STERILIZATION OF CANINE ANTERIOR CRUCIATE ALLOGRAFTS BY GAMMA-IRRADIATION IN ARGON

Bone-ACL-bone allograft transplantation is a potential solution to the problem of reconstruction of the anterior cruciate ligament (ACL), bu t sterilisation by gamma irradiation or ethylene oxide causes degradat ion of the graft, We have studied the biomechanical and histological p roperties of deep-frozen canine bone-ACL-bone allografts sterilised by gamma irradiation (2.5;Mrad) under argon gas protection, Particular a ttention was paid to their collagen structure and neuroanatomy compare d with those of non-irradiated allografts. We used 60 skeletally matur e foxhounds. In 30 animals one ACL was replaced by an irradiated allog raft and in the other 30 a non-irradiated graft was used. In both grou ps the graft was augmented by a Kennedy Ligament Augmentation Device. Examination of the allografts at 3, 6 and 12 months after implantation included mechanical testing, histology, collagen morphometry, neuroan atomical morphology (silver and gold chloride stain) and studies of th e microvasculature (modified Spalteholz technique). At 12 months the i rradiated ACL allografts failed at a mean mamimum load of 718.3 N, 63. 8% of the strength of the normal canine ACL. The non-irradiated allogr afts failed at 780.1 N, 69.1% of normal. All the allografts showed a w ell-orientated collagen structure one year after transplantation and t here was no difference between the irradiated grafts and the others, T he silver staining technique demonstrated Golgi tendon organs and free nerve endings within both groups of allografts, As in the normal ACL these structures mere most commonly found near the surface of the graf t and at its bony attachments. At 12 months the irradiated allografts showed slight hypervascularity compared with the non-irradiated grafts . We believe that cryopreserved ACL allografts have the potential to r estore both the mechanical and the neurophysiological functions of the normal ACL.