Overview

About this study

Aim 1 of this project will be entirely cadaveric and, thus, classified as not-human-subjects research by the Mayo Clinic IRB. Eight fresh-frozen cadaveric lower extremities (no history of knee trauma; < 50 years of age) will be acquired from a vendor that has provided >50 specimens with similar criteria in the past three years.5 Specimens will be thawed 24 hours prior to testing. 3D musculoskeletal (MSK) US images of the ACL in the intact knee will be acquired with an Aixplorer Mach 30 (SuperSonic Imagine, Bothell, WA). Literature described imaging techniques from both the anterior and posterior aspect of the knee will be used. SWE stiffness of the ACL will be calculated from the obtained images for cross-correlation against mechanical failure properties. Once images have been collected, each specimen will be resected such that the bone-ACL-bone complex remains intact. These complexes will be individually secured into custom mechanical fixtures and placed into a uniaxial hydraulic tensioner (MTS Systems, Eden Prairie, MN). Each structure will be exposed to 50 stress/relaxation cycles that vary ligament tension from 0-3% to remove viscoelastic effects. Specimens will then be tensioned at 20%/sec until failure is achieved. During tensioning, the hydraulic tensioner will measure displacement and a uniaxial load cell mounted to the tensioner will record linear force enacted on the tissue. ACL strain will be calculated as the linear displacement divided by the neutral ligament length (longest distance between ACL origin and insertion where the load cell registers 0 N force). Linear regression models will determine the significance of association between failure properties (ultimate strain, stress, and tensile strength) and US stiffness.

            For Aim 2, 40 total lower extremities will be recruited for 3D US imaging of the ACL at their pre-surgical clinical visit. This will include the injured limb from 20 pre-surgical patients with an MRI-confirmed ACL rupture and 20 healthy control limbs with no documented history of injury or scheduled surgery. Subjects recruited for the injured limb cohort may be dual-recruited as controls so long as their contralateral limb satisfies the inclusion criteria. US images will be acquired from both the anterior and posterior aspect of each knee. Injured versus control status will be documented by the collecting research team member. These images will be assessed and descriptively categorized by a separate, blinded, experienced rater for tear presence, location, severity, and type. For injured limbs, the clinical MRI for each subject will be acquired and similarly categorized. For healthy limbs, a research MRI will be scheduled and similarly categorized. Chi-Square test of independence will be used to assess statistical correlation between the US and MRI image classification. Receiver operator curves will be used to assess sensitivity and specificity of US and MRI diagnoses of ACL injuries against known clinical conditions.

Participation eligibility

Participant eligibility includes age, gender, type and stage of disease, and previous treatments or health concerns. Guidelines differ from study to study, and identify who can or cannot participate. There is no guarantee that every individual who qualifies and wants to participate in a trial will be enrolled. Contact the study team to discuss study eligibility and potential participation.

Participating Mayo Clinic locations

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