Biomechanical Effectiveness of Lower Trapezius Tendon Transfer with Intercalary Tendon-Bone Graft versus the modified l'Episcopo Procedure in Reverse Total Shoulder Arthroplasty with Proximal Humeral Bone Loss.

Abstract

Aim & Background: In reverse total shoulder arthroplasty (RSA), proximal humeral bone loss (PHBL) is associated with higher complication rates and inferior functional results, particularly loss of active external rotation (ER). Traditionally, adjunct tendon transfers such as the latissimus dorsi transfer (LDT) or the modified l'Episcopo procedure have been employed to address this. Recently, in native shoulders, lower trapezius transfer (LTT) has gained popularity as an alternative method to restore ER. To date, almost no literature exists on its use in RSA. The purpose of this study was to evaluate the biomechanical effectiveness of a novel, modified LTT technique using a tendon-bone allograft (LTT+), that aims to reconstruct the greater tuberosity in situations of PHBL, and to compare it with the modified l'Episcopo procedure. It was the hypothesis of this study, that LTT+ would provide comparatively higher ER and lower adduction (ADD) moments. Method(s): Ten right, cadaveric upper limbs were prepared by resecting the proximal humerus including both tuberosities, thus creating moderate PHBL (~4cm). RSA was performed, and both an LTT+ and a l'Episcopo were added. The specimens were mounted on a custom-built testing apparatus, and an optical motion analysis system was employed to record joint kinematics and tendon excursions. During passive rotational and abduction-adduction motion cycles, the ER and ADD moment arms were computed using the tendon-excursion method. Result(s): Both LTT+ and l'Episcopo are biomechanically effective in generating shoulder ER in RSA with PHBL. LTT+ moment arms were higher, significance being reached in end-range ER positions. For pooled internal rotation (-20degree to 0degree rotation), low (0degree to 45degree rotation) and high ER (45degree to 70degree rotation), the mean differences of the ER moment arms were significant in all abduction positions (p<0.0001 for all three groups). The ADD moment arms of LTT+, measured in neutral rotation in the scapular plane between 40degree and 70degree abduction, were significantly lower than l'Episcopo's (p<0.0001). The differences were most relevant in lower degrees of abduction. Conclusion(s): Biomechanically, both LTT+ and the modified l'Episcopo procedure demonstrated effective shoulder ER capacity when added as adjunct procedure to RSA. LTT+ provided significantly higher ER moment arms and, additionally, lower ADD moment arms, thereby potentially avoiding antagonisms with the deltoid during abduction and elevation. These effects may strongly depend upon the transfers' insertion site and technique.Copyright © 2025