Aaron Kim

Introduction. Osteonecrosis of the femoral head (ONFH) is often called the “coronary artery disease of the hip” because it is cause by similar ischemic conditions¹. An occlusion of the arteries surrounding the femoral head leads to progressive necrosis, further resulting in compromised subchondral circulation, accumulation of microfractures, and eventual collapse of the subchondral bone. Because most individuals affected by ONFH are in their 30s and 40s and the fact that hip injuries are correlated with increased morbidity and mortality, 3D printed bone scaffolds can improve outcomes for this potentially deadly disease.² The main treatment for ONFH has been core decompression which involves drilling a channel in the necrotic portion of the femoral head and allowing new bone to form. However, the growth is slow and leaves the patient vulnerable to femoral head collapse. To prevent this outcome, 3D printed bone scaffolds can be used to provide structural and cellular support to the core decompression channel while also promoting osteogenesis. Methods. First generation 3D printed porous titanium alloy rods were constructed by 3D printing Ti-6Al-4V sphere powder in a configuration that mimicked human trabecular bone with an 84.21 ± 0.19% porosity.⁴ Second generation scaffolds were constructed with medical grade polycaprolactone (PCL) and β-TCP 3D printed in a graded porous configuration that matched the surrounding bone tissue.⁵ Third generation bone scaffolds were constructed from PCL and nano-hydroxyapatite in a porous 3D printed configuration with a center channel for calcium peroxide encapsulated in gelatin spheres and bone marrow mononuclear cells.⁶ Results. 3D printed biodegradable scaffolds loaded with bone mesenchymal stem cells and calcium oxide were shown to increase new bone tissue ingrowth and proliferation. Bone scaffolds loaded with both calcium oxide and stem cells had greater new bone formation, revascularization, and survivability of stem cells than bone scaffolds alone or bone scaffolds with calcium carbonate⁶. Conclusion. These studies have shown that 3D printed degradable bone scaffolds loaded with stem cells and oxygen generating compounds have a significant increase in bone regeneration when compared to core decompression alone. This indicates that a combination of core decompression and 3D printed bone scaffolding may lead to better outcomes in the treatment of ONFH. Some limitations of this review are that all experiments were conducted on animal models and that structural support is still a limiting factor of these 3D printed bone scaffolds.

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