The number and range of investigations available to primary and secondary care is enormous.
There is a feeling that it is almost too easy these days to send a patient off for a scan, without fully assessing the patient and making a differential diagnosis purely from the history and examination. I think we are all guilty of this.
However investigations are vital in confirming, or not, our provisional diagnosis, assessing in detail the pathology, and aiding the planned treatment.
I will list below the most common investigations in my Orthopaedic practise, how they work and when to use.
Almost all Orthopaedic patients with a bone, joint or soft tissue problem should have a base-line X-ray. Two Orthogonal (at 90 degrees) views should be taken in most cases.
Specific anatomical examples in my practise include:-
2. Ultrasound Scans
An ultrasound probe emits high frequency sound waves that are passed through the body area being studied. These waves are reflected back by the structures inside and the echoes are used to form an image. The harder the structure they hit, the stronger the echo.
Thus fluid gives no image, while bone gives a very strong image.
Doppler ultrasound is similar, but also gives an idea of blood flow in the area.
Examples of conditions where ultrasound is useful include:-
3. Computer Tomography
A CT uses X-rays to form an image. Instead of a single X-ray, as used in a normal radiograph, CT uses multiple X-ray beams at different angles. The beams pass through the body area and are picked up on the other side. The signal is then turned into an image by the computer. These images can be manipulated into 3-D images.
CT in Orthopaedics is best for looking at bony anatomy.
Examples of conditions where CT is useful include:-
4. Magnetic Resonance Imaging (MRI)
Radiowaves are sent through the body. These excite the protons in the cells and push them into a different position. As these protons move back into their normal position, they give off their own radiowaves. These are picked up by the scanner and turned into an image.
There are many different sequences that can be used in MRI. The two most common are:-
T1 = This image shows fat as a bright image and fluid as a dark image. As a rule of thumb this image is useful in seeing anatomy.
T2 = This image shows up water (or any fluid) as very bright. It is therefore useful in looking at inflammation, cysts etc. As a rule of thumb this image is useful in seeing pathology.
N.B an aide-memoire is Water = H20, thus T2 (easy!)
Examples of conditions where MRI is useful include
5. Nerve conduction studies (NCS)
This is the study of peripheral nerves and the muscles they supply.
NCS look at the two functions of peripheral nerves, sensation and muscle stimulation.
The motor component is performed by electrical stimulation of a peripheral nerve and reading the effect in the muscle further down the limb supplied by that nerve. The time taken to travel that distance is measured, as well as the reaction of the muscle.
The sensory component is similarly performed, but the measurement is taken at a purely sensory spot (e.g the tip of the finger).
This will therefore show if there is a block or a slowing to the impulses travelling down that nerve at a specific spot e.g the carpal tunnel.
6. Blood tests
A number of blood tests are useful in certain orthopaedic conditions
A). Infection = FBC, ESR, CRP
B). Inflammatory Arthritis = FBC, ESR, Rheumatoid factor, ANA (anti-nuclear antibodies)