If the restriction is P-A with M-L only, which listing is most likely?

• A. PI
• B. IN
• C. EX
• D. AS

Answer: (B)

In this listing system, the codes describe the main direction of the vertebral restriction. If you’re told the restriction is P-A with M-L only, that means motion is limited mainly from posterior to anterior, and the constraint occurs only in the medial-lateral axis—no extra planes of motion are involved.

The code that best matches this exact pattern is the one that encodes a P-A restriction with an M-L limitation only. The other codes imply additional directional components (for example, a posterior-inferior pattern, an extension-related pattern, or an anterior-superior pattern), which don’t fit a single-plane P-A restriction with only M-L involvement. Therefore, the IN listing is the most likely.