Three-Dimensional Weightbearing CT Distance and Coverage Mapping of the Lisfranc Joint Complex: Agreement Between Contralateral and Matched-Control Feet.

BACKGROUND: Bilateral comparison is considered the reference standard for assessing subtle Lisfranc instability because it accounts for individual anatomic variation. However, contralateral imaging may be unavailable or unsuitable because of previous trauma, surgery, or deformity. PURPOSE: To evaluate whether matched controls could serve as an alternative reference for advanced weightbearing CT (WBCT) assessment of the Lisfranc joint complex. STUDY DESIGN: Retrospective matched case-control study METHODS: Contralateral uninjured feet from 34 patients with low-energy Lisfranc injuries were compared with contralateral feet from 34 matched controls. Matching was performed for sex, laterality, age, and body mass index. Three-dimensional WBCT distance mapping (DM) and coverage mapping (CM) were calculated for four Lisfranc articulations and subdivided regions following semi-automatic segmentation and manual surface selection. Paired two one-sided equivalence tests (TOST) used equivalence margins of ±0.5 mm for DM and ±10 percentage points for CM; Bland-Altman limits of agreement (LoA) were compared with these margins. RESULTS: Equivalence was demonstrated for all 16 DM outcomes and 15 of 16 CM outcomes. Plantar-medial C1-M1 coverage did not meet the equivalence criterion (mean difference, -6.8 percentage points; 90% confidence interval, -11.3 to -2.3; TOST p = 0.122). Bland-Altman limits of agreement were generally wider than the defined margins, indicating variability among individual matched pairs. CONCLUSIONS: Matched controls produced group-level DM and CM measurements comparable to contralateral feet for 31 of 32 evaluated outcomes. However, individual-level LoA generally exceeded the defined margins. Matched controls may therefore provide suitable group-level reference values when contralateral imaging is unavailable but should not be considered interchangeable with contralateral imaging for patient-specific assessment.