**2. Bone marrow stimulation (BMS) techniques**

#### **2.1 Drilling/microfracture/abrasion techniques**

Burmann in 1931, Haggart in 1940, and Magnuson in 1941 described joint debridement techniques for the treatment of osteoarthritis. Pridie in 1958 introduced the technique of perforation of the subchondral tissue exposing the vascularization of bone marrow, and later Ficat in 1979 described the spongialization, a resection of the entire subchondral bone plate chondromalacia patellae, with good to excellent results. Steadman suggested that specially designed awls are used to make multiple perforations or "microfractures," into the subchondral bone plate [21–30]. The perforations are made as close together as necessary, but not so close that one breaks into another. Consequently, the microfracture holes are approximately 3–4 mm apart (or three to four holes per square centimeter) [31, 32].

#### *Reconstruction with Joint Preservation DOI: http://dx.doi.org/10.5772/intechopen.84354*

Chondroplasty by abrasion depends on the mechanical stimulation, like burrs, of the joint defect, without penetration of the subchondral bone. Exposure of small blood vessels generates formation in a clot attached to the surface. Fibrous tissue metaplasia occurs for fibrocartilage.

Multiple perforations have the benefit of causing less thermal damage than chondroplasty by abrasion and also leave the subchondral surface more rugged, allowing better adhesion of the blood clots. The penetration of the subchondral bone stimulates the local release of growth factors from the underlying bone. These factors attract and aid the differentiation of mesenchymal stem cells from the bone marrow in chondrocyte-like cells [33, 34].

Patients require a period of 6–8 weeks of non-weight-bearing to allow maturation of the fibrocartilage. Also, according to some authors, continuous passive motion for pain control and better function may be necessary [35].

For better results, some important factors include a body mass index below 30 kg/m2 , age under 40 years, defect less than 4 cm2 , volume of repaired cartilage (defective filling) greater than 66%, and symptoms less than 12 months [35].

The repair tissue may be able to fill the defect, but it lacks the normal histological or biomechanical properties of hyaline cartilage. Therefore, it has a stability inferior to the compressive and shear forces and tends to deteriorate with the time [35–39].

However, in their 2017 study, Frehner et al. concluded that treatment of osteochondral lesion by microfracture cannot be seen as an evidence-based procedure [39].
