Which structure is represented by the better (B) in a lateral digit radiograph?

In a lateral digit radiograph, the structure represented by the better (B) typically refers to the anatomical landmark that is most clearly visualized in that view. In the case of the fifth digit, which is the little toe, the proximal interphalangeal (PIP) joint is positioned between the distal phalanx and the proximal phalanx.

When the fifth digit is imaged in a lateral view, the PIP joint will appear prominently because it is centrally located along the digit and allows for a clear depiction of the articulating surfaces from that angle, making it typically stand out. The alignment of the bones around this joint is such that it provides a good representation of joint space, which is important for assessing potential joint pathology, positioning, or alignment issues.

On the other hand, other anatomical structures like the distal phalanx, proximal phalanx, or metatarsophalangeal joint may not be as distinctly captured in a lateral view due to their positioning or alignment. The PIP joint’s distinct articulation and positioning in relation to the other structures contribute to its clarity in a lateral radiographic representation of the fifth digit.