AC Joint Injection

AC Joint Injection is used to diagnosis and treatment of osteoarthritis and distal clavicular osteolysis of the Acromioclavicular Joint.

Pain in the AC joint can be traumatic or non-traumatic:

• Traumatic AC joint pain is typically the result of a direct blow to the superior or lateral aspect of the shoulder. The impact results in a partial or complete tear of the ligamentous structures within the joint, more commonly known as a separated shoulder, and frequently occurs in contact sports such as football and hockey.
• The most common non-traumatic causes of pain in the AC joint are overuse, degenerative changes, and distal clavicle osteolysis.

See Also: Distal Clavicle Osteolysis

Related Anatomy

The acromioclavicular joint line runs in the sagittal plane, about a thumb’s width medial to the lateral edge of the acromion. The joint plane runs obliquely medially from superior to inferior and usually contains a small meniscus. Often, a small step can be palpated where the acromion abuts against the clavicle, or a slight V-shaped gap can be felt at the anterior joint margin. Passively gliding the acromion downwards on the clavicle may help in finding the joint line.

See Also: Clavicle Anatomy

Equipment Needed

The Equipment and tools needed for Acromioclavicular Joint Injection include the following:

AC Joint Injection Technique

• Patient sits supported, with arm hanging by the side to slightly separate joint surfaces.
• Identify lateral edge of acromion. Move palpating digit medially about a thumb’s width and mark midpoint of joint line.
• Insert needle, angling medially about 30 degrees from the vertical and pass through capsule.
• Inject solution as a bolus.

See Also: AC Joint Separation

Aftercare

Reevaluate patient and have them passively range the shoulder to determine whether there is clinical improvement.

Begin gentle mobilizing exercises as soon as possible. Acutely inflamed joints are helped by the application of ice, taping across the joint to stabilize it and by oral analgesia.

Contraindications

Contraindications to AC joint injection include:

1. AC joint septic arthritis.
2. Cellulitis in the area of injection.
3. hypersensitivity or known allergy to the injected solution.
4. skin breakdown at the injection site.
5. a fracture at the proposed injection site.
6. Caution is advisable in patients on anticoagulation or with known bleeding disorders.

Notes

• Occasionally, the joint is difficult to enter; it is normally a narrow space and degenerative changes may make it more so. Traction on the arm can open up the joint space.
• To avoid unnecessary pain, peppering of the capsule with the solution will anaesthetize it while feeling for the joint space with the needle.
• The AC joint can also be injected anteriorly and horizontally at the V-shaped anterior gap if the superior approach is difficult.
• The unstable or repeatedly subluxing joint can be helped by sclerosing injections or possibly surgery.

References

1. Merrigan B, Varacallo M. Acromioclavicular Joint Injection. [Updated 2022 May 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK547727/
2. Saccomanno MF, DE Ieso C, Milano G. Acromioclavicular joint instability: anatomy, biomechanics and evaluation. Joints. 2014 Apr-Jun;2(2):87-92.