Adductor longus: An anatomical study to better understand groin pain

Abstract

We investigated the shear modulus-passive force relationship in the hip adductor longus (AL) muscles of human cadavers and explored the effect of muscle architecture on the elastic properties of the AL muscle using shear wave elastography (SWE).Nine AL muscles were harvested from a soft, embalmed cadaver. The AL muscles were affixed to a custom-built device comprising two clamps, a pulley, and a cable to provide passive loads, which were increased from 0 to 600 g in 60-g increments. The shear modulus of the AL muscle was measured in the proximal (Pro), middle (Mid), and distal (Dis) regions. The masses and anatomical cross-sectional areas (ACSAs) of the AL muscles were measured. The shear modulus-passive load relationship of each tested muscle region was analyzed by fitting a least-squares regression line. Moreover, the rate of increase in the shear modulus per unit load (s) was calculated. The shear modulus and passive force were linearly correlated for all AL muscles in each region (p < 0.01). The mean coefficients of determination (R 2 ) for Pro, Mid, and Dis were 0.989, 0.986, and 0.982, respectively. The rate of increase in the shear modulus per unit load significantly correlated with the reciprocal of the muscle mass (r = 0.77, p = 0.02) and ACSA (r = 0.43, p = 0.03). Shear wave elastography can be used as an indirect measure of passive force in any region of the AL muscle. Additionally, the rate of increase in the shear modulus per unit load could be associated with muscle architectural parameters.

Quantifying the shear modulus of the adductor longus muscle during hip joint motion using shear wave elastography

“…This study demonstrated that the shear modulus of the AL muscle increases through hip abduction, extension, and internal rotation. We have already demonstrated a strongly linear relationship between the shear modulus and passive force in the AL muscle 16 . Therefore, the results of the present study indicate that the passive force of the AL muscle can be increased by hip abduction, extension, and internal rotation.…”

“…In this study, it was unclear whether the AL muscle had a hip internal or external rotation moment arm because the hip rotation moment arm of each subject was not measured. However, a previous study showed a strong linear relationship between the shear modulus of the AL muscle and the passive force 16 . At 20° hip extension, therefore, there might be a passive force in the AL muscle due to the stretching of the AL muscle by hip internal rotation.…”

“…The shear modulus of the AL muscle measured by SWE during elongation has a strong linear relationship with the passive force 16 . Similarly, previous studies have reported that this relationship is strongly linear in animal muscles 23 , 25 and the human rectus femoris muscle 22 .…”

“…Previous studies demonstrated that the strong linear relationship between the passive force and shear modulus imaged in the long axis indicates that the probe position is parallel to the muscle; however, no such relationship existed between the passive force and shear modulus imaged in the short axis, indicating that the probe position is transverse to the muscle 22 , 23 . Moreover, our previous study demonstrated that the shear modulus of the AL muscle measured along the long axis was strongly linear (R 2 = 0.98–0.99) 16 . Therefore, the probe was set along the long axis of the AL muscle.…”

“…Shear wave elastography (SWE) can quantify individual muscle tissue stiffness by measuring the muscle shear modulus, and it is used as a tool for indirect measurement of the mechanical properties of skeletal muscle, such as passive force 13 , 15 . We examined the shear modulus–passive force relationship in the AL muscle using SWE and demonstrated a strong linear relationship in each region of the AL muscle 16 . This result indicates that SWE can be used as an indirect measure of the passive force of the AL muscle.…”