The indication for the scaffold implantation, which is widely accepted, is pain after previous meniscectomy. The prophylactic use of the scaffold is still being debated.

Rodkey et al. [11] in a multicentric randomized study, regarding 311 patients with irreparable meniscal tear or pain after previous meniscectomy, demonstrated that the collagen meniscus implant is useful in replacing irreparable or lost meniscal tissue in patients with a chronic meniscal injury. The implant was not found to have any benefit for patients with an acute injury.

In one of our studies [12] about the CMI results at 5 years follow-up, a tendency for a better outcome in patients with acute lesions was observed, and Hirschmann et al. [13] reported that patients who underwent CMI due to prophylactic reasons had a higher Tegner score at one-year follow-up than the others.

Filardo et al. [14] speculated that this dispute could depend on the rapid clinical improvement offered by meniscectomy which makes the benefits of the scaffold implantation less significant in a short time. Probably, the meniscus protective role requires a longer time to be clinically evident. Long-term studies on acute injury will clarify this problem.

For a successful scaffold implantation, the anterior, posterior meniscal horn and peripheral rim should be intact.

The articular cartilage should be conserved or present maximum third-degree lesion according to ICRS classification. However, concomitant treatment of more complex focal cartilage lesions with microfracture, osteochondral scaffold implantation, and chondroabrasion has been reported [15, 16].

The patients must be relatively young and willing to follow the rehab protocol. The knee must be stable and aligned or a ligament reconstruction and/or an osteotomy must be performed.

The contraindications are skeletally immature subjects, previous total meniscectomy, meniscal roots lesions, severe osteoarthritis, allergy to the material of the implant, elderly patients, infection, or inflammatory diseases.

Surgical technique: The first steps are to check arthroscopically the correct indication for the implant and to remove all pathological tissues. Then, a bed is prepared for the CMI and bleeding is obtained from the parameniscal tissues in order to support the meniscal ingrowths. Then, the meniscus defect is measured and the implant is cut 10% longer than the measured area. The completely dry implant is delivered into the joint using a clamp for vascular surgery. The suture is started with an all inside technique and in most cases the suture is completed with the same technique, although in some cases, if necessary, the suture can be completed with an in-out technique. Generally, the stitches are put vertically into the central part of the implant and horizontally at the extremities.

Rehabilitation protocol: During the first weeks after surgery, the patient must wear a knee brace with a progressive range of motion. Complete movement is allowed after 6 weeks. The weight-bearing program is also progressive: in the first weeks, it is partial and becomes complete after 10 weeks. Immediate isometric muscle strengthening exercises are recommended and free activities are not allowed for 6 months.