The Pattern of Medial Column instability in PCFD: A Preliminary Radiographic Study

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Arch collapse or in another word, medial column instability, is an important feature of multidimensional PCFD deformities. The Sagittal plane Meary’s angle has been commonly used to reflect arch collapse. However, this angle spans the talonavicular (TN), naviculocuneiform (NC), and 1st Tarsometatarsal (TMT) joints, therefore, it does not provide any information about through which joint(s) the medial column sags. The TN sag and 1st TMT joint sag have always been the focus of clinical practice, while sagging through the NC joint has not been fully investigated. This radiographic study investigated the radiographic features of medial column instability and more specifically with naviculocuneiform sag. Methods: This was an IRB approved retrospective study. The preoperative anteroposterior and sagittal plane radiographs of 30 patients with symptomatic Stage I PCFD (Classes A-D) from one center were included. Correlations were analyzed between the arch collapse (Sagittal Meary’s angle and arch height ratios) and Sagittal plane parameters (sagittal plantar wedge angle of the naviculocuneiform and 1st TMT joints, and the medial arch sag angle (MASA) which reflects the medial column sag at different joints, as well as deformity on the AP view (AP talonavicular coverage angle, AP Meary’s angle). Sag at the TN joint was not included because it cannot be accurately measured and has not been reported in the literature. Results: Demographic information is summarized in Table 1. There was severe arch collapse in this group with an average Sagittal Meary’s angle of -16.61 +/- 7.3 degrees and low arch height ratios (Table 2). There was no statistical difference between the NC plantar gap (5.17 +/- 2.06 degrees) and 1st TMT plantar gap (2.58 +/- 1.32 degrees). Sagittal Meary's angle was significantly positively correlated with MASA which more specifically evaluates NC sag. When MASA increased by 1 degree, Sagittal Meary’s Angle would increase by 0.95 degrees (P=0.0011, adjusted R-square = 0.30). The AP talonavicular coverage angle and AP Meary’s angle did not correlate with any sagittal plane parameters. Conclusion: The preliminary findings of this study indicate that in PCFD medial column instability, in addition to sagging through the 1st TMT joint, NC sag also plays an important role in the medial column collapse. Furthermore, the arch collapse was not significantly correlated with AP plane deformities. This may help with understanding the role of different joints in maintaining the stability of the medial column. Outcomes of the same study with a much larger sample size is in process.