Reliability and correlates of cross‐sectional area of abductor hallucis and the medial belly of the flexor hallucis brevis measured by ultrasound

Abstract

BackgroundWeakness of the intrinsic foot muscles is thought to produce deformity, disability and pain. Assessing intrinsic foot muscles in isolation is a challenge; however ultrasound might provide a solution. The aims of this study were to assess the reproducibility of assessing the size of abductor halluces (AbH) and the medial belly of flexor hallucis brevis (FHBM) muscles, and identify their relationship with toe strength, foot morphology and balance.MethodsTwenty one participants aged 26–64 years were measured on two occasions for muscle cross-sectional area using a Siemens Acuson X300 Ultrasound System with 5-13 MHz linear array transducer. Great toe flexor strength was measured by pedobarography, the paper grip test and hand-held dynamometry. Foot morphology was assessed by foot length, truncated foot length, Foot Posture Index (FPI) and dorsal arch height. Balance was measured by the maximal step test. Intra-class correlation coefficients (ICC3,1) were used to evaluate intra-rater reliability. Pearson’s correlation coefficients were performed to assess associations between muscle size and strength, morphology and balance measures. To account for the influence of physical body size, partial correlations were also performed controlling for truncated foot length.ResultsIntra-rater reliability was excellent for AbH (ICC3,1 = 0.97) and FHBM (ICC3,1 = 0.96). Significant associations were found between cross-sectional area of AbH and great toe flexion force measured standing by pedobarography (r = .623, p = .003),), arch height measured sitting (r = .597, p = .004) and standing (r = .590, p = .005), foot length (r = .582, p = 006), truncated foot length (r = .580, p = .006), balance (r = .443, p = .044), weight (r = .662, p = .001), height (r = .559, p = .008), and BMI (r = .502, p = .020). Significant associations were found between cross-sectional area of FHBM and FPI (r = .544, p = .011), truncated foot length (r = .483, p = .027) and foot length (r = .451, p = .040). Significant partial associations were found between AbH and great toe flexion force in standing by pedobarography (r = .562, p = .012) and FHBM and the FPI (r = .631, p = .003).ConclusionsMeasuring the cross-sectional area of AbH and FHBM with ultrasound is reproducible. Measures of strength, morphology and balance appear to relate more to the size of AbH than FHBM. After controlling for physical body size, cross-sectional area of AbH remained a significant correlate of great toe flexor strength and might be a useful biomarker to measure early therapeutic response to exercise.

The Effects of Electrical Stimulation Program on Navicular Height, Balance, and Fear of Falling in Community-Dwelling Elderly

“…Fear of falling score clinically improved following 4 weeks of TENS compared with the CON group, possibly due to an increase in the strength of intrinsic foot muscles in the elderly, similar to the findings of a previous study [38]. The study of Hashimoto and Sakuraba (2014) [39] confirmed that strengthening the AbdH muscle results in better standing and walking performance.…”

Early-Stage Diabetic Neuropathy Reduces Foot Strength and Intrinsic but Not Extrinsic Foot Muscle Size

“…There were a few limitations in this study related to the ultrasound imaging methods. First, due to the FHL tendon location and double muscle head of the FHB, current methodology to obtain a CSA for FHB is dependent on the ultrasound operator to subjectively locate the thickest part of the muscle [19,50]. We chose a simpler thickness measurement at a uniform distance from the sesamoid bone of the hallux.…”

Use of Cine Loops and Structural Landmarks in Ultrasound Image Processing Improves Reliability and Reduces Error in the Assessment of Foot and Leg Muscles

“…Although optimal US settings (eg, transducer and frequency selection, depth, and focus position) are assumed across studies, transducer placement strategies and techniques have not been well standardized. Measurements of the foot muscles, for example, have been performed at the thickest part of the muscle, 50% of the foot length, and various positions on the leg referenced to internal bony landmarks . When measuring the abductor hallucis (ABDH) thickness, Mickle et al 20 found higher intraclass correlation coefficients (ICCs) and lower limits of agreement (LoAs) when using the medial malleolus landmark as opposed to the thickest part of the muscle, suggesting that the use of landmarks is likely more reliable than image‐based subjective locations.…”