Lower extremity mechanical work during stance phase of running partially explains interindividual variability of metabolic power

Recent attention given to the mechanical work of the lower extremity joints, the emerging importance of the stance phase of running, and the lack of consensus regarding the biomechanical correlates to economical running were primary justifications for this study. The purpose of this experiment was to identify the correlations between metabolic power and the positive and negative mechanical work at lower extremity joints during stance. Recreational runners (n = 16) ran on a treadmill at 3.35 m s⁻¹ for physiological measures and overground for biomechanical measures. Inverse dynamics were used to calculate net joint moments and powers at the ankle, knee, and hip. Joint powers were then integrated over the stance phase so that positive and negative joint mechanical work were correlated with metabolic power (r = 0.60–0.69). Positive work at the hip and ankle during stance was positively correlated to metabolic power. In addition to these results, more economical runners (lower metabolic power) exhibited greater negative work at the hip, greater positive work at the knee, and less negative work at the ankle. Between the most and least economical runners, different mechanical strategies were present at the hip and knee, whereas the kinetics of the ankle joint differed only in magnitude.     

Fixed patterns of rapid postural responses among leg muscles during stance

Summary The aim of this study has been to present firmer evidence that during stance functionally related postural muscles in the legs are activated according to fixed patterns. The importance of fixed patterns of activation for stabilization, balance, and movement control has received considerable theoretical and experimental attention. With regard to postural adjustment in humans, however, evidence for fixed activation patterns has been circumstantial only. Previous studies could not rule out the possibility that fixed patterns were caused by the mechanical coupling of rotatory movements among the joints of the body.This study has shown that in subjects employing FSR adjustments during stance activation patterns among leg muscles at FSR latency (functional stretch response, 100–120 msec) are preprogrammed prior to a response and are, on the average, fixed, independent of the associated motions among the ankle, knee, and hip joints. The identical fixed patterns were produced by sway rotation about the ankle joints and by direct rotation of the ankles. A pattern was characterized as fixed when, during a 1 hr session, the ratios of estimated force between pairs of functionally related leg muscles remained constant. In addition, the sequence of activation among muscles was fixed and followed a course beginning at the ankle muscle and proceeding proximally.The discussion of these results considered the functional implications of fixed contractile patterns during stance posture control.     

The dynamics of postural sway cannot be captured using a one-segment inverted pendulum model: a PCA on segment rotations during unperturbed stance

Research on unperturbed stance is largely based on a one-segment inverted pendulum model. Recently, an increasing number of studies report a contribution of other major joints to postural control. Therefore this study evaluates whether the conclusions originating from the research based on a one-segment model adequately capture postural sway during unperturbed stance. High-pass filtered kinematic data (cutoff frequency 1/30 Hz) obtained over 3 min of unperturbed stance were analyzed in different ways. Variance of joint angles was analyzed. Principal-component analysis (PCA) was performed on the variance of lower leg, upper leg, and head-arms-trunk (HAT) angles, as well as on lower leg and COM angle (the orientation of the line from ankle joint to center of mass). It was found that the variance in knee and hip joint angles did not differ from the variance found in the ankle angle. The first PCA component indicated that, generally, the upper leg and HAT segments move in the same direction as the lower leg with a somewhat larger amplitude. The first PCA component relating ankle angle variance and COM angle variance indicated that the ankle joint angle displacement gives a good estimate of the COM angle displacement. The second PCA component on the segment angles partly explains the apparent discrepancy between these findings because this component points to a countermovement of the HAT relative to the ankle joint angle. It is concluded that postural control during unperturbed stance should be analyzed in terms of a multiple inverted pendulum model.     

Dynamic transitions in stance support accompanying leg flexion movements in man

Summary The control processes underlying dynamic transitions in stance support during single leg flexion movements were investigated in human subjects as a function of the intended speed of movement, by examining the vertical and lateral horizontal components of the ground reaction forces, the frontal plane trajectory of the body center of mass (CM) recorded via motion analysis, and the electromyographic (EMG) recordings of selected lower limb muscles. For the slowest movements, the measured vertical force beneath the flexing and single stance limbs closely matched the vertical force-time history predicted by a quasi-static mechanical model, whereas, the more rapid natural and fast speeds showed progressively larger discrepancies between measured and predicted forces. The initial resultant horizontal force component was exerted in the flexing to stance limb direction but was proportionately greater (41) beneath the flexing versus the stance limb during fast and natural speeds, and became equivalent for slow movements. Speed related EMG differences included an early phasic recruitment of the lateral hip muscle of the flexing limb which always preceded the ground reaction force changes for fast and natural but not slow movements, and a considerably earlier onset of the stance leg knee extensor relative to the flexing limb knee flexor for slow versus fast and natural speeds. Overall, the findings suggested two different speed related strategies for linking the postural and intentional movement components, where the choice of the strategy selected appeared to reflect the mechanical requirements needed to overcome the inertial force of the body mass during transitions from bipedal to single limb stance support.     

Evaluation of hindfoot and knee alignment by the hip-to-calcaneus view in patients with knee osteoarthritis and healthy individuals

BackgroundHip-to-calcaneus (HC) view is a whole-leg standing view that can visualize the hindfoot in detail. The aim of this study was to investigate the reliability and validity of tibiocalcaneal angle in HC view (H-TCA) by comparing it with that in long axial view (L-TCA). We also verified whether periarticular knee alignment parameters, measured conventionally in whole-leg standing radiography, could be measured in HC view.MethodSixty healthy volunteers and 61 patients with medial knee osteoarthritis were included. H-TCA was measured by two examiners in the healthy group, and intra-class correlation coefficients (ICCs) were evaluated. H-TCA and L-TCA were then measured in the healthy and osteoarthritis groups and correlated. Finally, we measured hip–knee–ankle angle, mechanical axis deviation ratio, mechanical lateral distal femoral angle, medial proximal tibial angle, and joint-line convergence angle in HC view and conventional whole-leg standing radiography to evaluate statistical differences and correlations.ResultsThe intra-observer and inter-observer ICCs were 0.86 and 0.76, respectively. Correlation coefficients (r) between H-TCA and L-TCA were r = 0.87 in healthy group and r = 0.81 in osteoarthritis group, indicating a strong positive correlation in both groups. There was no significant difference in periarticular knee alignment parameters between HC view and conventional whole-leg radiography.ConclusionsHindfoot evaluation in HC view showed high intra-observer and inter-observer reliabilities and strong positive correlation with TCA in long axial view. By using HC view before knee surgery, such as total knee arthroplasty, other necessary alignments can be evaluated simultaneously.     

Underestimation of varus angulation in knees with flexion deformity

In order to investigate the change in limb alignment in cases of knee flexion deformity, 17 male volunteers aged from 25 to 35 years with no complaints and no knee disorders were selected. The femorotibial angle (FTA), which is the lateral angle at the intersection between the femoral axis and the tibial axis in an anteroposterior radiograph, was employed as an index of limb alignment. FTA in standing on one leg with and without knee flexion was measured. The mean standing FTA was 179.4±19° in full extension, which decreased to 176.9±2.5° in a mean flexion position of 18±3.3° (range 15–25°) (P<0.002), and in all cases, standing FTA in flexion was smaller (more valgus-angulated) than that in full extension. There was a significant positive relationship with a straight regression line (D=0.101KFA+0.296, R=0.8505) between the angle of knee flexion (KFA) and the difference (D) in standing FTA between full extension and knee flexion. We conclude that limb alignment became more valgus-angulated with an increase in flexion deformity.     

Coherence analysis of muscle activity during quiet stance

Studies of muscle activation during perturbed standing have demonstrated that the typical patterns of coordination (“ankle strategy” and “hip strategy”) are controlled through multiple muscles activated in a distal-to-proximal or proximal-to-distal temporal pattern. In contrast, quiet stance is thought to be maintained primarily through the ankle musculature. Recently, spectral analysis of inter-segment body motion revealed the coexistence of both ankle and hip patterns of coordination during quiet stance, with the predominating pattern dependent on the frequency of body sway. Here we use frequency domain techniques to determine if these patterns are associated with the same muscular patterns as observed during perturbed stance. Six of the seven muscles measured showed a linear relationship to the sway of at least one body segment, all being leg muscles. Muscle–segment phases were consistent with that required to resist gravity at low frequencies, with increasing phase lag as frequency increased. Visual information had effects only at frequencies below 0.5 Hz, where the shift from in-phase to anti-phase trunk–leg co-phase was observed. These results indicate that co-existence of the ankle and hip pattern during quiet stance involves only leg musculature. Anti-phase movement of the trunk relative to the legs at higher frequencies arises from indirect biomechanical control from posterior leg muscles.     

Double-level osteotomy for severe varus osteoarthritic knees can prevent change in leg length and restore physiological joint geometry

BackgroundIt is unclear whether double-level osteotomy (DLO) combining closed-wedge osteotomy in the distal femur and open-wedge osteotomy in the proximal tibia deformity can prevent change in leg length and excessive coronal inclination of the tibial articular surface in surgical correction of the severe varus knee. The purpose of this study was to examine the postoperative change in leg length as well as radiological and clinical outcomes following DLO compared with the results obtained from knees undergoing isolated open-wedge high tibial osteotomy (OW-HTO).MethodsIn cases of severe varus knee deformity (hip–knee–ankle angle (HKA) > 10°) 29 patients undergoing DLO and 35 patients undergoing OW-HTO were included. If the predicted mechanical medial proximal tibial angle (mMPTA) was 95° or greater or the wedge size was 15 mm or greater in the surgical simulation, then DLO was considered as the surgical of option. In cases where these criteria were not met, OW-HTO was selected. All patients were followed up for a minimum of 2 years.ResultsThe changes in the length of the whole leg in the DLO and OW-HTO groups averaged 2.3 ± 4.8 mm and 9.3 ± 7.2 mm, respectively (P < 0.001). mMPTA of more than 95° was found in no knee in the DLO group.ConclusionsThis study showed that DLO could avoid leg length change and non-physiologic joint lines when performed in patients with varus HKA > 10°, and the predicted mMPTA was 95° or greater or the wedge size was 15 mm or greater in the surgical simulation.     

Genu varum and football participation: Does football participation affect lower extremity alignment in adolescents?

BackgroundGenu varum is one of the most common anatomical variations of knee alignment which is considered a risk factor for anterior knee pain and anterior cruciate ligament injury among football players. Considering that millions of children participate in high-level football training, the purpose of this study was to determine the genu varum development in adolescent football players and non-athlete peers. The hypothesis of this study was that genu varum incidence was higher in adolescent football players compared with non-athletic peers.MethodsThe design was a cross-sectional study. Two-hundred and thirty-seven male football players (FG) and aged-matched and anthropometrically similar non-athletes (CG) were recruited into the study. The quadriceps angle and intercondylar–intermalleolar distance were measured to evaluate the leg alignment. The distance between the medial edges of the condyles and malleoli was measured in millimeters using a digital caliper while angle measurements were performed using a photographic technique in a standing position. To analyze the variables, comparison, correlation and regression statistical tests were performed.ResultsThe intercondylar–intermalleolar distance and quadriceps angle values were significantly higher in FG than CG in all ages. In FG, a very strong correlation was found between number of training years and the intercondylar–intermalleolar distance. The prevalence of genu varum was markedly higher in FG than CG (~37% vs. 2%, respectively) based on intercondylar–intermalleolar distance.ConclusionThis study determined that the prevalence of genu varum and abnormal quadriceps angles in adolescent football players is significantly higher compared with their non-athletic peers.     

The value of the intra-operative clinical mechanical axis measurement in open-wedge valgus high tibial osteotomies

IntroductionIn high tibial osteotomies (HTO) the correction needs to be precise and intra-operative assessment is essential. The purpose of this study was to evaluate the use of the intra-operative clinical mechanical axis measurement and compare it to the post-operative weight bearing situation on standing whole leg radiographs (WLR). Secondly, we evaluated the preoperative planned wedge size and compared it to the final results in 27 HTOs.MethodsThe mechanical axis deviation (MAD), expressed as a percentage of the tibial width (0% is medial edge, 100% is lateral edge) and the hip–knee–ankle angle (HKA) were calculated and analyzed. Preoperative planning was done by projecting the desired mechanical axis on the lateral tibial spine on the WLR and subsequently calculating the necessary correction angle. A 3° valgus correction was desired.ResultsThe results showed a preoperative standing MAD of 26.6%, or about halfway the medial tibial plateau. The MAD was corrected to 57.0% intra-operative, meaning a slight valgus. On the postoperative standing WLR, the MAD had shifted significantly to 62.0% (95% CI = ? 9.2 to ? 2.7; p < 0.01) compared to the intra-operative 57.0% axis. The HKA angle changed 8.2° from 5.1° varus preoperative to 3.1° valgus postoperative.ConclusionWhen aiming the mechanical axis at the lateral tibial spine, a slight undercorrection was introduced, but due to a valgus shift while weight bearing, a satisfying final outcome of 3° valgus average was achieved. Preoperative calculation of the wedge size remains important for surgical planning, but it does not always correspond to the actual used wedge size.     

A new approach for detection of leg movement using segmental electrical impedance changes

The purpose of this paper is to provide a new approach for detection using bio-impedance. This impedance is measured by the four-electrode method. As the impedance changes resulting from ankle, knee, and hip movements depend on electrode placement, we determined the optimal electrode configurations for these movements by searching for high correlation coefficients, large impedance changes, and minimum interference in ten subjects (age: 20?±?4). Our optimal electrode configurations showed very strong relationships between the ankle joint angle and ankle impedance (γ?=???0.913?±?0.03), between the knee joint angle and knee impedance (γ?=?0.944?±?0.02), and between the hip joint angle and hip impedance (γ?=?0.823?±?0.08). This study showed that lower leg movement could be easily measured by the impedance measurement system with two pairs of skin electrodes.     

Asymptomatic Genu Recurvatum reshapes lower limb sagittal joint and elevation angles during gait at different speeds

BackgroundKinematic characteristics of walking with an asymptomatic genu recurvatum are currently unknown. The objective of this study is to characterize the lower limb sagittal joint and elevation angles during walking in participants with asymptomatic genu recurvatum and compare it with control participants without knee deformation at different speeds.MethodsThe spatio-temporal parameters and kinematics of the lower limb were recorded using an optoelectronic motion capture system in 26 participants (n = 13 with genu recurvatum and n = 13 controls). The participants walked on an instrumented treadmill during five minutes at three different speeds: slow, medium and fast.ResultsParticipants with genu recurvatum showed several significant differences with controls: a narrower step width, a greater maximum hip joint extension angle, a greater knee joint extension angle at mid stance, a lower maximum knee joint flexion angle during the swing phase, and a greater ankle joint extension angle at the end of the gait cycle. Participants with genu recurvatum had a greater minimum thigh elevation angle, a greater maximum foot elevation angle, and a change in the orientation of the covariance plane. Walking speed had a significant effect on nearly all lower limb joint and elevation angles, and covariance plane parameters.ConclusionOur findings show that genu recurvatum reshapes lower limb sagittal joint and elevation angles during walking at different speeds but preserves the covariation of elevation angles along a plane during both stance and swing phases and the rotation of this plane with increasing speed.     

Determinant of leg stiffness during hopping is frequency-dependent

Identifying the major determinant of leg stiffness during hopping would be helpful in the development of more effective training methods. Despite the fact that overall leg stiffness depends on a combination of the joint stiffness, it is unclear how the major determinants of leg stiffness are influenced by hopping frequency. The purpose of this study was to identify the major determinant of leg stiffness over a wide range of hopping frequencies. Fourteen well-trained male athletes performed in a place hopping on two legs, at three frequencies (1.5, 2.2 and 3.0 Hz). We determined leg and joint stiffness of the hip, knee and ankle from kinetic and kinematic data. Multiple linear regression analysis revealed that knee stiffness could explain more of the variance of leg stiffness than could ankle or hip stiffness at 1.5 Hz hopping. Further, only ankle stiffness was significantly correlated with leg stiffness at both 2.2 and 3.0 Hz, and the standardized regression coefficient of ankle stiffness was higher than that of knee and hip stiffness. The results of the present study suggest that the major determinant of leg stiffness during hopping switches from knee stiffness to ankle stiffness when the hopping frequency is increased.     

A new approach for detection of leg movement using segmental electrical impedance changes

The purpose of this paper is to provide a new approach for detection using bio-impedance. This impedance is measured by the four-electrode method. As the impedance changes resulting from ankle, knee, and hip movements depend on electrode placement, we determined the optimal electrode configurations for these movements by searching for high correlation coefficients, large impedance changes, and minimum interference in ten subjects (age: 20 +/- 4). Our optimal electrode configurations showed very strong relationships between the ankle joint angle and ankle impedance (gamma = - 0.913 +/- 0.03), between the knee joint angle and knee impedance (gamma = 0.944 +/- 0.02), and between the hip joint angle and hip impedance (gamma = 0.823 +/- 0.08). This study showed that lower leg movement could be easily measured by the impedance measurement system with two pairs of skin electrodes.     

Resorbability of rigid beta-tricalcium phosphate wedges in open-wedge high tibial osteotomy: a retrospective radiological study

The open-wedge high tibial osteotomy (OWHTO) is a well accepted treatment modality for patients with osteoarthritis of the medial compartment associated with genu varum. To fill in the osteotomy gap 30% macroporosity rigid beta-tricalcium phosphate (β-TCP) is frequently used as a stable resorbable bone substitute. However, the resorbability of these β-TCP wedges is not known. The aim of this study was to investigate this.

Twenty-one OWHTO procedures in seventeen patients were performed with the use of 30% macroporosity rigid β-TCP wedges. The osteotomies were fixed using an angle-stable locking plate. Conventional AP and lateral radiographs were examined in order to assess the resorbability of the 30% macroporosity rigid β-TCP wedges as a function of time. A radiological classification system consisting of five phases was used to monitor the resorption of the 30% macroporosity rigid β-TCP wedges. The mean duration of follow-up was 62 months (± 23 range of 28–99).

In all 21 cases, remnants of the 30% macroporosity rigid β-TCP wedges were still present at maximum follow-up. Although the boundaries between 30% macroporosity rigid β-TCP wedges and bone remained slightly visible, all osteotomies were completely consolidated and full osseointegration took place. In 16 out of 21 knees the fixation system was removed after a mean duration of 32 months (± 19 range of 6–62). In six out of 21 knees a conversion to a knee arthroplasty was performed after a mean duration of 56 months (± 18 range of 37–82). The OWHTO did not interfere with the placement of knee prostheses.

Complete resorption of 30% macroporosity rigid β-TCP wedges did not take place up to 8 years after operation.     

Adaptation of the walking pattern to uphill walking in normal and spinal-cord injured subjects

 Lower-limb movements and muscle-activity patterns were assessed from seven normal and seven ambulatory subjects with incomplete spinal-cord injury (SCI) during level and uphill treadmill walking (5, 10 and 15°). Increasing the treadmill grade from 0° to 15° induced an increasingly flexed posture of the hip, knee and ankle during initial contact in all normal subjects, resulting in a larger excursion throughout stance. This adaptation process actually began in mid-swing with a graded increase in hip flexion and ankle dorsiflexion as well as a gradual decrease in knee extension. In SCI subjects, a similar trend was found at the hip joint for both swing and stance phases, whereas the knee angle showed very limited changes and the ankle angle showed large variations with grade throughout the walking cycle. A distinct coordination pattern between the hip and knee was observed in normal subjects, but not in SCI subjects during level walking. The same coordination pattern was preserved in all normal subjects and in five of seven SCI subjects during uphill walking. The duration of electromyographic (EMG) activity of thigh muscles was progressively increased during uphill walking, whereas no significant changes occurred in leg muscles. In SCI subjects, EMG durations of both thigh and leg muscles, which were already active throughout stance during level walking, were not significantly affected by uphill walking. The peak amplitude of EMG activity of the vastus lateralis, medial hamstrings, soleus, medial gastrocnemius and tibialis anterior was progressively increased during uphill walking in normal subjects. In SCI subjects, the peak amplitude of EMG activity of the medial hamstrings was adapted in a similar fashion, whereas the vastus lateralis, soleus and medial gastrocnemius showed very limited adaptation during uphill walking. We conclude that SCI subjects can adapt to uphill treadmill walking within certain limits, but they use different strategies to adapt to the changing locomotor demands. Received: 10 March 1998 / Accepted: 29 December 1998     

Three-dimensional assessment of lower limb alignment: Reference values and sex-related differences

BackgroundThree-dimensional (3D) preoperative planning and assisted surgery is increasingly popular in deformity surgery and arthroplasty. Reference ranges for 3D lower limb alignment are needed as a prerequisite for standardized analysis of alignment and preoperative planning in 3D, but are not yet established.MethodsOn 60 3D bone models of the lower limbs based on computed tomography data, fifteen parameters per leg were assessed by standardized validated 3D analysis. Distribution parameters and differences between sexes were evaluated. Reference values were generated by adding/subtracting one standard deviation from the mean.ResultsWomen had a significantly lower mean mechanical lateral distal femoral angle compared with men (86.4 ± 2.1° vs. 87.8 ± 2.0°; P < .05) and significantly lower mean joint line convergence angle (−2.5 ± 1.4° vs. -1.3 ± 1.2; P < .01), but higher mean hip knee ankle angle (178.9 ± 1.9° vs. 177.8 ± 2.3°; P < .05) and mean femoral torsion (18.2 ± 9.5° vs. 13.2 ± 6.4°; P < .05), resulting in a tendency towards valgus alignment and vice versa for men. Differences in mean medial proximal tibial angle were not significant. The mean mechanical axis deviation from the tibial knee joint center was 6.9 ± 7.3 mm medial and 1.4 ± 16.1 mm ventral without significant differences between sexes.ConclusionsWe describe total and sex-related reference ranges for all alignment relevant axes and joint angles of the lower limb. There are sex-related differences in certain alignment parameters, which should be considered in analysis and surgical planning.     

Post-effect of forward and backward locomotion on body orientation in space during quiet stance

Neural circuits responsible for stance control serve other motor tasks as well. We investigated the effect of prior locomotor tasks on stance, hypothesizing that postural post-effects of walking are dependent on walking direction. Subjects walked forward (WF) and backward (WB) on a treadmill. Prior to and after walking they maintained quiet stance. Ground reaction forces and centre of foot pressure (CoP), ankle and hip angles, and trunk inclination were measured during locomotion and stance. In WF compared to WB, joint angle changes were reversed, trunk was more flexed, and movement of CoP along the foot sole during the support phase of walking was opposite. During subsequent standing tasks, WB induced ankle extension, hip flexion, trunk backward leaning; WF induced ankle flexion and hip extension. The body CoP was displaced backward post-WB and forward post-WF. The post-effects are walking-direction dependent, and possibly related to foot-sole stimulation pattern and trunk inclination during walking.     

Identification of the plant for upright stance in humans: multiple movement patterns from a single neural strategy

We determined properties of the plant during human upright stance using a closed-loop system identification method originally applied to human postural control by another group. To identify the plant, which was operationally defined as the mapping from muscle activation (rectified EMG signals) to body segment angles, we rotated the visual scene about the axis through the subject's ankles using a sum-of-sines stimulus signal. Because EMG signals from ankle muscles and from hip and lower trunk muscles showed similar responses to the visual perturbation across frequency, we combined EMG signals from all recorded muscles into a single plant input. Body kinematics were described by the trunk and leg angles in the sagittal plane. The phase responses of both angles to visual scene angle were similar at low frequencies and approached a difference of approximately 150 degrees at higher frequencies. Therefore we considered leg and trunk angles as separate plant outputs. We modeled the plant with a two-joint (ankle and hip) model of the body, a second-order low-pass filter from EMG activity to active joint torques, and intrinsic stiffness and damping at both joints. The results indicated that the in-phase (ankle) pattern was neurally generated, whereas the out-of-phase pattern was caused by plant dynamics. Thus a single neural strategy leads to multiple kinematic patterns. Moreover, estimated intrinsic stiffness in the model was insufficient to stabilize the plant.     

Knee skin temperature following uncomplicated total knee replacement

This prospective study aimed to establish the pattern of knee skin temperature following uncomplicated primary total knee replacement. Thirty-two patients were included. The skin temperature of operated and contralateral knees was measured preoperatively and daily during the first 6 weeks postoperatively. Measurements were also taken at 3, 6, 12 and 24 months following surgery. The difference in temperature between the two knees had a mean value of + 2.9 °C at 7 days. This mean value decreased to + 1.6 °C at 6 weeks, + 1.3 °C at 3 months, + 0.9 °C at 6 months + 0.3 °C at 12 months and + 0.0 °C at 24 months. Following uncomplicated total knee replacement, the operated knee skin temperature increases compared to the contralateral knee. The difference decreases gradually but remains statistically significant up to at least 6 months following surgery. In the absence of other features of infection, local knee warmth should not cause concern.