Extensor Tendon Lacerations

Anatomy
The long digital extensor tendon and the lateral digital extensor tendon course over the dorsal and dorsolateral aspect of the tarsus, respectively, joining together on the dorsal aspect of the proximal third of the third metatarsus (MtIII), to insert onto the extensor process of the distal phalanx. Their main role is to supply passive resistance to flexion of the distal and proximal interphalangeal joints (Rooney 1987).

Clinical presentation
Despite often having extensive soft tissue damage, the degree of lameness is usually minimal. Complete transection of both tendons results in a characteristic dorsal ‘flick’ of the foot towards the end of the forward swing phase of the stride, just prior to hoof placement. Knuckling over onto the dorsal aspect of the fetlock is usually seen in wounds where all extensor structures have been severed; however, some proximal wounds may have enough peritendonous fascial attachments present to prevent this from occurring, at least initially (Bertone 1995).

Treatment
Wounds should be assessed on presentation for extent of soft tissue damage, degree of contamination and for evidence of compromised distal limb perfusion. Distal limb perfusion is assessed by a combination of digital pulse palpation, colour-flow Doppler and subjective assessment of distal limb warmth. The main blood supply to the distal limb is via the lateral plantar metatarsal artery. This artery is directly below the skin in the proximal third of the limb, and is particularly exposed to tourniquet-type wire wounds. Damage may cause clotting in the vessel several days after the initial trauma. […]