Reverse total shoulder arthroplasty with latissimus dorsi and teres major transfer: biomechanical and electromyographical outcomes.

Abstract

There is controversy regarding the optimal treatment for patients with rotator cuff arthropathy with external rotation deficit (CLEER group). This study analyzes the biomechanical and electromyographical outcomes of reverse total shoulder arthroplasty (RTSA) with latissimus dorsi and teres major transfer. The primary objective of this study is to compare the biomechanical and electromyographical outcomes between the treated and contralateral shoulder. Secondary objective is to define clinical and functional outcomes, and to report the radiological findings. Our hypothesis is that with this technique patients regain at least 50% of the strength in external rotation of the contralateral shoulder, and that the transferred muscles remain EMG active over time. All patients who underwent RTSA with latissimus dorsi and teres major transfer in our hospital between 2007 and 2015 were included. From 16 eligible patients, 10 were finally reviewed. Biomechanical assessment of rotation strength was performed postoperatively in both shoulders, and fine needle EMG of latissimus dorsi and teres major muscles was recorded at the same time in both shoulders. Constant test and clinical evaluation (Lag sign and Hornblower test) were obtained preoperative and at final follow up. Radiological (X-ray, US) assessment was also obtained for both shoulders at final follow up. External rotation strength of the operated shoulder was higher than 50% the strength of the contralateral shoulder, and the differences were statistically significant (p < 0.05). No statistically differences were found regarding to internal rotation. The electromyographic assessment found no significant differences (p > 0.05) between the treated and contralateral shoulders. The mean Constant-Murley score significantly increased (30.9 points) after surgery (p < 0.01). Lag sign and Hornblower test were negative in all patients. Performing RTSA with latissimus dorsi and teres major transfer is an effective procedure improve function and to restore ER strength in patients in CLEER group. The EMG records shows that transposed latissimus dorsi and teres major adapt to their new function and remain functional over time, even in elderly patients.