Intercuneiform Instability is Present in Midfoot Arthritis Patients: A 3D Volumetric Case-Control Assessment

Abstract

Category: Midfoot/Forefoot; Trauma Introduction/Purpose: Lisfranc complex stability, primarily coming from the tarsometatarsal ligaments, is crucial for midfoot integrity. It has been shown that Lisfranc injuries can lead to midfoot issues, such as midfoot arthritis when not properly diagnosed/treated. Previous studies have estimated the volumes of the articulating joint volumes of surgically confirmed Lisfranc Ligament injuries, but no study has assessed articulating joints and space-of-interest of the Lisfranc Complex in patients with midfoot arthritis. The objective of this retrospective study was to determine if patients with confirmed midfoot arthritis have increased volumes at the Lisfranc complex when compared to controls, particularly between the first and second rays. We hypothesized that volumes would be increased in midfoot arthritis patients, consistent with medial column/first ray instability. Methods: In this IRB-approved, retrospective case-control study, we analyzed WBCT data of 20 consecutive midfoot arthritis patients and 20 healthy controls. Using an automated segmentation method (DISIOR Bonelogic 2.0, Paragon28, USA), 3D volumetric models of the bones of the foot were created from WBCT data. Opposing articular spaces in the Lisfranc joint of the midfoot were selected on the STL models of the bones. Interarticular distance mapping was then performed to characterize the joint space width (JSW) in each of the articulations. Interarticular volume was then estimated using an area-weighted volume measurement. Areas of each triangle from the triangulated surface were multiplied by the JSW at each triangle. The sum of individual volumes was then normalized by the total surface area. The final volume was estimated using the product of the normalized summation and average area of both surfaces. Comparisons were performed with independent t-tests. P-values >0.05 were considered significant. Results: Estimates of joint volume were obtained using the automated method written in MATLAB. These outputs are reported in Table 1. Significant increase of approximately 25% was observed in Midfoot arthritis patients at the 1-2 intercuneiform joint, consistent with intercuneiform instability. Conversely, a decrease in the space between the second metatarsal and medial cuneiform of about 30% was observed, what could be explained by pronation of the first ray secondary to first ray instability. All other changes in joint volumes were not significant (Figure). Conclusion: In this case-control study with midfoot arthritis patients and healthy controls we performed a 3D volumetric assessment of the Lisfranc Complex joints and spaces-of-interest. We found that midfoot arthritis patients have a significant increase in the 1-2 intercuneiform joint consistent with intercuneiform instability. Conversely, a decrease in the Lisfranc space (in between second metatarsal and medial cuneiform) was observed, what could be explained by first ray pronation in the setting of medial column instability. Additional prospective studies assessing angular measurements and patient reported outcomes are needed.