To systematically summarize the medial meniscus allograft transplantation (MAT) reported outcomes and evaluate whether the surgical technique is associated with allograft extrusion and knee function.
In accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a literature review was performed utilizing PubMed, Embase and Cochrane Library databases. Inclusion criteria were English-language clinical studies involving arthroscopically assisted medial MAT that reported the surgical technique as well as the presence of graft extrusion, and/or functional outcomes after surgery. Studies in which the outcomes for medial MAT could not be separated from lateral MAT were excluded. Surgical technique, allograft-related characteristics and clinical outcomes were extracted.
Twenty-five studies were included, the majority of them classified as level of evidence 4 (56%). Of the 335 considered cases of medial MAT, 235 (70.1%) used bone plug technique, 55 (16.4%) bone bridge trough technique, and 45 (13.4%) soft-tissue techniques. Pooled mean value of absolute extrusion after surgery was 3.2 ± 0.9 mm, and the rate of major extrusion (> 3 mm) was 35.8%. Overall, functional scores improved after medial MAT. None of the surgical techniques were associated with poor functional outcomes and extruded meniscus; however, non-anatomically placement of allograft horns increased meniscus extrusion. Graft tear was the most common cause of reoperation (24.4%). Failure rate of 16.7% was demonstrated.
Medial MAT provides favorable outcomes, with acceptable rates of complication and failure regardless of surgical technique. While allograft extrusion appears equivalent for both bone plug and soft-tissue fixation techniques, positioning allograft horns at the native meniscal footprint may be critical for preventing extrusion. However, the heterogeneity and low level of evidence of the studies included in this systematic review prevent decisive conclusions regarding optimal MAT fixation techniques, clinical significance of allograft extrusion, or comparative clinical outcomes after medial MAT.