Purpose: As a one-step surgical procedure, microfracture is frequently considered to be technically easier and associated with less postoperative morbidity than autologous chondrocyte implantation (ACI), which involves both arthrotomy and arthroscopy and therefore safety was assessed in patients with symptomatic cartilage lesions of the knee treated with characterized chondrocyte implantation (CCI) or microfracture.

Methods: CCI (n=57) was compared to microfracture (n=61) in patients with grade III–IV symptomatic cartilage defects of the femoral condyles in a Phase III, prospective, multi-center, randomized, controlled trial. Safety assessments included adverse events (AEs), physical examination, vital signs, hematology and clinical chemistry.

Results: At 18 months post-surgery, similar proportions of patients experienced AEs in the CCI (88%) and microfracture (82%) groups; 67% and 59%, respectively, experienced AEs considered treatment related. The AE profile was generally similar between groups, with no significant difference for hypertrophy, although significantly more CCI-treated patients had joint swelling (19% versus 4.9%; p=0.022) and treatment-related joint crepitation (12% versus 1.6%; p=0.028). Although the proportion of patients with severe AEs was similar for CCI (12%) and microfracture (13%), slightly more microfracture-treated patients experienced serious (life-threatening or requiring hospitalization) AEs (13% versus 8.8%). No patients discontinued due to AEs or died during the study.

Conclusion: Contrary to general opinion, the two-step CCI procedure, involving arthroscopy followed by arthrotomy, has a similar safety profile to that of microfracture, a one-step arthroscopic procedure, for treating cartilage lesions of the knee.