Protrusion of the nucleus pulposus of the intervertebral disk into the spinal canal. Also called a herniated disk, or a slipped disk.
                                                            
                                                     
                        
                                                
                        
                        
                            Displacement of nuclear material and other disc components beyond the normal confines of the annulus. Four degrees os displacement are recognized : herniation, protrusion, extrusion and sequestration.
                                                            
                                                     
                        
                                                
                        
                        
                            Commonly called "slipped disc". An extrusion of the nucleus pulposus through the anterior annular fibers.