Page 329 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

304 CHAPTER 1

VetBooks.ir Cross-sectional surface area of the tendon Havemeyer consensus for CSA at the maximum
injury zone (Thoroughbred forelimb)
Serves to evaluate tendon thickening (Fig. 1.582).
Many studies show a huge variation in size, with a
<2 cm ; moderate (grade 2) if CSA = 2–5 cm and
more than 2-fold variation in mean CSA depend- Lesion may be graded as mild (grade 1) if CSA
2
2
ing on anatomical zone, age, exercise level, breed severe (grade 3) if CSA >5 cm .
2
and size. In a study performed over 2 years on 142
National Hunt Thoroughbred racehorses, the mean Lesion CSA ratio
CSA at mid-metacarpus ranged from 77 to 139 mm The simplest technique consists in calculating the
2
at mid-metacarpus (level IIB). There is no significant ratio of the lesion CSA at the ‘maximum injury zone’
difference between Thoroughbreds, Warmbloods or (MIZ [i.e. its largest point]) to the total tendon CSA
Irish draught horses. Ponies and Quarter horses have at the same level (lesion CSA × 100/total tendon
a significantly smaller CSA at the same level. Major CSA) (Fig. 1.583). This is useful to evaluate lesion
influences exist depending on training regime, but size at a given point at a given time or to follow up its
it does not appear that monitoring CSA can predict evolution over time.
the risk of injury. It is useful to compare right and
left tendons, providing the injury is not bilateral. Havemeyer consensus for CSA ratio at MIZ
The left tendon is significantly larger than the right (Thoroughbred forelimb)
in horses that train anticlockwise. However, the Lesion may be graded as mild (grade 1) if ratio <10%;
difference between right and left limbs is slight in moderate (grade 2) if ratio = 10–40% and severe
most horses and it is generally accepted that a differ- (grade 3) if ratio >40%.
ence greater than 20% is significant of injury, while
greater than 10% provides suspicion for predisposi- BAPTEN Protocol severity score
tion to injury. A more sensitive method to assess severity accord-
ing to the Havemeyer symposium, based on the

1.582 1.583

Fig. 1.583 Lesion cross-sectional surface area ratio.
The ratio of the lesion CSA (1) at the ‘maximum injury
Fig. 1.582 Measurement of the whole SDFT zone’ is divided by the total tendon CSA (2) to obtain a
cross-sectional area may be performed using specific ratio (LCA × 100/TCA). In this case, 51% is indicative of a
software by tracing the contours of the tendon. severe lesion. The ratio may be measured at each standard
point in the metacarpus to obtain a severity score.