Autologous cartilage implantation (ACI) is a new medical alternative that especially benefits for patients who have a damaged cartilage. The goal of ACI is to provide the patient with a durable, load bearing functional joint surface by the repair of articular carticular with both biomechanical and histologic characteristics comparable to normal articular cartilage. There are two stages involved in this ACI procedure. First, some health cartilage cells are collected from the patient’s knee. Then, these biopsytissue are sent to a special laboratory to grow for weeks and transplant back to the patient’s damaged region for new cartilage regeneration. One of the advantages of ACI is the usage of the patient’s own cells could reduce the chances of infection. Besides, ACI has the ability to restore hyaline-like articular cartilage.

ACI is an advanced, cell-based orthobiological technology; however the quality of this treatment is still not very well determined. In this article, “Autologous Chondrocyte Implantation: Superior Biologic Properties of Hyaline Cartilage Repairs,” by Henderson I, Lavigne P, Valenzuela H, and Oakes B. (could be downloaded from https://webfiles.berkeley.edu/wincheung/shared/ ), the properties and qualities of ACI were tested and analyzed. The authors focused on three points. First, the different effects resulted from cartilage repairs of different tissue types in terms of stiffness and outcome. Second, the correlation between the anatomic locations and the properties of the repairs. Third, the correlation between the presence of an abnormal macroscopic appearance at arthroscopy and its biomechanical or histologic properties. The results were based on two standard scoring systems. The International Cartilage Repair Society (ICRS) visual scoring system and the International Knee Documentation Committee (IKDC) score, which evaluate the symptoms, activity level, and health-related quality of life measures.

There were two limitations in this study. First, among the symptomatic population, which the data were derived from, they had additional abnormalities unrelated to the ACI repair. This made the results obtained from them couldn’t easily be extrapolated to the asymptomatic population with ACI. Second, the limitation to study the potential relation between the repair’s biologic properties and the clinical outcome due to the indentometry had to base on proper instrument positioning and also the repair thickness, which could possibly cause inaccurate measurements. Although the histologic evaluation was based on a 2mm thick tissue sample, this couldn’t represent the total composition of the repair tissue, it is more adequate to test for reliable, reproducible, and repeatable results.

It was found at the average of 26.5 months after implantation, the repair was stiffer than normal cartilage. The greatest stiffness was recorded in the following orders: the hyaline articular cartilage, hyaline-like, fibrocartilage, hyaline-like/fibrocartilage group. Besides, there were no difference in the histologic quality resulted from the difference anatomic location of the repair. Regarding of the third focus of the study, the relationship between the presence of an abnormal macroscopic appearance at arthroscopy and its biomechanical or histologic properties, the ICRS and IKDC scores were inconsistent. Based on the ICRS scores, the patients who were macroscopically normal had greater maximum and normalized stiffness than patients who were macroscopically abnormal. On the other hand, the patients with or without abnormal macroscopic appearance scored no difference in IKDC scores. The IKDC scores increased with time in patients in both cases, hyaline cartilage and fibrocartilage. These scores indicated patients did well regardless of the quality of the repair at 3 years postoperatively because these scores were comparable to scores of asymptomatic patients in the ACI cohort. 24 months after ACI, the overall stiffness and macroscopic appearance of hyaline articular cartilage and hyaline-like repairs were similar to normal articular cartilage.

My grandma has inspired me to have a special interest in the field of tissue engineering, and be more specific – cartilage, because of her knee pain. Her cartilage is wearing out as a result of aging, and by the time I heard this ACI repair treatment, I thought it might bring hope to save my grandma from pain. Treating ACI as a possible treatment for my grandma, I want to know more about ACI, and that’s why this article was especially attractive to me because it fulfilled my curiosity about the quality of ACI repair. Besides, by knowing these mechanical and histologic properties of current ACI, we can make improvement and hence one step closer to the durable cartilage repair.

Yee-Wan (Win) Cheung