Fig 1.
PRISMA ScR flow diagram: Scope review process for neuromusculoskeletal models of spasticity.
Fig 2.
Distribution of studies according to the countries, experimental data collected, target joints, and sample characteristics.
Fig 3.
Block diagram of components represented in neuromusculoskeletal models of spasticity.
Solid lines indicate components represented by all models, dotted lines denote elements represented by some studies, and long dashed lines indicate representation in a single study. At the top, supraspinal structures are represented in a simplified form, usually as a neural drive. Ascending tracts were not represented in the reviewed models. The spinal cord is represented by the pool of α motoneurons (MN) and γ motoneurons (MN) from the target muscle/group and its antagonist and interneurons from groups Ia, II, and Ib. Proprioceptive feedback is provided by primary (Ia), secondary (II) afferents from muscle spindles, and Ib from the Golgi tendon organ (GTO). Most neuromusculoskeletal models represent only the muscle-tendon unit (MTU) of the target muscle/group, i.e., where the spasticity is manifested. A few models also include the MTU of antagonistic muscles. The MTUs are typically represented by a Hill-type model, which consists of the contractile element (CE), or extrafusal fibers (EF), representing the contractile properties of the muscle fibers, parallel passive elements with viscoelastic properties, and intrafusal fibers (IF). These elements are arranged in series with the tendon, forming the pennation angle, which refers to the angle between the muscle fibers and the tendon.
Table 1.
Physiological components represented in the studies.
Table 2.
Characteristics of neuromusculoskeletal models and parameters associated with spasticity and other contributors of joint hyper-resistance.
Fig 4.
Mapping of the modeled muscles.
The presence of a rectangle in a muscle row indicates that it was a target muscle in the model(s) developed by the authors in the corresponding column. Rectangles of the same color indicated that muscles were represented in a lumped way.
Table 3.
Motor tasks, etiology of spasticity, and characteristics of experimental groups (when present).
Table 4.
Physiological plausibility score for the developed models according to the investigated tasks.