Outcomes and clinical role of osteochondral allograft transplantation

© Annals of Joint. All rights reserved. Ann Joint 2017;2:20 aoj.amegroups.com Full-thickness articular cartilage defects of the knee are a significant cause of patient morbidity. As treatment options have expanded, existing treatment algorithms have become increasingly complex (1,2). Osteochondral allograft and autograft transplantation (in this article, OAT refers exclusively to osteochondral allograft transplantation) have received increasing attention for the treatment of full-thickness cartilage defects since their initial study (3-5). Osteochondral allograft transplantations (OATs) are typically reserved for lesions greater than 2 cm, and commonly with subchondral plate or bone involvement. As surgical techniques and indications have improved, OAT studies have increasingly focused on patient outcomes (6,7). In the current study, Frank et al. report on outcomes and failures of 180 patients receiving OAT at a highvolume cartilage restoration center with a mean 5-year follow-up. The failure rate is an encouragingly low 13% at a mean time to failure of 3.6 years (SD 2.6). This mean time to failure highlights the importance of adequate length of follow-up for studies reporting on failure rates for this technique. Failure in this study was defined as revision OAT, conversion to arthroplasty, or graft failure at second-look arthroscopy by gross visual appearance. In general, according to a 2013 systematic review of 19 studies evaluating clinical outcomes of OAT, overall failure rates are reported to be 18% (8). However, no specific set of criteria to define OAT failures exist and this makes direct comparisons among retrospective outcomes studies of such procedures challenging. The results of this study also add to the growing body of medical literature indicating that OAT should not be viewed simply as a revision cartilage procedure or “lastditch” technique for large (>2 cm), full-thickness cartilage lesions. For instance, one study in which OAT was used as the primary and initial treatment reports a continued OAT survivorship of 89.5% at 5 years and 74.7% at 10 years, indicating its use as the index treatment procedure may be appropriate (9). Others have shown that previous subchondral marrow stimulation techniques do not affect the outcomes of OAT when comparing patients who received marrow stimulating techniques prior to OAT with patients who did not (10). This study further demonstrates that previous cartilage repair surgeries do not affect primary OAT outcomes, in comparison to ACI, in which previous marrow stimulation prior to ACI results in increased failure rates (11,12). Regardless of a prior knee surgery’s effect on OAT outcomes, many other advantages of OAT exist, including the ability to perform a single stage procedure and the restoration of a type II hyaline cartilage matrix that is physiologically more similar to native cartilage than fibrocartilage produced by microfracture (13). Furthermore, as the authors of Frank et al. point out, OAT has the advantage of addressing the osseous injury component Editorial