Patterns of later-stage growing rod fracture and their relationship with thoracic hyperkyphosis in early onset scoliosis

Growing rod surgery, as a distraction-based technique has been widely used to surgically treat early onset scoliosis (EOS) while preserving spinal growth. However, implant-related complications, particularly growing rod fracture (RF) are common. While several risk factors such as rod diameter are known, the patient-specific or radiological factors remains unclear, especially the late stages of growing rod surgery treatment in EOS. This study aims to investigate the incidence, fracture patterns, and influencing factors of later-stage RF prior to final fusion in patients with EOS. A total of 38 EOS patients who underwent growth-friendly surgery using traditional dual growing rod were divided into a rod fracture group (RF +, n = 15) and a non-fracture group (RF −, n = 23) based on the occurrence of rod breakage at the growing rod graduation (final follow-up). Demographic data such as obesity (defined as > 95th percentile) and radiological parameters such as Cobb’s angle, the spinal height gain, and thoracic kyphosis (TK) were included in this study. The occurrence of RF at the final follow-up was 39.5% (15 of 38), with the most common fracture site being just above the tandem connector (80%), corresponding to the apical region or between the thoracic and lumbar apices. The RF+ group had a significantly higher proportion of obesity compared to the RF- group (40.0% vs. 4.3%, P = 0.010). Initial hyper-TK (> 50°) was significantly more frequent in the RF+ group (46.7% vs. 13.0%, P = 0.030). Notably, all patients (100%, n = 5) who presented with both preoperative hyper-TK and obesity experienced RF. RF at growing rod graduation occurred in 39.5% of the study cohort, predominantly in the region proximal to the tandem connector. Initial hyper-TK and obesity were found to be significantly associated with the occurrence of RF prior to final fusion following growing rod surgery in EOS. III.