Ankle Stiffness Research Articles

How Does Ankle Mechanical Stiffness Change as a Function of Muscle Activation in Standing and During the Late Stance of Walking?

Ankle joint stiffness is known to be modulated by co-contraction of the ankle muscles; however, it is unclear to what extent changes in agonist muscle activation alone affect ankle joint stiffness. This study tested the effects of varying levels of ankle muscle activation on ankle joint mechanical stiffness in standing and during the late stance phase of walking. Dorsiflexion perturbations were applied at various levels of ankle muscle activation via a robotic platform in standing and walking conditions. In standing, muscle activation was modulated by having participants perform an EMG target matching task that required varying levels of plantarflexor activation. In walking, muscle activation was modulated by changing walking speeds through metronome-based auditory feedback. Ankle stiffness was evaluated by performing a Least-squares system identification using a parametric model consisting of stiffness, damping, and inertia. The association between ankle muscle activation and joint stiffness was evaluated using correlation analyses. Linear regression models were used to determine the extent to which muscle activation contributed to ankle stiffness. An inclusive statistical approach (both classical and Bayesian analyses) was adopted to measure the statistical significance (p-value) and Bayes Factor (BF10). Results indicate that plantarflexor activity was positively correlated with ankle stiffness in both standing and walking (p<0.001, BF10>900), whereas dorsiflexor activity was negatively correlated with ankle stiffness in walking (p = 0.014, BF10 = 3.9) but not in standing (p = 0.725). Regression analyses indicated that ankle muscle activation predicted about 84% of the variation in ankle stiffness in standing and 45% in walking (p<0.001, BF10>100). Ankle muscle activation significantly contributes to ankle stiffness during standing and walking. The results highlight the role of muscle activation on maintaining joint stiffness and underscore the importance of accounting for muscle activation when measuring ankle stiffness in healthy as well as patient populations.

Analysis of the relationship between muscular strength and joint stiffness in children with Down syndrome during drop landing.

BACKGROUND: Children with Down syndrome (DS) have critical biomechanical impairments such as increased ligamentous laxity, muscle hypotonia, and dysfunctional motor coordination, which makes performing everyday tasks challenging.OBJECTIVE: The purpose of the study was to explore the differences in the vertical joint stiffness, plantar force, and range of motion during drop landing for DS and age-matched typically developing children.METHODS: Six young male children with DS and age-matched seven healthy typically developing children (TD) assessed joint strength using an isokinetic dynamometer and performed five trials of single-leg drop jump using force platform and motion capture system.RESULTS: The peak vertical ground reaction force (VGRF), Range of motion (ROM), joint stiffness, and joint strength of lower limb were calculated and compared across DS and TD groups. The results revealed a significantly larger peak VGRF [2.857, 0.001] values for the DS group compared to the TD groups. The results of Spearman’s correlation analysis showed a negative correlation between hip joint stiffness and knee joint ROM [0.886, 0.05] and ankle joint stiffness and knee joint ROM [0.829, 0.05] for DS.CONCLUSIONS: The abnormal movements observed among DS was not due to the difference in stiffness of the lower extremity but due to the utilization of different landing mechanisms with changes in ROM.

Functional Outcome of Hybrid External Fixator in Tibial Pilon Fractures

Introduction: Tibial pilon fractures are difficult fractures mostly secondary to high-energy trauma. There are various options to treat these fractures, but the priority is always an anatomic reduction and articular congruity with good soft tissue handling. The aim of the study was to analyze the functional outcome of tibial pilon fractures managed with a hybrid external fixator as definitive management.&#x0D; Methods: We evaluated 28 patients with tibial pilon fractures with a mean age of 34.8 years. All patients who fulfilled the inclusion criteria were taken to the operating room for debridement and application of a hybrid external fixator.&#x0D; Results: The most common mechanism of injury was road traffic accidents and most of our patients had comminuted fractures. The fibula was fractured in 23 (82.14%) of our patients. The fractures united on an average of 15.28 weeks. Based on the Ovadia &amp; Beals objective scoring system 75% of our patients scored excellent or good on objective scoring and subjective scoring 82.14% of our patients scored excellent or good. We had 12 cases of pin tract infection, 2 cases of delayed union, and 2 cases of malunion but no incidence of non-union, osteomyelitis, or septic arthritis. Eight of our patients had ankle joint stiffness.&#x0D; Conclusion: Hybrid external fixator is an effective method of treatment for tibial pilon fractures with comparable union rate and complications to other modalities.

Ankle joint salvage and reconstruction by limited ORIF combined with an Ilizarov external fixator for complex open tibial pilon fractures (AO 43-C3.3) with segmental bone defects

BackgroundOpen pilon fractures combined with sizeable segmental bone defects are rare, difficult to treat, and often result in the loss of ankle joint function. The purpose of this study was to determine clinical outcomes in patients with open pilon fractures and sizeable segmental bone defects treated by limited ORIF combined with an Ilizarov external fixator.MethodsWe conducted a retrospective analysis of open pilon fractures with sizeable segmental bone defects treated by limited ORIF combined with the Ilizarov external fixator strategy between July 2014 and August 2019. All patients were included for assessments of fracture healing and infection rates. Ankle functional outcomes were assessed in all patients according to the Paley criteria and American Orthopedic Foot and Ankle Society Score (AOFAS) at least 24 months post-injury.ResultsAll patients were followed up for a mean of 41.09 months. The mean bone defect size was 5.64 ± 1.21 cm. The average EFI and BTI were 1.56 ± 0.28 months/cm and 11.12 ± 0.74 days/cm, respectively. According to the Paley evaluation system, the success rate of ankle joint reconstruction was 64% (7/11). The mean score based on the AOFAS functional assessment was 77.73 ± 8.87. Five patients showed posttraumatic arthritis, one of whom required ankle arthrodesis. Three patients developed pin site infections, and one patient developed a deep infection after bone grafting.ConclusionThe strategy of limited ORIF combined with an Ilizarov external fixator can restore ankle function in most patients with complex open tibial pilon fractures. Ankle stiffness, pin tract infection, and traumatic arthritis were the most common complications associated with this therapy.

Diabetes and peripheral neuropathy are related to higher passive torque and stiffness of the knee and ankle joints

The aim of this study was to investigate the ankle and knee stiffness and passive torque in individuals with diabetes mellitus type 2 (DM2), with and without diabetic peripheral neuropathy (DPN) at different speed of motion. Forty-nine male individuals of a similar age were studied (17 with DM2 without DPN, 15 with DM2 and DPN, and 17 controls). Knee and ankle flexion and extension passive torques were assessed on an isokinetic dynamometer at 5°/s, 30°/s, and 60°/s. Our results showed that the individuals with DM2 exhibited greater knee stiffness compared to the controls and the individuals with DPN presented greater ankle stiffness and passive torque compared to the controls and those with DM2 without DPN. The mechanical impairments at the ankle passive structures were most evident at low speeds while the knee alterations were at 30°/s and 60°/s. Although the presence of DPN was a key factor for the increased passive ankle stiffness and torque, it was not related to the increase in the knee passive stiffness. Preventive measures for avoiding stiffness and motion impairments at the ankle and knee could be adopted in the early stages of DM2.

Effectiveness of Endoscopic Assisted Repair in Achilles Tendon Ruptures Compared to Percutaneous and Open Repair

Category:Arthroscopy; Sports; TraumaIntroduction/Purpose:The Achilles tendon rupture is the third most common tendon's injury, with an incidence of 16- 18/100000. Various repair's techniques are described, however the best surgical treatment remains controversial. Our purpose was to evaluate the effectiveness of endoscopic assisted repair compared to traditional open repair and percutaneous technique.Methods:We carried out a prospective observational study in patient operated in our Orthopedic Department between 2017 and 2019. We enrolled 47 patients (40 M; 7F), with a mean age 42,5 y.o with a mean follow up 32 months (12-60). The patients were divided in 3 groups according to the surgical procedures. Group A included 15 patients underwent to endoscopic assisted repair, Group B: 11 patients with percutaneous repair and group C 21 patients open repair. Demographic data, injury mechanisms, operation's time and technique were recorded. At final f-u complications, functional score (VAS, AOFAS AH, ATRS) were requested. The statistical analysis was performed with the t-student test. IRB approved.Results:The 78% of injuries occurred during recreational sport activities, with a majority during football amatorial matches. Operation's time was 42,5 minutes for group A, 33,3 for group B, 33,5 for group C. Among group A, 1 patient developed a DVT. In group B no major complications were reported. In group C a patient suffered from infection with suture insufficiency. Ankle stiffness was reported in 25% of patients in group C. No axonotmesis or neurotmesis of suralis was observed; 16 of patients complained transitory paresthesia in the postoperative. The mean time to return to work's activity was 44,2 days for group A, 35,6 days for group B, and group C 91,1 days, while the mean time to return to drive was in average 72,1 days for group A, 66 days for group B, 92,3 days for group C. ATRS was 79,3 for group A, 87,6 group B and 72,75 group C.Conclusion:This technique is safe and achievable with low postoperative pain and complications, early return to activities, and satisfactory functional outcomes. Compared to standard percutane-ous repair, endoscopy-assisted repair of Achilles tendon ruptures may be useful because it ensures precise placement of sutures through the ten-don and real-time visualization of the gap. Further large-scale, randomized and prospective clinical trials must be the subject of future prospective study.

Posterior malleolus fractures and their role in prognosis of malleolar fractures

Introduction: The treatment of ankle fractures with involvement of the posterior tibial margin remains a subject of debate. We have evaluated the clinical, radiological, and functional outcome of such fractures in 25 patients, all of which were managed surgically over an average follow- up period of 6 months. The treatment options available for malleolar fractures, to attain a proper anatomical alignment and stability of ankle joint, can lead to rewarding outcome for the patient.Materials and Methods: 25 patients with posterior malleolus fractures were managed surgically between June 2019 to November2021 were included in this series. The mean age, gender ratio, mode of trauma, fracture union time, and complications were noted. The AOFAS Hindfoot scores were used for assessing the Ankle function.Results: Of the 25 patients in the study, 21 were males and 4 were females. The mean age was 38.12 years. The mean fracture union (radiological) time was 14.04 weeks (range: 10–18 weeks). However Ankle function was excellent in 17 cases (68%) on the AOFAS hindfoot score with a average AOFAS score of 94.8. Also platting gives a better result than using cannulated cancellous screws. Better syndesmotic stability is observed after surgically treating posterior malleolus fractures.Conclusion: Fixation of the posterior malleolus to reduce persistent fragment displacement, regardless of size, as well as to restore syndesmotic stability, may lead to improved outcomes. We conclude that posterior malleolar fractures encountered in clinical practice need thorough assessment and meticulous surgical intervention. We achieved stable fixation and performed early mobilization of the ankle joint, which limits the complications of mainly ankle stiffness and have achieved excellent clinical and functional outcomes of surgically fixing the posterior malleolus fractures.

Outcomes and Complications of Open vs Minimally Invasive Surgical Repair of Acute Achilles Tendon Rupture: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Category:Ankle; Sports; TraumaIntroduction/Purpose:Traditionally, open surgical repair has provided improved functional outcomes, reduced re-rupture rates, and quicker recovery and return to activities at the expense of increased wound complications of infection and skin necrosis compared to nonoperative management. Ma and Griffith in 1977 introduced the percutaneous approach, and over the following decades, multiple improved techniques, and modifications thereof, have been described with comparable outcomes to the open repair. The current study aims to provide updated level I evidence comparing the open and minimally invasive (MIS) through a comprehensive search of literature published in English, Spanish, Portuguese, and German while avoiding limitations of previous studies such as heterogeneous study designs and a small number of included studies.Methods:Following the PRISMA guidelines, two independent team members searched several databases to identify randomized controlled trials (RCTs) comparing open and MIS Achilles tendon repairs. The primary outcomes were (1) Sural nerve injury, (2) Skin complications, (3) Infection (deep/superficial), whereas the secondary outcomes were (1) AOFAS/ATRS score, (2) surgical time, (3) re-rupture (4) adhesions (5) ankle range of motion. Population: Achilles tendon rupture Intervention: MIS repair Control: Open repair Outcomes: Primary: (1) Sural nerve injury, (2) Skin complications, (3) Infection (deep/superficial) Secondary: (1) AOFAS/ATRS score, (2) surgical time, (3) re-rupture, (4) adhesions, (5) ankle range of motion (6) other complications.Results:Ten RCTs qualified for the meta-analysis with a total of 522 patients. 260(49.8%) patients had open repair while 262(50.2%) had MIS repair. The mean total complication rate was 15.5% (0-36.4%) in open repair vs. 10.4% (0-45.5%) in MIS repair, with non-significant statistical difference (RR= 1.50,CI=0.87-2.57,p= 0.14;I2=40%). The mean re-rupture rate was 2.5% (0-6.8%) in open repair vs. 1.53% (0-4.6%) with MIS repair, with non-significant statistical difference (RR=1.56,CI=0.42-5.70,p= 0.50;I2=0%).No cases of sural nerve injury were reported in the open repair group. The mean sural nerve injury was 3.4%(0-7.3%) in the MIS group, that was statistically significant (RR= 0.16,CI=0.03-0.46,p=0.02;I2=0%). The mean deep infection rate in the open group was 1.4% (0-5%) while no deep infection was reported in MIS, with no statistically significant difference (RR= 3.24,CI=0.48-20.54,p= 0.23;I2=0%). The mean superficial infection rate was 6.04% (0-18.2%) and 0.40% (0-4.5%) for open and MIS repairs, respectively, with statistically significant difference (RR= 5.70,CI=1.80-18.02,p< 0.001;I2=0%).Conclusion:Open Achilles tendon repair is associated with longer surgical time, higher risk of superficial infection, and ankle stiffness, while MIS repair is associated with a greater risk of temporary sural nerve palsy. Re-rupture rate and functional outcomes are mostly equivalent. We found MIS to be a safe and reliable technique. However, high-quality standardized RCTs are still needed before recommending MIS as the gold standard for the management of Achilles tendon rupture.

Actuation Timing Perception of a Powered Ankle Exoskeleton and Its Associated Ankle Angle Changes During Walking.

Robotic ankle exoskeletons have the potential to extend human ability, and actuation timing serves as one of the critical parameters in its controller design. While many experiments have investigated the optimal actuation timing values to achieve different objective functions (e.g. minimizing metabolic cost), studies on users' perception of control parameters are gaining interest as it gives information on people's comfort, coordination, and trust in using devices, as well as providing foundations on how the sensorimotor system detects the exoskeleton behavior changes. The purpose of this study was to evaluate people's sensitivity to changes in exoskeleton actuation timing and its associated exoskeleton ankle angle changes during walking. Participants (n =15) with little or no prior experience with ankle exoskeletons were recruited and performed a psychophysical experiment to characterize their just-noticeable difference (JND) thresholds for actuation timing. Participants wore a bilateral active ankle exoskeleton and compared pairs of torque profiles with different actuation timings and low peak torque (0.225 Nm/kg) while walking on the treadmill. The mean timing JND across participants was 2.8±0.6% stride period. Individuals exhibited different sensitivity towards actuation timing, and their associated exoskeleton ankle angle changes also varied. The variance in ankle angle changes might be explained by their differences in ankle stiffness and different ankle torques provided during walking. The results provide insights into how people perceive the changes in exoskeleton control parameters and show individual differences in exoskeleton usage. The actuation timing JND found in this study can also help determine the necessary controller precision.

Ankle Arthritis Etiology Predicts Patterns of Gait Dysfunction: A Prospective Multivariate Gait Analysis

Category:Ankle; Ankle Arthritis; Basic Sciences/Biologics; HindfootIntroduction/Purpose:Preoperative factors influencing functional disability imparted on the patient by ankle arthritis have not previously been assessed with gait analysis. The purpose of this study was to assess the influence of ankle arthritis etiology and deformity, measured radiographically, on gait performance in a dedicated gait lab utilizing a multisegment foot model. With three calcaneal and four metatarsal markers in addition to standard lower extremity markers, the modified Helen Haynes model allows for the evaluation of range of motion (ROM) within the 'ankle-hindfoot segment.' The primary hypothesis was that three- dimensional ankle-hindfoot segment ROM would be more restricted in patients with post-traumatic ankle arthritis than other etiologies. The secondary hypothesis was that temporospatial and kinetic measures would not vary by etiology.Methods:A longitudinal cohort of 183 patients with end-stage ankle arthritis were prospectively enrolled from 2008-2018. Mean age was 61, BMI 29, and 56% were male. Four etiologic groups were defined: Post-fracture (100), arthritis caused by planovalgus foot deformity (23), chronic instability associated with cavovarus (32), and miscellaneous (28), comprised of inflammatory (7), idiopathic (6), instability without deformity (5), septic (2), and avascular necrosis (3) as causes. The four-segment Milwaukee foot model was used in a dedicated gait lab with a 12-camera motion capture system. Gait data was collected over a minimum 20 gait cycles across a 10-meter walkway. Kinetic data was simultaneously collected with two force plates embedded in the walkway operating at 1 MHz. AP and lateral tibiotalar angles, lateral talus-first metatarsal angles, calcaneal pitch, and tibiotalar ratio were measured. Multivariate regression analyzed the effect of etiology and radiographic measures on gait function, controlling for age, gender, and BMI.Results:The primary hypothesis was confirmed. Sagittal plane ankle-hindfoot segment ROM was lower in post-traumatic and higher in valgus patients compared to other etiological groups (P<0.0001) (Figure 1). Sagittal plane ankle-hindfoot segment ROM restriction relative to the contralateral limb was also more severe in the post-traumatic group than others (P=0.0005). Valgus AP tibiotalar angles were associated with greater sagittal plane ankle-hindfoot ROM (P=0.0016). The secondary hypothesis was disproven. Post-traumatic patients ambulate with greater maximum ankle moment than other groups (P=0.0043). Valgus patients ambulate with a comparatively longer step length (P<0.0001). Significant reductions in affected limb walking speed (P<0.0001), step length (P<0.0001), and maximum ankle moment (P=0.036), as well as increases in double limb (P=0.0007) and total support percentage (P<0.0001) were found among the miscellaneous etiology group.Conclusion:Of the four groups, patients with post-traumatic ankle arthritis ambulated with the greatest ankle and hindfoot stiffness, but also the greatest ankle moment. Patients with valgus ankle arthritis had the greatest ROM through the ankle and hindfoot and the longest step length. In addition to diminished ROM, patients in the miscellaneous group had the lowest cadence, symmetry, and torque of gait. The etiology of severe ankle arthritis can predict the pattern of gait dysfunction, which, in turn, may inform choices of surgical reconstruction.

Multi-degrees-of-freedom soft robotic ankle-foot orthosis for gait assistance and variable ankle support.

This paper presents the design, modeling, analysis, fabrication, and experimental characterization of the Soft Robotic Ankle-Foot Orthosis (SR-AFO), which is a wearable soft robot designed for ankle assistance, and a pilot human study of its use. Using two novel pneumatically-powered soft actuators, the SR-AFO is designed to assist the ankle in multiple degrees-of-freedom during standing and walking tasks. The flat fabric pneumatic artificial muscle (ff-PAM) contracts upon pressurization and assists ankle plantarflexion in the sagittal plane. The Multi-material Actuator for Variable Stiffness (MAVS) aids in supporting ankle inversion/eversion in the frontal plane. Analytical models of the ff-PAM and MAVS were created to understand how the changing of the design parameters affects tensile force generation and stiffness support, respectively. The models were validated by both finite element analysis and experimental characterization using a universal testing machine. A set of human experiments was performed with able-bodied participants to evaluate: 1) lateral ankle support during quiet standing, 2) lateral ankle support during walking over compliant surfaces, and 3) plantarflexion assistance during push-off in treadmill walking. Group results revealed increased lateral ankle stiffness during quiet standing with the MAVS active, reduced lateral ankle deflection while walking over compliant surfaces with the MAVS active, and reduced muscle effort in ankle platarflexors during 40-60% of the gait cycle with the dual ff-PAM active. The SR-AFO shows promising results in providing lateral ankle support and plantarflexion assistance with able-bodied participants, which suggests a potential to help restore the gait of impaired users in future trials.

Design and structural analysis of a passive ankle-foot prosthesis with manually adjustable stiffness and having two degrees of freedom

The majority of commercial Below Knee Prosthetics are Passive Prosthetics as they are lightweight, affordable, durable and require less maintenance. Since the human ankle is a set of highly integrated joints, ankle design is the most crucial aspect of a Below Knee (transtibial) prosthesis design process. This research work focuses on developing and analysing a Passive Ankle-Foot Prosthesis to attain 2 DOF, i.e., plantarflexion-dorsiflexion and inversion-eversion motions of a foot, such that it could mimic the behaviour of a natural lost limb. Further, this study presents the integration of manual ankle stiffness modulation into the same design for dorsiflexion-plantarflexion which can be altered by the amputee to a preferred stiffness for various ambulation requirements. The design proposed in this study also assimilates the features of an ESR and a SACH foot to a significant level. The structural analysis demonstrates that the device can sustain a vertical load of 800 N with the Factor of Safety (FOS) of 1.5. The deflection analysis of the leaf spring used in the design shows the exponential increase in stiffness as the slider moves beyond 70% of the length of the leaf spring towards its free end.

A Novel Method for Field Measurement of Ankle Joint Stiffness in Hopping

Stiffness of ankle joint has been investigated in a wide range of biomechanical studies with a focus on the improvement of performance and reduction in the risk of injury. However, measuring ankle joint stiffness (AJS) using the existing conventional methodologies requires sophisticated equipment such as force plate and motion analyses systems. This study presents a novel method for measuring AJS during a hopping task with no force or motion measurement system. Also the validity of the proposed new method was investigated by comparing the results against those obtained using conventional method in which motion capture and force plate data are used. Twelve participants performed the controlled hopping task at 2.2 Hz, on a force platform, and six high speed cameras recorded the movement. To calculate the AJS in both methods, the lower extremity was modeled as a three linked rigid segments robot with three joints. In the new method, the contact time and flight time were used to calculate ground reaction force, and inverse kinematic and inverse dynamic approaches were used to calculate the ankle kinematic and kinetic. The AJS calculated using the new method was compared against the results of conventional method as the reference. The calculated AJS using this new method (506.47 ± 177.84 N·m/rad) showed a significant correlation (r = 0.752) with the AJS calculated using conventional method (642.39 ± 185.96 N·m/rad). The validation test showed a mean difference of −24.76% using Bland–Altman plot. The presented method can be used as a valid, and low-cost tool for assessing AJS in the field in low resource settings.

Outcomes and Complications of Open Versus Minimally Invasive Repair of Acute Achilles Tendon Ruptures: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Background: An acute Achilles tendon rupture is one of the most common sports injuries, affecting 18 per 100,000 persons, and its operative repair has been evolving and increasing in frequency since the mid-1900s. Traditionally, open surgical repair has provided improved functional outcomes, reduced rerupture rates, and a quicker recovery and return to activities at the expense of increased wound complications such as infections and skin necrosis compared with nonoperative management. In 1977, Ma and Griffith introduced the percutaneous approach, and over the following decades, multiple improved techniques, and modifications thereof, have been described with comparable outcomes with open repair. Purpose: The current study aimed to provide updated level 1 evidence comparing open repair with minimally invasive surgery (MIS) through a comprehensive search of the literature published in English, Arabic, Spanish, Portuguese, and German while avoiding limitations of previous studies such as heterogeneous study designs and a small number of included trials. Study Design: Meta-analysis; Level of evidence, 1. Methods: Following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, 2 independent team members searched several databases to identify randomized controlled trials (RCTs) comparing open repair and MIS of Achilles tendon ruptures. The primary outcomes were (1) functional outcomes, (2) reruptures, (3) sural nerve injuries, and (4) infections (deep/superficial), whereas the secondary outcomes were (1) skin complications, (2) adhesions, (3) other complications, (4) ankle range of motion, and (5) surgical time. Results: There were 10 RCTs that qualified for the meta–analysis with a total of 522 patients. Overall, 260 (49.8%) patients underwent open repair, while 262 (50.2%) underwent MIS. The mean postoperative AOFAS score was 94.8 and 95.7 for open repair and MIS, respectively, with a nonsignificant difference (mean difference [MD], –0.73 [95% CI, –1.70 to 0.25]; P = .14; I2 = 0%). The pooled mean total complication rate was 15.5% (0%-36.4%) for open repair and 10.4% (0%-45.5%) for MIS, with a nonsignificant statistical difference (odds ratio [OR], 1.50 [95% CI, 0.87-2.57]; P = .14; I2 = 40%). The mean rerupture rate was 2.5% (0%-6.8%) for open repair versus 1.5% (0%-4.6%) for MIS, with a nonsignificant statistical difference (OR, 1.56 [95% CI, 0.42-5.70]; P = .50; I2 = 0%). No cases of sural nerve injuries were reported in the open repair group. The mean sural nerve injury rate was 3.4% (0%-7.3%) in the MIS group, which was statistically significant (OR, 0.16 [95% CI, 0.03-0.46]; P = .02; I2 = 0%). The mean overall superficial infection rate was 6.0% (0%-18.2%) and 0.4% (0%-4.5%) for open repair and MIS, respectively, with a statistically significant difference (OR, 5.70 [95% CI, 1.80-18.02]; P < .001; I2 = 0%). The mean overall deep infection rate reported in the open repair group was 1.4% (0%-5.0%), while no deep infection was reported in the MIS group, with no statistically significant difference (OR, 3.14 [95% CI, 0.48-20.54]; P = .23; I2 = 0%). There were no significant differences between the open repair and MIS groups in the skin necrosis and dehiscence rate, adhesion rate, or keloid scar rate. The mean surgical time was 51.0 and 29.7 minutes for open repair and MIS, respectively, with a statistically significant difference (MD, 21.13 [95% CI, 15.50-26.75]; P < .001; I2 = 15%). Conclusion: Open Achilles tendon repair was associated with a longer surgical time, higher risk of superficial infections, and higher risk of ankle stiffness, while MIS was associated with a greater risk of temporary sural nerve palsy. The rerupture rate and functional outcomes were mostly equivalent. We found MIS to be a safe and reliable technique. However, high–quality standardized RCTs are still needed before recommending MIS as the gold standard for managing Achilles tendon ruptures.

Isolated Joint Block Progression Training Improves Leaping Performance in Dancers.

The purpose of this study was to investigate the effect of a 12-week ankle-specific block progression training program on saut de chat leaping performance [leap height, peak power (PP), joint kinetics and kinematics], maximal voluntary isometric plantar flexion (MVIP) strength, and Achilles tendon (AT) stiffness. Dancers (training group n = 7, control group n = 7) performed MVIP at plantarflexed (10◦) and neutral ankle positions (0◦) followed by ramping isometric contractions equipped with ultrasound to assess strength and AT stiffness, respectively. Dancers also performed saut de chat leaps surrounded by 3-D motion capture atop force platforms to determine center of mass and joint kinematics and kinetics. The training group then followed a 12-week ankle-focused program including isometric, dynamic constant external resistance, accentuated eccentric loading, and plyometric training modalities, while the control group continued dancing normally. We found that the training group's saut de chat ankle PP (59.8%), braking ankle stiffness (69.6%), center of mass PP (11.4%), and leap height (12.1%) significantly increased following training. We further found that the training group's MVIP significantly increased at 10◦ (17.0%) and 0◦ (12.2%) along with AT stiffness (29.6%), while aesthetic leaping measures were unchanged (peak split angle, mean trunk angle, trunk angle range). Ankle-specific block progression training appears to benefit saut de chat leaping performance, PP output, ankle-joint kinetics, maximal strength, and AT stiffness, while not affecting kinematic aesthetic measures. We speculate that the combined training blocks elicited physiological changes and enhanced neuromuscular synchronization for increased saut de chat leaping performance in this cohort of dancers.

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).

Abnormal synergistic gait mitigation in acute stroke using an innovative ankle\u2013knee\u2013hip interlimb humanoid robot: a preliminary randomized controlled trial

Abnormal spasticity and associated synergistic patterns are the most common neuromuscular impairments affecting ankle–knee–hip interlimb coordinated gait kinematics and kinetics in patients with hemiparetic stroke. Although patients with hemiparetic stroke undergo various treatments to improve gait and movement, it remains unknown how spasticity and associated synergistic patterns change after robot-assisted and conventional treatment. We developed an innovative ankle–knee–hip interlimb coordinated humanoid robot (ICT) to mitigate abnormal spasticity and synergistic patterns. The objective of the preliminary clinical trial was to compare the effects of ICT combined with conventional physical therapy (ICT-C) and conventional physical therapy and gait training (CPT-G) on abnormal spasticity and synergistic gait patterns in 20 patients with acute hemiparesis. We performed secondary analyses aimed at elucidating the biomechanical effects of Walkbot ICT on kinematic (spatiotemporal parameters and angles) and kinetic (active force, resistive force, and stiffness) gait parameters before and after ICT in the ICT-C group. The intervention for this group comprised 60-min conventional physical therapy plus 30-min robot-assisted training, 7 days/week, for 2 weeks. Significant biomechanical effects in knee joint kinematics; hip, knee, and ankle active forces; hip, knee, and ankle resistive forces; and hip, knee, and ankle stiffness were associated with ICT-C. Our novel findings provide promising evidence for conventional therapy supplemented by robot-assisted therapy for abnormal spasticity, synergistic, and altered biomechanical gait impairments in patients in the acute post-stroke recovery phase.Trial Registration: Clinical Trials.gov identifier NCT03554642 (14/01/2020).

Passive and active muscle elasticity of medial gastrocnemius is related to performance in sprinters.

Limited information is available on the association between muscle material properties and sprint performance. We aimed to identify whether and how the elasticity of passive and active muscle of the medial gastrocnemius (MG) is related to sprint performance. MG shear wave speed was measured under passive and active (20%, 50%, 80% of maximal voluntary contraction [MVC]) conditions, with ultrasound shear wave elastography, in 18 male sprinters. Passive and active ankle joint stiffness was assessed by applying a short-range fast stretch during 0%, 20%, 50%, and 80% MVC of plantar flexion. Additionally, rate of torque development (RTD) during explosive plantar flexion was measured. Passive and active MG shear wave speed was negatively correlated with 100-m race time. Passive MG shear wave speed was positively correlated with RTD, and RTD was negatively correlated with 100-m race time. MG shear wave speed at 50% and 80% MVC showed a positive correlation with ankle joint stiffness at the corresponding contraction level, and ankle joint stiffness at 50% and 80% MVC showed negative correlations with 100-m race time. These correlations were significant even after controlling for MVC torque. Our findings indicate that passive and active muscle elasticity of plantar flexor is important to achieve superior sprint performance. Specifically, high elasticity of passive MG could be related to superior sprint performance through high explosive torque production. In contrast, high elasticity of active MG at moderate-to-high intensity is likely related to high sprint performance through high ankle joint stiffness.

Classification of Ankle Joint Stiffness during Walking to Determine the Use of Ankle Foot Orthosis after Stroke

Categorization based on quasi-joint stiffness (QJS) may help clinicians select appropriate ankle foot orthoses (AFOs). The objectives of the present study were to classify the gait pattern based on ankle joint stiffness, also called QJS, of the gait in patients after stroke and to clarify differences in the type of AFO among 72 patients after stroke. Hierarchical cluster analysis was used to classify gait patterns based on QJS at least one month before the study, which revealed three distinct subgroups (SGs 1, 2, and 3). The proportion of use of AFOs, articulated AFOs, and non-articulated AFOs were significantly different among SGs 1–3. In SG1, with a higher QJS in the early and middle stance, the proportion of the patients using articulated AFOs was higher, whereas in SG3, with a lower QJS in both stances, the proportion of patients using non-articulated AFOs was higher. In SG2, with a lower QJS in the early stance and higher QJS in the middle stance, the proportion of patients using AFOs was lower. These findings indicate that classification of gait patterns based on QJS in patients after stroke may be helpful in selecting AFO. However, large sample sizes are required to confirm these results.

Multivariable passive ankle impedance in stroke patients: A preliminary study

Multivariable ankle mechanical impedance was estimated in four stroke survivors, in coupled dorsi- plantarflexion and inversion–eversion. We applied external torque perturbation with an ankle robot and used multi-input, multi-output stochastic system identification methods to estimate impedance, in both paretic and nonparetic limbs. Subjects were instructed to remain at rest throughout the four trials performed on each leg. Impedance projected onto the directions of maximum and minimum stiffness was fit to a 2nd order linear model, including inertia, viscosity and stiffness. For most trials, stiffness and damping in dorsi-plantarflexion are increased on the paretic side. However, for two subjects, overall impedance is not increased in the absence of sustained involuntary tonic contraction, registering values comparable to the non-paretic side. Thus, we speculate that the intrinsic properties of the paretic ankle remained unaffected at the evaluated pose. Spasticity (hyperflexive stretch reflex) would have systematically increased stiffness and damping, even in the absence of involuntary contraction. Hence, we speculate that these two subjects did not exhibit spasticity, while the remaining two subjects did, since impedance was increased, with no involuntary tonic muscle contraction. Regarding inversion–eversion, impedance in this direction remained unaffected by stroke. We evaluated two volunteers before and after the application of botulinum toxin. Surprisingly, ankle stiffness was not reduced, but anisotropy was normalized.