Conjoint Tendon Lengthening Improves Internal Rotation Following Reverse Total Shoulder Arthroplasty: A Cadaveric Study

Introduction Reverse Shoulder Arthroplasty (RSA) is a common procedure for treating a variety of shoulder pathologies. However, many patients struggle with postoperative internal rotation deficits, which often hinder their activities of daily living. The conjoint tendon provides an anatomic barrier that can impede the postoperative internal rotation of the shoulder, and this study aims to evaluate the effect of a conjoint tendon lengthening on the glenohumeral range of motion following RSA. Methods This study used ten fresh-frozen cadaver specimens of the upper extremity. An RSA was implanted using a standard deltopectoral approach, and the range of motion was assessed post-implantation. Following this, the conjoint tendon was identified and lengthened using a tendon sheath z-plasty, and the range of motion was re-recorded. Statistical significance for the range of motion gains after conjoint tendon lengthening was determined with a significance level of p < 0.05. Results Following the lengthening of the conjoint tendon, there were statistically significant improvements in all ranges of motion (p < 0.05). Subjects demonstrated a notable gain in internal rotation to the back by 10.3 cm (p < 0.01), and all ranges of motion increased by at least 10°, except for forward flexion, which increased by 6° (p < 0.001). Conclusions This study suggests that lengthening the conjoint tendon improves postoperative range of motion of the glenohumeral joint after RSA, offering a potential solution to a considerable internal rotation deficits that are commonly encountered post-RSA. Subsequent clinical and biomechanical studies should assess the stability of the shoulder joint following conjoint tendon lengthening.