Kyphosis correction and height restoration effects of percutaneous vertebroplasty

Abstract

Background and purpose: Percutaneous vertebroplasty is known for its pain-relieving effect. Our purpose was to evaluate its effect on the kyphosis angle, wedge angle, and height of the fractured vertebral body.

Methods: We reviewed digital radiographs of 73 vertebral bodies in 53 patients before and after vertebroplasty. We measured the spinal kyphosis angle and the wedge angle of the fractured vertebral body. Ratios of the height of the anterior border, center, and posterior borders of the collapsed vertebra to the height at the posterior border of an adjacent normal vertebral body were measured. Gain from vertebroplasty and the restoration percentage (gain divided by loss) were calculated for each parameter.

Results: The kyphosis angle, wedge angle, anterior height, center height, and posterior height significantly improved after vertebroplasty. The mean reduction in the kyphosis angle was 4.3 degrees, and the wedge-angle reduction was 7.4 degrees. The mean wedge-angle reduction in fractured vertebral bodies containing gas was 10.2 degrees. Restoration percentages for the kyphosis angle and wedge angle were 19% and 44%, respectively. Gain in the height of the fractured vertebral bodies was 16.7% for the anterior border, 14% for the center, and 7% for the posterior border. Restoration percentages for the height of the vertebral body were 29% for the anterior border and 27% for the center.

Conclusion: Vertebroplasty increases the height of the fractured vertebra and reduces the wedge and kyphosis angles. These effects are most remarkable in fractured vertebra containing gas.

Fig 1.

Horizontal beam lateral view of a patient before (A) and after (B) padding with pillows under the upper chest and lower abdomen. The patient has severe back pain and tenderness at the L1 level. The wedge angle of the L1 vertebral body (marked) is 15 degrees before padding, and 7 degrees after padding. The anterior, midline, and posterior vertebral height of L1 increased by 4.7 mm, 3.3 mm, and 0 mm, respectively. L2 is an old fracture. No change in height or wedge angle at L2 level is found before and after padding.

Fig 2.

Measurement of the collapsed vertebral body and reference line. Height of a collapsed vertebral body was measured at the anterior border (A), center (C), and posterior border (P). The height of the posterior border (NP) of an adjacent normal vertebral body was measured for reference. The wedge angle (θ) in this case is 28 degrees before vertebroplasty (A) and 11 degrees after vertebroplasty (B).

Fig 3.

Wedge angle reduction in 73 vertebral bodies. Most vertebral bodies in the gas group were on the right-hand side of the x-axis; therefore, the gas group had more wedge angle reduction. Fig 4. Gain of the anterior height from percutaneous vertebroplasty in 73 vertebral bodies. The gain is more remarkable in the “gas” group (P = .001).

Fig 5.

Correlation plot of gain (the wedge angle reduction)versus loss (original wedge angle) after vertebroplasty. There is a trend toward higher gain in cases with more original loss. Most cases of the “gas” group are in the right upper quadrant, whereas most cases of the “non-gas” group are in the left lower quadrant, suggesting that the gas group had larger wedge angle before vertebroplasty and more wedge angle reduction after vertebroplasty. After linear regression analysis, the slope for the “gas” group (0.61) is significantly larger than that for the “non-gas” group (0.24), again confirming the wedge angle reduction effect was more obvious in the “gas” group. Fig 6. Correlation plot of the gain from percutaneous vertebroplasty versus the loss from fracture for the anterior border of collapsed vertebral bodies. There is a trend toward higher gain in cases with more original loss. Most cases of the “gas” group are in the right upper quadrant, whereas most cases of the “non-gas” group are in the left lower quadrant, suggesting the gas group had larger initial loss of height before vertebroplasty and more gain after vertebrolasty. The regression line for the “gas” group is higher than the “non-gas” group, which confirms again that the vertebroplasty resulted in better height restoration at the anterior border of the collapsed body in the “gas” group.