Tissue response to a braided poly-L-lactide implant in an experimental reconstruction of anterior cruciate ligament

During follow-up periods of 6, 12, 24 and 48 weeks, the tissue response to a braided poly-L-lactide (PLLA) implant, 3.2 mm in diameter, was investigated in the reconstruction of experimental anterior cruciate ligament (ACL) ruptures in 32 sheep. In 16 sheep the cut ACL was removed and reconstructed with the fascia lata augmented with a PLLA implant. In 16 sheep the ACL was cut from its midportion, sutured, and thereafter augmented with a PLLA implant. The tissue reactions were typical of a scant non-specific-foreign-body reaction. The number of inflammatory and giant cells was greatest at six weeks, decreasing thereafter. Degradation of the PLLA was incomplete at 48 weeks. No signs of synovitis or changes in the cartilaginous surfaces were observed. The reconstructions in both groups were anchored to the bone by fibroconnective tissue, and remodelling of the bone was seen along the drill channels. After 48 weeks the maturation of the fibroconnective tissue and the orientation of the collagen fibres were higher (p<0.01) in the fascia-lata-PLLA group than in the primarysuture-PLLA group. Histologically, the braided PLLA implants proved to be suitable for ACL repair in sheep. The augmentation of the fascia lata with the PLLA implant seemed to be preferable to that of the primary suture of the ACL.