Simulated Weight Bearing and Articular Injury From Transarticular Screws In A Lisfranc Injury Model

Abstract

Category: Midfoot/Forefoot, Trauma Introduction/Purpose: Successful treatment of Lisfranc injuries, relies upon anatomic reduction [1-3] and rigid fixation until bony or ligamentous healing has occurred and inherent stability has been restored. Historically, transarticular screw fixation has been the most common method of fixation, but optimal treatment remains controversial. Articular injury from transarticular screw fixation may lead to arthritis of the Lisfranc joints and future morbidity. To our knowledge only two studies have evaluated articular injury from transarticular screws [6,7]. Neither of these studies, and no other study to our knowledge has investigated relative increase in articular damage after simulated weight bearing. The aims of this study were: (1) create a ligamentous Lisfranc injury model and (2) compare relative increase in articular injury pre- and post-simulated weight bearing from screw toggle. Methods: 10 cadaver specimens underwent transarcticular screw fixation with 3.5 mm cortical screws in a ligamentous Lisfranc injury model. Digital photographs of the articular surfaces of the first and second tarsometatarsal joints were taken before and after cycling. Simulated weight bearing was performed with each specimen cycled 1,000 cycles at 222.4 N in a custom jig fixed in approximately 20 degrees of plantar flexion. After creation of the Lisfranc injury and prior to cycling with screw fixation, each specimen was cycled for 20 cycles to ensure we had created a reliable injury model. At each stage we assessed total relative rotation and diastasis between each of the bones of the Lisfranc complex. After simulated weight bearing hardware was removed and digital photographs were again taken. Articular injury was measured as a percentage of total articular surface pre- and post-cycling and was compared and statistical analysis performed. Results: Our model produced motion consistent with a ligamentous Lisfranc injury. Overall, the articular injury increased by 44.22% (p<0.001) after cyclic loading. With respect to each individual surface, the second metatarsal (M2) showed the greatest increase in articular injury (53.89%, p=0.0047) whereas the first metatarsal (M1) showed the least (34.71%, p=0.0083). The increases seen at the medial cuneiform (43.51%, p=0.0387) and the middle cuneiform (44.24%, p=0.0292) were intermediate between the values seen at M2 and M1 (Table 1). Conclusion: Our model produced motion consistent with a ligamentous Lisfranc injury. The articular injury from transarticular screw fixation showed a significant increase in articular injury with cyclic loading at each of the articular surfaces of interest and a 44% overall increase in articular damage with simulated weight bearing. This relative increase in articular injury has never previously been studied. This increase in articular injury from screw toggle with simulated weight bearing with use of trans- articular screw fixation is significant and may increase the risk of arthritis and future morbidity when using this fixation strategy.