Modular control of muscle coordination patterns during various stride time and stride length combinations

BackgroundModular organization in muscular control is generally specified as synergistic muscle groups that are hierarchically organized. There are conflicting perspectives regarding modular organization for regulation of walking speeds, with regard to whether modular organization is relatively consistent across walking speeds. This conflict might arise from different stride time (time for one stride) and stride length combinations for achieving the same walking speed.Research questionDoes the regulation of the modular organization depend on stride time and stride length (stride time-length) combinations?MethodsTen healthy men walked at a moderate speed (nondimensional speed = 0.4) on a treadmill at five different stride time-length combinations (very short, short, preferred, long, and very long). Surface electromyograms from 16 muscles in the trunk and lower limb were recorded. The modular organization was modeled as muscle synergies, which represent groups of synchronously activated muscles. Muscle synergies were extracted using a decomposition technique. The number of synergies and their activation durations were analyzed.ResultsThe number of synergies was consistent in the preferred and quasi-preferred condition (median: 4.5 [short], 4.5 [preferred], 5 [long]), while it varied in the extreme condition (median: 4 [very short] and 6 [very long]; 0.02 ≤ p ≤ 0.09). Gait parameters (stride time, stride length, stance time, swing time, and double stance time) were significantly different for preferred and quasi-preferred conditions (p < 0.03).SignificanceOur results provide additional insights on the flexibility of modular control during walking, namely that the number of synergies or activations are fine-tuned even within one walking speed. Our finding implies that a variety of walking patterns can be achieved by consistent synergies except for extreme walking patterns.     

O 089 - A soft robotic exosuit assisting the paretic ankle in patients post-stroke: Effect on muscle activation during overground walking

This study compared overground walking with and without exosuit assistance in post-stroke patients. Exosuit-assisted walking was found to improve paretic propulsion and ground clearance during swing, two common gait deviations in stroke patients. No changes in leg muscle activity was found, motivating further study of the exosuit as a tool for gait training during stroke rehabilitation.     

Comparison between the Rizzoli and Oxford foot models with independent and clustered tracking markers

BackgroundThe Rizzoli Foot Model (RFM) and Oxford Foot Model (OFM) are used to analyze segmented foot kinematics with independent tracking markers. Alternatively, rigid marker clusters can be used to improve markers’ visualization and facilitate analyzing shod gait.Research questionAre there differences in angles from the RFM and OFM, obtained with independent and clustered tracking markers, during the stance phase of walking?MethodsWalking kinematics of 14 non-disabled participants (25.2 years (SD 2.8)) were measured at self-selected speed. Rearfoot-shank and forefoot-rearfoot angles were measured from two models with two tracking methods: RFM, OFM, RFM-cluster, and OFM-cluster. In RFM-cluster and OFM-cluster, the rearfoot and forefoot tracking markers were rigidly clustered, fixed on rods’ tips attached to a metallic base. Statistical Parametric Mapping (SPM) One-Way Repeated Measures ANOVAs and SPM Paired t-tests were used to compare waveforms. Coefficients of Multiple Correlation (CMC) quantified the similarity between waveforms. One-way Repeated Measures ANOVAs were conducted to compare the ranges of motion (ROMs), and pre-planned contrasts investigated differences between the models and tracking methods. Intraclass Correlation Coefficients (ICC) were computed to verify the similarity between ROMs.ResultsDifferences occurred mostly in small parts of the stance phase for the cluster vs. non-cluster comparisons and the RFM vs. OFM comparisons. ROMs were slightly different between the models and tracking methods in most comparisons. The curves (CMC ≥ 0.71) were highly similar between the models and tracking methods. The ROMs (ICC ≥ 0.67) were moderatetly to highly similar in most comparisons. RFM vs. RFM-cluster (forefoot-rearfoot angle - transverse plane), OFM vs. OFM-cluster and RFM vs. OFM (forefoot-rearfoot angle - frontal plane) were not similar (non-significant).SignificanceRigid clusters are an alternative for tracking rearfoot-shank and forefoot-rearfoot angles during the stance phase of walking. However, specific differences should be considered to contrast results from different models and tracking methods.     

Elbow Kinematics and Function Following Treatment with Open Arthrolysis and Hinged External Fixator

Objective

Open arthrolysis (OA) combined with hinged external fixator (HEF) is a promising surgical option for patients with elbow stiffness. This study aimed to investigate elbow kinematics and function following a combined treatment with OA and HEF in elbow stiffness cases.

Methods

Patients treated with OA with or without HEF due to elbow stiffness were recruited between August 2017 and July 2019. Elbow flexion-extension motion and function (Mayo elbow performance scores, MEPS) were recorded and compared between patients with and without HEF during a 1-year follow-up period. Additionally, those with HEF were assessed by dual fluoroscopy at week 6 postoperatively. Flexion-extension and varus-valgus motions, as well as ligament insertion distances of the anterior medial collateral ligament (AMCL) and lateral ulnar collateral ligament (LUCL), were compared between the surgical and intact sides.

Results

This study included 42 patients, of which 12 with HEF demonstrated a similar flexion-extension angle and range of motion (ROM) and MEPS as the other patients. In patients with HEF, the surgical elbows showed limitations in flexion-extension (maximal flexion, 120.5° ± 5.3° vs 140.4° ± 6.8°; maximal extension, 13.1° ± 6.0° vs 6.4° ± 3.0°; ROM, 107.4° ± 9.9° vs 134.0° ± 6.8°; all Ps < 0.01) compared with the contralateral sides. During elbow flexion, a gradual valgus-to-varus transition of the ulna, increase in the AMCL insertion distance, and steady change in the LUCL insertion distance were observed, with no significant differences between the bilateral sides.

Conclusions

Patients treated with OA and HEF demonstrated similar elbow flexion-extension motion and function to those treated with OA alone. Although the use of HEF could not restore an intact flexion-extension ROM and might result in some minor but not significant changes in kinematics, it contributed to clinical outcomes comparable to that of the treatment with OA alone.