Arthrogram (MRI)

An MR arthrogram is an MRI performed after a joint is injected with a solution containing gadolinium. Sometimes abbreviated to MRA, which can be confused with MR angiography. MRI can also be performed after an injection is not directly administered into the joint, via an indirect arthrogram. An arthrogram also refers to the procedure of injecting a joint.

Indications

• elbow: partial ulnar collateral ligament (UCL) tear
• hip: femoroacetabular impingement (FAI) / labral tears
• knee: repaired meniscus tears
• shoulder: instability/labral tears including superior labral anterior posterior (SLAP) tears, humeral avulsion of the glenohumeral ligament (HAGL) injuries
• wrist: triangular fibrocartilage (TFC) tear, scapholunate ligament tear

Contraindications

Absolute

• anaphylaxis to contrast medium/ injectate
• body habitus too large for local MRI
• MRI contraindication

Relative

• bleeding diathesis
• over 50 years of age
• unable to remain still for the procedure

Procedure

The arthrogram injection aim is to distend the joint with gadolinium containing solution, but not so distended to cause discomfort ^1,2.

Preprocedural evaluation

Relevant imaging should be reviewed and details of the patient confirmed. The patient should have an opportunity to discuss the risks and benefits and consent obtained. 

Risks include:

• infection
• bleeding
• allergy 

Driving is not advised after any injection, particularly if a local anesthetic is used.  The reasons include an inability to perform an emergency procedure and be in safe control of a vehicle.

Technique

Patient positioning and technique will vary depending on the joint, method of access and individual performing the injection ³. 

Steps of an arthrogram injection

• check for allergies and if on blood thinners
• consent
• optimize patient positioning
• optimize imaging and mark skin
• clean skin and draw up appropriate medications
• local anesthesia along the proposed needle path
• obtain joint access with image guidance
• confirm an intra-articular position
• administer MR arthrogram injectate
• apply dressing/ band-aid

The more commonly performed MR arthrograms are of the shoulder and hip. A glenohumeral joint injection (technique) can either be performed from anterior ^1,2,4 or posterior ⁵ approaches. The hip is injected from an anterior approach ^1,2. 

Equipment

• skin marker and a metal rod for marking (fluoroscopy)
• ultrasound machine and sterile probe cover (ultrasound)
• skin cleaning product
• sterile drape
• sterile field and tray for sharps
• syringe selection
• larger bore drawing up needle/ quill
• needle to administer local anesthetic i.e. 25-gauge needle
• needle to cannulate the joint i.e. 22-gauge Quincke needle
• short extension tubing
• injectants i.e. local anesthetic, saline, iodinated contrast, gadolinium
• sterile gauze
• adhesive dressing

Syringe selection

The injected solutions used in MR arthrogram injections are clear, therefore syringe selection is an important way of identifying the different solutions.  

A suggested syringe selection for a fluoroscopic MR arthrogram injection -

• 5 mL syringe: local anesthetic i.e. 1% lidocaine
• 10 mL syringe: non-ionic iodinated contrast i.e. iohexol 
• 20 mL syringe: arthrogram injectate

A suggested syringe selection for an ultrasound-guided MR arthrogram injection:

• 5 mL syringe: local anesthetic i.e. 1% lidocaine
• 20 mL syringe: arthrogram injectate

Arthrogram injectate

If performing ultrasound-guided injections, an intra-articular position is confirmed with direct visualization, therefore iodinated contrast is not required. Suggested arthrogram injectate mixtures are offered below.

Fluoroscopy:

• 20mL syringe containing: 0.1 mL gadolinium, 9.9 ml 0.9% saline, 5 mL 0.5% ropivacaine, 5 mL iohexol 

Ultrasound-guided:

• 20mL syringe containing: 0.1 mL gadolinium, 14.9 ml 0.9% saline, 5 mL 0.5% ropivacaine

The dilution of gadolinium is usually 1:200 therefore 0.1mL in 20 mL syringe ¹.  There are reported chondrotoxic effects of local anesthetics, and intra-articular lidocaine should be avoided. Other lower strength local anesthetics are reported as having less of a chondrotoxic effect. i.e. ropivacaine ⁶. Some institutions will not use a local anesthetic in their arthrogram injectate mixtures citing the above however its use has been shown to improve comfort and lessen movement artifact ⁷. Furthermore, a small amount included in the 20 mL arthrogram mixture can be useful diagnostically; if the patient has pain relief post-procedure, the injected joint is likely the pain generator. This combined with the imaging findings can help guide further treatment.

MR arthrogram requests

Request forms will be sent asking for imaging and it is implied a guided injection will take place before cross-sectional imaging. Waiting times are often longer for MR arthrograms and they involve an invasive procedure, therefore stricter guidelines are usually in place. An approximate upper age limit is 50 years old, after which time labral tears and arthropathy are more common. If imaging is requested and indicated in such patients, non-arthrogram MRI imaging is performed initially, and if the non-contrast imaging does not provide a sufficient answer, an MR arthrogram could be considered at that point.

MR arthrogram sequences

Gadolinium and fat are both high signal on T1 weighted sequences, whereas fluid is low signal. By using T1 weighted, fat-saturated sequences in MR arthrograms, we can identify areas that the high T1 signal gadolinium imbibes. Pathology in these areas, such as chondrolabral junction, would be less evident or not appreciable on non-fat saturated and fluid sensitive sequences nor in non-distended joints.