What is a Shoulder MRI arthrogram?

What is a shoulder arthrogram, and do I need one?

A shoulder arthrogram is an MRI examination done after injecting a special dye (contrast) into the shoulder joint. This is usually done under imaging guidance. Then, you will have a shoulder MRI scan. This is a special tunnel-like machine which has a strong magnet. It uses magnetic fields and radio waves to produce detailed shoulder images.

What is the difference between normal shoulder MRI and shoulder MRI arthrogram?

Both of the examinations are MRI-type scans. The difference is that in a normal shoulder MRI, only an MRI scan is done, while in a shoulder MRI arthrogram, a special dye (contrast material) is injected into the shoulder joint first under imaging guidance, and then a shoulder MRI scan is done. The images produced in the latter case are more detailed.

Why do I need a shoulder MRI arthrogram examination?

To answer this, we need to know a bit about shoulder anatomy. The main shoulder joint (also referred to as the glenohumeral joint) is a ball and socket-type joint. The ball is formed by the humeral head (the arm bone), and the socket is formed by the glenoid (part of the shoulder blade that articulates with the humerus).

The shoulder has a thin layer surrounding it called the joint capsule. The labrum is also an important structure inside the shoulder joint. It is a pear-shaped ring of cartilage that sit along the margin of the socket (glenoid) to increase its depth. This provides significant stability to the shoulder joint and, at the same time, maintains its good range of movement.

A rotator cuff is a special group of tendons that run on top of the ball of the shoulder joint. These tendons are very essential for shoulder movements and stability.

A shoulder MRI arthrogram is usually indicated to:

· Assess for any injury to the small cartilage or labrum inside the shoulder joint. This usually happens secondary to a significant shoulder injury or shoulder dislocation. These structures are very important for shoulder stability, but they are small and crowded inside the joint. When a dye is injected, it will distend the joint and provide excellent images of the labrum and other small structures inside the shoulder joint, making assessment more accurate.

· Assess for a special injury to the upper part of the labrum (called a SLAP tear).

· Detailed assessment of the articular cartilage, which is the thin layer covering the surface of the bones to ensure smooth movement at the joint and shoulder ligaments.

Same patient, after performing injecting contrast and performing a shoulder arthrogram examination

If there is clinical suspicion of injury to the structures outside the main shoulder (glenohumeral joint), i.e. to assess for any rotator cuff tear, shoulder bursitis, calcific tendonitis, AC joint arthritis, long head of biceps problems, frozen shoulder or shoulder impingement, then a normal shoulder MRI should suffice.

What does a shoulder MRI arthrogram scan involve?

A shoulder arthrogram will involve you having a shoulder injection first. This is done under imaging guidance (ultrasound or x-ray) to ensure the dye is injected accurately inside the shoulder joint. If the procedure is done under ultrasound guidance, the injection is usually done from the back of the shoulder. The skin at the injection site will be cleaned, and the area will be prepared as the procedure is done under very strict clean conditions (called the aseptic technique). Numbing medication will be administered to the skin using a small needle. Then, a needle will be inserted into the shoulder joint under imaging guidance, and a small volume of the special dye (usually 10-15 mls) will be injected slowly into the shoulder joint.

After the injection, you will be directed to the MRI room for the scan. You will need to stay still for approx. 20-30 minutes inside a special machine (small tunnel) while the images are taken. It can be slightly noisy while you are inside the machine therefore, ears protection or headphone with music will be used while you are inside the scanner. The imaged body part (the shoulder) will be put inside a small plastic device (called the coil). This is very useful to obtain detailed images of the shoulder joint. The technician will see you before the scan to ensure that you do not have any metallic objects before going into the scanner. To find out more, please see our article about shoulder MRIs.

The obtained images will be interpreted by a special doctor (a musculoskeletal radiologist) who will produce a detailed report of the findings and the diagnosis. This will be sent to the shoulder specialist, who will discuss it with you to decide on the appropriate management options.

What to expect during/after shoulder arthrogram injection?

You may feel a gradual build-up of pressure inside the shoulder. When the procedure is done, your shoulder might feel slightly tight. This may last for a day or two, although most patients report going back to their baseline the next day.

How long does shoulder arthrogram injection take?

Usually, 30 minutes is a reasonable time for the whole procedure (including explanation to the patient and preparation). The MRI examination should take another 20-30 minutes.

What are the possible complications of shoulder arthrogram injection?

The complications are very rare in general. In addition to the possible mild discomfort, there is a very small risk of infection (less than 1 in 10.000), similar to any other shoulder injection. There is also a very small risk of allergic reaction to the dye. Please see our FAQs for more information.