Meniscus allograft transplantation is an area of active research, as the importance of the meniscus in the longevity of the native knee joint is increasingly recognized. This article describes a modified meniscus allograft transplant technique using a hybrid technique with 1 bone tunnel with fixation of the allograft through the use of a posterior bone plug and fixing it in the anterior part with the use of a soft tissue plug, which is applicable both for the lateral and medial meniscus.

Meniscus tears are one of the most common knee injuries, once treated with total eniscectomy previously, the current management is preservation of the meniscus as a Gold standard. They were recognized in the 1930s, and the treatment was an open total meniscectomy.

Fortunately, Fairbank discovered the adverse effects of total meniscectomy, where he demonstrated that the joint is exposed to greater contact pressures and progresses towards joint degeneration.

Currently, total meniscectomy is no longer performed and meniscus repair, partial meniscectomy, and meniscal allograft transplantation are preferred.^1–5

Meniscus allograft transplantation decreases contact stress on the knee joint and provides pain relief. The ideal candidate is under 50 years of age, mass index less than 30, a stable and well- aligned knee, Outer bridge classification less than grade 3, Kellgren-Lawrence grade I or II, and symptoms of a previous subtotal or total meniscectomy. Common allograft preparation and fixation techniques include soft tissue fixation, bone plugs, or bone bridging. Initially, the proposed techniques required performing a small arthrotomy with the assistance of the arthroscope.

The end of the 80s, Keene demonstrated the possibility of performing this technique arthroscopically, which is a less invasive and beneficial way for the patient. In this work we explain our hybrid placement technique, which consists of the placement of a meniscal transplant with a posterior bone plug and an anterior soft tissue plug, which has the advantage of preserving bone stock, reducing the risk of confluence of anterior bone tunnels, reducing of surgical time, it is applicable to medial and lateral meniscus and is a less demanding technique.

Our technique has been developed by the main author and performed for more than 20 arthroscopic meniscus transplants with good results.^6–9

Surgical technique

Indications are patients under 50 years of age with a non-functional meniscus as a result of a previous partial or total meniscectomy, patients functionally limited by localized pain in the affected compartment, patients with a severity of the cartilage defect less than Outerbridge grade III, patients with normal or correctable knee alignment. Contraindications include patients over 50 years of age, patients with osteoarthritic changes or chondral lesions corresponding to an Outerbridge III classification or higher.

We determined the size by means of magnetic resonance imaging by measuring anteroposteriorly the distance between the tibial spine and the margin of the tibial metaphysis and laterally the distance between a line parallel to the anterior surface of the tibia above the tuberosity and another tangent to the posterior edge of the corresponding tibial plateau.^10,11

Allograft preparation

A meniscus with a bone block is obtained from the allograft bank, compatible with the measurements made preoperatively. The allograft is thawed in a mixture of 1 g vancomycin and 200 ml normal saline for 30 minutes.

Our preference is to use Arthrex instrumentation (Arthrex, Naples, FL) to simplify the process.

The first step is to mark the anterior horn and posterior horn to maintain orientation during preparation.

Subsequently, using a saw, the cuts of the posterior bone plug are made. Ideally, it should have a trapezoidal shape, with a diameter of 7.0 mm to 8.0 mm and a length of 10-15 mm. The anterior bone block is initially cut and all bone tissue is removed to preserve only soft tissue. Next, a 2 mm center hole is drilled in the posterior bone block and a #2 FiberWire suture with a straight needle is used to suture 2 to 3 times through the center hole of the bone block incorporating meniscal tissue through the hole posterior insertion. The anterior soft tissue plug is prepared in the same way with modified or horizontal Kessler stitches.^12,13

Location of portals

Standard anterolateral and anteromedial portals are made and the joint is visualized with a 30-degree arthroscope while the knee is insufflated with normal saline. A transpatellar accessory portal of the knee is made to facilitate fixation of the posterior horn. With the camera facing the posterior compartment, a spinal needle is inserted to estimate the best trajectory for soft tissue anchor insertion.

Meniscal bed preparation

An arthroscopic razor is introduced through the posteromedial portal and the remnants of the meniscal tissue are debrided to a bleeding edge of approximately 1 mm. The residual meniscus should not be completely removed because it prevents radial displacement of the allograft and serves as a firm bed for meniscus fixation. We performed a limited plasty of the posterior femoral condyle for adequate visualization of the posterior horn of the meniscus. Both insertions of the meniscus roots must be identified. With the help of an arthroscopic shaver and a curette, the cartilage is decorticated until reaching the bone and observing a bleeding edge.

Posterior tunnel preparation

A tibial guide from the meniscus root or anterior cruciate ligament (ACL) is used with an angle of 65 through the anteromedial or anterolateral portal respectively, the posterior horn tunnel is made retrogradely through the most anterior portion of the pons residual of the point of attachment of the meniscus. The root of the posterior medial meniscus should be placed behind the medial tibial tubercle, in front of the tibial insertion site of the posterior cruciate ligament, and the root of the posterior lateral meniscus should be placed behind the lateral tibial eminence.

ACL guidance is used at 65 degrees

It is drilled with the FlipCutter bur in the center of the posterior remnant. Choose a FlipCutter® drill bit size 1 mm larger than the diameter of the posterior plug of the donor meniscus to facilitate passage. Remove the guide and tap the cannula into the bone. Rotate the FlipCutter II bit to its cutting position and drill retrograde to a depth of 10-15 mm. Then use the shaver to remove any foreign tissue around the top edge of the tunnel. Any piece of soft tissue or cartilage will present difficulty in reducing the posterior plug.

Pass a FiberStick™ suture through the FlipCutter® Drill Guide and retrieve sutures passing through the medial portal or a #1 PDS suture using a knot pusher through the tibial tunnel for subsequent suture transfer from the definitive root threads of the posterior meniscus.

Passage of the graft through the portal

Pass the posterior bone plug suture with the previously placed posterior shuttle suture through the posterior cavity and down the tunnel, through the ipsilateral portal.

Begin inserting the allograft by guiding it with the posterior horn while pulling the posterior root meniscus sutures.^14,15

Continue to tighten the other sutures while the allograft is inserted. Use the probe to help guide the posterior bone plug into position while applying gentle traction on the posterior suture.

Peripheral fixation of the meniscus

Subsequently, the All-inside sutures begin to be placed. We prefer to use the Smith & Nephew Fast- Fix system. We start at the posterior horn and the middle part of the body and move towards the anterior part and anterior root. An average of 6 to 8 sutures with vertical mattress stitches are required to complement the fixation, placed 5 mm apart and distributed on both its upper and lower surface.

It is fixed peripherally with the use of 6 to 8 Fast-Fix anchors.

Fixation of the anterior soft tissue plug

Anterior root fixation is performed after insertion of the posterior meniscus root bone plug. This sequence allows you to have a more precise idea about the correct location. The imprint of the anterior horn of the medial meniscus is located in front of the tibial insertion of the ACL, behind the intermeniscal ligament.

The insertion of the lateral anterior meniscal horn can be found in front of the lateral eminence.

The insertion of the anterior horn of the meniscus is recreated with the knotless suture anchoring device, we prefer to use PEEK Swivelock type 4.75 mm (Arthrex), the anchor insertion angle is approximately 60-70° in the sagittal plane (up to the tibial plateau).

The anterior horn is fixed with the use of a 4.75 mm Swivelock anchor

Adequate stability and tension of the entire periphery is confirmed before fixing the posterior bone plug.

Posterior bone plug fixation

Visualize to ensure that the plug and meniscus have been reduced correctly, once the proper position has been confirmed, the fixation of the bone plug sutures is carried out using a knotless anchor type PEEK Swivelock 4.75 mm (Arthrex) in the anterior tibial cortex, paying attention. Be careful to fix it with adequate tension.

The preservation of the meniscus l has been one of the greatest evolutions in the last century. Although the incidence of meniscus repair is increasing, meniscal allograft transplantation is considered a salvage procedure.

Success rates vary widely in the literature. Early studies demonstrated lower success rates and outcome scores, however, as advances in instrumentation and techniques have evolved, more recent studies have shown better results. Comparisons between different preparation and fixation techniques have been studied. Soft tissue fixation, bone plug fixation, and bone bridge fixation have been the main focus of the literature.^16,17

Once the allograft is reduced, the knee is cycled several times to ensure proper position and stability. Finally, a final inspection is carried out to avoid overlooking any other added injuries.

The knee is drained and closed with 4-0 Monocryl suture and 3-0 Nylon skin. Alhalki et al.17 compared fixation methods using bone plugs versus soft tissue plugs and evaluated contact pressure and contact area. The authors concluded that the use of bone plugs restores contact pressures and contact area near a native meniscus.

McDermott et al.18 also studied tibial contact pressures and concluded that bone plug fixation showed lower contact pressure compared to soft tissue plug fixation. Although some studies have shown similar results between bone fixation and soft tissue fixation, there is currently controversy as to which technique is better. The technique presented in this article is an evolution of the original technique. We have discovered that it is simple, effective, reproducible and has certain advantages compared to the other techniques described.

Further clinical studies are currently being conducted to examine outcomes and patient satisfaction with our technique for comparison with other established techniques (Table 1).

This is an alternative meniscus transplant technique, which we have found provides secure fixation of the meniscus horns, with a low percentage of extrusion and has the benefits of being less surgically invasive, with a learning curve simpler as well as fewer adverse effects.

None.

The authors declare no conflicts of interest.

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