FUNCTIONAL EVALUATION OF SOFT TISSUE INSERTIONS TO BONE

摘要

Soft tissue insertions into bone are of critical importance in transmitting forces from ligaments and tendons to bone, and thus are crucial in joint stability and musculoskeletal motion. Despite their importance, there exists no established experimental method for rigorously determining their function. Previous studies have established the pull-out test as the standard method of evaluating the mechanical function of soft-tissue insertions, however, as this method tests response at a single orientation it may not capture the overall function of soft-tissue insertions. Previous researchers have noted the effect of alignment on the tensile response of soft tissues. For example, Woo, et al. demonstrated that alterations in alignment of insertions produced significant changes in the measured tensile stiffness and ultimate strength of the human anterior cruciate ligament (ACL). Mommersteeg and co-workers performed sub-failure tensile loadings at various isolated insertion tilts up to a maximum +- 25° in two independent directions (medial/lateral, or anterior/posterior), documenting significant changes in the stiffness of the constructs, but combined tilts (e.g., 5° medial/5° posterior) were not investigated. Complementing these studies, Sakane, et al., demonstrated that the direction of tensile force in the ACL changes under anterior joint loading depending on the angle of knee flexion. This indicates that the contribution of a ligament to a joint (and therefore the function of a ligament insertion) is generally along more than a single axis. We propose that a complete functional evaluation of a soft tissue insertion could be achieved by measuring tensile response over a wide range of angles, and would provide improved characterization of normal tissue insertions. Such an approach could also be used to evaluate current soft tissue fixation techniques, and could further provide structural design parameters needed for the development (and testing/evaluation) of engineered soft tissues and soft tissue insertions.