Fig. 3

Visualization of the changes in the BKA (96 included patients) of the thoracic and lumbar spine. The time to the radiological follow-up at the thoracic spine were: Follow-up 1 (t1): 14.4 ± 13.9 months and follow-up 2 (t2): 41.8 ± 36.7 months; The time to the radiological follow-up at the lumbar spine was: Follow-up 1 (t1): 22.9 ± 19.3 months and follow-up 2 (t2): 52.6 ± 48.8 months. At the thoracic spine (A; 23 patients) a mean preoperative BKA of − 12.8° ± 6.5° could be significantly corrected by 10.3° (reduction) and a statistically significant loss of reduction during the follow-up by − 1.7° (t2) was observed. At the lumbar spine (B; 73 patients), a mean preoperative BKA -9.0° ± 5.7° could be significantly reduced by 10.7° (reduction) and a statistically significant loss of reduction during the follow-up by − 2.7°(t2) was observed. * indicates p < 0.05