Page 18 - 2020 ISAKOS Newsletter Volume I

CURRENT CONCEPTS
Collagen Meniscus Implant (CMI): Features, Techniques, and Clinical Outcomes
The loss of meniscal tissue as a result of injury, surgery, or degenerative processes alters the biomechanical function of the knee and has been associated with an increased risk of osteoarthritis over time. Therefore, in the past 30 years, the approach to the treatment of meniscal tears has shifted to meniscus-sparing or replacing strategies involving meniscal suturing, scaffolds, and allograft. The Collagen Meniscus Implant (CMI, Ivy Sports Medicine GmbH, Gräfelfing, Germany) is the first biological scaffold to be used for the treatment of partial meniscal deficiencies. The aim of this Current Concept article is to summarize the characteristics, surgical techniques, clinical results, and the MRI findings associated with the CMI scaffold.
Basic Science and Histological Behavior
The CMI is a highly porous scaffold (not a prosthetic device) that is made up of type-I collagen fiber from purified bovine Achilles tendon. The scaffold is 7.5 cm long and 1 cm wide and is designed to be trimmed and adapted to the meniscal defect during surgery. The CMI was developed with the purpose to develop a tissue-engineered meniscus. Animal studies have provided extensive knowledge about the histological behavior of the CMI implant. The cellular response has been shown to consist of both angiogenic and resorptive levels by 6 weeks that disappeared after a year following scaffold implantation. At 17 months, the implants appeared to have been largely replaced by more organized and integrated tissue resembling native tissue. However, remaining fragments of the scaffold continued along a path of begin incorporation into the surrounding tissue. Therefore, animal studies have demonstrated a correlation between MRI findings and histological observations.
Indication and Surgical Procedures
The CMI is indicated for the treatment of irreparable meniscal tears in patients with meniscal tissue loss of >25%, intact anterior and posterior horn attachments, and an intact meniscal rim over the entire circumference of the involved meniscus. Contraindications to the use of the CMI include an age of >55 years, Ahlbäck grade >1 degenerative changes on radiographs, osteonecrosis of the knee, Outerbridge grade-IV chondral lesions, PCL insufficiency, inflammatory arthritis, systemic or local infection, allergies to collagen or bovine products, obesity, and pregnancy. If ACL insufficiency or malalignment of the lower limb are present, concomitant correction of the defect is mandatory.
The scaffold is placed arthroscopically. Anteromedial and anterolateral knee portals are established, and a standard diagnostic arthroscopic procedure is performed. In acute cases, meniscal suture repair should be done whenever possible. If repair is not possible and in cases of chronic tears, debridement of damaged meniscal tissue is performed until healthy tissue is reached. The prepared site should extend into the vascular zone of the meniscus in order to guarantee an adequate blood supply.
Introduction
Stefano Zaffagnini, MD, Prof.
II Orthopaedics and Traumatological Unite, IRCCS Rizzoli Orthopaedic Institute, Bologna, Italy; Dipartimento di Scienze Biomediche e Neuromotorie DIBINEM, University of Bologna, ITALY
Giacomo Dal Fabbro, MD
II Orthopaedics and Traumatological Unite, IRCCS Rizzoli Orthopaedic Institute, Bologna, ITALY
Gian Andrea Lucidi, MD,
II Orthopaedics and Traumatological Unite, IRCCS Rizzoli Orthopaedic Institute, Bologna, ITALY
Luca Macchiarola, MD ITALY,
II Orthopaedics and Traumatological Unite, IRCCS Rizzoli Orthopaedic Institute, Bologna, ITALY
Alberto Grass, MD
II Orthopaedics and Traumatological Unite, IRCCS Rizzoli Orthopaedic Institute, Bologna, ITALY
Meniscal tears are among the most common injuries treated by orthopaedic practitioners, and meniscectomy is still commonly performed because of its good short-term results and the severity of meniscal tears. The menisci have multiple functions: they are very important for shock absorption and force transmission during weight-bearing, they help in nutrition and lubrication of the joint, they have some role in proprioception, and they function as secondary stabilizers of the knee.
16 ISAKOS NEWSLETTER 2020: VOLUME I