Study design: A prospective radiographic analysis of deformity correction during the balloon kyphoplasty procedure.
Objective: To determine the spontaneous reduction of the deformity in prone position, the subsequent deformity correction by the inflatable bone tamp, and the overall deformity correction after deposition of the cement.
Summary of background data: Fracture mobility has been shown to contribute to fracture reduction in vertebroplasty. Spontaneous reduction has not been taken into account in recently published series of balloon kyphoplasty, but it must be considered when performing vertebral augmentation and when reporting and interpreting the significance of vertebral height restoration.
Methods: A consecutive series of 39 osteoporotic vertebral compression fractures were treated in 30 patients. Lateral radiographs were taken and analyzed at six different time points: 1) Preoperative standing. During the kyphoplasty procedure, four consecutive radiographs were obtained: 2) after placing the patient in prone position on the operation table, 3) after inflation of the bone tamp (IBT), 4) after deflation and removal of the IBT, and 5) after deposition of the cement. 6) Standing lateral radiographs were taken after the procedure. All fractures were analyzed for improvement in sagittal alignment (Cobb angle, kyphotic angle, sagittal index, vertebral height), complications, and reduction of pain (VAS).
Results: Placement of the patient in prone position displayed a significant spontaneous reduction in deformity of 6.5 degrees +/- 4.1 degrees Cobb angle. Inflation of the IBT demonstrated a further reduction of the fracture and a significant improvement of the Cobb angle of 3.4 degrees compared with baseline prone. After deflation and removal of the IBT and placement of the cement, no significant loss of fracture reduction was seen. Postoperative measurement of the Cobb angle by means of standing radiographs demonstrated a 3.1 degrees significant loss of reduction compared with the intraoperative measurement in prone position after cement application. Cement leaks occurred in 9 of 39 vertebral fractures. All patients subjectively reported immediate relief of their typical fracture pain. The VAS score significantly improved from 8.7 +/- 1.4 before surgery to 2.3 +/- 0.9.
Conclusion: The restoration of height in kyphoplasty is attributed to dynamic fracture mobility as well as to the expansion of the inserted balloon tamp.