Relationship between meniscal extrusion and various clinical findings after meniscus allograft transplantation.

Background: Meniscus allograft transplantation (MAT) is useful for meniscus-deficient knees. Although meniscal extrusion is common after MAT, there is no consensus regarding the criteria for normal meniscal extrusion or the relationship between clinical and radiologic results.
Hypothesis: Meniscal extrusion after MAT results in poor clinical, radiologic, and arthroscopic outcomes.
Study Design: Case series; Level of evidence, 4.
Methods: Thirty-six of 60 patients undergoing MAT from September 2002 to June 2007 who were available for follow-up evaluation for more than 2 years were evaluated. The study population (31 men, 5 women) consisted of 15 and 21 cases of medial and lateral meniscus transplant, respectively. Knee status was evaluated by Lysholm score, plain radiography, and magnetic resonance imaging preoperatively and postoperatively. Second-look examinations were performed in 18 cases.
Results: Mean follow-up was 31.4 months (range, 24-36). Lysholm knee score increased significantly (mean, 88.2; range, 70-100) on final visit versus the preoperative value (mean, 61.2; range, 26-83; P < .001). Joint-space narrowing was 0.08 mm (range, -2.58 to 1.92) in extension AP and -0.09 mm (range, -2.3 to 1.8) in Rosenberg view. Kellgren-Lawrence arthrosis grade did not change in 28 knees (77.8%) and progressed by 1 grade in 8 knees. Meniscal extrusion extent was 3.87 ± 1.94 mm and relative percentage extrusion was 42.1% ± 17.7%. Seven cases (19.4%) showed minor extrusion (<3 mm), 27 (75%) showed major extrusion (>3 mm), and 2 (5.6%) showed no extrusion. Further degeneration was absent in 28 knees (77.8%) on magnetic resonance imaging. In second-look arthroscopic examinations at an average of 26.3 months, 11 of 18 (63.6%) cases showed no progression of cartilage degeneration. There was no significant correlation between meniscal extrusion and other parameters.
Conclusion: This study indicated that MAT can improve the clinical status of the meniscectomized knee. Although meniscal extrusion occurred after surgery in most cases, there was no significant correlation with various clinical, radiologic, or arthroscopic outcomes. Further studies are required to evaluate long-term effects of meniscal extrusion.