In spondylolysis there is a defect in the neural arch of the fifth (rarely the fourth) lumbar vertebra. There is loss of bony continuity between the superior and the inferior articular processes, the deficiency being bridged by fibrous tissue. If this stretches or gives way, the consequent vertebral displacement constitutes one variety of spondylosthesis

through the detect was formerly regarded as congenital it is now widely believed that it may be caused by injury; or, more often, it may be the result of a stress fracture in childhood or adolescence. Clinically, spondylolysis (the defect without displacement) is often symptomless, but it if sometimes a cause of deep lumbar back pain. radiographically the defect is usually best shown in oblique projections


Treatment. This is often unnecessary. Aching may be relieved by a surgical corset, If pain is unusually troublesome an attempt may be made to to close the defect in the pars interarticularis on each aide by transfixing it with a screw and laying in slender bone grafts (Buck, 1970); or alternatively, local fusion of the spine may be undertaken.