The effect of injection volume on long-term outcomes of US-guided subacromial bursa injections.

ABSTRACT

PURPOSE: Limited data exist on the efficacy of high- compared to low-volume US-guided corticosteroid injections (CI) in the subacromial-subdeltoid (SA-SD) bursa. Our purpose was to compare the short- and long-term efficacy of low- and high-volume injections, by using a capacity reference of SA-SD bursa volume, as assessed on cadaveric specimens. METHOD: Within two years, 136 patients (63 males, 73 females; mean age 46.11 ±â€¯10.28 years) who underwent SA-SD bursa US-guided CI for subacromial impingement, rotator cuff tendinopathy or shoulder overuse were prospectively included. Patients were randomly assigned to low-volume (1 mL triamcinolone acetonide/40 mg) or high-volume (1 mL triamcinolone acetonide/40 mg, 9 mL anaesthetic agents) groups (67 and 69 patients, respectively). Visual Analogue Scores (VAS) were recorded at baseline, 30 min, 3 weeks, 3 months, 6 months and 1 year post-treatment. Predictors of complete recovery (VAS ≤ 2) at 1 year were analysed with multivariate Cox regression analysis. SA-SD bursa cadaveric dissection in 10 specimens was performed for volume assessment. RESULTS: Injection volume was the only predictor of complete pain resolution at 1 year. High-volume CI yielded higher chances of early pain recovery (2.837 HR, 95% CI 1.737-4.633, P < .001). Mean VAS scores at baseline and subsequent time-points were 6, 2.6, 2.2, 2, 1.6 and 1 for the high-volume and 7.8, 7.3, 4.7, 3.2, 2.5 and 1.8 for the low-volume group, respectively (P < .001, at all time-points). Cadaveric measurements showed a minimum SA-SD bursa volume of approximately 6.9 mL. CONCLUSIONS: High-compared to low-volume US-guided CI are superior for achieving early pain recovery.