Personalized Lumbar Vertebrae Modeling for Dynamic Assessment of Idiopathic Scoliosis.

Abstract

Clinical assessment of idiopathic scoliosis (IS) patients primarily relies on static imaging techniques. Dynamic digital human (DDH) can provide comprehensive spatio-temporal information for dynamic assessment of the deformed spine in IS patients comparing with static imaging techniques, such as X-ray for general assessment and computed tomography (CT) for surgical planning. The lumbar vertebrae exhibit greater morphological variability than the thoracic region when subjected to different postures and mechanical loads, making them particularly important for dynamic assessment. Therefore, a personalized lumbar vertebrae model (PLVM) is proposed in this work to simulate lumbar vertebrae motion for IS patients; furthermore, an individualized DDH (i-DDH) is proposed by embedding PLVM into DDH to capture the spatio-temporal information. First, we use a bone primitive generation method to construct the DDH by incorporating Neural Radiance Fields (NeRF) and three-dimensional (3D) Gaussian splatting methods. Next, we develop the PLVM generation method to simulate lumbar vertebrae motion under different loads and postures. Finally, the bone primitives and PLVM are merged to generate the i-DDH for dynamic assessment. We validated i-DDH using multi-posture radiographs from eight IS patients awaiting surgery. The results demonstrate high accuracy compared to state-of-the-art (SOTA) models, with a mean angular error of $0.96^\circ$ and a maximum error of $3.6^\circ$ relative to radiographs. The proposed i-DDH framework is able to capture the spinal posture and conduct the dynamic assessment of IS patients rather than fixed positions. It overcomes the soft tissue artifact (STA) problem from motion capture systems and the failure to generate 3D spinal deformity of IS patients by training healthy subjects from computer vision methods. It also shows great clinical significance for preoperative planning and clinical assessment by providing dynamic spinal posture that cannot be achieved with static imaging.