The modified Lapidus fusion: a systematic review of biomechanical studies

Abstract

Purpose The biomechanical characteristics of different techniques to perform the modified Lapidus procedure are controversial, discussing the issue of stability, rigidity, and compression forces from a biomechanical point of view. The aim of this systematic review was to investigate the available options to identify whether there is a procedure providing superior biomechanical results. Methods A comprehensive literature search was performed by screening PubMed, Embase, and Cochrane databases until September 2021. There was a wide heterogeneity of the available data in the different studies. Load to failure, stiffness, and compression forces were summarized and evaluated. Results Seventeen biomechanical studies were retrieved – ten cadaveric and seven polyurethane foam (artificial bone) studies. Fixation methods ranged from the classic crossed screw approach (n = 5) to plates (dorsomedial and plantar) with or without compression screws (n = 11). Newer implants such as intramedullary stabilization screws (n = 1) and memory alloy staples (n = 2) were investigated. Conclusion The two crossed screws construct is still a biomechanical option; however, according to this systematic review, there is strong evidence that a plate–screw construct provides superior stability especially in combination with a compression screw. There is also evidence about plate position and low evidence about compression screw position. Plantar plates seem to be advantageous from a biomechanical point of view, whereas compression screws could be better when positioned outside the plate. Overall, this review suggests the biomechanical advantages of using a combination of locking plates with a compression screw.