Selection Of Distal Fusion Vertebrae Of Idiopathic Scoliosis With Lumbar

Study design A prospective study is conducted.ObjectiveTo investigate the radiographic change of adolescent idiopathic scoliosis(AIS) patients undergone posterier pedicle screw fixation and fusion using a new method of choosing the lower instrumented vertebra(LIV).BackgroundAdolescent idiopathic scoliosis is one of the most common deformity in musculoskeletal system. The pedicle screw instrumentation technique have become the most widely used surgical technique in the treatment of AIS. Spinal fusion is as important as the fixation in the surgery. Appropriate selection of the fusion level plays an important role in achieving better correction, preserving more mobile segments and decreasing the rate of trunk decompensation, adding-on phenomenon and low back pain. However, there is no commonly accepted criteria for choosing the lower instumented vertebra, especially in cases needed fusion to the thoracolumbar/lumbar level.MethodsThis study analyzed patients prospectively treated with posterier pedicle screw fixation and Moe’s bone grafting fusion by the same surgeon according to the lower instrumented vertebra selecting criteria:The touched vertebra(TV) was defined as the most cephalad vertebra touched by central sacrum vertical line(CSVL), and the touched vertebra must fulfil3requirements when selected as the LIV:(1) The Nash-Moe rotation grade must be less than or equel to Grade Ⅰ;(2) CSVL falls between the pedicles of the touched vertebra in the preoperative supine concave bending radiograph;(3) There is no kyphosis in thoracolumbar/lumbar segments. All cases had a minimum follow-up period of12months. The pre-operative, post-operative and follow-up full length cassette standing radiographs, supine concave bending radiographs were reviewed and measured by an independent surgeon. The measurement included Cobb angle, trunk shift, LIV tilting(LIVT), LIV distal disc angulation(LIVA), angle between LIV and pelvis. Trunk decompensation is defined as trunk shift greater than2centimeters. Statistical analysis is conducted between the data of different junctures. The location of touched vertebra(TV), stable vertebra(SV), neutral vertebra(NV) is recorded and compared.ResultsSixty-one patients met the inclusion criteria(5males and56females),the average age was14.3year. The curve types included PUMC Ⅰa in3cases, Ⅰb in6cases, Ⅰc in5cases, Ⅱa in6cases, Ⅱb1in1cases, Ⅱc1in5cases, Ⅱc3in4cases, Ⅱd1in19cases, Ⅱd2in3cases, Ⅲa in3cases, Ⅲb in6cases.The results are as follow:(1)the TS was (1.88±0.98)cm before surgery and (0.92±0.76)at the last follow-up(P<0.001),5cases presented trunk decompensation but none of them was a new one compared to the preoperative radiograph;(2)the LIVT was22.75°±4.72°before surgery and5.18°±3.22°at the last follow-up(P<0.001);(3) the LIVA was7.20°±5.08°before surgery and4.21°±3.36°at the last follow-up(P<0.001);(4) compared to SV, selecting TV as LIV can save average (1.31±0.47) segments.ConclusionChoosing the touched vertebra(TV) as the lower instrumented vertebra(LIV) is a safe and effective method. It can achieve satisfactory correction and can save more mobile segments compared with the traditional criteria.