Local application of a collagen type I/hyaluronate matrix and growth and differentiation factor 5 influences the closure of osteochondral defects in a minipig model by enchondral ossification

This pilot study evaluated the effect of growth and differentiation factor-5 (rhGDF-5) combined with a collagen type I/hyaluronate matrix (c/h) on osteochondral defect repair in a minipig model. Defects created in both medial femoral condyles of 20 minipigs were treated with c/h (n = 10), c/h + rhGDF-5 (n = 10) or were left empty. After 3 and 12 months, five animals of each group were sacrificed. Evaluation included macroscopic and histological scoring and quantitative histomorphometry of synthesized bone. C/h and c/h + rhGDF-5 treatment increased trabecular bone formation in the upper third of the defect compared to empty controls, showing significance for c/h + rhGDF-5 (p = 0.05) but not between c/h and c/h + rhGDF-5 treatment. Cartilage regeneration and macroscopic outcome were not improved by c/h or c/h + rhGDF-5 treatment. Since c/h remnants were seen even one year postoperatively in the defect, possibly inhibiting further bone and cartilage healing, other matrices in combination with rhGDF-5 may provide further improvement in osteochondral defect treatment.