Replacement of the meniscus with a collagen implant (CMI).

Objective: Replacement of an almost completely absent medial meniscus with a collagen implant (CMI), reconstruction of form and function of the medial meniscus, delay of the development of arthrosis deformans.

Indications: Subtotal degenerative or traumatic loss of the medial meniscus, stable meniscal periphery, stable anterior and posterior meniscal insertions, joint with stable ligaments.

Contraindications: Complete loss of the medial meniscus. Untreated knee ligament instability. Extreme varus deformity. Extensive cartilaginous damage, i.e., levels IV and VI as described by Bauer and Jackson. Advanced unicompartmental or generalized arthrosis. Replacement of the lateral meniscus.

Surgical Technique: Standard anterior arthroscopy portals. Resection of the medial meniscus leaving a complete and stable outer rim. Revitalization of the periphery to promote healing. Measurement of defect size. Insertion and fixation of the CMI with nonresorbable suture material in inside-out technique.

Postoperative Management: Postoperative knee brace with limited motion in extension/ flexion of 0/0/60 degrees until week 4, 0/0/90 degrees until week 6. Continuous passive motion within the limits of motion from the 1st postoperative day, actively assisted physiotherapy. No weight bearing for 6 weeks, then increased weight bearing for 2 weeks until full weight bearing is achieved. Cycling can commence from 3 months postoperatively. Full sporting activity after 6 months.

Results: 60 patients (19-68 years, average 41.6 years) with subtotal loss of the medial meniscus and varus morphotype were treated from January 2001 to May 2004 as part of a prospective, randomized, arthroscopically controlled study. The sample consisted of 30 patients with high tibial valgus osteotomy combined with implantation of a CMI, and 30 patients with valgization correction osteotomy only. The CMI had to be removed from one patient because of a dislocation. Evaluation on the Lysholm Score, IKDC (International Knee Documentation Committee), and subjective pain data revealed only slight, nonsignificant differences for 39 patients after 24 months (CMI and correction n = 23; correction only n = 16). The chondroprotective effect of the CMI in the long term remains to be seen.