Biomechanical Properties and Vascularity of an Anterior Cruciate Ligament Graft can be Predicted by Contrast-Enhanced Magnetic Resonance Imaging A Two-Year Study in Sheep

• Published in: American journal of sports medicine Vol. 29; no. 6; pp. 751 - 761
• Main Authors: Weiler, Andreas, Peters, Gunnar, Mäurer, Jürgen, Unterhauser, Frank N., Südkamp, Norbert P.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Los Angeles, CA SAGE Publications 01-11-2001; American Orthopaedic Society for Sports Medicine; Sage Publications, Inc; Sage Publications Ltd
• Subjects: Animals; Anterior cruciate ligament; Anterior Cruciate Ligament - blood supply; Anterior Cruciate Ligament - surgery; Anterior Cruciate Ligament Injuries; Biological and medical sciences; Biomechanical Phenomena; Female; Hindlimb - surgery; Image Enhancement; Injuries; Investigative techniques, diagnostic techniques (general aspects); Knee; Ligaments; Magnetic Resonance Imaging; Medical sciences; Models, Animal; NMR; Nuclear magnetic resonance; Osteoarticular system. Muscles; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Sheep; Skin & tissue grafts; Sports injuries; Sports medicine; Surgery; Tensile Strength; United States; Knee; Diseases of the osteoarticular system; Homograft; Lower limb; Mechanical properties; Experimental study; Trauma; Nuclear magnetic resonance imaging; Anterior cruciate ligament; Vascularization; Vertebrata; Ewe; Mammalia; Treatment; Surgery; Animal; Tissue rupture; Graft; Medical imagery; Sheep; Artiodactyla; Predictive factor; Ungulata; Tendon
• DOI: 10.1177/03635465010290061401
• EISSN: 1552-3365
• ISSN: 0363-5465

Magnetic resonance imaging has been used to determine graft integrity and study the remodeling process of anterior cruciate ligament grafts morphologically in humans. The goal of the present study was to compare graft signal intensity and morphologic characteristics on magnetic resonance imaging with biomechanical and histologic parameters in a long-term animal model. Thirty sheep underwent anterior cruciate ligament reconstruction with an autologous Achilles tendon split graft and were sacrificed after 6, 12, 24, 52, or 104 weeks. Before sacrifice, all animals underwent plain and contrast-enhanced (gadolinium-diethylenetriamine pentacetic acid) magnetic resonance imaging (1.5 T, proton density weighted, 2-mm sections) of their operated knees. The signal/noise quotient was calculated and data were correlated to the maximum load to failure, tensile strength, and stiffness of the grafts. The vascularity of the grafts was determined immunohistochemically by staining for endothelial cells (factor VIII). We found that high signal intensity on magnetic resonance imaging reflects a decrease of mechanical properties of the graft during early remodeling. Correlation analyses revealed significant negative linear correlations between the signal/noise quotient and the load to failure, stiffness, and tensile strength. In general, correlations for contrast-enhanced measurements of signal intensity were stronger than those for plain magnetic resonance imaging. Immunohistochemistry confirmed that contrast medium enhancement reflects the vascular status of the graft tissue during remodeling. We conclude that quantitatively determined magnetic resonance imaging signal intensity may be a useful tool for following the graft remodeling process in a noninvasive manner.