Access to talar dome surface with different ankle approaches

F. Malagelada, M. Dalmau-Pastor, B. Fargues, J. Vega, R. Dega, C. Clark

Introduction: Access to the talar dome for treatment of osteochondral lesions (OCLs) can be achieved by different approaches to the ankle joint. Osteotomies are used in cases where the area to treat is not fully accessible. The recent description of an anatomical nine-grid scheme of the talus has proven useful to localize OCLs but no studies have demonstrated what approaches are indicated to access each of these zones.

Methods: Four standard soft tissue ankle approaches were performed simultaneously in ten fresh-frozen cadavers (anterolateral - AL, anteromedial - AM, posterolateral - PL, posteromedial - PM). The area of the talus that was accessible with an instrument perpendicular to the surface was documented for each of the approaches. Using ImageJ software the surface area exposed with each approach was calculated. The talar dome was divided in a nine-grid scheme and exposure to each zone was documented.

Results: The AL, AM, PL and PM approaches allow for exposure of 24%, 25%, 5%, 7% of the talar dome respectively. The AL gives access to zones 3 (completely) and 2, 5, 6 (partially) ; the AM to zones 1 (completely) and 2, 4, 5 (partially); the PL to zones 9 and 8 (partially); and the PM to zones 7 and 8 (partially).

Conclusions: A large area of the talar dome cannot be easily accessed with the use of standard soft tissue approaches (39%). Minimal or no access is achieved for grid zones 4, 5, 6 and 8. Extended exposure can be achieved with the use of osteotomies, section of the ATFL or through modified approaches. Careful preoperative planning is necessary when attempting techniques that require full exposure of a particular area of the talar dome like OATs, ACI, or MACI.