The purpose of this study was to histologically observe a specimen of a calcium phosphate (CaP)-hybridized tendon graft-bone interface at the posterior side of tibial bone tunnel obtained during the revision anterior cruciate ligament (ACL) reconstruction. We present the
case of a 15-year-old female who was returning to sports 7 months and 12 days after primary anatomic single-bundle ACL reconstruction with no instability. Re-rupture was diagnosed 9 months and 12 days after the surgery. At the joint aperture site, a firm biological fixation via direct bonding area, cartilaginous tissue, and dense collagen fiber were observed without the presence of a nonbonding gap area.