Radiographic Outcome Differences in Distraction-Based Growing Rod Constructs Using Tandem Versus Wedding Band Connectors

Study Design: Comparative cohort study. Objective: To compare coronal deformity control, lengthening efficacy, and sagittal alignment between distraction-based growing rod constructs utilizing tandem versus wedding band connectors. Summary of Background Data: Different construct designs exist for growing rod treatment of early-onset scoliosis. All use a version of a rod connector, with the two main types being tandem and wedding band. Little data exist to quantify the impact of connector choice on radiographic outcomes of treatment. Methods: A multicenter database of prospectively and retrospectively collected data on early-onset scoliosis patients was reviewed. Patients of any thoracic or thoracolumbar coronal plane deformity whose initial growing rod treatment was initiated before age 10 years and underwent at least 3 years of dual growing rod treatment with either tandem or wedding band connectors were included. Preoperative, immediate postoperative, and prefinal radiographs were reviewed and compared in regard to major curve magnitude, T1–T12 and T1–S1 spinal length, length of instrumentation, and sagittal plane measures. Results: A total of 209 patients were included. The overall percent change from preoperative to prefinal in all radiographic parameters was not different between the two groups indicating similar efficacy in treatment. After controlling for institutional variation, the improvement of the major coronal Cobb angle from preoperative to prefinal was statistically improved for the tandem group (34° vs. 29° p =.002) and the difference in T5–T12 kyphosis from preoperative to prefinal was significantly different between the groups (−6° vs. +1.3° p =.008). Conclusion: We identified little difference in the effects of connector type on radiographic outcomes of patients treated with traditional growing rod, which indicates that both wedding band and tandem connectors function similarly. The small differences detected suggest that tandem connectors may improve major Cobb correction, and wedding band connectors may maintain thoracic kyphosis over time. Level of Evidence: Level III