Low Density Implants in Adolescent Idiopathic Scoliosis Correction

Abstract

Background: Adolescent idiopathic scoliosis (AIS) is the most common type of spinal deformity, affecting the physical and mental health of adolescent. The low density (LD) screw constructs can provide significant radiographic and clinical outcomes. The use of fewer pedicle screws indicated a reduction of hospital expenses and risk of neurologic complications. We aim to evaluate perioperative functional and radiological outcomes of low density pedicle screw patterns by radiographic, perioperative outcomes in AIS patients.

Methods: This is a prospective case study of 30 patients with AIS. Functional evaluation was done by SRS 30 questionnaire pre operatively and at final follows up. Screw density was calculated by number of screws per level in post op. AP film. Radiological outcomes was evaluated by Measurement of Cobb s angles in AP standing film preoperatively, degree of correction post-operative at 1, 3, 6, 12 months, loss of correction and relation between screws density, degree of correction and loss of correction.  Thirty AIS patients underwent primary posterior fusion with pedicle screw instrumentation were prospectively reviewed. Implant density was defined as the screws number per fused spinal segment. The correlations between three-dimensional curve correction, Functional and radiographic parameters and anchor density were analyzed, implant density in this study was below 1.6 screws / level.

Results: This study showed that the mean age of patients was 15.5 years, We achieved correction of mean preoperative curve 59.47° degree to 17.83° degree (69.33 %) by low density implants constructs (mean: 1.12). SRS 30 score improved from 75.63 ± 8.18 preoperative to 127.13 ± 3.39 postoperative p value < 0.001. Mean loss of correction 2.9° degree (6.9%) after 12 months follow up. There was positive but non-significant correlation between screws density and correction rate (P value = 0,089). Operative time and blood loss significantly increase with screws density (P value =0,001).

Conclusions: Low anchor density with longer fusion level achieves excellent curve correction and stability. Low density implants constructs decrease operative time, blood loss, cost and risk of complications.