Biomechanical effect of instability at tendon transfer insertion in reverse shoulder arthroplasty with modified L'Episcopo procedure using fresh frozen cadaver

Reverse shoulder arthroplasty (rTSA) often has favorable postoperative outcomes but does not improve external rotation in patients with severe loss of shoulder external rotation. A modified L'Episcopo procedure was introduced to address this issue, but the optimal tendon transfer positions remain unclear. Instability is also a significant complication of rTSA. This study examines the biomechanical stability of rTSA with the modified L'Episcopo procedure using fresh-frozen cadavers. Eight cadaveric upper limbs were used, with tendon transfer positions set at 225°, 270°, and 315° from the bicipital groove in the horizontal plane, and at the teres minor attachment and the middle level of the latissimus dorsi (LD) in the vertical plane. Six shoulder joint positions were evaluated. No significant stability differences across rotational or horizontal tendon transfer positions at 30° and 60° abduction. In the vertical plane, however, the teres minor level provided greater stability than the middle level of the LD ( P < .05). Stability improved at 60° abduction and with subscapularis repair, equalizing teres minor level and the middle level of the LD stability differences. Tendon transfer to the teres minor level and subscapularis repair enhance anterior stability, suggesting these techniques may improve rTSA outcomes with the modified L'Episcopo procedure.