The impact of ossified anterior longitudinal ligaments surrounding osteotomy vertebra on the lordosing capability of pedicle subtraction osteotomy in thoracolumbar kyphotic deformity secondary to ankylosing spondylitis / 中华骨科杂志

ABSTRACT

Objective To investigate anterior longitudinal ligaments (ALL) ossified surrounding osteotomy vertebra impact the lordosing effect of pedicle subtraction osteotomy (PSO) in patients with thoracolumbar kyphosis secondary to ankylosing spondylitis (AS).Methods We retrospectively reviewed 102 AS patients with thoracolumbar kyphosis treated with single-level PSO at our institution from September 2007 to August 2015.There were 92 male and 10 female.The average age was (35.6±11.8)years old (range from 17 to 65 years old).Patients were stratified into ossified group (54 cases) and non-ossified group (48 cases)based on the presence of ALL ossification adjacent to osteotomy vertebra.Compared the contribution of adjacent disc wedging to total correction of each PSO segment between the ossified and non-ossified groups.The long-term correction loss of spine and pelvic sagittal morphology were also evaluated and compared between the 2 groups.Results Patients in the ossified group accomplished significantly lower amount of correction in single level segment of PSO (36.3°±6.9° vs.41.5°±6.9°),and there was significant difference between the two groups.The contribution of adjacent disc wedging to total correction of PSO was significantly larger in the non-ossified group (22.9％ vs.7.8％,P＜0.001).For subgroups with a minimum 2 year follow-up,loss of corrections concerned sagittal vertical axis (SVA),which was (1.7±4.5) cm vs.(-0.2±4.0) cm in ossified group and non-ossified group,and there was significant difference between the two groups.Pelvic tilt (PT) was 3.5°±8.2° vs.2.0°± 10.4°,lumbar lordosis (LL) was-7.9°±11.9° vs.-0.1°± 11.9° and sacral slope (SS) was 4.5°±9.3° vs.1.6°±7.9°,and there were all significant differences between the two groups.The change of adjacent disc wedging angle was marginally higher in the unossified group (-2.1°±6.2° vs.-0.1°±3.7°,P=0.09),but there was no significant difference between the two groups.No significant correction loss of osteotomy angle was observed in both groups.Conclusion Osteotomy vertebrae accompanied by unossified adjacent ALL in PSO of AS were prone to create more disc-originated lordosing effect immediately after surgery.However,a correction loss might occur more commonly during a long term follow-up.