IN-DEPTH: THE RELATIONSHIP BETWEEN IMAGING FINDINGS AND LAMENESS


ing on the horse’s discipline. Persistent hypervas- cularity at this stage, even with return to normal fiber pattern, is worrisome to the authors for the horse’s prognosis and particularly the ability to in- crease work without further injury. At this stage, the authors re-evaluate the horse’s rehabilitation program both in terms of management (i.e., horse and trainer/owner compliance) and rehabilitation modalities. In general, the authors’ preference is for a horse to


be cantering under saddle for 4 weeks and doing well on recheck examination prior to any turnout in a sizeable paddock, but understand that this may not be feasible for all horses depending on temper- ament, etc. After this point, increase in work in- tensity is very disciplined and horse-specific but for all horses the authors like to see complete resolution of the lesion on gray-scale as well as complete re- gression of vasculature on Doppler prior to such an increase. Additionally, the lesion, should appear “hard” on elastography. Once a horse has returned to full work, it is common in the authors’ practice to re-assess the old injury site every 3–6 months or sooner (depending on severity) to monitor for subtle signs of re-injury and then adjust work level and/or rehabilitation accordingly. In particular, the au- thors utilize Doppler imaging to evaluate for poten- tial return of vascularity and elastography to assess for a “softening” of the tendon/ligament that may precede any changes in fiber pattern. The above recommendations are basic exercise components of a rehabilitation protocol. There are many other options including, but not limited to, underwater treadmill, salt water spa, vibration plate, laser, shockwave, and therapeutic ultrasound that the authors’ utilize depending on the case and the owners’ desire and financial ability. Where ap- plicable, these specific modalities and therapies are discussed below under specific conditions.


Digital Flexor Tendon Sheath Pathology


Pathology within the digital flexor tendon sheath (DFTS) can be challenging to accurately diagnose, treat, and rehabilitate. New methods have been described to better define DFTS pathology such as standard CT,28 contrast tenography utilizing either radiography36 or CT,29 saline distension of the DFTS utilizing ultrasonography or MRI,37 and dynamic ultrasonography.38,39 In the authors’ practice, it is common to utilize multiple imaging modalities in addition to tenoscopy in order to best characterize and treat DFTS pathology as well as provide owners with an accurate prognosis. Unlike “simple” tendon and ligament lesions described above, lesions/tears within the DFTS are at risk of adhesion formation and restriction from such adhe- sions and/or palmar/plantar annular ligament con- striction which cause pain and can substantially limit performance.39–41 For this reason, rehabilita- tion of these injuries in the authors’ practice also includes specific passive and active range of motion


(ROM) exercises. Passive ROM exercises involve a human moving the limb, and more specifically in this case, the fetlock joint region through the normal ROM, while active ROM exercises include walking in the underwater treadmill42 and walking or trot- ting over ground poles. Water height in the under- water treadmill is adjusted on a case by case basis depending on the horse’s comfort level. In addition, the authors often utilize therapeutic ultrasound, la- ser, and friction massage to try to limit and/or pre- vent adhesion formation, which is associated with poor prognosis.


Suspensory Branch Pathology


As with most soft tissues, ultrasound is the imaging modality of choice when evaluating the suspensory branches. Due to the ease of diagnosis via ultra- sound, further advanced imaging such as MRI is usually not necessary. In the authors’ opinion, a complete radiographic examination of the fetlock re- gion is always recommended in suspensory branch cases to determine the full extent of the osseous changes of the proximal sesamoid bones, fetlock joint, and potentially splint bones as these changes can greatly affect prognosis, rehabilitation timeline, and treatment options. Confirming or diagnosing suspensory ligament branch disease can be difficult with many horses having ultrasonographic abnor- malities that are not necessarily a cause of clinical lameness.43–45 When trying to determine or con- firm a suspensory branch lesion as the cause of lameness and/or an active lesion, besides using clin- ical judgment such as pain on palpation and positive flexion test, Doppler is frequently used in the au- thors’ practice. As previously discussed, there is little research to support this,12 but in the authors’ experience increasing levels of hypervascularity on Doppler ultrasound are seen with increasing de- grees of lameness and therefore suggestive of an active and clinical injury. An additional imaging modality that can be useful in suspensory branch injuries is nuclear scintigraphy. Nuclear scintigra- phy is helpful to determine the amount of osseous response to a given lesion as well as again determine whether the lesion is active. Typical ultrasonographic abnormalities of suspen-


sory branches are changes in shape, enlargement, diffuse or discrete fiber abnormalities, and margin irregularities. Important additional abnormalities to note, which affect prognosis and rehabilitation protocols, are insertional fiber changes at the at- tachment on the sesamoid bones with associated degree of osseous changes (evaluated in conjunction with radiographs), and presence and degree of periligamentous fibrosis. As ligament and bone in- terfaces are known weak spots in healing, injuries involving this interface such as resorptive or os- seous cyst-like lesions, slow the rehabilitation timeline down as well as decrease prognosis.46 Periligamentous fibrosis is more commonly seen in


AAEP PROCEEDINGS  Vol. 66  2020 33


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