The effect of mono- versus multi-segment musculoskeletal models of the foot on simulated triceps surae lengths in pathological and healthy gait.

Estimating muscle-tendon complex (MTC) lengths is important for planning of soft tissue surgery and evaluating outcomes, e.g. in children with cerebral palsy (CP). Conventional musculoskeletal models often represent the foot as one rigid segment, called a mono-segment foot model (mono-SFM). However, a multi-segment foot model (multi-SFM) might provide better estimates of triceps surae MTC lengths, especially in patients with foot deformities. What is the effect of a mono- versus a multi-SFM on simulated ankle angles and triceps surae MTC lengths during gait in typically developing subjects and in children with CP with equinus, cavovarus or planovalgus foot deformities? 50 subjects were included, 10 non-affected adults, 10 typically developing children, and 30 children with spastic CP and foot deformities. During walking trials, marker trajectories were collected for two marker models, including a mono- and multi-segment foot; respectively Newington gait model and Oxford foot model. Two musculoskeletal lower body models were constructed in OpenSim with either a mono- or multi-SFM based on the corresponding marker models. Normalized triceps surae MTC lengths (soleus, gastrocnemius medialis and lateralis) and ankle angles were calculated and compared between models using statistical parametric mapping RM-ANOVAs. Root mean square error values between simulated MTC lengths were compared using Wilcoxon signed-rank and rank-sum tests. Mono-SFM simulated significantly more ankle dorsiflexion (7.5 ± 1.2°) and longer triceps surae lengths (difference; soleus:2.6 ± 0.29 %, gastrocnemius medialis:1.7 ± 0.2 %, gastrocnemius lateralis:1.8 ± 0.2%) than a multi-SFM. Differences between models were larger in children with CP compared to typically developing children and larger in the stance compared to the swing phase of gait. Largest differences were found in children with CP presenting with planovalgus (4.8 %) or cavovarus (3.8 %) foot deformities. It is advisable to use a multi-SFM in musculoskeletal models when simulating triceps surae MTC lengths, especially in individuals with planovalgus or cavovarus foot deformities.

Zandbergen MA ，Schallig W ，Stebbins JA ，Harlaar J ，van der Krogt MM ... -  《-》

Multi-segment foot kinematics during gait in children with spastic cerebral palsy.

Foot deformities (e.g. planovalgus and cavovarus) are very common in children with spastic cerebral palsy (CP), with the midfoot often being involved. Dynamic foot function can be assessed with 3D gait analysis including a multi-segment foot model. Incorporating a midfoot segment in such a model, allows quantification of separate Chopart and Lisfranc joint kinematics. Yet, midfoot kinematics have not previously been reported in CP. What is the difference in multi-segment kinematics including midfoot joints between common foot deformities in CP and typically-developing feet? 103 feet of 57 children with spastic CP and related conditions were retrospectively included and compared with 15 typically-developing children. All children underwent clinical gait analysis with the Amsterdam Foot Model marker set. Multi-segment foot kinematics were calculated for three strides per foot and averaged. A k-means cluster analysis was performed to identify foot deformity groups that were present within CP data. The deformity type represented by each cluster was based on the foot posture index. Kinematic output of the clusters was compared to typically-developing data for a static standing trial and for the range of motion and kinematic waveforms during walking, using regular and SPM independent t-tests respectively. A neutral, planovalgus and varus cluster were identified. Neutral feet showed mostly similar kinematics as typically-developing data. Planovalgus feet showed increased ankle valgus and Chopart dorsiflexion, eversion and abduction. Varus feet showed increased ankle varus and Chopart inversion and adduction. This study is the first to describe Chopart and Lisfranc joint kinematics in different foot deformities of children with CP. It shows that adding a midfoot segment can provide additional clinical and kinematic information. It highlights joint angles that are more distinctive between deformities, which could be helpful to optimize the use of multi-segment foot kinematics in the clinical decision making process.

Schallig W ，Piening M ，Quirijnen L ，Witbreuk MM ，Buizer AI ，van der Krogt MM ... -  《-》

Medial gastrocnemius and soleus muscle-tendon unit, fascicle, and tendon interaction during walking in children with cerebral palsy.

Barber L ，Carty C ，Modenese L ，Walsh J ，Boyd R ，Lichtwark G ... -  《-》

Ankle and knee coupling in patients with spastic diplegia: effects of gastrocnemius-soleus lengthening.

Baddar A ，Granata K ，Damiano DL ，Carmines DV ，Blanco JS ，Abel MF ... -  《JOURNAL OF BONE AND JOINT SURGERY-AMERICAN VOLUME》

Discrepancy between true ankle dorsiflexion and gait kinematics and its association with severity of planovalgus foot deformity.

Sung KH ，Chung CY ，Lee KM ，Kwon KB ，Lee JH ，Park MS ... -  《BMC MUSCULOSKELETAL DISORDERS》