Ankle Rotation Research Articles

The rocker-soled shoes change the kinematics and muscle contractions of the lower extremity during various functional movement

While rocker-shaped soles have become popular for running shoes, whether or not this type of shoe benefits other functional movements has rarely been discussed. The purpose of this study was to investigate the effect of rocker-soled shoes on lower extremity biomechanics during different exercises. Seventeen healthy university students were recruited. A motion capture analysis system and surface electromyography were used to measure kinematics and muscle activation while walking (10 m), running (10 m), cutting, jumping, and ascending and descending stairs. The results showed that when wearing rocker-soled shoes, greater peak external ankle rotation was present during most exercises. Smaller peak joint angles were observed in hip extension and external rotation when walking, and in ankle dorsiflexion when ascending stairs and jumping. The vastus medialis and vastus lateralis contracted more in most exercises when rocker-soled shoes were worn. However, the biceps femoris and medial gastrocnemius showed less muscle contraction. Wearing rocker-soled shoes during testing movements change the kinematics and muscle contractions of the lower extremity. These findings may provide information for choosing shoes for different exercises or training purposes.

Achilles tendinopathy and plantar fasciopathy: Are we ignoring calcaneal bone morphology? – A radiological assessment of calcaneal parameters

BackgroundA radiological study was conducted to determine whether calcaneal morphological differences contribute to the pathophysiology of Achilles tendinopathy and plantar fasciopathy. This study is aimed to support our new hypothesis to explain the pathophysiology leading to recalcitrant disease and also to identify the role of calcaneal osteotomy for treating these conditions. Materials and methodsCalcaneal width and height distance deviation from centre of ankle joint rotation was measured on standardised lateral weight bearing Ankle radiographs. A comparison was made between control group and study group to identify the differences in measured parameters. ResultsSignificant difference (P = 0.05) was observed in calcaneal width distance in study group with Achilles tendinopathy. In Plantar fasciopathy the vertical distance was reduced suggesting flattening of arch in study group. However, the difference was not statistically significant. ConclusionThe study identifies the importance of evaluating calcaneal morphology for patients with recalcitrant Achilles tendinopathy and plantar fasciopathy. A new hypothesis is proposed to explain the high stresses produced in entire Achilles –calcaneus –plantar fascia unit which leads to chronic inflammatory response and intra substance degeneration.

Design and kinematic investigation of an actuated prosthetic ankle during walking

Due to the varied needs of persons who have lost a lower limb in their everyday lives, ankle-foot prosthetic technology is continually evolving. Numerous prosthetic ankles have been created in recent years to restore the ankle function of lower limb amputees. Most ankle foot prostheses, on the other hand, are passive, such as the solid ankle cushion heel and the energy storage and release foot (ESAR). The solid ankle foot can only provide steady vertical support during ambulation; however, the ESAR foot can store energy and gradually release it throughout human walking periods, hence increasing the walking pace of amputees. The aim of this work is to describe the design and manufacture of an actuated ankle-foot prosthesis. The main benefit of powered ankles is that they are capable of mimicking natural stride, particularly in steep or uneven terrain conditions. The primary objective is to establish two degrees of freedom of ankle rotation in two planes, plantar flexion and dorsiflexion in the sagittal plane, besides inversion and eversion in the frontal plane. As software can improve the gait stability, an automatic modifiable transmission arrangement was prepared for delivering the current design motions in the sagittal plane based on empirical collected biomechanical data related to passive prosthetic normal gait circumstances. However, the ankle rolling in the frontal plane was guided mechanically by means of mono leaf spring. The majority of the ankle mechanical components are made of 7075-T6 aluminum alloy and are integrated onto ESAR carbon fiber laminated foot. For a unilateral above-knee amputee, the ankle function at self-selected walking was assessed, achieving maximum results of 10° inversion, 10° eversion, 12° plantar flexion and 18° dorsiflexion ankle angles. Also, the patient gait experiment in a normal cadence showed an improvement in plantar flexion behavior for the powered ankle in contrast with the passive ankle

The development and evaluation of a fully automated markerless motion capture workflow

This study presented a fully automated deep learning based markerless motion capture workflow and evaluated its performance against marker-based motion capture during overground running, walking and counter movement jumping. Multi-view high speed (200 Hz) image data were collected concurrently with marker-based motion capture (criterion data), permitting a direct comparison between methods. Lower limb kinematic data for 15 participants were computed using 2D pose estimation, our 3D fusion process and OpenSim based inverse kinematics modelling. Results demonstrated high levels of agreement for lower limb joint angles, with mean differences ranging “0.1° − 10.5° for hip (3 DoF) joint rotations, and 0.7° − 3.9° for knee (1 DoF) and ankle (2 DoF) rotations. These differences generally fall within the documented uncertainties of marker-based motion capture, suggesting that our markerless approach could be used for appropriate biomechanics applications. We used an open-source, modular and customisable workflow, allowing for integration with other popular biomechanics tools such as OpenSim. By developing open-source tools, we hope to facilitate the democratisation of markerless motion capture technology and encourage the transparent development of markerless methods. This presents exciting opportunities for biomechanics researchers and practitioners to capture large amounts of high quality, ecologically valid data both in the laboratory and in the wild.

Validating Foot Center Axis and Ankle Rotation using Weight-Bearing CT

Category: Ankle; Ankle Arthritis Introduction/Purpose: Even as its popularity increases, there remain many unanswered questions regarding total ankle arthroplasty. One debate considers the proper rotation of the talar component to restore native, non-osteoarthritic anatomy. The foot center axis is a unique anatomic concept that considers the position of the native foot relative to the ankle. The present pilot study sought to evaluate the reproducibility of axial alignment measurements, including the foot center on weight-bearing CT in patients without ankle osteoarthritis. Methods: Following IRB approval, charts were reviewed to identify patients without ankle osteoarthritis, trauma or other deformity who received a weightbearing CT scan. A pilot group of n=8 patients were included for a total of n=10 limbs. Average age was 50.1 +/- 14 and there were 38% female patients. All measurements were made on MPR (multiplanar reformation) axial reconstructions. Cobb angle measurements between the anatomic foot center, the second, the fourth metatarsal and the gutter bisector or medial gutter line were recorded by n=4 observers. Intraclass correlation (ICC) was produced using a two-way random effects model with absolute agreement and other statistical testing was performed by IBM SPSS Statistics for Windows, Version 27.0. Armonk, NY. Results: The average gutter bisector angle was 6.2 deg +/- 2.0 and the average angle between the medial base of the 1st metatarsal head, lateral base of the 5th metatarsal head and the posterior calcaneus was 33.0 deg +/- 2.6. Amongst the observers, the ICC for these landmarks were 0.95 and 0.96 respectively. The average cobb angle measurement between the gutter bisector angle and the second metatarsal was 8.3 deg +/- 7.3, with a corresponding ICC of 0.96. The average cobb angle measurement between the gutter bisector angle and the anatomic foot center was 5.6 deg +/- 4.3 and the average cobb angle measurement between the medial gutter line and the anatomic foot center was 6.23 deg +/- 6. Amongst the observers, the ICC for these measurements were 0.81 and 0.81 respectively. Conclusion: In a small pilot study of patients without osteoarthritis who underwent weight-bearing CT scans there was good (ICC>0.75-0.90) to excellent (ICC>0.90) agreement amongst observers for measurements of foot center axis and ankle rotation. These findings validate the reproducibility and agreement of these manually constructed measurements for assessing the relationship between the foot center axis and ankle rotation. Future studies will expand upon the use of these measurements to define non-arthritic anatomy. The anatomic foot center may be a useful guide for establishing intra-operative foot orientation when performing total ankle arthroplasty.

Comparison of Foot Center Axis and Ankle Rotation using Weight-Bearing CT

Category: Ankle; Ankle Arthritis Introduction/Purpose: Even as its popularity increases, there remain many unanswered questions regarding total ankle arthroplasty. One debate considers how best to restore proper rotation of the talar component relative to native, non- osteoarthritic anatomy. At present, two common schools of thought are to parallel the talar component rotation with the medial gutter line or to choose a line that bisects the gutters. These axis' are then considered with respect to a chosen foot axis, often defined by the second metatarsal or second toe clinically. The present study sought to define the foot center axis relative to the ankle on weight-bearing CT in patients without ankle osteoarthritis to inform talar component positioning in total ankle arthroplasty. Methods: Following IRB approval, charts were reviewed to identify patients without ankle osteoarthritis, trauma or other deformity who received a weightbearing CT scan. A pilot group of n=34 patients were included for a total of n=50 limbs. Average age was 50.3 +/- 7 and there were = 54% female patients. All measurements were made on MPR (multiplanar reformation) axial reconstructions. Cobb angle measurements between the anatomic foot center, the second, the fourth metatarsal and the gutter bisector or medial gutter line were recorded. Statistical analysis was performed by IBM SPSS Statistics for Windows, Version 27.0. Armonk, NY. Results: The mean gutter bisector angle was 5.7 deg +/- 2.0. The mean cobb angle between the anatomic foot center and the medial gutter line was 6.1 deg +/- 4.4 and between the anatomic foot center and gutter bisector was 6.3 deg +/- 4.8, there was no statistical difference between measurements (p=0.62, Table 1). The mean cobb angle between the second metatarsal and the gutter bisector was 9.9 deg +/- 6.8, whereas the mean cobb angle between the fourth metatarsal and the gutter bisector was 7.5 deg +/- 5.2, which was not statistically significant (p=0.053). There was no statistical difference between mean cobb angle measurements between the anatomic foot center and the gutter bisector and the fourth metatarsal and the gutter bisector (p=0.243), but there was statistical difference between mean cobb angle measurements of the second metatarsal and the gutter bisector and the anatomic foot center and the gutter bisector (p=0.003). Conclusion: The axial alignment of the foot center axis relative to the ankle in patients without deformity or osteoarthritis is most collinear with the medial gutter line. In general, the axial alignment of the ankle joint relative to the foot in patients without osteoarthritis tends towards <10 degrees of difference on weight-bearing CT, regardless of method chosen. Due to both the consistency of measure and reproducibility of measure on pre-operative weight-bearing CT, the anatomic foot center may be a useful guide for establishing intra-operative foot orientation when performing total ankle arthroplasty.

Effects of running fatigue on lower extremity symmetry among amateur runners: From a biomechanical perspective.

The objective of this study was to examine the effects of running fatigue on the symmetry of lower limb biomechanical parameters in eighteen male amateur runners. The marker trajectories and ground reaction forces were collected before and after the running-induced fatigue protocol. Symmetry angles (SA) were used to quantify the symmetry of each parameter. Normality tests and Paired sample T-tests were carried out to detect bilateral lower limb differences and SA of parameters between pre- and post-fatigue. One-dimensional statistical parameter mapping (SPM_1d) was used to compare parameters with the characteristic of one-dimensional time series data of lower limbs. After fatigue, the SA of knee extension angles, knee abduction moment, and hip joint flexion moment increased by 17%, 10%, and 11% respectively. In comparison, the flexion angle of the knee joint decreased by 5%. The symmetry of internal rotation of ankle, knee and hip joints increased after fatigued, while the SA of external rotation of the three joints decreased significantly. These findings provide preliminary evidence that fatigue changes lower limb symmetry in running gait and may have implications for understanding running-related injuries and performance.

Development and Evaluation of Dorsiflexion Support Unit Using Elastomer Embedded Flexible Joint

In our previous study, we developed a walking support shoe with an elastomer-embedded flexible joint (EEFJ) to assist the function of tibialis anterior (TA) in initial stances (IC) and swing phases (SW). However, its usability and supporting effect have not been sufficiently evaluated. Therefore, in this study, we developed a dorsiflexion support unit (DSU) using the EEFJs with consideration on the usability for frail persons. Their needs were investigated in hearings at community centers. With reference to their comments, we proposed a three-phased scenario in which pre- / post-activities were considered as important factors of its product design of the DSU. We designed the DSU for better usability in the pre- / post-activities. Its basic function and mechanical properties were also investigated in experiments. According to the mechanical tests, the supporting torque was around 10% of the activation of TA in IC. In addition, the results of gait tests show reductions of ankle rotations by 17% and 11% in IC and SW, respectively, without significant increases of TA activations.

The ankle kinematic reference of normal gait pattern in Thai adults.

ObjectiveThis study was aimed to establish the reference values of ankle kinematics and factors associated with ankle kinematics of healthy Thai adults.MethodsA prospective cohort was conducted among healthy volunteers aged between 18 and 40 years and evaluated gait analysis between 2016 and 2020. After applying the modified Halen Hayes marker set, participants were assigned to walk 8–10 rounds with their preferred speed. Demographic data i.e., age, gender and body mass index (BMI) and ankle kinematics (varus-valgus, dorsiflexion-plantar flexion, foot progression, and ankle rotation) using motion analysis software were recorded and analyzed.Results98 volunteers (60 females and 38 males) aged 28.6 ± 5.4 years with body mass index 21.2 ± 2.0 kg/m2 were included. The average ranges of ankle kinematics entire gait cycle were varus-valgus −1.62 to 3.17 degrees, dorsiflexion-plantar flexion 0.67 to 14.52 degrees, foot progression −21.73 to −8.47 degrees, and ankle rotation 5.22 to 9.74 degrees. The ankle kinematic data in this study population was significantly different from the normal values supplied by OrthoTrak software of the motion analysis program, especially more ankle internal rotation at mid-stance (5.22 vs. −12.10 degrees) and terminal stance (5.48 vs. −10.74 degrees) with P < 0.001. Foot progression significantly exhibited more external rotation for 1.5 degrees on the right compared to the left side, and for 5 degrees more in males than females. One increment in age was significantly correlated with ankle internal rotation at mid-swing (coefficient 0.21 degrees, P = 0.039). BMI had no statistical association with ankle kinematics. Statistical parametric mapping for full-time series of angle assessments showed significantly different foot progression at initial contact and terminal stance between sides, and our ankle kinematics significantly differed from the reference values of the motion analysis program in all planes (P < 0.05).ConclusionThe reference of ankle kinematics of Thai adults was established and differences between sides and the normal values of the motion analysis program were identified. Advanced age was associated with ankle internal rotation, and male gender was related to external foot progression. Further studies are needed to define all-age group reference values.

Effect of knee joint weight change on knee function recovery and gait after total knee arthroplasty

BackgroundKnee osteoarthritis (KOA) is a common disease based on degenerative pathological changes. Total knee arthroplasty (TKA) is an effective treatment for end-stage of KOA. However, only volume adaptation can be achieved with current knee prostheses, and it is difficult to achieve weight adaptation. This study focused on the weight difference of knee joints and initially explored the impact of this change on knee joint functional recovery and gait changes in patients after surgery.MethodsFrom October 2015 to June 2019, patients who underwent primary unilateral TKA were enrolled in this prospective cohort study with the same brand of knee prostheses. General data were collected from patients who met the criteria. The resected bone and soft tissues were collected and weighed precisely during TKA, and multivariate regression analysis was used to determine the factors affecting the weight of the removed knee tissues. We compared the weight of excised tissues and the total weight of the knee prosthesis, and the weight difference was defined as the increased weight of the knee joint (IWKJ). All patients were evaluated by HSS score, gait analysis, and affected side knee X-ray at two weeks, three months, and the last follow-up after the operation. To further determine the influence of IWKJ on postoperative functional recovery, the relationship between IWKJ, HSS score, and gait analysis was analyzed by univariate regression.ResultsIn total, 210 patients were eventually included in observation. All patients underwent postoperative follow-up for no less than two years. Multiple regression analysis showed that the course of the disease, body weight, and kellgren-Larencen stage(K-L stage)of the affected knee joint were independent factors affecting the weight of the removed knee tissues and were positively correlated with it. Univariate analysis showed that IWKJ was negatively correlated with HSS score at two weeks and three months after the operation. In addition, the values of spatiotemporal parameters and knee rotation ROM were negatively correlated with IWKJ two weeks after surgery, while outside food load response was positively correlated with IWKJ. Cadence, knee rotation ROM, and Ankle rotation ROM were negatively correlated with IWKJ, while outside food was positively correlated with IWKJ three months after surgery. At the last follow-up, only the hip rotation ROM was positively correlated with IWKJ.ConclusionsAll Patients underwent TKA had varying degrees of increased knee weight. The increased weight was 298.98 ± 63.77 g. Patients' body weight, K-L staging, and disease duration are important factors that cause differences in resected knee tissue. Three months after the operation, the changes in knee joint weight had a negative correlation with the HSS score, which at the same time, it had varying degrees of linearity with gait parameters. However, the influence of weight diminished over time.

Effects of badminton insole design on stress distribution, displacement and bone rotation of ankle joint during single-leg landing: a finite element analysis

ABSTRACT Previous research has reported that up to 92% of injuries amongst badminton players consist of lower limb, whereby 35% of foot fractures occurred at the metatarsal bone. In sports, insoles are widely used to increase athletes’ performance and prevent many injuries. However, there is still a lack of badminton insole analysis and improvements. Therefore, this study aimed to biomechanically analyse three different insole designs. A validated and converged three-dimensional (3D) finite element model of ankle–foot complex was developed, which consisted of the skin, talus, calcaneus, navicular, three cuneiform, cuboid, five metatarsals and five phalanges. Three existing insoles from the market, (1) Yonex Active Pro Truactive, (2) Victor VT-XD 8 and (3) Li-Ning L6200LA, were scanned using a 3D scanner. For the analysis, single-leg landing was simulated. On the superior surface of the skin, 2.57 times of the bodyweight was axially applied, and the inferior surface of the outsole was fixed. The results showed that Insole 3 was the most optimum design to reduce peak stress on the metatarsals (3.807 MPa). In conclusion, the optimum design of Insole 3, based on the finite element analysis, could be a justification of athletes’ choices to prevent injury and other complications.

Prosthetic Ankle Design and Performance Evaluation by Experimental Gait Comparison

There are millions of persons in this world have been suffered from land mines or other accidental events which have caused amputations. The human body feet provide stability and balance when standing and moving. Amputation of a foot highly decrease the amputee’s ability to practice common activities such as walking. The main target of a prostheses of any kind is to improve or return function to a physically disabled person. Although, the rapid developing of alternative prostheses technology, unfortunately, it is still a far from inquiring quite functional prosthetic limb replacement. The present study was focused on design and manufacturing of a two degree of freedom ankle rotation, plantar flexion- dorsiflexion in sagittal plane and inversion - eversion in frontal plain so as to mimic the normal human gait and also to reduce the pain and stress in the residual limb. Most ankle parts were formed from aluminum alloy and assembled to a carbon fiber foot laminated foot. The gait analysis was performed by the amputee user case study for both his prosthetic foot and the designed foot at the same optional ground surface conditions. The user foot angles responses were: eversion 2.60, inversion 2.60, plantar 8.70, dorsi 5.30, in contrast, the designed foot angles were: eversion 9.50, inversion 9.80, plantar 10.20, dorsi 10.40. The achieved designed maximum rolling in frontal plane was 100 inversion- eversion angle and the maximum rolling in sagittal plane were 120, 180 for plantar and dorsi flexion angle respectively.

Age related progression of clinical measures and gait in ambulant children and youth with bilateral cerebral palsy without a history of surgical intervention

BackgroundAge related progression needs to be considered when assessing current status and treatment outcomes in cerebral palsy (CP). Research questionWhat is the association between age, gait kinematics and clinical measures in children with bilateral CP? MethodA retrospective database review was conducted. Subjects with bilateral CP with baseline and follow-up 3D gait analyses, but no history of intervening surgery were identified. Clinical and summary kinematic measures were examined for age related change using repeat measures correlation. Interactions with GMFCS classification and whether surgery was recommended were examined using robust linear regression. Timeseries kinematic data for baseline and most recent follow-up analyses were analysed using statistical parametric mapping. Results180 subjects were included. 75% of participants were classified as GMFCS I or II at baseline. Mean time to follow-up was 4.89 (2.8) years (range 1–15.9 years) with a mean age of 6.4 (2.4) at baseline and 11.3 (3.4) at final follow-up. 15.5% of subjects demonstrated an improvement in GMFCS classification while GDI remained stable. Age related progression was noted across many clinical measures with moderate correlations (r ≥ 0.5) noted for reduced popliteal angle, long lever hip abduction and internal hip rotation range. In gait, there was reduced hip extension in late stance (p < 0.001), increased knee flexion in mid-stance (p < 0.001), reduced peak knee flexion in swing (p < 0.001) and increased ankle dorsiflexion in stance (p < 0.001). In the coronal plane, there was reduced hip abduction in swing (p < 0.001). In the transverse plane, increased external rotation of the knee (p < 0.001) and reduced external ankle rotation were noted in early stance and through swing (p < 0.001). There were no changes in foot progression or hip rotation. SignificanceIndividuals with CP show age related progression of clinical and kinematic variables. Treatment can only be deemed successful if outcomes exceed or match these age-related changes.

Measurements and Analyses of Walk Using a Novel Rollator Equipped with a Rotatable Chest Pad

In recent years, different types of commercial rollators or gait-training devices have been widely used by elderly people, suffering from dementia, for their daily activities to avoid being bedridden. However, the effectiveness of most of these commercial devices has not been investigated thoroughly. In this study, a novel rollator with a freely rotating chest pad, integrated with two angular sensors and two load cells, was developed. Walk measurements were carried out on four young healthy subjects who performed walk tests using the developed rollator. To measure the motion of the lower limbs, two goniometers were attached to the exteriors of both the knees, and two more were attached to the exteriors of both the ankle joints of the subjects. The results of the pressing forces on the pad measured by the load cells, pad rotations, knee extensions, and ankle rotations were demonstrated. Frequency analyses were performed and correlation coefficients were computed for the obtained results. The relationship between the pad rotation and the motion of the lower limbs was investigated, and the effectiveness of the developed novel rollator in walk assistance was discussed.

Does treadmill workstation use affect user's kinematic gait symmetry?

The effects of treadmill workstation use on kinematic gait symmetry and computer work performance remain unclear. The purpose of this pilot study was to analyze the effects of treadmill workstation use on lower body motion symmetry while performing a typing task when compared to overground and treadmill walking. The lower body motion of ten healthy adults (6 males and 4 females) was recorded by a motion capture system. Hip, knee, and ankle joint rotations were computed and compared for each condition. Despite comparable lower body kinematic gait asymmetries across conditions, asymmetric knee flexion motions at early gait cycle were only found in treadmill workstation users (left knee significantly more flexed than the right one). This demonstrates that the interaction between walking and another task is dependent on the task cognitive content. Our findings suggest that lower body kinematic gait symmetry may be influenced by the use of treadmill workstations.

Three-dimensional gait analysis in children with recurrent idiopathic clubfoot undergoing complete tibialis anterior tendon transfer.

This study was aimed to evaluate the kinetics and kinematics of the foot and ankle using three-dimensional gait analysis in children with recurrent clubfoot treated with tibialis anterior tendon transfer (TATT). Three-dimensional gait analysis of 17 children with dynamic supination (24 feet; 12 males; mean age: 6.34 years) was performed pre- and post-TATT. Spatial, temporal and kinematic parameters, as well as the gait deviation index (GDI), were recorded for all patients. Moreover, to evaluate the severity of dynamic supination during walking, we also measured the angle between the plane of the foot and the X-axis during the swing phase (V-angle-S). The postoperative step length (38.95 ± 8.36 cm) and stride length (76.73 ± 15.92 cm) were significantly smaller than their preoperative values (40.68 ± 9.35 cm and 80.57 ± 17.51 cm; P = 0.0316 and P = 0.0028, respectively). The postoperative peak internal ankle rotation angle in the frontal plane (20.45° ± 14.44) was significantly lower than the preoperative value (25.93° ± 9.84; P = 0.029). The postoperative peak internal foot progression angle in the transverse plane (0.96° ± 5.83) was significantly lower than the preoperative value (4.34° ± 8.88; P = 0.026). However, both the peak ankle varus moment and GDI were not significantly different between the pre- and postoperative data. Postoperative V-angle-S values (28.55° ± 7.56) were reduced compared to their preoperative values (32.52° ± 6.53; P = 0.0094). TATT to the lateral cuneiform can correct dynamic supination in patients with a recurrent clubfoot; however, it has limited or no effects on hindfoot varus deformity. Level of evidence: Level III.

Sensitivity of a Subject-specific Ankle Sprain Simulation to Extrinsic Versus Intrinsic Biomechanical Factors.

Ankle sprains are the most common musculoskeletal injury in sport and military activity, despite existing prophylactic strategies. The purpose of this report was to develop a probabilistic simulation of lateral ankle sprains during single-limb drop landing, towards accelerating innovation in ankle sprain prevention. A deterministic, subject-specific musculoskeletal model was extended with automation and probabilistic distributions on sprain-related biomechanical factors. Probabilistic simulations were generated using traditional Monte Carlo techniques and the advanced mean value method, a more computationally-efficient approach. Predicted distributions of peak ankle joint rotations, velocities, and moments borne by supporting passive structures agreed favorably with the deterministic model and with reports of real sprain biomechanics. Parameter sensitivities identified that predictions were most strongly influenced by drop height, subtalar joint posture at contact, invertor/evertor co-activation, and passive ankle stiffness. The advanced mean value method predicted confidence bounds comparable to a 1000-trial Monte Carlo simulation, and required only 14 model evaluations and 4-min processing time. The extended probabilistic simulation may be useful to virtually test new prophylactic strategies for ankle sprains, and is made available for open-source use (https://simtk.org/projects/sprain-sim).

Biomechanical Gain in Joint Excursion from the Curvature of the Achilles Tendon: Role of the Geometrical Arrangement of Inflection Point, Center of Rotation, and Calcaneus.

The dorsal movement of the Achilles tendon during ankle rotation is restricted by anatomical obstructions. Previously, we demonstrated that the anatomical obstruction provides a gain (gainAT) in the proximal displacement of the calcaneus compared to the change in the Achilles tendon length. Here, we empirically validate and extend our previous modeling study by investigating the effects of a broad range of obstruction locations on gainAT. The largest gainAT could be achieved when the obstruction was located on the most ventral and distal sides within the physiological range of the Achilles tendon, irrespective of the ankle position.

Mind your step: predicting maximum ankle inversion during cutting movements in soccer

ABSTRACT The objective of this investigation was to identify parameters at initial contact that would predict the subsequent maximum ankle inversion angle during cutting movements. We conducted a secondary data analysis and calculated kinematics of 1,400 cuttings performed by 46 male soccer athletes. The movement task consisted of an approach run, followed by a pre-planned cutting movement. A linear mixed regression model was applied to predict the maximum ankle inversion angle during the first 100 ms of ground contact. The prediction was made based on six predictors that describe change-of-direction intensity and foot placement as found to be relevant in the literature. The model explained 62% of the variance of maximum ankle inversion angles. A change of the main predictors (foot rotation, cutting angle and initial ankle inversion) by 1 SD caused a reduction of the subsequent maximum ankle inversion angle by 2.6–4.4°. Regarding the intensity of a change-of-direction movement, cutting angle seems to have a higher influence on maximum ankle inversion angle than approach velocity. With respect to the individual foot positioning, the maximum ankle inversion angle can be reduced by increasing exorotation and eversion of the foot while shifting towards forefoot landing.

Ankle joint rotation and exerted moment during plantarflexion dependents on measuring- and fixation method.

We examined the effect of ankle joint fixation vs increased foot pressure (aiming to reduce dynamometer-subject elasticity (DSE)) on the exerted moment during plantarflexion contraction. We also examined the joint rotation in dependence of the measuring site (forefoot, rearfoot) and the foot condition (fixed, free). We hypothesized higher exerted moments due to reduced DSE compared to fixed condition and an effect of fixation on the joint rotation in dependence of the measuring site. Fourteen healthy individuals (28.7±6.9y) completed in randomized order maximal isometric plantarflexions in four different positions (0-3-6-9 cm) and two ankle joint conditions (fixed-free). Kinematics of the rear- and forefoot were obtained synchronously. We found higher moment in the fixed compared to the free condition at all positions. The maximum moment in the fixed condition did not differ at any position. At the fixed condition, the forefoot rotation did not differ at any position (~5°) while at free condition we observed a significant rotation reduction (form ~12 to ~5°). The rearfoot rotation did not differ between conditions at any position while a significant joint angle reduction was observed (~10 to ~6° and ~12 to ~6°; fixed-free respectively). The results indicate that with appropriate foot fixation the maximum moment can be achieved irrespective of the position. With the foot secured, the measuring site influences the rotational outcome. We suggest that for a minimization of the joint rotation a fixation and the forefoot-measuring site should be preferred. Additionally, for unconstrained foot kinematic observations both measuring sites can be obtained.