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.

Introduction

Meniscus transplantation is indicated for patients with a symptomatic meniscus deficient knee which is well aligned and stable. Initially MAT was indicated for patients with intact cartilage surfaces however the indications have been extended to include the treatment of instability and knees with greater degrees of chondral wear.

Content

A recent Meta-analysis have reported that 85.8% of medial and 89.2% of lateral meniscal allograft transplants survive at midterm (5-10 years) while 52.6% of medial and 56.6% of lateral meniscal allograft transplants survive long term (>10 years). Functional outcomes 10 years after MAT are fair and improved compared with preoperative scores. Patients undergoing lateral MAT have demonstrated greater pain relief and functional improvement than patients undergoing medial MAT. MAT is associated with a significant re-operation rate of up to 20% and patients need to be counselled accordingly.

The majority (77%) of athletes and physically active patients are able to return to sport after MAT; approximately two-thirds are able to perform at preinjury levels. Most studies have reported no significant differences between the soft tissue suture and bone fixation in terms of meniscal allograft tear rates, failure rates, Lysholm scores, and VAS scores. Meniscal extrusion is also similar with both techniques.

Associated malalignment and ligamentous instability should be corrected and overall, there seems to be no significant difference between the postoperative patient reported outcome scores in terms of isolated MAT and MAT combined with other procedures i.e. ligament reconstruction, osteotomy. However, more data is required to verify the effects of osteotomy and cartilage procedures on the clinical outcomes of MAT.

More latterly the importance of the meniscus in knee instability has been appreciated and thus the potential role of MAT. Medial MAT has been shown to improve not only anteroposterior stability but also rotational stability in the meniscus-deficient ACL-reconstructed knee. Lateral MAT showed improvements in the anterior drawer and Lachman tests but not in the pivot-shift test or side-to-side difference on Telos stress radiographs in meniscus-deficient ACL-reconstructed knees.

There is currently insufficient data within the literature to state whether MAT is chondroprotective or cost-effective. MAT needs to be approximately one-third more effective in delaying OA in previously meniscectomized knees to be considered cost-effective. Younger, non-obese patients have the lowest required efficacy of MAT to be cost-effective.

References

Bendich I, Rubenstein W, Mustafa Diab M, Feeley B. Evaluating meniscus allograft transplant using a cost-effectiveness threshold analysis. Knee. 2018 Dec;25(6):1171-1180. doi: 10.1016/j.knee.2018.08.016. Epub 2018 Sep 17. PMID: 30232027.

Bin SI, Nha KW, Cheong JY, Shin YS. Midterm and Long-term Results of Medial Versus Lateral Meniscal Allograft Transplantation: A Meta-analysis. Am J Sports Med. 2018 Apr;46(5):1243-1250. doi: 10.1177/0363546517709777. Epub 2017 Jun 13. PMID: 28609637.

Grassi A, Bailey JR, Filardo G, Samuelsson K, Zaffagnini S, Amendola A. Return to Sport Activity After Meniscal Allograft Transplantation: At What Level and at What Cost? A Systematic Review and Meta-analysis. Sports Health. 2019 Mar/Apr;11(2):123-133. doi: 10.1177/1941738118819723. Epub 2019 Jan 14. PMID: 30638438; PMCID: PMC6391552.

Jauregui JJ, Wu ZD, Meredith S, Griffith C, Packer JD, Henn RF 3rd. How Should We Secure Our Transplanted Meniscus? A Meta-analysis. Am J Sports Med. 2018 Jul;46(9):2285-2290. doi: 10.1177/0363546517720183. Epub 2017 Aug 17. PMID: 28816515.

Lee BS, Kim HJ, Lee CR, Bin SI, Lee DH, Kim NJ, Kim CW. Clinical Outcomes of Meniscal Allograft Transplantation With or Without Other Procedures: A Systematic Review and Meta-analysis. Am J Sports Med. 2018 Oct;46(12):3047-3056. doi: 10.1177/0363546517726963. Epub 2017 Sep 25. PMID: 28945482.

Novaretti JV, Patel NK, Lian J, Vaswani R, de Sa D, Getgood A, Musahl V. Long-Term Survival Analysis and Outcomes of Meniscal Allograft Transplantation With Minimum 10-Year Follow-Up: A Systematic Review. Arthroscopy. 2019 Feb;35(2):659-667. doi: 10.1016/j.arthro.2018.08.031. PMID: 30712641.

Yoon KH, Lee HW, Park SY, Yeak RDK, Kim JS, Park JY. Meniscal Allograft Transplantation After Anterior Cruciate Ligament Reconstruction Can Improve Knee Stability: A Comparison of Medial and Lateral Procedures. Am J Sports Med. 2020 Aug;48(10):2370-2375. doi: 10.1177/0363546520938771. Epub 2020 Jul 21. PMID: 32692971.