Muscle and Tendon Stiffness of the Lower Limb of Professional Adolescent Soccer Athletes Measured Using Shear Wave Elastography

Abstract

Background: While adolescents have specific risk factors for acute and chronic injury, there is a lack of preventive medicine algorithms for this vulnerable group. Shear wave elastography (SWE) is currently mainly used for assessing muscle and tendon stiffness in adult athletes and can diagnose tissue pathologies such as tendinopathy. The aim was to investigate differences in quadriceps tendon and muscle stiffness between adolescent and adult professional soccer players using SWE and identify lateral imbalances in order to improve the knowledge of preventive medicine algorithms for professional adolescent athletes.

Methods: Standardized SWE examinations of both lower limb tendons and muscles (the quadriceps tendon (QT) and the vastus medialis (VM) muscle) in the longitudinal plane and relaxed tendon position were performed in 13 healthy adolescent soccer athletes (13-17 years), and a control group of 19 healthy adult professional soccer athletes (18-29 years).

Results: Adolescent soccer players had lower stiffness values for both the quadriceps tendon (3.11 m/s vs. 3.25 m/s) and the vastus medialis muscle (1.67 m/s vs. 1.71 m/s) than adult athletes. Moreover, QT stiffness in adolescent soccer players was significantly lower on the right side (QT: adult 3.50 m/s (2.73-4.56) vs. adolescent 2.90 m/s (2.61-3.12); p = 0.031). Analysis of the lateral differences revealed softer QT and VM tissue on the right side in over two-thirds of adolescent soccer athletes. Over two-thirds of adults had stiffer QT and VM tissue on the right side.

Conclusion: In adolescent soccer players, the stiffness of the QT and VM muscle measured by SWE is lower in the right leg. SWE of the musculoskeletal system may thus become a relevant diagnostic tool to detect early lateral imbalances as a main risk factor for injury and may thus contribute to the prevention of acute and chronic injury prevention in adolescent athletes.

Keywords: SWE; adolescence; muscle; shear wave elastography; soccer; tendon; ultrasound.

Figure 1

Probe placement and target volume: for SWE, a multifrequency linear transducer was placed in longitudinal plane for accurate assessment of the quadriceps tendon (QT; (A,B)) and with minimal movement to assess the medial vastus muscle (VM; (C,D)).

Figure 2

Shear wave elastography of the quadriceps tendon (A,B) and medial vastus muscle (C,D) with color-coded map (A,C) and assessment of shear wave speed using three ROI-measurements per image (B,D). The color scale on the left side of each image can be used for interpretation of the shear wave speed, ranging from minimum 0 m/s (e.g., very soft = blue) to a maximum of 15 m/s (e.g., red = stiff). In this example, the tendon stiffness is visualized green (resulting in a moderate stiffness around 2–3.5 m/s; Figure 1A,B), while the softer muscle tissue ranged around 1 m/s and is therefore visualized as blue (Figure 1C,D).

Figure 3

Boxplots of shear wave speed delta (SWS) for adolescent and adult soccer athletes for right and left quadriceps tendon (QT) and medial vastus muscle (MV).

Figure 4

Exemplary images of the right quadriceps tendon in an adolescent soccer athlete (left) and an adult athlete (right). As depicted by the color-coded map, SWE showed significant higher shear wave velocity in an adult athlete (green, right image) compared to adolescent athlete (left image).