Finite element analysis of an intramedulary anatomical strut for proximal humeral fractures with disrupted medial column instability: A cohort study.

Abstract

Lateral locking plate (LLP) fixation has gained popularity for the treatment of proximal humeral fractures (PHFs); however, complications can occur due to loss of the medial cortical buttress from fracture comminution. We designed a novel intramedullary anatomical medial strut with allograft bone (IAMSAB) using MIMICS software to specifically fill the intramedullary canal of the proximal humeral bone. We used finite element analysis to evaluate the biomechanical characteristics of a LLP, LLP-intramedullary fixation system (IFS), LLP-anatomical medial locking plate (AMLP), or the combined application of a LLP and IAMSAB (LLP-IAMSAB) fixation construct in patients with a PHF and an unstable medial column. For axial or rotational loads, under (normal) Nor or osteoporotic (Ost) bone conditions, the LLP-IAMSAB fixation construct was significantly stiffer than the LLP-IFS fixation construct, and displacement at the fracture site after LLP-IAMSAB fixation was significantly less than after LLP or LLP-IFS fixation (P<0.05). Stiffness of the LLP-IAMSAB and LLP-AMLP fixation constructs and displacement at the fracture site after LLP-IAMSAB and LLP-AMLP fixation were not significantly different. The IFS, AMLP, and IAMSAB shared the load in the LLP and decreased the risk of implant failure. There were no significant differences in von Mises stress and stress distribution after fixation with the LLP-IFS, LLP-AMLP, and LLP-IAMSAB constructs. These data suggest that the IAMSAB can provide direct medial support or resistance to rotation and augment the biomechanics of the LLP. The combined application of the IAMSAB and LLP may achieve functional outcomes that are similar to the LLP-AMLP fixation construct.