Posterior instrumentation and reduction for L5/S1 spondylolisthesis in adolescents: the immediate reduction outcome and its associated risk factors

English Keywords:Adolescent  Spondylolisthesis  Isthmic  Dysplastic  Reduction

English Abstract:

  【Abstract】 Objectives: To identify the immediate reduction outcome and its associated risk factors of posterior instrumentation and reduction for adolescent patients with L5/S1 spondylolisthesis. Methods: In this study, adolescents with isthmic(n=21) or dysplastic(n=9) spondylolisthesis at L5/S1 were recruited in our hospital from May 2002 to Deccmber 2014. The average age was 14.5 years(range, 10-20 years). There were 13 males and 17 females. According to Meyerding grade, 16 cases in grade Ⅰ, 7 in Ⅱ, 4 in Ⅲ and 3 in Ⅳ. All patients underwent posterior pedicle screw instrumentation(L5-S1 single segment fusion for 24 cases, L4-S1 double segment fusion for 6 cases). The relationship between reduction rate and preoperative radiographic parameters including lumbar spine lordosis Cobb′s angle, pelvic incidence, pelvic tilt, sacral slope, disc height, slippage rate, slippage angle and slippage distance was evaluated. Results: Before surgery, the average lumbar lordosis(LL) was 52°±16°, the average pelvic incidence(PI) was 62°±13°, the average pelvic tilt(PT) was 24°±16°, the average sacral slope(SS) was 38°±15°, the average slippage percentage(SP) was (33.6±24.2)％, the average slippage angle(SA) was 13°±9°, the average slippage distance(SD) was 9.1±6.6mm, and the average intervertebral disc relative height was 0.31±0.1. After the posterior instrumentation and fusion surgery, the average reduction rate of L5 slippage was (87.3±14.7)％. Among the preoperative radiographic parameters, immediate reduction rate was found to be strongly correlated with the disc relative height and LL, while negatively correlated with PT, SP, SA and SD. Conclusions: Effective reduction of L5/S1 slippage in adolescents can be successfully achieved by posterior instrumentation and reduction. Various factors may impact on the immediate reduction rate including etiology, fusion method, slip severity, and disc relative height. During the surgery, managing the intervertebral disc help improve reduction rate of slippage.