Achilles tendon complex: The anatomy of its insertional footprint on the calcaneus and clinical implications

Abstract

The Achilles tendon is the largest, and most commonly torn tendon in the body. The Achilles is usually torn at a region of relative hypo-vascularity proximal to its insertion. However, partial thickness tears and other pathologies often occur at its insertion on the calcaneus. Anatomically, the insertion is a confluence of the gastrocnemius and soleus muscles that fuse to form a myotendinous unit on the posterosuperior aspect of the calcaneus. This review aims to reveal the insertional footprint as individual fascicular components attaching to facets of calcaneal tuberosity. Understanding this anatomy is essential for interpreting tear patterns and surgical implications.

Keywords: Achilles complex; Achilles insertion; Achilles rupture; Achilles tear; Achilles tendon; Calcaneal tuberosity.

Fig. 1

Cadaveric specimen dissected so coronal view of calcaneus can be appreciated. Figure shows insertion footprints of Achilles sub-tendons, as well as location of retrocalcaneal bursa.

Fig. 2

Cadaveric specimen dissected so coronal view of calcaneus and Achilles tendon can be appreciated. Figure shows insertions of sub-tendons of both gastrocnemius bellies and soleus muscles into their respective calcaneal facets.

Fig. 3

Cadaveric specimen dissected so Achilles tendon can be appreciated. Figure shows the bundles of the Achilles tendon. The tendon of the medial head of the gastrocnemius is reflected back on itself to reveal the deeper sub-tendons of the Achilles footprint.

Fig. 4

Lateral radiograph of the ankle demonstrates the insertional anatomy of the calcaneus with the superficial facet (thin arrow), middle facet (thick arrow), and inferior facet (bent arrow) clearly demonstrated.

Fig. 5

Sagittal PD MRI of the ankle demonstrates the normal anatomy of the Achilles tendon in relation to the superior facet (thin arrow) corresponding to the location of the retrocalcaneal bursa, the middle facet (thick arrow) corresponding to the deep structures of the Achilles tendon complex, and the inferior facet (bent arrow) corresponding to the superficial structures of the Achilles tendon complex.

Fig. 6

Sagittal PD fat saturated MRI of the ankle demonstrates a patient with Haglunds deformity, where there is retrocalcaneal bursitis occupying the region of the superior facet (arrow).

Fig. 7

a)Sagittal STIR MRI of the ankle demonstrates partial thickness isolated tear of the Achilles tendon insertion at the inferior calcaneal facet (arrow) with retraction of the tendon superiorly. b)Axial PD fat saturated MRI of the ankle (same patient) demonstrates partial thickness tear of the superficial fibers of the Achilles tendon complex just proximal to its insertion on the inferior facet (arrow). c) Coronal PD MRI of the ankle (same patient) shows a corrugated and wavy morphology of the medial gastrocnemius myotendinous junction confirming isolated medial gastrocnemius tear (arrow). Note the normal intact morphology of the soleus muscle (thick arrow).

Fig. 7

a)Sagittal STIR MRI of the ankle demonstrates partial thickness isolated tear of the Achilles tendon insertion at the inferior calcaneal facet (arrow) with retraction of the tendon superiorly. b)Axial PD fat saturated MRI of the ankle (same patient) demonstrates partial thickness tear of the superficial fibers of the Achilles tendon complex just proximal to its insertion on the inferior facet (arrow). c) Coronal PD MRI of the ankle (same patient) shows a corrugated and wavy morphology of the medial gastrocnemius myotendinous junction confirming isolated medial gastrocnemius tear (arrow). Note the normal intact morphology of the soleus muscle (thick arrow).

Fig. 7

a)Sagittal STIR MRI of the ankle demonstrates partial thickness isolated tear of the Achilles tendon insertion at the inferior calcaneal facet (arrow) with retraction of the tendon superiorly. b)Axial PD fat saturated MRI of the ankle (same patient) demonstrates partial thickness tear of the superficial fibers of the Achilles tendon complex just proximal to its insertion on the inferior facet (arrow). c) Coronal PD MRI of the ankle (same patient) shows a corrugated and wavy morphology of the medial gastrocnemius myotendinous junction confirming isolated medial gastrocnemius tear (arrow). Note the normal intact morphology of the soleus muscle (thick arrow).

Fig. 8

Sagittal STIR and axial PD FS MRI of the ankle demonstrates partial thickness tearing of the soleus tendon at its insertion on the lateral aspect of the middle calcaneal facet (white arrow). Note the intact medial gastrocnemius tendon at its insertion on the inferior calcaneal facet (yellow arrow).

Fig. 9

PDFS transverse of Left foot: Achilles tendon partial thickness sub-tendon tears at footprint of the middle facet.

Fig. 10

PDFS coronal of an ankle demonstrates an intact medial gastrocnemius tendon inserting on inferior facet of calcaneus.

Fig. 11

PDFS coronal of an ankle shows a partial thickness tear of the lateral gastrocnemius sub-tendon at its insertion on the lateral aspect of the middle facet of the calcaneus.

Fig. 12

Sagittal STIR and axial PD FS MRI of the ankle demonstrates partial thickness tearing of the lateral gastrocnemius insertion at the lateral aspect of the middle calcaneal facet (white arrows). Note the intact medial gastrocnemius tendon insertion on the inferior facet (yellow arrow).