SUBLUXATIONS
Definition
A vertebral subluxation is a displacement, less than a dislocation, in which the chief element is the partial loss of normal apposition of the articular surfaces of the subluxated vertebra with those of the vertebra above or below, or both. Or, Vertebral subluxation is a permanent partial dislocation.
How Produced
Subluxations are primarily caused by trauma—falls, blows, strains, etc., being the chief factors. Hereditary weakness in structure of some part predisposes by rendering that portion more easily displaced.
Subluxations are never hereditary but may be congenital through violent or instrumental delivery into the world or may appear hereditary because they occur shortly after birth through the effect of light jars upon the hereditarily weakened segments of the spinal column.
They are always the result of concussions of forces; never of forces acting entirely within the organism. They result from the contact of the body with its environment.
It has been said that muscular action in response to peripheral irritation may produce subluxation. The laws of reflex action render this impossible. Given a normally aligned vertebra, and consequently normal nerves and a normal reflex arc in that segment, the ventral horn cells respond to a slight peripheral stimulus by exciting muscular contraction on the same side with the irritation. If the irritation be sufficiently increased, the response occurs on both sides but most strongly on the side from which the irritation comes. Greater irritation merely serves to cause greater distribution of the responsive action. (See any standard physiology on reflex action.) In no case will the difference between the contractions of muscles on the two sides be sufficient to displace a normally aligned vertebra. Nature has provided against that contingency.
Given a subluxated vertebra causing nerve impingement and thus interruption of the normal action of the reflex arc, irritation may result in greater contraction upon the opposite side than upon the side of the irritation. This is an abnormal condition and accounts for the increase of previously existing subluxations under pain or peripheral irritation. But in every instance trauma must and does precede and cause subluxation.