Biomechanical comparison of Ortho-Bridge system and plate fixation system for femoral periprosthetic type Vancouver B1 fracture / 中华骨科杂志

ABSTRACT

Objective:To compare the biomechanical parameters of Ortho-Bridge system (OBS) and locking compression plate+locking attachment plate (LCP+LAP) in the fixation of femoral periprosthetic type B1 fracture.Methods:The same periprosthetic type B1 fracture of human femur were made, including simple fracture model and comminuted fracture model, 12 in each. And the simple fracture models were randomly divided into 6 pieces of OBS system fixation group and 6 pieces of LCP+LAP system fixation group, and the complex fracture models were also randomly divided into 6 pieces of OBS system fixation group and 6 pieces of LCP + LAP system fixation group. Then the four groups of models were tested by axial compression and torsion tests, and the stiffness of the models under axial compression and torsion angle of the models under torsion test were collected. The axial compression failure test was carried out to collect the vertical load of the ultimate failure test. The axial stiffness, torsion angle and axial failure load of OBS and LCP+LAP fixed simple and comminuted fractures were statistically analyzed by t test. Results:For the test of fixed simple fracture, there was no significant difference ( t=0.535, P=0.522) in the axial stiffness between the OBS group (868.87±157.14 N) and the LCP+LAP group (904.53±44.76 N), whereas the results of torsion test showed that the LCP+LAP group had a higher torsion angle 7.17°±0.52° than the OBS group 5.45°±0.44° ( t=5.616, P<0.001); When fixing comminuted fractures, the OBS group had a higher axial stiffness (145.33±10.34 N) than the LCP+LAP group (84.15±8.94 N) ( t=10.961, P<0.001), but the LCP+LAP group had a higher torsion angle 7.75°±1.17° than the OBS group 5.23°±0.31° ( t=4.652, P=0.001). Ultimate failure test data showed that the failure pressure of OBS fixed group (4 967.49±132.88 N) was higher than LCP+LAP group (3 967.41±145.16 N) ( t=12.447, P<0.001). In the LCP+LAP group, there was destruction of the contact cortex at the fracture site, while in the OBS group, there was destruction of the contact cortex at the fracture site as well as fractures around the proximal fixation screw. Conclusion:OBS group has similar axial compression resistance to LCP+LAP group, but better torsion resistance than LCP+LAP group when it is used to fix B1 simple fracture around femoral prosthesis. When comminuted fracture is fixed, the axial compression resistance and torsion resistance of OBS group are better than LCP+LAP group. The stress is dispersed during OBS fixation, which can better avoid the failure of internal fixation during early functional exercise.