Does higher screw density improve radiographic and clinical outcomes in adolescent idiopathic scoliosis? A systematic review and pooled analysis.

OBJECTIVE The radiographic and clinical outcomes of low-density (LD) versus high-density (HD) screw constructs in patients with adolescent idiopathic scoliosis (AIS) treated with all-pedicle screw constructs are still controversial. A systematic review and pooled analysis were performed to compare radiographic, perioperative, and quality-of-life (QOL) outcomes and complications in patients with moderate AIS treated with LD or HD screw constructs. METHODS The MEDLINE, Embase, and Web of Science databases were searched for English-language articles addressing LD versus HD screw constructs in AIS patients treated with all-pedicle screw constructs. The division of LD and HD groups was based on relative screw density and screw techniques. This systematic analysis strictly followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, and all articles included in the analysis met the criteria specified in the guidelines. Two reviewers independently assessed the quality of the studies using the Newcastle-Ottawa Scale. Date on radiographic, perioperative, and QOL outcomes and complications were extracted from the included studies. RESULTS Twelve studies, involving a total of 827 patients (480 treated with LD constructs, 347 with HD), were analyzed-1 randomized controlled trial, 1 quasi-randomized controlled trial, and 10 retrospective studies. The patients' age at surgery, preoperative Cobb angle of the major curve, amount of thoracic kyphosis, and major curve flexibility were reasonably distributed, and no statistically significant differences were found. Regarding the outcomes at most recent follow-up, there were no significant differences in the Cobb angle of the major curve (mean difference 0.96°, 95% CI -0.06° to 1.98°, p = 0.06, I2 = 1%), major curve correction (mean difference -0.72%, 95% CI -2.96% to 1.52%, p = 0.53, I2 = 0%), thoracic kyphosis (mean difference -1.67°, 95% CI -4.59° to 1.25°, p = 0.26, I2 = 79%), complications (odds ratio [OR] 0.66, 95% CI 0.31-1.42, p = 0.29, I2 = 0%), and QOL outcomes. Reduced operative time (mean difference -48.56 minutes, 95% CI -82.69 to -14.43 minutes, p = 0.005, I2 = 87%), blood loss (mean difference -77.85 ml, 95% CI -153.10 to -2.60 ml, p = 0.04, I2 = 0%), and hospital charges (mean difference -$5.92K, 95% CI -$6.59K to -$5.26K, p < 0.00001, I2 = 0%) were found in the LD group, compared with the HD group. CONCLUSIONS LD and HD screw constructs are both associated with satisfactory radiographic and QOL outcomes with few complications. This study supports the use of LD screw constructs for the treatment of moderate AIS, because they resulted in reduced operative time, blood loss, and hospital charges while maintaining radiographic and QOL outcomes and complication rates similar to those achieved with HD screw constructs.