SIX-YEAR RESULTS OF COLLAGEN MENISCUS IMPLANTS (CMI) EMPHASIZING LOCATION AND AMOUNT OF MENISCUS REMAINING

Abstract

Prospectively, we determined amount of meniscus loss and anatomic location of Collagen Meniscus Implant (CMI) placement after partial medial meniscectomy (PMM). At 1-year relook we determined total meniscus tissue present based on surface area coverage. We correlated percent of meniscus and anatomic location of the original lesion with function and activity levels 6 years after CMI placement. We hypothesized that meniscus amount and anatomic location would influence clinical function and activity levels.

In a prospective randomized controlled multicenter clinical trial (Level of Evidence I), 114 chronic patients (1 to 3 prior PMM on the involved meniscus) 18 to 60 years old underwent partial medial meniscectomy, and then randomly one group received a CMI to fill the meniscus defect. There were 68 PMM only controls and 46 CMI patients. At index surgery, amount and anatomic location of meniscus removed and CMI placement were documented on a standard grid. Locations were categorized as posterior (A), middle (B), or anterior (C) third. A 1-year relook was done on CMI patients, and meniscus surface area coverage was measured. Patients were followed clinically for a minimum of two years and subjectively annually thereafter. Average follow-up was 69 months (range, 24 to 92). All patients completed validated questionnaires including Lysholm and Tegner scores to assess function and activity.

For CMI patients, 29 had lesions which included posterior and middle thirds (AB), and 17 had lesions involving all three zones (ABC). Lysholm scores were significantly higher in patients with AB lesions (81) compared to ABC lesions (71), p=0.046. AB lesion patients also had significantly higher Tegner index (0.70) than ABC lesion patients (0.22), thus AB patients regained more of their lost activity, p=0.049. Comparing all patients with > 60% meniscus surface area coverage, CMI patients had significantly higher Tegner index compared to controls (0.59 vs. 0.30), p=0.036. No differences between treatment groups were seen in patients with < 60% meniscus surface area coverage. When comparing 24 month to final follow-up values, controls had no change for Lysholm (p=0.13) or Tegner (p=0.39) scores, but CMI patients improved significantly over time for both Lysholm (p=0.02) and Tegner (p=0.04) scores.

Zones of meniscus involvement influenced clinical outcomes at 6 years in CMI patients. Those whose lesions extended into all three zones did worse than those with lesions in posterior and middle zones only. Patients with successful CMI procedures yielding > 60% meniscus surface area coverage were significantly better than PMM only controls for both clinical function and activity levels. Noteworthy, CMI patients continue to improve over time for clinical function and activity levels, but PMM controls do not.