Reconstruction of proximal humeral fractures with a reduced number of screws and a reinforced bone substitute

Abstract

Multi-fragmented fractures of the proximal humerus are difficult to treat, especially in the case of osteoporotic bone. Intra-operative risks include cartilage damage when inserting multiple screws. A common post-operative complication is distal-varus collapse of the head. The aim of this study was to investigate if an Innovative technique (reduced number of screws and injection of a beta-TCP additivated partially resorbable cement) provides the same or better stability of the reconstructed head compared to the Standard technique (using more screws). A four-fragment fracture was simulated in six pairs of humeri, with partial removal of the cancellous bone to simulate osteoporotic "eggshell" defect. One humerus of each pair was repaired with a Standard (locking plate, 2 cortical and 6 locking screws), and the other with the Innovative technique (same plate, 2 cortical and only 3 locking screws, plus cement injection). The reconstructed specimens were subjected to a biomechanical test where a cyclic force of increasing amplitude was applied axially until failure. The Innovative reconstructions withstood a force 3.49 times larger than the contralateral Standard reconstructions before failure started. The maximum force before final collapse for the Innovative reconstructions was 4.24 times larger than the contralateral Standard reconstructions. These differences were statistically significant. The Innovative reconstructions, based on fewer screws and beta-TCP additivated acrylic cement, showed positive results, demonstrating better biomechanical properties compared to the Standard reconstructions. These laboratory findings, along with the advantages of a reduced number of screws, may help perform a surgically safer, and more effective procedure in osteoporotic patients.

Keywords: Augmentation; Locking plate; Number of screws; Osteoporotic multi-fragment fracture; Proximal humeral fracture.