Static and dynamic analysis of five anterior instrumentation systems for thoracolumbar scoliosis

A nondestructive biomechanical investigation among five anterior spinal instrumentation systems for scoliosis.

The purpose of this study is to analyze the static and dynamic biomechanical stability of five different systems.

Although a variety of anterior spinal instrumentation systems for scoliosis are available, very few attempts have been made at comparative biomechanical studies.

Thirty calf spines were underwent static biomechanical tests, including flexion-extension, axial rotation, and lateral bending loading modes in the multisegmental spinal model. Five anterior instrumentation systems included: 1) Texas Scottish Rite Hospital system; 2) Bad Wildungen Metz; 3) anterior ISOLA; 4) Cotrel-Dubousset Hoph; and 5) Kaneda Anterior Scoliosis System. The initial and postfatigue stability after a cyclic loading test were analyzed by measuring the range of motion at instrumented segments compared to the intact within the same specimen (% to intact).

Two-rod systems showed a significant decrease in range of motion compared to one-rod systems in flexion-extension (P < 0.001) and axial rotation (P < 0.05). In lateral bending, all systems demonstrated a significant decrease in range of motion of less than 40% to the intact (P < 0.001). After cyclical loading test, all systems increased in range of motion. In flexion-extension, one-rod systems depicted a significant increase in range of motion, compared to two-rod systems (P < 0.05).

In the initial stability analysis, two-rod systems are superior to one-rod systems. For one-rod systems, repeated physiologic loading may result in reduced stability in flexion-extension.