5 Points on Meniscal Allograft Transplantation
TAKE-HOME POINTS
- Patient selection is critical for obtaining long-term functional outcome improvements and reduced pain, with the ideal MAT candidate being a chronologically and physiologically young patient (<50 years) with symptomatic meniscal deficiency.
- Existing pathology in the knee needs to be carefully considered and issues such as malalignment, cartilage defects, and/or ligamentous instability may require a staged or concomitant procedure.
- Accurate graft width and length measurements are vital, and the most common technique used today includes measuring the meniscus on anteroposterior and lateral radiographic images.
- When preparing the graft for the bone-bridge technique, the bone is fashioned to create a bone bridge 10 mm in depth by approximately 7 mm in width, incorporating the anterior and posterior horns of the meniscus.
- Graft fixation can be accomplished by placing vertical mattress sutures and tying those down with the knee in full extension.
In a meniscus-deficient patient with chondral lesions (Outerbridge grade 3 or 4), concomitant MAT and cartilage restoration should be considered. Depending on the size and location of the chondral lesion, options include marrow stimulation, autologous chondrocyte implantation, osteochondral autograft transfer, as well as chondral and/or osteochondral allograft transplantation. In a systematic review of concomitant MAT and cartilage restoration procedures, Harris and colleagues25 found that failure rates of the combined surgery were similar to those of either surgery in isolation.
Young athletes sustaining anterior cruciate ligament (ACL) tears commonly also have meniscal pathology that must be addressed. Most cases are treated with meniscal repair or partial meniscectomy, but occasionally patients present with ACL tear and symptomatic meniscal deficiency. Specifically, MAT survival relies largely on a knee with ligamentous stability, whereas outcomes of ACL reconstruction are improved with intact and functional menisci.29 The surgical technique for MAT is modified slightly in the setting of performing a concomitant ACL reconstruction, with the ACL tibial tunnel drilled to avoid the meniscal bone slot if possible, followed by femoral tunnel creation. Femoral fixation of the ACL graft is accomplished after preparation of the meniscal slot. The meniscal graft is set into place (sutures are not yet tied), and tibial fixation of the ACL graft is performed next. We typically use an Achilles allograft for the ACL reconstruction, with the bone block used for femoral fixation to avoid bony impingement between the MAT bone bridge/block and the ACL graft. With the knee in full extension, the MAT sutures are tied at the conclusion of the surgical procedure. Concomitant MAT and ACL reconstruction has yielded positive long-term clinical outcomes, improved joint stability, and findings similar to historical results of ACL reconstruction or MAT performed in isolation.30,31
CONCLUSION
When used with the proper indications, MAT has demonstrated the ability to restore function and reduce pain. Successful meniscal transplant requires attention to the patient’s past medical and surgical history. Similarly, care must be taken to address any concomitant knee pathology, such as coronal realignment, ligament reconstruction, or cartilage restoration.
