Other diagnostic tests
Ergometry
What it is:
It consists of registering the force expended by the muscles during
exertion. Back muscles are used to maintain posture and move the spinal
column, but are also used when muscles from other parts of the body
are working. For example, when raising an arm, back muscles contract
to keep stability, compensating for the variation in the center of
gravity that the arm movement creates. When pain is present, there
are changes in the characteristics with which back muscles expend
force. Also, if exertion triggers pain, the amount of force is limited
in a very characteristic fashion. Ergometry allows registering these
characteristics.
What it allows:
Basically, to register the alteration of the force associated
with back pain.
Risks:
No risks, other than the fact that the registered efforts may,
and in fact do trigger pain, at least temporarily.
Indications:
The existing recommendations,
based on scientific evidence, do not advise ergometry for assessing
acute patients (of less than a 3 month evolution).
Ergometry does not inform of the cause of pain but may be recommended
in a medical-legal context, to evaluate work capability limitations.
Echography (or sonogram)
What it is:
It is a system similar to the submarine sonar. It emits waves
that rebound against certain structures and cross other structures,
in a different fashion depending on their consistency. Thus, the
analysis of the collected waves reflects composition, shape, and/or
thickness of subjacent tissues.
What it allows:
Echography allows visualizing the thickness of some muscular groups.
In some patients, back pain impedes some movements and provokes
atrophy of a muscular group. This lack of muscle may increase the
onset of future pain episodes.
For example, some scientific studies have shown that the paravertebral
musculature is symmetrical: the left and right muscles tend
to be similar, independently of whether the individual is left-
or right-handed. In patients who have undergone back surgery, or
those who have suffered chronic back pain, paravertebral muscles
may show an 80% atrophy compared with the healthy side, which leads
to asymmetrical load distribution, muscular or disc overload and
onset of new pain episodes. In these cases, echography permits assessing
how one side of the musculature is atrophied in relation to the
other.
Risks:
There are no proven risks.
Indications:
The existing recommendations
based on scientific evidence do not advise it to evaluate patients
with pain of less than a 3-month evolution.
Some physical therapists use real-time echography, which enables
them to evaluate the image constantly and show it to patients on
a monitor. This procedure shows patients the echographic image of
the muscle that needs to be worked on while patients contract it
in front of the camera, which permits them to check that they are
contracting the muscle they specifically need to strengthen with
each movement. It is therefore used more as a helping tool in physical
therapy than as a useful diagnostic procedure for back pain.
Thermography
What it is:
It consists of measuring body temperature. Formerly, this technology
could not measure very light variations, and thermography results
were very questionable. Nowadays, technological advances and computer
programs permit very detailed and subtle measurements: some devices
detect variations of one hundredth of a degree on surfaces of 1
square millimeter.
In the presence of back pain and neurogenic
inflammation, blood vessel dilatation increases body temperature
in that specific area. Thermography is able to detect these variations.
What it allows:
To prove the presence of temperature changes in the painful site,
which suggests the presence of pain but gives no information on
its cause.
Risks:
Thermography is not painful and does not expose patients to any
risks.
Indications:
The existing recommendations
based on scientific evidence do not advise it to evaluate patients
with pain of less than a 3 month evolution. It is exclusively used
for medical-legal purposes when presence of pain must be proven
in an objective way.
MEASUREMENT OF THE DEGREE OF ACTIVITY OF CAPSAICIN SENSITIVE FIBERS
What it is:
It consists of the application of a substance -"capsaicin"- that
induces pain
nerves to release the substances they contain.
The underlying rationale is that these nerves are persistently
activated in patients with common
back pain, therefore the implicated substances in conducting
pain are constantly released -especially Substance
P-. The amount of this substance is greater in the activated
nerves than in the non-activated ones. Capsaicin provokes release
of the Substance P contained within the pain nerve ending. Therefore
the released amount reflects the grade of activity.
Since Substance P produces neurogenic
inflammation at the site where it is released, a way to quantify
the released amount -and, indirectly, the grade of activity of the
releasing nerve- is to measure the intensity of inflammation by
applying capsaicin, and evaluating vessel dilatation and extension
of inflammation.
What it allows:
It permits showing pain nerve activation, which has been proven
to correlate with the presence of back pain.
Risks:
It produces temporary skin flushing in the area where capsaicin
is applied, and is sometimes associated with itching and heat sensation.
Indications:
The existing recommendations
based on scientific evidence do not advise it for diagnosing patients
with back pain.
The method for measuring vessel dilatation is very complex and
requires sophisticated devices. Moreover, it objectively evidences
presence of common back pain, but does not contribute to identifying
its cause, nor does it add any relevant data for deciding the most
adequate treatment. Therefore, it is only used experimentally or
in very specific research studies, since this technique has proven
to strongly correlate with the existence of common back pain and
not with pain in the back due to other reasons.
|
Back Pain Research Network 
Webmaster
Diagnostic tests
