Matrix-induced autologous chondrocyte implantation (MACI) in the knee
Enea D, Cecconi S, Busilacchi A, Manzotti S, Gesuita R, & Gigante A. Knee Surgery, Sports Traumatology, Arthroscopy. 2011 Aug 12.  [Epub ahead of print] doi: 10.1007/s00167-011-1639-1
Damaged articular cartilage does not spontaneously heal and traditional surgical techniques to repair cartilage have mixed outcomes.  Traditional surgical techniques (e.g., microfracture) cause the formation of an inferior “patch” tissue (fibrocartilaginous tissue) to fill the lesion area.  More advanced surgical techniques (e.g., autologous chondrocyte implantation, matrix-induced autologous chondrocyte implantation [MACI]) lead to a “patch” tissue that shares similar microscopic properties to the surrounding cartilage (for more information about MACI see video below). The purpose of this study was to take a second look at MACI repair tissue several months after the tissue was implanted, and to compare the microscopic properties, the visual appearance of the MACI tissue, and the patient’s knee symptoms.  30 patients (median age = 40.5 years) underwent the MACI procedure and returned for a total of 33 follow-up biopsies (median follow up time = 15 months, 14 asymptomatic / 19 symptomatic knees).  The surgeon recorded patient demographics, knee symptoms, lesion characteristics, and visual appearance. Biopsies were also evaluated to assess the microscopic structure of the repair tissues (e.g., types of tissue present, organization of the cells).  Using a standardized scoring system to judge the visual appearance of the repair, most repairs (~82%) were classified as normal or nearly normal by the surgeon performing the biopsy. While these tissues appeared normal, microscopically they had abnormal structure and cell patterns. The visual appearance and microscopic appearance of the repair tissue were not associated with knee symptoms.  Interestingly, the visual appearance of the MACI tissues was significantly better in patients older than 40 years.
This study is interesting because several months after cartilage repair surgery (MACI) there appears to be no link between the visual or microscopic appearance of the tissue “patch” and patient symptoms.  To further verify this it will be important to assess the quality of repair tissue in studies with more patients and longer-follow-up time. This study suggests that we need to understand that patient symptoms may be unrelated to the status of the repair patch.  If we step back this may not seem unrealistic since there are some patients with osteoarthritis that have little or no symptoms. Furthermore, many of us have probably treated patients with patellofemoral cartilage pathology who have experienced episodes of pain remission.  We need to gain a better understanding of the complex relationship between joint structures and joint symptoms. For some patients, however, surgery will be necessary, unfortunately, the outcomes remain variable.  As clinicians we need to think of other causes of residual symptoms (e.g., biomechanical, psychological) and how we can manage them.
Written by: Nicole Cattano