矢状面骶骨铅垂线与远端融合椎的距离在青少年特发性脊柱侧凸术后发生交界性后凸的临床意义

Clinical significance of the distance between LIV and SSVL in posterior fusion strategy for adolescent idiopathic scoliosis patients

目的明确矢状面骶骨后上角铅垂线与远端融合椎的距离在青少年特发性脊柱侧凸融合节段选择中的意义。方法回顾性分析165例从2005至2008年接受后路椎弓根螺钉固定矫形手术的AIS患者。排除标准:非特发性脊柱侧凸,下端融合椎低于L4,前后路联合手术,后路钉钩混合手术,翻修手术,影像学资料不完整。共有88例纳入,分为三组,PJK(Proximal Junctional Kyphosis)组,DJK(Distal Junctional Kyphosis)组,对照组。PJK定义为融合节段最上端的椎体(UIV,Upper instrumented vertebrae)的下终板和其近端相邻第二个椎体的上终板延长线的夹角改变大于10°。DJK定义为远端融合椎(LIV,lowest intrumented vertebrae)上终板到远端融合椎相邻一个椎体的下终板之间的角度改变大于5°。选择没有其他任何并发症的病人作为对照组。比较三组之间年龄、Risser征、上胸弯、主胸弯、矢状面胸椎后凸、腰椎前凸以及远端融合椎和矢状面骶骨铅垂线(SSVL,sagittal Sacral Vertical Line)的距离。结果其中15例在随访中发生近端交界性后凸畸形,列为PJK组。8例发生远端交界性后凸,列为DJK组。将36例无其他任何并发症的随访超过2年的病人作为对照组。PJK组、DJK组和对照组三组在术前胸椎后凸、腰椎前凸及术后胸椎后凸、腰椎前凸及矢状面矫正度数的差值上均没有显著差异(P>0.05)。但是PJK组年龄及Risser征均较对照组小,冠状面主胸弯及近胸弯角度均较对照组小,而且术前矢状面近端后凸角度较对照组大,有统计学意义(P<0.05)。LIV和SSVL在术后和末次随访之间的距离PJK,DJK和C组之间是明显不同的。当LIV的中点落于SSVL线腹侧容易出现PJK,而LIV位于SSVL线的背侧时,则容易出现DJK。结论如果下端椎位于矢状面骶骨铅垂线腹侧,可能增加近端交界性后凸的风险,相反,如果位于矢状面骶骨铅垂线背侧,容易继发远端交界性后凸。所以,术后下端椎与矢状面骶骨铅垂线可能预测近端或远端交界性后凸的发生。

Objective To determine the importance of the distance between lowest instrumented vertebrae （LIV） and sagittal sacral vertical line （SSVL） in posterior fusion strategy for adolescent idiopathic scoliosis （AIS） patients. Methods This retrospective review included 165 consecutive AIS inpatients from 2005 to 2008 who underwent the posterior corrective surgery using pedicle screwconstructs. 3 groups were identified：proximal junctional kyphosis （PJK）, distal junctional kyphosis （DJK）, and control （C）. PJK was defined as 〉10° angular change between the superior endplate of the upper instrumented vertebra-2 （UIV-2） to the inferior endplate ofUIV between postoperation and the final follow-up. DJK was defined as 〉 5° angular change between the superior endplate of the LIV to the inferior endplate of LIV＋I between postoperation and final follow-up. Regardless of whether or not PJK/DJK oeeurred before or after 2 years, all patients were included. In C group, a subset of AIS patients with more than 2 years follow-up without complications were selected. Various anatomic parameters were measured and compared between the PJK, DJK and C group to identify risk factors. Results After excluding other complications and short follow-up less than 2 years for C group, 15 cases in PJK （17%）, 8 cases in DJK （9%） and 36 eases in C remained. There was no significant difference among PJK, DJK and C in terms of preoperative thoracic kyphosis or its correction （P〉0.05）. Younger age, lower Risser stage, smaller proximal thoracic （FF） and main thoracic （MT） eurves had significantly more PJK （P〈0.05）. However, the distance between LIV and SSVL in postoperation and final follow-up was signifieantly different in both PJK and DJK compared to C. In contrast to byperkyphotic patients, SSV was poorly defined in AIS because many patients had hypokyphosis preoperatively. Conclusion If LIV is located too anterior than SSVL, the chance of PJK increases. In contrast, if it is too posterior, the chance of DJK increases. The postoperative distance between LIV and SSVL can predict the possibility of PJK or DJK during follow-up.