Comparison of the rigidity and forefoot – Rearfoot kinematics from three forefoot tracking marker clusters during walking and weight-bearing foot pronation-supination

Clinical and biomechanical characteristics of responders and non-responders to insoles in individuals with excessive foot pronation during walking

This study aimed to identify the clinical and biomechanical factors of subjects with excessive foot pronation who are not responsive (i.e., "non-responders") to medially wedged insoles to increase knee adduction external moment. Ankle dorsiflexion range of motion, forefoot-shank alignment, passive hip stiffness, and midfoot passive resistance of 25 adults with excessive bilateral pronation were measured. Also, lower-limb angles and external moments were computed during walking with the participants using control (flat surface) and intervention insoles (arch support and 6° medial heel wedge). A comparison between "responders" (n = 34) and "non-responders" (n = 11) was conducted using discrete and continuous analyses. Compared with the responders, the non-responders had smaller forefoot varus (p = 0.014), larger midfoot passive internal torque peak (p = 0.005), and stiffness measured by the torsimeter (p = 0.022). During walking, non-responders had lower angle peaks for forefoot eversion (p = 0.001), external forefoot rotation (p = 0.037), rearfoot eversion (p = 0.022), knee adduction (p = 0.045), and external hip rotation (p = 0.022) and higher hip internal rotation angle peak (p = 0.026). Participants with small forefoot varus alignment, large midfoot passive internal torque, stiffness, small knee valgus, hip rotated internally, and foot-toed-in during walking did not modify the external knee adduction moment ("non-responders"). Clinicians are advised to interpret these findings with caution when considering the prescription of insoles. Further investigation is warranted to fully comprehend the response to insole interventions among individuals with specific pathologies, such as patellofemoral pain and knee osteoarthritis (OA).

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

BACKGROUND

The 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 QUESTION

Are there differences in angles from the RFM and OFM, obtained with independent and clustered tracking markers, during the stance phase of walking?

METHODS

Walking 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.

RESULTS

Differences 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).

SIGNIFICANCE

Rigid 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.

Midfoot passive stiffness affects foot and ankle kinematics and kinetics during the propulsive phase of walking

The midfoot joint complex (MFJC) is related to the mechanics and efficiency of the walking propulsive phase and low midfoot passive stiffness may require compensatory foot and ankle joint moments to avoid excessive pronation and inefficient propulsion. This study aimed to investigate the kinematics and kinetics of the MFJC and ankle during the propulsive phase of walking in subjects with larger and smaller midfoot passive stiffness. MFJC passive stiffness of 20 healthy adult participants, and the kinematics and kinetics of the MFJC (forefoot-rearfoot) and ankle (rearfoot-shank) during the stance phase of walking were measured. The participants were divided equally into two groups according to the MFJC passive stiffness. Ranges of motion (ROM) and mean joint moments were computed for the late stance. Independent t-tests (α = 0.05) revealed that subjects with lower midfoot passive stiffness showed an increased MFJC sagittal ROM (flattened longitudinal arch) (p = 0.002), increased ankle frontal ROM (more everted positions) (p = 0.002), increased MFJC frontal ROM (more inverted positions) (p = 0.019), as well as a tendency for larger ankle sagittal ROM (p = 0.056). They also showed increased MFJC (p = 0.021) and ankle (p = 0.018) moments in the sagittal plane, increased MFJC moment in the frontal plane (p = 0.047) and a tendency for a predominant ankle moment in the frontal (p = 0.058). Foot and ankle joint moments are possible strategies to reduce pronation and improve propulsion, but not sufficient to prevent the altered kinematics related to low midfoot stiffness. Therefore, midfoot passive stiffness is critical for foot and ankle kinematics and kinetics during walking propulsive phase and is a potential target of interventions.

Evaluation of the Validity, Reliability, and Kinematic Characteristics of Multi-Segment Foot Models in Motion Capture

This study aimed to evaluate the validity and reliability of our new multi-segment foot model by measuring a dummy foot, and examine the kinematic characteristics of our new multi-segment foot model by measuring the living body. Using our new model and the Rizzoli model, we conducted two experiments with a dummy foot that was moved within a range from -90 to 90 degrees in all planes; for the living body, 24 participants performed calf raises, gait, and drop jumps. Most three-dimensional (3D) rotation angles calculated according to our new models were strongly positively correlated with true values (r > 0.8, p < 0.01). Most 3D rotation angles had fixed biases; however, most of them were in the range of the limits of agreement. Temporal patterns of foot motion, such as those in the Rizzoli model, were observed in our new model during all dynamic tasks. We concluded that our new multi-segment foot model was valid for motion analysis and was useful for analyzing the foot motion using 3D motion capture during dynamic tasks.