Defect in the articular process of the lumbar facet.

Bone defect in the lumbar articular facet is rarely noted, and only a few reports on its clinical course have been presented. We report on seven cases with lumbar inferior facet defect whose symptoms were mimicking spondylolysis. We have found three types of the defect shape on radiographs: linear, blunt, and irregular. There were five cases with linear type, one with blunt, and one with irregular. All patients had persistent low back pain, especially when doing physical activity or sports, but no one had history of major trauma or accident. Injection of a small amount of anesthetic temporarily alleviated the low back pain. The low back pain in six patients was controlled with conservative treatments, such as bracing or medication; bone union was especially gained in one case. However, a volleyball player's pain could not be controlled conservatively, and removal of the bone fragment was performed. It is considered that facet defect is not as rare as presumed, and more attention should be paid to it as a source of low back pain.