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    Surgical Technique for Meniscal Allograft Transplantation

    The authors describe their bridge-in-slot technique for lateral meniscal allograft transplantation and their 2-bone plug technique for medial meniscal allograft transplantation.

    Authors

    Utkarsh Anil, BA, and Eric J Strauss, MD

    Introduction

    With an annual incidence of 61 per 100,000, meniscal injuries represent one of the most commonly treated orthopaedic conditions. [1] Meniscal deficiency has been strongly associated with a negative effect on articular cartilage health, leading to early progressive osteoarthritis. [2] Biomechanical studies of cadaveric knees have shown that peak torque contact stresses increase by 235% after meniscectomy. [3] Research on tibiofemoral contact mechanics after meniscectomy has shown that the meniscus is a crucial load-bearing structure that optimizes the contact area and minimizes contact stress; meniscectomy of any kind disrupts that mechanism. [4]

    Meniscectomy for the treatment of meniscal injury is often unavoidable, especially in patients with complex or recurrent tears or failed meniscal repairs. [5] Meniscal allograft transplantation (MAT) has more recently emerged as a technique for meniscal rescue in young patients with symptomatic meniscal deficiency. [6] Although the operation is not new, the techniques are constantly changing and improving.

    RELATED: An Update on Meniscal Allograft Transplantation

    The purpose of this article is to describe our bridge-in-slot technique for lateral meniscal allograft transplantation and our 2-bone plug technique for medial meniscal allograft transplantation.

    Surgical Technique

    Positioning

    • The patient is placed in the supine position on a standard operating room table, with the operative leg in a circumferential leg holder and the foot of the table dropped. The position of the operative leg is such that the posterolateral and posteromedial aspects of the operative knee are easily accessible for the meniscal repair portion of the procedure (Figure 1).
    • A folded blanket is placed under the contralateral buttock to allow for slight hip flexion to relieve any tension on the femoral nerve and to create sufficient space for a figure-4 position with the operative leg.
    • A well-padded pneumatic tourniquet is placed around the proximal thigh of the operative leg to minimize blood loss. The operative leg is then prepared with an alcohol-based solution from the feet to the thigh below the tourniquet and draped in a sterile fashion.

    Figure 1. Patient positioning for meniscal transplantation, allowing access to anterior and posterior aspects of the knee.

    Diagnostic Arthroscopy and Meniscus Debridement

    • Traditional anterolateral and anteromedial portal sites are utilized to perform a diagnostic arthroscopy to confirm the presence of meniscal deficiency and assess the integrity of articular surfaces in the knee.
    • For cases of lateral meniscus allograft transplantation, the medial portal site should be placed 1 mm to 2 mm higher than usual to allow for easy access to the lateral compartment over the tibial spines.
    • During the diagnostic arthroscopy, the condition of the articular cartilage in the affected compartment should be assessed, with no more than mild grade 2 chondral wear present.
    • The remnant meniscus is debrided with an arthroscopic biter and standard 4.5-mm shaver, retaining a 1- to 2-mm peripheral rim of native meniscus for fixation (Figure 2).
    • In cases in which little to no remnant meniscus is present, a meniscus rasp is utilized to abrade the capsule to create a bleeding bed for subsequent tissue healing.

    Figure 2. A peripheral rim of native meniscus tissue should be left to aid in fixation.

    Graft Preparation: Lateral Meniscus Allograft

    • Allograft preparation is performed by an assistant on the back table during the diagnostic arthroscopy and debridement.
    • A cutting block, guide, and sagittal saw are used to create a 7-mm wide and 10-mm deep bone bridge connecting the anterior and posterior horn attachments.
    • If the allograft has a prominent tibial spine, it can be removed with a saw or rongeur to create a level bone bridge (Figure 3).
    • A #2 non-absorbable suture is passed through the meniscal allograft at the junction of the body and the posterior horn to assist with graft passage and reduction during insertion of the allograft into the knee (Figure 4).
    • The prepared graft is then placed into a kidney basin and covered with a wet gauze sponge to prevent drying.

    Figure 3. Sizing, measuring, and marking the bone bridge for the lateral meniscal allograft.

    Figure 4. Suture through the graft to allow for easier graft passage into the knee.

    Graft Preparation: Medial Meniscus Allograft

    • Allograft preparation is performed by an assistant on the back table during the diagnostic arthroscopy and debridement.
    • The posterior and anterior horn insertion sites are dissected free and clearly marked on the bone.
    • Then, 2.4-mm guide pins are inserted into the horn attachment sites and out through the bone of the allograft tibial plateau.
    • A collared reamer is placed over the guide pins and run to prepare the anterior and posterior bone plugs.
    • The bone plugs are sized to 8-mm wide and 10- to 12-mm deep.
    • High-strength sutures are passed through the horn attachment site and out through the central hole in each plug for later use in seating the plugs.
    • A 2-0 non-absorbable suture is passed through the meniscal allograft at the junction of the body and the posterior horn to assist with graft passage and reduction during insertion of the allograft into the knee (Figure 5).
    • The prepared graft is then placed into a kidney basin and covered with a wet gauze sponge to prevent drying.

    Figure 5. Graft preparation for medial meniscal allograft transplantation.

    Lateral Meniscus Transplant Approach and Slot Preparation

    • An accessory anterolateral portal is created in addition to an open posterolateral approach to the knee.
    • The course and insertion of the biceps femoris tendon is palpated and a 3-inch posterolateral incision is made. The incision is posterior to the lateral collateral ligament and anterior to the biceps femoris insertion to avoid injuring the common peroneal nerve, placed such that one-third of the incision is above and two-thirds is below the joint line.
    • From this initial incision, dissection is carried out to identify the interval between the posterior aspect of the iliotibial band and the biceps femoris tendon.
    • The lateral head of the gastrocnemius muscle is palpated within this interval, and with blunt dissection, space is created deep to the muscle to allow for an interval between the lateral head of the gastrocnemius and the posterolateral capsule of the knee.
    • Appropriate position is confirmed with palpation by plantar and dorsiflexing the foot. During this maneuver, tensioning of the muscle occurs posterior to the surgeon’s finger placed into the deep interval.
    • Once the position is confirmed, a surgical spoon or Henning retractor is inserted to serve as a neurovascular protector during the meniscal repair portion of the procedure.
    • Under spinal needle localization, the anterolateral accessory portal is made, in line with the anterior and posterior root insertions of the lateral meniscus. This portal will later be expanded into an arthrotomy for graft insertion.
    • A 4-mm bone cutter is introduced into the joint through the anterolateral accessory portal. A superficial reference slot is created by connecting the anterior and posterior horns of the meniscus.
    • Once the reference slot has been created to a depth of 4 mm, a drill guide with a hooked depth gauge is introduced through the anterolateral accessory portal. The guide is held parallel to the slope of the tibial plateau in the superficial reference slot and the tip is hooked around the posterior tibial cortex (Figure 6).
    • A guide pin is inserted through the drill guide into, but not through, the posterior tibial cortex. Direct palpation through the posterolateral portal can be performed to ensure that the posterior cortex has not been violated.
    • Although fluoroscopy is not routinely used in our practice, intraoperative fluoroscopic lateral views can be utilized to ensure proper drill depth if there is any concern.
    • Once the guide pin is in place, it is over-reamed using an 8-mm cannulated reamer (Figure 7).
    • The drill bit and guide pin are subsequently removed and an 8-mm slot cutting chisel is introduced over the drill hole.
    • The box chisel is gently impacted by a mallet along the course of the reamed tunnel to fashion the tunnel into a rectangle and remove any residual bone and cartilage.
    • The tines of the box chisel are visualized arthroscopically throughout its insertion to prevent injury to surrounding structures, especially the articular surface of the femoral condyle (Figure 8).
    • The box chisel creates a slot that is 8-mm wide and 10-mm deep. To further ensure that the bone tunnel accommodates the bone bridge on the graft, 7- and 8-mm rasps are used in series until the 8-mm rasp sits flush with the tibial plateau and glides easily in and out of the prepared bone slot (Figure 9).

    Figure 6. Reference slot marking and preparation for the lateral meniscal allograft.

    Figure 7. Guide pin and reamer placement for slot preparation.

    Figure 8. Box chisel insertion into the knee under arthroscopic guidance to prevent injury.

    Figure 9. Finalized bone tunnel preparation.

    Lateral Meniscus Graft Introduction and Fixation

    • A zone-specific meniscal repair cannula is inserted into the medial portal.
    • A single 2-0 meniscal repair needle is passed just anterior and lateral to the popliteus tendon, through the prepared remnant native meniscus. The meniscus repair needle is retrieved through the posterolateral incision.
    • With the second needle removed, the suture is grasped and retrieved through the anterolateral accessory portal, which has been extended into an arthrotomy large enough to allow graft passage.
    • The shuttling suture is then used to shuttle the graft passage sutures from the prepared meniscus allograft.
    • With varus stress applied to the knee, tension is maintained on the graft passage sutures as the bone bridge is inserted into the slot under direct visualization. Two army-navy retractors are used to clearly expose the slot.
    • Bone bridge insertion into the trough should require no more than gentle digital pressure. The combination of gentle tension on the graft passage sutures, varus stress on the knee, and digital pressure from the surgeon through the arthrotomy will help reduce the lateral meniscus allograft into the lateral compartment (Figure 10).
    • Once in position, the meniscus allograft is fixed peripherally by multiple inside-out vertical mattress sutures using 2-0 non-absorbable sutures with the needles captured through the posterolateral approach (Figure 11).
    • Sutures are placed on the superior and inferior surfaces of the allograft to provide a balanced repair with the meniscus in anatomic position. Care must be taken at this step to prevent entanglement of sutures before they are finally tied down.
    • An all-inside technique of suture passage is utilized posterior to the popliteus tendon and for fixation of the posterior horn. One or 2 implants are typically utilized.
    • Once peripheral fixation sutures have been placed, the bone bridge is stabilized with a single 7×23-mm bioabsorbable interference screw placed central to the bone bridge over a nitinol guide wire (Figure 12).
    • With the knee in full extension, the meniscus repair sutures are then tied within the posterolateral approach.
    • Additional fixation of the anterior aspect of the meniscus allograft can be achieved with direct repair through the anterolateral arthrotomy using 2-0 high-strength sutures.
    • The posterolateral approach and anterolateral arthrotomy are then irrigated and closed in layers using 0 Vicryl for deep tissue re-approximation, 2-0 Vicryl for subcutaneous tissue re-approximation, and 3-0 Monocryl suture for the skin.
    • The portals are closed subcuticularly with 3-0 Monocryl sutures. The incisions are sealed with Dermabond adhesive, and sterile dressings are applied.
    • The operative knee is then placed into a hinged knee brace locked in extension.

    Figure 10. Graft introduction into the knee with guiding sutures in place.

    Figure 11. Graft fixation performed arthroscopically.

    Figure 12. A single 7×23-mm bioabsorbable interference screw is placed central to the bone bridge.

    Medial Meniscus Transplant Approach, Tunnel Preparation, and Graft Fixation

    • Following arthroscopic preparation of the remnant meniscus, a retrograde reamer is passed into the site of the posterior medial meniscus root with the use of an anterior cruciate ligament (ACL) tibial drill guide.
    • An 8.5-mm diameter tunnel is reamed to a depth of 12 mm to 15 mm, at which point a passing suture is passed and retrieved through the anteromedial portal site.
    • A posteromedial approach is then created to retrieve the needles from the inside-out meniscal repair.
    • The medial collateral ligament (MCL) is palpated and an incision is made just posterior to its course, one-third above the joint line and two-thirds below the joint line.
    • The interval between the semimembranosus and the medial head of the gastrocnemius is developed. The medial head of the gastrocnemius muscle is palpated within this interval, and with blunt dissection, space is created deep to the muscle. This creates an interval between the medial head of the gastrocnemius and the posteromedial capsule of the knee.
    • Appropriate position is confirmed with palpation by plantar and dorsiflexing the foot. During this maneuver, tensioning of the muscle occurs posterior to the surgeon’s finger placed into the deep interval.
    • Once confirmed, a surgical spoon or Henning retractor is inserted to serve as a neurovascular protector during the meniscal repair portion of the procedure.
    • The anteromedial portal site is extended to create an arthrotomy large enough to pass the graft into the joint. The posterior tunnel passing suture is used to shuttle the posterior bone plug suture.
    • With gentle tension on the bone plug suture the posterior bone plug is inserted into the posterior tunnel. A freer elevator may be used to help guide the bone plug into position.
    • The medial meniscus allograft is then reduced into the medial compartment.
    • Zone-specific cannulas are then used to perform an inside-out medial meniscal repair, with sutures passed in vertical mattress fashion.
    • Sutures are placed on the superior and inferior surfaces of the allograft to provide a balanced repair with the meniscus in anatomic position.
    • Through the anterior arthrotomy, the anterior root insertion of the medial meniscus is exposed with 2 army-navy retractors.
    • An 8.5-mm anterior tunnel is then reamed to a depth of 15 mm over a guide pin placed at the anatomic site of the anterior root of the medial meniscus. A 2.5-mm drill is used to create a hole 2 cm distal to the joint line.
    • A Hewson suture passer is then inserted, allowing the suture from the anterior bone plug to be passed. Gentle tension on the suture will seat the anterior bone plug into position.
    • Once the peripheral fixation of the meniscus is inspected and confirmed to be stable, the anterior and posterior bone plugs are then fixed using cortical buttons tied over to the proximal tibial cortex.
    • With the knee placed in full extension, the meniscal repair sutures are then tied through the posteromedial approach.
    • The posteromedial approach and anterolateral arthrotomy are then irrigated and closed in layers using 0 Vicryl for deep tissue re-approximation, 2-0 Vicryl for subcutaneous tissue re-approximation, and 3-0 Monocryl suture for the skin.
    • The portals are closed subcuticularly with 3-0 Monocryl sutures. The incisions are sealed with Dermabond adhesive, and sterile dressings are applied.
    • The operative knee is then placed into a hinged knee brace locked in extension.

    Postoperative Course and Rehabilitation

    The patient is kept in toe-touch weight-bearing status for the first 2 weeks postoperatively, with the knee in the hinged knee brace locked in extension. At the initial postoperative visit, the hinged knee brace is unlocked from 0 to 90.

    Starting at postoperative week 2, weight-bearing status is progressively advanced as tolerated. If the patient’s gait has been normalized, crutches are discontinued around 4 weeks postoperatively. Weight-bearing at greater than 90 is restricted for the first 6 weeks, at which time the hinged knee brace is unlocked completely. Once quadriceps strength has improved, with the patient exhibiting a straight leg raise without an extensor lag, the hinged knee brace is discontinued.

    The patient should achieve full range of motion by 8 to 12 weeks after surgery. At 8 weeks, the patient begins strengthening exercises and may start using a stationary bike. Jogging is permitted at 12 weeks, with full return to sports at 6 to 9 months after surgery, depending on the patient’s return of quadriceps and hamstring strength and endurance.

    Concomitant Procedures

    We prefer the 2-bone plug technique for concomitant ACL reconstruction with medial or lateral meniscal deficiency to avoid the bone bridge interfering with the ACL tibial tunnel. In patients with malalignment and valgus/varus deformity that requires osteotomy for biomechanical stability of the graft, we perform the operation in a staged fashion. Patients undergo osteotomy and recover for 6 months postoperatively, after which they return to the operating room for medial or lateral meniscus allograft transplantation.

    Graft Fixation Technique Choice

    Various techniques for graft fixation have been described, including soft tissue fixation, bone plug technique, and bridge-in-slot technique. Soft-tissue fixation has fallen out of favor, as anatomic fixation of the horns has been shown to be essential for the graft to function well; the biomechanical advantage is often lost without some bony attachment. [7,8]

    As a result, the bridge-in-slot technique is our preferred method of graft fixation for the lateral meniscus. Although the medial meniscus graft can also be fixed using the bridge-in-slot technique, the origin of the ACL often gets in the way and can require debridement of up to one-third of the ACL fibers. Although technically demanding and often dependent on the accuracy of ideal tibial tunnel placement, bony fixation using 2 bone plugs has been shown to be very successful. [9,10]

    Absent further evidence comparing the 2 fixation techniques – particularly with regard to ACL-related failures and morbidity – we prefer to use the double bone plug technique for medial meniscus graft fixation.

    Conclusion

    Meniscal allograft transplantation offers an excellent surgical option for suitable young active patients with symptomatic meniscal deficiency. At our institution, we prefer to use the double bone plug technique for medial meniscus transplantation and the bridge-in-slot technique for lateral meniscus transplantation.

    Author Information

    Utkarsh Anil, BA, and Eric J. Strauss, MD, are from the Division of Sports Medicine, Department of Orthopaedic Surgery, NYU Langone Health, New York, New York.

    Disclosures

    Mr. Anil has no disclosures relevant to this article. Dr. Strauss has disclosed that he is a paid consultant for Arthrex and Smith & Nephew

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