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

Abstract

Objectives-Foot and leg muscle strength and size are crucial to proper function. It is important to assess these characteristics reliably. Our primary objective was to compare the measurement of still images to cine loops. The secondary purpose was to determine interoperator and intraoperator reliability between operators of different experience levels using video clips and internal and external landmarks.Methods-Twelve healthy volunteers participated in our study. Internal (navicular tuberosity) and external (lateral leg length at 30% and 50% from the knee joint line) landmarks were used. Two operators each captured and later measured still and cine loop images of selected foot and leg muscles.Results-The 12 participants included 8 male and 4 female volunteers (mean age AE SD, 23.5 AE 1.9 years). Good to excellent intraoperator and interoperator reliability was seen (intraclass correlation coefficient range of 0.946-0.998). The use of cine loops improved the intraclass correlation coefficients for both intraoperator and interoperator reliability (0.5%-4% increases). The use of cine loops decreased the intraoperator standard error of the measurement and limits of agreement of the novice operator (decreases of 45%-73% and 24%-51%, respectively), and these became comparable to those of experienced operators using still images. The interoperator standard errors of the measurement dropped by 42% to 53%, whereas the limits of agreement dropped by 27% to 40%. No substantial changes were noted in the tibialis anterior across reliability metrics.Conclusions-Improved protocols that take advantage of using internal bony landmarks and cine loops during both the image-gathering and measurement processes improve the reliability of research examining muscle size changes in the lower leg or foot associated with muscle changes due to exercise, injury, disuse, or disease.

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

“…Two US images were taken on 10 muscles of the lower leg and foot by a single experienced researcher, with over 10 years of US imaging experience and an established reliability of 0.99 [24]. US images were collected using a GE Logiq s8 with a 6-15 Hz multilinear probe (most images collected at 10-12 Hz).…”

“…We chose a simpler thickness measurement at a uniform distance from the sesamoid bone of the hallux. The use of internal landmarks has been shown to increase accuracy of CSA measurements in comparison to measuring the thickest part of the muscle [19,24]; therefore, future studies should consider new methodology incorporating internal landmarks with a CSA measurement to increase accuracy and account for different foot lengths if possible. Second, the decreased quality and atrophied nature of many muscles in the individuals with DPN made determination of muscle borders more challenging than for CON.…”

“…The standard for this imaging has been MRI in the past, but ultrasound (US) imaging is less expensive, easier, and faster than MRI [8,21,22] and has been used for multiple other pathologies [12,19,23]. While image quality is typically higher in MRI, US also has the advantage of capturing muscle contractions using cine-loops, which can help distinguish difficult muscle-fascial borders [24]. The analysis of individual lower limb muscles using US in DPN could be proved useful in monitoring atrophy and motor nerve degeneration.…”

Ultrasound Imaging Is Reliable for Tibialis Posterior Size Measurements

“…We previously used US to measure the thickness of the TP from an anterior position at 30% of the distance between the knee joint line and lateral malleolus (shank length). 25 We also applied the same procedure to track TP changes throughout an 8-week intervention. 20 Although the CSA may better represent muscle size, we previously focused on thickness based on instrumentation limitations.…”

“…27 We previously measured the TP at 30% of the shank length because its muscle belly is proximal to the other muscles of that compartment. 25 The purpose of this study was to establish a reliable technique to assess the TP CSA using US. Specifically, we evaluated 4 measurement locations: anterior and posterior views at both 30% and 50% of the shank length.…”