Straight chiropractors adhere to the philosophical principles set forth by D.D. and B.J. Palmer, and retain metaphysical definitions and vitalistic qualities.[37] Straight chiropractors believe that vertebral subluxation leads to interference with an "innate intelligence" exerted via the human nervous system and is a primary underlying risk factor for many diseases.[37] Straights view the medical diagnosis of patient complaints (which they consider to be the "secondary effects" of subluxations) to be unnecessary for chiropractic treatment.[37] Thus, straight chiropractors are concerned primarily with the detection and correction of vertebral subluxation via adjustment and do not "mix" other types of therapies into their practice style.[37] Their philosophy and explanations are metaphysical in nature and they prefer to use traditional chiropractic lexicon terminology (e.g., perform spinal analysis, detect subluxation, correct with adjustment).[22] They prefer to remain separate and distinct from mainstream health care.[22] Although considered the minority group, "they have been able to transform their status as purists and heirs of the lineage into influence dramatically out of proportion to their numbers."[22]
Vertebrobasilar artery stroke (VAS) is statistically associated with chiropractic services in persons under 45 years of age,[147] but it is similarly associated with general practitioner services, suggesting that these associations are likely explained by preexisting conditions.[146][148] Weak to moderately strong evidence supports causation (as opposed to statistical association) between cervical manipulative therapy (CMT) and VAS.[149] There is insufficient evidence to support a strong association or no association between cervical manipulation and stroke.[15] While the biomechanical evidence is not sufficient to support the statement that CMT causes cervical artery dissection (CD), clinical reports suggest that mechanical forces have a part in a substantial number of CDs and the majority of population controlled studies found an association between CMT and VAS in young people.[150] It is strongly recommended that practitioners consider the plausibility of CD as a symptom, and people can be informed of the association between CD and CMT before administrating manipulation of the cervical spine.[150] There is controversy regarding the degree of risk of stroke from cervical manipulation.[15] Many chiropractors state that, the association between chiropractic therapy and vertebral arterial dissection is not proven.[17] However, it has been suggested that the causality between chiropractic cervical manipulation beyond the normal range of motion and vascular accidents is probable[17] or definite.[16] There is very low evidence supporting a small association between internal carotid artery dissection and chiropractic neck manipulation.[151] The incidence of internal carotid artery dissection following cervical spine manipulation is unknown.[152] The literature infrequently reports helpful data to better understand the association between cervical manipulative therapy, cervical artery dissection and stroke.[153] The limited evidence is inconclusive that chiropractic spinal manipulation therapy is not a cause of intracranial hypotension.[154] Cervical intradural disc herniation is very rare following spinal manipulation therapy.[155]
Chiropractors use hands-on spinal manipulation and other alternative treatments, the theory being that proper alignment of the body's musculoskeletal structure, particularly the spine, will enable the body to heal itself without surgery or medication. Manipulation is used to restore mobility to joints restricted by tissue injury caused by a traumatic event, such as falling, or repetitive stress, such as sitting without proper back support.