Abstract
Few biomechanical data exist regarding whether the polyetheretherketone (PEEK) spacer or titanium spacer is better for posterior lumbar interbody fusion (PLIF). This study evaluated the biomechanical influence that these types of spacers with different levels of hardness exert on the vertebra by using finite element analysis including bone strength distribution. To evaluate the risk of spacer subsidence for PLIF, we built a finite element model of the lumbar spine using computed tomography data of osteoporosis patients. Then, we simulated PLIF in L3/4 and built models with the hardness of the interbody spacer set as PEEK and titanium. Bones around the spacer were subjected to different load conditions. Then, fracture elements and some stress states of the two modalities were compared. In both models of PLIF simulation, fracture elements and stress were concentrated in the bones around the spacer. Fracture elements and stress values of the model simulating the PEEK spacer were significantly smaller compared to those of the titanium simulation model. For PLIF of osteoporotic vertebrae, this suggested that the PEEK spacer is in a mechanical environment less susceptible to subsidence caused by microfractures of bone tissue and bone remodeling-related fusion aspects. Therefore, PEEK spacers are bio-mechanically more useful.
Highlights
It was observed that the intensity and range of Drucker-Prager stress for LS-Titanium were higher than those for LS-PEEK and tended to concentrate around the spacer, especially the spacer on the left side
The mean values of Drucker-Prager stress, strain energy density (SED), and minimum principal strain in areas 1 to 20 of the bones around the L3 left spacer under flexion and extension conditions were obtained, and a significant difference was identified between the strain values of LS-PEEK and LS-Titanium (Table 2)
posterior lumbar interbody fusion (PLIF) models were constructed by using an osteoporotic vertebra model using digital imaging and communications in medicine (DICOM) data of patient-specific computed tomography (CT) scans and implants was constructed, and comparisons of the mechanical behavior of each model indicated that, for PLIF, the use of the PEEK spacer is mechanically more advantageous than the use of a titanium spacer
Summary
PLIF, which uses posterior fixation with an interbody spacer filled with a bone graft and pedicle screw (PS), has been widely adopted as a treatment option that provides stability until spinal fusion occurs [2,3,4,5]. This contributed to a higher fusion rate. Biomechanical factors are important when comparisons between those spacers are performed to determine the significance associated with durability, stress shielding, microdamage, and bone remodeling This is a highly important subject, there is little biomechanical evidence regarding such biomechanical factors
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