Zig Zag Deformity: An abnormality of the hands in patients that have rheumatoid arthritis, consisting of ulnar
deviation at the metacarpophalangeal joints and radial deviation of the radiocarpal compartment of the wrist.
Among the causes of this deformity is muscle or tendon imbalance. A zigzag contour may also occur in the
interphalangeal joints in patients that have osteoarthritis.
Zonography: An x-ray imaging technique used to produce films of body sections similar to those made by
tomography. A very narrow exposure angle of less than ten degrees is used in zonography, producing a safe focal
zone of less than one inch in thickness.
Zygapophyseal Joint: This is the technical name for spinal facet joint. The facet joint is made up two superior
upward projecting surfaces of the lower vertebra interconnecting with two inferior downward projecting surfaces
from the vertebra directly above. Facet joints link the bones of the spine together in the posterior or back part of
the spine. Two facet joints are present at each spinal segment. The facet joints are important in controlling
twisting, flexion and extension motions of the cervical and lumbar spine.