Page 29 - ISAKOS 2018 Newsletter Volume 2

Update on Meniscal Allograft Transplantation
Indications
MAT is indicated for patients with symptomatic post- meniscectomy syndrome following previous subtotal or functional meniscectomy. Patients often present with painful effusions and unicompartmental pain following previous injury or surgery. MAT may be considered when symptoms persist despite appropriate conservative management (e.g., unloader bracing, nonsteroidal anti-inflammatory drugs, biologic injections, rehabilitation programs). The role of prophylactic MAT remains highly controversial. While meniscal deficiency may progress toward radiographic evidence of joint-space narrowing over time, clinical symptoms do not accurately correlate. Additionally, there is no definitive evidence that MAT decreases the radiographic advancement of osteoarthritis (OA) or that the duration of allograft survival following MAT is >1 to 2 decades. Given these considerations, MAT is not routinely indicated for patients with asymptomatic meniscal deficiency, and for those who should be counseled effectively and monitored closely for signs and/or symptoms of post- meniscectomy syndrome.
MAT also may be indicated for patients with meniscal deficiency as a result of failed primary anterior cruciate ligament (ACL) reconstruction or chronic ACL insufficiency. It is well known that the medial meniscus plays a critical role as a secondary stabilizer to anterior tibial translation (i.e., brake stop mechanism) and that the lateral meniscus likely has a stabilizing effect during the pivot shift. MAT may be considered as an adjunct to ACL reconstruction in patients with functional instability and meniscal deficiency, particularly those with high-grade sagittal instability (grade IIIB on the Lachman test) and/or explosive pivot shift (Grade III on the pivot-shift test). Another important indication is the presence of meniscal deficiency in the setting of a symptomatic cartilage lesion. This scenario is most often encountered in the lateral compartment. In such cases, the addition of MAT can be considered as a means of optimizing the outcome of cartilage restoration.
Applied Surgical Anatomy
Understanding the unique anatomical and biomechanical characteristics of the medial and lateral menisci is necessary when considering the addition of MAT in one’s clinical practice. These striking differences influence the timing and frequency of MAT, the need for concomitant procedures, and, possibly, the selection of surgical technique.
The medial tibial plateau is concave, with the meniscus covering approximately 64% of the plateau and bearing an average of 50% of the load. As a result, medial meniscectomy is often well tolerated, with a delayed (or absent) or post-meniscectomy syndrome and decreased need for concomitant cartilage restoration with medial MAT. The medial meniscus is inherently more stable than the lateral meniscus through attachments of the meniscotibial (coronary) ligaments to the deep MCL. Reproducing these meniscotibial ligament insertions can be considered during medial MAT.
Introduction
Seth L. Sherman, MD
University of Missouri Department of Orthopaedic Surgery
Columbia, MO UNITED STATES
Trevor R. Gulbrandsen, BS
University of Missouri School of Medicine Columbia, MO UNITED STATES
Dimitri M. Thomas, MD
University of Missouri Department of Orthopaedic Surgery
Columbia, MO UNITED STATES
The knee meniscus contributes to shock absorption, joint lubrication, chondroprotection, proprioception, secondary stabilization, and load distribution. Given its critical role, surgeons should err on the side of meniscal preservation whenever possible. For symptomatic patients with meniscal deficiency, meniscal allograft transplantation (MAT) has evolved as a reliable surgical option for this challenging clinical problem.
The goal of MAT is to restore the biomechanical properties of the native damaged meniscus, thereby reducing pain, increasing overall knee function, and improving quality of life. Successful MAT requires careful management of patient expectations, appropriate patient selection, thorough preoperative planning, meticulous surgical technique, and adherence to postoperative rehabilitation guidelines. While some evidence-based recommendations exist, controversy remains regarding MAT indications, techniques, and outcomes.
CURRENT CONCEPTS
ISAKOS NEWSLETTER 2018: VOLUME II 27