Leg and Joint Stiffness in Children with Spastic Diplegic Cerebral Palsy during Level Walking

Abstract

Individual joint deviations are often identified in the analysis of cerebral palsy (CP) gait. However, knowledge is limited as to how these deviations affect the control of the locomotor system as a whole when striving to meet the demands of walking. The current study aimed to bridge the gap by describing the control of the locomotor system in children with diplegic CP in terms of their leg stiffness, both skeletal and muscular components, and associated joint stiffness during gait. Twelve children with spastic diplegia CP and 12 healthy controls walked at a self-selected pace in a gait laboratory while their kinematic and forceplate data were measured and analyzed during loading response, mid-stance, terminal stance and pre-swing. For calculating the leg stiffness, each of the lower limbs was modeled as a non-linear spring, connecting the hip joint center and the corresponding center of pressure, with varying stiffness that was calculated as the slope (gradient) of the axial force vs. the deformation curve. The leg stiffness was further decomposed into skeletal and muscular components considering the alignment of the lower limb. The ankle, knee and hip of the limb were modeled as revolute joints with torsional springs whose stiffness was calculated as the slope of the moment vs. the angle curve of the joint. Independent t-tests were performed for between-group comparisons of all the variables. The CP group significantly decreased the leg stiffness but increased the joint stiffness during stance phase, except during terminal stance where the leg stiffness was increased. They appeared to rely more on muscular contributions to achieve the required leg stiffness, increasing the muscular demands in maintaining the body posture against collapse. Leg stiffness plays a critical role in modulating the kinematics and kinetics of the locomotor system during gait in the diplegic CP.

Alleviation of Motor Impairments in Patients with Cerebral Palsy: Acute Effects of Whole-body Vibration on Stretch Reflex Response, Voluntary Muscle Activation and Mobility

“…In spasticity, reciprocal inhibition is pathologically affected ( 64 , 69 – 71 ). This can be reflected in pathological co-contractions of antagonistic muscles leading to augmented joint stiffness ( 20 , 22 ) as well as muscle weakness leading to deficient movement patterns in children with CP ( 17 , 72 ). In the current study, however, neuromuscular control during voluntary movement execution emphasizes improved neuromuscular coordination following WBV: the results clearly demonstrate an enhanced muscular activation of lower limb muscles (values up to +37%) as well as improved coordination between agonists and antagonists during maximal excursion of the ankle and knee joint (ratios up to +117%).…”

“…Those include hyperexcitability of short-latency ( 14 , 15 ), but reduced long-latency reflexes ( 16 ). Coexisting with spasticity, also muscle weakness ( 17 , 18 ) as well as diminished selective and voluntary supraspinal motor control ( 19 ) are expressed in developmental disorders of functional movement: patients suffer from gross motor problems ( 12 ), such as impaired mobility ( 20 ) and postural control ( 19 , 21 ), as well as disturbances in gait ( 22 – 24 ). On a neuromuscular basis, reduced electromyographic activity ( 22 ), a strong co-activation of antagonistic muscles during movement ( 15 , 22 , 23 , 25 ), diminished reciprocal inhibition ( 17 , 26 ), and changes in perception ( 12 ) have been associated with those functional impairments and should be considered regarding therapy of movement disorders.…”

Biomechanical control-based locomotor function rehabilitation technology for children with cerebral palsy

“…It is necessary to extend the integrated approach to the physiological aspects. The theory of functional systems represents a promising way towards it (Wang, & Huang, 2016).…”

Toward modeling locomotion using electromyography‐informed 3D models: application to cerebral palsy

“…Current modeling pipelines characterize either the neural or the mechanical determinants of CP locomotion. This poses a major challenge to the treatment of motor impairment in CP, where disrupted mechanical function (i.e., abnormal joint loading and stiffness) must be understood in the context of its disrupted neural origin (i.e., abnormal neuromuscular function) .…”

“…However, with this paper, we provide applicative examples in the context of CP and subsequent personalization of neurorehabilitation interventions . The past decade has seen critical advancement in the development of modeling formulations that characterize CP individuals’ musculoskeletal morphologies and function, a central element driving this position paper focus toward CP …”