This report shows a rare case of avascular necrosis of vertebra body after insertion of interspinous device after insertion of interspinous device and its plausible cause. A 82-year-old woman presented with severe back pain for 1 week without injury. In her history, she had undergone decompression and implantation of L4-5 interspinous device for the relief of neurogenic claudication at 4 year ago. Magnetic resonance image demonstrated signal change suggesting avascular necrosis of L5 vertebra body and fracture of posterior facet after insertion of interspinous device. In this case, avascular necrosis of lumbar vertebra body was documented with simple radiograph and MRI and symptom was satisfactorily relieved with conservative treatment. Avascular necrosis of lumbar vertebra body can occur as a complication of interspinous process device. Surgeons always must consider the possibility of avascular necrosis of vertebral body in patients with osteoporosis after insertion of interspinous device.