Objective measurement of sitting - Application in children with cerebral palsy.

Background: Children with cerebral palsy (CP) and a severe motor impairment, have limited ability to perform volitional movements due to spasticity, involuntary postures and movements and reduced ability to maintain antigravity head and trunk control. A stable sitting position is a prerequisite for participation in daily life, but there is a lack of objective measurement methods for this population.

Research Question: Is it feasible to measure a stable sitting position with pressure mapping and 2D motion analysis, and can it detect differences to a) a reference group, b) between subgroups of CP and c) before and after treatment with intrathecal baclofen (ITB)?

Methods: Pressure mapping, and a 2D motion analysis system, were used to capture movements of centre of pressure (CoP), and movements of head, hand and leg, sitting on a bench for 90 s. Twenty-two children with dyskinetic or bilateral spastic CP, GMFCS III-V, mean age 9.0, and 30 children with typical development (TD) mean age 10.7, were recruited between 2010 and 2019. Seventeen children were treated with ITB. Parents were interviewed regarding aspect of sitting. Non-parametric methods were used for statistical analysis.

Results: Differences in CoP and kinematics were detected with more movements in children with CP compared to children with TD (p < 0.001). There were more movements in children with dyskinetic CP compared to children with bilateral spastic CP as captured with the pressure mapping system (CoP distance p = .005 and Anterio-Posterior sway p = .014). After treatment with ITB, involuntary movements had decreased (CoP p = 0.006-0.035, kinematics p = 0.002-0.020). Parents reported improvement in sitting. The two measurement systems showed consistent results (rho 0.500-0.771, p = <0.001-0.049).

Significance: It was feasible to objectively measure sitting position in children with a moderate-to-severe motor impairment with differences to a reference group and after an intervention. CoP and head movements were the variables that were easiest to capture.