title: Knee Moment-Angle Characteristics and Semitendinosus Muscle Morphology in Children with Spastic Paresis Selected for Medial Hamstring Lengthening.
abstract: To increase knee range of motion and improve gait in children with spastic paresis (SP), the semitendinosus muscle (ST) amongst other hamstring muscles is frequently lengthened by surgery, but with variable success. Little is known about how the pre-surgical mechanical and morphological characteristics of ST muscle differ between children with SP and typically developing children (TD). The aims of this study were to assess (1) how knee moment-angle characteristics and ST morphology in children with SP selected for medial hamstring lengthening differ from TD children, as well as (2) how knee moment-angle characteristics and ST morphology are related. In nine SP and nine TD children, passive knee moment-angle characteristics and morphology of ST (i.e. fascicle length, muscle belly length, tendon length, physiological cross-sectional area, and volume) were assessed by hand-held dynamometry and freehand 3D ultrasound, respectively. At net knee flexion moments above 0.5 Nm, more flexed knee angles were found for SP compared to TD children. The measured knee angle range between 0 and 4 Nm was 30% smaller in children with SP. Muscle volume, physiological cross-sectional area, and fascicle length normalized to femur length were smaller in SP compared to TD children (62%, 48%, and 18%, respectively). Sixty percent of the variation in knee angles at 4 Nm net knee moment was explained by ST fascicle length. Altered knee moment-angle characteristics indicate an increased ST stiffness in SP children. Morphological observations indicate that in SP children planned for medial hamstring lengthening, the longitudinal and cross-sectional growth of ST muscle fibers is reduced. The reduced fascicle length can partly explain the increased ST stiffness and, hence, a more flexed knee joint in these SP children.
authors.affiliation: Laboratory for Myology, Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands.|Department of Rehabilitation Medicine, VU University Medical Center, Amsterdam, The Netherlands.|MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Helga
authors.initials: H
authors.lastname: Haberfehlner
authors.affiliation: Laboratory for Myology, Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands.|MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Richard T
authors.initials: RT
authors.lastname: Jaspers
authors.affiliation: Pediatric Orthopaedic Department, University Children's Hospital Basle (UKBB), Basle, Switzerland.|Laboratory for Movement Analysis, University Children's Hospital Basle (UKBB), Basle, Switzerland.
authors.forename: Erich
authors.initials: E
authors.lastname: Rutz
authors.affiliation: Department of Rehabilitation Medicine, VU University Medical Center, Amsterdam, The Netherlands.|MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Jules G
authors.initials: JG
authors.lastname: Becher
authors.affiliation: Department of Rehabilitation Medicine, VU University Medical Center, Amsterdam, The Netherlands.|MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Jaap
authors.initials: J
authors.lastname: Harlaar
authors.affiliation: MOVE Research Institute Amsterdam, The Netherlands.|Department of Orthopaedic Surgery, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Johannes A
authors.initials: JA
authors.lastname: van der Sluijs
authors.affiliation: MOVE Research Institute Amsterdam, The Netherlands.|Department of Orthopaedic Surgery, VU University Medical Center, Amsterdam, The Netherlands.
authors.forename: Melinda M
authors.initials: MM
authors.lastname: Witbreuk
authors.affiliation: Laboratory for Movement Analysis, University Children's Hospital Basle (UKBB), Basle, Switzerland.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Romkes
authors.affiliation: Laboratory for Movement Analysis, University Children's Hospital Basle (UKBB), Basle, Switzerland.
authors.forename: Marie
authors.initials: M
authors.lastname: Freslier
authors.affiliation: Pediatric Orthopaedic Department, University Children's Hospital Basle (UKBB), Basle, Switzerland.|Laboratory for Movement Analysis, University Children's Hospital Basle (UKBB), Basle, Switzerland.
authors.forename: Reinald
authors.initials: R
authors.lastname: Brunner
authors.affiliation: Laboratory for Myology, Department of Human Movement Sciences, Faculty of Behavioural and Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands.|MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Huub
authors.initials: H
authors.lastname: Maas
authors.affiliation: Department of Rehabilitation Medicine, VU University Medical Center, Amsterdam, The Netherlands.|MOVE Research Institute Amsterdam, The Netherlands.
authors.forename: Annemieke I
authors.initials: AI
authors.lastname: Buizer
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002648:Child; D004576:Electromyography; D005260:Female; D000070633:Hamstring Muscles / Q000473:pathology* / Q000503:physiopathology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint; D008297:Male; D009128:Muscle Spasticity / Q000175:diagnosis / Q000473:pathology* / Q000503:physiopathology*; D010291:Paresis / Q000175:diagnosis / Q000473:pathology* / Q000503:physiopathology*; D016059:Range of Motion, Articular; D014463:Ultrasonography