title: T2 * MR relaxometry and ligament volume are associated with the structural properties of the healing ACL.
abstract: Our objective was to develop a non-invasive magnetic resonance (MR) method to predict the structural properties of a healing anterior cruciate ligament (ACL) using volume and T2 * relaxation time. We also compared our T2 *-based structural property prediction model to a previous model utilizing signal intensity, an acquisition-dependent variable. Surgical ACL transection followed by no treatment (i.e., natural healing) or bio-enhanced ACL repair was performed in a porcine model. After 52 weeks of healing, high-resolution MR images of the ACL tissue were collected. From these images, ligament volumes and T2 * maps were established. The structural properties of the ligaments were determined via tensile testing. Using the T2 * histogram profile, each ligament voxel was binned based on its T2 * value into four discrete tissue sub-volumes defined by specific T2 * intervals. The linear combination of the ligament sub-volumes binned by T2 * value significantly predicted maximum load, yield load, and linear stiffness (R(2)  = 0.92, 0.82, 0.88; p < 0.001) and were similar to the previous signal intensity based method. In conclusion, the T2 * technique offers a highly predictive methodology that is a first step towards the development of a method that can be used to assess ligament healing across scanners, studies, and institutions.
authors: Department of Orthopaedics, Warren Alpert Medical School, Brown University/Rhode Island Hospital, Providence, Rhode Island.
authors: Alison M
authors: AM
authors: Biercevicz
authors: Martha M
authors: MM
authors: Murray
authors: Edward G
authors: EG
authors: Walsh
authors: Danny L
authors: DL
authors: Miranda
authors: Jason T
authors: JT
authors: Machan
authors: Braden C
authors: BC
authors: Fleming
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000503:physiopathology*; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D007718:Knee Injuries / Q000503:physiopathology* / Q000601:surgery; D007719:Knee Joint / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008962:Models, Theoretical; D013552:Swine; D013556:Swine, Miniature
keywords: ACL; MRI; biomechanics; ligament healing; structural properties