Arthroscopic meniscal transplantation: Bone plug

OVERVIEW

Chapter synopsis

Arthroscopic meniscal allograft transplantation (MAT) has the potential to relieve pain and increase knee function within a subset of patients with non-functional menisci or after subtotal or total meniscectomy. The arthroscopic bone plug technique allows a surgeon to match the allograft to the patient’s specific anatomy and to perform concomitant procedures while achieving the benefits of minimally invasive surgery. This chapter outlines the indications, contraindications, and surgical technique required to optimize the chances of a successful outcome.

Important points

Arthroscopic MAT has been shown to provide pain relief and increased function.
Ideal candidates should be younger than 50 years of age.
Articular cartilage damage must be minimal (Outerbridge grade I or II).
Mechanical alignment and joint stability must be optimal or able to be corrected at the time of MAT.
Bone plugs allow for allograft fixation that precisely matches the patient’s own anatomy.

Clinical and surgical pearls

If present, mechanical malalignment and instability must be addressed. Osteotomies and ligament reconstructions can be performed concomitantly with the bone plug technique.
Use different-appearing sutures to avoid confusion.
Mark the graft with the correct orientation to avoid any confusion should twisting or flipping occur during graft reduction.
Mark the superior edge of the bone plug to allow for proper depth placement.
Perform an adequate notchplasty and flattening of the tibial eminence to allow for visualization of the posterior horn socket.

Clinical and surgical pitfalls

Failure to address mechanical malalignment and/or concomitant pathology will result in failure of MAT, even with an anatomic reconstruction.
If possible, leave a peripheral rim of meniscal remnant tissue to help avoid graft extrusion.
Avoid meniscal extrusion by first securing the allograft to the posterior horn then to the anterior horn, followed by the body to the capsule.

Video available

: Arthroscopic meniscus transplantation

The meniscus plays an important role in load transmission, shock absorption, stability, articular cartilage nutrition, and lubrication within the knee joint. Removal of this important anatomic structure results in eventual joint degeneration. Because of this, the standard of care for meniscal injuries has focused on meniscal preservation and repair techniques in an effort to safeguard joint cartilage. However, in some situations, these techniques are not feasible, and total or subtotal meniscectomy is necessary. Meniscal allograft transplantation (MAT) is a viable option in a subpopulation of these patients.

Many different techniques are used for MAT, and none has been shown to be definitively superior to the others. ^, The senior author (T.D.) advocates an all-arthroscopic technique with the use of individual bone plugs for both medial and lateral MAT for the following reasons:

1.
Arthroscopic technique allows for anatomic placement of both meniscal horns, which minimizes meniscal extrusion and maximizes hoop stresses, presumably leading to enhanced knee kinematics.
2.
Bone plugs can be adapted to a patient’s individual anatomy.
3.
Concomitant surgical procedures can be performed at the time of MAT to address ligamentous instability, mechanical malalignment, and cartilaginous defects.
4.
An all-arthroscopic technique is minimally invasive and can be used in an outpatient setting.

Preoperative considerations

Indications

Success of MAT hinges on proper patient selection. Prior total or subtotal meniscectomy and pain with activity localized to the meniscal deficient compartment is the most common indication. Ideally, patients should be younger than 50 years, have minimal Outerbridge changes to their articular cartilage (grade I or II), and possess an optimal mechanical environment from a stability and alignment perspective. ^, Patients who do not fit all these criteria at the time of clinical presentation should not be precluded from undergoing MAT. There has been initial data suggesting those older than 50 may demonstrate improvement in functional outcomes but have a higher failure rate compared to a younger cohort. Instead, a detailed single or staged surgical plan should be formulated to make sure that all knee abnormalities are addressed and that native knee anatomy, stability, and kinematics are restored, thereby giving the meniscal allograft the best chance of incorporation at the time of implantation.

Though beyond the scope of this chapter, concomitant procedures performed with MAT include anterior cruciate ligament (ACL) reconstruction, revision ACL reconstruction, posterolateral corner (PLC) reconstruction, osteotomies of the distal femur and proximal tibia to correct for coronal plane malalignment, and any number of procedures to address focal, cartilaginous defects (e.g., autologous chondrocyte implantation [ACI], osteochondral autograft transplantation surgery [OATS], osteochondral allograft [OCA] transplantation). Patients need to be willing to comply with postoperative rehabilitation protocols and should be thoroughly counseled that the intent of the MAT is to restore knee function and decrease pain, not return patients to their peak, preinjury level of activity, especially high-performance athletes.

Contraindications

Patients should not undergo MAT if they are asymptomatic; possess overt signs of joint degeneration on plain radiographs (joint space narrowing, osteophytes, subchondral cysts, sclerosis); demonstrate diffuse, high-grade cartilage changes (Outerbridge grade III or IV) on magnetic resonance imaging (MRI); or have fixed sagittal or coronal plain deformities. ^, In addition, muscular atrophy, history of knee sepsis, history of inflammatory arthritis, and conditions such as immune disorders, diabetes mellitus, gout, and marked obesity are relative contraindications. Last, but nonetheless important, patients who are not willing to comply with the postoperative rehabilitation or who seek unrealistic outcomes are not ideal candidates for MAT.

Graft sizing

Meniscal allografts must be appropriately sized to prevent overstuffing of the joint leading to stiffness or, conversely, to prevent undersizing. Undersizing may lead to poor joint surface coverage and increased forces across the graft, predisposing for MAT failure. The senior author has consistently used one tissue bank over the course of his career and receives a size-matched meniscal allograft based on the preoperative MRI scan supplied to the tissue bank. Alternatively, measurements made from calibrated plain films have been used.

Imaging

A standard set of weight-bearing plain radiographs should be obtained for all patients being evaluated for MAT and should include the following views: 45-degree posteroanterior (PA), anteroposterior (AP) in full extension, 45-degree lateral, Merchant views of the patella, and full-length mechanical axis films of the lower extremity. Magnification markers placed on the skin are important for sizing of the meniscal allograft before surgery. CT scan has a limited role in preparing for MAT surgery except when a revision ACL procedure needs to be performed and there is concern for lysis around the bone tunnels. MRI is useful to assess the extent of meniscal damage, the integrity of the articular cartilage and subchondral bone, and to identify ligamentous injury. Bone scans have been described in the literature for differentiation of compartment stress overload from overt arthritis, but they are rarely ordered in the clinical setting of patients being evaluated for MAT.

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