Although shear wave elastography (SWE) has been used to indirectly measure passive force in muscle tissues, it is unknown whether SWE can be utilized to evaluate passive force in capsule tissues. This study investigated the relationship between the shear elastic modulus and passive force in posteroinferior shoulder capsules using SWE. Six posteroinferior shoulder capsules were dissected from six fresh-frozen cadavers; then, humeral head–capsule–glenoid specimens were created from each capsule. The humeral head and glenoid were each immobilized with clamps of a custom-built device. Passive force (0-400 g in 25 g increments) was applied to each capsule via a pulley system, and elasticity was measured simultaneously using SWE. Our data revealed that the relationship between the shear elastic modulus and passive capsule force was highly linear for all six tested capsules (p < 0.01). The mean (± standard deviation) coefficient of determination was 0.933 (±0.030; range 0.883 and 0.963). Our study demonstrated that SWE is a valid and useful method for indirectly and noninvasively evaluating the passive force of the posteroinferior shoulder capsule.
