Definition: Anhydromyelia is a medical term referring to an abnormality where all bones are fused together without any joint space or cartilage, often seen in elderly individuals with bone defects or osteoporosis. This condition can be caused by various factors such as infection, trauma, or genetic abnormalities. The primary cause of anhydromyeliasis is a deficiency in hyaluronan, which is the main component of cartilage and bone.