Extrusions do not affect degenerative morphologic changes in lateral meniscus allografts during midterm follow-ups.

Purpose: To investigate degenerative morphological changes in meniscus allograft after lateral meniscus allograft transplantation (MAT) based on extrusions.
Methods: Ninety-one patients who underwent lateral MAT were divided into extruded and non-extruded groups. Serial magnetic resonance imaging scans obtained 6 weeks, 1 year, and at the last follow-up (midterm, 3-7 years) post-surgery were evaluated retrospectively. Degenerative morphological changes at each time point in each group were compared using the postoperative meniscal width, thickness, and intrameniscal signal intensity (IMSI) at the anterior horn, mid-body, and posterior horn. The Lysholm scores and meniscal tears based on graft extrusion were also investigated.
Results: The mean age was 33.7 ± 11.1 years (64 men and 27 women). Fifty-three (58%) and 38 knees (42%) were classified into the non-extruded and extruded groups, respectively. The overall meniscal width of the mid-body decreased from 9.6 ± 1.3 to 6.5 ± 1.2 mm (p < 0.01), and IMSI of mid-body was increased from 1.2 ± 0.1 to 1.7 ± 0.1 (p < 0.01) during midterm follow-ups. No significant differences were observed between the meniscal width, thickness, and IMSI at the anterior horn (n.s.), mid-body (n.s.), and posterior horn (n.s.) of the two groups during the midterm follow-ups. The incidence of meniscus tears and Lysholm scores did not differ significantly between the groups during midterm follow-ups.
Conclusion: The overall meniscus width of mid-body decreased while the relative IMSI of mid-body increased during midterm follow-ups after lateral MAT. Meniscal allograft extrusions did not influence postoperative changes in meniscus width, thickness, and relative intrameniscal signal intensity.
Level of Evidence: Level III.