Unilateral facet interlocking in the lower cervical spine.

Interlocking of the zygapophysial joints of the lower cervical spine may occur on one or both sides. This paper reports thirty-seven cases of unilateral interlocking (hemiluxation). In the literature unilateral interlocking is usually regarded as a form of dislocation, a term which includes other types of displacement as well. Thus, in the oldcr literature, the term dislocation often refers to an abnormal posture of the head (Langworthy 1930, Brookes 1933). Nowadays it is often used by radiologists to describe a shift of two vertebral bodies in relation to each other, and if this shift is slight the term subluxation is used. Such loose terminology may lead to inaccurate diagnosis and inappropriate treatment.