Regarding “Proximal humeral fracture fixation: a biomechanical comparison of two constructs”

Abstract

To the Editor: We read with interest the article entitled ‘‘Proximal humeral fracture fixation: a biomechanical comparison of two constructs,’’ 1 which biomechanically compared the DePuy S3 proximal humeral locking system (DePuy Orthopaedics, Warsaw, IN, USA) and Synthes proximal humeral locking compression plate (LCP) (Synthes, Paoli, PA, USA) in simulated proximal humeral fractures. It may be of interest to the authors of this article that these locking plate systems have indeed been previously compared in an osteoporotic 3-part fracture model. 2 This study showed that humeral heads fixed with the S3 plate showed significantly greater rotation into varus, with respect to the humeral shaft, than did humeral heads fixed with the LCP after 5000 cycles of loading through the supraspinatus tendon in the scapular plane. We would agree that, in osteoporotic bone, the S3 plate appears less able to prevent varus failure than the LCP, presumably because of its greater stiffness 1 and therefore greater mismatch at the bone-implant interface. In our 3-part model, we were also able to show greater displacement of the greater tuberosity fragment after cyclic loading with the S3 plate, likely because of its more distal position on the shaft at implantation.