CHAPTER 127 Deep Digital Flexor Tendon Injuries in the Foot
Although it has long been suspected that injury to the digital portion of the deep digital flexor tendon (DDFT) is a potential cause of lameness originating in the foot, practitioners’ inability to use diagnostic imaging techniques to assess soft tissues inside the hoof has limited antemortem diagnosis of this condition. Consequently, previous reports consist of reviews of cases that were diagnosed postmortem. Since the advent of magnetic resonance imaging (MRI) and, to a lesser extent, computed tomography (CT), it has become clear that tendonitis of the DDFT is the most common soft tissue injury causing lameness in the equine foot. Tendonitis of the digital portion of the DDFT may occur alone, in conjunction with navicular bone pathology, or as one component of a complex of a multiple soft tissue injuries in the foot.
PATHOLOGY
Recent pathologic surveys revealed four types of lesions in the digital portion of the DDFT: core lesions, sagittal plane splits, insertional lesions (enthesopathy), and dorsal border lesions. Core lesions (Figure 127-1) are characterized by gross fiber disruption in the center of usually only one lobe. Core lesions most frequently span the upper extent of the T-ligament into the proximal recess of the navicular bursa but can extend a variable distance proximodistally and occasionally cause a continuous core defect from the insertion to the level of the distal aspect of the proximal phalanx.
CLINICAL EXAMINATION
Visual Inspection and Palpation
There are generally no visual or palpable abnormalities that indicate injury of the digital portion of the DDFT as the cause of lameness. Occasionally distension of the digital synovial sheath is seen in horses with a lesion that extends proximally to the level of the sheath. Even more rarely a focal, painful, firm soft tissue swelling can be appreciated on the palmar aspect of the DDFT in the distal aspect of the pastern.