MENISCAL ALLOGRAFT TRANSPLANTATION

doi:10.1016/S0278-5919(05)70132-0

Clinics in Sports Medicine

Volume 18, Issue 1, 1 January 1999, Pages 93-108

https://doi.org/10.1016/S0278-5919(05)70132-0 Get rights and content

The treatment of meniscal pathology has undergone a dramatic change over the past thirty years. This evolution stems from increased understanding of the function of the human meniscus, and the harmful effects of menisectomy. In the past, the meniscus was believed to be a vestigial remnant of leg muscle⁶⁷; that belief led to the erroneous belief that menisectomy could be performed with little consequence, much like an appendectomy. As late as 1947, Cave,¹⁶ in the Journal of the American Medical Association, advocated complete menisectomy as the preferred treatment for all meniscal tears.

Although early work by individuals such as King and Fairbank²³ indicated the meniscus played an important role in knee function, it has remained poorly understood until roughly the last quarter century. Clinicians currently recognize the value of the meniscus regarding load-bearing, shock absorption, joint stability, joint congruity, and joint nutrition.1, 23 Numerous clinical studies indicate that total and partial menisectomy can result in altered load bearing across the joint, leading to degeneration of the articular cartilage. The integrity of the meniscal cartilage is important to the functional outcome of the anterior cruciate deficient knee.55, 68 An irreparable meniscal tear may be the eliciting factor in the functional decline of the chronically anterior cruciate ligament (ACL) deficient knee.⁵⁵ Recent reports have demonstrated the importance of the meniscus in the acutely ACL reconstructed knee as well.¹⁹ McConville reported increased complaints of pain, swelling, instability, and reduced activity in individuals who underwent meniscal excision at the time of ACL reconstruction compared with those with intact menisci.⁷

This current understanding of the vital role of the meniscus has lead to attempts to restore its function whenever possible. Open and arthroscopic repair, synovial abrasion, fibrin clots, and trephination have all been used in an effort to repair and promote healing of the injured meniscus.17, 36 A subset of patients remains who have undergone or require total or near-total menisectomy for an irreparable tear. The belief that meniscal reconstruction will interrupt or delay the onset of progressive osteoarthrosis in these patients, has lead to the development of meniscal transplantation. In May of 1984, Milachowski performed the first meniscal allograft transplantation at the Munich-GroBhaden University Hospital.⁵³ Since that time, scientific investigators have attempted to use synthetic, autogenous, and allograft substitutes to restore the function of the human meniscus.43, 45 From early total menisectomy, to subtotal and partial menisectomy, to meniscal repair, the treatment of the injured meniscus has now evolved to the development and refinement of meniscal transplantation techniques. Although much has been learned about meniscal transplantation, many important areas of investigation remain.

Section snippets

MENISCAL ANATOMY AND FUNCTION

Successful replacement of the injured meniscus requires an in-depth understanding of its anatomy and function. The lateral meniscus is the more mobile of the menisci. Its loose peripheral fixation allows it to translate up to 11 mm in the anteroposterior plane during knee motion.⁴¹ It is relatively circular in shape and covers approximately 50% of the lateral tibial plateau. The anterior horn attaches to both the ACL footprint and the transverse ligament. The posterior horn attaches to the

IMMUNOLOGY

Both humoral and cell-mediated immune responses may be activated by transplanted allograft tissue, affecting both the rate of incorporation and the strength of the particular graft. Currently, knowledge of the immunologic response to meniscal transplantation remains limited.³ Because articular and meniscal cartilage are relatively acellular and the cellular and major antigenic components of these tissues are protected by an extracellular matrix, these tissues are believed to be “immunologically

ANIMAL STUDIES

Animal studies have consistently demonstrated the feasibility and viability of meniscal transplantation. Arnoczky³ demonstrated that allografts healed to the canine knee capsule at 6 months with a normal cell population and proteoglycan component. Normal histologic microarchitecture resulted from the incorporation of meniscal allograft in another canine model at 8 to 12 months.⁵²

Bylski-Austrow12, 13 used fresh frozen irradiated grafts in a goat model and determined that at 8 months after

GRAFT SELECTION AND PRESERVATION

Graft donors should ideally be younger than 25 years old with a negative history and serologic study for infectious disease. The grafts should be matched for size between the donor and recipient.⁴⁷ Several techniques currently exist for the preservation and sterilization of meniscal allografts. The most commonly used substitutes to date include fresh, frozen, or cryopreserved allografts.25, 54, 56 Brown et al¹⁰ recently reported the use of a collagen meniscal template which produced a

INDICATIONS

The indications for meniscal transplantation are currently evolving. Preoperative variables include the patient's age and activity demands, as well as knee stability, alignment, and the degree of articular wear. Veltri et al⁶⁹ reserved meniscal transplantation for patients with pain associated with early osteoarthrosis of the involved compartment of the knee. They recommend limiting transplantation to patients younger than 45 with a ligamentously stable knee or a knee that will be stabilized by

SIZING

Selecting an appropriately sized graft is a prerequisite for incorporation and function of the allograft meniscus. Ideally, the allograft should match the size of the native meniscus to within 5%.²⁶ Available techniques of sizing include MR imaging, computed tomography (CT), and plain radiography.26, 69 Both MR imaging and CT have been shown to consistently underestimate the size of the true meniscus and recipient site.²⁶ However, Lí Insalata et al,⁴⁹ has demonstrated that plain radiography can

SURGICAL TECHNIQUE

Once the appropriate patient and graft have been selected, several options exist for transplanting the meniscus. Both open and arthroscopically assisted techniques have been described. Garrett²⁷ described a technique using a parapatellar arthrotomy with ipsilateral collateral ligament transection from the femoral origin and subsequent repair of the collateral ligament at the end of the procedure. He also used a tibial tubercle osteotomy in cases of lateral meniscal reconstruction.

In an attempt

REHABILITATION

To date, no standard rehabilitation protocol has been developed for patients who have undergone meniscal transplantation. The postoperative regimen should be designed to protect the allograft tissue. No data currently exist concerning the stresses seen at the attachments of the meniscal horns or at the periphery of the graft when the knee is loaded. It therefore remains debatable as to when weightbearing should begin and how much weight should be initiated at specific intervals. Often the

RESULTS

Determining the results of meniscal transplantation is difficult. Most series have a limited number of patients, short term follow-up, and different outcome measures (Table 1). Many patients also have compounding factors, such as joint deterioration, osteochondral lesions, or ligamentous instability, making the impact of the “isolated” meniscal reconstruction difficult to interpret.⁴³

Current methods of objectively evaluating meniscal reconstruction include MR imaging and second-look

COMPLICATIONS

Few complications regarding meniscal transplantation have been reported in the literature. Most of these adverse outcomes appear to be related to poor patient selection, technical errors, and biologic failures. Milachowski⁵³ reported two soft tissue infections in 22 patients and four patients who developed synovitis, all with lyophilized allografts. Deep infections have also been reported⁵⁴ as well as one case of a suspected immunologic response.³² As in all allograft surgery, disease

FUTURE DIRECTIONS

Although much information has been gained in the field of meniscal transplantation over the past decade, many issues need to be addressed to ensure improved meniscal reconstruction outcomes in the future. The specific indications for meniscal reconstruction remain undefined. The literature to date supports the young, symptomatic individual with little or no associated instability or degenerative disease as the ideal candidate. Cameron and Saha,¹⁵ however, have recently reported encouraging

SUMMARY

Meniscal allograft transplantation remains an investigational procedure. Loss of native meniscal function has been consistently shown to result in the development and progression of degenerative joint disease.1, 23 Allograft reconstruction is a technically feasible and reproducible procedure in both animals and humans with demonstrated incorporation of the transplanted graft with host tissue.1, 53, 54 However, the ultimate success or failure of the meniscal reconstruction cannot be judged

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