ABSTRACT
INTRODUCTION: First Ray Instability (FRI) and especially hypermobility leads to the collapse of the medial longitudinal arch's structural framework, which reduces the foot's ability to become a rigid lever for propulsion, resulting in progressive foot deformities. Early detection of FRI with prompt intervention helps prevent degenerative foot deformities. Various manual, device-based and radiographic diagnostic tests for FRI quantification have been described in the literature. We aim to conduct an up-to-date, comprehensive, systematic review of the literature reporting on diagnostic tests to evaluate FRI. METHODOLOGY: Electronic databases (Medline, Embase and PubMed) and bibliography lists were searched until May 2021 for studies evaluating diagnostic tests for FRI. MeSH terms were used to conduct the literature search. The authors screened all produced abstracts. Selected articles were further assessed in full based on inclusion and exclusion criteria. The relevant studies were qualitatively assessed and grouped into tables based on tests. RESULTS: 18,176 studies were identified. Thirty-two full-text articles were included for assessment. Ten articles were excluded based on evaluation criteria. 18 studies were included for qualitative assessment: two studies describing manual diagnostic tests, three evaluating device-driven tests, six image-guided studies and seven comparison studies assessing a new test versus an established one. CONCLUSION: Gold standard tests in defining FRI need to be improved. Manual tests exhibit significant subjective variability. Radiographic tests, while accurate, are complex and cumbersome to perform and, therefore, are not widely applied. Dorsal rulers have demonstrated mixed results and shown variability when compared to instruments. The focus has been on assessing FRI in hallux valgus (HV). More studies are needed to investigate FRI in the absence of HV.
