Spinal arch isthmus

Bone nonunion can occur on one or both sides of the pyramid. The spinous process is normal or absent or combined with other deformities such as spina bifida, but it is clinically asymptomatic or slipped. This type of nonunion is called spinal disintegration, which is a potential internal cause of back and leg pain. Spondylolisthesis mostly occurs in the 5th lumbar vertebra, and is rare in other parts.