Assessment of net knee moment-angle characteristics by instrumented hand-held dynamometry in children with spastic cerebral palsy and typically developing children

Abstract

BackgroundThe limited range of motion during walking in children with spastic cerebral palsy (SCP) may be the result of altered mechanical characteristics of muscles and connective tissues around the knee joint. Measurement of static net knee moment-angle relation will provide insights into these alterations, for which instrumented hand-held dynamometry may be applied.The aims of this study were: (1) to test the measurement error of the estimated net knee moment-angle characteristics, (2) to determine the correlation between knee extension angle measurement at a standardized knee moment and popliteal angle from common physical examination and (3) to compare net knee moment–angle characteristics in SCP versus typically developing children.MethodsWith the child lying in sideward position, the knee was extended by moving the lower leg by a hand-held force transducer on a low friction cart. Force data were collected for a range of knee angles. Data were excluded when activity (EMG) levels of knee extensor and flexor muscles exceeded the EMG level during rest by more than two standard deviations. The net knee flexion moments were calculated from recorded force data and measured moment arm. Reliability for knee angles corresponding with 0.5, 1, 2, 3, and 4 Nm knee net flexion moments was assessed by standard error of measurements (SEM) and smallest detectable difference (SDD).ResultsFor between day comparison, SEMs were about 5° and SDDs were below 14° for knee angles at 1-4 Nm net knee flexion moments. In SCP children, the knee angle measured at 4 Nm knee flexion moment was not related to the popliteal angle (r = 0.52). The slope at 4 Nm of the knee moment-angle curve in SCP children was significantly higher than that in typically developing children.ConclusionsThe presented knee hand-held dynamometry allows assessment of net knee flexion moment-knee angle characteristics in typically developing and SCP children and can be used to identify clinically relevant changes as a result of treatment. Overall stiffness of structures that contribute to the net knee flexion moment at the knee (i.e. muscles, tendons, ligaments) is elevated in SCP children.Electronic supplementary materialThe online version of this article (doi:10.1186/s12984-015-0056-y) contains supplementary material, which is available to authorized users.

Knee Moment-Angle Characteristics and Semitendinosus Muscle Morphology in Children with Spastic Paresis Selected for Medial Hamstring Lengthening

“…The experimental protocol and setup have been described in detail previously [31]. Subjects were positioned on an examination bed on their left side, with the hip of the measured (right) leg at 70° flexion (Fig 1).…”

“…The analyses and reliability have been described in detail previously, reporting an standard error of the mean for these measurements of about 5° [31]. In brief, joint angle and force data were low-pass filtered at 1 Hz.…”

“…The included data points from the three repetitions were fitted by a third order polynomial function. This equation was retrieved based on a stepwise regression analysis in a previous study [31]: …”

“…We have recently described a freehand three-dimensional ultrasound method (3D US) to assess morphological variables of ST (e.g. muscle belly length, tendon length, fascicle length and whole muscle volume, and volumes and fascicle length of both compartments) [30] and a method to reliably measure knee moment-angle characteristics in children with SP [31], which provides quantitative measures of knee ROM and stiffness.…”

Muscle and tendon lengthening behaviour of the medial gastrocnemius during ankle joint rotation in children with cerebral palsy

“…The leg tested was the most affected, defined by clinical spasticity scores(Bohannon & Smith, 1987;Tardieu, Shentoub, & Delarue, 1954), and the left in TD children. When, during joint rotation, the RMS-EMG signal exceeded 10% of the maximal voluntary contraction value (collected before the stretch trials), the corresponding trial was discarded(Haberfehlner et al, 2015). The reliability of data measured using the same equipment has been reported previously(Schless et al, 2015).…”