Suture Augmentation Neutralizes Deforming Muscular Forces in a Simulated 2-Part Osteoporotic Proximal Humeral Fracture Model

Objectives: To evaluate the contribution that tension-relieving sutures, placed between a proximal humeral locking plate and the rotator cuff muscles, had on preventing varus malalignment in an osteoporotic 2-part proximal humerus fracture model. Methods: A 2-part fracture model was created in 8 cadaveric specimens and then fixed with a lateral locking plate. A custom shoulder testing system was used to increase loading through the supraspinatus (SS) tendon to drive varus deformity. Trials were performed with no suture placement; SS only; SS and subscapularis (SB); and SS, SB, and infraspinatus. The primary outcome was contribution of each point of suture fixation to prevention of varus collapse. Results: Suture augmentation to the SS, SB, and infraspinatus significantly decreased humeral head varus collapse when compared with the plate alone at nearly all loads (P < 0.05). There were no significant differences in humeral head varus collapse between the 3 suture constructs. Conclusions: In our biomechanical evaluation of a simulated osteoporotic 2-part proximal humerus fracture with incompetent medial calcar, tension-relieving sutures placed between a lateral locked plate and the rotator cuff tendons prevented varus malalignment.