Spondylolysis
Description: Spondylolysis is a unilateral or bilateral bony defect in the pars interarticularis or isthmus of the vertebra. The term derives from the Greek words spondylos (vertebra) and lysis (defect). It can cause a slipping of the vertebra. Relevant anatomy: Vertebrae consist of the vertebral body and a bony ring or arcus which protects the spinal cord.The arcus is formed by two pedicles which attach to the dorsal side of the vertebral body and two laminae, which complete the arch. The area between the pedicle and the lamina is called the pars interarticularis and is in fact the weakest part of the arcus. It is the pars interarticularis that is affected in spondylolysis. Aetiology: Affects 3-6% of population. This condition appears in the first or second decade of life; the frequency of spondylolysis increases with age until 20 years. Men are affected twice as often as women. There is a possible genetic tendency for people with lower cortical bone density at the pars