This study aimed to examine the mobility and muscle activity of the thoracohumeral (TH) and glenohumeral (GH) joints. About 13 patients were enrolled and assessed following latissimus dorsi transfer (LDT) by researchers who had preoperative clinical pseudoparalysis. In both the LDT and the asymptomatic contralateral shoulder (ACS), 3D electromagnetic tracking was employed to quantify shoulder active range of motion (ROM). The maximum active elevation of the shoulder (MAES) was measured, including forwarding flexion, scapular abduction, and coronal plane abduction. Separately, the maximum active internal and exterior rotations were measured by Researchers. During shoulder motion, surface electromyography (EMG) was used to track the activation of the latissimus dorsi (LD) and deltoid muscles. The maximum isometric voluntary contraction (MIVC) recorded in specific strength tests was used to scale EMG. 

The LDT shoulder’s TH motion was not substantially different from the ACS in MEAS, F(1,12)=1.174, p=0.300, while the GH contribution was significantly lower in the LDT shoulder for all motions (1,12) =11.230, p=0.006. The ACS had significantly higher external rotation (LDT 26°±10°, ACS 42°±11°; P<0.001). During MAES, there was no significant difference in LD % EMG max between LDT and ACS F(1,11)=0.005, p=0.946. The LDT had a greater % EMG max during maximal active external rotation in the shoulder than the ACS (LDT 3.0%±2.9, ACS 1.2%±2.0; P=0.006). In a pseudoparalytic MIRT, TH motion improved after LDT and was similar to the ACS except for external rotation. However, inactive elevation ROM GH motion was considerably lower after LDT than in the ACS. Except for active external rotation, which researchers did not deem important because the activity did not increase above 3% EMG max, the LD was active after LDT but not more than in the ACS.