In the intra-group analysis , while microfracture showed moderate to good degree of cartilage repair in nearly 50 % of the patients ( 47 % at 6 months to 50 % at 2 years ; n.s. ) , microfracture/biomembrane maintained an equivalent degree of repair up to 2 years ( 88 % at 6 months to 75 % at 2 years ; n.s. ) .