Midterm follow-up of vertebral geometry and remodeling of the vertebral bidisk unit (VDU) after percutaneous vertebroplasty of osteoporotic vertebral fractures.

The purpose of this study was to investigate geometrical stability and preservation of height gain of vertebral bodies after percutaneous vertebroplasty during 2 years' follow-up and to elucidate the geometric remodeling process of the vertebral bidisk unit (VDU) of the affected segment. Patients with osteoporotic vertebral compression fractures with pain resistant to analgetic drugs were treated with polymethylmethacrylate vertebroplasty. Mean +/- standard error cement volume was 5.1 +/- 2.0 ml. Vertebral geometry was documented by sagittal and coronal reformations from multidetector computed tomography data sets: anterior, posterior, and lateral vertebral heights, end plate angles, and compression index (CI = anterior/posterior height). Additionally, the VDU (vertebral bodies plus both adjacent disk spaces) was calculated from the multidetector computed tomography data sets: anterior, posterior, and both lateral aspects. Patients were assigned to two groups: moderate compression with CI of >0.75 (group 1) and severe compression with CI of <0.75 (group 2). A total of 83 vertebral bodies of 30 patients (7 men, 23 women, age 70.7 +/- 9.7 years, range 40-82 years) were treated with vertebroplasty and prospectively followed for 24 months. In the moderate compression group (group 1), the vertebral heights were stabilized over time at the preinterventional levels. Compared with group 1, group 2 showed a greater anterior height gain (+2.8 +/- 2.2 mm vs. +0.8 +/- 2.0 mm, P < 0.001), better reduction of end plate angle (-4.9 +/- 4.8 degrees vs. -1.0 +/- 2.7 degrees , P < 0.01), and improved CI (+0.12 +/- 0.13 vs. +0.02 +/- 0.07, P < 0.01) and demonstrated preserved anterior height gain at 2 years (+1.2 +/- 3.2 mm, P < 0.01) as well as improved end plate angles (-5.2 +/- 5.0 degrees , P < 0.01) and compression indices (+0.11 +/- 0.15, P < 0.01). Thus, posterior height loss of vertebrae and adjacent intervertebral disk spaces contributed to a remodeling of the VDU, resulting in some compensation of the kyphotic malposition of the affected vertebral segment. Vertebroplasty improved vertebral geometry during midterm follow-up. In severe vertebral compression, significant height gain and improvement of end plate angles were achieved. The remodeling of the VDUs contributes to reduction of kyphosis and an overall improvement of the statics of the spine.