Maximum Ankle Plantarflexion and Dorsiflexion Allow for Optimal Arthroscopic Access to the Talar Dome: An Anatomic 3-Dimensional Radiography Study

Abstract

Purpose: (1) to improve the comprehension of the topographical position of the talar dome beneath the inferior articular surface of the tibia and, (2) to illustrate the changes of possible access to the articular surface of the talar dome during arthroscopic treatment of talar osteochondral defects in an anatomical model. Methods: Twenty matched pairs (n = 40) of anatomical ankle specimen were used. All specimens were mounted in a standardized fashion, 3-dimensional radiography was performed in 4 defined positions (maximum dorsiflexion, neutral position, noninvasive distraction, and maximum plantarflexion). All radiographs were analyzed and statistically compared. Results: Anterior accessibility was highest in maximum plantarflexion (medial: 49.20 ± 9.86%, lateral: 48.19 ± 8.85%), followed by non-invasive distraction (medial: 33.60 ± 7.96%, lateral: 31.98 ± 8.30%). Neutral position (medial: 19.34 ± 6.90%, lateral: 17.54 ± 6.63%) and dorsiflexion (medial: 15.36 ± 5.03%, lateral: 13.88 ± 4.33%) were not able to significantly increase accessibility. Posterior accessibility was greatest in maximum dorsiflexion (medial: 56.69 ± 9.65%, lateral: 46.82 ± 8.36%), followed by neutral position of the ankle joint (medial: 40.95 ± 8.28%, lateral: 31.06 ± 6.92%). Noninvasive distraction (medial: 31.41 ± 8.18%, lateral: 22.99 ± 7.63%) was still significantly better than plantarflexion (medial: 14.54 ± 5.10%, lateral: 13.89 ± 3.14%) and slightly increased accessibility to the talar dome. Medially, a central area of 5.89 ± 9.76% was accessible by maximum plantarflexion and maximum dorsiflexion from anterior and posterior, respectively, laterally a central blind spot of 4.99 ± 8.61% was detected. Conclusions: From an anatomical point of view, maximum joint positions of the ankle (i.e., plantarflexion and dorsiflexion) allow for better access to the talar dome in anterior and posterior ankle arthroscopy. Noninvasive distraction may increase accessibility in anterior approaches, but has no benefit from posterior. Clinical Relevance: This study provides insight into the morphology of the ankle joint in a standardized laboratory setup and illustrates the influence of different surgically relevant ankle joint positions. The presented data allow for better preoperative planning for the arthroscopic treatment of talar osteochondral defects.