Position of the bony bridge of lateral meniscal transplants can affect meniscal extrusion

Background: There are several reported causes of midbody extrusion after lateral meniscal allograft transplantation. However, there are no reports studying the correlation between the position of the bony bridge and extrusion of the midbody after meniscal allograft transplantation. Hypothesis: The position of the bony bridge of lateral meniscal allografts can affect meniscal extrusion. Study Design: Case series; Level of evidence, 4. Methods: Twenty-three consecutive patients underwent a lateral meniscal allograft transplantation using a fresh-frozen graft. The lateral meniscal allograft was prepared with a bony bridge. Postoperative evaluations of the meniscal allografts were performed using follow-up magnetic resonance imaging 6 months postoperatively. On the coronal view, extrusion was measured as the distance between the outer edge of the articular cartilage of the lateral tibial plateau and the outer edge of the meniscal allograft. On the axial view, the length of the entire tibial plateau (PL) and distance between the lateral edge of the lateral tibial plateau and center of the bony bridge (CB) were measured. Measurements of CB were divided by measurements of PL. The correlation test between CB/PL and extrusion was performed to determine whether the position of the bony bridge can affect extrusion of the midbody of meniscal allograft. Results: The mean center of the bony bridge of the meniscal allograft (CB/PL) was positioned at 42.3% (range, 36.1%-49%; standard deviation [SD] = 3.6%) from the outer edge of the lateral tibial plateau. The mean extrusion of meniscal allografts was 3.2 mm (range, 0-6.5 mm; SD = 2.3). The amount of extrusion was correlated with the position of the bony bridge of the graft and the Pearson correlation coefficient was –.567 ( P = .003). The cut-off percentage above which extrusion did not occur was 42.05%. Conclusion: The more closely the center of the bony bridge approached 50% of the entire tibial plateau, the less extrusion of the midbody occurred. Anatomic placement of the bony bridge of lateral meniscal allograft is imperative to prevent extrusion after lateral meniscal allograft transplantation.