Arthroscopy: The Journal of Arthroscopic and Related SurgeD' 9(1):82-86 Published by Raven Press, Ltd. © 1993 ArthroscopyAssociation of North America The Induction of IL-1 by Freeze-Dried Ethylene Oxide-Treated Bone-Patellar Tendon-Bone Allograft Wear Particles: An In Vitro Study V. J. Silvaggio, M.D., F. H. Fu, M.D., H. I. Georgescu, B.Sc., and C. H. Evans, Ph.D. Summary: There have been recent reports of adverse clinical results with freeze-dried ethylene oxide-treated bone-patellar tendon-bone (FD-ETO- BPTB) allografts used in anterior cruciate ligament (ACL) reconstruction. Eth- ylene oxide and its residues were implicated as the cause of many of the failures. Wear particles generated from both freeze-dried ethylene oxide- treated and deep frozen bone-patellar tendon-bone (DF-BPTB) allografts were placed in culture with lapine synoviocytes. The resulting synovial- conditioned media were then assayed for interleukin-I (IL-1) content. IL-1 is a potent mediator of tissue inflammation. FD-ETO-BPTB wear particles gener- ated statistically significant levels of IL-1 when compared with both a negative control and DF-BPTB wear particles. Key Words: Ethylene oxide--Inter- leukin-1--Anterior cruciate ligament. The anterior cruciate ligament (ACL) has been well established as a primary stabilizer of the knee. Patients with ACL-deficient knees may suffer symptomatic instability leading to further injury, knee joint degeneration, and functional disability. In this group of patients surgical intervention may be the only option. Surgical reconstruction of the ACL requires the use of autograft, allograft, or synthetic materials. The procedure that has proved most successful uses autogenous bone-patellar tendon-bone or semiten- dinosus with or without gracilis tendon. Concern about donor site morbidity caused surgeons to seek From the Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh School of Medicine, Pittsburgh, Penn- sylvania, U.S.A. Address correspondence and reprint requests to Vincent J. Silvaggio, M.D., at Ferguson Laboratory for Orthopaedic Re- search, University of Pittsburgh School of Medicine, 986 Scaife Hail, Pittsburgh, PA 15261, U.S.A. This article was presented at the ninth annual meeting of the Arthroscopy Association of North America, Orlando, Florida, 1990, and the 37th annual meeting of the Orthopaedic Research Society, Anaheim, California, U.S.A. alternatives to autogenous tissues. As a result, ACL reconstruction with allograft tissue as well as syn- thetic ligaments has been performed. The long-term safety and efficacy of artificial lig- aments has yet to be determined. Many reports in the literature have noted problems with artificial lig- aments. Failure as well as persistent knee effusions requiring ligament removal have been reported (1,2). Allografts offer potential advantages to autog- enous tissues, including unlimited supply in various shapes and sizes, long-term storage capabilities, the possibility of transporting tissues from one center to another, no donor site morbidity, and decreased op- erative time. Two allograft tissues commonly used are deep- frozen bone-patellar tendon-bone (DF-BPTB) and freeze-dried ethylene oxide-treated bone-patellar tendon-bone (FD-ETO-BPTB). There have been recent reports of adverse clinical results with FD- ETO-BPTB allografts (3,4). Ethylene oxide and its residues (ethylene chlorhydrin and ethylene glycol) were implicated as the cause of many of the fail- ures. The exact mechanism of failure has not yet 82