Bone marrow stimulating therapies like microfracturing are indicated in rather smaller cartilage defects (< 2–3 cm²) with good and healthy subchondral bone. The surgical technique is similar to the treatment of other joints like the knee or ankle and can be performed arthroscopically. Initially a careful debridement of the defect using an arthroscopical shaver or curette is necessary, which must be completed down to the subchondral bone including the calcified layer and into healthy surrounding cartilage. Subsequently the subchondral surface is perforated with special awls or drills, so blood containing stem cells can escape from the bone marrow and build a clot in the former defect zone, which over time transforms to fibrocartilage tissue [5]. It is crucial that the often sclerotic subchondral bone is completely perforated, which can be ensured by the leakage of grease drops from the underlying bone marrow. Studies have shown that the optimal distance between the perforations is 3 and 4 mm [13]. Microfracturing of the shoulder is a relatively easy and cost-effective therapy with similar good clinical results in comparison to other joints, if the indication is set properly [4]. Furthermore in comparison to other established cartilage regenerative procedures, an additional surgery at the knee for harvesting autologous osteochondral transplants or chondrocytes is not necessary. However, microfracturing is not indicated for bipolar lesions, and it does not seem suitable for larger cartilage defects of more than 3 cm² and for patients over 40 years of age. Furthermore compared with other locations like the femorotibial joint, microfracturing in the glenohumeral joint can be quite challenging since the surgeon has to avoid an approach, which is too tangential to the defect. While for the humeral head, this problem can be solved by internal or external rotation of the arm; for defects of the glenoid, the arthroscopical portal should be placed more lateral in order to reach the lesion more vertical (Fig. 26.3).

By now ACT is a standard therapy for the treatment of large (>2cm²) full-thickness chondral lesions with intact subchondral bone in different joints with good clinical outcome. Still clinical experience for the glenohumeral joint is rare, but its application in other joints has shown that ACT is contraindicated in bipolar defects and that previous microfracturing is associated with minor results [9]. In a first operation, chondrocytes are harvested from the posterior-superior zone of the humeral head arthroscopically. Afterward the cells are in vitro cultivated for 4–8 weeks (dependent on the producing company) and then implanted into the defect zone. Also for ACT a careful debridement is necessary prior to implantation; however, in contrast to microfracturing, damage to the subchondral layer and subsequent bleeding from the bone marrow must be avoided as the implanted chondrocytes should not be mixed with stem cells. Especially for defects of the humeral head, matrix-associated ACT (MACT) procedures, where the expanded chondrocytes are imbedded in a three-dimensional collagen bio-scaffold that is fixed in the surrounding cartilage by sutures, have seemed to be advantageous in the past years, as the implanted chondrocytes are distributed more homogeneous in the defect zone on the spherical surface of the humeral head [4]. Though this procedure requires an open approach including the detachment of the subscapularis tendon and therefore it causes a more stringent rehabilitation [2]. Following the recent invention of injectable ACT, where the cultivated cells are contained in albumin hyaluronic acid gels, less invasive arthroscopical or arthroscopical-assisted procedures are possible today; however, the arthroscopical technique still requires a high level of experience by the surgeon.