GUIDELINES For Successful DSLD Exam & Ultrasound
Exam Form
A physical exam, lameness exam, and ultrasonographic exam of their suspensory tissues. Physical data:
presence of fetlock enlargement and/or effusions of the fetlock joints or tendon sheath; angle of the fetlock during weight-bearing as being either upright, level, or hyperextended; palpable pain and enlargement or thickening of the suspensory ligament as being either none, mild, moderate, or severe; baseline lameness using the AAEP Lameness Grading System of 0-57;and fetlock flexion tests using the same grading system.
Ultrasonographically, the suspensory ligament of each limb examined just proximal to the bifurcation or in zones 2A or 3A, and both branches roughly midway along their length or in zones 3A or 4A. Measurements recorded as follows: the suspensory body in cm in the palmar/plantar to dorsal plane and both branches in area in cm2
and in cm in the lateral to medial plane, or medial to lateral plane—totaling 3 measurements per leg. Area measurements of the suspensory ligament branches are highly encouraged and represent the most accurate results. In Peruvian Pasos the suspensory body should not exceed 1.3 cm at midcannon and suspensory branches in zones 3A or 4A should not exceed 0.7cm squared or 1.1 cm in a two dimensional plane. Other equines can range slightly higher on the suspensory ligament body measurement and can have branches that range up to 1cm squared or 1.1 cm in a two dimensional plane and be considered normal.
Sonographic lesions recorded as either hypoechoic or hyperechogenic areas in the suspensory ligament, and it was noted whether there were other soft tissue lesions usually involving the flexor tendons.
DSLD represents a disease that is a chronic, progressive multi-limb syndrome that affects either sex, does not have an age predilection, and is usually nontreatable. Consistent exam findings are:
Pain on isolated palpation of the suspensory ligament and palpable enlargements and thickenings of the ligament in at least 2 limbs;
Lameness in at least one limb and often multiple limbs;
Positive fetlock flexion tests usually in 3 or more limbs, with at least one limb having a flexion grade of 2.5 or higher; and
Enlarged suspensory ligament body and branch measurements on ultrasound exams, again in more than one limb.
Horse may be presented with complaints of upper limb and/or back pain, surly and miserable temperaments, reluctance and/or a refusal to work, unwillingness to stand for the farrier, and subtle gait changes that are not at first overt lameness.
4 steps are useful and reasonably accurate in either the diagnosis of, or screening for DSLD in horses.
The three physical exam procedures for each limb of palpation for pain and/or enlargement and thickening of the suspensory ligament, observance of a baseline lameness, and abnormal fetlock flexion tests all taken together provide useful information in the screening for DSLD, particularly when large numbers of animals are examined.
Given that (1) no unaffected horses exhibit either specific pain or palpable changes to the suspensory ligament, (2) few nonaffected horses are lame, and (3) only 33% of nonaffected horses have a fetlock flex worse than 2.5, a horse that (1) does not reveal any pain or palpation changes to the suspensory, (2) does not exhibit any lameness, and (3) does not flex lame in the fetlocks or has grades of flexion lameness of 2.5 or less would be highly unlikely to be affected with DSLD.
The fourth step of measuring the suspensory ligament at 3 sites per leg improves a clinician's confidence in the diagnosis, the selection of sites of the suspensory body at midcannon and both branches only.
Combining the information from all 4 steps should decrease the likelihood of making false negative determinations. In other words, an animal that 1.Palpates with pain, 2.is lame, and 3. flexes lame with high grades, especially in several fetlocks 4.(combined with ultrasound measurements near to or at the cutoff points) suggests the presence of disease.
At the very least, if the ultrasound measurements are within normal limits, but the horse physically has positive signs, a repeat exam in several months' time would be a prudent suggestion.
In contrast, a horse with no positive physical exam signs for DSLD but ultrasound measurements that are at or close to the cut-offs should not be diagnosed with DSLD based on the ultrasound measurements alone.
Earlier detection and screening for DSLD allows owners and breeders to make informed decisions prior to sales and purchases, potential breeding, and future plans for young stock. While a physical and ultrasound exam is not a guarantee for future soundness, until a reliable gene marker test becomes available, it is the best defense available at this time in combating DSLD.
Revised March, 12, 2006 Excerpts from Dr Mero's May 2005 article.
