaction after 2–3 weeks (Correct answer)
- Immediate cortical break visible on initial films
- Diffuse osteopenia of the metatarsal head
- Pathological dislocation of the second MTP joint
Correct answer: Lytic lesion with periosteal reaction after 2–3 weeks
Stress fractures often show no findings on initial radiographs; periosteal reaction and endosteal callus typically appear 2–3 weeks after onset.
Question 3: Which MRI sequence is most sensitive for detecting bone marrow edema in acute osteomyelitis of the foot?
- STIR (Short Tau Inversion Recovery) (Correct answer)
- T1-weighted without contrast
- T2-weighted fat-saturated
- Gradient echo
Correct answer: STIR (Short Tau Inversion Recovery)
STIR sequences suppress fat signal and are highly sensitive for detecting bone marrow edema, making them the sequence of choice for early osteomyelitis.
Question 4: On a dorsoplantar (DP) radiograph, the intermetatarsal angle (IMA) in moderate hallux valgus typically measures:
- 13–20° (Correct answer)
- 5–8°
- 0–5°
- Greater than 25°
Correct answer: 13–20°
Moderate hallux valgus is associated with an IMA of 13–20°; angles above 20° indicate severe deformity.
Question 5: A 'C-sign' on a lateral ankle radiograph is pathognomonic of which condition?
- Talocalcaneal coalition (Correct answer)
- Subtalar joint arthritis
- Plantar fasciitis
- Os trigonum syndrome
Correct answer: Talocalcaneal coalition
The C-sign, formed by the outline of the talar dome and sustentaculum tali on lateral view, is a classic radiographic sign of talocalcaneal coalition.
Question 6: On ultrasound, a normal plantar fascia thickness at its calcaneal insertion measures approximately:
- 2–4 mm (Correct answer)
- 6–8 mm
- 8–10 mm
- Less than 1 mm
Correct answer: 2–4 mm
Normal plantar fascia thickness is 2–4 mm; measurements above 4 mm at the insertion are consistent with plantar fasciitis.
Question 7: Which radiographic finding on a weightbearing lateral view suggests midfoot collapse in Charcot neuroarthropathy?
- Reversal of the talar-first metatarsal angle (negative Meary's angle) (Correct answer)
- Increased calcaneal inclination angle above 25°
- Widening of the Lisfranc joint space
- Fragmentation isolated to the calcaneus
Correct answer: Reversal of the talar-first metatarsal angle (negative Meary's angle)
A negative (sagging) Meary's angle on weightbearing lateral view indicates plantar midfoot collapse, the hallmark of Charcot midfoot rocker-bottom deformity.
DPM Diagnostic Imaging Interpretation 2
On a lateral foot radiograph, which landmark is used to measure the calcaneal inclination angle?