The ossification centre for the medial epicondyle of the humerus appears at approximately age 5–7 years. In the mnemonic CRITOE, the order of appearance is: Capitellum (1 yr), Radial head (3 yr), Internal (medial) epicondyle (5 yr), Trochlea (7 yr), Olecranon (9 yr), External (lateral) epicondyle (11 yr). Which injury pattern requires knowledge of this sequence?

• A Avulsion of medial epicondyle trapped in the elbow joint — trochlea should not appear before medial epicondyle ✓
• B Lateral condyle fracture — radial head should appear before the capitellum
• C Olecranon apophysitis — the trochlea appears after the olecranon
• D Supracondylar fracture — the lateral epicondyle appears before the medial

Explanation

The CRITOE sequence is clinically important in paediatric elbow radiography. The trochlea ossifies at ~7 years, AFTER the medial epicondyle (5 years). If a trochlear ossification centre is visible on radiograph, the medial epicondyle MUST also be visible unless it has been avulsed and trapped within the joint. Seeing the trochlea without the medial epicondyle on a post-traumatic elbow X-ray in a child mandates the diagnosis of an entrapped medial epicondyle avulsion — this fragment is entrapped within the joint and may be mistaken for the trochlea.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.