A physically based trunk soft tissue modeling for scoliosis surgery planning systems

Abstract

One of the major concerns of scoliotic patients undergoing spinal correction surgery is the trunk's external appearance after the surgery. This paper presents a novel incremental approach for simulating postoperative trunk shape in scoliosis surgery. Preoperative and postoperative trunk shapes data were obtained using three-dimensional medical imaging techniques for seven patients with adolescent idiopathic scoliosis. Results of qualitative and quantitative evaluations, based on the comparison of the simulated and actual postoperative trunk surfaces, showed an adequate accuracy of the method. Our approach provides a candidate simulation tool to be used in a clinical environment for the surgery planning process. IntroductionAdolescent idiopathic scoliosis (AIS) is a complex three-dimensional deformation of the trunk. In severe cases, a spine surgery treatment is required. Most of the surgical procedures use specialized instrumentation attached to the spine to correct the deformities (Fig. 4.1). One 22of the concerns of the patient (and, in fact, a major factor of satisfaction) is the trunk's appearance after the surgery. In addition to the surgeon's priorities in the surgery planning process, a tool for simulating the trunk's postoperative appearance is of importance to take into account the patient's concerns in the treatment planning.Aubin et al. [4] have developed a spinal surgery simulation system in the context of the optimal planning of surgical procedures to correct scoliotic deformities. The overall goal of this biomechanical engineering research project is to develop a user-oriented simulator for virtual prototyping of spinal deformities surgeries: a fully operational, safe and reliable patient-specific tool that will permit advanced planning of surgery with predictable outcomes, and rationalized design of surgical instrumentation [3,4]. It addresses the problems faced by orthopedic surgeons treating spinal deformities when making surgical planning decisions. The developed system is, however, only concerned with the configuration of the spine, and does not furnish any estimate of the effects of the surgical treatment on the external appearance of the trunk. A desirable complement to this spine simulator would be to develop a full trunk model that would allow the propagation of the surgical correction on the spine toward the external trunk surface through the soft tissue deformation.Physics-based models of deformable objects have been studied since the early 80's and are common in animation where physical laws are applied to an object to simulate realistic movements. Deformable physics-based models are also used in biomedical applications, in particular for surgery simulation [30]. These applications require visual and physical realism, but the real biomechanical properties involved are not always well known. The two most popular approaches to physically modeling soft tissues are the Finite Element Method (FEM) and Mass-Spring Model (MSM). Commonly used in engineering to accurately analyze struct...

Combining 3D Structured Light Imaging and Spine X-ray Data Improves Visualization of the Spinous Lines in the Scoliotic Spine

“…Ng and Bettany-Saltikov reviewed diagnostic methods and emphasized that scoliosis measurements should not focus only on Cobb angles best calculations because several methods may deliver equally accurate parameters [19]. The analysis of the human torso's shape was also applied before and after scoliosis surgery [25,27,72]. The approach presented in this study utilizes the combined data from 3D ST optical scans and X-rays.…”

“…The EOS system has recently become a recommended diagnostic system due to the microdose of radiation [10,12,15,22,23]. Possible imperfections may occur [26] when an examined patient cannot stand or sit steadily during image acquisition [27]. Only an EOS imager may significantly lower radiation exposure.…”