Osteochondral Allograft Transplantation for Focal Cartilage Defects of the Femoral Condyles.

Focal cartilage defects of the knee are painful and difficult to treat, especially in younger patients¹. Seen in up to 60% of patients who undergo knee arthroscopy², chondral lesions are most common on the patella and medial femoral condyle³. Although the majority of lesions are asymptomatic, a variety of treatment options exist for those that are symptomatic; however, no clear gold-standard treatment has been established. In recent years, osteochondral allograft transplantation has been increasingly utilized because of its versatility and encouraging outcomes^4-7. The procedure entails replacing damaged cartilage with a graft of subchondral bone and cartilage from a deceased donor. Indications for this procedure include a symptomatic, full-thickness osteochondral defect typically ≥2 cm² in size in someone who has failed conservative management. Relative indications include patient age of <40 years and a unipolar defect^8,9.

Description: Osteochondral allograft transplantation requires meticulous planning, beginning with preoperative radiographs to evaluate the patient's alignment, estimate the lesion size, and aid in matching of a donor femoral condyle. The procedure begins with the patient supine and the knee flexed. A standard arthrotomy incision is performed on the operative side. Once exposure is obtained, a bore is utilized to remove host tissue from the lesion typically to a depth of 5 to 8 mm. Measurements are taken and the donor condyle is appropriately sized to match. A coring reamer is utilized to create the plug from donor tissue, which is trimmed to the corresponding depth. After marrow elements are removed via pulse lavage, the allograft plug is placed within the femoral condyle lesion through minimal force.

Alternatives: Nonoperative treatment involves a reduction in high-impact activities and physical therapy. Surgical alternatives include chondroplasty, microfracture, and osteochondral autograft transplantation; however, these options are typically performed for smaller lesions (<2 cm). For larger lesions (≥2 cm), matrix-induced autologous chondrocyte implantation (MACI) can be utilized, but requires 2 surgical procedures.

Rationale: Osteochondral allograft transplantation is selected against other procedures for various reasons related to patient goals, preferences, and expectations. Typically, this procedure is favored over microfracture or autograft transplantation when the patient has a large lesion. Allograft transplantation might be favored over MACI because of patient preference for a single surgical procedure instead of 2.

Expected outcomes: To our knowledge, there are currently no Level-I or II trials comparing osteochondral allograft transplantation against other treatments for cartilage defects. There are, however, many systematic reviews of case studies and cohorts that report on outcomes. A 2016 review of 291 patients showed significantly improved patient-reported outcomes at a mean follow-up of 12.3 years^5,9. The mean survival of grafts was 94% at 5 years and 84% at 10 years⁵. Overall, data on long-term survival are lacking because interest in and use of this procedure have only increased over the past few decades¹⁰. Finally, the rate of return to sport is promising, with the systematic review by Campbell et al. showing rates as high as 88% with an average time to return to sport of 9.6 months¹¹. Postoperatively, patients can expect to immediately begin passive range of motion. Progression of heel-touch weight-bearing begins at 6 weeks, and patients may return to sport-specific activity after 8 months, as tolerated.

Important tips: Ensure that the allograft is of adequate quality and is size-matched prior to performing the surgical procedure.The cannulated cylinder should be perpendicular to both the host lesion and graft tissue in order to ensure symmetric estimations of size.Save subchondral bone shavings when preparing the host lesion. These can be utilized to take up space if your graft depth is not sufficient to fill the host defect.Utilize saline solution irrigation judiciously when reaming out the host tissue and graft plug.

Acronyms & abbreviations: AAROM = active-assisted range of motionACI = autologous chondrocyte implantationAP = anteroposteriorBMI = body mass indexCPM = continuous passive range of motionGlut/glutes = gluteal musclesHTO = high tibial osteotomyICRS = International Cartilage Repair SocietyLFC = lateral femoral condyleLTP = lateral tibial plateauMACI = matrix-induced autologous chondrocyte implantationMFC = medial femoral condyleMobs = mobilizationMRI = magnetic resonance imagingNSAIDs = non-steroidal anti-inflammatory drugsOAT = osteochondral allograft transplantationPROM = passive range of motionQuad = quadriceps musclesROM = range of motionSLR = straight leg raise.