Objective: To compare the stress distribution of normal pelvis with those of postoperative contralateral pelvic and modular hemipelvic prosthesis under different positions, with an aim to providing biomechanical evidence support for safe reconstruction of pelvic ring using modular hemipelvic prosthesis.
Methods: Three-dimensional finite element models of normal pelvis, postoperative pelvic and modular hemipelvic prosthesis were established using thin-layer CT scanning (TLCS). The stress distributions of normal pelvis, postoperative pelvic and prosthesis were measured under three static positions: standing on two feet, standing on one foot on the defective side and sitting.
Results: Little difference was found in contralateral pelvic stress between the normal pelvic and reconstructive pelvic models given the same load with different positions. The maximum stress level appeared at the upside of sacrum mesion, sacroiliac joints, superior greater sciatic notch and iscbial tuberosity, albeit a much lower level than fatigue strength. The maximum stress level of modular hemipelvic prosthesis appeared at the inner wall of connector bar between CS fixation and acetabular cup. Similarly, the stress level was also much lower than the fatigue strength of connector bar. The stress distribution of postoperative pelvic was similar to that of normal pelvic.
Conclusion: Reconstruction with modular hemipelvic prosthesis has little effect on contralateral pelvic. The maximum stress levels of contralateral pelvis and modular hemipelvic prosthesis are significantly lower than their fatigue strength, which indicates sound safety of contralateral pelvis and modular hemipelvic prosthesis. Pelvic reconstruction with modular hemipelvic prosthesis produces good biomechanical compatibility.