Durability of Suppl. Rod Constructs-SuppleMentAry Rod Technique for Long-segment Posterior Instrumented Spinal Fusions

This multicenter retrospective comparative cohort study will enroll 1244 patients, who underwent primary or revision long-segment posterior thoracolumbar (TL) instrumented fusion using either a supplementary rod construct or a dual-rod construct. By comparing two groups of patients, ie, patients treated with supplementary rod constructs vs dual-rod constructs, in the setting of long-segment posterior instrumented spinal fusion, this study aims to provide quality evidence regarding the benefits of supplementary rod constructs in reducing the risk of RFs and other mechanical complications. This study shall provide the first long-term clinical evidence on clinical outcome and benefit of supplementary rod constructs. All participating surgeons will be asked to identify a time point, denoted as X, when they started using predominantly either supplementary rod constructs or dual-rod constructs for long-segment posterior TL instrumented spinal fusion. This time point X must be on or before December 31, 2020 (the last eligible date for the index surgery). Participating surgeons will be instructed to select the time point X to be as early within the collection window as feasible to maximize the available FU period. Once the time point X is identified for a participating surgeon, medical records of patients treated by this surgeon will be reviewed to identify consecutive eligible patients with the index surgery done between the time point X and December 31, 2020, inclusive. In the case that an eligible patient had undergone several surgeries during this period, the first primary or revision of long-segment posterior TL instrumented fusion using either a supplementary rod construct or a dual-rod construct is defined as the index surgery. Patients will then be grouped based on the rod constructs into either the supplementary rod construct group or dual-rod construct group. The study has two FU periods: * The first FU period is the first 2 years after the index surgery. The primary analysis will be done using data from the first 2 years of FU. * The second FU period ends on December March 31, 20232024. The duration of this FU therefore ranges from 3 years and 3 months to 10 years and 3 months. The primary study endpoint is the occurrence of the first RF within 2 years after the index surgery.