"Occult" osteoporotic vertebral fractures: vertebral body fractures without radiologic collapse.

Study Design: Retrospective observational study.

Objectives: We report our experience with patients who presented with osteoporotic vertebral fractures with no visible deformation of vertebral body.

Summary Of Background Data: The diagnosis of osteoporotic vertebral fractures largely relies on the observation of vertebral deformations on plain radiographs, termed vertebral collapses. There are no data on the characteristics, or indeed of the reality, of osteoporotic vertebral fractures with no significant deformation of the vertebral body.

Methods: We retrospectively analyzed cases that presented with acute back pain with no initial deformation of the vertebral body on plain radiographs, and later proved to be fresh osteoporotic vertebral body fractures. All cases met each of the following criteria: 1) The incriminated vertebra appeared normal on initial radiographs (Genant's Grade 0 deformation). 2) The diagnosis of fresh vertebral body fracture was confirmed by MRI. 3) The diagnosis of osteoporosis was made by the combination of established osteoporosis, ruling out of underlying disease, and follow-up.

Results: We observed 21 fractures in 16 patients (11 female/5 male; mean age, 72 years). Most of these fractures affected the lumbar spine (14 of 21 occurred at L2-L5). Osteoporosis was known beforehand in 9 patients and newly diagnosed in 7 patients. At follow-up, radiographs were obtained for 19 of 21 fractures: in 15 cases, the vertebral fracture developed a vertebral collapse (Genant's Grade > or = 0.5) in a mean of 12.5 weeks (range, 4-24 weeks); in the 4 remaining cases, the vertebra remained normal. All cases had a clinically favorable outcome.

Conclusion: Osteoporotic vertebral fractures with no sign of vertebral collapse on initial radiographs do indeed exist. They are analogous to occult stress fractures well known in other skeletal sites. They must not be misdiagnosed as malignant lesions.