Medial Meniscal Allograft Transplantation

Abstract

Background:

This technique video reviews medial meniscal allograft transplantation (MAT) using a representative case example.

Indications:

Medial meniscal allograft transplantation is indicated in symptomatic patients with a deficient medial tibiofemoral compartment that has not progressed to arthritic changes. Concomitant procedures to address focal cartilage defects, ligamentous laxity, and/or limb malalignment should be performed prior to MAT or in the same surgical setting.

Technique Description:

Preoperative workup includes magnetic resonance imaging (MRI), prior arthroscopic pictures, and sizing radiographs. The Pollard radiographic method measures for the appropriate cryopreserved allograft size. Arthroscopic instruments remove residual meniscal tissue to a 1 mm base around the capsule. Percutaneous lengthening of the medial collateral ligament (MCL) at its femoral attachment aids visualization/instrumentation. This technique employs 8-mm bone plugs for anterior and posterior meniscal root fixation. Tunnels size 8.5 mm diameter and 10 mm depth are created. Once the meniscal allograft is placed in the joint, inside-out sutures are placed throughout the meniscal body. Sutures from the meniscal roots are secured with an anchor in the anterior proximal tibia.

Results:

There are numerous outcomes studies of meniscal allograft transplantation with a reported overall graft survivorship of roughly 70% at 10 years and 60% at 15 years follow-up.

Discussion/Conclusion:

Meniscal allograft transplantation is a temporizing measure that provides good midterm clinical results, although long-term failure rates increase incrementally. Most studies suggest return to sport is possible although activity modification is recommended.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

This is a video technique for a medial meniscal allograft transplantation procedure as performed by Dr Brian Werner at the University of Virginia. Our disclosures are listed.

We will review the following items in this video:

• Patient history, physical examination, and imaging

• Preoperative planning

• Patient positioning and preparation

• Surgical technique

• Postoperative management, rehabilitation, and return to sports guidelines

• Published outcomes and a concise review of the current literature

This case example is a 21-year-old man, who presents with ongoing medial-sided left knee pain and mechanical symptoms. He has a notable history regarding this knee, having previously undergone index anterior cruciate ligament (ACL) reconstruction with hamstring autograft in 2016, with subsequent failure and revision ACL using ipsilateral patellar tendon autograft in 2017. He is status post meniscal repair in 2019 for a large bucket handle tear. His examination demonstrates full range of motion with a moderate effusion and medial jointline tenderness. His ligamentous examination is stable, indicating an intact ACL graft.

Preoperative imaging includes plain radiographs that demonstrate findings status post–ACL reconstruction with the absence of any significant tunnel osteolysis and a magnetic resonance imaging (MRI) study demonstrating an intact ACL graft and medial meniscal deficiency with a residual meniscal tear and displaced fragment. He has intact cartilage without any notable chondral changes. Long cassette films do not demonstrate malalignment.

Preoperative planning for a patient undergoing meniscal allograft includes considerations for patient age, activity level, and symptom location and severity. ACL status and cartilage health are of paramount importance as criteria for considering this procedure. Sizing for meniscal allografts transplants in our institution is carried out using the Pollard method using radiographs with markers of known size. From a graft selection standpoint, we use appropriate size-matched cryopreserved grafts with less than 2 years of storage. In some cases, concomitant procedures are necessary to address ligamentous stability, malalignment, or focal cartilage lesions. Intra-operatively, there are a number of critical steps to highlight. Examination under anesthesia helps to confirm the presence or absence of ligamentous instability. For graft fixation, the main considerations are root fixation and meniscal body suturing. We prefer bone plug fixation for the anterior and posterior roots for both medial and lateral allografts, with 8-mm plugs, as will be demonstrated in the technique video. Some authors use alternatives such as slot bone fixation or soft tissue root techniques. For the meniscal body, we advocate an inside-out fixation technique using zone-specific cannulas for passage.

Patient positioning for this procedure is supine with a lateral leg post and non sterile thigh tourniquet at 300 mm Hg. A bump is secured to the table to allow for 90° leg positioning during portions of the procedure.

This surgical technique video demonstrates medial meniscal allograft transplantation with emphasis on the critical steps and key components of the procedure. The procedure commences with diagnostic arthroscopy carried out through standard anteromedial and anterolateral portals. Here we see findings consistent with meniscal deficiency with a large area of segmental absence of the medial meniscus. Prior all-side fixation devices are noted intra-articularly; however, gratefully minimal chondral changes are noted on the medial femoral condyle and tibial plateau. We have excellent visualization of the medial compartment, which is aided by a controlled proximal lengthening of the medial collateral ligament (MCL) at the femoral attachment. The remaining meniscal remnant is removed with basket biters and a shaver to the level of the joint capsule. Both the posterior and anterior root attachments are well visualized and cleared of residual tissue in preparation for the transplantation.

An accessory incision is created medially for subsequent inside-out suture passage, with dissection in the usual interval between semimembranosus and the medial head of the gastrocnemius to the level of the joint capsule. We are now ready to proceed with the placement of the sockets for the posterior and, subsequently, the anterior roots. A retrograde drilling device is used to create the posterior socket. Using the guide, the device is positioned in the center of the posterior root insertion. Here we demonstrate the view intra-articularly with placement of the device, deployment of the drilling component, and socket preparation.

We generally favor using 8.5-mm sockets and ream to a 1-cm depth. Excess bone debris is evacuated and a passage suture is advanced and retrieved. While these steps are being carried out, graft preparation has been accomplished on the back table. The cryopreserved graft is marked on the superior surface to maintain orientation, and the anterior and posterior bone plugs are fashioned using 8-mm core reamers. High-strength sutures are placed through the center of each plug and a locking stitch configuration is used at the meniscal root insertions of the graft, with 2 limbs exiting through the plug inferiorly.

Here you can see the preparation steps of the posteromedial counter-incision for passage of the meniscal sutures. It is critical to maintain the appropriate interval and tease the medial head of the gastrocnemius from the underlying capsule for accurate and safe suture passage. We are now prepared for introduction of the prepared graft into the joint. Using the passage suture, the posterior horn suture is shuttled through the tunnel, and the graft is advanced into the joint through the extended anteromedial portal with care to maintain graft alignment. An intra-articular view shows how the horn is shuttled posteriorly and the allograft is guided into its position with the plug anchoring into the posterior socket. This is a critical step and it is important to maintain graft orientation and settle the tissue and bone plug into position accurately and securely. Visualization of the graft confirms that our pre-operative sizing was accurate and the graft is seen to fit nicely within the patient’s medial compartment. Here fine adjustments are made to position the graft as closely as possible to restore the patient’s native meniscal anatomy. Next, zone-specific cannulas are used to place meniscal sutures in a combination of horizontal and vertical mattress configurations working from posteriorly to anteriorly.

Here you can see the operative set up with the surgeon passing and the assistant retrieving sutures sequentially. Multiple sutures are advanced on both the upper and lower surfaces of the meniscal allograft and retrieved by the assistant through the counter incision. Here is seen the final fixation of the meniscal allograft body. Next, our anterior horn socket is prepared anterograde under direct visualization through the anteromedial incision. Shuttling suture is used to similarly dock the anterior bone plug into this socket to complete graft positioning. Final securing of the graft is completed by tying the meniscal body sutures working from posterior to anterior. The sutures for the anterior and posterior roots are then fixed using a suture anchor placed approximately 1 cm distal to the tunnels as demonstrated here. A last look into the joint demonstrates our final meniscal allograft construct.

Postoperative management for medial meniscal allograft transplant follows a defined protocol with 25% partial weightbearing on crutches for the first 6 weeks. Knee range of motion is progressed immediately but flexion is limited to 90° until 6 weeks postoperatively. A graduated rehabilitation program is navigated with a goal for return to full activities at approximately 6 months postoperatively. Most patients return to some activities with approximately 50% returning to a similar level of sports. Appropriate patient counseling is important regarding return to high impact or cutting sports as well as allograft longevity.

Potential complications are listed and include infection, neurovascular injury, and iatrogenic chondral injury. Graft re-tearing or extrusion can result from inaccurate graft sizing, non anatomic graft placement, or postsurgical trauma.

There are numerous outcomes studies of meniscal allograft transplantation with a reported overall graft survivorship of around 70% at 10 years and 60% at 15 years’ follow-up. Longer term follow-up studies demonstrate incremental increases in failure rates with some patients going on to revision meniscal allograft transplantation or conversion to knee arthroplasty. Clinical outcomes do not appear to be negatively affected by the additional of concomitant procedures such as ligament reconstruction or cartilage repair procedures, although these data are not as well defined. Tegner activity scale results suggest most patients do not continue high-level sports over the long term.

Our references are listed. Thank you.