Evaluation of preoperative calculation methods of osteotomy size in ankylosing spondylitis with thoracolumbar or lumbar kyphosis

Abstract

Abstract Background To evaluate the accuracy of different preoperative calculation methods of osteotomy size in ankylosing spondylitis with thoracolumbar or lumbar kyphosis and analyze its clinical significance. Methods Twenty-two cases of AS patients with thoracolumbar or lumbar kyphosis, from January 2015 to December 2018, who underwent one-level SPO surgery in our hospital, were retrospectively reviewed. The sagittal parameters were measured at pre-operation and last follow up using Surgimap software, and theoretical values of sagittal parameters were calculated according to pre-operative PI. The osteotomy angles of different methods were measured using Surgimap software. Paired t test was used to for the statistical analysis. Results The mean follow-up time of all patients was 30.00 $$\pm$$ ± 3.56 months. The osteotomy sites were located at T12 in 3 cases, L1 in 6 cases, L2 in 9 cases, and L3 in 4 cases. Compared to pre-operative sagittal parameters, post-operative PT, SS, LL, and SVA were significantly improved (P$$<$$ < 0.05). Compared to the OVA (46.57 $$\pm$$ ± 2.32 $$^\circ$$ ∘ ), there was a significantly larger angle predicted by Surgimap method (53.80 $$\pm$$ ± 9.79 $$^\circ$$ ∘ ), CAM-HA method (56.61 $$\pm$$ ± 8.58 $$^\circ$$ ∘ ), and HP-HA method (60.07 $$\pm$$ ± 13.58 $$^\circ$$ ∘ ), respectively (P$$<$$ < 0.05). But no significant difference was found between the postoperative osteotomy angle and those of SFA method (51.24 $$\pm$$ ± 12.14 $$^\circ$$ ∘ ) and FBI method (48.08 $$\pm$$ ± 12.49 $$^\circ$$ ∘ ) (P$$>$$ > 0.05). Conclusion For AS patients with thoracolumbar or lumbar kyphosis, the SFA method, FBI method, and Surgimap method can be used to predict the osteotomy angle precisely, however, considering the rationality of parameter settings and the operability, SFA method is relatively more suitable for such population.