A comparative study of single- and double-bundle ACL reconstructions in sheep.

Work in vitro has previously shown superior restoration of knee stability using a double-bundle anterior cruciate ligament (ACL) reconstruction compared with single bundles taken through the condyle or 'over the top'. This paper describes an animal study designed to compare the three ACL reconstructions in vivo, in order to collect data that could support the clinical use of a double-bundle reconstruction. The three methods were compared in three groups of eight sheep, the ovine ACL having a distinct double-bundle structure. Biomechanically matched polyester fibre implants were used, with 6 months in vivo. The three methods led to similar intra-articular fibrous tissue integration of the implants and no evidence of implant damage, and biomechanical testing found greater laxity than normal for all three groups. The double-bundle group, however, had more joint surface degeneration than the other groups. It was concluded that clinical use of the double-bundle reconstruction was not indicated by the results of this experiment, in view of the more complex surgery and lack of superior performance.