Comparison of Snowman and Single-Plug Circular Osteochondral Allograft Transplantation Techniques for Similarly Sized Defects: A Matched Cohort Analysis

Background: Multiplug “snowman” osteochondral allograft transplantation (OCA) is an effective treatment method for large, irregularly shaped osteochondral defects of the knee. No existing literature directly compares the effectiveness of this technique with traditional single-plug circular OCA. Purpose: To compare failure rates, reoperation rates, and relevant patient-reported outcome (PRO) scores at 2-year follow-up between patients undergoing snowman OCA and patients undergoing single-plug OCA. Study Design: Case series; Level of evidence, 3. Methods: Patients who underwent snowman or single-plug OCA between 2001 and 2021 with a minimum 2-year follow-up were identified. Propensity score matching at 1:2 was performed based on age, sex, body mass index, defect location, and defect size. The PRO measures assessed included the International Knee Documentation Committee subjective score, Lysholm score, Knee Injury and Osteoarthritis Outcome Score, and 12-Item Short Form Health Survey. Failure was defined as conversion to arthroplasty, revision OCA, or graft degeneration on second-look arthroscopic examination. Additionally, rates of achieving the minimal clinically important difference (MCID) or patient acceptable symptom state (PASS) for PRO measures were determined. Results: There were 26 patients (mean age, 33.3 ± 9.3 years; 65.4% male) who underwent snowman OCA with a mean follow-up of 5.8 ± 4.1 years. No significant differences in baseline variables were identified compared with a matched control group of 52 patients who underwent single-plug OCA. No differences were detected in the rate of achieving the MCID or PASS between the groups for any PRO measure. Overall, 5 patients (19.2%) in the snowman group experienced graft failure at a mean 1.7 ± 1.0 years, while 10 patients (19.2%) in the single-plug group met the criteria for failure at a mean 6.6 ± 3.5 years. No differences were detected in the rate of failure or reoperations between the 2 groups. Conclusion: Multiplug “snowman” and single-plug circular OCA techniques yielded comparable clinical outcomes and graft survivorship for defects of a similar size in a matched cohort analysis. Defect shape, rather than size alone, should guide the selection of a technique. The snowman technique is advantageous for longer or oval-shaped defects not easily treated with a single plug, as it minimizes the removal of healthy cartilage while maintaining optimal outcomes.