MRI of the tibioastragalus anticus of Gruber muscle: a rare accessory muscle and normal anatomical variant

Abstract

We present the case of a 31-year-old man who sustained a hyperplantar flexion injury of his right ankle, and was evaluated using computed tomography and MRI to assess for osseous and ligamentous injury. The MRI and CT studies demonstrated a tibioastragalus anticus of Gruber (TAAG) muscle in the lower limb's anterior compartment. To our knowledge, the imaging of this muscle has not been previously described. The TAAG muscle arises from the lower third of the anterolateral tibia and the interosseous membrane. Its tendon passes laterally, deep to the tibialis anterior and extensor hallucis longus tendons, and inserts onto the anterior superolateral neck of the talus in a fan-like manner. Knowledge and recognition of this tendon are important for both diagnostic accuracy and surgical planning, and could potentially be used as a tendon transfer or graft in the appropriate clinical setting. The presence of this accessory muscle should not be confused with a pathological condition.

Anatomical variation in the ankle and foot: from incidental finding to inductor of pathology. Part I: ankle and hindfoot

“…The muscle arises from the lower third of the anterolateral tibia and interosseous membrane and inserts onto the anterolateral aspect of the neck of the talus. The tendon is deep to the tibialis anterior and extensor hallucis longus tendon [59]. This accessory muscle can be used for tendon transfer or graft.…”

Accessory Tibionavicular Muscle: An Unusual Cause of Medial Ankle Pain

“…5,6 The commonly described accessory or anomalous around the ankle and foot include the flexor digitorum accessorius longus, the accessory soleus, the peroneocalcaneus internus, tibiocalcaneus internus, the tibioastragalus anticus of Gruber muscle, and the accessory peroneal muscles (►Table 1). 1,[7][8][9][10][11][12] We describe a case of dorsomedial ankle pain in a patient arising due to partial thickness tear of a new accessory muscle at the ankle in an 18-year-old male football player. We highlight the clinical presentation, role of MRI in its accurate diagnosis including its successful management with US-guided platelet-rich plasma (PRP) therapy, and reviewassociated literature.…”

“…The commonly described accessory or anomalous around the ankle and foot include the flexor digitorum accessorius longus, the accessory soleus, the peroneocalcaneus internus, tibiocalcaneus internus, the tibioastragalus anticus of Gruber muscle, and the accessory peroneal muscles ( Table 1 ). 1 7 8 9 10 11 12 …”