In Vitro Analysis of Micronized Cartilage Stability in the Knee: Effect of Fibrin Level, Defect Size, and Defect Location.

Purpose: The purpose of the study is to assess the stability of a dehydrated cartilage allograft combined with platelet-rich plasma sealed with fibrin glue within trochlear and medial femoral condyle (MFC) chondral defects in a cadaver knee model.

Methods: Defects were made in the trochlea (20, 25, and 30 mm) and MFC (15, 20, and 25 mm) of 6 cadaver specimens. Allograft was applied utilizing 2 different techniques: (1) proud in which the fibrin level extends beyond surrounding cartilage and (2) recessed in which the fibrin level is even with or below the surrounding cartilage. The knees were cycled by using a continuous passive motion machine through a range of motion. Defects were assessed for superficial delamination and displacement of the allograft. This was quantified as the percentage of surface delamination and/or exposed bone. Comparisons were made with regard to defect size, location, and fill.

Results: In both the MFC and trochlea, proud application resulted in an increased rate of fibrin delamination. In the trochlea, an average of 38% delamination was detected in the recessed 20-mm defect compared with 70% in the proud 30-mm defect (P < .05). This effect was increased with increasing defect size. In the MFC, mean delamination of 43% and 28% exposed bone was noticed in the proud 15-mm defect compared with 95% delamination and 71% exposed bone at 25 mm. In 82% of specimens, displacement and/or delamination occurred within the first 15 minutes of testing.

Conclusions: Increased defect size in both the trochlea and femoral condyle, as well as a proud construct application, were associated with significant delamination and displacement of the allograft/fibrin construct.

Clinical Relevance: Proud application of allograft increases the likelihood of fibrin delamination and graft displacement in both trochlear and MFC defects. This effect is increased with increasing defect size. These data may support limiting range of motion immediately after an allograft procedure.