Meniscal allograft transplantation: Bridge-in-slot technique

OVERVIEW

Chapter synopsis

This chapter summarizes the indications, 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 an 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.
If possible, preserve a 2-mm peripheral rim of meniscal tissue to facilitate capsular repair and potentially reduce graft extrusion.
Use the appropriate varus or valgus stress with hyperflexion followed by extension of the knee to reduce the transplanted graft 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. ^, Recognition of these consequences has led to a strong commitment within the orthopedic community to perform meniscus-sparing interventions. However, there are many cases in which meniscal preservation is not possible. In carefully selected meniscus-deficient patients, meniscal allografts can restore nearly normal knee anatomy and biomechanics, providing excellent pain relief and improved function.

Several techniques exist for meniscal allograft transplantation (MAT), including soft-tissue fixation, bone plugs, a keyhole technique, and a dovetail technique. We prefer the bridge-in-slot technique 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

History

It is essential to elicit a thorough history, including the causative mechanism, associated injuries, and prior treatments. Previous 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
Effusion
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

Radiography

Weight-bearing anteroposterior radiograph in full extension
Weight-bearing posteroanterior flexion radiograph (Rosenberg view)
Non–weight-bearing 45-degree flexion true lateral view
Axial view of the patellofemoral joint
Long-cassette mechanical axis hip-to-ankle view to evaluate malalignment

Magnetic resonance imaging

Magnetic resonance imaging (MRI)—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.

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