Reliability of the radiographic measurement of the hallux interphalangeal angle

Khademi, Mohammadaki
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Introduction: The hallux valgus interphalangeus (HVI) deformity has a common association with hallux valgus and hallux rigidus. The radiographic measurement of the hallux valgus interphalangeus is formed by the angle between the long axes of the proximal and distal phalanges. The normal value for this angular deformity in the coronal plane is less than 10 degrees. The reliability of measuring the hallux interphalangeal angle has not been verified as yet .The purpose of this study is to analyse the intra- and inter-observer reliability of measurements of the interphalangeal angle by orthopaedic surgeons. This study is going to be the first study to evaluate the reliability and reproducibility of the hallux valgus interphalangeal angle. Methods: Twenty one X-ray prints (images) of the weight bearing foot constituted a set. Three such sets were sent to each evaluator at four week intervals. Sixteen qualified orthopaedic surgeons were asked to measure the hallux interphalangeal angle of all twenty one X-ray images at three different occasions. After all three sets were measured, data was retrieved and statistically analysed to determine the incidence of inter- and intra-observer variability and reliability in the measurement of the hallux interphalangeal angle. Results: Reproducibility of the hallux interphalangeal angle measurement was assessed using three categories which included the ability to measure the same angle three times and achieve: three degrees or less, five degrees or less, more than five degrees. The intra-observer reliability was found to be 5 degrees and less in 75.2% of participants and for the inter-observer reliability was 61.2%. The researcher did not find significant correlation between the surgeons’ level of experience with respect to the reliability of measurement of the hallux interphalangeal angle. Conclusion: The reliability and reproducibility of measurement of the hallux interphalangeal angle is low. The level of experience of the surgeon does not improve this reliability.
A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Medicine, Johannesburg, 2018
Hallux Interphalangeal Angle, Radiographic Measurement