Bone Marrow Stimulation: Microfracture, Drilling, and Augmentation

Bone marrow stimulating procedures (BMS) are often used to treat symptomatic grade III/IV cartilage damage. Despite good initial clinical successes, the medium- and long-term results with BMS have been equivocal. This is attributed to limited histologic and mechanical quality of the regenerated tissue as well as incomplete defect filling. In addition, persistent postoperative complaints may stem from surgery-related bone pathologies and excess bone formation in the defect site. Consequently, recent years have seen the development of various biological augmentation techniques for BMS. A change in the surgical technique using thin drills (0.1–1.5 mm) causes less bone damage while providing sufficient access to bone marrow cells. The addition of platelet-rich plasma (PRP) appears scientifically justified, but there is a large product-specific heterogeneity in the published studies. Biomaterials in the form of matrices, membranes, scaffolds, and gels have been used in clinical use in combination with BMS for some time and there is substantial evidence of superiority over standard BMS procedures such as Microfracture (Mfx). Additional biological enhancement of biomaterials through the use of adjuvants such as bone marrow aspirate or concentrate (BMA/BMAC), PRP, or minced cartilage have demonstrated good results with durable clinical improvements, but due to the variety of evidence, levels, and reported outcomes there is still no universally agreed-upon standard procedure. Recent developments have shown that biomaterials (e.g., scaffolds and membranes), cells (e.g., mesenchymal stromal cells [MSCs] and chondrocytes), and biological adjuvants (e.g., PRP and BMAC) have a synergistic function in BMS and are important for achieving positive clinical results.