Table 1.
Characteristics of biomechanical studies
| Author (yr) | Design of study | Level of evidence | No. of subjects | Method | Conclusions |
|---|---|---|---|---|---|
| Santoni et al. [17] (2009) | Human cadaveric study | 4 | 14 Lumbar vertebral bodies (L1–L5) | Comparing CBT, PS screw fixation strength: pullout and toggle test | CBT screw fixation: uniaxial yield pullout load (30% higher than PS); pullout resistance, toggle testa) |
| Perez-Orribo et al. [31] (2013) | Human cadaveric study | 4 | 28 Specimens | Comparing stability of CBT and PS | CBT screw fixation: stiffness, stabilitya) |
| Matsukawa et al. [20] (2014) | In-vivo analysis of insertional torque | 2 | 48 Patients | Comparing CBT, PS screw fixation strength: insertional torque measurement | CBT screw fixation: insertional torque (1.7 times higher than PS) |
| Matsukawa et al. [22] (2016) | Analysis of finite element model | 4 | 17 Patients (L4, L5 vertebral bodies) | Comparing CBT, PS screw fixation strength: measurement of axial pullout strength and applying flexion, extension, lateral bending, axial rotation force in spondylolytic vertebrae and normal vertebrae | CBT screw fixation strength in spondylolytic vertebrae: pullout strengtha); flexion, extension, lateral bending, axial rotation force (lower than PS); pullout, flexion, extension, lateral bending, axial rotation strength is lower than normal vertebrae |
| Sansur et al. [24] (2016) | Human cadaveric study | 4 | 8 Specimens | Comparing CBT, PS screw fixation strength: fatigue testing (tensile load to failure pullout testing) | CBT screw fixation: increase in mean load at failure in lower vertebral segment |
| Matsukawa et al. [23] (2016) | Analysis of finite element model | 2 | 20 Lumbar vertebral bodies | Simulation and testing of CBT screw fixation Strength of single screw: axial pullout strength Paired screw construct: simulation of flexion, extension, lateral bending, axial rotation Calculation of bone-screw interface equivalent stress value |
Larger-diameter screws: increased pullout and vertebral fixation strength; decreased equivalent stress around screws Fixation force of CBT screws depends on screw size. Ideal screw size for CBT: diameter larger than 5.5 mm, length longer than 35 mm |
| Li et al. [27] (2018) | Human cadaveric study | 4 | 14 (31 lumbar vertebral bodies) | Comparing CBT, PS screw fixation strength: one side CBT, the other side PS screw fixation on vertebral body; measurement of maximal insertional torque, pullout and cyclic fatigue test was done. | CBT screw fixation: higher maximum insertional torque, axial pullout strength; higher failure load for displacing screw than PS screw fixation |
| Ninomiya et al. [28] (2016) | Clinical study | 4 | 21 Patients | Comparing CBT, PS screw fixation in degenerative spondylolisthesis: measurement of lumbar lordosis, percent slippage | CBT screw fixation: pre- and postoperative slippagea) |
| Baluch et al. [32] (2014) | Human cadaveric study | 4 | 17 Vertebral bodies | Comparing CBT, PS screw fixation strength: one side CBT, the other side PS screw fixation on vertebral body; measurement of resistance to toggle testing (by increasing cycling craniocaudal toggling) | CBT screw fixation: more resistance to craniocaudal toggling |
| Oshino et al. [25] (2015) | Animal cadaveric study | 5 | 20 Lumbar vertebral bodies | Comparing CBT, PS screw fixation: measurement of ROM by bending and rotational force | CBT screw fixation: mean ROMs, intervertebral stabilitya) |
| Calvert et al. [33] (2015) | Human cadaveric study | 4 | 10 Specimens (L3, L4) | Comparing CBT, PS screw fixation: test of pullout strength to fail and then salvaged with screws of the opposite trajectory | CBT screw and PS fixation each obtain proper construct stiffness and pullout strength when used for revision at the same level. → Both CBT screw and PS fixation may be used as rescue option in compromised screw construct in lumbar spine. |
| Matsukawa et al. [21] (2015) | Analysis of finite element model | 4 | 30 Lumbar vertebral bodies (L4) | Comparing CBT, PS screw fixation strength: measurement of axial pullout, multidirectional loading. And then simulating flexion, extension, lateral bending, axial rotation of screw-vertebra construct | CBT screw fixation: stronger in pullout strength, stiffness in cephalocaudal and mediolateral loading; superior resistance to flexion and extension loading, inferior resistance to lateral bending and axial rotation in screw-vertebra construct PS screw fixation construct: superior to lateral bending and axial rotation |
CBT, cortical bone trajectory; PS, pedicle screw; ROM, range of motion.
a)
No significant difference.