Page 337 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

312 CHAPTER 1

VetBooks.ir of injected cells in the clinical situation remains surfaces, proper farriery and identification of early
degenerative changes in the tendon. It has been
unclear. Autologous pluripotential stem cells may
be isolated from bone marrow or adipose tissue
may help to increase tendon resistance to strains.
aspirates and grown in vitro before being reinjected suggested that early training before 2.5 years of age
into the lesion. This ensures adequate cell concen- Training techniques, regime and surfaces have
trations but causes significant delays between blood a tremendous effect on the risk of injury or rein-
collection and intralesional injection (several weeks) jury, with marked variations noted between train-
and it may be argued that injecting MSCs into ing yards in several studies. However, it is unclear
an already partially healed lesion is less effective. which factors are deleterious or beneficial at this
Alternatively, MSCs may be isolated and reinjected stage. Ultrasound has proved disappointing in pre-
directly without previous ex-vivo culture. A rela- dicting injury but is useful to monitor adaptation
tively small number of cells are obtained using this to exercise level and to predict reinjury, especially
technique. Nevertheless, experimental treatment when monitoring variations of total CSA. MRI may
using both techniques provides similar results, with prove more useful as it helps detect alterations in
major improvement in healing tissue quality in the matrix water contents.
early stages, particularly when combining MSC and
PRP injection. Unfortunately, there is still a lack Prognosis
of adequate large scale or long-term studies. Gene The prognosis for soundness is always good, even
therapy is receiving increasing interest but is still at with severe tears. Tendons always heal. The prog-
an experimental stage. nosis for return to the same level of activity and
performance is, however, guarded, depending on
Surgical treatments the severity of the lesion. Up to 50% of affected
These have been used for decades and include chemi- racehorses never return to racing, while recurrence
cal or physical cautery (‘firing’), proximal check liga- occurs in up to 80% of cases. In other athletic activi-
ment (accessory ligament of the SDFT [AL-SDFT]) ties the prognosis is probably better, but the risk of
desmotomy and percutaneous longitudinal tenot- recurrence remains high. Recent studies suggest that
omy (‘splitting’). Cautery and blistering have not the prognosis for return to athletic activity does not
been shown to produce any advantages and may be depend on the severity of the initial injury, but rather
deleterious as they promote adhesions and paratenon on the evolution of the ultrasonographic appearance
fibrosis. These methods also raise concerns regard- regardless of the initial severity.
ing the animal’s welfare. The other two techniques The prognosis associated with SDFT tears within
are carried out in the subacute phase and have been the confines of the digital or carpal tendon sheaths
suggested to increase the speed of recovery, although is much poorer than in the metacarpal region.
the repair quality and rate of recurrence may not be Spontaneous rupture in the carpal sheath may be
improved. These should therefore be used in severe associated with vascular supply impairment, as
or recurrent cases or in cases where speed of recov- thrombosis of the median and collateral arteries is
ery is paramount. There has been some concern that frequently observed. In the digital sheath, central
accessory ligament desmotomy may predispose to lesions without associated tenosynovitis carry a bet-
contralateral SDFT tendonitis or to SL injury in ter prognosis than peripheral or full-thickness tears.
either limb. There is currently no strong evidence The latter often heal with fibrocartilage metaplasia
that surgical treatments significantly improve the and restrictive adhesion formation, the recurrence
long-term outcome. rate is very high and few horses appear to return
to work. SDFT branch injuries carry a fair to good
Prevention prognosis, provided the lesion does not extend to the
Prevention in the future may be through improved undivided part of the tendon. Avulsions carry a very
training techniques, adequate care of training poor prognosis.