Tendon Lacerations

Chapter 81Tendon Lacerations

Tendon lacerations are serious injuries in horses because of the loss of the biomechanical function of the tendon, the slow return of tendon strength, the immediate strenuous loading demanded by a horse, and the complications of scarring. Nonetheless, early diagnosis, wound management, limb support, and long-term surgical and medical management have resulted in a good prognosis for most horses with extensor tendon lacerations and a fair prognosis for most of those with flexor tendon lacerations.1,2 The extensor (dorsal) aspect of the limb is often damaged by wire or a sharp object over which the horse has jumped. The flexor (palmar or plantar) aspect of the limb may be traumatized by circumferential wire injuries, landing on a sharp object, or being struck. The latter may be self-inflicted or from another horse.


Gross Appearance of the Wound

Any laceration over the dorsal or palmar/plantar surface of the limb distal to the stifle or elbow, especially across the dorsal aspect of the tarsus, distal dorsal aspect of the tarsus, dorsal metatarsal region, distal aspect of the radius, dorsal metacarpal region, and dorsal fetlock region may involve a tendon (Figure 81-1). Extensor tendons and the superficial digital flexor tendon (SDFT) are positioned directly under the skin; therefore minor-appearing wounds can transect these tendons completely. Direct visual inspection may reveal transected tendon fibers protruding from the wound. However, injuries sustained at the gallop may result in a skin wound removed from the site of tendon damage because of the movement of the skin during exercise. The position of the wound relative to synovial structures should be evaluated with care because concurrent synovial contamination or infection reduces the prognosis and necessitates specific emergency treatment.

Evaluation of Gait

Each tendon serves a biomechanical function. Complete severance of a tendon results in a posture or gait change, which may be pathognomonic for disruption of the tendon integrity.

Extensor Tendons

Transection of an extensor tendon below the carpus produces a reduced ability to extend the digit, which is detected as an exaggerated, rapid (uncontrolled) dorsal flip of the hoof at the walk. This subtle change is easiest to detect if the lateral and common (or long) digital extensor tendons are transected completely. Intermittently the horse knuckles at the fetlock joint and places the digit on the dorsal surface of the pastern and fetlock joint. The gait abnormality is more obvious in a hindlimb and with lacerations in close proximity to the fetlock. Remaining peritendonous fascial attachments provide some support in horses with more proximal injuries. Horses with extensor tendon lacerations bear weight fully in a normal posture, unless other aspects of the wound create lameness and pain.

Transection of extensor tendons proximal to the carpus and at, or just proximal to, the tarsus also commonly occurs. Proximal to the carpus, transection of the extensor carpi radialis and common digital extensor tendons is most frequent. Flexion of the carpus may cause pain. The tendon sheath is often involved.

Proximal or dorsal to the tarsus, transection of the long digital extensor, cranialis tibialis, and fibularis (peroneus) tertius tendons is most frequent. imageIf the fibularis tertius is disrupted, the hock can be extended while the stifle is flexed, indicating loss of the reciprocal apparatus. The gastrocnemius tendon develops a characteristic wrinkle in this extended position (see Figure 80-2 and page 802). The degree of gait abnormality may be mild. Transection of all the extensor tendons over the tarsus still allows full weight bearing with the foot flat on the ground. A greater tarsal extension during the swing phase of the stride and intermittent knuckling of the digit can be detected.

Jun 4, 2016 | Posted by in EQUINE MEDICINE | Comments Off on Tendon Lacerations

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