*Review* **Multibody Models of the Thoracolumbar Spine: A Review on Applications, Limitations, and Challenges**

**Tanja Lerchl 1,2,\* , Kati Nispel 1,2 , Thomas Baum <sup>2</sup> , Jannis Bodden 2 , Veit Senner <sup>1</sup> and Jan S. Kirschke 2**


**Abstract:** Numerical models of the musculoskeletal system as investigative tools are an integral part of biomechanical and clinical research. While finite element modeling is primarily suitable for the examination of deformation states and internal stresses in flexible bodies, multibody modeling is based on the assumption of rigid bodies, that are connected via joints and flexible elements. This simplification allows the consideration of biomechanical systems from a holistic perspective and thus takes into account multiple influencing factors of mechanical loads. Being the source of major health issues worldwide, the human spine is subject to a variety of studies using these models to investigate and understand healthy and pathological biomechanics of the upper body. In this review, we summarize the current state-of-the-art literature on multibody models of the thoracolumbar spine and identify limitations and challenges related to current modeling approaches.

**Keywords:** musculoskeletal multibody dynamics; spinal biomechanics; spinal alignment; spinal loading; muscle force computation; thoracolumbar spine; biomechanical model
