Biologic augmentation of rotator cuff tendon repair

It is known that a histologically normal insertion site does not regenerate after rotator cuff tendon-to-bone repair. Cytokines play an important role in cell chemotaxis, proliferation, matrix synthesis, and cell differentiation and may thus improve rotator tendon-to-bone healing. We have used a sheep infraspinatus repair model to evaluate the effect of osteoinductive growth factors (bone morphogenetic protein [BMP] 2, BMP-7, transforming growth factor [TGF] β₁, TGF-β₂, TGF-β₃, and fibroblast growth factor) and BMP-12 on tendon-to-bone healing. We have found that these molecules improve formation of new bone and fibrocartilage at the healing tendon attachment site, resulting in improved load to failure. Several other avenues have the potential to augment repair site biology. For example, because platelets are known to contain various cytokines, they may be isolated from autologous blood and could provide an effective method by which to deliver growth factors to a rotator cuff tendon repair site. Furthermore, modalities that improve local vascularity, such as low-intensity pulsed ultrasound or nitroglycerine, have the potential to augment rotator cuff repair healing. Finally, important information about the biology of tendon healing can be gained from studies of substances that inhibit healing, such as nicotine and nonsteroidal anti-inflammatory medications.