The erosion of the lumbar vertebral bodies by a chronic contained rupture of an infra-renal abdominal aortic aneurysm is a rare event. Chronic contained rupture can cause diagnostic difficulties as there are many clinical presentations, such as: back pain, sciatic pain or an expansive abdominal mass. The diagnosis is sometimes made following an incidental finding on radiological examination. Currently a CT scan is the gold standard diagnostic tool. The outcome following urgent surgical or endovascular repair is equivalent to that of an elective aneurysm repair. We report a case of a 59 year old man admitted for septic rupture of a cutaneous fistula resulting from a false aneurysm in the left groin. Pre-operative CT scan revealed a 6 cm abdominal aortic aneurysm, with chronic contained rupture. This had caused bone erosion of the vertebral body of the third lumbar vertebrae.