In chiropractic, vertebral subluxation is a set of signs and symptoms of the spinal column. Those chiropractors who assert this concept (specifically, straight chiropractors) also add a visceral component to the definition. Chiropractors maintain that a vertebral subluxation complex is a dysfunctional biomechanical spinal segment which is fixated. Chiropractors additionally assert that the dysfunction actively alters neurological function, which in turn, is believed to lead to neuromusculoskeletal and visceral disorders. The WHO acknowledges this difference between the medical and chiropractic definitions of a subluxation: medical doctors only refer to "significant structural displacements" as subluxations, whereas chiropractors suggest that a dysfunctional segment, whether displaced significantly or not, should be referred to as a subluxation. This difference has been noted in the proceedings of the chiropractic profession's Mercy Center Consensus Conference: "The chiropractic profession refers to this concept as a 'subluxation'. This use of the word subluxation should not be confused with the term's precise anatomic usage, which considers only the anatomical relationships."