An in Vitro Study of the Structural Properties of Deep-Frozen Versus Freeze-dried, Ethylene Oxide-Sterilized Canine Anterior Cruciate Ligament Bone-Ligament-Bone Preparations

The effect of two preparation and storage methods on the structural properties of canine anterior cruciate ligament (ACL) bone-ligament-bone preparations was determined. In Group 1, one knee joint from each dog was tested after storage at -70 degrees for eight to 12 weeks. In Group 2, one knee joint from each dog was sterilized using ethylene oxide, freeze-dried, and then stored at room temperature for four to five weeks prior to mechanical testing. In both groups, the contralateral joint was tested fresh and used as a control. The bone-ligament-bone preparations were loaded in tension until failure and the load at failure, stiffness, and maximum elongation were measured. No preparation method caused a significant decline in breaking strength. In both groups, however, there was a significant increase in elongation at failure noted in the test specimens. This was accompanied, in Group 1 (deep-frozen), by a significant decrease in stiffness in the test joints. A similar trend toward decreased stiffness was observed in the test joints from Group 2 (freeze-dried).