Osteochondral Plug Transfers—Do They Survive?

Abstract & Commentary

Synopsis: Biopsies of transplanted autologous osteochondral plugs revealed viable articular cartilage and bone in every case.

Source: Barber FA, Chow JC. Arthroscopic osteochondral transplantation: Histologic results. Arthroscopy. 2001;17(8): 832-835.

Treatment of full thickness articular cartilage lesions remains a challenging clinical problem despite expanding research and emerging technologies. Osteochondral plug transfer, also referred to by commercial names including OATS, COR, and Mosaicplasty, has rapidly gained acceptance in part because it can be performed arthroscopically in 1 stage. Unfortunately, few studies document clinical effectiveness in a prospective, controlled fashion. The same can be said for the other emerging treatment options for cartilage injury. An even larger shortcoming of the literature in this area is the lack of clinical studies with second-look arthroscopies and biopsies to evaluate the tissue that fills the defect.

Barber and Chow provide a welcome addition to the literature with this nonrandomized, longitudinal, cohort study. Patients initially underwent osteochondral grafting with 1 to 3 plugs for defects measuring between 1 and 3.5 cm in diameter. All plugs were taken from the lateral and superior intercondylar notch. Drilling was used to prepare the recipient site. The study group consisted of 10 patients who underwent osteochondral plug transfer and required later surgery due to "clinical symptoms" or to debride scar tissue following ACL reconstruction. How these patients were selected and indications for this second surgery were not altogether clear from the methods. All 10 had arthroscopy at variable intervals ranging from 2 to 12 months, and 7 agreed to biopsy with a bone biopsy needle from the center of one of the plugs. Biopsies were stained with H&E and assessed for cell viability, healing, and tissue integrity. At all time points, the chondrocytes and osteocytes were alive and well, and the tissue appeared normal in its organization. The bone appeared to have healed with creeping substitution, remodeling, and preservation of the tidemark. No complications with dislodging of the plugs, loose body formation, or damage to surrounding cartilage occurred.

Comment by David R. Diduch, MS, MD

It is truly amazing how orthopaedic surgeons have embraced new techniques for treating articular cartilage defects despite the paucity of good scientific or longitudinal clinical studies, and the lack of studies with second look biopsies to critically evaluate the repair. Although the numbers are small, the follow-up short, and the inclusion criteria vague, this is a welcome study to confirm what most of us suspected. If you transfer healthy articular cartilage with its bony attachment, it will survive. These biopsies document that the osteochondral plug heals, the cells survive, and no mechanical disruption occurs through 12 months. Even the spaces between the plugs, shielded from shear forces by the plugs and adjacent cartilage, filled in with fibrocartilage-like grout. Unfortunately, no biopsies were obtained from these areas. Even the donor areas predictably filled in with bone and a fibrocartilage cap that was flush with surrounding cartilage. Given that the donor areas are small and somewhat shielded from shear by adjacent normal cartilage, this fibrocartilage may do well, but we really don’t know without more studies with second look arthroscopies and biopsies over the long term.

Osteochondral plug transfer is an established procedure now in orthopaedics that many of us do, including myself. What we need are more studies to validate this. There is a move afoot to label this procedure "experimental." No! This would kill it. No one would get paid, including the surgical center for the harvesters. Of all of the emerging technologies, this is probably the most straightforward in terms of knowing what you get in the defect. This study is a major addition to validate the procedure and objectively confirm the hyaline nature of the tissue and that the plugs survive. The limiting factor remains, as always, the availability of donor tissue. This confirms once again the age old axiom well established in sports (medicine), that size does matter.

Dr. Diduch, Associate Professor, Department of Orthopaedic Surgery, University of Virginia School of Medicine, Charlottesville, is Editor of Sports Medicine Reports.