Ultrasonography in the Diagnosis of Lameness

Introduction
Diagnostic ultrasound is now an accepted and routine procedure for evaluation of soft tissue injuries in the horse. The increased frequency of the use of this technique and the rapidly improving technology now enables even small portable ultrasound machines to provide good quality, diagnostic images. This presentation will address the techniques and basic interpretative skills needed to produce diagnostic quality ultrasound images.

Indications for an ultrasonographic examination
(a) Investigation of soft tissue injury.
(b) Investigation of the surface of bone.
(c) Investigation of joint abnormalities.
(d) Investigation of wounds.
(e) Investigation of an area causing lameness, as determined by diagnostic anaesthesia, with negative clinical and radiographic findings, or radiographic findings that suggest a soft tissue injury.
(f) Evaluation of structures likely to be concurrently or previously injured.
(g) Comparative contralateral limb

Ultrasonographic equipment:
In most practice situations, a portable ultrasound machine is essential. There are a multitude of such machines available on the market, but below (see table 1) are a list of some features to consider when trying out an ultrasound scanner.

Ultrasonographic technique for the metacarpal and pastern regions
Careful preparation of the area is essential if good diagnostic images are to be obtained. The skin should ideally be clipped with fine-bladed clippers, taking care to avoid causing damage to the skin as this can cause swelling after scanning. For evaluation of the flexor tendons and proximal suspensory ligament, a narrow strip of skin from the very palmar aspect of the limb is all that needs to be clipped. For the accessory ligament of the deep digital flexor tendon and the suspensory ligament branches, the hair also needs to be clipped from the medial and lateral aspects of the limbs directly overlying these structures. In some cases, owners/trainers request for the limbs to be scanned without clipping. In such circumstances, it has to be emphasised that subtle pathology may be missed and it is usually not possible to obtain a diagnostic quality scan without clipping in those horses with large amounts of feather.  [...]