Validity of the Roussouly classification system for assessing distal junctional problems after long instrumented spinal fusion in degenerative scoliosis.

PURPOSE: To evaluate the validity of the Roussouly classification system for assessing distal junctional problems (DJP) after long instrumented spinal fusion in degenerative scoliosis.
METHODS: Sixty-four patients with degenerative scoliosis and long-segment fixation receiving treatment at our hospital between December 2012 and December 2018 were retrospectively analyzed. Patients were classified preoperatively and postoperatively (Roussouly classification) and divided into DJP and control groups. We observed whether patients restored to their preoperative Roussouly classification (based on pelvic incidence [PI]) postoperatively.
RESULTS: The incidences of DJP were 11.11% and 50% in patients who did and did not match their sagittal Roussouly classification immediately postoperatively, respectively. The adjusted Chi-square test that showed whether the sagittal profile matched the Roussouly classification immediately after surgery was statistically significant (P = 0.012). PIs were 55.83 ± 4.94 and 47.21 ± 10.81 in the DJP and non-DJP groups, respectively (t' = 4.367, P < 0.001). Distal junctional kyphosis angles were 6.33 ± 4.19° and 11.56 ± 5.02° in the DJP and non-DJP groups, respectively (t = - 2.595, P = 0.015). Preoperative PI-lumbar lordosis values were 29.14 ± 13.82 and 16.67 ± 11.39 in the DJP and non-DJP groups, respectively (t = - 2.626, P = 0.013). The logistic regression model showed that patients whose Roussouly classification did not match the postoperative PI value were more likely to have DJP (odds ratio [OR] = 4.01, 95% confidence interval [CI]: 0.51-31.61) and preoperative distal junctional kyphotic changes.
CONCLUSION: If the postoperative sagittal profile can be restored to match the patient's own PI value, use of the Roussouly classification can greatly reduce the possibility of postoperative DJP.