Toward the development of virtual surgical tools to aid orthopaedic FE analyses

Abstract

Computational models of joint anatomy and function provide a means for biomechanists, physicians, and physical therapists to understand the effects of repetitive motion, acute injury, and degenerative diseases. Finite element models, for example, may be used to predict the outcome of a surgical intervention or to improve the design of prosthetic implants. Countless models have been developed over the years to address a myriad of orthopaedic procedures. Unfortunately, few studies have incorporated patient-specific models. Historically, baseline anatomic models have been used due to the demands associated with model development. Moreover, surgical simulations impose additional modeling challenges. Current meshing practices do not readily accommodate the inclusion of implants. Our goal is to develop a suite of tools (virtual instruments and guides) which enable surgical procedures to be readily simulated and to facilitate the development of all-hexahedral finite element mesh definitions.

Figure 1

The capitate bone – the original triangulated surface represented as (a) a shaded and (b) wireframe surface. (c) Each triangle of the original mesh was subdivided 4 times and (d) the mesh was decimated to reduce the overall number of triangles.

Figure 2

Box clip widget used to generate two bony segments.

Figure 3

Boolean operations performed on (a) two spherical surfaces: (b) subtract, (c) intersection, and (d) union.

Figure 4

Introducing a cylindrical drill hole through the bone.

Figure 5

Multiblock mesh generated about a through hole. The magnified view of the hole illustrates a subtle loss of mesh fidelity due to smoothing immediately adjacent to the hole.

Figure 6

Laminoplasty procedure performed on vertebra C5. (a) intact C5 surface, (b) bicortical defect, (c) contralateral hinge defect introduced, (d) spinous process resected, (e) drill holes introduced, (f) FE mesh, (g) hinge opened and the calculated stresses are input as initial conditions for the (h) plated model.