156 Canine Sports Medicine and Rehabilitation
with the intent of heating and evaporating to
cut the tissue and to control bleeding and pain
by cauterizing the blood vessels and nerves
along the incision line. Class 4 therapeutic
lasers can be classified into heating and non
heating lasers. Use of nonheating lasers is
known as low‐level laser therapy (LLLT). LLLT
influences cellular processes through photobio
modulation (Figure 7.17). Heating lasers are
therapeutic lasers that create heat in the tissue
quickly if not moved constantly during a ther
apy session.
Evidence supporting the use of LLLT
Therapeutic effects on pain
Light energy is absorbed by chromophores
(light‐absorbing molecules found in the cell)
causing a number of biological effects including
oxygen production, changes in cell calcium ion
balance, ATP production, changes in cell mem
brane permeability (Passarella et al., 1984; Karu,
1988; Nasu et al., 1989), and reduction in inflam
mation by reducing production of cytokines—
cyclooxygenase 2 (COX2), tumor necrosis factor
α (TNFα), interleukin 1 (IL‐1), and IL‐6 (Sakurai
et al., 2000; Alves et al., 2013b). LLLT may
also facilitate collagen synthesis (Abergel et al.,
1984), growth factor release (Yu et al., 1994), and
stimulation of fibroblast development (Pourreau‐
Schneider et al., 1990), all promoting tissue repair.
LLLT may increase angiogenesis and therefore
the formation of new capillaries in injured tis
sues (Corazza et al., 2007). Indeed, evidence has
been found that LLLT can lead to more rapid
closure (Hopkins et al., 2004), increased tensile
strength (Vasilenko et al., 2010), and greater col
lagen content during wound healing (Medrado
et al., 2003). LLLT has also shown an ability to
affect the healing of nerves (Gigo‐Benato et al.,
2004), connective tissues, such as ligament
(Fung et al., 2002), and may have positive effects
on injured cartilage (Guzzardella et al., 2001;
Guzzardella et al., 2002).
Additionally, LLLT may assist in pain reduc
tion through increased metabolism of endoge
nous opiates, or a change in the conduction
latencies of nerves (Snyder‐Mackler & Bork,
1988; Lowe et al., 1994).
There are numerous studies supporting the
use of LLLT to address both acute and chronic
pain related to orthopedic and neurological
diagnoses. For example, a 2016 study by Ojea
and colleagues found that human patients
who received postoperative LLLT experienced
less incisional pain as compared to a sham
group (Ojea et al., 2016); this is likely meaning
ful for postoperative canine patients as well.
LLLT has also been shown to reduce the pain
associated with chronic orthopedic conditions
such as ankylosing spondylitis (Stasinopoulos
et al., 2016), temporomandibular joint (TMJ)
pain (Cavalcanti et al., 2016), and knee osteoar
thritis (Assis et al., 2015; Bjordal, et al., 2003).
Indeed, in a study by Ip (2015), patients with
knee osteoarthritis who received LLLT in addi
tion to conventional physical therapy were
significantly less likely to require joint replace
ment surgery as compared to patients who
received physical therapy alone. This outcome
remained true even 6 years after treatment
was completed (Ip, 2015).
LLLT can be effective in decreasing neuro
pathic pain (de Oliveira Martins et al., 2013;
Janzadeh et al., 2016). Kobiela Ketz and col
leagues used a peripheral nerve injury model in
rats with resulting pain as assessed by mechan
ical hypersensitivity. Subjects treated with
LLLT every other day (initiated 7 days after
injury) showed improvements in pain status
after just two treatments, and were returned to
baseline mechanical hypersensitivity levels
within 10 treatments (Kobiela Ketz et al., 2017).
A 2016 literature review also supported the
positive effect of LLLT in the treatment of neu
ropathic pain (de Andrade et al., 2016).Figure 7.17 Example of a low‐level laser therapy (LLLT)
unit. Source: Courtesy of Respond Systems. Reproduced
with permission of Respond Systems.