Review of Arthroscopic and Histological Findings Following Knee Inlay Arthroplasty

The phenomenon of cartilage rim loading in defects exceeding the threshold diameter of 10 mm is well documented. Contoured defect fill off-loads the perimeter and counteracts further delamination and progression of defects. When biological procedures have failed, inlay arthroplasty follows these concepts. The human biological response to contouredmetallic surface implants has not been described. Four patients underwent non-implant-related, second-look arthroscopy following inlay arthroplasty for
bi- (n D 3) and tricompartmental (n D 1) knee arthrosis without subchondral bone collapse. Arthroscopic probing of the implant–cartilage interface of nine prosthetic components did not show signs of implant–cartilage gap formation, loosening, or subsidence. The implant periphery was consistently covered by cartilage confluence leading to a reduction of the original defect size diameter. Femoral condyle cartilage flow appeared to have more hyaline characteristics. Trochlear cartilage flow showed greater histological variability and less organization with fibrocartilage and synovialized scar tissue. This review reconfirmed previous basic science results and demonstrated effective defect fill and rim off-loading with inlay arthroplasty. (Journal of Surgical Orthopaedic Advances 25(1):18–26, 2016) Key words: cartilage flow, cartilage rim stress, inlay arthroplasty