Congenital absence of lumbar articular facets. Report of two cases.

X-ray evidence of an absent lumbar facet is usually considered to be indicative of the presence of an osteolytic bone lesion but on rate occasions may be due to a congenital anomaly. Two cases of the congenital absence of a lumbar superior articular facet suggest that this anomaly is not symptom-producing, and in one case was discovered incidentally in a patient without back pain yet led to the performance of a major surgical diagnostic operation. While, rare, a greater awareness of this condition, as clearly defined in the literature on the subject, might occasionally eliminate the need for a similar surgical procedure.