Growth Plate Closure in Boys' Ankles
In boys, the distal tibial and distal fibular growth plates typically close completely between ages 14 and 19 years, with complete fusion occurring as early as 14 years in some populations and universally by age 19. 1
Timing and Pattern of Closure
The distal tibial growth plate closure follows a predictable pattern:
- Earliest complete fusion: Can occur as early as 14 years of age 1
- Universal complete fusion: All males demonstrate complete fusion by 19 years 1
- Physiologic closure begins: Between ages 13-15 years (approximately 1 year later than girls) 2
- Duration of closure process: Takes approximately 18 months from initiation to completion 2
Anatomic Progression
The closure pattern is not uniform across the growth plate:
- Closure begins: Eccentrically at the ventrolateral zone of the medial malleolus, extending dorsally 2
- Closure ends: Laterally, with the anterolateral zone being the last to ossify 2
- Medial malleolus: The secondary ossification center extends into the medial malleolus between ages 7-8 years, reaching the distal tip during adolescence 3
Population Variations
There are significant ancestral differences in timing 1:
- African-American and Mexican-American males: Complete fusion as early as 14 years in both distal tibia and fibula
- European-American males: Complete fusion typically not until 16 years
Clinical Implications
During the 18-month closure period, the growth plate loses its joint-protective function, making transitional fractures (two-plane and triplane fractures) possible 2. The progressive lateral location of potential fractures correlates with the medial-to-lateral closure pattern.
Important caveat: The anteromedial undulation of the tibial physis (Kump hump or Poland's hump) develops before closure and should not be misinterpreted as premature closure or injury 4, 3.