Background: Despite the popularity of microfracture as a first-line treatment for articular cartilage defects in the knee, systematic information on its clinical efficacy for articular cartilage repair and long-term improvement of knee function is not available.
Hypothesis: Systematic analysis of the existing clinical literature of microfracture in the knee can improve the understanding of the advantages and limitations of this cartilage repair technique and can help to optimize its indications and clinical outcomes.
Study design: Systematic review.
Methods: A comprehensive literature search was performed using established search engines (MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled Trials) to identify original human studies of articular cartilage repair with microfracture. Modified Coleman Methodology Scores were used to analyze the quality of the existing studies. Clinical efficacy of articular cartilage repair was evaluated by systematic analysis of short- and long-term functional outcome scores, macroscopic and microscopic repair cartilage quality, and findings of postoperative magnetic resonance imaging.
Results: Twenty-eight studies describing 3122 patients were included in the review. The average follow-up was 41 months, with only 5 studies reporting follow-up of 5 years or more. Six studies were randomized controlled trials and the mean Coleman Methodology Score was 58 (range, 22-97). Microfracture effectively improved knee function in all studies during the first 24 months after microfracture, but the reports on durability of the initial functional improvement were conflicting. Several factors were identified that affected clinical outcome. Defect fill on magnetic resonance imaging was highly variable and correlated with functional outcome. Macroscopic repair cartilage quality positively affected long-term failure rate, while the influence of histologic repair tissue quality remained inconclusive.
Conclusion: This systematic analysis shows that microfracture provides effective short-term functional improvement of knee function but insufficient data are available on its long-term results. Shortcomings of the technique include limited hyaline repair tissue, variable repair cartilage volume, and possible functional deterioration. The quality of the currently available data on micro-fracture is still limited by the variability of results and study designs. Further well-designed studies are needed to determine the long-term efficacy of microfracture and to define its specific clinical indications compared to other cartilage repair techniques.