Pearls and Pitfalls in Difficult Patellar Osteochondral Allograft Transplantation.

Background: Osteochondral allograft (OCA) transplantation is a durable option for patients with symptomatic chondral or osteochondral defects involving the patella; however, the unique shape and contour of the patella can make successful OCA transplantation challenging. Indications: Patellar OCA transplantations are indicated in the setting of a symptomatic patellar chondral or osteochondral lesion that has failed conservative management. A concomitant offloading tibial tubercle osteotomy (TTO) may be added depending on the location of the lesion and the posteriorization of the tibial tubercle relative to the trochlea. Technique Description: Donor size and shape-matched patellae should be obtained before the procedure. The patella is exposed via a laterally based arthrotomy, through which a lateral retinacular lengthening is performed. When TTO is indicated, the osteotomy is performed first to facilitate patellar eversion and exposure. The recipient defect is sized and matched to a donor patellar cartilage surface. Using a guide pin, the defect is then scored and reamed using constant cold flow irrigation. The donor cartilage plug is then prepared via cold irrigation reaming, cutting to the proper depth, and lavaging with saline and carbon dioxide gas to remove bone marrow elements and antigenicity. It is then press-fit into the recipient defect location. Results: We represent pearls and pitfalls at all stages during patellar OCA transplantation in the setting of large focal defects in various locations. There has been excellent survivorship of OCA plugs in the patellofemoral joint up to 8 to 10 years, with a significant decrease in survivorship with the use of shell-type OCAs. Discussion/Conclusion: Patellar OCA transplantation is a complex procedure that requires further consideration in cases of incongruent topography of the cartilage surface. Ensuring adequate matching between donor and recipient grafts and implementing steps to optimize integration and graft biology can help achieve optimal outcomes. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.