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This study aimed to investigate how electromyography (EMG) cluster analysis of the rectus femoris (RF) could help to better interpret gait analysis in patients with cerebral palsy (CP). The retrospective gait data of CP patients were categorized into two groups: initial examination (E1, 881 patients) and subsequent examination (E2, 377 patients). Envelope-formatted EMG data of RF were collected. Using PCA and a combined PSO-K-means algorithm, main clusters were identified. Patients were further classified into crouch, jump, recurvatum, stiff and mild gait for detailed analysis. The clusters (labels) were characterized by a significant peak EMG activity during mid-swing (L1), prolonged EMG activity during stance (L2), and a peak EMG activity during loading response (L3). Notably, L2 contained 76% and 92% of all crouch patients at E1 and E2, respectively. Comparing patients with a crouch gait pattern in L2-E1 and L2-E2, two subgroups emerged: patients with persistent crouch (G1) and patients showing improvement at E2 (G2). The minimum activity of RF during 20–45% of the gait was significantly higher (p = 0.025) in G1 than in G2. A greater chance of improvement from crouch gait might be associated with lower RF activity during the stance phase. Using our findings, we could potentially establish an approach to improve clinical decision-making regarding treatment of patients with CP. [ABSTRACT FROM AUTHOR]

Goal of this work is a quantitative description of Jacquelin Perry's rocker concept by locating the position of the heel rocker and the forefoot rocker within segments of the foot via functional calibration. Two functional calibration tasks with the foot in ground contact were performed by ten typical developed adults and foot marker motion was captured. After applying a least-square method for constructing foot segments, their motion relative to the floor was analyzed via a functional algorithm. Resulting reference positions – namely the heel rotation center and the metatarsal rotation axis – were calculated. Further, the repeatability of the method and variability of outcome within the cohort was tested. The heel rotation center is located substantially posterior (25 mm) and slightly more inferior (5 mm). to the midpoint of the two markers placed medially and laterally on the calcaneus. Repeated measures reveal a variation of this location around 5 mm. The forefoot center is slightly more medial to the "toe marker" (DMT2) and substantially more inferior (19 mm). The metatarsal rotation axis is slightly tilted in the frontal and transverse plane against the metatarsal line given between markers on MT1 and MT5 with small variation in repeated measures (1–2°). The determination of heel rotation center and the metatarsal rotation axis relative to foot segments can be determined with good repeatability and their location meet the intuitive expectation. Since they have a direct biomechanical meaning in the foot roll-over process in gait, they may be used for a more functionally oriented definition of foot segments potentially improving the calculation of foot kinematics and kinetics in future work. • Foot calibration tasks with ground contact were performed by 10 adults. • These were applied to calculate heel rotation center and metatarsal axis. • Results are repeatable with low variation within the cohort (5 mm;5°). • Heel rotation center and metatarsal axis may be used for foot modeling. [ABSTRACT FROM AUTHOR]

Aim: To evaluate short-term (1y postoperatively; E1) and long-term (at least 4y postoperatively; E2) changes in hamstring muscle-tendon length (MTL) and lengthening velocity after hamstring lengthening in children with bilateral cerebral palsy (CP).Method: Three-dimensional gait analysis was performed in 19 children (16 males, 3 females; 36 limbs; mean age at surgery 9y [SD 3y]; range 6-10y) with flexed knee gait, preoperative ankle dorsiflexion lower than 20 degrees, and CP before bilateral hamstring lengthening (E0), at E1 and E2. Hamstring MTL (normalized by leg length) and velocity were assessed via OpenSim software.Results: MTL increased from E0 to E1 (p=0.004) and decreased from E1 to E2 (p<0.020). Hamstring lengthening velocity did not change. In the subgroup with short, not slow hamstrings, the increase in MTL was maintained at E2.Interpretation: Hamstring lengthening is an efficient procedure to lengthen short and/or slow hamstrings short-term. The desired outcome with maintenance of the postoperative changes in hamstring MTL is only achieved for preoperatively short, not slow hamstrings.What This Paper Adds: Surgical hamstring lengthening can be confirmed via musculoskeletal modelling in OpenSim software. Surgical hamstring lengthening in cerebral palsy does not change hamstring lengthening velocity. Short, not slow hamstrings present a long-lasting muscle-tendon length (MTL) increase after hamstring lengthening. Changes in MTL after hamstring lengthening cannot be maintained for slow hamstrings. MTL does not change after hamstring lengthening for neither short nor slow hamstrings. [ABSTRACT FROM AUTHOR]