ARRT - American Registry of Radiologic Technologists Lower Extremity Procedures Questions and Answers — Questions and Answers
Question 1: A patient arrives in the emergency department with a traumatic injury to the hip and is unable to move the affected leg. To obtain a lateral projection of the proximal femur, which of the following methods should the technologist employ?
- Unilateral 'frog-leg' (Modified Cleaves method)
- AP Oblique (Judet method)
- AP Pelvis with internal rotation
- Axiolateral inferosuperior (Danelius-Miller method) (Correct answer)
Correct answer: Axiolateral inferosuperior (Danelius-Miller method)
The axiolateral inferosuperior projection, also known as the Danelius-Miller or cross-table lateral method, is specifically designed for trauma situations where the patient cannot move the affected leg. [7, 11, 12, 17] It provides a lateral view of the femoral head, neck, and trochanters by directing the central ray horizontally, avoiding the need for patient manipulation.
Question 2: When evaluating an AP pelvis radiograph for proper positioning, which of the following indicates the patient was not rotated?
- The lesser trochanters are not visible.
- The iliac alae and obturator foramina are symmetric. (Correct answer)
- The sacrum and coccyx are centered to the pubic symphysis.
- The greater trochanters are seen in profile.
Correct answer: The iliac alae and obturator foramina are symmetric.
Symmetry of the iliac alae (wings) and the obturator foramina is the primary indicator that the pelvis is not rotated. [3, 4] If one iliac ala appears wider and the corresponding obturator foramen appears more closed, it signifies rotation toward that side.
Question 3: A radiograph of an AP oblique foot demonstrates significant overlapping of the bases of the third, fourth, and fifth metatarsals. Which of the following is the most likely cause of this appearance?
- Insufficient cephalic angulation of the central ray.
- Excessive medial rotation of the foot. (Correct answer)
- Plantar flexion of the foot during exposure.
- Insufficient medial rotation of the foot.
Correct answer: Excessive medial rotation of the foot.
The goal of the AP oblique projection of the foot is to separate the metatarsals, typically requiring 30-40 degrees of medial rotation. [19, 33] When the bases of the lateral metatarsals are excessively overlapped, it indicates the foot was rotated too much, exceeding the optimal degree of obliquity. [24]
Question 4: An emergency room physician orders an ankle series to evaluate the integrity of the entire ankle mortise. Which projection is specifically performed to demonstrate an open tibiotalar and distal tibiofibular joint?
- AP with 45-degree lateral rotation
- Lateral mediolateral
- AP oblique with 15-20 degree medial rotation (Correct answer)
- AP with dorsiflexion
Correct answer: AP oblique with 15-20 degree medial rotation
The AP oblique projection with 15-20 degrees of medial rotation is known as the mortise view. [6, 15, 22, 23] This specific degree of rotation places the intermalleolar line parallel to the image receptor, which opens the entire ankle mortise joint for evaluation without bony overlap.
Question 5: Which of the following projections is specifically designed to demonstrate the intercondylar fossa of the femur, often referred to as a 'tunnel' view?
- PA axial (Camp-Coventry method) (Correct answer)
- AP oblique with medial rotation
- Tangential (Settegast method)
- Lateral mediolateral
Correct answer: PA axial (Camp-Coventry method)
The PA axial (Camp-Coventry method), along with other methods like the Holmblad, are 'tunnel' views designed to project the central ray directly through the intercondylar fossa. [5, 8] This requires patient positioning that involves significant knee flexion to visualize the fossa without superimposition from the patella. [10, 16]
Question 6: A technologist is performing a plantodorsal (axial) projection of the calcaneus. What is the primary purpose of directing the central ray with a 40-degree cephalic angle?
- To open the talonavicular joint space.
- To project the metatarsals free of superimposition.
- To place the posterior aspect of the calcaneus in profile.
- To elongate the calcaneus and demonstrate the subtalar joint. (Correct answer)
Correct answer: To elongate the calcaneus and demonstrate the subtalar joint.
The steep 40-degree cephalic angulation for the plantodorsal (axial) projection is necessary to elongate the body of the calcaneus, projecting it free from the superimposing structures of the foot. This view clearly demonstrates the tuberosity and the middle articulation of the subtalar joint. [2, 29]
ARRT - American Registry of Radiologic Technologists Lower Extremity Procedures Questions and Answers
A patient arrives in the emergency department with a traumatic injury to the hip and is unable to move the affected leg.
To obtain a lateral projection of the proximal femur, which of the following methods should the technologist employ?