Ankle Stiffness Research Articles

Prefabricated ankle-foot orthoses for children with cerebral palsy to overcome spastic drop-foot: does orthotic ankle stiffness matter?

Spastic drop-foot is a common problem in children with cerebral palsy that may lead to tripping and falling. To improve ankle dorsiflexion in swing phase, prefabricated carbon-composite ankle-foot orthoses are commonly prescribed; by increasing ankle stiffness, these orthoses may also improve knee extension in stance. To compare the effect of a stiff vs. flexible prefabricated ankle-foot orthosis on sagittal plane ankle and knee kinematics and kinetics during walking. Cross-sectional, repeated-measures, interventional study. Twenty-seven children and adolescents with cerebral palsy who had drop-foot in swing were included. Gait analysis was conducted under four conditions: barefoot, shod, with a stiff, and with a flexible orthosis. Participants were divided into two groups including children and adolescents who have a flexed knee during stance (KF, N = 12) and without flexed knee during stance (KE, N = 15). Ankle dorsiflexion in swing phase was significantly improved compared with the shod condition by 6.3 degrees (SD = 3.3 degrees) only in the KE group when using the flexible orthosis. For the stiff orthosis, knee extension in stance was significantly increased by 2.4 degrees (SD = 3.3 degrees) in the KE group compared with the shod condition. No significant improvements were observed for the KF group. Further analysis indicated that only seven patients in the KF group with weak ankle plantarflexors improved knee extension while using the stiff orthosis. Our results suggested that in the KE group, the flexible orthosis was best suited for patients with drop-foot without a knee extension deficit. The stiff orthosis was not suitable in this group as it caused a hyperextended knee without improving dorsiflexion in swing phase. Therefore, stiffness should be considered when prefabricated orthoses are prescribed.

Application of Leg, Vertical, and Joint Stiffness in Running Performance: A Literature Overview.

Stiffness, the resistance to deformation due to force, has been used to model the way in which the lower body responds to landing during cyclic motions such as running and jumping. Vertical, leg, and joint stiffness provide a useful model for investigating the store and release of potential elastic energy via the musculotendinous unit in the stretch-shortening cycle and may provide insight into sport performance. This review is aimed at assessing the effect of vertical, leg, and joint stiffness on running performance as such an investigation may provide greater insight into performance during this common form of locomotion. PubMed and SPORTDiscus databases were searched resulting in 92 publications on vertical, leg, and joint stiffness and running performance. Vertical stiffness increases with running velocity and stride frequency. Higher vertical stiffness differentiated elite runners from lower-performing athletes and was also associated with a lower oxygen cost. In contrast, leg stiffness remains relatively constant with increasing velocity and is not strongly related to the aerobic demand and fatigue. Hip and knee joint stiffness are reported to increase with velocity, and a lower ankle and higher knee joint stiffness are linked to a lower oxygen cost of running; however, no relationship with performance has yet been investigated. Theoretically, there is a desired “leg-spring” stiffness value at which potential elastic energy return is maximised and this is specific to the individual. It appears that higher “leg-spring” stiffness is desirable for running performance; however, more research is needed to investigate the relationship of all three lower limb joint springs as the hip joint is often neglected. There is still no clear answer how training could affect mechanical stiffness during running. Studies including muscle activation and separate analyses of local tissues (tendons) are needed to investigate mechanical stiffness as a global variable associated with sports performance.

Effects of Robot-Aided Rehabilitation on the Ankle Joint Properties and Balance Function in Stroke Survivors: A Randomized Controlled Trial.

Background: Stroke survivors with impaired control of the ankle due to stiff plantarflexors often experience abnormal posture control, which affects balance and locomotion. Forceful stretching may decrease ankle stiffness and improve balance. Recently, a robot-aided stretching device was developed to decrease ankle stiffness of patient post-stroke, however, their benefits compared to manual stretching exercises have not been done in a randomized controlled trial, and the correlations between the ankle joint biomechanical properties and balance are unclear.Objective: To compare the effects of robot-aided to manual ankle stretching training in stroke survivors with the spastic ankle on the ankle joint properties and balance function post-stroke, and further explore the correlations between the ankle stiffness and balance.Methods: Twenty inpatients post-stroke with ankle spasticity received 20 minutes of stretching training daily over two weeks. The experimental group used a robot-aided stretching device, and the control group received manual stretching. Outcome measures were evaluated before and after training. The primary outcome measure was ankle stiffness. The secondary outcome measures were passive dorsiflexion ranges of motion, dorsiflexor muscle strength, Modified Ashworth Scale (MAS), Fugl-Meyer Motor Assessment of Lower Extremity (FMA-LE), Berg Balance Scale (BBS), Modified Barthel Index (MBI), and the Pro-Kin balance test.Results: After training, two groups showed significantly within-group improvements in dorsiflexor muscle strength, FMA-LE, BBS, MBI (P < 0.05). The between-group comparison showed no significant differences in all outcome measures (P > 0.0025). The experimental group significantly improved in the stiffness and passive range of motion of dorsiflexion, MAS. In the Pro-Kin test, the experimental group improved significantly with eyes closed and open (P < 0.05), but significant improvements were found in the control group only with eyes open (P < 0.05). Dorsiflexion stiffness was positively correlated with the Pro-Kin test results with eyes open and the MAS (P < 0.05).Conclusions: The robot-aided and manual ankle stretching training provided similar significant improvements in the ankle properties and balance post-stroke. However, only the robot-aided stretching training improved spasticity and stiffness of dorsiflexion significantly. Ankle dorsiflexion stiffness was correlated with balance function.Clinical Trial Registration: www.chictr.org.cn ChiCTR2000030108.

Effects of sex and walking speed on the dynamic stiffness of lower limb joints

Fast walking may require a non-uniform change of dynamic stiffness among lower limb joints to deal with this daily task’s demands. The change of dynamic joint stiffness may be distinct between females and males. This study aimed to test for differences in dynamic stiffness among lower limb joints in response to increased walking speed in males and females. Thirty-five participants walked in two randomized conditions: self-selected speed and fast speed (25% greater than the self-selected speed). Dynamic stiffnesses of the ankle, knee, and hip were calculated as the linear slope of the moment–angle curve’s regression line during their major power absorption phase of the walking cycle. The comparison between conditions showed that the knee (p < 0.001) and hip (p = 0.031) increased their stiffness at the fast compared to self-selected speed. Ankle stiffness was not different between conditions (p = 0.818). The comparison among joints across speeds showed that the knee had a greater increase than the ankle (p = 0.001) and hip (p < 0.001), with no difference between ankle and hip (p = 0.081). The sex of the participant influenced only the ankle stiffness, in which males had greater stiffness than females (p = 0.008). These findings demonstrated that the lower limb joints changed their dynamic stiffness differently, and only the ankle stiffness was influenced by sex. The non-uniform adjustments of stiffness may provide the necessary stability and allow the individual to deal with greater demand for walking fast.

How Compliance of Surfaces Affects Ankle Moment and Stiffness Regulation During Walking.

Humans can regulate ankle moment and stiffness to cope with various surfaces during walking, while the effect of surfaces compliance on ankle moment and stiffness regulations remains unclear. In order to find the underlying mechanism, ten healthy subjects were recruited to walk across surfaces with different levels of compliance. Electromyography (EMG), ground reaction forces (GRFs), and three-dimensional reflective marker trajectories were recorded synchronously. Ankle moment and stiffness were estimated using an EMG-driven musculoskeletal model. Our results showed that the compliance of surfaces can affect both ankle moment and stiffness regulations during walking. When the compliance of surfaces increased, the ankle moment increased to prevent lower limb collapse and the ankle stiffness increased to maintain stability during the mid-stance phase of gait. Our work improved the understanding of gait biomechanics and might be instructive to sports surface design and passive multibody model development.

Leg and Joint Stiffness Adaptations to Minimalist and Maximalist Running Shoes.

The running footwear literature reports a conceptual disconnect between shoe cushioning and external impact loading: footwear or surfaces with greater cushioning tend to result in greater impact force characteristics during running. Increased impact loading with maximalist footwear may reflect an altered lower-extremity gait strategy to adjust for running in compliant footwear. The authors hypothesized that ankle and knee joint stiffness would change to maintain the effective vertical stiffness, as cushioning changed with minimalist, traditional, and maximalist footwear. Eleven participants ran on an instrumental treadmill (3.5m·s-1) for a 5-minute familiarization in each footwear, plus an additional 110 seconds before data collection. Vertical, leg, ankle, and knee joint stiffness and vertical impact force characteristics were calculated. Mixed model with repeated measures tested differences between footwear conditions. Compared with traditional and maximalist, the minimalist shoes were associated with greater average instantaneous and average vertical loading rates (P < .050), greater vertical stiffness (P ≤ .010), and less change in leg length between initial contact and peak resultant ground reaction force (P < .050). No other differences in stiffness or impact variables were observed. The shoe cushioning paradox did not hold in this study due to a similar musculoskeletal strategy for running in traditional and maximalist footwear and running with a more rigid limb in minimalist footwear.

Distal metaphyseal tibial fractures: Is an IMIL nail an adequate implant? An observational study on the functional and radiological outcome

The purpose of this study is to evaluate the functional outcome as well as radiological outcome of distal metaphyseal tibial fractures treated with intramedullary interlocking nail after 6 months post surgery in terms of degree of functionality preserved and degree of malalignment respectively.This was an observational study conducted with 38 patients. Data was retrieved from the MRD. Patients were clinically assessed at 6 months interval and as and when needed by Karlstorm and Orleud Score. Fracture alignment post operatively and radiological union in two standard perpendicular (AP & Lateral) views were assessed. In patients operated in the past, their immediate post-operative and 6 month follow up x-ray was accessed. Functionality was assessed by available information in the patient chart and from present followup.6 cases (20%) had excellent results, 16 cases (55%) had good results, 7 cases (24%) had fair result (satisfactory/moderate) mostly for minor complaints of knee pain, ankle stiffness. 7 patients were unavailable for assessment of functionality. 1 patient had expired due to natural causes in conclusion Interlocking Intramedullary Nailing for Distal Metaphyseal Tibial Fractures is an acceptable line as it helps with early mobilization of the patient which helps in healing of the fracture and prevents joint stiffness thereby restoring complete motion. The construct is biomechanically stable. Fibular fixation with rush nails predisposed to delayed union, hence plating is recommended or revision of rush nailing to plating when feasible.

Understanding patient preference in prosthetic ankle stiffness

BackgroundUser preference has the potential to facilitate the design, control, and prescription of prostheses, but we do not yet understand which physiological factors drive preference, or if preference is associated with clinical benefits.MethodsSubjects with unilateral below-knee amputation walked on a custom variable-stiffness prosthetic ankle and manipulated a dial to determine their preferred prosthetic ankle stiffness at three walking speeds. We evaluated anthropomorphic, metabolic, biomechanical, and performance-based descriptors at stiffness levels surrounding each subject’s preferred stiffness.ResultsSubjects preferred lower stiffness values at their self-selected treadmill walking speed, and elected to walk faster overground with ankle stiffness at or above their preferred stiffness. Preferred stiffness maximized the kinematic symmetry between prosthetic and unaffected joints, but was not significantly correlated with body mass or metabolic rate.ConclusionThese results imply that some physiological factors are weighted more heavily when determining preferred stiffness, and that preference may be associated with clinically relevant improvements in gait.

Characterization and clinical implications of ankle impedance during walking in chronic stroke

Individuals post-stroke experience persisting gait deficits due to altered joint mechanics, known clinically as spasticity, hypertonia, and paresis. In engineering, these concepts are described as stiffness and damping, or collectively as joint mechanical impedance, when considered with limb inertia. Typical clinical assessments of these properties are obtained while the patient is at rest using qualitative measures, and the link between the assessments and functional outcomes and mobility is unclear. In this study we quantify ankle mechanical impedance dynamically during walking in individuals post-stroke and in age-speed matched control subjects, and examine the relationships between mechanical impedance and clinical measures of mobility and impairment. Perturbations were applied to the ankle joint during the stance phase of walking, and least-squares system identification techniques were used to estimate mechanical impedance. Stiffness of the paretic ankle was decreased during mid-stance when compared to the non-paretic side; a change independent of muscle activity. Inter-limb differences in ankle joint damping, but not joint stiffness or passive clinical assessments, strongly predicted walking speed and distance. This work provides the first insights into how stroke alters joint mechanical impedance during walking, as well as how these changes relate to existing outcome measures. Our results inform clinical care, suggesting a focus on correcting stance phase mechanics could potentially improve mobility of chronic stroke survivors.

Serial Within-Session Improvements in Ankle Dorsiflexion During Clinical Interventions Including Mobilization-With-Movement and A Novel Manipulation Intervention - A Case Series.

BackgroundPersisting reductions in ankle dorsiflexion range of motion are commonly encountered clinically and seen to be associated with adverse outcomes after ankle and other lower extremity injuries. Accordingly improving identified deficits is a common goal for rehabilitation; however, little data exists documenting any improvement related to interventions in these patients.PurposeTo document the change in dorsiflexion range of motion after stretching and mobilization-with-movement and exercise and a novel manipulation intervention in a population of injured athletes.DesignCase series in 38 consecutive injured athletes with persisting reductions in ankle dorsiflexion range of motion (42 “stiff” ankles, 34 uninjured) in an outpatient sports physiotherapy clinic.MethodDuring a single treatment session, two baseline measurements of weight-bearing dorsiflexion were taken at the start of the session to establish reliability and minimum detectable change, and then the same measures were performed after stretching and a mobilization-with-movement intervention, and again after clinical exercise and a novel manipulation which was applied on both ankles.ResultsExcellent reliability was demonstrated (ICC2,1>0.93, MDC=3.5°) for the dorsiflexion measure. Statistically significant (p<0.01), but clinically meaningless improvements were seen after stretching and the mobilization-with-movement intervention on the injured and uninjured legs (1.9° and 1.4° respectively) with greater improvements seen after exercise and the subsequent manipulation (6.9° and 4.7°).ConclusionsThe relatively simple clinical exercise and manipulation intervention program was associated improvement in dorsiflexion range of motion in this cohort with persisting ankle stiffness. The interventions described largely restored range of motion consistent with baseline levels of the uninjured ankles. Improvements were also seen in the uninjured ankles following intervention.

The efficacy of ilizarov method for management of long tibial bone and soft tissue defect

IntroductionPatients with open fracture Gustillo-Anderson grade 3 had undergone several surgical procedures, but still ended up with expose long dead bone or infected. Illizarov method was used to address long bone and soft tissue defect after re-debridement with radical resection of long dead bone or infected segment. MethodsWe included 14 patients (mean age: 30.86 ± 11.49) with non-union tibial fracture with long dead and infected bone segment who had undergone several debridement, bone grafting or spacer and soft tissue closure procedure due to open fracture of tibia grade 3. The subjects underwent re-debridement with radical resection of dead or infected bone segment followed by Illizarov method to perform bone transport procedure for bone defect filling and simultaneously restore severe soft tissue loss and bone lengthening procedure. ResultsAll subjects had achieved satisfactory results with mean docking period of bone transport 3.78 ± 0.54 months, union time at the docking side 7 (5.5–9) months. Soft tissue was covered and no recurrence of infection. Three subjects had Leg Length Discrepancy (LLD) of 1 cm, whereas the remaining had zero discrepancy. No significant pain was observed at final follow-up and 4 patients had ankle joint stiffness. ConclusionThe Illizarov method can effectively address long bone and soft tissue defects by distraction osteogenesis through bone transport procedure that filling the defect gradually without bone graft and simultaneously enhancing soft tissue closure without tertiary soft tissue procedure subsequently followed with bone lengthening procedure to correct the limb length discrepancy.

The tightening parameters of the vibratory devices modify their disturbing postural effects

The purpose was to specify the impact of two different forces exerted by vibratory devices on the Achilles tendon on postural balance. The postural balance of 13 participants was evaluated on a force platform in two 40 s bipedal stance conditions with closed eyes. Tendon vibrations (80 Hz) were triggered 10 s after the beginning of the postural evaluation and applied during 20 s. Two levels of the force exerted by the vibrators were calibrated using load cells to control the tightening parameters of the vibrators: a strong tightening (ST) condition at 45 N and a light tightening (LT) condition at 5 N. The soleus electromyographic (EMG) activity and the spatio-temporal parameters of displacement of the centre of foot pressure (COP) were analysed. To analyse the effects of the introduction, the adaptation and the end of the stimulation, non-parametric tests were used. The results indicated that the soleus EMG activity increased only in the ST condition. However, during the vibration the anteroposterior COP position was significantly more in a backward position in the LT condition. At the end of the vibration, COP parameters increased more in the LT condition than the ST condition. This study demonstrated that the effects of the vibration depended on the force exerted by the devices on the tendons. The ST increased the vibration effects on EMG activity through greater stimulating effects compared to the LT. However, the ST could also increase the ankle joint stiffness and/or somaesthetic sensory information, which attenuated the COP backward shift.

Outcome of various modalities of management of distal tibia fracture

Background: Distal tibial fractures represent less than 7% of all tibial fractures. The present study was conducted to compare outcome of various modalities of management of distal tibia fractures. Materials & Methods: 45 distal tibia fracture patients of both genders were divided equally into 3 groups of 15 each. Group I patients were treated with intra-medullary nail, group II patients treated with external fixator and group III patients with MIPO (Minimally Invasive Percutaneous Osteosynthesis). The American Orthopaedic Foot and Ankle Society score was recorded. Gustilo Anderson (GA) type of fractures and complications were recorded. Results: GA type 1 was seen in 10, 2 in 8, 3A in 7 and no GA type in 20 patients. AO classification A1 was present in 5, A2 in 6, A3 in 15, B1 in 8, C1 in 5, C2 in 5 and C3 in 3 patients. The mean AOFAS score was 74.2 in group I, 70.5 in group II and 89.2 in group III. Complications were non- union seen in 1, 2 and 3, ankle stiffness in 2, 2 and 1, wound discharge in 0, 1 and 1, vagus deformity in 3, 2 and 0 and valgus deformity in 1, 3 and 2 in group I, II and III respectively. The difference was significant (P

Method for characterization of dynamic ankle stiffness in patients with spasticity.

Dynamic ankle stiffness has been quantified as the slope of the ankle joint moment-angle curve over the gait interval of the second rocker, defined explicitly as the period of the gait cycle from the first relative maximum plantar flexion in early stance to maximum dorsiflexion in midstance. However, gastrocnemius spasticity may interfere with the second ankle rocker in patients with spasticity. This gait disruption results in stiffness calculations which are misleading. Current dynamic stiffness metrics need to be modified. The main goal of this study was to develop and test a new method to better evaluate dynamic ankle stiffness in individuals with pathologic gait who lack a second rocker interval. Twenty unimpaired ambulators (10/20 female, 26.7 ± 5.0 years, BMI: 23.2 ± 2.2) and 9 individuals with cerebral palsy (5/9 female, 5.7 ± 1.7 years, BMI: 14.6 ± 2.1, GMFCS Levels: I - 2, II - 5, III - 2) participated in this study. Dynamic ankle stiffness was evaluated using the previous kinematic method, defined by the interval of maximum plantar flexion to maximum dorsiflexion angle in midstance, and the proposed kinetic method, defined by the interval from the maximum dorsiflexion moment to first peak plantar flexion moment. Stiffness was quantified as the linear slope between the sagittal plane ankle angle and moment. Method differences were explored using an equivalence test (α = 0.05). There was equivalence between the methods for unimpaired ambulators (p = 0.000) and a lack of equivalence for patients with spasticity (p = 0.958). The new method was successfully applied to all 9 pediatric ambulators with CP and demonstrated increased stiffness in patients with spasticity as compared to the previous method. The ability to objectively calculate ankle stiffness in pathologic gait is critical for determining change associated with clinical intervention.

Frontal plane ankle stiffness increases with weight-bearing

Ankle sprains are among the most common musculoskeletal injuries. They are not isolated innocuous injuries as 30–40% of people who sprain their ankles develop chronic ankle instability. Ankle instability is typically assessed under passive unloaded conditions, ignoring any potential contribution of joint loading or muscle activation to the maintenance of ankle stability. Thus, the relevance of unloaded ankle stability assessments to the evaluation of impairments in chronic ankle instability or the prediction of future ankle sprains is questionable. Ankle impedance, which quantifies the resistance to an imposed rotation, has often been used to quantify ankle stability. However, few studies have investigated impedance in the frontal plane where sprains occur, and none have systematically investigated the effect of weight-bearing on ankle impedance. The objective of this study was to determine whether weight-bearing affects frontal plane ankle impedance. We had subjects systematically alter the weight on the tested ankle, while imposed frontal plane rotations were applied to estimate the impedance. We found that ankle stiffness, the static component of impedance, increased proportionally with the weight on the ankle. This increase in stiffness was due to a combination of the increase loading on the joint and the increase in muscle activation that occurs during weight-bearing. Finally, we found that men had a greater stiffness than women over the majority of the weight-bearing range. These results highlight the importance of clinically assessing ankle stability during weight-bearing conditions to better determine the impairments in chronic ankle instability and identify those at risk for ankle sprains.

Mechanical properties of ankle joint and gastrocnemius muscle in spastic children with unilateral cerebral palsy measured with shear wave elastography

The aim of this study was to describe passive mechanical and morphological properties of the ankle joint and gastrocnemius medialis (GM) muscle in paretic and contralateral legs in highly functional children with unilateral cerebral palsy (UCP) using shear wave elastography (SWE).SWE measurements on the GM muscle were performed in both paretic and contralateral legs during passive ankle dorsiflexion using a dynamometer in 11 children (mean age: 10 years 6 months) with UCP. Torque-angle and shear modulus-angle relationships were fitted using an exponential model to determine passive ankle joint and GM muscle stiffness respectively. Based on shear-modulus-angle relationship, slack angle and shear modulus of GM muscle were compared between legs. GM and Achilles tendon length were determined at rest using ultrasonography.No significant difference was found between legs for passive ankle joint (p = 0.26; 11.2%; 95 %CI: 31.9, −9.4) and GM muscle passive stiffness (p = 0.62; −4.4%; 95 %CI: 14.7, –23.4). GM shear modulus at a common angle was significantly higher on the paretic leg (p = 0.02; +56.5%; 95 %CI: 100.5, 12.6). GM slack angle on the paretic leg was significantly shifted to a more plantarflexed position (p = 0.04; +25.5%; 95 %CI: 49.7, 1.3) and this was associated with a non-significant lower muscle length compared to the contralateral leg (p = 0.05; −4.5%; 95 %CI: −0.4, −8.7).Increased passive tension on the paretic leg when compared to the contralateral one may be explained in large part by muscle shortening. The role of altered mechanical properties remains unknown.

Quantification and Modeling of Ankle Stiffness During Standing Balance.

This study investigates the factors contributing to the modulation of ankle stiffness during standing balance and evaluates the reliability of linear stiffness models. A dual-axis robotic platform and a visual feedback display were used to quantify ankle stiffness in both the sagittal and frontal planes while subjects controlled different levels of ankle muscle co-contraction, center-of-pressure (CoP), and loading on the ankle. Results of 40 subjects demonstrated that ankle stiffness in the sagittal plane linearly increased with the increasing level of these three factors. The linear model relating the change in these factors from the baseline measurements during quiet standing to the change in weight normalized ankle stiffness resulted in high reliability (R2 = 0.83). Ankle stiffness in the frontal plane increased with the increasing ankle muscle co-contraction and ankle loading, but the linearity was less obvious. It also exhibited a clear nonlinear trend when CoP was shifted mediolaterally. Consequently, the reliability of the linear model was low for ankle stiffness in the frontal plane (R2 = 0.37). During standing balance, ankle stiffness in the sagittal plane could be well explained by a linear model if ankle muscle activation, CoP, and ankle loading were collectively considered. However, the linear model cannot capture highly variable and nonlinear ankle stiffness characteristics in the frontal plane. The outcomes of this study could benefit the development of lower-extremity robots and their controllers. Furthermore, the ankle stiffness models could be used as a baseline in developing patient-specific ankle rehabilitation protocols.

Leg Stiffness, Joint Stiffness, and Running-Related Injury: Evidence From a Prospective Cohort Study.

Background:The spring-like behavior of the leg and the joints of the lower body during running are thought to influence a wide range of physiologic and mechanical phenomena, including susceptibility to overuse injury. If leg and joint stiffness are associated with running-related injuries, altering joint or leg stiffness may be a useful avenue for injury rehabilitation and injury prevention programs.Purpose:To test the associations between running-related injury and leg stiffness, knee stiffness, and ankle stiffness in a prospective study of recreational runners.Study Design:Cohort study; Level of evidence, 2.Methods:A total of 49 healthy recreational runners took part in a year-long study. Participants completed a 3-dimensional kinematic and kinetic biomechanical assessment at baseline and reported training volume and injury status in a weekly survey during the follow-up period. Relationships between stiffness and injury were assessed at the level of individual legs (n = 98) using spline terms in Cox proportional hazards models.Results:During follow-up, 23 participants (29 legs) sustained injury. The median time to injury was 27 weeks (53.27 hours of training). Relative injury rate as a function of knee stiffness displayed a weak and nonsignificant U-shaped curve (P = .187-.661); ankle and leg stiffness displayed no discernable associations with relative injury rate (leg stiffness, P = .215-.605; ankle stiffness, P = .419-.712).Conclusion:Leg and joint stiffness may not be important factors in the development of running-related injuries. Moderate changes in leg and joint stiffness are unlikely to substantially alter injury risk.

Functional results of compound extra articular tibial pilon fractures managed with hybrid external fixator

&lt;p&gt;&lt;strong&gt;Background: &lt;/strong&gt;Distal tibia fractures are difficult to treat. It is often difficult to assess the potential risk of surgical complications because of the variations in the clinical findings. Less subcutaneous tissue, limited blood supply and no muscle insertions are the factors that tend to make the healing of the soft tissue more complex. Compounding presents a great challenge for the treating surgeon regarding the treatment options.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Methods:&lt;/strong&gt;&lt;strong&gt; &lt;/strong&gt;A total of 23 patients were included in the study based on the inclusion and exclusion criteria and were managed by hybrid external fixator as definitive treatment. They were kept in follow up for at least 6 months and were assessed using Ovadia and Beal’s objective and subjective scoring.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Results: &lt;/strong&gt;All patients achieved fracture union with 82% patients reporting excellent to good functional outcome. Pin site infections and ankle stiffness were most common complications.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; A very good outcome is achieved in compound extra articular tibial pilon fractures with the hybrid fixator technique. Adequate stability is provided and hence early motion and ambulation can be started.&lt;/p&gt;

Variable stiffness foot design and validation

Energy storing and returning prosthetic feet are commonly prescribed. Research has demonstrated advantages to use these types of prosthetic feet. However, their stiffness in the sagittal plane is fixed and cannot adapt to different walking tasks and user preference.In this paper, we propose a novel prosthetic foot design capable of modulating its stiffness in the sagittal plane. The Variable Stiffness Ankle unit (VSA) is mounted on a commercially available prosthetic foot. The stiffness of the foot is adjusted with a lightweight servo motor controlled wirelessly. The stiffness change is accomplished by moving the supports points on the glass fiber leaf spring of the VSA ankle unit.We described the design and characterized changes in ankle stiffness using a mechanical test bench. A novel method was used to capture mechanical test data using a six degree of freedom load cell, allowing us to contrast mechanical and biomechanical data.A transtibial unilateral amputee performed level ground walking on an instrumented treadmill. The VSA prosthetic foot exhibited ankle stiffness change in the mechanical test bench. Ankle stiffness changes were also confirmed during the biomechanical analysis.Future work will involve additional subjects. The VSA prosthetic foot could improve user satisfaction and help prosthetist to fine tune prosthetic feet during fittings.