Finite element analysis of the pelvis after modular hemipelvic endoprosthesis reconstruction

Abstract

Purpose: The aim of this study was to investigate the biomechanics of the pelvis reconstructed with a modular hemipelvic prosthesis using finite element (FE) analysis.

Methods: A three-dimensional FE model of the postoperative pelvis was developed and input into the Abaqus FEA software version 6.7.1. Mesh refinement tests were then performed and a force of 500 N was applied at the lamina terminalis of the fifth lumbar vertebra along the longitudinal axis of the normal pelvis and the postoperative pelvis for three positions: sitting, standing on two feet, and standing on the foot of the affected side. Stress distribution analysis was performed between the normal pelvis and postoperative pelvis at these three static positions.

Results: In the normal pelvis, stress distribution was concentrated on the superior area of the acetabulum, arcuate line, sacroiliac joint, sacral midline and, in particular, the superior area of the greater sciatic notch. In the affected postoperative hemipelvis, stress distribution was concentrated on the proximal area of the pubic plate, the top of the acetabular cup, the connection between the CS-fixator and acetabular cup and the fixation between the prosthesis and sacroiliac joint.

Conclusions: Stress distribution of the postoperative pelvis was similar to the normal pelvis at three different static positions. Reconstruction with a modular hemipelvic prosthesis yielded good biomechanical characteristics.

Fig. 1

a MRI scan shows the tumour before surgery. b Radiographic image of the pelvis 12 months after surgery. A CS-fixator; B acetabular cup; C pubic plate

Fig. 2

The three-dimensional reconstruction model of the pelvis before surgery (a) and after surgery (b)

Fig. 3

a Acetabular cup. b CS-fixator. c Assembly of the acetabular cup and CS-fixator. d Pubic plate

Fig. 4

Stress distribution of the normal pelvis during two-legged stance position (a), single-legged stance position (b), and sitting (c)

Fig. 5

Stress distribution of the postoperative pelvis during two-legged stance position (a), one-legged stance position on the affected leg (b) and sitting (c)

Fig. 6

The stress distribution of the implant components during two-legged stance (a), one-legged stance on the affected leg (b), and sitting (c). The red arrows indicate the proximal pubic plate bears high stresses