PURPOSE:
To examine the entire repair tissue resulting from marrow-stimulation techniques in patients with early osteoarthritis.

METHODS:
The repair tissue and adjacent articular cartilage after failed marrow-stimulation techniques (microfracture and Pridie drilling) of 5 patients (47-65 years old) with cartilage defects and radiographic early osteoarthritis (Kellgren-Lawrence grading 1 and 2) was removed during total joint arthroplasty (mean time until analysis: 8.8 months), analysed by histology, polarized light microscopy, immunohistochemistry, biochemistry and by histological score systems.

RESULTS:
Macroscopic cartilage repair assessment revealed ICRS grades of II (nearly normal) and III (abnormal). Cartilage defects were mostly completely filled with a fibrocartilaginous tissue that had small and large fissures. Cartilage-specific stains of the repair tissue were more intense than the surrounding native cartilage but reduced compared with normal articular cartilage. The subchondral bone was incompletely restored. A new tidemark was absent. The repair tissue always showed positive immunoreactivity for types II and X collagen, and was sometimes positive for type I collagen. Proteoglycan contents of the repair tissue were generally higher than of the surrounding cartilage. The repair tissue was always more cellular than the adjacent articular cartilage. Histological scoring of the repair tissue revealed a mean Sellers score of 17.6 ± 3.0 and an ICRS grading of 7-9.

CONCLUSION:
Failed marrow stimulation of articular cartilage defects in patients with early osteoarthritis is characterized by fibrocartilaginous repair. The balance of cell number to extracellular matrix is shifted towards an increased cell number in this tissue. Articular cartilage repair did not reach the quality of normal hyaline articular cartilage.

LEVEL OF EVIDENCE:
IV.





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