The polymethyl methacrylate cervical cage for treatment of cervical disk disease Part III. Biomechanical properties.
BACKGROUND
In a previous article, we used the PMMA cervical cage in the treatment of single-level cervical disk disease and the preliminary clinical results were satisfactory. However, the mechanical properties of the PMMA cage were not clear. Therefore, we designed a comparative in vitro biomechanical study to determine the mechanical properties of the PMMA cage.


METHODS
The PMMA cervical cage and the Solis PEEK cervical cage were compressed in a materials testing machine to determine the mechanical properties.


RESULTS
The compressive yield strength of the PMMA cage (7030 +/- 637 N) was less than that of the Solis polymer cervical cage (8100 +/- 572 N). The ultimate compressive strength of the PMMA cage (8160 +/- 724 N) was less than that of the Solis cage (9100 +/- 634 N). The stiffness of the PMMA cervical cage (8106 +/- 817 N/mm) was greater than that of the Solis cage (6486 +/- 530 N/mm). The elastic modulus of the PMMA cage (623 +/- 57 MPa) was greater than that of the Solis cage (510 +/- 42 MPa). The elongation of PMMA cage (43.5 +/- 5.7%) was larger than that of the Solis cage (36.1 +/- 4.3%).


CONCLUSIONS
Although the compressive yield strength and ultimate compressive strength of the PMMA cervical cage were less than those of the Solis polymer cage, the mechanical properties are better than those of the cervical vertebral body. The PMMA cage is strong and safe for use as a spacer for cervical interbody fusion. Compared with other cage materials, the PMMA cage has many advantages and no obvious failings at present. However, the PMMA cervical cage warrants further long-term clinical study.
Chen
Jyi-Feng
JF
Department of Neurosurgery, Chang Gung University College of Medicine & Chang Gung Memorial Hospital, Taoyuan 333, Taiwan.
Lee
Shih-Tseng
ST
D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae; D019245:Compressive Strength; D004548:Elasticity; D016268:Internal Fixators / Q000592:standards*; D008422:Materials Testing / Q000379:methods / Q000706:statistics & numerical data*; D019635:Neurosurgical Procedures / Q000295:instrumentation*; D019904:Polymethyl Methacrylate / Q000592:standards*; D013123:Spinal Fusion / Q000295:instrumentation*; D016474:Weight-Bearing
D019904:Polymethyl Methacrylate