Optimal pedicle screw density for the treatment of adolescent idiopathic scoliosis (AIS) remains unknown. It is not clear whether higher implant density results in better clinical outcomes. Large variability in implant density exists among hybrid or all screw constructs. Significant heterogeneity exists with respect to the number of sublaminar bands (SB) used, and the influence of SB density on curve correction in the treatment of AIS.

We hypothesize that increased SB density does not improve sagittal or coronal plane curve correction.

A single-center, retrospective study of 131 consecutive patients (118 females) with Lenke 1 adolescent idiopathic scoliosis, all operated between 2012 and 2015 by two surgeons using identical surgical technique and type of instrumentation (SB hybrid instrumentation treatment). SB density was measured using the number of SB reported as well as the number of vertebrae instrumented. Radiographic measurements included preoperative thoracic curve flexibility, Cincinnati reduction index (CRI), and postoperative thoracic Cobb (POCC) and kyphosis (POKC) angle correction measured on immediate postoperative radiographs and at 2 years postoperatively.

Median patient age was 15.6 years (IQR, 12–18). The median SB density was 0.4 (IQR 0.4–0.5). No statistically significant correlation was identified between SB density and CRI (p=0.71), POCC (p=0.55), or POKC (p=0.61) at 2-years postoperatively. Preoperative curve flexibility was found to have significant effect both on immediate (r=−3.02, p<0.001) and 2-year (r=−2.69, p<0.001).

SB utilized as a part of a hybrid construct for patients with flexible Lenke I AIS achieve satisfactory deformity correction regardless of SBd. The use of low SB density is appropriate for a subset of patients with flexible Lenke 1 adolescent idiopathic scoliosis.