Meniscal allograft transplants and new scaffolding techniques

Abstract

Clinical management of meniscal injuries has changed radically in recent years. We have moved from the model of systematic tissue removal (meniscectomy) to understanding the need to preserve the tissue.Based on the increased knowledge of the basic science of meniscal functions and their role in joint homeostasis, meniscus preservation and/or repair, whenever indicated and possible, are currently the guidelines for management.However, when repair is no longer possible or when facing the fact of the previous partial, subtotal or total loss of the meniscus, meniscus replacement has proved its clinical value. Nevertheless, meniscectomy remains amongst the most frequent orthopaedic procedures.Meniscus replacement is currently possible by means of meniscal allograft transplantation (MAT) which provides replacement of the whole meniscus with or without bone plugs/slots. Partial replacement has been achieved by means of meniscal scaffolds (mainly collagen or polyurethane-based). Despite the favourable clinical outcomes, it is still debatable whether MAT is capable of preventing progression to osteoarthritis. Moreover, current scaffolds have shown some fundamental limitations, such as the fact that the newly formed tissue may be different from the native fibrocartilage of the meniscus.Regenerative tissue engineering strategies have been used in an attempt to provide a new generation of meniscal implants, either for partial or total replacement. The goal is to provide biomaterials (acellular or cell-seeded constructs) which provide the biomechanical properties but also the biological features to replace the loss of native tissue. Moreover, these approaches include possibilities for patient-specific implants of correct size and shape, as well as advanced strategies combining cells, bioactive agents, hydrogels or gene therapy.Herein, the clinical evidence and tips concerning MAT, currently available meniscus scaffolds and future perspectives are discussed. Cite this article: EFORT Open Rev 2019;4 DOI: 10.1302/2058-5241.4.180103.

Keywords: meniscal repair; meniscectomy; meniscus allograft transplantation (MAT); partial meniscus replacement; scaffold; tissue engineering and regenerative medicine.

Fig. 1

(a) Lateral meniscus of a right knee; in blue is demonstrated a radial cut; (b) light optical amplification of a radial cut for ultra-structure evaluation; (c) and (d) the density of collagen network is visible; (e) schematic drawing of meniscus vascularization on the sagital view.

Fig. 2

(a) Cryopreserved lateral meniscus graft prepared with bone slot and a suture in the junction of the posterior segment to the mid-body to assist in introducing the graft in the joint; (b) Preparation of a fresh meniscus graft (anterior and posterior horns as well as top side are marked); (c) soft tissue only allograft with all the marks and the suture to assist introduction within the joint.

Fig. 3

(a) Arthroscopic view of a posterior longitudinal peripheral tear of a lateral meniscus transplant 3 years after implantations; (b) all-inside suture; (c) knot tying; (d) stable suture.

Fig. 4

(a) Debridement and trephination of the peripheral meniscus rim to enhance healing prior to scaffold implantation; (b) measurement of the defect; (c) cutting of the scaffold with slight oversizing; (d) suturing the scaffold with all-inside technique.

Fig. 5

(a) Frontal and (b) lateral MRI view of lateral ACTIFIT (yellow circle; red arrows) with morphologic Genovese Grade 3 and signal intensity grade 2 after 5 years’ implantation.

Fig. 6

(a) MRI of a medial ACTIFIT extrusion (red arrows between thin blue lines) with morphologic Genovese Grade 3 and signal intensity grade 2 after 5 years’ implantation. (b) 3-D reconstruction of the morphology of the implanted ACTIFIT.

Fig. 7

(a) Arthroscopic view of an ACTIFIT 2 years after implantation (the colour and texture are very different than the native meniscus); (b) haematoxylin and eosin stain (H&E) histology of ACTIFIT biopsy showing increased neovascularization and paucity of fibrochondrocites when compared to native meniscus. Source: Courtesy of Dr. Pedro Pessoa and Dr. Manuel Virgolino.

Fig. 8

A silk fibroin scaffold for meniscus tissue engineering applications.

Fig. 9

(a) and (b) MRI axial views showing meniscus tear dislocated to the meniscotibial recess (white arrows); (c) frontal MRI view of the same lesion with the meniscus fragment contoured in green (yellow arrow); (d) 3-D MRI-based image showing the tear and enabling use for rapid prototype scaffold printing.