Methodological Biases in Adult-Acquired Flatfoot Deformity Research: A Systematic Analysis of Study Design Limitations

Abstract

Aims: Adult-acquired flatfoot deformity (AAFD) research has historically emphasized posterior tibial tendon dysfunction while underestimating medial ankle ligamentous pathology. This study systematically examines how specific methodological biases in research design have obscured the early and mechanistically significant role of the spring ligament and deltoid ligament complex. Methods: analyzed 195 papers from multi-database searches (Sci Space, PubMed, Google Scholar) examining AAFD pathomechanics, imaging assessment, and clinical outcomes published between 2010-2025. Studies were systematically evaluated for five categories of methodological bias: temporal bias (study design and timing), assessment bias (measurement approaches), measurement bias (outcome instruments), publication bias (reporting patterns), and conceptual bias (theoretical frameworks). Results: Five interconnected methodological biases were identified. Temporal bias: 85% of studies employed cross-sectional designs preventing determination of primary versus secondary pathology. Assessment bias: reliance on static imaging underestimated dynamic ligamentous function, with weight-bearing CT revealing pathology invisible on conventional imaging. Measurement bias: absence of validated ligament-specific outcome measures created circular reasoning where ligament pathology was deemed clinically irrelevant. Publication bias: surgical literature over represented tendon-focused interventions by 4:1 ratio. Conceptual bias: tendon-centric paradigms predetermined research questions and variable selection. Conclusion: Methodological choices, not biological reality, have systematically underestimated ligament contributions to flatfoot progression. Addressing these limitations requires longitudinal study designs, dynamic functional assessment protocols, development of validated ligament-specific outcome measures, and hypothesis-driven research explicitly testing ligament roles. Recognition of these biases is essential for advancing AAFD pathomechanics understanding and improving clinical assessment strategies.