The selection of upper instrumented vertebra in ankylosing spondylitis thoracolumbar kyphosis

English Keywords:Ankylosing spondylitis  Kyphosis  Pedicle subtraction osteotomy  Vertevertebral column decancellation  Upper instrumented vertebra

English Abstract:

  【Abstract】 Objectives: To determine the optimal selection of upper instrumented vertebra(UIV) in ankylosing spondylitis(AS) thoracolumbar kyphosis. Methods: From January 2010 to May 2013, in Chinese People′s Liberation Army General Hospital, 123 AS thoracolumbar kyphosis cases(110 males, 13 females) treated with pedicle subtraction osteotomy(PSO) or vertevertebral column decancellation(VCD) were retrospectively reviewed. Osteotomied vertebra(OV) of all cases distributed from T11 to L4. According to the relationship between UIV and proximal OV, all cases were divided into Group A, UIV was the third vertebra cranial to the proximal OV(n=64), and Group B, UIV was the forth vertebra or more cranial to the proximal OV(n=59). The two groups were compared between preoperative and the last follow-up with respect to sagittal radiographic parameters[global kyphosis(GK), thoracic kyphosis(TK), thoracolumbar kyphosis(TLK), lumbar lordosis(LL), sagittal vertical axis(SVA)], Oswestry disability index(ODI) and complication occurrence rate. All patients were divided into groups based on the relative position of UIV and apical vertebra(AV): Group AV(the UIV was AV or above, n=34) and Group Non-AV(n=89), the above-mentioned parameters and data were compared again. Results: During the 29.3±3.2(24-60) months of follow-up, no fixation failure occurred. Group A and Group B had no significant differences with respect to age and gender(P>0.05). The mean instrumented segments of Group A were less than those in Group B(P<0.05). Two groups had similar deformity correction rate(P>0.05), ODI improvement(P>0.05) and proximal junctional kyphosis(PJK) occurrence(1/64 vs. 2/59, P>0.05) at the last follow-up. The incidence of complaining about back pain orprotrudent sensation in Group A was lower than that in Group B(P<0.05). The incidence of complaining about back pain or protrudent sensation in Group AV was higher than that in Group Non-AV(P<0.05). Two groups had similar deformity correction rate(P>0.05) and ODI improvement(P>0.05) at the last follow-up. There was no significant difference between two groups in PJK incidence(1/34 vs. 2/89, P>0.05). Conclusions: When PSO or VCD is considered to treat the AS thoracolumbar kyphosis, the 3rd vertebra cranially to the proximal OV is enough for the correction and fixation due to its low incidence of complaining about the protrudent sensation. When UIV is above AV, patient is apt to develop back pain or protrudent sensation.