The LOD for PI is which of the following?

• A. P-A, S-I
• B. P-A, I-S
• C. P-A, M-L
• D. P-A, L-M

Answer: (B)

The main idea here is how Line of Drive (LOD) is chosen to correct a specific directional misalignment. LOD is the direction the thrust travels relative to the segment being adjusted. When a lesion is described as Posterior-Inferior (PI), the segment is thought to be positioned toward the back and toward the bottom. To bring it toward a more neutral position, the thrust is directed toward the opposite directions: from posterior to anterior to move it forward, and from inferior to superior to move it upward. Combining these two components gives a diagonal drive that addresses both the posterior and inferior aspects. So the appropriate LOD is from posterior to anterior and from inferior to superior (P-A, I-S). The other options would address different directional components (such as superior-inferior or medial-lateral directions) that don’t correct the inferior aspect of a PI lesion.