1000 Section - Injectate Distribution Patterns in Ultrasound-Guided Rotator Interval, Dual-Target, and Posterior Glenohumeral Injections

Objectives : Corticosteroid injections for adhesive capsulitis are commonly delivered through the rotator interval or posterior glenohumeral approaches, though injectate spread differs by technique. A dual-target method, combining rotator interval and subdeltoid bursal injections, has been suggested when subacromial impingement is present. This study compared dye distribution among the three approaches.

Design: Eighteen shoulders from nine embalmed cadavers received one of three ultrasound-guided injections: rotator interval (15 mL), dual-target (10 mL rotator interval + 5 mL subdeltoid bursa), or posterior glenohumeral (15 mL). Standardized dissections assessed dye penetration of the biceps tendon sheath, subdeltoid bursa, and anterior and posterior joint capsules (graded as absent, partial, or extensive).

Results: Rotator interval and dual-target injections produced consistent, extensive staining of the biceps tendon sheath and anterior capsule. The posterior approach showed variable anterior coverage. Only the dual-target technique reliably stained the subdeltoid bursa (5/6 shoulders). The posterior capsule was most completely infiltrated by posterior injections (6/6 extensive), followed by rotator interval (5/6) and dual-target injections (mixed partial/extensive). Infraspinatus involvement occurred only after posterior injections (2 shoulders).

Conclusion:

Injectate spread is technique-dependent. Rotator interval and dual-target injections best reach anterior structures, the dual-target approach uniquely covers the bursa, and posterior injections most effectively infiltrate the posterior capsule. Technique selection should match the patient’s predominant pathology.