Can preoperative magnetic resonance imaging be used for sagittal kyphotic flexibility assessment in patients with kyphosis secondary to symptomatic old osteoporotic thoracolumbar fracture?

OBJECTIVE: This study aimed to investigate whether preoperative magnetic resonance imaging (MRI) can be used for sagittal kyphotic (SK) flexibility assessment in patients with kyphosis secondary to symptomatic old osteoporotic thoracolumbar fracture (so-OTLF). METHODS: The authors evaluated the radiographic data of patients with kyphosis secondary to so-OTLF. All patients underwent posterior corrective fusion surgery in the hospital. Spinal sagittal parameters were measured on standing radiographs preoperatively. The regional kyphosis angle (RKA) was also measured on preoperative supine MRI and intraoperative prone radiographs on the surgical frame. The SK flexibility in patients with kyphosis secondary to so-OTLF was defined as the difference from the RKA measured on the standing radiographs to that measured on the intraoperative prone radiographs or preoperative supine MRI. The difference and the correlation between the SK flexibility measured by these two methods were compared and analyzed. RESULTS: Thirty-seven patients were included. The RKA measured on standing radiographs, supine MRI, and intraoperative prone radiographs were 48.0°, 34.4°, and 32.0°, respectively. Compared with the RKA measured in standing position, the RKA measured on supine MRI decreased by 13.6° (95% confidence interval 11.4°–15.8°), whereas that measured on intraoperative prone radiographs decreased by 16.1° (95% confidence interval 13.7°–18.5°). A linear correlation existed between the SK flexibility measured on supine MRI and that measured on intraoperative prone radiographs, with a mean difference of 2.4° (R(2) = 0.912, p < 0.001). CONCLUSION: The degree of regional kyphosis deformity was reduced by self-reduction of the intraoperative surgical frame. With a predictive value similar to an intraoperative prone radiograph, preoperative supine MRI can be used for SK flexibility assessment in patients with kyphosis secondary to so-OTLF. The ability to predict the intraoperative degree of regional kyphosis deformity with positioning before an operation may help with surgical planning and patient counseling regarding expectations and risks of surgery.