Multiple-rod constructs in thoracolumbar reconstructive spine surgery: Building a novel classification of heterogeneous rods for multiple etiologies (CHRoME) scoring system

Background: Surgical management of complex spine disorders with instrumentation continues to expand. This present study investigates the possible therapeutic uses of a categorization nomenclature system that is widely recognized for multiple-rod constructs in spine reconstruction surgery utilizing a modified Delphi technique. Methods: An extensive literature review identified articles on multiple-rod constructs where definitions and names of multiple-rod constructs were categorized according to inclusion criteria. An expert panel of spine surgeons using a modified Delphi process established the framework of terms for the multiple-rod scheme for the classification of heterogeneous rods for multiple etiologies (CHRoME). Four key questions based on a review of spinal x-ray films and relevant clinical indications were used to create CHRoME: number of rods present, extension of the rostral construct, purpose of the working rod, and number of screws for pelvic fixation. Next the CHRoME score was used by a panel of spine surgeons to evaluate images from a sample of 10 case scenarios. Results: Our expert panel were able to classify images with very good agreement and high rates of inter-rater reliability (kappa coefficient 0.83; 95 % CI: 0.69–0.96). With a kappa coefficient of 0.94 (95 percent CI, 0.90 to 0.99), the intra-rater reliability was almost flawless. Conclusions: The novel classification of heterogeneous rods for multiple etiologies (CHRoME) score, based on 4 essential questions, is used to define multiple-rod constructs and gives a consistent description of the numerous ways that instrumentation is used in spine surgery.