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5 Points on Meniscal Allograft Transplantation

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Meniscus tears are common in the young, athletic patient population. In the United States alone, approximately 700,000 meniscectomies are performed annually.1 Given discouraging long-term clinical results following subtotal meniscectomy in young patients, meniscal repair is preferred whenever possible.2 Despite short-term symptom relief if subtotal meniscectomy is required, some patients often go on to develop localized pain in the affected compartment, effusions, and eventual development of osteoarthritis. In such patients with symptomatic meniscal deficiency, meniscal allograft transplantation (MAT) has yielded excellent long-term functional outcomes.3-5 Three recently published systematic reviews describe the outcomes of MAT in thousands of patients, noting positive outcomes in regard to pain and function for the majority of patients.6-8 Specifically, in a review conducted by Elattar and colleagues7 consisting of 44 studies comprising 1136 grafts in 1068 patients, the authors reported clinical improvement in Lysholm Knee Scoring Scale score (44 to 77), visual analog scale (48 mm to 17 mm), and International Knee Documentation Committee (84% normal/nearly normal, 89% satisfaction), among other outcomes measures. Additionally, the complication (21.3%) and failure rates (10.6%) were considered acceptable by all authors. The purpose of this article is to review indications, operative preparation, critical aspects of surgical technique, and additional concomitant procedures commonly performed alongside MAT.

1. PATIENT SELECTION

When used with the proper indications, MAT offers improved functional outcomes and reduced pain for patients with symptomatic meniscal deficiency. When evaluating a patient for potential MAT, it is imperative to evaluate past medical history and past surgical procedures. The ideal MAT candidate is a chronologically and physiologically young patient (<50 years) with symptomatic meniscal deficiency who does not have (1) evidence of diffuse osteoarthritis (Outerbridge grade <2), including the absence of significant bony flattening or osteophytes in the involved compartment; (2) inflammatory arthritis; (3) active or previous joint infection; (4) mechanical axis malalignment; or (5) morbid obesity (Table). Long-leg weight-bearing anterior-posterior alignment radiographs are important in the work-up of any patient being considered for MAT, and consideration for concomitant or staged realignment high tibial osteotomy (HTO) or distal femoral osteotomy (DFO) should be given for patients in excessive varus or valgus, respectively. Although the decision to perform a realignment osteotomy is made on a patient-specific basis, if the weight-bearing line passes medial to the medial tibial spine or lateral to the lateral tibial spine, HTO or DFO, respectively, should be considered. Importantly, MAT is not typically recommended in the asymptomatic patient.9 Although some recent evidence suggests MAT may have chondroprotective effects on articular cartilage following meniscectomy, there is insufficient long-term outcome data to support the use of MAT as a prophylactic measure, especially given the fact that graft deterioration inevitably occurs at 7 to 10 years, with patients having to consider avoiding meniscus-dependent activities following transplant to protect their graft from traumatic failure.10,11

Table. Summary of Indications and Contraindications for Meniscal Allograft Transplant (MAT)

Indications

Contraindicationsa

Patients younger than 50 years old with a chief complaint of pain limiting their desired activities

Diffuse femoral and/or tibial articular cartilage wear

Body mass index <35 kg/m2

Radiographic evidence of

arthritis

Previous meniscectomy (or non-viable meniscus state) with pain localized to the affected compartment

Inflammatory arthritis conditions

Normal or correctable coronal and sagittal alignment

MAT performed as a prophylactic measure in the absence of appropriate symptoms is highly controversial

Normal or correctable ligamentous stability

Normal or correctable articular cartilage

Willingness to comply with rehabilitation protocol

Realistic post-surgical activity expectations

aContraindications for MAT are controversial, as the available literature discussing contraindications is very limited. This list is based on the experience of the senior author.

Long-term prospective studies have shown high graft survival and predominantly positive functional results after MAT. Age indications have expanded, with 1 recent study reporting 6% reoperation rate and zero failures in a cohort of 37 adolescent MAT patients.12 High survival rates hold even among an athletic population, where rates of return to play after MAT have been reported to be >75% for those competing at a high school level or higher.13 In an active military population, <2% of patients progressed to revision MAT or total knee arthroplasty at minimum 2-year follow-up, but 22% of patients were unable to return to military duty owing to residual knee limitations.14 In this series, tobacco use correlated with failure, whereas MAT by high-volume, fellowship-trained orthopedic surgeons decreased rates of failure.

2. GRAFT SELECTION

In preparation for MAT, accurate measurements must be taken for appropriate size matching. Several measurement techniques have been described, including using plain radiographs, 3D computed tomography (CT), and magnetic resonance imaging (MRI).15-18 There is limited data regarding the consequences of an improperly sized donor meniscus; however, an oversized lateral meniscus has been shown to increase the contact forces across the articular cartilage.19 Additionally, an undersized allograft may result in normal forces across the articular cartilage but greater forces across the meniscus.19

When sizing the recipient knee for MAT, accurate width and length measurements are critical. The most common technique used today includes measurements using anteroposterior and lateral radiographic images as described by Pollard and colleagues.15 The width of the meniscus is determined by the distance between 2 vertical lines perpendicular to the joint line, 1 of them tangential to the margin of the tibia metaphysis and the other between the medial and lateral tibial eminence in both knees (Figures 1A,1B). The length of the meniscus is measured on a lateral radiograph. A line is drawn at the level of the articular line between the anterior surface of the tibia above the tuberosity and a parallel line that is tangential to the posterior margin of the tibial plateau. Percent corrections are performed for these dimensions as described in previous publications.

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Other techniques have been described to obtain accurate measurements of the recipient knee. For example, obtaining an MRI of the contralateral knee may provide a reproducible method of measuring both the width and length of the medial and lateral menisci.20 CT has been used to measure the lateral meniscus independently, and it has been shown to exhibit less error in the measure of the tibial plateau when compared with X-rays.18 Both CT and MRI are more expensive than simple radiographs, and CT exposes the patient to an increased amount of radiation. Current evidence does not support standard use of these advanced imaging modalities for meniscal sizing.

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