Pelvic reconstruction is required to restore the functional activity after an internal hemipelvectomy.   
The available pelvic prosthesis has several complications and long terms issues (such as stability, dislocations etc.) due to non inclusion of the basic mechanics.   
In this study, a structural optimization based pelvic design is presented for an efficient pelvic prosthesis by including the effect of muscles under single leg stance.   
The single leg stance loading condition is divided into four categories, (a) when all muscles of the pelvic bone are active, (b) when lower muscles of the pelvic bone are active, (c) when upper muscles of the pelvic bone are active and (d) average value of the muscle forces during the entire stance phase.   
The muscle force data is obtained from the literature and the OpenSim software.   
Thereafter, compliance minimization with volume constraint formulation in topology optimization is used to generate four prosthesis for pelvic reconstruction.   
This formulation gives the best possible stiffest possible structure with the given volume.  
Titanium alloy (Ti_6Al_4V) is used to design the pelvic prosthesis due to its biocompatibility and high strength.   
The obtained optimal designs are compared with the natural pelvic bone by measuring the shape similarity index using Procrustes Analysis.   
The optimal design obtained from the upper muscles and the average values of the muscles are able to create a hole in the lower portion of the pelvic bone which is similar to the obturator foramen.  
The moderate to good shape similarity values indicate less complication such as dislocations, stability and constraining the range of hip joint.   
Results show that the maximum value of the stress and displacement produced by the optimal designs are less than the natural pelvic bone.   
The maximum stress region (at sacro-iliac joint and pubic symphysis) and maximum displacement region (at iliac-crest, which the upper most part of the pelvic bone) remain same for all the optimal designs.  
The induced peak stresses in the optimal designs are low, within linear elastic zone and below the yield strength of the alloy.   
The compliance values of the optimal designs are lower than natural pelvic bone due to the use of different material for the prosthesis.   
The four optimal designs are compared by measuring the compliance of each design under four different loading configurations.  
From these results, the optimal design obtained from the average value of the muscles show better compliance values than the other optimal designs, so we recommend this design for the pelvic prosthesis. 


Topology Optimization of the Pelvic Bone Prosthesis Under Single Leg Stance

Division / Sponsors: 
Design Engineering Division and Computers & Information In Engineering Division


Paper Proceedings: https://asmedigitalcollection.asme.org/IDETC-CIE/IDETC-CIE2020/volume/83907

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