Tearing of the Calcaneal Insertions of the Superficial Digital Flexor Tendon: Treatment and Outcome

The hindlimb superficial digital flexor arises from the supracondylar fossa of the femur as a thick round tendon which is incompletely covered with muscle as far as the proximal one- third of the crus. It is intimately attached to the cranial surface of the gastrocnemius and in the distal one-third of the crus it winds around the medial surface of the gastrocnemius to lie caudally. From this point the tendon mediolaterally widens and over the apex of the calcaneus forms a curved fibrocartilagenous cap with a cranial concavity. The calcaneal insertions of the superficial digital flexor emerge from the medial and lateral margins of the cap. The calcaneal bursa is found beneath the SDF tendon from the distal quarter of the crus to the middle of the tarsus. This communicates consistently with a small bursa found between the tendon of insertion of gastrocnemius and the calcaneus. The calcaneal insertions of the SDFT are subsynovial with regard to the calcaneal bursa and form part of its abaxial walls. Distal to the fibrocartilagenous cap the SDF tendon narrows as it passes over the long plantar ligament towards its ultimate insertion via the plantar fibrocartilage on the distal extremity of the proximal phalanx and proximal extremity of the middle phalanx. Its action is to flex the digit and extend the hock which are considered largely to be mechanical effects resulting from the action of other muscles on the stifle joint. The calcaneal insertions are thus critical to its role in providing the caudal arm of the reciprocal apparatus. [...]