Paving the way for future research in autologous chondrocyte implantation: response.

Abstract

which suggested that graft maturation after autol-ogous chondrocyte implantation (ACI) in the knee jointneeds at least 1 year, with ongoing adjustment of the T2relaxation time values compared with native surroundingcartilage, and found no correlation between increasingACI graft maturation and clinical outcomes (InternationalKnee Documentation Committee [IKDC] score).This is a very important study, adding to the studies onevaluating ACI graft maturation in osteochondral lesions.It would have been interesting if the authors—because ofobvious heterogeneity of defect locations as well as seriousmethodological limitations inherent in case series studies(eg, lack of comparative cohort or control group)—couldhave improved their study assessment tools (such as alsousing histological findings or the Short Form–36 [SF-36]questionnaire as secondary outcomes) to determine thecontributing factors that affected clinical outcomes. Mentalfactors, which could be assessed by the SF-36 question-naire, or other variables that are not visible on magneticresonance imaging (MRI), such as inflammation, increasedvascular penetration, and nerve growth, may influenceclinical outcomes. Moreover, the complexity of the kneeinjury and the patient history can make it difficult forany of the used outcome questionnaires to reflect the exactareas that are important to patients.