A proposal for a new classification for the tendon of insertion of tibialis posterior.

Although the tendon of the tibialis posterior muscle (TPM) is high morphological variability, its insertion is not well defined in anatomy discussions. The aim of the work is to systematize the classification of tibialis posterior tendon insertion by anatomical dissection. Classical anatomical dissection was performed on 80 lower limbs (40 female, 40 male) fixed in 10% formalin solution. The morphology of the insertion of the tendon was evaluated, and the muscle was subjected to appropriate morphometric measurements. Four types of insertion were observed, the most common being Type III (35 cases - 43.75%): a triple distal attachment where the main tendon inserts to the navicular bone and the medial cuneiform bone, and two accessory bands insert to the medial, lateral, or intermediate cuneiform bone or to the metatarsal bones (II, III, IV, V) depending on subtypes (A-C). The second most common type was Type II (18 cases: 22.5%): a double distal attachment. Type IV (14 cases: 17.5%) was characterized by quadruple distal attachment and was also divided into three subtypes (A-B). The rarest type was Type I (13 cases: 16.25%), which was characterized by a single band: the main tendon inserts to the navicular bone and the medial cuneiform bone. The tendon of the TPM presents high morphological variability. Knowledge of the four particular types of insertions is essential for both clinicians and anatomists. Clin. Anat. 32:557-565, 2019.