Histological Evaluation of Harvested Specimen of a Patient Who Underwent Unicompartmental Knee Arthroplasty Two Years and Six Months After Medial Meniscus Posterior Root Tear Transtibial Pull-Out Repair.

Transtibial pull-out repair is routinely performed to treat medial meniscal posterior root tear (MMPRT). However, data on the postoperative histological evaluation of the repaired medial meniscus posterior attachment after the procedure is scarce. In this report, we present a histological evaluation of the harvested specimen of a patient who underwent unicompartmental knee arthroplasty (UKA) approximately two years and six months after MMPRT transtibial pull-out repair. The patient was a 75-year-old female. Her X-ray showed Kellgren-Lawrence classification grade II and her MRI revealed MMPRT. Arthroscopic transtibial pull-out repair was performed two months after the onset, and her condition was fine two years after the operation. However, her knee pain gradually worsened, and UKA was performed two years and six months after the initial surgery. The medial meniscus posterior root was continuous from the resected tibia. Tissue specimens were prepared and evaluated. There were Sharpey's fiber-like tissues in the tibial bone tunnel. The medial meniscus posterior attachment showed a four-layer structure of ligaments, uncalcified fibrocartilage, calcified fibrocartilage, and subchondral bone zone. The structures were observed 2,000 ㎛ medially from the bone tunnel. The results revealed that the reconstructed graft after a transtibial pull-out repair for the medial meniscus posterior root showed different histological findings compared with the native posterior root and similar to the anterior root of the medial meniscus.