Shrug radiographs for the diagnosis of long thoracic nerve palsy in traumatic brachial plexus injury.

Abstract

Preoperative diagnosis of long thoracic nerve (LTN) palsy is important for shoulder reconstruction after a traumatic brachial plexus injury (BPI). In the present study, we developed an objective diagnostic method for LTN palsy for patients with traumatic BPI. This is a retrospective review of 56 patients with traumatic BPI who had been receiving treatment at a single institution for over 8 years. The patients were divided into 2 groups: an LTN palsy group (n = 30) and a no palsy control group (n = 26). The LTN palsy group had 21 different palsy types with 4 and 5 C5-7 and C5-8, whereas the no palsy group had 18 different palsy types with 5 and 3 C5-6 and C5-8, respectively. Preoperative plain anteroposterior radiographs were taken in shoulder adduction and shrug positions. Scapulothoracic (ST) upward rotation and clavicle lateral (CL) rotation angles were measured on X-rays. The differences between the adduction and shrug positions for the respective angles were calculated and defined as Φ_ST and Φ_CL, respectively. The differences in the Φ_ST and Φ_CL values due to the presence or absence of LTN palsy were examined, the cutoff values of Φ_ST and Φ_CL for the diagnosis of LTN palsy were determined, and further sensitivity and specificity were calculated. Both Φ_ST and Φ_CL were significantly decreased in the LTN palsy group compared with the no palsy control group. The sensitivity and specificity for LTN palsy were 0.833 and 1.000 for Φ_ST and 0.833 and 0.840 for Φ_CL, respectively, when the cutoff value was set as Φ_ST = 15° and Φ_CL ≤ 24°. Dynamic shrug radiographs provide a useful objective diagnosis of LTN palsy after traumatic BPI.