Reliability of ultrasound for measurement of selected foot structures

Background: Understanding the relationship between the lower leg muscles, foot structures and functionis essential to explain how disease or injury may relate to changes in foot function and clinical pathology.The aim of this study was to investigate the inter-operator reliability of an ultrasound protocol toquantify features of: rear, mid and forefoot sections of the plantar fascia (PF); flexor hallucis brevis (FHB);flexor digitorum brevis (FDB); abductor hallucis (AbH); flexor digitorum longus (FDL); flexor hallucislongus (FHL); tibialis anterior (TA); and peroneus longus and brevis (PER).Methods: A sample of 6 females and 4 males (mean age 29.1 x 7.2 years, mean BMI 25.5 x 4.8) wasrecruited from a university student and staff population. Scans were obtained using a portable Venue 40musculoskeletal ultrasound system (GE Healthcare UK) with a 5–13 MHz wideband linear array probe with a12.7 mm x 47.1 mm footprint by two operators in the same scanning session.Results: Intraclass Correlation Coefficients (ICC) values for muscle thickness (ICC range 0.90–0.97),plantar fascia thickness (ICC range 0.94–0.98) and cross sectional muscle measurements (ICC range0.91–0.98) revealed excellent inter-operator reliability. The limits of agreement, relative to structuresize, ranged from 9.0% to 17.5% for muscle thickness, 11.0–18.0% for plantar fascia, and 11.0–26.0% forcross sectional area measurements.Conclusions: The ultrasound protocol implemented in this work has been shown to be reliable. Ittherefore offers the opportunity to quantify the structures concerned and better understand theircontributions to foot function