Allograft Meniscus Transplantation: Bridge-in-Slot Technique

Allograft Meniscus Transplantation

Bridge-in-Slot Technique

Andreas A. Gomoll, Jack Farr, II and Brian J. Cole

Chapter Synopsis

• This chapter summarizes the indications for and technique and results of meniscal allograft transplantation with the bridge-in-slot technique for the treatment of symptomatic meniscal deficiency.

Important Points

• Meniscal transplants are indicated for symptomatic compartment overload caused by total or subtotal meniscectomy.

• Osteoarthritis, with the exception of very specific circumstances, is a contraindication.

Clinical and Surgical Pearls

• Ensure that the graft has been received in acceptable condition and that the size and side are correct before the patient is anesthetized.

• A transpatellar tendon approach is commonly necessary to align the slot with the anterior and posterior meniscal roots.

• Preserve a 2-mm peripheral rim of meniscal tissue if possible to facilitate the capsular repair and potentially reduce extrusion.

• Use the appropriate varus or valgus stress with hyperflexion followed by extension of the knee to reduce the transplant under the femoral condyle. Especially medially, pie-crusting of the medial collateral ligament (MCL) can occasionally become necessary if the compartment is tight.

Clinical and Surgical Pitfalls

• Make sure the graft is not undersized; this can complicate capsular repair and increases the failure rate.

It is generally believed that any significant meniscectomy alters the biomechanical and biologic environment of the normal knee, eventually resulting in pain, recurrent swelling, and effusions. Overt secondary osteoarthritis is often the endpoint.1,2 Recognition of these consequences has led to a strong commitment within the orthopedic community to meniscus-sparing interventions. However, there are cases in which meniscal preservation is not possible. In carefully selected patients, meniscal allografts can restore nearly normal knee anatomy and biomechanics, providing excellent pain relief and improved function.⁹

Several techniques exist for allograft meniscus transplantation, including bone plugs, a keyhole technique, and a dovetail technique. We prefer the bridge-in-slot technique ⁴ because of its simplicity and secure bone fixation, the ability to more easily perform concomitant procedures such as osteotomy and ligament reconstruction, and the advantages of maintaining the relationship of the native anterior and posterior horns of the meniscus.

Preoperative Considerations

It is essential to elicit a thorough history, including the causative mechanism, associated injuries, and prior treatments. Operative reports are helpful to evaluate arthritic changes that could constitute a contraindication to meniscal transplantation.

Typical History

• Knee injury, often an acute traumatic event initiating meniscal treatment

• One or more meniscectomies, open or arthroscopically performed with initial improvement

• Subsequent development of ipsilateral joint line pain and activity-related swelling

• Giving way (occasionally reported)

Physical Examination

Factors Affecting Surgical Indication

• Range of motion: usually preserved

• Joint line or femoral condyle tenderness

• Objective evidence of joint space narrowing (magnetic resonance imaging, flexion weight-bearing radiographs); development of localized or diffuse chondral disease in the ipsilateral compartment

Factors Affecting Surgical Planning

• Preexisting incisions

• Limb malalignment (may require concomitant realignment procedure)

• Ligamentous instability (may require prior or concomitant reconstructive procedure)

• Chondral injury, typically involving the femoral condyle (may require concomitant cartilage repair procedure)

Imaging

• Weight-bearing anteroposterior radiograph in full extension

• Weight-bearing posteroanterior 45-degree flexion radiograph

• Non–weight-bearing 45-degree flexion lateral view

• Axial view of the patellofemoral joint

• Long-cassette mechanical axis view to evaluate malalignment

Other Modalities

• Magnetic resonance imaging with or without the intra-articular administration of contrast material is performed to assess extent of meniscectomy, degree of articular cartilage damage, and presence of subchondral edema in the involved compartment.

• Technetium bone scanning may indicate stress overload in the involved compartment or overt osteoarthritis.

Indications and Contraindications

The ideal candidate has a history of prior total or subtotal meniscectomy with persistent pain localized to the involved compartment, intact articular surfaces (ideally grade I or II), normal alignment, and a stable joint. Associated pathologic findings, such as malalignment, discrete chondral defects, and ligamentous instability, are not contraindications in an otherwise appropriate candidate because they can be addressed in either staged or concomitant procedures.

In addition to uncorrected comorbidities (malalignment, ligament deficiency, uncorrected localized chondral damage in the involved compartment), contraindications are overt arthroscopic or radiographic arthritic changes (especially associated with femoral condyle or tibial flattening), history of inflammatory arthritis, marked obesity, and previous infection.

Surgical Planning

Concomitant Procedures

Significant limb malalignment, ligamentous instability, or discrete chondral defects can be addressed either before or concomitantly with meniscus transplantation.

Allograft Sizing

Meniscal allografts are size and compartment specific. Preoperative measurements are obtained from anteroposterior and lateral radiographs with magnification markers placed on the skin at the level of the joint line. After radiographic magnification is accounted for, meniscal width is measured on the anteroposterior radiograph from the edge of the ipsilateral tibial spine to the edge of the tibial plateau. Meniscal length is calculated by multiplying the depth of the tibial plateau (as measured on lateral radiographs) by 0.8 for the medial meniscus and 0.7 for the lateral meniscus (Fig. 56-1).

Figure 56-1 Graft sizing on anteroposterior and lateral radiographs.

Meniscal Graft Processing and Preservation

Meniscal allografts are harvested by sterile surgical technique, most commonly within 24 hours of donor asystole. Unlike with fresh osteochondral allografts, cell viability in meniscal allografts does not seem to improve the morphologic or biochemical characteristics of the grafts; thus the most commonly implanted grafts are either fresh-frozen or cryopreserved. The risk of disease transmission is minimized through rigid donor screening, graft culturing, and polymerase chain reaction testing for human immunodeficiency virus. Several tissue banks are evaluating secondary sterilization techniques to further improve the safety of meniscal allograft tissue.

Surgical Technique

Anesthesia and Positioning

On the basis of the surgeon’s, anesthesiologist’s, and patient’s preferences, the procedure can be performed with general, spinal, or regional anesthesia or a combination thereof. The patient is positioned supine on a standard operating room table, with a thigh tourniquet, and the extremity is placed in a standard leg holder allowing full knee flexion or hyperflexion (Fig. 56-2). The posteromedial or posterolateral corner must be freely accessible for inside-out meniscus suturing to be performed.

Figure 56-2 Patient positioning.

Surgical Landmarks, Incisions, and Portals

• Patellar tendon

• Tibial plateau

• Fibular head

Portals and Approaches

See Fig. 56-3 for portals and approaches:

Figure 56-3 Incisions: accessory posteromedial incision (left); inferomedial and inferolateral arthroscopy portals, mini-arthrotomy for meniscal insertion (between portals); accessory incision for concomitant allograft anterior cruciate ligament reconstruction in this patient (inferior).

• Inferomedial portal

• Inferolateral portal

• Additional outflow portals as needed

• Posteromedial or posterolateral approach

• Mini-arthrotomy through ipsilateral side of patellar tendon

Structures at Risk

• Posterolateral approach: peroneal nerve, lateral collateral ligament, popliteus tendon

• Posteromedial approach: saphenous nerve, medial collateral ligament

• Mini-arthrotomy: patellar tendon

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Sep 11, 2016 | Posted by admin in SPORT MEDICINE | Comments Off

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