Biomechanical study on the stability and Finite-element analysis of stress distribution in reconstructed pelvis with autograft after hindquarter amputation

Background: Treatment of malignant tumors of the pelvis, especially in the periacetabular region continues to present one of the most challenging problems in oncological and orthopedic surgery. Even now, hindquarter amputation is still the only choice for some patients, but hindquarter amputation can cause much trouble in sitting, standing and in fitting the exoprosthesis of patients after amputation, and their quality of life and function were always poor. Method: The weight bearing function of pelvis with autograft was restored after hindquarter amputation on 10 cadaveric pelves along with the lumbar and bilateral lower limbs, analyzed the stability of reconstructed pelvis under the axial loading in gradient from 0-500N. The finite element model of the intact pelvis was constructed based on computed tomography (CT) images of the pelvis of a healthy 30-year-old man and investigate its stress distribution under physiological loading. Results: Biomechanical experiment showed that the intact pelvis was the most stable condition compared to the reconstructed models according to the capability of pelvis resisting compression in axial direction, but the intact pelvis and reconstructed models were restored anterior state after removed loading. There had no statistical difference in displacements of pelvis reconstructed by femur or tibia (1>0.05). The FEM analyses showed as following: the stress distribution in normal pelvis was symmetric and the concentration of stress located along ischio sacral arch. The maximum stress of the reconstructed pelvis was higher compared with that of intact pelvis. The stress distribution in two reconstructed pelves was similar. The maximum stress concentrated on the shaft of reconstructive tibia, which was less than that of reconstructive femur, in that the stress distribution was near screw. Conclusion: The stability of reconstructed pelvis is weaker than that of intact pelvis, but the stability of reconstructed pelvis is effective and it could bear human weight at earlier time. The maximum stress of the reconstructed pelvis is higher than that of intact pelvis and the reconstruction by femur is benefit for preventing bone fracture.