Page 624 - Adams and Stashak's Lameness in Horses, 7th Edition

590 Chapter 4

athletic activity to allow for the majority of healing to greater adaptive ability and may respond to an appro-
occur, and clinical signs of lameness should be absent priate exercise regimen to produce a more functionally
VetBooks.ir cise. Tendon rehabilitation protocols are tailored accord- allowed free pasture exercise develop a larger, stronger,
adapted tendon. Recent studies suggest that foals
after a short period of rest and before any forced exer-
49
more elastic tendon compared with those that were con-
ing to whether the structural damage is graded as mild,
moderate, or severe. In mild structural injury, the SDF fined or subjected to a training program. Effects on the
has a tendon CSA that is less than 20% greater than noncollagenous matrix appear to be responsible for
normal SDFT, a core lesion of 15% or less of the total these differences. In contrast, training or excess exercise
tendon CSA, or a longitudinal lesion of 20% or less of may have permanent detrimental effects on the biome-
the total length of the tendon. A moderate structural chanical and functional properties of the SDFT in the
injury has a 20%–35% greater CSA, a core lesion of foal. The implication is that the determination of opti-
15%–30% of the total tendon CSA, or a longitudinal mum exercise intensity and timing and the role of the
lesion of 20–35% of the length of the tendon. A severe noncollagenous matrix in tendon physiology in the
structural injury has a 35% greater CSA than normal, a young horse may hold the key to developing tendons
core lesion greater than 30% of the total tendon CSA, that are more capable of resisting injury. Optimal condi-
and a longitudinal lesion greater than 35% of the length tioning of a young horse may result in improved perfor-
of the tendon. mance and reduced tendon injury later in life. 33,125
All cases with structural injury to the tendon or sus-
picion of a structural injury should have an initial period
of stall confinement and hand walking after acute DEEP DIGITAL FLEXOR TENDINITIS
inflammation subsides, usually a minimum of 30 days.
Hand walking is generally 15 minutes twice daily from Strain injuries of the DDFT in the metacarpal or met-
0 to 30 days. Many mild tendinitis cases can begin rid- atarsal region are uncommon compared with injuries of
ing at the walk at 30 days, but most moderate and severe the SDFT, ALDDFT, or SL on the basis of both postmor-
139
48,109
injuries require at least 60 days of hand walking. tem surveys and ultrasonographic examinations.
A second ultrasonographic examination is made at 30 However, many DDFT lesions are within the hoof and
and 90 days, and the tendon lesion compared to original cannot be seen with ultrasound.
scans. Repeat PRP or stem cell injections can be per-
formed under ultrasonographic guidance every 30 days Etiology
for three to four treatments. Horses without lameness
and good grades of lesion can increase the rehabilitation Classic deep digital flexor (DDF) tendinitis in the
exercise to include riding at a walk 30 minutes daily from distal metacarpal/tarsal area is usually traumatic in ori-
90 to 120 days, increasing over the next several months. gin, but direct blunt trauma may be a more common
After several months of walking, and in horses without cause than with SDF tendinitis. Excessive strain (defor-
lameness and improvement in ultrasound grade, horses mation) of the tendon, usually as it passes over the fet-
can begin trotting under control. One method is to have lock, can induce inflammation or structural damage.
horses trot under saddle only on the straight portions of The anatomic confluence of the digital sheath and
the ring to avoid asymmetric loading on the limbs. The annular ligament relatively immobilizes the DDFT at
number of laps and times per day can be increased, this site, possibly predisposing this area to injury.
gauged by the progress of the horse and tendon healing Horses that hit themselves around the fetlock region
on ultrasound. Cantering can be added for 5 minutes with other limbs during exercise can induce a DDF
every 2 weeks for 120 days for good and fair cases, tendinitis. DDF tendinitis can be confused with SDF
whereas poor cases have a reevaluation and discussion of tendinitis and desmitis of the ALDDFT based on visual
further treatment options. No active race or jump train- appearance (Figure 4.170). 139
ing should begin for at least 6 months from the injury. Many, if not most, DDFT abnormalities are degener-
Arguably, a controlled exercise program may be prefer- ative in nature and are located in the distal phalangeal
able to turnout after 60 days. This statement is supported region of the forelimb. Distal injuries of the DDFT pal-
by the results of a retrospective study of 50 Thoroughbred mar/plantar to the flexor cortex of the navicular bone
racehorses with SDF tendinitis. The severity of the lesion are a well‐recognized postmortem and MRI finding and
50
and type of rehabilitation were significant. Of 16 horses are considered part of the heel pain syndrome. 81,104
kept in pasture, 2 of 8 raced. Of 28 horses kept in a con-
trolled exercise regimen, 20 of 28 raced. Successful cases Clinical Signs
usually require 8–9 months of rest and rehabilitation to
return to their previous full workload. Shortening this DDF tendinitis is suspected with careful physical and
period or advancing too quickly often results in worsening lameness examination. It can be confused with distal
of the tendon lesions. The premise for use of controlled SDF tendinitis (low bow) or desmitis of the ALDDFT on
exercise is to initially reduce inflammation, maintain glid- visual examination and palpation, especially if edema or
ing function, and improve healing. hemorrhage blends the structures (Figure 4.170). Limbs
should be palpated both with load on and off the limb.
In unloaded limbs, the SDFT can be moved off of the
Prevention DDFT, permitting better palpation. If injury of the DDFT
Based on changes seen in tendon matrix associated has occurred within the digital sheath, sheath distension
with development, aging, function, and exercise, it has can also make palpation of the structures more difficult.
been hypothesized that immature tendon may have a In both SDF low bow and DDF tendinitis, a convex