Introduction

Extrusion following meniscus allograft transplantation remains a significant limitaiton of the procedure.

Content

When faced with an irrepairable meniscus or a patient who has had a total or subtotal meniscectomy, meniscus allograft transplantation (MAT) is the preferred modality to restore biomechanical function of the meniscus. The indications for meniscus allograft transplantation are yet to be established. However, currently, MAT has previously been indicated for symptomatic patients who have mild or early osteoarthritis, are younger than 50 years of age, and present with an Outerbridge grade II or lower. The short- to intermediate-term results confirmed noteworthy clinical improvements and consistent objective findings. On the other hand, the successful outcome would be reduced by various complications. Therefore, long-term observation required to evaluate the longevity of these results.

The possible complications of meniscus transplantation include reruptures, graft shrinkage, and extrusion. Graft shrinkage is common with the lyophilized grafts, whereas rare with fresh or fresh frozen grafts. The long-term effects of graft extrusion remain controversial.

The ultimate goal of MAT is cartilage protection and its efficacy has not yet been fully investigated. In some animal model studies, meniscus transplantation was more effective in reducing the cartilage degeneration than meniscectomy, albeit not comparable to the intact meniscus. Some authors recommend to perform MAT as early as possible to improve the chondroprotective role, whereas others report that the timing of MAT was not significantly correlated with the chondroprotection. Verdonk et al. reported that there were no radiographic evidence of joint space narrowing in 41% of the patients and MRI evidence of progression of arthritis in 35% of the patients during the ≥10 years of follow-up period. The long-term effects of MAT should be further investigated in future studies. However, it is our understanding that MAT would provide some level of chondroprotection, although it cannot be comparable to the intact meniscus.

The extrusion of the graft is regarded as another complication after MAT, and relatively more studies have investigated this issue compared to the shrinkage. Several studies have investigated the change of graft extrusion after MAT using serial MRI. Most of the studies focused on the graft extrusion in radial direction observed on coronal plane, while only few studies from the same study group evaluated the graft extrusion in anterior or posterior direction. It is supposed that the graft “extrusion” may be not a progressive problem, but rather may be a problem that already existed immediately after surgery due to assumed reasons including graft size mismatch or inadequate graft position. There were studies on efforts to prevent graft extrusion by reducing the graft size or using different approach for graft placement.

Association between the extrusion of native meniscus and progression of symptomatic knee osteoarthritis has been reported. However, many studies on the extrusion after MAT reported that the extent of extrusion did not correlate with the clinical outcomes, although they have confirmed the occurrence of extrusion. There are several technical considerations to optimize and improve extrusion at the time of meniscus allograft transplantation. In addition, we disucss a novel and developing technique of centralization in order to prevent extrusion of the graft, and hopefully promote chondroprotection over the long-term outcome.

References

Kim, JH., Lee, S., Ha, D.H. et al. The effects of graft shrinkage and extrusion on early clinical outcomes after meniscal allograft transplantation. J Orthop Surg Res 13, 181 (2018). https://doi.org/10.1186/s13018-018-0892-0

Lee SM, Bin SI, Kim JM, Lee BS, Lee CR, Son DW, Park JG. Long-term Outcomes of Meniscal Allograft Transplantation With and Without Extrusion: Mean 12.3-Year Follow-up Study. Am J Sports Med. 2019 Mar;47(4):815-821. doi: 10.1177/0363546518825251. Epub 2019 Feb 14. PMID: 30763116.