Cartilage failures. Systematic literature review, critical survey analysis, and definition

While midterm results of matrix-assisted autologous chondrocyte transplantation (MACT) are now available, less attention has been paid to the evaluation of failures of this surgical approach. Aim of this study was to analyse how "failures" are generally defined in cartilage surgery, in order to understand how the survival rate may change according to different definitions of failure.A systematic review on MACT in the knee was conducted to report failure rates as well as different failure definitions in the available literature. Afterwards, we analysed the survival curve at 8.5-year follow-up of a survey of 193 patients treated with MACT. Using different definitions to identify failures, we compared how the survival rate changed according to the different definitions of failure.The systematic review on 93 papers showed that the average failure rate reported on 3,289 patients was 5.2 \% at a mean 34 months of follow-up. However, 41 studies (44.1 \%) did not even consider this aspect, and failures were variously defined, thus generating confusing data that make a meta-analysis or a study comparison meaningless. The failure analysis of the MACT survey showed that the survival curve changed significantly depending on the definition applied; in fact, the failure rate ranged from 3.6 to 33.7 \%. According to a critical literature and survey analysis, we proposed a combined surgical- and improvement-based definition which led to a failure rate of 25.9 \% at midterm/long-term follow-up.Nowadays, failure definitions of cartilage treatments differ in scientific articles, thus generating confusion and heterogeneous data even when applied to the same cohort of patients. While the literature analysis shows a low number of failures, this study demonstrated that if properly addressed with a comprehensive definition, the real failure rate of cartilage surgical procedures in the knee is higher than previously reported. Recognizing failures would give a better understanding and a more realistic prognosis to patients and physicians seeking treatment for cartilage lesions. LEVEL OF EVIDENCE: IV.