Electromyographic analysis of muscle function after latissimus dorsi tendon transfer.

The latissimus dorsi transfer is an established method for irreparable tears of the rotator cuff. The original task of the muscle is to move the arm downward and to rotate it internally. After the transfer, it has to perform the completely new function of elevating the arm. We used surface electromyography to calculate the mean values of the activity pattern in relation to the Constant score in 45 patients. We assessed patients after 6 weeks and at 6, 9, and 19 months. After the operation, most patients showed a typical activity pattern of the latissimus dorsi on electromyography, which improved in the course of the study. We also found a strong correlation between the activity pattern on electromyography and the Constant score in different areas. We conclude that the functional improvement is due to an active muscle contraction as shown on electromyography and is not just an interposition or tenodesis effect.