In cases of vertebral collapse after a trivial injury in elderly patients with severe osteoporosis, it can be a diagnostic challenge to determine whether the cause is a benign compression fracture or malignant metastasis. A 78-year-old male patient was referred to the emergency department for the evaluation of weakness of the left lower limb. He had undergone percutaneous vertebroplasty four months earlier after being diagnosed with L3 osteoporotic compression fracture. He was treated with foraminotomy at the L3–4 level after being diagnosed with foraminal stenosis two months earlier at a spine clinic. Magnetic resonance (MR) images showed significant signal change from the vertebral body to the posterior element, and widely spreading extraspinal extension of soft tissue at L3. Computed tomography scan revealed osteolytic changes in regions including the ventral body and pedicle. Emergent decompressive laminectomy and bone biopsy were performed, and the histologic evaluation showed metastatic squamous cell carcinoma. A retrospective review of previous MR images showed obvious pedicle and facet involvement, and paraspinal extension of soft tissue, which are highly suggestive of malignant metastasis.