The reliability of talonavicular uncoverage to indicate forefoot abduction in progressive collapsing foot deformity: a finite element analysis.

Abstract

Background: Progressive Collapsing Foot Deformity (PCFD) presents various deformities. While medializing displacement calcaneal osteotomy (MDCO) and lateral column lengthening (LCL) are commonly employed as corrective surgeries, their impact on foot structure and functionality necessitates detailed biomechanical analysis. The objective of this study is to analyze the reliability of using talonavicular uncoverage percentage (TUP) as a metric for assessing the degree of forefoot abduction.

Methods: Seven subject-specific flatfoot models were constructed based on previous study. Finite element analysis was conducted to simulate stress distribution and contact characteristics in PCFD. Models were categorized based on TUP values, and MDCO was performed to analyze stress changes in the medial longitudinal arch and contact characteristics of subtalar joint.

Results: The study revealed discrepancies in TUP measurements between plain radiographs and three-dimensional models. Comparative analysis of the seven models showed that TUP exceeding 40% showed varied stress responses. A newly introduced parameter, the distance from the center of the head of the second metatarsal to the talar body axis (DSMT), demonstrated potential as a more dependable indicator. Models with DSMT below 20 mm experienced a remarkable reduction in ligamentous stress and notable change in region of stress concentration on the subtalar joint surface after MDCO, while those above 20 mm showed no noteworthy change.

Conclusion: The study suggests that TUP may not be a reliable indicator for LCL surgery in PCFD, highlighting the need for improved assessment parameters. DSMT shows promise as a more dependable indicator, warranting further research to validate its efficacy. Enhanced indicators will facilitate better surgical planning in PCFD corrective procedures.

Clinical relevance: Accurate assessment of flatfoot deformities is crucial for developing effective treatments. DSMT , which utilizes the talar body axis as a reference, is not affected by anatomical variations in the talar head body angle, rendering it more reliable for assessment of forefoot abduc tion. Improved indicators will contribute to better surgical decision making and patient outcomes in PCFD.