The modified Lapidus fusion: a systematic review of biomechanical studies

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.