Understanding gait alterations: trunk flexion and its effects on walking neuromechanics.

Evolutionary and functional adaptations of morphology and postural tone of the spine and trunk are intrinsically shaped by the field of gravity in which humans move. Gravity also significantly impacts the timing and levels of neuromuscular activation, particularly in foot-support interactions. During step-to-step transitions, the centre of mass velocity must be redirected from downwards to upwards. When walking upright, this redirection is initiated by the trailing leg, propelling the body forward and upward before the foot contact of the leading leg, defined as an anticipated transition. In this study, we investigate the neuromechanical adjustments when walking with a bent posture. Twenty adults walked on an instrumented treadmill at 4 km/h under normal (upright) conditions and with varying degrees of anterior trunk flexion (10, 20, 30, and 40°). We recorded lower-limb kinematics, ground reaction forces under each foot, and the electromyography activity of five lower-limb muscles. Our findings indicate that with increasing trunk flexion, there is a lack of these anticipatory step-to-step transitions, and the leading limb performs the redirection after the ground collision. Surprisingly, attenuating distal extensor muscle activity at the end of stance is one of the main impacts of trunk flexion. Our observations may help to understand the physiological mechanisms and biomechanical regulations underlying our tendency toward an upright posture, as well as possible motor control disturbances in some diseases associated with trunk orientation problems.

The Effect of Sensor Placement on Measured Distal Tibial Accelerations During Running.

Inertial measurement units (IMUs) attached to the distal tibia are a validated method of measuring lower-extremity impact accelerations, called tibial accelerations (TAs), in runners. However, no studies have investigated the effects of small errors in IMU placement, which would be expected in real-world, autonomous use of IMUs. The purpose of this study was to evaluate the effect of a small proximal shift in IMU location on mean TAs and relationships between TAs and ground reaction force loading rates. IMUs were strapped to 18 injury-free runners at a specified standard location (∼1 cm proximal to medial malleolus) and 2 cm proximal to the standard location. TAs and ground reaction forces were measured while participants ran at self-selected and 10% slower/faster speeds. Mean TA was lower at the standard versus proximal IMU location in the faster running condition (P = .026), but similar in the slower (P = .643) and self-selected conditions (P = .654). Mean TAs measured at the standard IMU explained more variation in ground reaction force loading rates (r2 = .79-.90; P < .001) compared with those measured at the proximal IMU (r2 = .65-.72; P < .001). These results suggest that careful attention should be given to IMU placement when measuring TAs during running.

A passive exoskeleton can assist split-belt adaptation.

An exoskeletal device can assist walking in those with gait deficits. A passive exoskeleton can be a favorable choice for local or home rehabilitation settings because it is affordable, light weight, and less complex to utilize. While there is research that investigates the effects of exoskeleton on gait research examining the effects of such devices on gait adaptation, is rare. This is important because in diseases like stroke, the ability to flexibly adapt is affected, such that functional recovery becomes difficult. The purpose of this study was to characterize gait adaptation patterns that result from exoskeleton usage during a split-belt adaptation task. Healthy young participants were randomly assigned to a unilateral exoskeleton or a no-exoskeleton group. Each participant performed the specific split-belt adaptation tasks on the treadmill, where the speed of each belt could be controlled independently. Symmetry indices of spatiotemporal variables were calculated to quantify gait adaptation. To analyze the adaptation, trials were divided into early and late adaptation. We also analyzed degree of adaptation, and transfer effects. We also measured the symmetry of the positive power generated by the individual legs during the split-belt task to determine if using exoskeleton assistance reduced power in the exoskeleton group versus the no-exoskeleton group. Use of a passive exoskeleton device altered gait adaptation during a split-belt treadmill task in comparison to the control group. Such adaptation was found to be largely restricted to the temporal domain. Changes in the gait coordination patterns consisted of both early and late adaptive changes, especially in intra-limb patterns like stance time rather than inter-limb patterns like step time. Although the symmetry of the positive power generated during the split-belt task was found to be reduced for the exoskeleton-assistance group, it was shown that this was primarily the result of increased positive power generated by the side not receiving exoskeletal assistance. An unpowered assistive device can provide a unique solution for coordinating the lower limbs during different gait tasks. Such a solution could reduce the neural burden of adaptation consequently resulting in a reduction of the mechanical burden of walking during the bilateral gait coordination task. This may be useful for accelerating gait rehabilitation in different patient populations. However, balance control is important to consider during unilateral exoskeletal assistance.

Validity and Reliability of the Insole3 Instrumented Shoe Insole for Ground Reaction Force Measurement during Walking and Running.

Pressure-detecting insoles such as the Insole3 have potential as a portable alternative for assessing vertical ground reaction force (vGRF) outside of specialized laboratories. This study evaluated whether the Insole3 is a valid and reliable alternative to force plates for measuring vGRF. Eleven healthy participants walked overground at slow and moderately paced speeds and ran at a moderate pace while collecting vGRF simultaneously from a force plate (3000 Hz) and Insole3 (100 Hz). Intraclass correlation coefficients (ICC) demonstrated excellent vGRF agreement between systems during both walking speeds for Peak 1, Peak 2, the valley between peaks, and the vGRF impulse (ICC > 0.941). There was excellent agreement during running for the single vGRF peak (ICC = 0.942) and impulse (ICC = 0.940). The insoles slightly underestimated vGRF peaks (−3.7% to 0.9% bias) and valleys (−2.2% to −1.8% bias), and slightly overestimated impulses (4.2% to 5.6% bias). Reliability between visits for all three activities was excellent (ICC > 0.970). The Insole3 is a valid and reliable alternative to traditional force plates for assessing vGRF during walking and running in healthy adults. The excellent ICC values during slow walking suggests that the Insole3 may be particularly suitable for older adults in clinical and home settings.

Longitudinal changes in tibial and femoral cartilage thickness are associated with baseline ambulatory kinetics and cartilage oligomeric matrix protein (COMP) measures in an asymptomatic aging population.

OBJECTIVE: To address the need for early knee osteoarthritis (OA) markers by testing if longitudinal cartilage thickness changes are associated with specific biomechanical and biological measures acquired at a baseline test in asymptomatic aging subjects. DESIGN: Thirty-eight asymptomatic subjects over age 45 years were studied at baseline and at an average of 7-9 year follow-up. Gait mechanics and knee MRI were measured at baseline and MRI was obtained at follow-up to assess cartilage thickness changes. A subset of the subjects (n = 12) also had serum cartilage oligomeric matrix protein measured at baseline in response to a mechanical stimulus (30-min walk) (mCOMP). Baseline measures, including the knee extension (KEM), flexion (KFM), adduction (KAM) moments and mCOMP, were tested for associations with cartilage thickness changes in specific regions of the knee. RESULTS: Cartilage change in the full medial femoral condyle (p = 0.005) and external medial femoral region (p = 0.041) was negatively associated with larger early stance peak KEM. Similarly, cartilage change in the full medial femoral region (p = 0.009) and medial femoral external region (p = 0.043) was negatively associated with larger first peak KAM, while cartilage change in the anterior medial tibia was positively associated with larger first peak KAM (p = 0.003). Cartilage change in the anterior medial tibia was also significantly associated (p = 0.011) with mCOMP levels 5.5-h post-activity (percentage of pre-activity levels). CONCLUSIONS: Interactions found between gait, mechanically-stimulated serum biomarkers, and cartilage thickness in an at-risk aging asymptomatic population suggest the opportunity for early detection of OA with new approaches that bridge across disciplines and scales.

Relationships Between Arch Height Flexibility and Medial-Lateral Ground Reaction Forces in Rearfoot and Forefoot Strike Runners.

Higher medial-lateral forces have been reported in individuals with stiffer foot arches. However, this was in a small sample of military personnel who ran with a rearfoot strike pattern. Therefore, our purpose was to investigate whether runners, both rearfoot and forefoot strikers, show different associations between medial-lateral forces and arch stiffness. A group of 118 runners (80 rearfoot strikers and 38 forefoot strikers) were recruited. Ground reaction force data were collected during running on an instrumented treadmill. Arch flexibility was assessed as the difference in arch height from sitting to standing positions, and participants were classified into stiff/flexible groups. Group comparisons were performed for the ratio of medial:vertical and lateral:vertical impulses. In rearfoot strikers, runners with stiff arches demonstrated significantly higher medial:vertical impulse ratios (P = .036). Forefoot strikers also demonstrated higher proportions of medial forces; however, the mean difference did not reach statistical significance (P = .084). No differences were detected in the proportion of lateral forces between arch flexibility groups. Consistent with previous findings in military personnel, our results indicate that recreational runners with stiffer arches have a higher proportion of medial forces. Therefore, increasing foot flexibility may increase the ability to attenuate medial forces.

Cross-Sectional Analysis of Backward, Forward, and Dual Task Gait Kinematics in People With Parkinson Disease With and Without Freezing of Gait.

People with Parkinson disease demonstrate increased gait variability, but the primary variability sources are poorly understood. People with Parkinson disease and freezing of gait (freezers) have greater gait impairments than people with Parkinson disease without freezing of gait (nonfreezers), which may relate to cerebellar dysfunction. Thirteen freezers and 31 nonfreezers completed backward, forward, and forward with dual task gait trials. Sagittal joint angle waveforms were extracted for the hip, knee, and ankle using 3D motion capture. Decomposition indices were calculated for the 3 joint combinations. Principal component analysis extracted variance sources from the joint waveforms. Freezers had significantly greater decomposition between hip-ankle (F1,42 = 5.1, P = .03) and hip-knee (F1,42 = 5.3, P = .03) movements. The principal component analysis did not differentiate freezers and nonfreezers; however, primary variance sources differed between conditions. Primary variance during forward and forward with dual task gait came from joint angle magnitude and peak angle timing. Backward gait showed primary variance from joint angle magnitude and range of motion. The results show that freezers decompose movement more than nonfreezers, implicating cerebellar involvement in freezing of gait. Primary variance differs between gait conditions, and tailoring gait interventions to address variability sources may improve intervention efficacy.

Gait mechanics contribute to exercise induced pain flares in knee osteoarthritis.

BACKGROUND: Exercise-induced pain flares represent a significant barrier for individuals with knee osteoarthritis to meet physical activity recommendations. There is a need to understand factors that contribute to pain flares and the potential for the motor system to adapt and reduce joint loading should a flare occur. The study aim was to examine the impact of a bout of exercise on self-reported pain, walking mechanics and muscle co-contraction for participants with knee osteoarthritis. METHODS: Thirty-six adults (17 healthy older and 19 knee osteoarthritis) participated in this study. Self-reported pain, joint mechanics and muscle co-activation during gait at two self-selected speeds were collected before and after a 20-min preferred pace treadmill walk (20MTW). RESULTS: Eight of nineteen osteoarthritis participants had a clinically significant pain flare response to the 20MTW. At baseline the participants that did not experience a pain flare had smaller knee flexion and total reaction moments compared to both the participants with pain flares (p = 0.02; p = 0.05) and controls (p < 0.001; p < 0.001). In addition, the 2nd peak knee adduction (p = 0.01) and internal rotation (p = 0.001) moments were smaller in the no flares as compared to controls. The pain flare participants differed from controls with smaller knee internal rotation moments (p = 0.03), but greater relative hamstrings (vs. quadriceps) and medial (vs. lateral) muscle activation (p = 0.04, p = 0.04) compared to both controls and no flare participants (p = 0.04, p = 0.007). Following the 20MTW there were greater decreases in the 1st and 2nd peak knee adduction (p = 0.03; p = 0.02), and internal rotation (p = 0.002) moments for the pain flare as compared to the no flare group. In addition, for the pain flare as compared to controls, greater decreases in the knee flexion (p = 0.03) and internal rotation (p = 0.005) moments were found. CONCLUSIONS: Individuals who adapt their gait to reduce knee joint loads may be less susceptible to exercise-induced pain flares. This highlights a potential role of gait biomechanics in short-term osteoarthritis pain fluctuations. The results also suggest that despite the chronic nature of osteoarthritis pain, the motor system's ability to respond to nociceptive stimuli remains intact.

The Reliability and Validity of the Loadsol® under Various Walking and Running Conditions.

The assessment of loading during walking and running has historically been limited to data collection in laboratory settings or with devices that require a computer connection. This study aims to determine if the loadsol®-a single sensor wireless insole-is a valid and reliable method of assessing force. Thirty (17 male and 13 female) recreationally active individuals were recruited for a two visit study where they walked (1.3 m/s) and ran (3.0 and 3.5 m/s) at a 0%, 10% incline, and 10% decline, with the visits approximately one week apart. Ground reaction force data was collected on an instrumented treadmill (1440 Hz) and with the loadsol® (100 Hz). Ten individuals completed the day 1 protocol with a newer 200 Hz loadsol®. Intraclass correlation coefficients (ICC3,k) were used to assess validity and reliability and Bland⁻Altman plots were generated to better understand loadsol® validity. Across conditions, the peak force ICCs ranged from 0.78 to 0.97, which increased to 0.84⁻0.99 with the 200 Hz insoles. Similarly, the loading rate ICCs improved from 0.61 to 0.97 to 0.80⁻0.96 and impulse improved from 0.61 to 0.97 to 0.90⁻0.97. The 200 Hz insoles may be needed for loading rate and impulse in running. For both walking and running, the loadsol® has excellent between-day reliability (>0.76).

Modeling knee osteoarthritis pathophysiology using an integrated joint system (IJS): a systematic review of relationships among cartilage thickness, gait mechanics, and subchondral bone mineral density.

OBJECTIVE: To introduce an integrated joint system (IJS) model of joint health and osteoarthritis (OA) pathophysiology through a systematic review of the cross-sectional relationships among three knee properties (cartilage thickness, gait mechanics, and subchondral bone mineral density). METHODS: Searches using keywords associated with the three knee properties of interest were performed in PubMed, Scopus, and Ovid databases. English-language articles reporting cross-sectional correlations between at least two knee properties in healthy or tibiofemoral OA human knees were included. A narrative synthesis of the data was conducted. RESULTS: Of the 5600 retrieved articles, 13 were included, eight of which reported relationships between cartilage thickness and gait mechanics. The 744 tested knees were separated into three categories based on knee health: 199 healthy, 340 at-risk/early OA, and 205 late OA knees. Correlations between knee adduction moment and medial-to-lateral cartilage thickness ratios were generally positive in healthy, inconclusive in at-risk/early OA, and negative in late OA knees. Knee adduction moment was positively correlated with medial-to-lateral tibial subchondral bone mineral density ratios in knees of all health categories. One study reported a positive correlation between lateral tibial subchondral bone mineral density and femoral cartilage thickness in at-risk/early OA knees. CONCLUSIONS: The correlations identified between knee properties in this review agreed with the proposed relationship-based IJS model of OA pathophysiology. Accordingly, the IJS model could provide insights into overcoming current barriers to developing disease-modifying treatments by considering multiple aspects of OA disease, aspects that could be assessed simultaneously at an in vivo system level.

Developments in development: What have we learned from primate locomotor ontogeny?

The importance of locomotion to evolutionary fitness has led to extensive study of primate locomotor behavior, morphology and ecology. Most previous research has focused on adult primates, but in the last few decades, increased attention to locomotor development has provided new insights toward our broader understanding of primate adaptation and evolution. Here, we review the contributions of this body of work from three basic perspectives. First, we assess possible determinants on the timing of locomotor independence, an important life history event. Significant influences on timing of locomotor independence include adult female body mass, age at weaning, and especially relative brain size, a significant predictor of other primate life history variables. Additionally, we found significant phylogenetic differences in the timing of locomotor independence, even accounting for these influences. Second, we discuss how structural aspects of primate growth may enhance the locomotor performance and safety of young primates, despite their inherent neuromotor and musculoskeletal limitations. For example, compared to adults, growing primates have greater muscle mechanical advantage, greater bone robusticity, and larger extremities with relatively long digits. Third, focusing on primate quadrupedalism, we provide examples that illustrate how ontogenetic transitions in morphology and locomotion can serve as a model system for testing broader principles underlying primate locomotor biomechanics. This approach has led to a better understanding of the key features that contribute to primates' stride characteristics, gait patterns, limb force distribution, and limb postures. We have learned a great deal from the study of locomotor ontogeny, but there is much left to explore. We conclude by offering guidelines for future research, both in the laboratory and the field.

Walking at non-constant speeds: mechanical work, pendular transduction, and energy congruity.

Although almost half of all walking bouts in urban environments consist of less than 12 consecutive steps and several day-to-day gait activities contain transient gait responses, in most studies gait analysis is performed at steady-state. This study aimed to analyze external (Wext ) and internal mechanical work (Wint ), pendulum-like mechanics, and elastic energy usage during constant and non-constant speeds. The mechanical work, pendular transduction, and energy congruity (an estimate of storage and release of elastic energy) during walking were computed using two force platforms. We found that during accelerating gait (+NCS) energy recovery is maintained, besides extra W+ext , for decelerating gait (-NCS) poor energy recovery was counterbalanced by W-ext and C% predominance. We report an increase in elastic energy usage with speed (4-11%). Both W-ext and %C suggests that elastic energy usage is higher at faster speeds and related to -NCS (≈20% of elastic energy usage). This study was the first to show evidences of elastic energy usage during constant and non-constant speeds.

Elevated proinflammatory cytokines in response to mechanical stimulus are associated with reduced knee loading 2 years after anterior cruciate ligament reconstruction.

BACKGROUND: The aim of this study was to test the hypothesis that proinflammatory cytokines correlate with knee loading mechanics during gait following a mechanical walking stimulus in subjects 2 years after anterior cruciate ligament reconstruction. Elevated systemic levels of proinflammatory cytokines can be sustained for years after injury. Considering roughly 50% of these patients progress to Osteoarthritis 10-15 years after injury, a better understanding of the role of proinflammatory cytokines such as tumor necrosis factor-α and Interleukin-1ß on Osteoarthritis risk is needed. METHODS: Serum proinflammatory cytokines concentrations were measured in 21 subjects 2 years after unilateral ACLR from blood drawn at rest and 3.5 h after 30 min of walking. An optoelectronic system and a force plate measured subjects' knee kinetics. Correlations were tested between inflammatory marker response and knee extension and knee adduction moments. FINDINGS: Changes in proinflammatory cytokines due to mechanical stimulus were correlated (R = 0.86) and showed substantial variation between subjects in both cytokines at 3.5 h post-walk. Knee loading correlated with 3.5-h changes in tumor necrosis factor-α concentration (Knee extension moment: R = -0.5, Knee adduction moment: R = -0.5) and Interleukin-1ß concentration (Knee extension moment: R = -0.44). However, no significant changes in concentrations were observed in tumor necrosis factor-α and Interleukin-1ß when comparing baseline and post walking stimulus conditions. INTERPRETATION: The significant associations between changes in serum proinflammatory markers following a mechanical stimulus and gait metrics in subjects at risk for developing Osteoarthritis underscore the importance of investigating the interaction between biomarkers and biomechanical factors in Osteoarthritis development.

Patients with unilateral ankle arthritis have decreased discrete and time-series limb symmetry compared to healthy controls.

Patients with ankle arthritis (AA) have side-to-side limb differences at the ankle and in spatiotemporal measures; however, the degree of symmetry between limbs has not been compared to a healthy population. The purpose of this study was to determine differences in limb symmetry during walking for discrete and time-series measures when comparing patients with unilateral AA to healthy participants. Thirty-seven AA and 37 healthy participants were age, gender, and body mass index matched. Three-dimensional gait mechanics and ground reaction force (GRF) were captured during four to seven walking trails. GRF and hip and ankle mechanics were extracted bilaterally for each trial. The Normalized Symmetry Index and Statistical Parameter Mapping were used to assess discrete and time-series symmetry, respectively. Discrete symmetry was analyzed using linear mixed-effect models to determine significant differences between groups (α = 0.05). Compared to healthy participants, patients with AA had decreased weight acceptance (p = 0.017) and propulsive (p < 0.001) GRF, ankle plantarflexion (p = 0.021), ankle dorsiflexion (p = 0.010), and ankle plantarflexion moment (p < 0.001) symmetry. Significant regions of difference were found between limbs and groups throughout the stance phase for the vertical GRF force (p < 0.001), the ankle angle during push-off (p = 0.047), the plantarflexion moment (p < 0.001), and the hip extension angle (p = 0.034) and moment (p = 0.010). Patients with AA have decreased symmetry in the vertical GRF and at the ankle and hip during the weight acceptance and propulsive portions of the stance phase. Therefore, clinicians should try a non improving symmetry focusing on changing hip and ankle mechanics during the weight acceptance and propulsive phases of gait.

Isolated effects of footwear structure and cushioning on running mechanics in habitual mid/forefoot runners.

The true differences between barefoot and shod running are difficult to directly compare because of the concomitant change to a mid/forefoot footfall pattern that typically occurs during barefoot running. The purpose of this study was to compare isolated effects of footwear structure and cushioning on running mechanics in habitual mid/forefoot runners running shod (SHOD), barefoot (BF), and barefoot on a foam surface (BF+FOAM). Ten habitually shod mid/forefoot runners were recruited (male = 8, female = 2). Repeated measures ANOVA (α = 0.05) revealed differences between conditions for only vertical peak active force, contact time, negative and total ankle joint work, and peak dorsiflexion angle. Post hoc tests revealed that BF+FOAM resulted in smaller vertical active peak magnitude and instantaneous vertical loading rate than SHOD. SHOD resulted in lower total ankle joint work than BF and BF+FOAM. BF+FOAM resulted in lower negative ankle joint work than either BF or SHOD. Contact time was shorter with BF than BF+FOAM or SHOD. Peak dorsiflexion angle was smaller in SHOD than BF. No other differences in sagittal joint kinematics, kinetics, or ground reaction forces were observed. These overall similarities in running mechanics between SHOD and BF+FOAM question the effects of footwear structure on habituated mid/forefoot running described previously.

A hierarchical clustering approach for examining potential risk factors for bone stress injury in runners.

Bone stress injuries (BSI) are overuse injuries that commonly occur in runners. BSI risk is multifactorial and not well understood. Unsupervised machine learning approaches can potentially elucidate risk factors for BSI by looking for groups of similar runners within a population that differ in BSI incidence. Here, a hierarchical clustering approach is used to identify groups of collegiate cross country runners (32 females, 21 males) based on healthy pre-season running (4.47 m·s-1) gait data which were aggregated and dimensionally reduced by principal component analysis. Five distinct groups were identified using the cluster tree. Visual inspection revealed clear differences between groups in kinematics and kinetics, and linear mixed effects models showed between-group differences in metrics potentially related to BSI risk. The groups also differed in BSI incidence during the subsequent academic year (Rand index = 0.49; adjusted Rand index = -0.02). Groups ranged from those including runners spending less time contacting the ground and generating higher peak ground reaction forces and joint moments to those including runners spending more time on the ground with lower loads. The former groups showed higher BSI incidence, indicating that short stance phases and high peak loads may be risk factors for BSI. Since ground contact duration may itself account for differences in peak loading metrics, we hypothesize that the percentage of time a runner is in contact with the ground may be a useful metric to include in machine learning models for predicting BSI risk.

Self-reported walking difficulty influences gait characteristics in patients with medial compartment knee osteoarthritis.

BACKGROUND: To differentiate gait strategies per knee osteoarthritis and self-reported walking difficulty during self-selected regular and fast gait speeds. We hypothesize that knee osteoarthritis gait characteristics during self-selected regular and fast gait speeds will be most accentuated by the osteoarthritis and walking difficulty group, followed by osteoarthritis and no walking difficulty, and least in the control group. METHODS: Prospective study of community-dwelling older adults (n = 39) who walk at functional speeds (≥1.0 m per second) were age and sex matched across the three groups. Gait strategies including knee excursion and moments, muscle activation and co-contraction, and limb dynamics (linear acceleration and jerk) were compared between groups during self-selected regular and fast gait speed trials. Significant group differences were defined as P < 0.05 and an effect size greater than small. FINDINGS: Based on walking difficulty, adduction moments (P-range = 0.00-0.03; effect size range,r = 0.42-0.52) and lateral quadriceps-gastrocnemius co-activations (P = 0.01;r = 0.36) were significant during regular gait speeds; and extension (P = 0.03;d = 0.59) and adduction (P-range = 0.00-0.02;d = 0.86;r = 0.40) moments were significant during fast trials. Per knee osteoarthritis presence, adduction moment(P = 0.01;r = 0.49), medial-quadriceps (P = 0.00;d = 1.04;r = 0.61), lateral-hamstrings (P = 0.04;d = 0.55), medial-gastrocnemius (P = 0.02;r = 0.40), medial quadriceps-hamstrings (P = 0.02;r = 0.38), medial quadriceps-gastrocnemius (P = 0.00;r = 0.56), and all limb dynamics (P = 0.00-0.01;d = 1.13-1.18;r = 0.35-0.47) were significant during regular gait speeds. Extension excursion (P = 0.02;d = 0.63), adduction moment (P = 0.01;d = 0.85) and medial-quadriceps (P = 0.01;r = 0.38) were significant during fast trials. INTERPRETATION: Many gait strategies during regular speeds that differ per walking difficulty and knee osteoarthritis attenuated at fast speeds. Perhaps gait training at fast speeds for those with knee osteoarthritis related walking difficulty is biomechanically and functionally beneficial.

Medical and Biomechanical Risk Factors for Incident Bone Stress Injury in Collegiate Runners: Can Plantar Pressure Predict Injury?

Background: Bone stress injury (BSI) is a common reason for missed practices and competitions in elite track and field runners. Hypothesis: It was hypothesized that, after accounting for medical risk factors, higher plantar loading during running, walking, and athletic movements would predict the risk of future BSI in elite collegiate runners. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 39 elite collegiate runners (24 male, 15 female) were evaluated during the 2014-2015 academic year to determine the degree to which plantar pressure data and medical history (including Female and Male Athlete Triad risk factors) could predict subsequent BSI. Runners completed athletic movements while plantar pressures and contact areas in 7 key areas of the foot were recorded, and the measurements were reported overall and by specific foot area. Regression models were constructed to determine factors related to incident BSI. Results: Twenty-one runners (12 male, 9 female) sustained ≥1 incident BSI during the study period. Four regression models incorporating both plantar pressure measurements and medical risk factors were able to predict the subsequent occurrence of (A) BSIs in female runners, (B) BSIs in male runners, (C) multiple BSIs in either male or female runners, and (D) foot BSIs in female runners. Model A used maximum mean pressure (MMP) under the first metatarsal during a jump takeoff and only misclassified 1 female with no BSI. Model B used increased impulses under the hindfoot and second through fifth distal metatarsals while walking, and under the lesser toes during a cutting task, correctly categorizing 83.3% of male runners. Model C used higher medial midfoot peak pressure during a shuttle run and triad cumulative risk scores and correctly categorized 93.3% of runners who did not incur multiple BSIs and 66.7% of those who did. Model D included lower hindfoot impulses in the shuttle run and higher first metatarsal MMP during treadmill walking to correctly predict the subsequent occurrence of a foot BSI for 75% of women and 100% without. Conclusion: The models collectively suggested that higher plantar pressure may contribute to risk for BSI.

In silicomodeling of tibial fatigue life in physically active males and females during different exercise protocols.

Preventing bone stress injuries (BSI) requires a deep understanding of the condition's underlying causes and risk factors. Subject-specific computer modeling studies of gait mechanics, including the effect of changes in running speed, stride length, and landing patterns on tibial stress injury formation can provide essential insights into BSI prevention. This study aimed to computationally examine the effect of different exercise protocols on tibial fatigue life in male and female runners during prolonged walking and running at three different speeds. To achieve these aims, we combined subject-specific magnetic resonance imaging (MRI), gait data, finite element analysis, and a fatigue life prediction algorithm, including repair and adaptation's influence. The algorithm predicted a steep increase in the likelihood of developing a BSI within the first 40 days of activity. In five of the six subjects simulated, faster running speeds corresponded with higher tibial strains and higher probability of failure. Our simulations also showed that female subjects had a higher mean peak probability of failure in all four gait conditions than the male subjects studied. The approach used in this study could lay the groundwork for studies in larger populations and patient-specific clinical tools and decision support systems to reduce BSIs in athletes, military personnel, and other active individuals.

Modified Rotationplasty as a Composite Free Flap for Femur and Thigh Reconstruction.

Knee rotationplasty is a suitable reconstructive and limb salvage procedure for infected femur and knee prostheses. It involves external rotation of the lower limb with an intact neurovascular bundle to function as a knee joint. Functionally, it has better outcomes when compared to alternate options like above knee amputation. It results in better cortical reorganization and superior stance mechanics, enabling a more efficient gait and better quality of life. Here we report a 57-yr-old male who underwent modified rotationplasty for an infected knee endoprosthesis as a composite lower leg free flap.