[Analysis of sagittal parameters about senior thoracolumbar proximal junctional kyphosis after lumbar long segment...

To explore the radiographic risk factors of senior thoracolumbar proximal junctional kyphosis (PJK) after lumbar long segment fusion.

From January 2009 to December 2011, the PJK group enrolled 9 patients who satisfied the following criteria: being older than 60 years, having lumbar fusion operation no less than 4 levels, upper instrumented vertebrae being L1 or L2, emerging PJK in 2-year follow-up, and the control group enrolled 10 matched patients without PJK. Their sagittal parameters including sagittal vertical axis, thoracic kyphosis, lumbar lordosis, upper instrumented vertebral angle, pelvic incidence, sacral slope, pelvic tilt, lumbo-pelvic lordosis on full length spine lateral film were measured, the oswestry disability index (ODI ) scores of the two groups in the last follow up recorded, and the parameters and ODI scores of two groups compared.

The phenomena of PJK emerged average 7.9 months post-operation. The patients' lumbar lordosis reduced and compensatory pelvic appeared backward obviously after PJK emerged. Compared with the control group, lumbar lordosis, pelvic radius-T12 (PR-T12), upper instrumented vertebral angle were small in the PJK group, suggesting more severe lumbar pelvic imbalance. The ODI scores of the PJK group and contral group were 40.6 ± 15.9 and 21.5 ± 15.0 respectively, and the difference was significant.

PJK after lumbar long segment fixation of elderly patients can aggravate the sagittal imbalance and reduce functional scores. The operator should pay great attention to restoring the lumbo-pelvic lordosis.