Comparison of the therapeutic effects of intramuscular subscapularis and scapulothoracic bursa injections in patients with scapular pain: a randomized controlled trial

Scapulothoracic bursitis contributes to considerable morbidity in some patients with scapular pain. A scapulothoracic bursa injection can induce symptomatic relief; however, blind injections into the scapulothoracic bursa may involve injecting into the subscapularis muscle itself. The aim of this study was to compare the therapeutic effects of intramuscular injections into the subscapularis under ultrasound (US) guidance with those of blind scapulothoracic bursa injections in patients with scapular pain. This study was a single-center, prospective, randomized, single-blinded, controlled clinical trial. Thirty-six patients with suspected scapulothoracic bursitis, who met the inclusion criteria, were recruited between January 2009 and December 2012. We performed three US-guided intramuscular injections into the subscapularis muscle or three blind scapulothoracic bursa injections at 1-week intervals. A visual analogue scale (VAS) and the Rubin scale at baseline and at 1, 2, and 3 weeks after the last injections were examined and again at 3 months after the last injections by a blinded investigator. Adverse effects were monitored. The VAS scores at baseline were 7.7 ± 1.3 and 7.8 ± 1.4 in the intramuscular injection and scapulothoracic bursa injection groups, respectively. Mean VAS scores after the intramuscular injections were 3.8, 2.7, 1.3, and 3.5, and mean VAS scores after scapulothoracic bursa injections were 4.1, 2.4, 1.6, and 2.9 at 1, 2, 3 weeks and at 3 months after the last injections. VAS scores decreased significantly after the injections in each group (p ≤ 0.05). However, no significant difference was observed between intramuscular injection into the subscapularis and the scapulothoracic bursa injection. No serious complications were encountered. In conclusion, injections at the scapulothoracic bursa without US guidance did not exclude the possibility of an effect of steroid on the subscapularis muscle, as both intramuscular injections into the subscapularis and scapulothoracic bursa injections in patients with scapular pain provided equal symptomatic relief, and all patients developed tenderness in their subscapularis muscle.