A comparison of stainless steel and CP titanium rods for the anterior instrumentation of scoliosis.
Use of 4.0 mm and 5.0 mm steel rods have resulted in proximal screw pullout. Titanium rods, which encompass a reduced yield point, may increase the effective stiffness of the construct when used with segmental anchors. Seven human thoracic spines were loaded in axial compression, axial torsion, flexion, extension, and lateral bending. Testing was performed on intact, discectomy and simulated bony fusion specimens. Specimens were randomly instrumented with 4.0 mm and 5.0 mm steel, and 4.5 mm CP Ti rods. In compression and torsion, the intact spine demonstrated increased stiffness with respect to all instrumentation employed in a discectomy condition. No significant differences between the intact and the instrumentation systems were detected for torsion or compression under simulation of fusion. Under flexural loading, no significant differences were detected between the intact specimen and the instrumentation systems. When used in conjunction with segmental force anchors, the use of CPTi rods which posses reduced yield points can provide sufficient rigidity as compared to stainless steel rods of comparable diameter. Implants of reduced yield point will permit permanent deformation with low force. Screw pullout may result when high yield materials are employed in conjunction with anchors.
Haher
Thomas
T
Department of Surgery, Lutheran Medical Center, Brooklyn, NY 11220, USA. Tomhaher@aol.com
Ottaviano
Danielle
D
Lapman
Peter
P
Goldfarb
Brian
B
Merola
Andrew
A
Valdevit
Antonio
A
D001860:Bone Plates; D002102:Cadaver; D019245:Compressive Strength; D004548:Elasticity; D019544:Equipment Failure Analysis / Q000379:methods*; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D012600:Scoliosis / Q000503:physiopathology* / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013193:Stainless Steel; D013904:Thoracic Vertebrae / Q000502:physiology* / Q000601:surgery*; D014025:Titanium; D016474:Weight-Bearing
D013193:Stainless Steel; D014025:Titanium