title: The mechanics of activated semitendinosus are not representative of the pathological knee joint condition of children with cerebral palsy.
abstract: Characteristic cerebral palsy effects in the knee include a restricted joint range of motion and forcefully kept joint in a flexed position. To show whether the mechanics of activated spastic semitendinosus muscle are contributing to these effects, we tested the hypothesis that the muscle's joint range of force exertion is narrow and force production capacity in flexed positions is high. The isometric semitendinosus forces of children with cerebral palsy (n=7, mean (SD)=7years (8months), GMFCS levels III-IV, 12 limbs tested) were measured intra-operatively as a function of knee angle, from flexion (120°) to full extension (0°). Peak force measured in the most flexed position was considered as the benchmark. However, peak force (mean (SD)=112.4N (54.3N)) was measured either at intermediate or even full knee extension (three limbs) indicating no narrow joint range of force exertion. Lack of high force production capacity in flexed knee positions (e.g., at 120° negligible or below 22% of the peak force) was shown except for one limb. Therefore, our hypothesis was rejected for a vast majority of the limbs. These findings and those reported for spastic gracilis agree, indicating that the patients' pathological joint condition must rely on a more complex mechanism than the mechanics of individual spastic muscles.
authors.affiliation: Biomedical Engineering Institute, Boğaziçi University, Istanbul, Turkey.
authors.forename: Filiz
authors.initials: F
authors.lastname: Ateş
authors.affiliation: Istanbul University, Istanbul School of Medicine, Department of Orthopaedics and Traumatology, Istanbul, Turkey.
authors.forename: Yener
authors.initials: Y
authors.lastname: Temelli
authors.affiliation: Biomedical Engineering Institute, Boğaziçi University, Istanbul, Turkey. Electronic address: can.yucesoy@boun.edu.tr.
authors.forename: Can A
authors.initials: CA
authors.lastname: Yucesoy
mesh_terms: D001696:Biomechanical Phenomena; D002547:Cerebral Palsy / Q000503:physiopathology*; D002648:Child; D005260:Female; D000070633:Hamstring Muscles / Q000503:physiopathology*; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction; D016059:Range of Motion, Articular
keywords: Hamstrings; Intraoperative measurements; Knee flexion deformity and crouched posture; Muscle force-knee angle characteristics; Spasticity