Influence of tear size on the load bearing capacity of the supraspinatus tendon

Supraspinatus tendon tearing is one of the most common injuries of the rotator cuff. This study aims to evaluate the effect of a full-thickness tear on the load bearing capacity of the supraspinatus tendon and to estimate the tear size at which the tendon cannot withstand physiological load. This study introduces a single value parameter, Strength Index (SI), which was estimated from a numerical model of the tendon with an increasing tear size. Critical Tear Size (CTS), defined as the tear size at which the tendon is unable to withstand maximal physiological load, was also estimated. SI and CTS were estimated for eight tear sizes and seven ultimate stresses to account for tear progression and patient variability, respectively. The SI of the modeled tendon decreased with larger tear sizes. The effect of tendon ultimate stress on failure force decreased as the tear size increased. The CTS for the modeled tendon was estimated to be between 6 and 19 mm, assuming an ultimate stress ranging from 1.6 to 12.6 MPa. The potential clinical applicability of CTS is limited to new techniques that allow for accurate estimation of the tissue ultimate stress.