Implant density and curve correction in scoliosis surgery using a three-dimensional-based correction strategy

Introduction: The growing trend toward the use of pedicle screws for the operative treatment of patients with idiopathic scoliosis is to provide a three-dimensional (3D) deformity correction using a three-column fixation was observed. Reports have variable recommendations regarding the implant density as well as the configuration of the pedicle screws. This study re-evaluated implant density and curve correction currently based on the 3D correction strategy by comparing it to side-bending correction (SBC). Materials and Methods: Seventy-six adolescent idiopathic scoliosis (AIS) patients who had undergone posterior spinal fusion from 2017 to 2019 visited our specialized center were recruited. Demographic variables and radiological measurements were collected. Patients filled out the Scoliosis Research Society (SRS-22) questionnaire from a mobile device, of which the SRS-22 was digitally adopted using mobile technology and cloud computation. Results: In the 76 AIS patients, 28 (37%) were rigid curves and 48 (63%) were flexible curves. Of the 28 rigid curves (SBC <30%), 13 (46%) patients had low pedicle screw density (PSD), while 15 (54%) had high PSD. Of the 48 flexible curves, 26 (55%) patients had low PSD, while 22 (45%) patients had high PSD. SBC index for the high PSD group (172) is almost the same compared to the low PSD group (174). Conclusions: Using high or low PSD makes the same amount of spinal correction for this group and additional screws do not make significant improvement on spinal correction. Higher screw density instrumentation is associated with the same amount of correction rate, whether in rigid or flexible curves, leading us to postulate that scoliosis correction relates more to intrinsic curve flexibility rather than instrument density.