The use of ultrasound technology is an essential diagnostic tool for the equine veterinarian. The most common use of ultrasound at Weatherford Equine is for the detailed examination of the reproductive tracts of mares during the breeding season. The technique involves the careful placement of the probe in the rectum of the mare which gives us a birds eye view of the uterus, ovaries and cervix.
Lower Limb Ultrasound
The other most common usage for ultrasound is the examination of the tendons and ligaments of the horses lower limb. We can also use ultrasound to examine chests, abdomens, muscles and other soft tissues of the body. There are very few limitations to the use of ultrasound, it can only visualise the surface of bone and is not suitable for deeper bone structures. In order to see Fractures or Bone Disease we require Digital Radiography.
Tendon and ligament injuries in the limbs of competitive horses are, unfortunately, very common. It is true that many owners and trainers of performance horses have regarded injuries to these structures as more threatening to an equine athlete’s future career than fractures.
Usually horses with suspected tendon injuries are presented when an owner recognises swelling over the structures and the presence of mild lameness. The swelling is usually not present at the time of injury, but is more commonly noticed the following day. At this point, there are several questions that need to be answered:
- Is the inflammation within the tendon or ligament or is it in surrounding tissue?
- If it is in tendon/ligament – how severe is the damage?
If swelling is surrounding the tendon the prognosis is very good, and the horse only needs a very short period of rest before return to performance. If the damage is to tendon or ligament fibres themselves, then the prognosis and treatment change depending on the severity.
Assessment of tendon damage is best performed by a veterinarian experienced in the use of a quality ultrasound machine. For basic assessment of obvious lesions, examination with a portable machine on farm may be all that is required. For the detection of more subtle lesions and better assessment of the tendon fibres can be achieved at a dedicated surgical facility with an appropriate high end machine.
The factors indicating severity of a lesion are:
- Cross sectional size of the tendon or ligament - Usually compared to either an ‘established normal’ size, or comparison against the opposite limb. It is important to remember that the opposite limb may also have been affected at some time, and therefore it may not represent a normal size for the use as a comparison. If the cross section size is increased by 20-30% it is rated as ‘moderate’ damage (obviously if it is <20% it is ‘mild’ and >30% it is ‘severe’.)
- Size of core lesion - seen as a black/ hole on ultrasound in the tendon. In this case, ‘moderate’ applies to core lesions of 15-30% of the tendon cross sectional area or if it extends 20 -30% of the length of the tendon.
- Chronicity (ie. Is this a re injury of a previous lesion?) - If the tendon has been torn several times the prognosis for ongoing soundness is obviously reduced. Assessment of deposition of previous scar tissue is readily established with good ultrasonographic technique and will change the case management.
Some of the more common structures involved are the Superficial digital flexor tendon (SDFT), the Deep digital flexor tendon (DDFT), the Suspensory ligament origin (behind the knee and hock) and the Suspensory branches. Some of these structures more commonly form low grade ongoing tendonitis, while others tend to suffer acute severe tears.
Treatment options for these injuries are many and varied. The most important factor on healing is a graded exercise program, which prevents further damage and the slow introduction of exercise allows for realignment of healing tendon fibres.