Biomechanics of the ankle

Long-term Stress Distribution Patterns Across the Ankle Joint in Soccer Players: A Computed Tomography Osteoabsorptiometry Study

Background:

The distribution pattern of subchondral bone density is considered to accurately reflect the stress distribution over a joint under long-term physiologic loading. The biomechanical characteristics of the surface of the ankle joint in soccer players can be determined by measuring this distribution pattern under long-term loading.

Purpose:

To evaluate the distribution of subchondral bone density across the ankle joint in soccer players and to determine the effects of soccer activities, including kicking motion, on the ankle joint surface under long-term loading conditions by computed tomography (CT) osteoabsorptiometry (CTOAM).

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

CT imaging data were obtained from both ankles of 10 soccer players (soccer group) and 10 nonathletic volunteers (control group). The distribution patterns of subchondral bone density across the articular surface of the ankle joints were assessed by CTOAM. Quantitative analysis was performed of the locations and percentages of high-density areas on the articular surface.

Results:

Stress distribution patterns over the ankle joint differed between the soccer players and controls. In the soccer players, the high-density areas were found in the anterior part of the distal tibia and proximal talus as well as the distal fibula. The percentages of high-density areas were greater in the soccer players compared with controls (P < .0001).

Conclusion:

Stress distribution over the articular surface of the ankle joint was affected by soccer activities. A high stress concentration was seen in soccer players in the anterior part of the tibia and talus and in the fibula; such excessive stress may lead to anterior impingement.

Back foot influence on dorsiflexion using three different positions of the weight bearing lunge test

OBJECTIVES

To determine whether back foot (BF) position influences dorsiflexion range of motion (DFROM) during three different positions of the weight bearing lunge test (WBLT).

DESIGN

Randomised, repeated measures design.

SETTING

Sports clubs.

PARTICIPANTS

52 athletes participating in cutting and pivoting sports.

MAIN OUTCOME MEASURES

DFROM was obtained using a WBLT in three different BF positions: BF heel in full contact with the floor, BF heel raised off the floor and BF was non weight bearing (NWB). All measurements were obtained using three methods: inclinometer at the tibial tuberosity, toe to wall distance and goniometer angle from the lateral malleolus to the fibula head. Differences between testing positions were determined using a repeated measures one-way ANOVA and reliability analysis was performed using the Intraclass Correlation Coefficient (ICC).

RESULTS

DFROM was statistically significantly different for all three positions of the WBLT for each measurement technique (P < .001). These results were associated with large effect sizes for all BF positions and measurement techniques. Reliability ICC values were excellent for all measurements (ICC 0.94-0.99).

CONCLUSIONS

Results show that DFROM differs depending upon the position of the BF during the WBLT. Further research is needed to establish the reproducibility of these three BF positions due to the variability observed.

A machine learning-based diagnostic model associated with knee osteoarthritis severity

Knee osteoarthritis (KOA) is characterized by pain and decreased gait function. We aimed to find KOA-related gait features based on patient reported outcome measures (PROMs) and develop regression models using machine learning algorithms to estimate KOA severity. The study included 375 volunteers with variable KOA grades. The severity of KOA was determined using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). WOMAC scores were used to classify disease severity into three groups. A total of 1087 features were extracted from the gait data. An ANOVA and student's t-test were performed and only features that were significant were selected for inclusion in the machine learning algorithm. Three WOMAC subscales (physical function, pain and stiffness) were further divided into three classes. An ANOVA was performed to determine which selected features were significantly related to the subscales. Both linear regression models and a random forest regression was used to estimate patient the WOMAC scores. Forty-three features were selected based on ANOVA and student's t-test results. The following number of features were selected from each joint: 12 from hip, 1 feature from pelvic, 17 features from knee, 9 features from ankle, 1 feature from foot, and 3 features from spatiotemporal parameters. A significance level of < 0.0001 and < 0.00003 was set for the ANOVA and t-test, respectively. The physical function, pain, and stiffness subscales were related to 41, 10, and 16 features, respectively. Linear regression models showed a correlation of 0.723 and the machine learning algorithm showed a correlation of 0.741. The severity of KOA was predicted by gait analysis features, which were incorporated to develop an objective estimation model for KOA severity. The identified features may serve as a tool to guide rehabilitation and progress assessments. In addition, the estimation model presented here suggests an approach for clinical application of gait analysis data for KOA evaluation.

Analysis of a Wearable Robotic System for Ankle Rehabilitation

As one of the most commonly injured joints of the human body, the ankle is often subject to sprains or fractures that require motion assistance to recover mobility. Whereas physiotherapists usually perform rehabilitation in one-on-one sessions with patients, several successful robotic rehabilitation solutions have been proposed in the last years. However, their design is usually bulky and requires the patient to sit or stand in a static position. A lightweight wearable device for ankle motion assistance, the CABLEankle, is here proposed for motion ankle exercising in rehabilitation and training. The CABLEankle is based on a cable-driven S-4SPS parallel architecture, which enables motion assistance over the large motion range of the human ankle in a walking gait. The proposed mechanism design is analyzed with kinematic and static models, and the force closure workspace of the mechanism is discussed with analytical results. Finally, the feasibility of the proposed design is investigated through numerical simulations over the ankle motion range as a characterization of the peculiar motion.

Multi-Directional Ankle Impedance During Standing Postures

In this study, we estimated the multi-directional ankle mechanical impedance in two degrees-of-freedom (DOF) during standing, and determined how the stiffness, damping, and inertia vary with ankle angle and ankle torque at different postures. Fifteen subjects stood on a vibrating instrumented platform in four stationary postures, while subjected to pulse train perturbations in both the sagittal and frontal planes of motion. The four stationary postures were selected to resemble stages within the stance phase of the gait cycle: including post-heel-strike during the loading response, mid-stance, post-mid-stance, and just before the heel rises from the ground in terminal-stance phase. In general, the ankle stiffness and damping increased in all directions as the foot COP moved forward, and more torque is generated in plantarflexion. Interestingly, the multi-directional ankle impedance during standing showed a similar shape and major tilt axes to the results of non-loaded scenarios. However, there were notable differences in the impedance amplitude when the ankle was not under bodyweight loading. Last, the stiffness during standing had similar amplitudes ranges to the time-varying ankle stiffness during the stance phase of dynamic walking estimated in previous studies. These results have implications on the design of new, less physically intense, biomechanics experiments aimed at people with neuromuscular disorders or other physical impairments who cannot complete a standard gait test.

Posterior Ankle Impingement and Flexor Hallucis Longus Pathology

Posterior ankle pain is a common complaint, and the potential causative pathologic processes are diverse. The constellation of these numerous etiologies has been collectively referred to as posterior ankle impingement syndrome. The pain associated with posterior ankle impingement is caused by bony or soft tissue impingement of the posterior ankle while in terminal plantar flexion. This condition is most frequently encountered in athletes who participate in sports that involve forceful, or repetitive, ankle plantar flexion. This article discusses the associated pathology, diagnosis, conservative treatment, and surgical techniques associated with flexor hallucis longus and posterior ankle impingement syndrome.

Bilateral Foot Orthoses Elicit Changes in Gait Kinematics of Adolescents with Down Syndrome with Flatfoot

Background: Subjects with Down Syndrome (DS) are characterized by specific physiological alterations, including musculoskeletal abnormalities. Flat Foot (FF), caused by hypotonia and ligament laxity, represents one of the most common disabling disorders in this population. Conservative treatments promote the use of orthopaedic insoles and plantar supports. The aim of this study was to evaluate the impact of Foot Orthoses (FOs) on the gait pattern of subjects with DS, assessing the biomechanical effects associated with their use. Methods: Twenty-nine subjects were screened under two conditions-walking barefoot (WB); with shoes and insoles (WSI), during three trials for each. Assessments were performed through the 3D gait analysis, using an optoelectronic system, force platforms, and video recording. Specifically, synthetic indices of gait kinematics, i.e., gait profile score (GPS) and gait variable score (GVS) were calculated and compared with Wilcoxon signed-rank test, to evaluate between-conditions. Results: Significant variations were found in GVS foot progression index, representative of foot rotation during walking, in adolescents only. Conclusions: Bilateral FOs has a positive immediate impact on gait quality in adolescents with DS, as confirmed by quantitative analysis. FOs prescription is an evidence-based early approach to slow down biomechanical abnormalities and prevent relative symptoms.

Naviculectomy for two ambulatory children with intractable congenital vertical talus: redefining the indications of an old technique

Congenital vertical talus is a rare and complex foot anomaly. Serial casting with or without minimally invasive surgery is a universal management strategy especially for children in the first year of life. Nevertheless, extensive surgical treatment of late-presenting, neglected and multiple operated children with congenital vertical talus may be required with guarded results. The results of naviculectomy as a more conservative intervention and directed exclusively at ambulatory children with intractable congenital vertical talus have not been reported. We present the radioclinical outcomes of two ambulatory children with intractable congenital vertical talus treated by naviculectomy/midtarsal resection and limited soft tissue release. One child had an isolated congenital vertical talus whereas the other had a non-isolated etiology. Generally, naviculectomy/midtarsal resection revealed a positive benefit-risk profile in children with intractably severe congenital vertical talus on the short-term. We reported favorable results in terms of foot appearance, function and radiology. We believe that a less invasive procedure like naviculectomy/midtarsal resection is an encouraging technique to investigate in children with intractable congenital vertical talus.

Relationship between foot posture index and weight bearing computed tomography 3D biometrics to define foot alignment

BACKGROUND

The Foot Posture Index (FPI) was originally validated only against two dimensional radiographic imaging at the time of its inception since weight bearing three dimensional (3D) imaging did not exist. This technology is now widely available but it is not known if the FPI will continue to correlate well against it.

RESEARCH QUESTION

How does the clinical assessment tool of FPI correlate against 3D biometrics of foot alignment assessed on weight bearing computerised tomography (WBCT)?

METHODS

The FPI and 3D biometrics of 66 feet in 33 patients presenting to a single foot and ankle unit were assessed by two observers independently. All measurements were assessed for intra-rater and inter-rater reliability, and the association between the clinically assessed FPI and radiologically assessed 3D biometrics was identified.

RESULTS

The FPI demonstrated excellent intra-rater and good inter-rater reliability. All 3D biometric measures demonstrated excellent intra-rater and inter-rater reliability. A strong and significant correlation was identified between the FPI and 3D biometrics overall although subgroup analysis revealed the strength of association dropped when the hindfoot had a valgus alignment.

SIGNIFICANCE

This study confirmed that the FPI is a valid tool for assessing foot position. However, correlation between the FPI and 3D biometrics fell in the valgus aligned hindfoot so caution must be used when the FPI is used for assessment in this population.

Design of a Variable Stiffness Pneumatic Ankle Prosthesis With Self-Recharging for Weightlifting Exercise

With advances in prosthetic technology, functional intent has extended past basic support toward providing increased dynamic ability for daily and athletic use. Addressing a disparity between universality and complexity in sport-grade and energy-storage-and-return (ESR) prostheses, this paper presents a pneumatic transtibial ankle prosthesis concept with semi-active control of ankle stiffness to adjust the prosthesis' properties for a wider range of gym exercises. Functional validation of the device falls under specific scenarios including the parallel back squat weightlifting exercise. The prosthesis features 30 deg sagittal ankle range of motion and provides wireless adjustment of static air pressure via a smartphone app to transition between the force and stiffness demands of walking and weightlifting. This pneumatic system includes a self-replenishing feature, providing a practical solution for the variable air pressure demands of athletics and everyday use. The mechanical, pneumatic, and control systems of the prosthesis are therefore described. Biomechanical tests including the back squat were conducted with one transtibial amputee subject. The resultant kinematic analysis validated the functional goals of the device, including an increased range of ankle rotation and variable stiffness across three different cylinder pressure settings. The kinetic profiles of the amputated leg and the natural leg also reveal an improvement in bilateral symmetry compared to a standard ESR prosthesis. This prosthesis concept has the potential to help persons with amputation participate in a wider range of activities, by improving the versatility of current ESR and sport prostheses.

End-stage Ankle Arthritis Treated by Ankle Arthrodesis with Screw Fixation Through the Transfibular Approach: A Retrospective Analysis

OBJECTIVE

To evaluate the clinical outcome of ankle arthrodesis with screw fixation through the transfibular approach for end-stage ankle arthritis.

METHODS

Data of 22 patients (28 ankles) with end-stage ankle arthritis admitted to the Department of Orthopedics and Surgery of the First Hospital of Jilin University from May 2015 to December 2018 were analyzed retrospectively. The study included 9 men and 13 women, with a mean age of 56.86 ± 11.27 years (range, 37-75 years). The mean duration of the disease was 11.36 ± 12.80 years (range, 3 months-50 years). A total of 16 patients had posttraumatic arthritis, 5 patients had osteoarthritis, and 1 patient had rheumatoid arthritis. There were 12 cases of the left ankle and 16 cases of the right ankle; 16 cases were unilateral and 6 were bilateral. The same surgical procedure was applied to all patients. Collected data included the operation time, intraoperative and postoperative blood loss, hospitalization time, bone union rate, time to bone union, and complications. The American Orthopedic Foot and Ankle Society (AOFAS) ankle hindfoot score and the visual analogue scale (VAS) were used to evaluate the preoperative status and the postoperative outcome at the last follow up.

RESULTS

The mean follow-up period was 26.14 ± 10.99 months. The mean operation time was 101.82 ± 33.33 min. The mean blood loss was 116.78 ± 68.86 mL during the procedure and 111.07 ± 52.18 mL after the procedure. The mean hospitalization time was 14.22 ± 5.42 days. Bone union of the ankle joint was achieved in all patients. The mean time to bone union was 14.83 ± 2.14 weeks. There was significant difference in the operation time between the patients undergoing unilateral and bilateral ankle arthrodesis. The AOFAS ankle hindfoot score increased from the preoperative value of 43.46 ± 4.39 points to 80.39 ± 5.37 points at the last follow up. During the same interval, the VAS score improved from 6.14 ± 0.80 points to 1.64 ± 0.73 points. The AOFAS ankle hindfoot score of patients who underwent unilateral ankle arthrodesis improved from the preoperative 43.19 ± 3.95 points to 81.75 ± 5.23 points at the last follow up, and the VAS score improved from 6.19 ± 0.83 points to 1.69 ± 0.70 points. The AOFAS ankle hindfoot score of patients undergoing bilateral ankle arthrodesis improved from the preoperative value of 43.83 ± 5.08 points to 78.67 ± 5.05 points at the last follow up, while the VAS score improved from 6.08 ± 0.82 points to 1.58 ± 0.79 points. There was significant difference in the maximum walking distance and walking on any surface between the patients undergoing unilateral and bilateral ankle arthrodesis. One patient developed superficial peroneal nerve palsy, which resolved within 1 year after the operation. In another patient, healing of the incision skin was delayed. During the follow-up period, none of the patients developed an infection of the incision or local skin necrosis; screw loosening, withdrawal, or breakage did not occur in any patient.

CONCLUSION

The ankle arthrodesis with screw fixation through the transfibular approach provides satisfactory clinical outcomes for end-stage ankle arthritis.

In vivo kinematics of fixed-bearing total ankle arthroplasty

BACKGROUND

A good recovery of the physiological mobility of the ankle is an indication of patients' satisfaction after total ankle arthroplasty, which does not generally match that of other consolidated procedures such as hip and knee replacement. The aim of this study was to investigate the kinematics of the Zimmer Total Metal Total Ankle (ZTMTA) during the different exercises.

METHODS

Fifteen patients with ZTMTA were enrolled in this study. The patients performed non-weightbearing flexion-extension, stair climbing and descending, and fluoroscopic images were taken to capture the ankle movements. A combined images/three-dimensional models method was used to perform a kinematic analysis.

RESULTS

Plantar-dorsiflexion resulted the main plane of movement, with the largest range of motion (ROM) of 23.3 ± 9.0° during flexion-extension. Inversion-eversion and adduction-abduction resulted lower than 10° in any trials.

CONCLUSIONS

In the investigated population, the ZTMTA allowed a good recovery of the mobility, with ROMs comparable to the healthy subjects.

Biomechanical Comparison of a New Dynamic Ankle Orthosis to a Standard Ankle-Foot Orthosis During Walking

Patients who sustain irreversible cartilage damage or joint instability from ankle injuries are likely to develop ankle osteoarthritis (OA). A dynamic ankle orthosis (DAO) was recently designed with the intent to offload the foot and ankle using a distractive force, allowing more natural sagittal and frontal plane ankle motion during gait. To evaluate its efficacy, this study compared ankle joint kinematics and plantar pressures among the DAO, standard double upright ankle-foot orthosis (DUAFO), and a nonorthosis control (CON) condition in healthy adults during walking. Ten healthy subjects (26 ± 3.8 yr; 69.6 ± 12.7 kg; and 1.69 ± 0.07 m) walked on a treadmill at 1.4 m/s in three orthosis conditions: CON, DAO, and DUAFO. Ankle kinematics were assessed using a three-dimensional (3D) motion capture system and in-shoe plantar pressures were measured for seven areas of the foot. DAO reduced hallux peak plantar pressures (PPs) compared to CON and DUAFO. PPs under toes 2-5 were smaller in DAO than DUAFO, but greater in DUAFO compared to CON. Early stance peak plantarflexion (PF) angular velocity was smaller in DAO compared to CON and DUAFO. Eversion (EV) ROM was much smaller in DUAFO compared to CON and DAO. Early stance peak eversion angular velocity was smaller in DAO and much smaller in DUAFO compared to CON. This study demonstrates the capacity of the DAO to provide offloading during ambulation without greatly affecting kinematic parameters including frontal plane ankle motion compared to CON. Future work will assess the effectiveness of the DAO in a clinical osteoarthritic population.

Morphometric geometric differences between right and left human tali: A cadaveric study of fluctuating asymmetry via systematic measurement and three-dimensional scanning

Background

Little is known about differences in the size and morphology of the right and left human tali. The present study demonstrates differences between right and left talar morphometric geometric profiles as fluctuating asymmetry in matched pairs of cadaveric specimens.

Methods

In total, 24 tali were collected in this study. All eligible tali were systematically measured with a Vernier caliper and three-dimensional laser scanner, which provided data for further analysis regarding the talar morphometric geometric profiles. Data were calculated to demonstrate differences between the right and left talar profiles using a matched-pair method, including the general size of the talus.

Results

The average talar length was 53.5 mm, the average talar dome height was 31.2 mm, and the average talar body width was 41.3 mm. The average anterior trochlear width, middle trochlear width, posterior trochlear width, and trochlear length were 31.8, 31.2, 28.3, and 30.7 mm, respectively. Eleven matched pairs of intact tali were eligible for the matched-pair study. Paired t-tests showed significant differences in the talar dome height (P = 0.019), middle trochlear width (P = 0.027), and posterior trochlear width (P = 0.016) between the right and left tali. However, there were no significant differences in the surface area or volume between the right and left tali.

Conclusion

Significant differences in the morphometric profile were found between the right and left matched pairs of tali. This basic information indicates that the profile of the contralateral talus may not be used as a single reference to reconstruct or duplicate the talus of interest in certain conditions such as talar prosthesis implantation or customized total ankle replacement.

Impact of Ankle-Foot Orthosis on Gait Efficiency in Ambulatory Children With Cerebral Palsy: A Systematic Review and Meta-analysis

OBJECTIVE

Children with cerebral palsy experience functional limitations because of excessive muscle weakness, spasticity, and impaired motor control. They are prescribed ankle-foot orthoses to assist with ambulation. Our objective was to analyze stride length and dorsiflexion data comparing the effectiveness of "ankle-foot orthoses" with "barefoot or shoes only" on ambulatory children with cerebral palsy.

DESIGN

An electronic literature search was conducted. Studies were screened by two reviewers based on our inclusion criteria: prospective cohort study or randomized clinical trial, participants younger than 18 yrs with a primary diagnosis of cerebral palsy, ankle-foot orthoses with a control group, 20 combined participants in the experimental and control groups for cohort studies, and 10 participants for randomized clinical trials.

RESULTS

Seventeen studies were selected. Pooled results of the meta-analyses showed that stride length was significantly better in the ankle-foot orthoses group as compared with the control group (mean difference between groups = 0.05 m (95% confidence interval = 0.04-0.06). The dorsiflexion angle (5 studies, 124 participants) was improved in patients with ankle-foot orthoses as compared with barefoot or shoes only (mean difference between groups = 8.62 degrees (95% confidence interval = 8.05-9.2).

CONCLUSIONS

Children with cerebral palsy using ankle-foot orthoses had improved stride length and dorsiflexion angle during gait in a pooled meta-analyses of cohort studies and clinical trials.

Analyzing Uncertainty of an Ankle Joint Model with Genetic Algorithm

Recent studies in biomechanical modeling suggest a paradigm shift, in which the parameters of biomechanical models would no longer treated as fixed values but as random variables with, often unknown, distributions. In turn, novel and efficient numerical methods will be required to handle such complicated modeling problems. The main aim of this study was to introduce and verify genetic algorithm for analyzing uncertainty in biomechanical modeling. The idea of the method was to encode two adversarial models within one decision variable vector. These structures would then be concurrently optimized with the objective being the maximization of the difference between their outputs. The approach, albeit expensive numerically, offered a general formulation of the uncertainty analysis, which did not constrain the search space. The second aim of the study was to apply the proposed procedure to analyze the uncertainty of an ankle joint model with 43 parameters and flexible links. The bounds on geometrical and material parameters of the model were set to 0.50 mm and 5.00% respectively. The results obtained from the analysis were unexpected. The two obtained adversarial structures were almost visually indistinguishable and differed up to 38.52% in their angular displacements.

The correlation between clinical and ultrasound evaluation of anterior talofibular ligament and calcaneofibular ligament tears in athletes

BACKGROUND

The objectives of this study were to find correlation between the clinical and ultrasound grading in anterior talofibular ligament and calcaneofibular ligament tear, and to determine the sensitivity and specificity of the two stability tests among the athletes. Subsequently, we would like to propose a new grading criterion for an ultrasound examination.

METHODS

Two blinded assessors examined thirty-five patients with a history of recent lateral ankle sprain. The first assessor performed physical examination on the injured ankle by using the anterior drawer test and talar tilt test, and the second assessor performed dynamic and static ultrasound assessment for anterior talofibular ligament and calcaneofibular ligament. The clinical laxity grading and sonographic extent of ligamentous injury was graded into a three-point scale.

RESULTS

There was a moderate positive correlation between clinical test and ultrasound grading of anterior talofibular ligament and calcaneofibular ligament with Spearman's correlation coefficient values of 0.58 and 0.66 respectively. Clinical grading of anterior drawer test had 59.1% sensitivity (95% CI: 0.36-0.79) while ultrasound grading had 100.0% specificity (95% CI: 0.75-1.00), with positive likelihood ratio of 0.77 and negative likelihood ratio of 0.44 in detecting a complete (grade 3) anterior talofibular ligament tear (P<0.05). Meanwhile, the clinical grading of talar tilt test had 54.5% sensitivity (95% CI: 0.23-0.83) and ultrasound grading had 100.0% specificity (95% CI: 0.85-1.00), with positive likelihood ratio of 1.0 and negative likelihood ratio of 0.45 in detecting a complete grade 3 calcaneofibular ligament tear (P<0.05).

CONCLUSIONS

The dynamic ultrasound is recommended to determine the actual degree of disruption of the ligament especially when clinical grading under-grades the degree of tear. Grade 2 tears can vary from 10% tear to 90% tear causing the clinical correlation to become less strong. We recommend a new classification for ultrasound grading of grade 2 tears, which could result in a stronger correlation between clinical and ultrasound grading.

Estimation of ankle joint parameters in typically developed adults using functional calibration methods

BACKGROUND

Despite of many attempts to determine or correct hip and knee joint parameters via non-invasive techniques such as regression or functional methods, in conventional gait models the position of the ankle joint center still is assumed at the center point between malleoli.

RESEARCH QUESTION

The aim of this study was to estimate the ankle joint parameters using a functional approach.

METHODS

To this aim, we used data of 23 typically developed adults performing two different calibration motions. Subsequently, we applied functional approaches to determine the functional joint center and axis.

RESULTS

The results show significant differences for ankle joint parameters in all directions for both calibration motions applied with respect to the malleoli line. Most prominently, we find a shift of the ankle joint center of 7 % of the foot length anteriorly to the malleoli mid-point when applying functional calibration.

CONCLUSION

These significant alterations of the ankle joint center and axis indicate the importance of accurate determination of ankle joint parameters and consequently their influence on the clinical outcome.

Novel passive ankle-foot prosthesis mimics able-bodied ankle angles and ground reaction forces

BACKGROUND

During gait, the human ankle both bends with ease and provides push-off forces that facilitate forward motion. The ankle is crucial for support, stabilization, and adapting to different slopes and terrains. Individuals with lower limb amputation require an ankle-foot prosthesis for basic mobility.

METHODS

Inspired by the role of the ankle-foot in an able-bodied gait, the 3D printed Compliant and Articulating Prosthetic Ankle (CAPA) foot was designed. It consists of four articulating components connected by torsion springs and produces forces that are dependent on the ankle angle. Using the Computer Assisted Rehabilitation Environment, able-bodied individuals walked wearing a prosthetic simulator with the Solid Ankle Cushioned Heel foot, Renegade® AT, and multiple versions of the CAPA. These versions test compliant vs. stiff, small vs. large rocker radius, and pretension vs. none. We hypothesized that the CAPA would have larger ankle range of motion, push-off forces, and braking forces.

FINDINGS

Compared to existing prostheses, the novel prosthesis exhibits greater and significantly different ankle range of motion and sagittal plane ground reaction forces than existing prostheses during gait. Nine out of ten individuals prefer the novel prosthesis to the existing prostheses, and there is a statistically significant difference in difficulty level ratings.

INTERPRETATION

By providing a personalizable and passive alternative to existing designs, the CAPA could improve the quality of life for the growing number of individuals living with limb loss in the United States and around the world.

Using an ankle robotic device for motor performance and motor learning evaluation

In this paper we performed the evaluation of ankle motor performance and motor learning during a goal-directed task, executed using the pediAnklebot robot. The protocol consisted of 3 phases (Familiarization, Adaptation, and Wash Out) repeated one time for each movement direction (plantarflexion, dorsiflexion, inversion, and eversion). During Familiarization and Wash out subjects performed goal-directed movements in unperturbed environment, whereas during Adaptation phase, a curl viscous force field was applied and it was randomly removed 10 times out of 200. Ankle motor performance was evaluated by means of a set of indices grouped into: accuracy, smoothness, temporal, and stopping indices. Learning Index was calculated to study the motor learning during the adaptation phase, which was subdivided into 5 temporal intervals (target sets). The outcomes related to the ankle motor performance highlighted that the best performance in terms of accuracy and smoothness of the trajectories was obtained in dorsiflexion movements in the sagittal plane, and in inversion rotations in the frontal plane. Differences between movement directions revealed an anisotropic behavior of the ankle joint. Results of the Learning index showed a capability of the subjects to rapidly adapt to a perturbed force field depending on the magnitude of the perceived field.

Ankle stability in ankle fracture

Restoration of normal ankle kinematics should be the all-encompassing ethos in the approach to management of ankle fractures. To do this, the ligamentous stabilisers must also form part of its assessment and definitive management and be considered during index fracture fixation surgery. This article is a review of the anatomy, mechanics and clinical testing of instability in ankle fractures.

Can foot angle influence the risk of injury to the lower limb joints during a field hockey hit?

Objectives

The lower limb is widely reported as the most commonly injured body part in the field of hockey, more specifically lateral ankle sprains and internal knee injury. Despite this, there remains limited understanding of how the biomechanics of the sport could be adapted to minimise injury. The aim of this study was to propose a foot position during the hockey hit that results in the smallest joint angles and moments, from a total of four different foot positions: 0°, 30°, 60° and 90°, which may correlate to injury risk.

Method

Eighteen players from the local University Ladies Hockey Club participated in this study. Each player was required to perform a hit with their lead foot in four different positions: 0°, 30°, 60° and 90°, where 0° was a lead foot position perpendicular to the direction of motion of the ball. Angles and moments were calculated with the Vicon system using force plates and motion analysis.

Results

Significant differences (p<0.05) were found between the angles and moments of the four foot positions tested, indicating that foot angle can influence the degree of angulation, and moments, produced in the lower limb joints during the hockey hit.

Conclusion

There is a relationship between lead foot position and the angles and moments produced in the lower limb joints during the hockey hit, and this may correlate with injury risk.

Comparison of Tibial and Talar Bone Density in Patients Undergoing Total Ankle Replacement vs Non-Ankle Arthritis Matched Controls

BACKGROUND

Bone quality in the distal tibia and talus is an important factor contributing to initial component stability in total ankle replacement (TAR). However, the effect of ankle arthritis on bone density in the tibia and talus remains unclear. The objective of this study was to compare bone density of tibia and talus in arthritic and nonarthritic ankles as a function of distance from ankle joint.

METHODS

We retrospectively reviewed 93 end-stage ankle arthritis patients who had preoperative nonweightbearing ankle computed tomography (CT) and identified a cohort of 83 nonarthritic ankle patients as a demographic-matched control group. A region of interest tool was used to calculate Hounsfield unit (HU) values in the cancellous region of the tibia and talus. Measurements were obtained on axial cut CTs from 6 to 12 mm above the tibial plafond, and 1 to 4 mm below the talar dome. HU measurements between groups and the decrease of HU at the relative level in each group were compared.

RESULTS

Arthritic ankles demonstrated significantly greater mean bone density than nonarthritic ankles at between 6 and 10 mm above the joint in the tibia (P < .05). No significant difference in bone density between 10 and 12 mm from the joint in the tibia nor at any level of the talus was found between groups. In both groups, bone density decreased significantly at each successive level away from the ankle joint.

CONCLUSION

Ankle arthritis patients demonstrated greater or equal bone density in both the tibia and talus compared to demographic-matched controls. In both groups, bone density decreased with increasing distance away from the articular surface. In TAR, tibial bone resection between 6 and 8 mm may provide improved initial implant stability.

LEVEL OF EVIDENCE

Level III, comparative study.

Inverse Relationship Between Radiographic Lateral Ankle Instability and Osteochondral Lesions of the Talus in Patients With Ankle Inversion Injuries

BACKGROUND

Insufficient or excessive bony constraint surrounding the talus might contribute to the occurrence of ligamentous injury or bone contusion, respectively, at the time of ankle inversion injuries. This study aimed to investigate the relationship between radiographic lateral ankle instability and osteochondral lesions of the talus (OLT) following ankle inversion injuries.

METHODS

A total of 195 patients (113 men and 83 women; mean age, 38.7 years) with a history of ankle inversion injuries were included in this study. All patients underwent ankle magnetic resonance imaging (MRI) and stress radiography. The tibiotalar tilt angle on varus stress radiograph, anterior translation of the talus on anterior-drawer lateral radiographs, bimalleolar tilt angle, and fibular position were radiographically determined. The radiographic lateral ankle instability was defined as tibiotalar tilt angle ≥10 degrees, and the presence of OLT was confirmed on MR images. The relationship between the radiographic lateral ankle instability and the presence of OLT was statistically analyzed.

RESULTS

The presence of radiographic lateral ankle instability (tibiotalar tilt angle ≥10 degrees) showed an inverse relationship with that of OLT in the chi-squared test (P = .003). An increased tibiotalar tilt angle was associated with lower incidence of OLT (P = .011) in the multiple regression analysis, and the presence of OLT was associated with a decreased tibiotalar tilt angle (P = .016) in the binary logistic regression analysis.

CONCLUSIONS

This study showed an inverse relationship between lateral ankle instability and the development of OLT following ankle inversion injury. The role of bony constraint in the development of sports injuries in the ankle should be considered with these injuries.

LEVEL OF EVIDENCE

Level III, diagnostic, comparative study.

Oxford foot model kinematics in landings: A comparison between professional dancers and non-dancers

OBJECTIVES

Dancers frequently perform jump-landing activities, with the foot-ankle complex playing an essential role to attenuate the landing forces. However, scarce research has been conducted in professional dancers multi-segmented foot in landings. The aim of this study was to compare the multi-segmented foot kinematics between professional dancers and non-dancers, during forward and lateral single-leg jump-landings.

DESIGN

Descriptive group comparison.

METHODS

Marker trajectories and synchronized ground reaction forces of 15 professional dancers and 15 non-dancers were collected using motion capture and a force plate, during multidirectional single-leg jump-landings. Sagittal and frontal hindfoot-tibia, forefoot-hindfoot, and hallux-forefoot kinematics of the multi-segmented foot model were computed at initial contact, peak vertical ground reaction force and peak knee flexion. Repeated measures ANOVAs were conducted (p < 0.05).

RESULTS

Professional dancers landed with higher hindfoot-tibia and forefoot-hindfoot plantarflexion angles at initial contact (p < 0.001), and hindfoot-tibia dorsiflexion angles at peak vertical ground reaction force and peak knee flexion (p < 0.001) than non-dancers. Also, dancers exhibited higher sagittal hindfoot-tibia and forefoot-hindfoot excursions than non-dancers (p < 0.001). No statistically significant differences were found in the frontal plane.

CONCLUSIONS

The multi-segmented foot allows a comprehensive kinematic analysis of the different foot joints. In jump-landings, professional dancers higher hindfoot-tibia, and forefoot-hindfoot plantarflexion at initial contact, compared to non-dancers, contributed to a subsequent higher foot joints excursion. This pattern is commonly linked to a better shock absorption mechanism in landings.

Foot modeling affects ankle sagittal plane kinematics during jump-landing

The foot-ankle complex is a key-element to mitigate impact forces during jump-landing activities. Biomechanical studies commonly model the foot as a single-segment, which can provide different ankle kinematics compared to a multi-segmented model. Also, it can neglect intersegmental kinematics of the foot-ankle joints, such as the hindfoot-tibia, forefoot-hindfoot, and hallux-forefoot joints, that are used during jump-landing activities. The purpose of this short communication was to compare ankle kinematics between a three- and single-segmented foot models, during forward and lateral single-leg jump-landings. Marker trajectories and synchronized ground reaction forces of 30 participants were collected using motion capture and a force plate, during multidirectional single-leg jump-landings. Ankle kinematics were computed using a three- (hindfoot-tibia) and a single-segmented (ankle) foot models, at initial contact (IC), peak vertical ground reaction force (PvGRF) and peak knee flexion (PKF). Repeated measures ANOVAs were conducted (p < 0.05). The findings of this study showed that during lateral and forward jump-landing directions, the three-segmented foot model exhibited lower hindfoot-tibia dorsiflexion angles (PvGRF and PKF, p < 0.001) and excursions (sagittal: p < 0.001; frontal: p < 0.05) during the weightbearing acceptance phase than the single-segmented model. Overall, the two foot models provided distinctive sagittal ankle kinematics, with lower magnitudes in the hindfoot-tibia of the three-segmented foot. Furthermore, the three-segmented foot model may provide additional and representative kinematic data of the ankle and foot joints, to better comprehend its function, particularly in populations whose foot-ankle complex plays an important role (e.g., dancers).

Analysis of three-dimensional computed tomography talar morphology in relation to pediatric pes planovalgus deformity

Intraosseous alignment of the tarsal bone has not been investigated in relation to various foot deformities. This study aimed to investigate three-dimensional computed tomography (3D CT) talar morphology in children with idiopathic and neuromuscular pes planovalgus. Eleven children [nine boys, two girls; mean (SD) age: 10.5 (2.8) years] with idiopathic pes planovalgus and 15 children [three boys, 12 girls; mean (SD) age: 10.8 (3.4) years] with neuromuscular pes planovalgus were included. All patients underwent 3D CT and weight-bearing anteroposterior, lateral, and axial radiography. Demographic data and talar 3D CT and radiographic measurements were compared between both groups. The correlation between the measurements was also analyzed. The neuromuscular group showed significantly more severe deformity than the idiopathic group in the radiographic and 3D sagittal talus measurements. The 3D coronal talus measurement showed a significant negative correlation with the axial hindfoot alignment in the idiopathic group while the 3D transverse talus measurement was significantly correlated with the lateral talocalcaneal angle in the neuromuscular group. 3D intraosseous alignment of the talus is correlated with pes planus deformity. Longitudinal and biomechanical studies including a control group are necessary to elucidate the role of 3D talar morphology on a dynamic imbalance in pes planovalgus.

Terrain Feature Estimation Method for a Lower Limb Exoskeleton Using Kinematic Analysis and Center of Pressure

While controlling a lower limb exoskeleton providing walking assistance to wearers, the walking terrain is an important factor that should be considered for meeting performance and safety requirements. Therefore, we developed a method to estimate the slope and elevation using the contact points between the limb exoskeleton and ground. We used the center of pressure as a contact point on the ground and calculated the location of the contact points on the walking terrain based on kinematic analysis of the exoskeleton. Then, a set of contact points collected from each step during walking was modeled as the plane that represents the surface of the walking terrain through the least-square method. Finally, by comparing the normal vectors of the modeled planes for each step, features of the walking terrain were estimated. We analyzed the estimation accuracy of the proposed method through experiments on level ground, stairs, and a ramp. Classification using the estimated features showed recognition accuracy higher than 95% for all experimental motions. The proposed method approximately analyzed the movement of the exoskeleton on various terrains even though no prior information on the walking terrain was provided. The method can enable exoskeleton systems to actively assist walking in various environments.

Alterations in tibiotalar joint reaction force following syndesmotic injury are restored with static syndesmotic fixation

INTRODUCTION

Syndesmotic injury alters joint mechanics, which may fail to be restored unless an anatomic reduction is obtained.

METHODS

A minimally invasive method of measuring joint forces was utilized that does not require significant dissection or intraarticular placement of sensory instruments. Steinmann pins were placed in the tibia and talus of eight fresh-frozen human cadaveric lower extremities and a baseline joint reaction force was determined. A syndesmotic injury was created and reduction (anatomic and anterior malreduction) performed with one or two quadricortical screws and joint reaction forces were measured after the injury and subsequent repairs.

FINDINGS

Baseline mean tibiotalar joint reaction force was 31.4 (SD 7.3 N) and syndesmotic injury resulted in a 35% decrease (mean 20.3, SD 8.4 N, p < 0.01). Fixation of the injury using one or two syndesmotic screws resulted in significant increase compared to the injury state (mean 28.7, SD3.9 N, and mean 28.3, SD 6.4 N, p < 0.05), however there was no significant difference between the two methods of fixation. Malreduction of the fibula also increased joint reaction force compared to the injury state (mean 31.5, SD 5.2 N, p < 0.01), however a significant difference was not detected between malreduction and anatomic reduction.

INTERPRETATION

The present study demonstrates that syndesmotic injury decreases joint reaction force within the tibiotalar joint, suggesting ankle joint instability. Tibiotalar force was restored with anatomic reduction with either a 1 or 2 quadricortical syndesmotic screws. Furthermore, anterior malreduction restored joint reaction force to levels similar to those observed at baseline and with anatomic reduction.

LEVEL OF EVIDENCE

Level V: biomechanical/cadaver study.

Effect of ball position on the risk of injury to the lower limb joints during the hockey sweep pass in women

Objectives

This study aimed to determine if ball position influences the risk of lower limb non-contact injury in hockey sweep pass. It also aimed to determine a ball position that minimises excessive strain placed on the lower limb joints of the lead leg during the sweep pass.

Methods

A cohort of 18 female hockey-playing volunteers (age: 19.7±1.5 years; height: 165.5±5.4 cm; body mass: 66.4±7.0 kg) were recruited. Participants performed the sweep pass using three different ball positions: in front, in line with, and behind the heel of the lead (left) foot.

Motion analysis and force plate data were collected. Moments and angles in all three planes of motion for the three main lower limb joints were then calculated using Vicon software. Results were statistically analysed using SPSS software.

Results

Significant differences (p<0.05) were found between the three tested ball positions for the mean maximum angles and moments, and mean ranges of motion produced at the lead three main lower limb joints. Positioning the ball in line with the heel of the lead foot resulted in the lowest moments and angles when compared with the other two ball positions.

Conclusions

The results indicate that positioning the ball in line with the heel of the lead foot is recommended to minimise the risk of injury to the lower limb joints during the hockey sweep pass. It is hoped that these findings will result in this position being implemented by players new to hockey or those returning to the sport following injury.

Total ankle arthroplasty and ankle arthrodesis affect the biomechanics of the inner foot differently

Ankle arthrodesis and total ankle arthroplasty are the two primary surgeries for treatment of end-stage degenerative ankle arthritis. The biomechanical effects of them on the inner foot are insufficient to identify which is superior. This study compared biomechanical parameters among a foot treated by ankle arthrodesis, a foot treated by total ankle arthroplasty, and an intact foot using computational analysis. Validated finite element models of the three feet were developed and used to simulate the stance phase of gait. The results showed total ankle arthroplasty provides a more stable plantar pressure distribution than ankle arthrodesis. The highest contact pressure, 3.17 MPa, occurred in the medial cuneonavicular joint in the total ankle arthroplasty foot. Neither of the surgeries resulted in contact pressure increase in the subtalar joint. The peak stress in the metatarsal bones was increased in both surgical models, especially the second and third metatarsals. This study enables us to get visual to the biomechanics inside of an intact foot, and feet treated by total ankle arthroplasty and ankle arthrodesis during walking.

Anticipatory muscle responses in transitions from rigid to compliant surfaces: towards smart ankle-foot prostheses

Locomotion is paramount in enabling human beings to effectively respond in space and time to meet different needs. There are 2 million Americans living with an amputation and the majority of those amputations are of the lower limbs. Although current powered prostheses can accommodate walking, and in some cases running, basic functions like hiking or walking on various non-rigid or dynamic terrains are requirements that have yet to be met. This paper focuses on the mechanisms involved during human locomotion, while transitioning from rigid to compliant surfaces such as from pavement to sand, grass or granular media. Utilizing a unique tool, the Variable Stiffness Treadmill (VST), as the platform for human locomotion, rigid to compliant surface transitions are simulated. The analysis of muscular activation during the transition from rigid to compliant surfaces reveals specific anticipatory muscle activation that precedes stepping on the compliant surface. These results are novel and important since the evoked activation changes can be used for altering the powered prosthesis control parameters to adapt to the new surface, and therefore result in significantly increased robustness for smart powered lower limb prostheses.

Autism and toe-walking: are they related? Trends and treatment patterns between 2005 and 2016

PURPOSE

This study quantified toe-walking trends and treatment decisions in patients with autism spectrum disorder (ASD) in the United States between 2005 and 2016 using a large national private-payer database.

METHODS

A retrospective database review was performed on paediatric patients with ASD, and for International Classification of Diseases-9/10 diagnosis codes for toe-walking. Patients were filtered based on treatment type by Current Procedural Terminology (CPT) code. Continued toe-walking rates were assessed for each patient population and treatment group. A Pearson's chi-squared test was used to evaluate differences in group characteristics.

RESULTS

Of 2 221 009 paediatric patients in the database, 5739 patients had a diagnosis of ASD, and 8.4% of patients with ASD also had a diagnosis of toe-walking (n = 484). For typically developing children in the database, 0.47% of patients had a diagnosis of persistent toe-walking. In all, 59.3% of ASD patients underwent physical therapy, 7.4% serial casting and 3.3% surgical correction, compared with 38.1%, 3.6% and 1.2% of normally developing children, respectively (chi-square 6.4031; p < 0.040699). Without intervention, 63.6% of patients with ASD continued to toe-walk within ten years of their diagnosis, with 19.3% of patients without ASD (chi-square 82.9762; p < 0.0001).

CONCLUSION

This study supports the association between a greater prevalence of toe-walking in children with ASD. We showed that patients with ASD and toe-walking receive surgical correction at nearly triple the rate of children without ASD who toe-walk. The continued rate of toe-walking is comparable between treatment groups as well as between ASD and typically developing children. Typically developing children have higher rates of toe-walking resolution without intervention than children with ASD.

LEVEL OF EVIDENCE

Level II.

The Effect of Ankle Support on Lower Limb Kinematics During the Y-Balance Test Using Non-linear Dynamic Measures

Background: According to dynamical systems theory, an increase in movement variability leads to greater adaptability, which may be related to the number of feedforward and feedback mechanisms associated with movement and postural control. Using Higuchi dimension (HDf) to measure complexity of the signal and Singular Value Decomposition Entropy (SvdEn) to measure the number of attributes required to describe the biosignal, the purpose of this study was to determine the effect of kinesiology and strapping tape on center of pressure dynamics, myoelectric muscle activity, and joint angle during the Y balance test.

Method: Forty-one participants between 18 and 34 years of age completed five trials of the Y balance test without tape, with strapping tape (ST), and with kinesiology tape (KT) in a cross-sectional study. The mean and standard errors were calculated for the center of pressure, joint angles, and muscle activities with no tape, ST, and KT. The results were analyzed with a repeated measures ANOVA model (P_A < 0.05) fit and followed by Tukey post hoc analysis from the R package with probability set at P < 0.05.

Results: SvdEn indicated significantly decreased complexity in the anterior-posterior (p < 0.05) and internal-external rotation (p < 0.001) direction of the ankle, whilst HDf for both ST and KT identified a significant increase in ankle dynamics when compared to no tape (p < 0.0001) in the mediolateral direction. Taping also resulted in a significant difference in gastrocnemius muscle myoelectric muscle activity between ST and KT (p = 0.047).

Conclusion: Complexity of ankle joint dynamics increased in the sagittal plane of movement with no significant changes in the possible number of physiological attributes. In contrast, the number of possible physiological attributes contributing to ankle movement was significantly lower in the frontal and transverse planes. Simply adhering tape to the skin is sufficient to influence neurological control and adaptability of movement. In addition, adaptation of ankle joint dynamics to retain postural stability during a Y Balance test is achieved differently depending on the direction of movement.

The Ankle-Joint Complex: A Kinesiologic Approach to Lateral Ankle Sprains

Copious research exists regarding ankle instability, yet lateral ankle sprains (LASs) persist in being among the most common recurrent musculoskeletal injuries. Key anatomical structures of the ankle include a triform articulating structure that includes the inferior tibiofibular, talocrural, and subtalar joints. Functionally, force absorption and propulsion through the ankle complex are necessary for any task that occurs in weight bearing. For optimal ankle performance and avoidance of injury, an intricate balance between stability and mobility is necessary to ensure that appropriate force transfer occurs during sports and activities of daily living. Consideration for the many structures that may be directly or indirectly involved in LASs will likely translate into advancements in clinical care. In this clinical review, we present the structure, function, and relevant pathologic states of the ankle complex to stimulate a better understanding of the prevention, evaluation, and treatment of LASs.

Adverse Events and Their Risk Factors Following Intra-articular Corticosteroid Injections of the Ankle or Subtalar Joint

BACKGROUND

Little data exists regarding the incidence of adverse events and their associated risk factors following intra-articular corticosteroid injection of the ankle and subtalar joint. The aim of this study was to determine the complication rate associated with such injections and to identify any predictive risk factors.

METHODS

Adult patients who had received an intra-articular ankle or subtalar joint injection between January 2000 and April 2016 at one of 3 regional hospitals (2 level 1 trauma centers and 1 community hospital) were included. Patients with prior intra-articular injection of corticosteroid into the ankle or subtalar joint were excluded. Explanatory variables were sex, age, race, body mass index, diabetes status, tobacco use, presence of fluoroscopic guidance, location of intra-articular injection, and administering physician's years of experience.

RESULTS

Of the 1708 patients included in the final cohort, 99 patients (5.8%) had a total of 104 adverse events within 90 days postinjection. The most prevalent types of adverse events were postinjection flare in 78 patients (4.6% of total cohort, 75% of adverse events) followed by skin reaction in 10 patients (0.6% of total cohort, 9% of adverse events). No infections were noted. Multivariable logistic regression analysis found that intra-articular injection in the subtalar ( P = .004) was independently associated with development of an adverse event. Fluoroscopic guidance was not found to be protective of an adverse event compared to nonguided injections ( P = .476).

CONCLUSION

The adverse event rate following intra-articular ankle or subtalar joint corticosteroid injection was 5.8%, with postinjection flare being the most common complication. Infections following injection were not reported. Injection into the subtalar joint was independently associated with the development of an adverse event after intra-articular corticosteroid injection, and this was not mitigated by the use of fluoroscopic guidance.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Ankle strength, muscle size, and adipose content following unilateral tibiotalar arthrodesis

Tibiotalar arthrodesis is commonly used to treat end-stage ankle osteoarthritis. Post-operative impairments are often attributed to limited ankle motion. However, whether muscular deficits also exist, thereby potentially contributing to impairments, is unknown. This study aimed to identify post-operative deficits in ankle musculature by examining range of motion, strength (maximum isometric ankle joint torque), and leg composition (cross-sectional area of individual tissue types: bone, subcutaneous adipose, intramuscular adipose, muscle). Ten individuals with unilateral tibiotalar arthrodesis participated. Paired t-tests (p < 0.05) identified differences between the fused and contralateral, control limb. The results indicate that individuals with tibiotalar arthrodesis have profound losses of range of motion and strength. Across participants, range of motion in the fused limb was 53.5 ± 11.7%, 66.8 ± 6.3%, 38.2 ± 18.7%, 37.8 ± 13.6% less than the control for dorsiflexion, plantarflexion, inversion, and eversion, respectively. The largest strength deficit was in dorsiflexion, with the fused limb producing 47.2 ± 9.4% less torque than the control. The quantity and quality of muscle tissue was also negatively affected in individuals following tibiotalar arthrodesis. The total cross-sectional area of the fused limb was 11.4 ± 5.4% smaller than the control limb. This change was primarily due to the 16.1 ± 6.7% decrease in muscle cross-sectional area. However, intramuscular adipose was significantly increased. Although the posterior compartment demonstrated a significant decrease in cross-sectional area, when accounting for differences in total cross-sectional area, the relative sizes of the four muscle compartments were consistent between limbs. This cross-sectional study motivates longitudinal research examining muscular deficits and whether these deficits are reversible with exercise and rehabilitation. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Ankle Joint and Rearfoot Biomechanics During Toe-In and Toe-Out Walking in People With Medial Compartment Knee Osteoarthritis

BACKGROUND

Toe-in and toe-out walking are 2 strategies that have been shown to be effective in reducing the knee adduction moment in people with knee osteoarthritis. However, despite a positive biomechanical impact on the knee, altering foot rotation may impart unintended forces or joint positions on the ankle that could impact joint health. The kinematic and kinetic changes at the ankle during toe-in or toe-out walking have yet to be examined.

OBJECTIVE

To examine ankle/rearfoot biomechanics during toe-in and toe-out walking in those with knee osteoarthritis.

DESIGN

Single-session repeated measures design to compare ankle biomechanics during walking with 4 different foot rotations.

SETTING

University motion analysis laboratory.

PARTICIPANTS

A convenience sample (N = 15) of males and females with a diagnosis of medial knee osteoarthritis confirmed by radiographs.

METHODS

Participants walked in 4 conditions guided by real-time biofeedback: (1) toe-in (+10°), (2) zero rotation (0°), (3) toe-out (-10°), and (4) toe-out (-20°). Ankle and rearfoot kinematics and kinetics were examined during barefoot over-ground walking.

MAIN OUTCOME MEASURES

Ankle joint angles, moments, moment impulses, and foot rotation.

RESULTS

Overall, toe-in compared to toe-out walking decreased (P = .03) peak rearfoot eversion (toe-in = -1.6°; 10° toe-out = -3.7°; 20° toe-out = -4.1°). Toe-in compared to toe-out walking also increased rearfoot inversion at initial contact (7.4° vs 3.1° at 10° toe-out and 1.9° at 20° toe-out; P < .001) and frontal plane rearfoot angle excursion (9.0° vs 6.8° at 10° toe-out and 6.0° at 20° toe-out; P < .006). Toe-in compared to all other conditions increased peak external ankle inversion moments (0.04 Nm/kg vs 0.02 Nm/kg at 0°, 0.02 Nm/kg at 10° toe-out, and 0.01 Nm/kg at 20° toe-out; P < .003).

CONCLUSIONS

Toe-in and toe-out walking require different ankle/rearfoot biomechanics, though no differences in discomfort were observed. Longer-term studies are required to properly assess these relationships in knee osteoarthritis populations.

LEVEL OF EVIDENCE

IV.

Proportional Joint-Moment Control for Instantaneously Adaptive Ankle Exoskeleton Assistance

Lower-limb exoskeletons used to improve free-living mobility for individuals with neuromuscular impairment must be controlled to prescribe assistance that adapts to the diverse locomotor conditions encountered during daily life, including walking at different speeds and across varied terrain. The goal of this paper is to design and establish clinical feasibility of an ankle exoskeleton control strategy that instantly and appropriately adjusts assistance to the changing biomechanical demand during variable walking. To accomplish this goal, we developed a proportional joint-moment control strategy that prescribes assistance as a function of the instantaneous estimate of the ankle joint moment and conducted a laboratory-based feasibility study. Four individuals with neuromotor impairment and one unimpaired individual completed exoskeleton-assisted slow and fast gait transition tasks that involved gait initiation and changing walking speed. We found that the controller was effective in instantaneously prescribing exoskeleton assistance that was proportional to the ankle moment with less than 14% root-mean-square error, on average. We also performed a three-subject pilot investigation to determine the ability of the proportional joint-moment controller to improve walking economy. Evaluated in two individuals with cerebral palsy and one unimpaired individual, metabolic cost of transport improved 17-27% during treadmill and over-ground walking with proportional control compared with wearing the exoskeleton unassisted. These preliminary findings support the continued investigation of proportional joint-moment control for assisting individuals with neuromuscular disabilities during walking in real-world settings.

Function of ankle ligaments for subtalar and talocrural joint stability during an inversion movement - an in vitro study

Background

The lateral ankle ligament complex consisting of the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL) and the posterior talofibular ligament (PTFL) is known to provide stability against ankle joint inversion. As injuries of the ankle joint have been reported at a wide range of plantarflexion/dorsiflexion angles, the aim of the present study was to evaluate the stabilizing function of these ligaments depending on the sagittal plane positioning of the ankle joint.

Methods

Eight fresh-frozen specimens were tested on a custom-built ankle deflection tester allowing the application of inversion torques in various plantarflexion/dorsiflexion positions. A motion capture system recorded kinematic data from the talus, calcaneus and fibula with bone-pin markers during inversion movements at 10° of dorsiflexion, at neutral position and at plantarflexion 10°. ATFL, CFL and PTFL were separately but sequentially sectioned in order to assess the contribution of the individual ligament with regard to ankle joint stability.

Results

Joint- and position-specific modulations could be observed when the ligaments were cut. Cutting the ATFL did not lead to any observable alterations in ankle inversion angle at a given torque. But subsequently cutting the CFL increased the inversion angle of the talocrural joint in the 10° plantarflexed position, and significantly increased the inversion angle of the subtalar joint in the 10° dorsiflexed position. Sectioning of the PTFL led to minor increases of inversion angles in both joints.

Conclusions

The CFL is the primary ligamentous stabilizer of the ankle joint against a forced inversion. Its functioning depends greatly on the plantar−/dorsiflexion position of the ankle joint complex, as it provides the stability of the talocrural joint primarily during plantarflexion and the stability of the subtalar joint primarily during dorsiflexion.

Electronic supplementary material

The online version of this article (10.1186/s13047-019-0330-5) contains supplementary material, which is available to authorized users.

Recurrence dynamics reveals differential control strategies to maintain balance on sloped surfaces

BACKGROUND

Studies on postural control have primarily focused on the maintenance of balance in quiet upright standing on flat horizontal support surfaces that can reveal only a subset of the potential postural stability/instability configurations in everyday contexts.

OBJECTIVES

Here we investigated the nature of dynamical properties of postural coordination in an upright standing task as a function of the systematic scaling of seven support surface angles, +20°, +10° dorsiflexion (+), 0 °Flat, -10°, -20°, -30°, -35° plantarflexion (-), mounted on a force plate.

METHODS

The center of pressure (CoP) and virtual time-to-contact (VTC) were analyzed to examine the spatial and spatio-temporal aspects of postural coordination dynamics, respectively. Recurrence quantification analysis (RQA) was used to characterize the dynamic postural control strategies as a function of slope surface angle.

RESULTS

The recurrence findings showed that on a flat surface the postural CoP dynamic are recurrent with a largely deterministic process and higher Shannon entropy compared to elevated slope angles in dorsiflexion and plantarflexion. There were asymmetrical patterns between similar slope angles for dorsiflexion and plantarflexion postures. The recurrence measures revealed that VTC operates on a higher embedding dimension than that of CoP.

SIGNIFICANCE

VTC showed an enhanced sensitivity to detection of postural instability in relation to the stability boundary that was magnified on the flat surface but progressively reduced over larger surface angles for both the dorsiflexion and plantarflexion postures.

Kinematics reduction applied to the comparison of highly-pronated, normal and highly-supinated feet during walking

BACKGROUND

Kinematic analysis could help to study how variations in the static foot posture affect lower limb biomechanical function. The analysis of foot kinematics is complex because it involves managing the time-dependent joint angles in different joints and in all three planes of motion. But it could be simplified if joint angles are coordinated.

METHODS

The kinematics of the ankle, midtarsal and metatarsophalangeal joints were registered in 20 highly-pronated, 30 normal and 20 highly-supinated subjects (assessed by the Foot Posture Index - FPI) as they walked barefoot. Coordination for each sample was analysed through principal component analysis applied to the dorsiflexion, abduction and inversion angles measured. Finally, a systematic comparison among the samples was performed through a set of ANOVAs applied to the reduced variables corresponding to the factors found.

RESULTS

Three principal components (coordination patterns) accounted for about 70% of the variance of the joint angles, and were affected by the FPI. The main coordination in normal feet was the supination movement, while in highly-supinated and highly-pronated feet it was the flexion coordination of all foot joints, which could work against adaptation in cases of varying terrain. The original joint angles were reduced to three factors, and the ANOVAs applied to them showed that highly-pronated feet presented a delayed propulsion peak and smaller ranges of motion during propulsion regarding all factors, and that highly-supinated feet require more pronation time to fully support the foot during walking.

SIGNIFICANCE

The coordination patterns of normal feet might be considered the normal patterns used for an efficient gait, and may help in planning surgical procedures and designing foot prostheses or orthotics. Dimensional reduction makes it possible to perform more systematic kinematic analyses, which have revealed that highly-pronated feet are in poorer propulsive condition, and this in turn may make them more prone to injury.

Objectively Assessed Foot and Ankle Characteristics in Patients With Systemic Lupus Erythematosus: A Comparison With Age- and Sex-Matched Controls

OBJECTIVE

To objectively identify foot and ankle characteristics in patients with systemic lupus erythematosus (SLE) compared to age- and sex-matched controls.

METHODS

A total of 54 patients with SLE and 56 control participants attended a study visit designed to comprehensively assess the foot and ankle. Objectively assessed foot characteristics included muscle strength, joint motion, foot posture, foot problems, protective sensation, vibration perception threshold (VPT), ankle brachial index (ABI), plantar pressure, and spatiotemporal gait characteristics. Self-reported measure of foot pain and impairment were also assessed using a 100-mm foot pain visual analog scale. Data were analyzed using regression models. Plantar pressure and gait models were adjusted for walking velocity, body mass index, and foot pain.

RESULTS

Compared to controls, participants with SLE had lower muscle force for plantarflexion, dorsiflexion, inversion, and eversion (all P < 0.001), higher foot posture indices (P = 0.007), higher foot problem scores (P = 0.001), higher VPT (P = 0.001), and more frequent abnormal ABI (odds ratio [OR] 3.13, P = 0.044). Participants with SLE also had lower peak pressure and higher pressure time integrals for all foot regions (all P < 0.001), lower step and stride length, velocity, and cadence, and higher step, swing, stance, and single and double support times compared to controls (all P < 0.001). Compared to controls, participants with SLE also reported greater foot pain (P < 0.001).

CONCLUSION

Patients with SLE experience a wide range of foot symptoms. This study has provided objective evidence of foot and ankle disease in patients with SLE, including reduced muscle strength and altered gait patterns when compared to controls. This highlights the importance of foot health assessments as part of SLE management.

3D Printed Total Talar Replacement: A Promising Treatment Option for Advanced Arthritis, Avascular Osteonecrosis, and Osteomyelitis of the Ankle

Advanced ankle arthritis, avascular osteonecrosis, and osteomyelitis of the ankle remain a surgical challenge in the foot and ankle arena with limited treatment options. Multiple medical comorbidities contribute to total loss of the talus. Collapse of the talar body as a complication of total ankle arthroplasty, talectomy in infection, and septic talus necrosis or severe bone defects caused by tumor resection may result in need for total talar replacement. Ankle arthrodesis and tibiocalcaneal fusion after talectomy can produce severe disability of the ankle and foot. Total ankle replacement is a viable option for treatment of end-stage ankle arthritis in appropriate patient populations.

Peroneal muscle activity during different types of walking

BACKGROUND

As the most common form of movement, walking happens not only on flat but also on uneven surfaces, where constant loss and regaining of balance occur. The main balancing function of the ankle joint is performed by tibial muscles. When changing inclination in a frontal plane, an essential balancing function is performed by the peroneal muscles. One of the methods for improving the activity of peroneal muscles is walking with different foot placement. The objective of this study was to analyze the activity of the peroneal muscles when performing different types of walking.

METHODS

Sixteen healthy participants took part in this study, walking on a flat surface (NORM), on a medial incline ramp with the plantar surface of the foot fully placed on the surface (FULL), and on a medial incline ramp with elevated lateral part of the foot (LAT). We monitored the changes of EMG signals in peroneus longus (PL), peroneus brevis (PB), tibialis anterior (TA), soleus (SOL), gastrocnemius medialis (GM) and gastrocnemius lateralis (GL) muscles. We monitored kinematic parameters (gait speed, stride length, contact time, foot position). The parametric ANOVA test and a non-parametric Friedman test were used at an alpha level of 0.05.

RESULTS

This study shows that the EMG activities of peroneal muscles increases when walking on the medial incline ramp. Statistically significant EMG differences were observed in the peroneal muscles, TA and GL muscles. We observe a very high percentage of normalized EMG value of the PL muscle in LAT walking. Walking on a medial incline ramp impacts the foot position, contact time, and stride length but not the gait speed.

CONCLUSIONS

Walking on a medial incline ramp could be an effective exercise to improve the neuro-muscular function of the peroneal muscles and, therefore, might be a suitable exercise for people with weakened ankle evertors.