Which radiographic view is most useful to diagnose pars interarticularis fracture?

• A. AP view
• B. Lateral view
• C. Oblique views
• D. Flexion-extension view

Answer: (C)

Oblique views are most useful because they place the pars interarticularis in profile between the posterior elements, making a fracture line through the pars visible. This projection creates the classic appearance of a Scottie dog, and a fracture shows up as a radiolucent line through the pars—the collar of the dog.

AP views often obscure the pars due to superimposition of surrounding bones, and lateral views, while they show alignment and canal details, don’t visualize the pars fracture well because of overlapping structures. Flexion-extension views are used to assess instability and motion at a segment, not to optimize fracture visualization. If radiographs are inconclusive but suspicion remains, CT is more sensitive for detecting pars defects.