Histologic findings with a bioabsorbable anterior cruciate ligament interference screw explant after 2.5 years in vivo.

We retrieved a high-molecular-weight poly-L-lactic) (PLLA) anterior cruciate ligament (ACL) interference screw (Arthrex, Naples, FL) after 30 months in vivo during revision ACL surgery. Gross, histologic, histomorphometric, and molecular weight measurements were carried out on the implant and the surrounding bone. These studies showed a 75% decrease in the molecular weight of the screw, with implant fragmentation and new bone formation adjacent to the screw and graft. Healing of the graft within the bony tunnel with no significant inflammatory reaction had occurred. The clinical implications of these findings are that this implant dissolves slowly, and it was physically present at 30 months in vivo. It is a safe, nonreactive alternative to traditional metal interference screws used for ACL graft fixation. It will eventually be substituted by bone and will eliminate some of the problems associated with metallic devices.