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Background Multi-segment foot models (MFMs) for assessing three-dimensional segmental foot motions are calculated via various analytical methods. Although validation studies have already been conducted, we cannot compare their results because the experimental environments in previous studies were different from each other. This study aims to compare the kinematics, repeatability, and reproducibility of five MFMs in the same experimental conditions. Methods Eleven healthy males with a mean age of 26.5 years participated in this study. We created a merged 29-marker set including five MFMs: Oxford (OFM), modified Rizzoli (mRFM), DuPont (DFM), Milwaukee (MiFM), and modified Shriners Hospital for Children Greenville (mSHCG). Two operators applied the merged model to participants twice, and then we analysed two relative angles of three segments: shank-hindfoot (HF) and hindfoot-forefoot (FF). Coefficients of multiple correlation (CMC) and mean standard errors were used to assess repeatability and reproducibility, and statistical parametric mapping (SPM) of the t-value was employed to compare kinematics. Results HF varus/valgus of the MiFM and mSHCG models, which rotated the segment according to radiographic or goniometric measurements during the reference frame construction, were significantly more repeatable and reproducible, compared to other models. They showed significantly more dorsiflexed HF and plantarflexed FF due to their static offset angles. DFM and mSHCG showed a greater range of motion (ROM), and some models had significantly different FF points of peak angle. Conclusions Under the same conditions, rotating the segment according to the appropriate offset angle obtained from radiographic or goniometric measurement increased reliability, but all MFMs had clinically acceptable reliability compared to previous studies. Moreover, in some models, especially HF varus/valgus, there were differences in ROM and points of peak angle even with no statistical difference in SPM curves. Therefore, based on the results of this study, clinicians and researchers involved in the evaluation of foot and ankle dysfunction need an understanding of the specific features of each MFM to make accurate decisions.

Background The feet play an essential role in shock absorption, and foot posture is closely related to gait. The compensatory mechanism under heavy-load conditions in individuals with mild flatfoot is poorly understood. In the authors’ country, individuals with mild flatfoot are drafted as active-duty soldiers and participate in military rucking wearing heavy backpacks. This study investigated the effect of backpack load on gait and foot plantar pressure and possible differences in participants with mild flatfoot. The average weight of the backpack during military rucking (approximately 20 kg), was simulated in this study. Methods This study prospectively enrolled 30 healthy young males, divided into a control group (CON, n  = 15) and a mild low-arched group (MLA, n  = 15), based on the presence of flatfoot. Segmental foot kinematics were evaluated using a three-dimensional multi-segment foot model, and gait data of the temporal and spatial parameters were obtained. The dynamic plantar pressure was simultaneously measured using a pedobarography platform with gait trials. The protocol was repeated with all participants wearing 20 kg backpacks. Comparisons between the baseline and loaded states, as well as comparison between groups, were conducted. Results Although the cadence, gait speed, and stride length decreased in the loaded condition, step time and proportion of the stance phase increased in both groups. Although the MLA group showed more supinated and abducted positions of the forefoot and more pronated positions of the hindfoot than the CON group, the change in intersegmental foot and ankle motion in each group after backpack loading was minimal. However, the former showed a larger step width and a greater increase in contact area in the midfoot region, while the latter demonstrated a greater increase in peak pressure. Conclusions Individuals with mild flatfoot demonstrated significantly different gait curve patterns (waveforms) compared to the controls. In the loaded condition, the CON and MLA groups may have adopted different strategies to maintain balance during gait. We suggest that although individuals with asymptomatic mild flatfoot are drafted as active-duty soldiers, they should be thoroughly investigated under loaded conditions, and orthoses may be helpful.

Background Different multi-segment foot models have been used to explore the effect of foot orthoses. Previous studies have compared the kinematic output of different multi-segment foot models, however, no study has explored if different multi-segment foot models detect similar kinematic changes when wearing a foot orthoses. The aim of this study was to compare the ability of two different multi-segment foot models to detect kinematic changes at the hindfoot and forefoot during the single and double support phases of gait when wearing a foot orthosis. Methods Foot kinematics were collected during walking from a sample of 32 individuals with and without a foot orthosis with a medial heel bar using an eight-camera motion capture system. The Oxford Foot Model (OFM) and a multi-segment foot model using the Calibrated Anatomical System Technique (CAST) were applied simultaneously. Vector field statistical analysis was used to explore the kinematic effects of a medial heel bar using the two models, and the ability of the models to detect any changes in kinematics was compared. Results For the hindfoot, both models showed very good agreement of the effect of the foot orthosis across all three anatomical planes during the single and double support phases. However, for the forefoot, the level of agreement between the models varied with both models showing good agreement of the effect in the coronal plane but poorer agreement in the transverse and sagittal planes. Conclusions This study showed that while consistency exists across both models for the hindfoot and forefoot in the coronal plane, the forefoot in the transverse and sagittal planes showed inconsistent responses to the foot orthoses. This should be considered when interpreting the efficacy of different interventions which aim to change foot biomechanics.

Background Accurately measuring of intrinsic foot kinematics using skin mounted markers is difficult, limited in part by the physical dimensions of the foot. Existing kinematic foot models solve this problem by combining multiple bones into idealized rigid segments. This study presents a novel foot model that allows the motion of the 26 bones to be individually estimated via a combination of partial joint constraints and coupling the motion of separate joints using kinematic rhythms. Methods Segmented CT data from one healthy subject was used to create a template Glasgow-Maastricht foot model (GM-model). Following this, the template was scaled to produce subject-specific models for five additional healthy participants using a surface scan of the foot and ankle. Forty-three skin mounted markers, mainly positioned around the foot and ankle, were used to capture the stance phase of the right foot of the six healthy participants during walking. The GM-model was then applied to calculate the intrinsic foot kinematics. Results Distinct motion patterns where found for all joints. The variability in outcome depended on the location of the joint, with reasonable results for sagittal plane motions and poor results for transverse plane motions. Conclusions The results of the GM-model were comparable with existing literature, including bone pin studies, with respect to the range of motion, motion pattern and timing of the motion in the studied joints. This novel model is the most complete kinematic model to date. Further evaluation of the model is warranted.

Background Several 3D multi-segment foot models (MFMs) have been introduced for the in vivo analysis of dynamic foot kinematics. However, reproducibility of a model should be checked and ascertained before clinical utilization of a MFM. The purpose of this study was to determine the reliability of recently introduced MFM with a 15-marker set by assessing the participant’s stride-to-stride (intra-session) and visit-to-revisit (inter-session) repeatability. Methods Twenty healthy adults with a mean age of 28.9 years (10 males and 10 females) were tested. Three representative strides from five separate trials were used for analysis from each session. Kinematic data of foot segmental motion was collected and tracked using the Foot3D Multi-Segment Software (Motion Analysis Co., Santa Rosa. CA). A retest was performed in the same manner at an interval of 4 weeks. Coefficients of multiple correlation (CMC) and intra-class correlation coefficient (ICC) were calculated in order to assess the intra-session and inter-session repeatability. Results Inter-segment foot angles from healthy adults from a MFM with 15-marker set showed a narrow range of variability during the gait cycle. The mean intra-session ICC was 0.981 (±0.010), which was interpreted as excellent. The mean intra-session CMC was 0.948 (±0.027), which was interpreted as very good repeatability. The mean inter-session ICC was 0.886 (±0.047) and the mean inter-session CMC was 0.801 (±0.077), which were interpreted as excellent and good repeatability, respectively. Conclusion We demonstrated a MFM with a 15-marker set had high intra-session and inter-session repeatability, especially in sagittal plane motion. We thought this MFM would be applicable to evaluation of the segmental foot motion during gait.

Background Detailed kinematics of the foot has been frequently reported on in the literature, specifically using various multi-segment foot models. It is important to identify the reliability of a multi-segment foot model in a population of mixed genders and activity levels, while walking in commonly used footwear. The main objective of this study was to investigate the between-day reliability and within-session variability of the Oxford Foot Model (OFM) while walking in a neutral cushioning shoe. Methods A 7-camera Vicon motion capture system was used along with 29 passive reflective markers, placed on the participant to examine the multi-segment foot kinematics of the left foot using the OFM. Windows were cut in New Balance 840 shoes following reports from a previous investigation to maintain shoe integrity during testing. Two walking sessions on separate days were collected for 12 healthy participants, with an average total of 22 gait cycles per day. Results ICCs ranged from 0.020 to 0.964 for between-day reliability, and within-session ICC values ranged from 0.268 to 0.985. Between-day ICC values of the relative measures (excursion and range of motion (ROM)) were higher than the absolute angle measures (angle at foot strike and peak angle). Largest differences were measured in the transverse plane, and the smallest differences in the sagittal plane. Bland-Altman plots revealed best agreement in the frontal and sagittal planes. SEM values ranged from 0.04 to 3.5 for the between-day reliability. Conclusions Between-day reliability and within-session variability were comparable to previous studies for adults walking barefoot and shod. This research demonstrates that the OFM can produce reliable data when applied to the assessment of a shod foot.

Background Understanding how kinematic multi-segment foot modelling influences the utility of Plug-in-Gait calculations of the knee adduction moment (KAM) during shod walking is relevant to knee osteoarthritis (OA). Multi-segment foot markers placed on the skin through windows cut in to the shoe provide a more accurate representation of foot mechanics than the traditional marker set used by Plug-in-Gait, which uses fewer markers, placed on the shoe itself. We aimed to investigate whether Plug-in-Gait calculation of the KAM differed when using a kinematic multi-segment foot model compared to the traditional Plug-in-Gait marker set. Methods Twenty people with medial knee OA underwent gait analysis in two test conditions: i) Plug-in-Gait model with its two standard foot markers placed on the shoes and; ii) Plug-in-Gait with the heel marker virtualised from a modified-Oxford Foot Model where 8 ft markers were placed on the skin through windows cut in shoe uppers. Outcomes were the peak KAM, KAM impulse and other knee kinetic and kinematic variables. Results There were no differences ( P  > 0.05) in any gait variables between conditions. Excellent agreement was found for all outcome variables, with high correlations ( r  > 0.88-0.99, P  < 0.001), narrow limits of agreement and no proportional bias ( R 2  = 0.03–0.14, P  > 0.05). The mean difference and 95% confidence intervals for peak KAM were also within the minimal detectable change range demonstrating equivalence. Conclusions Plug-in-Gait calculations of the KAM are not altered when using a kinematic multi-segment foot marker model with skin markers placed through windows cut in to the shoe, instead of the traditional marker set placed on top of shoes. Researchers may be confident that applying either foot model does not change the calculation of the KAM using Plug-in-Gait.

Background Although accumulative evidence exists that support the applicability of multi-segmental foot models (MFMs) in evaluating foot motion in various pathologic conditions, little is known of the effect of aging on inter-segmental foot motion. The objective of this study was to evaluate differences in inter-segmental motion of the foot between older and younger adult healthy females during gait using a MFM with 15-marker set. Methods One hundred symptom-free females, who had no radiographic evidence of osteoarthritis, were evaluated using MFM with 15-marker set. They were divided into young ( n  = 50, 20–35 years old) and old ( n  = 50, 60–69 years old) groups. Coefficients of multiple correlations were evaluated to assess the similarity of kinematic curve. Inter-segmental angles (hindfoot, forefoot, and hallux) were calculated at each gait phase. To evaluate the effect of gait speed on intersegmental foot motion, subgroup analysis was performed according to the similar speed of walking. Results Kinematic curves showed good or excellent similarity in most parameters. Range of motion in the sagittal ( p  < 0.001) and transverse ( p  = 0.001) plane of the hallux, and sagittal ( p  = 0.023) plane of the forefoot was lower in older females. The dorsiflexion ( p  = 0.001) of the hallux at terminal stance and pre-swing phases was significantly lower in older females. When we compared young and older females with similar speed, these differences remained. Conclusions Although the overall kinematic pattern was similar between young and older females, reduced range of inter-segmental motion was observed in the older group. Our results suggest that age-related changes need to be considered in studies evaluating inter-segmental motion of the foot.

Background Walking down stairs is a clinically relevant daily activity for older persons. The aim of this pilot study was to investigate the impact of cheilectomy on walking on level ground and on stairs. Methods 3D motion analysis of foot kinematics was performed in eight patients with hallux rigidus and 11 healthy control participants with a 12-camera system, using the Heidelberg foot measurement method before and one year after surgery. The clinical results were documented using the AOFAS Scale. Results The range of motion of the first metatarsophalangeal joint did not improve after the operation under any gait condition. Preoperatively, hallux dorsi-/plantarflexion in level walking was 11.9° lower in patients than in controls ( p  = 0.006), postoperatively 14.5° lower ( p  = 0.004). Comparing walking conditions in patients, hallux dorsi-/plantarflexion was significantly higher in level walking than in climbing stairs (difference up stairs – level: -8.1°, p  = 0.018). The AOFAS Scale improved significantly from 56.9 ± 19.9 points (mean ± SD), preoperatively, to 75.9 ± 13.9 points, postoperatively ( p  = 0.027). Conclusions Cheilectomy is appropriate for reducing symptoms of hallux rigidus. However, neither a positive influence on the range of motion in walking on level ground and on stairs nor a functional improvement was observed in this group of patients. Trial registration NCT01804491

Walking on uneven surfaces alters foot joint kinematics and challenges gait stability. The intricate joint coupling relationship of the human foot, which is essential for biomechanical adaptations, particularly when encountering uneven surfaces, remains unclear. This study focused on quantifying foot joint coordination on cross-slopes using a markerless gait analysis method. Twelve healthy subjects performed walking tests on a gait platform under level, 8° everted and 8° inverted surface conditions. Segmental motion between rearfoot, midfoot, forefoot, and hallux were analyzed using a point cloud-based multi-segment foot model (MSFM). Adaptive changes of multi-segmental foot kinematics and inter-joint coupling relationships were compared across different cross-slope conditions. The results indicated that the rearfoot dominated frontal plane motion during everted surface walking in both middle and late stance, while the forefoot and midfoot dominated during inverted surface walking, respectively. In contrast to level walking, the sagittal-plane motion of the midtarsal joints during everted and inverted surface walking did not significantly contribute to foot kinematics at push-off. Further analysis reveals that significant variabilities exist in joint coupling behavior at different phases of the cross-slope walking.These findings demonstrate the effectiveness of the proposed method in detecting the complex inter-joint kinematics and coupling patterns of the human foot during cross-slope walking. The results provide insights into the kinematic changes of foot joints for terrain adaptation in uneven walking surfaces and advocate the application of novel motion analysis methods for tracking natural gait patterns.