A 67-yr-old woman with a working diagnosis of osteoporosis was seen for low-back pain. Her medical history revealed a recent kyphoplasty procedure for an L2-compression fracture. Limited low-back motions with bilateral paravertebral muscle guarding were noted on physical examination. Radiologic evaluations of lumbar vertebrae and bone mineral density measurements using dual-energy x-ray absorptiometry were performed (Figs. 1 and 2). The initial L1–L4 t score was thought to be consistent with osteopenia (−1.92); however, further analysis revealed that the L2 score (+2.48) had, in effect, skewed the results (Table 1). When the value pertaining to the L2 vertebra was neglected, the mean value of t scores were recalculated using L1, L3, and L4 values as −3.12 (osteoporotic).
The authors report this case for two reasons. First, considering the mounting frequency of kyphoplasty operations, we imply that dual-energy x-ray absorptiometry measurements may yield incorrect results in such patients.1 Accordingly, clinicians should diligently evaluate such patients’ bone mineral density measurements in light of their medical history. Secondly, a better estimation of L1–L4 t score can easily be done with a simple correction by omitting the value of the involved vertebra.
1. McAllister A, Spencer R, Yannopoulos A: Bone densitometry study in a patient with prior kyphoplasty variant of vertebroplasty. Clin Nucl Med