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Musculoskeletal system: 1.7b The axial skeleton – thoracolumbar region 255

VetBooks.ir BACK PAIN ‘untreatable behavioural’ back problems from those
horses with finite pathology can be misleading.
Definition/overview
Back pain is a challenging diagnostic and therapeu- Clinical presentation
tic syndrome. Where physical abnormalities can be Clinical assessment of a back pain case should include
identified, they seldom have a consistent correlation the following steps: history; passive physical exami-
with clinical signs of back pain, which are subjective nation, including assessment and palpation of the
and variable in time. Objectively investigating a sub- whole musculoskeletal system; and dynamic physical
jective syndrome for which there are many causes examination, including walk, trot and canter. Further
and relatively few treatments is difficult and poten- tests and investigations often follow, such as a neuro-
tially controversial. Most of the conditions described logical examination, an oral examination and a lame-
in this chapter can cause primary back pain, but ness work-up preferably including a ridden test. The
their frequent inaccessibility does not lend itself to first and more challenging aim is to identify whether
proving cause and effect by traditional diagnostic pain is present in the back and/or elsewhere in the
analgesia. In addition, secondary back pain occurs musculoskeletal system. Then, the second aim is to
more commonly than primary back pain, most often decide on the most appropriate means of identifying
through compensation for insidious limb lameness, the problem, which is often somewhat easier.
commonly, but not limited to, the hindlimbs Back pain has many manifestations, with symp-
toms varying from mild loss of performance through
Aetiology/pathophysiology to extreme and dangerous avoidance behaviour, with
In an acute trauma, a pain stimulus is transmitted bucking, rearing and bolting. With time and experi-
to the central nervous system (CNS) via nocicep- ence these symptoms can be recognised easily, but
tive sensory nerves distributed in the soft tissues of owners and riders may not associate them with prob-
the back. The response is not linear due to negative lems until symptoms worsen, instead finding various
feedback loops within the lower levels of the CNS, alternative explanations, including self-blame. Most
leading to variation in higher pain perception. The horses with finite orthopaedic causes of back pain
expectation of pain is known to increase its percep- exhibit behavioural and schooling abnormalities,
tion and the ‘cold backed’ horse that anticipates pain yet horses owned and ridden by inexperienced riders
when saddled or backed illustrates this phenomenon. may also exhibit these abnormalities in the absence
Chronic stimulation and nerve damage (neuropa- of pathology. More experienced riders and profes-
thy) can lead to nervous system dysfunction, giving sionals may be able to help differentiate the issue,
the inappropriate sensation of pain (termed neural- but a useful starting position is to assume that all
gia) and abnormally heightened sensation (termed behavioural problems are indicative of finite clinical
allodynia). These phenomena are often observed pathology, at least until proven otherwise.
in equine back pain, whereby the lightest brush of Loss of performance, evidence of distress or avoid-
fingers over the back elicits an electric shock-type ance behaviour before or during work may be the first
pain response. Secondary overuse of thoracolumbar sign. Failure to engage the core muscles of the back
epaxial muscles can develop as a response to lame- leads to frustrated owners complaining that they can-
ness, so-called compensatory or secondary back not get their horses to develop muscles of the topline,
pain. The muscles become tight and painful to pal- will not work in an outline or work excessively on
pate due to increased workload, despite the cause the forehand. Symptoms can develop insidiously or
being located at a distant site. The anti-inflammatory the horse may be able to continue working for con-
mode of action of NSAIDs as painkillers means that siderable periods of time with intermittent rest or
they have little or no effect on primary back pain repeated musculoskeletal manipulative treatments.
caused by lactic acid build-up in tense muscles or on Owners often find actual pain in the back relatively
neuropathic pain (e.g. clinical signs of allodynia or late in the process, reporting the findings of physical
neuralgia). Hence relying on NSAIDs to distinguish therapists, or struggling to approach or groom the