Impact Of Connector Placement And Design On Bending Stiffness Of Spinal Constructs
Objective: To evaluate the stability of multiple rodâ€“connector construct designs using a mechanical 4-point bending testing frame. Methods: A mechanical study was used to evaluate the bending stiffness of 3 connectors across 12 different configurations of rodâ€“connectorâ€“rod constructs. Stability was evaluated in flexionâ€“extension and lateral bending. Combinations of rods having 1 of 3 diameters (4.0 mm, 5.5 mm, and 6.0 mm) connected by 1 of 3 connector types (parallel open, snap-on, and hinged) were compared. Configurations with single connectors and with double connectors with variable spacing were also compared to simulate revision surgery conditions. Results: Constructs consisting of 4.0-mm rods connected to 4.0-mm rods were significantly less stiff as the total number of connectors used in a series exceeded 2. When single-connector configurations were compared, parallel open rod connectors demonstrated greater stiffness in flexionâ€“extension than hinged open connectors, whereas hinged open connectors demonstrated greater stiffness in lateral bending. Using double connectors increased stiffness of 4.0- to 4.0-mm rod configurations in flexionâ€“extension and lateral bending, 4.0- to 6.0-mm rod configurations in flexionâ€“extension, and 5.5- to 6.0-mm rod configurations in lateral bending. Spacing the double connectors significantly improved lateral bending stiffness of 4.0- to 4.0-mm and 5.5- to 6.0-mm rod configurations. Conclusions: Our data indicate that the design, number, and placement of rod connectors have a significant impact on the bending stiffness of a surgical construct. Such mechanical data may influence construct design in primary and revision surgeries of the cervical spine and cervicothoracic junction.
Digital Object Identifier (DOI)
Godzik, Jakub; Hool, Nick; Dalton, Jonathan F.; Whiting, Alexander C.; Newcomb, Anna G.U.S.; Kelly, Brian P.; and Crawford, Neil R., "Impact Of Connector Placement And Design On Bending Stiffness Of Spinal Constructs" (2019). Translational Neuroscience. 116.