Chapter 16 Biological Therapies in Canine Sports Medicine 409used clinically. This is one reason that the final
volume of PRP produced is possibly clinically
relevant.
The findings of these studies assessing multi‑
ple canine PRPs underscore that the term PRP
is not specific. Rather, PRPs make up a diverse
array of biological blood‐derived products with
varying characteristics with regard to cellular
composition and growth factor delivery. It is
important that the specific characteristics of a
PRP are considered, and in the context of a
specific medical condition, when evaluating
the efficacy data for a particular PRP and its
potential clinical benefit.
Efficacy data
Tendon injury: surgical application
A series of three experiments using platelet‐rich
fibrin constructs were performed to assess the
suitability of PRP for treating tendon defects in
dogs. The first of the studies confirmed that
substantial TGF‐β1 was eluted from the acti‑
vated PRP fibrin membrane that was created by
activation of PRP with calcium chloride coupled
with a simultaneous and additional centrifu‑
gation (Visser et al., 2010a). In the second experi‑
ment, it was demonstrated that canine tenocytes
demonstrated greater proliferation in vitro when
supplemented with the growth factor‐rich
eluent from this PRP fibrin membrane (Visser
et al., 2010b). In the third study, the central third
of the patellar tendon was excised from both
stifles in eight dogs and the PRP fibrin mem‑
brane was sutured into the defect of one tendon
(Visser et al., 2011). Dogs were sacrificed at 4
(n = 4) and 8 weeks (n = 4). The rate and quality
of tissue healing was not improved with use of
the PRP fibrin membrane. However, the total
volume of fibrous repair tissue was significantly
greater in the group treated with the PRP mem‑
brane. The authors of this study concluded that
use of the platelet‐rich fibrin membrane may
not be indicated for augmenting the repair of
tendons that have been injured acutely and are
healthy in all other aspects. However, since the
PRP fibrin membrane increased the volume of
healing tissue, a PRP fibrin membrane could be
beneficial if an increased volume of tissue is
considered desirable.
Tendinopathy: percutaneous injection
Percutaneous injection to treat tendon injuries is
highly pertinent to canine sports medicine given
the frequency of supraspinatus, common calca‑
neal, and iliopsoas tendon injuries in competi‑
tive dogs. However, the only data regarding
PRP for such applications are from one case
series evaluating the benefits of a single ultra‑
sound‐guided injection of a leukocyte‐rich PRP
in 10 dogs with supraspinatus tendinopathy
(Ho et al., 2015). Subjective client‐assessed
lameness improved in 40% of dogs. However,
the caregiver placebo effect has previously been
documented to be approximately (or slightly
greater than) 40% in veterinary medicine
(Conzemius & Evans, 2012). Tendon heteroge‑
neity and echogenicity based upon ultrasonog‑
raphy were improved in six of the 10 dogs. Force
plate assessments at 6 weeks post injection did
not demonstrate any improvement in treated
dogs (Ho et al., 2015). Accordingly, there are
insufficient data to demonstrate that percutane‑
ous PRP injections are effective in treating tendi‑
nous injury in dogs, and further study is needed
to ascertain whether PRP is useful for such
conditions.Bone healing
A recent review and meta‐analysis of all
preclinical animal studies concluded that the
evidence suggests that PRP confers several
beneficial effects on animal long bone models
(Gianakos et al., 2015). However, these conclu‑
sions were based largely on data from species
other than dogs. The author (SF) is aware of
only three studies assessing the effects of PRP
on long bone healing in dogs. One study com‑
pared the benefit of an uncharacterized, calcium‐
activated PRP in conjunction with calcium
phosphate granules (as a bone filler) in an ulnar
defect model in dogs (Rabillard et al., 2009).
Although control dogs treated with autogenous
cancellous bone graft healed uneventfully, dogs
treated with the granules, with or without
adjunctive PRP, did not have successful bone
healing. Conversely, another study assessed use
of a PRP (moderate platelet concentration and
calcium activation) in a heterogeneous popula‑
tion of dogs in whom a mid‐diaphyseal defect
in the radius had been created and stabilized