[Insufficiency fractures of the spine in relation to cancellous bone density : An in vitro study].

Background: The risk of osteoporotic insufficiency fractures (Fx) at the axial skeleton increases with decreasing bone density, with an accumulation in the thoracic and thoracolumbar regions. To better understand the differential distribution of Fx along the spine, morphological and osteodensitometric studies were performed by computed tomography (CT) in the various spine sections. In addition, we aimed to clarify whether Hounsfield units (HU) found on CT examinations from other indications correlate with bone density and could be grounds for osteologic diagnosis.

Material And Methods: The entire spines of 26 body donors were fixed in a Plexiglas water phantom and analyzed by high-resolution spiral CT. In addition, CT morphological cancellous bone density was measured in HU from C3 to S2 (624 vertebral bodies). Bone mineral density (BMD, mg/ml) was calculated and used to estimate osteoporosis (OPO).

Results: OPO was present in all spines. Significantly increased sintering fractures were found in the thoracic and thoracolumbar regions when BMD was below 60 mg/ml. Fx in the cervical spine area were not found overall. Cancellous bone density was significantly higher in the cervical (median 188.6 HU) than in the lumbar (median 63.6 HU) and sacral (median 25.5 HU) spine.

Discussion: BMD loss of vertebral body cancellous bone leads to an increased risk of Fx, which is also found in the cadaver spines. However, an apparent threshold for the occurrence of sintering fractures is not undercut in the cervical region. Finding a threshold for HU would be relevant to clinical practice.