Abstract:

Objective To explore the biomechanical stability and advantages of cortical bone trajectory (CBT) screws in the treatment of lumbar spine tuberculosis and provide biomechanical evidence for the choice of clinical fixation methods. Methods Sixteen pig spine specimens (T₁₂-L₅) were selected to simulate the in vitro (L₂-L₃) lumbar spine tuberculosis bone destruction. The 16 specimens were randomly divided into 4 groups (short-segment (vertebra pedicle screw) fixation (group A), short-segment (spine CBT screw) fixation (group B), intervertebral pedicle screw fixation (group C), vertebrae fixation with CBT screw (group D)), 4 specimens in each group, each specimen in each group was subjected to biomechanical testing in the state of complete specimen (state 1) and L₂-L₃ spinal tuberculosis model bone graft fusion and internal fixation (state 2). We loaded each specimen on the spine 3D exercise machine, applied moments of 2 N·m, 2.5 N·m, 1 N·m, 3 N·m, respectively, then recorded the range of movement (ROM) of the specimens in the four directions of flexion, extension, lateral bending and torsion, compared and analyzed each group of ROM. Results The ROMs of flexion, extension, lateral bending, and torsion in group A in state 1 and state 2 modes were (8.47±1.76)°, (7.01±1.10)°, (5.03±0.92)°, (4.48±0.41)° and (4.78±0.07)°, (2.91±0.16)°, (2.66±0.09)°, (2.23±0.05)°; the ROMs of flexion, extension, lateral bending and torsion in group B in state 1 and state 2 modes were (7.32±0.75)°, (5.35±0.69)°, (3.44±0.51)°, (3.36±1.02)° and (3.51±0.29)°, (1.74±0.04)°, (1.53±0.31)°, (1.23±0.08)°; the ROMs of flexion, extension, lateral bending, and torsion in group C in state 1 and state 2 modes were (10.01±0.39)°, (9.05±0.25)°, (7.42±1.06)°, (6.92±1.15)° and (7.21±0.17)°, (5.07±0.02)°, (5.12±0.74)°, (4.58±0.01)°; the ROMs of flexion, extension, lateral bending, and torsion in group D in state 1 and state 2 modes were (9.20±1.37)°, (7.38±0.88)°, (6.89±1.22)°, (6.00±0.52)° and (6.06±0.16)°, (3.99±0.02)°, (3.85±0.08)°, (3.47±0.10)°. The ROM value of each fixed mode group under the state of bone graft fusion and internal fixation (state 2) was lower than that of the intact state (state 1), and the difference was statistically significant (group A: t values were 4.531, 5.346, 6.008, 4.149, P values were 0.020, 0.013, 0.009, 0.025; group B: t values were 9.481, 16.181, 11.814, 4.769, P values were 0.002, 0.001, 0.001, 0.018; group C: t values were 4.349, 8.002, 4.473, 4.800, P values were 0.022, 0.004, 0.021, 0.017; group D: t values were 5.041, 4.146, 12.232, 10.583, P values were 0.015, 0.025, 0.001, 0.002). Conclusion The state 2 of the 4 groups of fixation modes all have stronger mechanical support than state 1. CBT screw intervertebral fixation can not only provide sufficient mechanical stability, but also provide stronger stability when using the same fixed segment, thus could minimize number of segments for fixation.

Key words: Tuberculosis,spine, Internal fixator, Spinal fusion, Disease model,animal, Comparative study