RTBC Lower Extremities Practice Test

In performing a plantodorsal axial calcaneus radiograph, the correct tube angulation is 40 degrees cephalad. This technique is specifically designed to obtain a clear view of the calcaneus (heel bone) while minimizing overlap from surrounding structures, such as the talus and the forefoot.

The rationale behind the 40-degree cephalad angulation is that it allows the X-ray beam to project through the calcaneus at an appropriate angle, producing an optimal image that shows the anatomy of the heel in detail. This angulation effectively projects the dorsum of the foot towards the film or detector, capturing the calcaneus in a way that demonstrates its shape and any potential pathologies.

Using any other angle, such as 20 degrees or 30 degrees cephalad, may not provide sufficient visualization of the structures of interest, potentially resulting in a less diagnostic image. Similarly, a caudad angle is not appropriate in this context and could lead to distortion of the anatomical details required for an accurate analysis. Thus, understanding the correct tube angulation is essential for obtaining high-quality radiographs of the calcaneus.