The present study evaluates changes in shoulder muscle function in patients with frozen shoulder syndrome (FSS) following manipulation under general anesthesia (MUA).

Fifteen FSS patients with mean (±SD) age of 53.6±9.7years were included in this study. Isometric endurance of the shoulder muscles was characterized by time and net impulse (NI), which were assessed with the patient holding a weight in the hand until exhaustion. Fatigability of the deltoid and trapezius muscles during isometric endurance test was assessed by electromyogram power spectrum median frequency (MF) slope per minute. Patients were also screened for daytime pain. Data were collected before MUA, and at 1 and 6months postoperatively.

Six months postoperatively, the MF slope for the trapezius and deltoid muscles of the involved and uninvolved shoulders did not differ (P>0.05), whereas NI remained lower and endurance time was longer (P<0.05). Shoulder pain was reduced as compared to preoperative levels (on visual analog scale) 1 and 6months postoperatively (P<0.05).

In patients with FSS, the fastest improvements in shoulder muscle NI, fatigability and pain take place in the first month after MUA; 6months after MUA, however, NI and endurance time remained impaired for the involved shoulder. Physiotherapy should pay more attention to muscle function recovery.

Level III, prospective follow-up study.