Australian Doctor Australian Doctor 7th September 2018 | Page 25

Therapy Update
25
A good look at back pain
Musculoskeletal
Dr Scott Masters
is director of the Caloundra Spinal and Sports Medicine Centre on the Sunshine Coast,
and a clinical lecturer in medicine at the University of Queensland, Brisbane.
It’s one of the most common complaints in adult
patients presenting to GPs. Here’s a guide to ordering
and interpreting spinal radiology for this condition.
P
ATIENTS presenting with low back
pain are often understandably
anxious. Many will request an MRI
in the belief that it will reveal the
cause of their pain. For some, this belief is
fuelled by coverage of their sports stars lin-
ing up for Monday morning MRIs, cement-
ing the idea that such scans must be vital
for accurate diagnosis and management.
In truth, MRI rarely provides a clear
diagnosis for the cause of back pain, but
does play a role in ruling out surgical and
red fl ag conditions.
The major downside of MRIs is that they
reveal numerous red herrings and inci-
dentalomas, which may divert attention
away from active management. 1 Instead,
patients may undergo needless further
investigation, referral and potentially
harmful invasive managements for inci-
dentally identifi ed, perceived ‘pathology’.
The results are extra cost, wasted time,
ongoing anxiety and inactivity for the
patient.
How can doctors sensibly order
and interpret spinal radiology?
First, we need to know which patients
need imaging. This requires an updated
approach to the traditional low back pain
‘red fl ags’, which have been fi ne-tuned.
Some symptoms traditionally considered
as red fl ags have been shown to be very
weak predictors of signifi cant pathology.
Night pain is an example. This may be pres-
ent in up to 45% of low back pain presenta-
tions and is rarely a harbinger of serious
disease. 2
In addition, up to 80% of low back pain
presentations include one traditional red
fl ag symptom. 2 Since only 1% of low back
pain patients have a serious cause for their
pain, most of these red fl ags will not be due
to signifi cant pathology. 2
Key red flags
The following should be considered as red
fl ags that point to signifi cant pathology in
low back pain:
A past history of cancer
The prevalence of previously undiagnosed
cancer as a presenting cause of low back
pain is 0.5% in primary care and 1.5% in
secondary and tertiary care. 3 If there is a
past history of cancer this increases to 7%
in primary care and 33% in the emergency
care setting. 3
It is worth being particularly mindful
of a history of cancers that preferentially
metastasise to bone (for example prostate,
breast and lung).
Older age, signifi cant trauma/injury, pro-
longed corticosteroid use
The prevalence of spinal fracture as a pre-
senting cause of low back pain is 0.5% in
increased the likelihood of spinal frac-
ture, which rose to 90% if any three of the
following features were present: female
gender, age over 70, severe trauma and pro-
longed corticosteroid use. 3
Severe neurological defi cits
New urinary retention or incontinence,
faecal incontinence, or saddle anaesthe-
sia warrant urgent ED referral to exclude
cauda equina syndrome. Consider the pos-
sibility of cervical myelopathy, particularly
if there is upper limb weakness and wide
ataxic gait. Cervical myelopathy is one
of the most common causes of acquired
spastic paraparesis in adults and is easily
missed. 4
First we need to know which patients need
imaging. This requires an updated approach
to the traditional low back pain ‘red flags’.
primary care, and 5% in secondary and
tertiary care. 3 In any of these settings, age
over 65 or a history of signifi cant trauma
increased the likelihood of spinal fracture
causing low back pain to 15%. 3
In low back pain presentations asso-
ciated with prolonged corticosteroid use,
the likelihood of spinal fracture rose to
33%. 3
Combinations of these red fl ags further
Features of spinal infection
Fever, urinary or cutaneous infection, his-
tory of IV drug use, spinal procedures and
immunosuppression indicate the need to
consider and exclude spinal infection.
Evidence of a visceral cause
Always consider the possibility of abdom-
inal aortic aneurysm, gynaecological,
renal/urinary tract and other visceral