Meniscal Allograft Transplantation

Christopher I. Ellingson MD

Jon K. Sekiya MD

Christopher D. Harner MD

History of the Technique

The menisci’s role in load transmission and stability in the knee has been well documented since Fairbank’s important work in 1948.¹^,²^,³^,⁴^,⁵^,⁶^,⁷ Meniscal injuries that result in damage or loss of the meniscus alter knee biomechanics and lead to degenerative changes of the knee.⁷^,⁸^,⁹^,¹⁰^,¹¹ Situations in which a partial or total meniscectomy are required have posed a difficult management issue, especially in young active patients. While meniscal allograft transplantation has emerged over the past 20 years as a viable treatment option for these patients, the surgical techniques continue to be refined.

Milachowski performed the first isolated meniscal allograft transplant in 1984 and reported his results in 22 patients with second look arthroscopy performed at 14 months.¹² Garrett¹³ used an early open technique for meniscal transplantation with takedown of the MCL with a piece of bone off the femur. Secondary to the soft tissue trauma associated with open techniques, the use of mini-arthrotomies and arthroscopic methods are now the procedures of choice for meniscal allograft transplantation.

Meniscal allografts are available fresh, cryopreserved, fresh-frozen, or freeze-dried. Most meniscal allografts implanted today are fresh-frozen or cryopreserved. The use of fresh grafts is logistically difficult as they can be stored for only 7 days, allowing inadequate time for serological testing and sizing of grafts. The use of freeze-dried grafts is not recommended secondary to alterations in the biomechanical properties and size of these grafts. Cryopreservation of grafts maintains cell viability between 10% to 40%, but donor cell viability has not shown any clinical advantage and these cells are quickly replaced by host cells.¹⁴ Fresh-frozen allograft preservation is simpler and more inexpensive than cryopreservation. The lack of cell viability in fresh-frozen grafts has not appeared to affect allograft survival and meniscal transplantation outcomes. Meniscal allograft sizing can be performed utilizing computed tomography (CT), magnetic resonance imaging (MRI), plain radiographs, or direct measurement. Most surgeons and tissue banks use the consistent relationship between plain radiographic landmarks and meniscal size for sizing allografts.¹⁵ Shaffer et al.¹⁶ evaluated MRI for allograft sizing and found only 35% measured to within 2 mm and there was not a significant difference when compared to plain radiographs.

Indications and Contraindications

Meniscal transplant in the meniscus-deficient knee should be considered only after nonoperative treatment modalities have failed to relieve symptoms or prevent progression of joint space narrowing. These nonoperative modalities include unloading braces, nonimpact activity modification, and pharmacological measures. An exception to this guideline is in patients with combined anterior cruciate ligament (ACL) and medial meniscus deficient knees who exhibit significant anteromedial rotatory instability (AMRI). In these select patients earlier intervention with a combined ACL reconstruction and medial meniscal transplantation may improve stability, ACL graft survival, and clinical outcome.⁴^,⁷^,¹⁷^,¹⁸^,¹⁹^,²⁰

Indications for meniscal transplant are patients under age 40 (upper limits of 50 in select cases) with an absent or nonfunctioning meniscus. These patients should have pain localized to the involved compartment associated with activities of daily living or sports. Mechanical alignment of the involved extremity must be normal and articular cartilage changes limited to Outerbridge grade I or II in the involved compartment.

Contraindications include age >50, Outerbridge grade IV articular cartilage changes, bony architectural changes (osteophytes), and significant varus/valgus malalignment or knee instability (unless addressed concurrently with an additional procedure).

Preoperative evaluation includes inspection of stance and gait, knee range of motion, joint line palpation, muscle strength, presence or absence of effusion, and ligamentous stability. Radiographs should be obtained using radiographic markers to include weight bearing posterior-anterior 45-degree flexion, merchant, and non–weight bearing lateral knee films. Long leg alignment films allow objective evaluation for varus/valgus malalignment. MRI can be used as an adjunct to provide information regarding the hyaline cartilage, subchondral bone, and menisci. Finally, a diagnostic arthroscopy can define the extent of the meniscal deficiency and arthrosis, but this adds the morbidity of an additional surgical procedure.

Surgical Techniques

Medial Meniscal Transplantation

The patient is positioned supine on a radiolucent table. After induction of general anesthesia via endotracheal tube, an exam under anesthesia is performed to document knee stability and range of motion. A nonsterile tourniquet is then placed about the patient’s proximal thigh. A sandbag is taped to the table on the ipsilateral side transversely so as to allow the foot of the surgical leg to rest against it and hold the knee flexed. Additionally, a post is placed along the lateral aspect of the affected thigh, thereby allowing hands-free knee flexion and positioning during the case. After sterile prepping and draping, the medial and lateral borders of the patellar tendon are identified and marked along with standard arthroscopy portals. The incision for a posteromedial approach to the knee is drawn with a skin marker. Diagnostic arthroscopy is then performed to document the degree of meniscus deficiency and condition of the articular cartilage in the involved compartment. Once the diagnostic arthroscopy confirms the appropriateness of meniscal transplant the allograft is thawed and reconstituted in antibiotic solution according to standard protocol. We may use a femoral distractor positioned across the knee joint to provide valgus stress in order to open the medial compartment for meniscal debridement and graft passage. Arthroscopic debridement of the remaining native meniscus is performed to expose a remaining bleeding rim of 1 to 2 mm. This bleeding rim of native meniscus is left as a vascular source to aid in graft healing.

Only gold members can continue reading. Log In or Register to continue