This landmark paper correlates the histological appearance of MACI and ACI grafts in a large group of complex patients up to nine years post implantation. Many clinical studies to date have shown an improvement in clinical outcome scores over time with ACI and MACI grafts. It has been proposed by Lars Petersen and his co-workers based on their extensive clinical experience that these grafts continue to mature with time. This is the first longer term study to demonstrate this. They show that doubling the time to biopsy will increase the likelihood of a hyaline like biopsy 4.21 times. The authors conclude that biopsies for research purposes should be taken at two years post-surgery as the outcome is still improving at this point
A recently published study by Brun et al1 supports this study by showing a higher percentage of hyaline like cartilage grafts with biopsies taken greater than 18 months post implantation.
This study shows an annualised improvement in outcome scores up to 9 years, confirming the finding of others that a ACI or MACI graft gives a durable repair improving with age.
Interestingly early biopsies demonstrating poorer cartilage repair tissue did not have lower outcome scores therefore failing to demonstrate a correlation between timing of biopsy and functional score. Henderson et al2 in evaluating 55 ACI patients with biopsies and indentometry showed maximum stiffness, normalised stiffness, and International Cartilage Repair Society repair scoring were higher for hyaline articular cartilage repairs compared with fibrocartilage but there was no difference in clinical outcome when comparing the hyaline cartilage patients with the fibrocartilage patients.
Thus thankfully for the patient it appears that a good clinical outcome can be obtained a year post procedure despite the finding that the ACI or MACI graft goes through a very slow maturation process. Techniques to advance this maturation process would enhance this treatment option.
1. Brun P, Dickinson SC, Zavan B, Cortivo R, Hollander AP, Abantagelo G. Characteristics of repair tissue in second-look and third-look biopsies from patients treated with engineered cartilage: relationship to symptomatology and time after implantation. Arthr Res Ther 2008;10:R132.
2. Henderson I, Lavigne P, Valenzuela H, Oakes B. Autologous chondrocyte implantation: superior biologic properties of hyaline cartilage repairs. Clin Orthop 2007;455:253-61.
Clatworthy M, FRACS, Orthopaedic Surgeon
Middlemore Hospital, Auckland, New Zealand