The Plantar Fascia Talar Head Correlation: A Radiographic Parameter With a Distinct Threshold to Validate Flatfoot Deformity and Its Corrective Surgery on Conventional Weightbearing Radiographs

Background: Corrective surgery for flexible flatfoot deformity (FD) remains controversial, and one of the main reasons for this is the lack of standardized radiographic measurements to define an FD. Previously published radiographic parameters to differentiate between a foot with and without an FD do not have a commonly accepted and distinct threshold. Methods: The plantar fascia–talar head correlation (PTC) with its defined threshold was assessed by measuring the distance between the medial border of the plantar fascia and the center of the talar head (DPT) on conventional dorsoplantar and lateral weightbearing radiographs; the authors were blinded to the clinical diagnosis of the 189 patients’ first visits. Feet were sorted into groups with and without an FD based on their clinical examination. The effect of operative corrections of FD on the PTC was retrospectively evaluated on an additional 38 patients. Results: The sensitivity of the PTC was 0.98 (95% CI: 0.9-1) and specificity 0.96 (95% CI: 0.92-0.98), respectively, to identify an FD, consistent with the clinical examination. Thirty-five of 38 surgeries sufficiently corrected the FD and the PTC comparable to that in subjects without an FD. Three corrections with a residual FD did not adequately correct the PTC. Conclusion: The PTC is a reliable radiographic parameter with a distinct threshold that is sensitive and specific for the differentiation of feet with and without an FD including feet with and without residual FD after corrective surgery. The PTC is applicable to monitor the needed intraoperative amount of correction using simulated weightbearing fluoroscopy. Level of Evidence: Level III, diagnostic.