Acromioclavicular joint (ACJ) injections under image guidance ensure precise delivery of an injectate into the joint. Ultrasound allows for real-time visualization of the needle and administration of the injectate. Fluoroscopy is an alternative method of image guidance.
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Indications
- pain: arthropathy i.e. osteoarthritis
- diagnostic injection
Contraindications
Absolute
- anaphylaxis to contrast/ injectates
- active local/ systemic infection
Relative
- bleeding diathesis
- recent injection with steroid in same/other body parts
- unable to remain still for the procedure
- young age
Procedure
The general principles of ACJ injections are to
- cannulate the joint
- confirm an intra-articular position with imaging
- administer intra-articular injectate, usually a corticosteroid and a small amount of longer-acting local anesthetic - the ACJ is a small joint therefore the injected volume should reflect this i.e maximum 2 mL
Pre-procedural 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
- focal fat necrosis/ skin discolouration at the injection site
- steroid flare
Equipment
- ultrasound machine, sterile probe cover and a skin marker (ultrasound)
- skin marker, a metal rod for marking and short connecting tube (fluoroscopy)
- skin cleaning product
- sterile drape
- sterile field and tray for sharps
- syringe selection i.e. 5mL and 3mL (US)
- larger bore drawing up needle
- needle to administer local anesthetic i.e. 30 or 25-gauge needle
- needle to cannulate the joint i.e. 25 or 27-gauge needle
- injectants i.e. local anesthetics, iodinated contrast, corticosteroid preparation
- sterile gauze
- adhesive dressing
Syringe selection
Using a Luer lock syringe to inject the smaller ACJ will mean no disconnection of the needle and syringe during the injection, as the joint is often under pressure.
A suggested syringe and injectate selection for an ultrasound-guided ACJ anesthetic arthrogram injection
- 5 mL syringe: 3 mL of local anesthetic i.e. 1% lidocaine
- 3 mL syringe (Luer lock): 40mg triamcinolone acetonide (40 mg/1 mL) and 1 mL 0.5% ropivacaine
A suggested syringe and injectate selection for a fluoroscopic-guided ACJ anesthetic arthrogram injection
- 10mL mL syringe: 3 mL of local anesthetic i.e. 1% lidocaine
- 5 mL syringe (Luer lock): 3 mL non-ionic iodinated contrast i.e. iohexol 300
- 3 mL syringe (Luer lock): 40mg triamcinolone acetonide (40 mg/1 mL) and 1 mL 0.5% ropivacaine
Needle selection
Smaller gauge needles can be less painful but are less stiff and can bend when trying to cannulate a joint.
- ACJ: 25 or 27-gauge needles
Technique
Ultrasound in-plane
- check for allergies and if on blood thinners
- consent
- optimize patient positioning by lying them flat and supine on the bed for cranial access, or at 45 degrees for anterior access
- identify ACJ in the transverse plane; perpendicular to the clavicle, and optimize imaging and mark skin entry point
- clean skin and draw up appropriate medications
- consider local anesthesia along the proposed needle path
- under ultrasound guidance using anterior or cranial access, insert the needle in-plane with the probe into the ACJ
- administer arthrogram injectate under direct visualization
- remove needle and apply dressing/ band-aid as required
Ultrasound out-of-plane
- check for allergies and if on blood thinners
- consent
- optimize patient positioning by lying them flat and supine on the bed or at 45 degrees, the joint will be accessed cranially
- identify the ACJ in a longitudinal plane; parallel to the clavicle, with the ACJ in the center of the image. Optimize imaging and mark skin at the probe midpoint
- clean skin and draw up appropriate medications
- consider local anesthesia along the proposed needle path
- under ultrasound guidance using cranial access, insert the needle at the probe midpoint and out-of-plane with the probe into the ACJ
- administer arthrogram injectate
- remove needle and apply dressing/ band-aid as required
Fluoroscopy
- check for allergies and if on blood thinners
- consent
- optimize patient positioning by lying them supine on bed, the joint is accessed anteriorly
- optimize imaging field and using the metal rod, mark the skin at the target entry at the midpoint of the joint
- clean skin and draw up appropriate medications
- consider local anesthesia along the proposed needle path
- under fluoroscopic guidance using anterior access, insert a needle into the ACJ
- check for an intra-articular needle tip position with a small amount of iodinated contrast via connection tubing and save a post injection image
- administer arthrogram injectate
- remove needle and apply dressing/ band-aid as required
Complications
Steroid flare is a relatively common side effect which will settle after 1 or 2 days. The most serious complication is infection causing septic arthritis. Steroid containing injections should be postponed if there are any signs and/or symptoms of local and/ or systemic infective. Fat necrosis causing skin dimpling and skin discolouration can occur due to steroid leaking into the surrounding soft tissues 1.