The axillary nerve and adhesive capsulitis

The axillary nerve (yellow arrow) and the posterior humeral circumflex artery (red arrow) in the region of the quadrilateral space. Note proximity to the inferior capsule.

The axillary nerve is closely related to the inferior capsule of the shoulder. It passes inferior to the subscapularis muscle and travels adjacent to the capsule before entering the quadrilateral space.

The axillary nerve is associated with adhesive capsulitis in at least 2 ways.

First, the axillary nerve can be irritated in the setting of inflammation and thickening of the inferior capsule. The evidence for this is somewhat anecdotal, but makes anatomic sense. The image below is from a patient with adhesive capsulitis. Note the teres minor atrophy (green arrow) in the setting of thickening of the inferior capsule (blue arrow), and constrained fluid in the joint (orange arrow) being forced into the superior subscapularis recess (orange*). The bone lesions are from myeloma, in case you were wondering.



Second, the close proximity of the nerve to the joint capsule predisposes it to injury during arthroscopic capsule release for treatment of adhesive capsulitis. Risk of injury is decreased by placing the incision of the glenohumeral joint capsule at the glenoid insertion with the arm in the abducted and externally rotated position.

We can appreciate the extent of inflammation on other imaging modalities too. On FDG PET/CT, for example, patients with adhesive capsulitis tend to have uptake at the inferior capsule that extends into the adjacent tissues.

References

• Sridharan R, Engle MP, Garg N, Wei W, Amini B. Focal uptake at the rotator interval or inferior capsule of shoulder on ¹⁸F-FDG PET/CT is associated with adhesive capsulitis. Skeletal Radiol. 2017 Apr;46(4):533-538.
• Salem U, Zhang L, Jorgensen JL, Kumar R, Amini B. Adhesive capsulitis mimicking metastasis on 18F-FDG-PET/CT.Clin Nucl Med. 2015 Feb;40(2):e145-7.
• Jerosch J, Filler TJ, Peuker ET. Which joint position puts the axillary nerve at lowest risk when performing arthroscopic capsular release in patients with adhesive capsulitis of the shoulder? Knee Surg Sports Traumatol Arthrosc. 2002 Mar;10(2):126-9.
• E. B. G. D. Santos, P. M. E. Souza (pdf). Teres minor beyond quadrilateral space syndrome: a pictorial review. ECR 2014 conference.