Distribution of Subchondral Bone Puncture Strength in the Talus and Tibial Plafond: A Biomechanical Study.

We investigated talus and tibial plafond subchondral bone puncture strength based on surface location. Puncture tests of the subchondral bone were performed in 9 equal zones on the articular surface of 12 cadaver specimens aged 49.1 years (range, 36-56 years). Compressive load was applied through a microfracture awl at 2 mm/min. Puncture strength was defined as the first load drop in load-deflection curves. In the talus, zone 1 (215 ± 91 N) and zone 2, the anterior medial and anterior middle zones, had significantly greater puncture strength than zones 7, 8, and 9, the posterior medial, middle, and lateral zones (104 ± 43 N, 115 ± 43 N, and 102 ± 35 N, respectively; P < .001). In the tibial plafond, zone 3, the anterior-lateral zone, and zone 7, the posterior medial zone, had significantly greater strength than zone 8, the posterior middle zone (202 ± 72 N, 206 ± 121 N, and 112 ± 65 N, respectively; P < .001) These results suggest that the subchondral bone is significantly weaker to penetrative force in the posterior region than in the anterior region of the talar dome and of the tibial plafond. These findings may have implications for microfracture awl design and for understanding the complex anatomy and physiology of the ankle joint. LEVELS OF EVIDENCE: Controlled laboratory study.