Current solutions for the treatment of chronic articular cartilage defects in the knee

Overview

This review by Chimutengwende-Gordon, Donaldson and Bentley, published in EFORT Open Reviews in 2020, discusses current options for chronic chondral and osteochondral defects of the knee. Cartilage has little capacity to regenerate. Chondral lesions were found in about 60% of patients undergoing knee arthroscopy, and untreated defects may progress to early osteoarthritis.

Bone marrow stimulation

Microfracture is generally regarded as first-line treatment and works best for defects under 2 to 4 cm2 in younger patients. It produces mostly fibrocartilage, which is inferior to hyaline cartilage, and failure is expected after about five years. Adding a collagen scaffold (autologous matrix-assisted chondrogenesis) improves stability and has been used for defects up to 12 cm2.

Graft-based options

Mosaicplasty or the osteochondral autograft transfer system (OATS) fills the defect at once with hyaline cartilage and gave better results than microfracture. A systematic review found 72% survival at about 10 years, but the technique is demanding, causes donor-site morbidity and does worse in larger defects. Fresh osteochondral allografts avoid donor-site problems and can treat larger defects, with reported survivorship of 82% at 10 years, but graft availability and immune reaction are limits.

Cell-based treatment

Autologous chondrocyte implantation (ACI) takes cartilage in a first operation, culture-expands the cells for 4 to 6 weeks and implants them in a second stage. Matrix-assisted implantation (MACI) uses a collagen scaffold, shortens surgery and avoids the periosteal patch complications of the original technique. ACI and MACI produce hyaline-like cartilage and have been used for defects up to 22 cm2, with graft survival of about 78% at five years and 51% beyond ten years in a large prospective study. NICE recommends them as first-line treatment in suitable patients. Disadvantages are two operations, a 12-month rehabilitation and high cost.

Newer methods

Stem cell transplantation can be done in a single stage, has a shorter rehabilitation and costs less than ACI, and early results are promising, but longer-term and randomised studies are needed. Growth factors, platelet-rich plasma, cell-free scaffolds and gene therapy are still under study, and none has yet proved its worth in long-term randomised trials.