Single-limb Stance Research Articles

Development and reliability testing of the Comprehensive High-Level Activity Mobility Predictor (CHAMP) in male servicemembers with traumatic lower-limb loss

The opportunity for wounded servicemembers (SMs) to return to high-level activity and return to duty has improved with advances in surgery, rehabilitation, and prosthetic technology. As a result, there is now a need for a high-level mobility outcome measure to assess progress toward high-level mobility during and after rehabilitation. The purpose of this study was to develop and determine the reliability of a new outcome measure called the Comprehensive High-Level Activity Mobility Predictor (CHAMP). The CHAMP consists of the Single Limb Stance, Edgren Side Step Test, T-Test, and Illinois Agility Test. CHAMP reliability was determined for SMs with lower-limb loss (LLL) (interrater: n = 118; test-retest: n = 111) and without LLL ( n = 97). A linear system was developed to combine the CHAMP items and produce a composite score that ranges from 0 to 40, with higher scores indicating better performance. Interrater and test-retest intraclass correlation coefficient values for the CHAMP were 1.0 and 0.97, respectively. A CHAMP score equal to or greater than 33 points is within the range for SMs without LLL. The CHAMP was found to be a safe and reliable measure of high-level mobility in SMs with traumatic LLL.

Alterations in Balance and Gait Characteristics in Community-Dwelling Elderly Subjects Following Hemi Hip-Arthroplasty Compared to Healthy Control Subjects

The objective of this study was to identify changes in balance and deviations in gait following hemi hip arthroplasty in 52 community-dwelling elderly individuals (n = 21) compared to healthy elderly subjects (n = 31). We assessed the outcome measures of balance (Berg balance scale) and gait parameters (temporal, spatial, and walking velocity). Those who received a hemi hip arthroplasty demonstrated poor balance (37.857 ± 8.673) compared to healthy elderly (52.484 ± 2.096). During gait, right and left single-limb stance time did not show differences, but double limb support time and cadence had significant differences (P < 0.001) between the groups. Hemi hip arthroplasty elderly had shorter step length (25.055 ± 4.045 cm) and shorter stride length (49.583 ± 8.054 cm) compared to healthy elderly (36.212 ± 9.620 and 72.722 ± 21.036 cm, respectively). Step height was less in those who received a hemi hip arthroplasty thank in healthy elderly. Walking velocity for the hemi hip arthroplasty group (28.690 ± 7.406 cm/sec) was 48.99% less (P < 0.001) than that in the healthy elderly group (58.557 ± 19.210). Effects of exercise on balance and gait parameters for subjects with hemi hip arthroplasty were not significant. Body mass index did not influence the balance and gait parameters. Progressive aging does influence walking velocity between hemi hip arthroplasty and healthy elderly. In conclusion, community-dwelling elderly with hemi hip arthroplasty had poor balance and reduced gait parameters (i.e., double limb support time, cadence, step length, stride length, step height, and walking velocity) compared to age-matched healthy control subjects.

The Effect of Boundary Shape and Minima Selection on Single Limb Stance Postural Stability

The effect of time-to-boundary minima selection and stability limit definition was investigated during eyes open and eyes closed condition single-limb stance postural stability. Anteroposterior and mediolateral time-to-boundary were computed using the mean and standard deviation (SD) of all time-to-boundary minima during a trial, and the mean and SD of only the 10 absolute time-to-boundary minima. Time-to-boundary with rectangular, trapezoidal, and multisegmented polygon defined stability limits were also calculated. Spearman's rank correlation coefficient test results revealed significant medium-large correlations between anteroposterior and mediolateral time-to-boundary scores calculated using both the mean and SD of the 10 absolute time-to-boundary minima and of all the time-to-boundary minima. Friedman test results revealed significant mediolateral time-to-boundary differences between boundary shape definitions. Follow-up Wilcoxon signed rank test results revealed significant differences between the rectangular boundary shape and both the trapezoidal and multisegmented polygon shapes during the eyes open and eyes closed conditions when both the mean and the SD of the time-to-boundary minima were used to represent postural stability. Significant differences were also revealed between the trapezoidal and multisegmented polygon definitions during the eyes open condition when the SD of the time-to-boundary minima was used to represent postural stability. Based on these findings, the overall results (i.e., stable versus unstable participants or groups) of studies computing postural stability using different minima selection can be compared. With respect to boundary shape, the trapezoid or multisegmented polygon shapes may be more appropriate than the rectangular shape as they more closely represent the anatomical shape of the stance foot.

The effect of contralateral pelvic drop and trunk lean on frontal plane knee biomechanics during single limb standing

Pelvic drop as a result of hip abductor weakness has been hypothesized as a potential modifier of frontal plane knee joint kinetics during gait in individuals with pathology such as knee osteoarthritis (OA). However, hip muscle strengthening interventions have failed to find significant reductions in frontal plane loading measures such as the external knee adduction moment (KAM) with altered hip strength. Since this could in part be due to a lack of change in pelvic kinematics between conditions or test sessions or due to alterations in lateral trunk lean angle, the relationship between pelvic drop and subsequent changes in centre of mass with knee joint loading remains unclear. The purpose of this study was to examine the effect of a consciously altered frontal plane centre of mass position (pelvic drop and trunk lean to the contralateral side) on the KAM during single limb standing. Twenty healthy individuals performed a series of single limb standing trials, where they were asked to balance on their dominant leg. KAM was assessed during single limb stance in two conditions: with pelvis and trunk maintained in a level position, and with contralateral pelvic drop. A third condition involving contralateral pelvic drop and trunk lean was assessed to examine exaggerated changes in centre of mass. The KAM increased significantly with contralateral pelvic drop (p=0.001) and with combined contralateral pelvic drop and trunk lean (p<0.001) compared to the level pelvis trials. These findings suggest that pelvic drop alone can significantly increase KAM magnitude, a risk factor for the progression of knee OA. Assessment of pelvic obliquity prior to treatment may allow those with marked pelvic drop to be targeted for hip muscle strengthening.

Coordination of the non-paretic leg during hemiparetic gait: Expected and novel compensatory patterns

BackgroundPost-stroke hemiparesis is usually considered a unilateral motor control deficit of the paretic leg, while the non-paretic leg is assumed to compensate for paretic leg impairments and have minimal to no deficits. While the non-paretic leg electromyography (EMG) patterns are clearly altered, how the non-paretic leg acts to compensate remains to be established. MethodsKinesiological data were recorded from sixty individuals with chronic hemiparesis (age: 60.9, SD=12.6years, 21 females, 28 right hemiparetic, time since stroke: 4.5years, SD 3.9years), divided into three speed-based groups, and twenty similarly aged healthy individuals (age: 65.1, SD=10.4years, 15 females). All walked on an instrumented split-belt treadmill at their self-selected speed and control subjects also walked at slower speeds matching those of the persons with hemiparesis. We determined the differences in magnitude and timing of non-paretic EMG activity relative to healthy control subjects in four pre-defined regions of stance phase of the gait cycle. FindingsIntegrated EMG activity and EMG timing in the non-paretic leg were different in many muscles. Multiple compensatory patterns identified included: increased EMG output when the muscle was typically active in controls and novel compensatory EMG patterns that appeared to provide greater propulsion or support with little evidence of impaired motor performance. InterpretationMost novel compensations were made possible by altered kinematics of the paretic and non-paretic leg (i.e., early stance plantarflexor activity provided propulsion due to the decreased advancement of the non-paretic foot) while others (late single limb stance knee extensor and late stance hamstring activity) appeared to be available mechanisms for increasing propulsion.

Biomechanical comparison of two stabilization techniques for unstable sacral fractures

AimThe purpose of the study was to assess the stability provided by an ilio-iliac dorsal plate fixation technique using an AO narrow DCP on the pelvic brim in vertically and rotationally unstable type-C pelvic ring injuries. Materials and methodsWe examined 12 fresh cadaver pelvises in a single limb stance load. A type-C pelvic ring injury (a type I lateral sacral fracture in the classification of Denis with symphysis pubis rupture) was performed on the cadaver specimen and fixed with a four-hole narrow dynamic compression plate to stabilize the symphysis pubis rupture; the sacrum fracture was stabilized either anteriorly with two 3-hole reconstruction plates (“anterior plate osteosynthesis”) or with a posterior fixation using a 12-hole narrow DCP. A cyclic load of between 100 and 250N was applied to the fifth lumbar vertebra of the specimen. An extensometer was attached to both sides of the sacrum fracture to detect movements at the fracture site. ResultsWe were able to achieve usable measurements in nine specimens. Three measurements were performed on each specimen, and the movements recorded at the fracture gap in trans-sacral plate fixation were higher than or similar to those observed for anterior plate synthesis in 23 out of 27 cases. ConclusionDorsal ilio-iliac bridge plate fixation provides somewhat reduced stability compared to anterior plate fixation, but the difference is not significant.

Patterns of inter-joint coordination during a single-limb standing

Past studies have documented contributions of multiple joints in maintaining a single-limb standing, but no reports on patterns of inter-joint coordination. It is also unknown whether such inter-joint coordination, if exists, depends on visual feedback. Eight health young volunteers took part in this study. The inter-joint coordination during a single-limb standing were examined using 3D joint kinematics. There were five testing trials with eyes open (EO) and five trials with eyes close (EC) conditions. During each trial the subject stood on the right leg on an even platform for 20s while 3D kinematic data was recorded. Recorded data was processed for an “adjusted coefficient of multiple determinations (ACMD)” to evaluate the inter-joint similarities in joint motions. Under both EO and EC conditions moderate to good similarities were found in axial rotation between the ankle and hip joints, and between ankle inversion/eversion and hip axial rotation. This pattern of the inter-joint coordination might be a unique feature of biomechanical configuration of the lower extremity. The significant increases in joint rotations but maintained inter-joint coordination from EO to EC condition may indicate a minimal influence of vision on the inter-joint coordination. Future studies to test patients with pathological conditions in single-limb stance need to examine any alternation/impairment of the inter-joint coordination pattern.

Biomechanical Study of 4-hole Pubic Symphyseal Plating: Locked Versus Unlocked Constructs

To the authors' knowledge, no published studies have examined the use of locking plates on injuries of the anterior pelvic ring. The purpose of this study was to determine whether locked plates provide enhanced stability in the treatment of pubic symphyseal disruptions. Completely unstable pelvic injuries were simulated in pelvic Sawbones (model 1301; Pacific Research Laboratories, Vashon, Washington) and 2 different fixation constructs used for anterior fixation (4-hole, 3.5-mm pubic symphysis plate with all locked or all unlocked screws). Adjunctive sacroiliac screw fixation with a single 7.3-mm screw placed into S1 was used in all specimens. Specimens were analyzed for motion at the pubic symphysis and sacroiliac joints using a Material Testing System (MTS Systems Corporation, Eden Prairie, Minnesota). Each specimen was subjected to compressive loading in a single-limb stance. Side loading was also examined. The main outcome measurement was motion at the pubic symphysis and sacroiliac joints and overall construct stiffness. No significant difference existed in overall construct stiffness between the 2 methods of pubic symphysis fixation. The motions at the pubic symphysis or injured sacroiliac joints were not significantly different. In addition, motion at the pubic symphysis joint with lateral load was not improved with a locking construct.No significant difference existed between 4-hole locked or unlocked constructs used for fixation of the pubic symphysis. No apparent advantage of locking screws exists for disruptions of the pubic symphysis, and recent reports have questioned the possibility of catastrophic failure.

Testing single and double limb standing balance performance: Comparison of COP path length evaluation between two devices

Center of pressure (COP) path length evaluation was commonly applied to measure postural sway and usually obtained from gold standard force plates. Thus, we comparatively investigated the feasible and less-expensive GKS® balance system (GKS) with the Kistler® force platform (KIS).34 non-specifically trained but active adults (14 males, 20 females, age: 25.4±4.8 years; weight: 69.3±12.3kg; height: 1.75±0.09m, sports activity: 5.8±3.6hours per week) were randomly tested on both devices during double and single limb stance with opened and closed eyes.Irrespective of the analysed time frame, repeated measures analyses of variances revealed higher path length readings for GKS compared to KIS for 30s (F=6.8, p=0.01) and 10s (F=21.2, p=0.001). Large effect sizes of the COP path length differences between GKS and KIS decreased from easy tasks (double limb, eyes open; d30-s=2.55, d10-s=2.04) to the most severe task (single limb, eyes closed; d30-s=0.02, d10-s=0.23). According to Bland and Altman, the limits of agreements indicated a high random variability component (between 29%, double limb, eyes open and 67%, single limb, eyes closed). The overall intraclass correlation coefficients (ICC) across all four standing balance tasks were moderate for the 30 s- (0.57) as well as the 10 s-analysis (0.65).In conclusion, the COP path length displacements obtained from the GKS balance system seem to differ with a considerable random variability from Kistler force platform data. Thus, measurements of the evaluated devices should not be used interchangeably. Further methodological investigations regarding balance measures seem warranted.

Validity and Reliability of Nintendo Wii Fit Balance Scores

Interactive gaming systems have the potential to help rehabilitate patients with musculoskeletal conditions. The Nintendo Wii Balance Board, which is part of the Wii Fit game, could be an effective tool to monitor progress during rehabilitation because the board and game can provide objective measures of balance. However, the validity and reliability of Wii Fit balance scores remain unknown. To determine the concurrent validity of balance scores produced by the Wii Fit game and the intrasession and intersession reliability of Wii Fit balance scores. Descriptive laboratory study. Sports medicine research laboratory. Forty-five recreationally active participants (age = 27.0 ± 9.8 years, height = 170.9 ± 9.2 cm, mass = 72.4 ± 11.8 kg) with a heterogeneous history of lower extremity injury. Participants completed a single-limb-stance task on a force plate and the Star Excursion Balance Test (SEBT) during the first test session. Twelve Wii Fit balance activities were completed during 2 test sessions separated by 1 week. Postural sway in the anteroposterior (AP) and mediolateral (ML) directions and the AP, ML, and resultant center-of-pressure (COP) excursions were calculated from the single-limb stance. The normalized reach distance was recorded for the anterior, posteromedial, and posterolateral directions of the SEBT. Wii Fit balance scores that the game software generated also were recorded. All 96 of the calculated correlation coefficients among Wii Fit activity outcomes and established balance outcomes were interpreted as poor (r < 0.50). Intrasession reliability for Wii Fit balance activity scores ranged from good (intraclass correlation coefficient [ICC] = 0.80) to poor (ICC = 0.39), with 8 activities having poor intrasession reliability. Similarly, 11 of the 12 Wii Fit balance activity scores demonstrated poor intersession reliability, with scores ranging from fair (ICC = 0.74) to poor (ICC = 0.29). Wii Fit balance activity scores had poor concurrent validity relative to COP outcomes and SEBT reach distances. In addition, the included Wii Fit balance activity scores generally had poor intrasession and intersession reliability.

Functional and Radiographic Outcomes of Intertrochanteric Hip Fractures Treated With Calcar Reduction, Compression, and Trochanteric Entry Nailing

Shortening after intertrochanteric hip fractures with sliding constructs is an increasingly recognized problem by the orthopaedic community. It often results in a limb length discrepancy causing maladaptation of the abductor lever arm. Functional limitations can also result from altered hip biomechanics and negatively influence patient outcomes. We hypothesized that with trochanteric entry nailing, calcar reduction, and intraoperative compression, a near-normal restoration of gait parameters and satisfactory outcomes can be achieved. Level 4, prospective descriptive study. Level 1 trauma care center. Fifty-eight patients with intertrochanteric hip fractures were managed operatively from 2007 to 2008. A strict exclusion criterion was used to analyze the data of interest for a final cohort of 30 patients. Stable fixation was achieved with trochanteric entry nail after calcar reduction and intraoperative compression of the fracture site. Patients were grouped into stable (n = 17) and unstable (n = 13) fracture types based on the OTA classification. OUTCOME/MEASUREMENTS: Postoperative collapse was measured as telescoping of the lag screw from lateral cortex and blade tip migration within the femoral head. Alteration in femoral head offset and abductor lever arm was measured at the last follow-up visit. Gait parameters were recorded and compared with contralateral side at 6-week, 3-, 6-, and 12-month follow-up visits. Functional outcomes were assessed through 36-item short form health survey (version 2) and Harris Hip Scores at 1 year. Fracture type (stable or unstable) significantly predicted telescoping (P = 0.007). Mean telescoping was 3.3 mm (SD = 2.41 mm) in the unstable group versus 1.2 mm (SD = 0.81 mm) in the stable group (P = 0.004). The stable group recovered 95% of the single limb stance versus 91% in the unstable group, at 1 year. (P = 0.02). Return of single limb stance improved from 76% to 95% between 6 weeks and 6 months. No improvement in gait was seen after 6 months (P > 0.05). The average scores on the physical and mental components of 36-item short form health survey and Harris Hip Scores were 44, 53, and 89, respectively. The radiographic union rate was 100%. There was 1 (3%) screw cutout that did not require a revision surgery in our series. There were no cases with implant failure, femur fracture, or any wound complications. Satisfactory functional outcomes with near-normal gait restoration can be achieved in cases of intertrochanteric hip fractures with an emphasis on calcar reduction and compression after fixation with trochanteric entry nail. Therapeutic Level IV. See page 128 for a complete description of levels of evidence.

Effects of a Proximal or Distal Tibiofibular Joint Manipulation on Ankle Range of Motion and Functional Outcomes in Individuals With Chronic Ankle Instability

Randomized clinical trial. To determine whether manipulation of the proximal or distal tibiofibular joint would change ankle dorsiflexion range of motion and functional outcomes over a 3-week period in individuals with chronic ankle instability. Altered joint arthrokinematics may play a role in chronic ankle instability dysfunction. Joint mobilization or manipulation may offer the ability to restore normal joint arthrokinematics and improve function. Forty-three participants (mean ± SD age, 25.6 ± 7.6 years; height, 174.3 ± 10.2 cm; mass, 74.6 ± 16.7 kg) with chronic ankle instability were randomized to proximal tibiofibular joint manipulation, distal tibiofibular joint manipulation, or a control group. Outcome measures included ankle dorsiflexion range of motion, the single-limb stance on foam component of the Balance Error Scoring System, the step-down test, and the Foot and Ankle Ability Measure sports subscale. Measurements were obtained prior to the intervention (before day 1) and following the intervention (on days 1, 7, 14, and 21). There was no significant change in dorsiflexion between groups across time. When groups were pooled, there was a significant increase (P<.001) in dorsiflexion at each postintervention time interval. No differences were found among the Balance Error Scoring System foam, step-down test, and Foot and Ankle Ability Measure sports subscale scores. The use of a proximal or distal tibiofibular joint manipulation in isolation did not enhance outcome effects beyond those of the control group. Collectively, all groups demonstrated increases in ankle dorsiflexion range of motion over the 3-week intervention period. These increases might have been due to practice effects associated with repeated testing. Therapy, level 2b-.

Altered Plantar-Receptor Stimulation Impairs Postural Control in Those With Chronic Ankle Instability

Postural control as assessed via time-to-boundary (TTB) measures has been shown to be impaired in those with chronic ankle instability (CAI). Foot orthotics have been shown to improve postural control, although it is not clear if this is via mechanical or sensorimotor mechanisms. To assess the effect of textured shoe inserts that provide no mechanical support on postural control as assessed by TTB measures in subjects with CAI. A crossover design to examine the effects of a textured insole on postural control in individuals with unilateral CAI. The independent variables were vision (eyes open, eyes closed) and texture (textured insole, sham insole, control). Laboratory. 20 physically active individuals, 12 men, 8 women, age 18-45 y (21.5 ± 5.51) with self-reported CAI. Each subject balanced in shod single-limb stance with eyes open and eyes closed under 3 conditions (control, sham, and textured insole). The order of testing under the 3 shoe conditions and 2 vision conditions was counterbalanced. The mean of TTB minima and the standard deviation of TTB minima in the mediolateral (ML) and anteroposterior directions. There were significant reductions in TTB ML magnitude and variability found in the textured condition compared with the control and sham conditions. In the textured condition, subjects failed significantly more trials than any other condition. Stimulating the plantar surface of the foot, via a textured insole, has an effect in the broad spectrum of postural-control maintenance in individuals with CAI.

Effects of Dual-Channel Functional Electrical Stimulation on Gait Performance in Patients with Hemiparesis

The study objective was to assess the effect of functional electrical stimulation (FES) applied to the peroneal nerve and thigh muscles on gait performance in subjects with hemiparesis. Participants were 45 subjects (age 57.8 ± 14.8 years) with hemiparesis (5.37 ± 5.43 years since diagnosis) demonstrating a foot-drop and impaired knee control. Thigh stimulation was applied either to the quadriceps or hamstrings muscles, depending on the dysfunction most affecting gait. Gait was assessed during a two-minute walk test with/without stimulation and with peroneal stimulation alone. A second assessment was conducted after six weeks of daily use. The addition of thigh muscles stimulation to peroneal stimulation significantly enhanced gait velocity measures at the initial and second evaluation. Gait symmetry was enhanced by the dual-channel stimulation only at the initial evaluation, and single-limb stance percentage only at the second assessment. For example, after six weeks, the two-minute gait speed with peroneal stimulation and with the dual channel was 0.66 ± 0.30 m/sec and 0.70 ± 0.31 m/sec, respectively (P < 0.0001). In conclusion, dual-channel FES may enhance gait performance in subjects with hemiparesis more than peroneal FES alone.

Finite element analysis of Puddu and Tomofix plate fixation for open wedge high tibial osteotomy

The use of open wedge high tibial osteotomy (HTO) to correct varus deformity of the knee is well established. However, the stability of the various implants used in this procedure has not been previously demonstrated. In this study, the two most common types of plates were analysed (1) the Puddu plates that use the dynamic compression plate (DCP) concept, and (2) the Tomofix plate that uses the locking compression plate (LCP) concept. Three dimensional model of the tibia was reconstructed from computed tomography images obtained from the Medical Implant Technology Group datasets. Osteotomy and fixation models were simulated through computational processing. Simulated loading was applied at 60:40 ratios on the medial:lateral aspect during single limb stance. The model was fixed distally in all degrees of freedom. Simulated data generated from the micromotions, displacement and, implant stress were captured. At the prescribed loads, a higher displacement of 3.25mm was observed for the Puddu plate model (p<0.001). Coincidentally the amount of stresses subjected to this plate, 24.7MPa, was also significantly lower (p<0.001). There was significant negative correlation (p<0.001) between implant stresses to that of the amount of fracture displacement which signifies a less stable fixation using Puddu plates. In conclusion, this study demonstrates that the Tomofix plate produces superior stability for bony fixation in HTO procedures.

Age-related loss of proximal femoral strength in elderly men and women: The Age Gene/Environment Susceptibility Study — Reykjavik

The risk of hip fracture rises rapidly with age, and is particularly high in women. This increase in fracture risk reflects both the age-related change in the risk of falling and decrements in the strength of the proximal femur. To better understand the extent to which proximal femoral density, structure and strength change with age as a function of gender, we have carried out a longitudinal analysis of proximal femoral volumetric quantitative computed tomographic (vQCT) images in men and women, analyzing changes in trabecular and cortical bone properties, and using subject-specific finite element modeling (FEM) to estimate changes in bone strength. In the AGES-Reykjavik Study vQCT scans of the hip were performed at a baseline visit in 2002–2006 and at a second visit 5.05±0.25years later. From these, 223 subjects (111 men, 112 women, aged 68–87years) were randomly selected. The subjects were evaluated for longitudinal changes in three bone variables assessed in a region similar to the total femur region quantified by DXA: areal bone mineral density (aBMD), trabecular volumetric bone mineral density (tBMD) and the ratio of cortical to total tissue volume (cvol/ivol). They were also evaluated for changes in bone strength using FEM models of the left proximal femur. Models were analyzed under single-limb stance loading (FStance), which approximates normal physiologic loading of the hip, as well as a load approximating a fall onto the posterolateral aspect of the greater trochanter (FFall). We computed five-year absolute and percentage changes in aBMD, tBMD, cvol/ivol, FFall and FStance. The Mann–Whitney Test was employed to compare changes in bone variables between genders and the Wilcoxon Signed Rank Test was used to compare changes in bone strength between loading conditions. Multiple (linear) regression was employed to determine the association of changes in FFall and FStance with baseline age and five-year weight loss. Both men and women showed declines in indices of proximal femoral density and structure (aBMD: men −3.9±6.0%, women −6.1±6.2%; tBMD: men −14.8±20.3%, women −23.9±26.8%; cvol/ivol: men −2.6±4.6%, women −4.7±4.8%, gender difference: p<0.001). Both men and women lost bone strength in each loading condition (FStance: men −4.2±9.9%, women −8.3±8.5%; FFall: men −7.0±15.7%, women −12.8±13.2%; all changes from baseline p<0.0001). The gender difference in bone strength loss was statistically significant in both loading conditions (p<0.001 for FStance and P<0.01 for FFall) and FFall was lost at a higher rate than FStance in men (p<0.01) and women (p<0.0001). The gender difference in strength loss was statistically significant after adjustment for baseline age and weight loss in both loading conditions (p<0.01). In these multi-linear models, men showed increasing rates of bone loss with increasing age (FFall: p=0.002; FStance: p=0.03), and women showed increasing bone strength loss with higher degrees of weight loss (FStance: p=0.003). The higher loss of FFall compared to FStance supports previous findings in animal and human studies that the sub-volumes of bone stressed under normal physiologic loading are relatively better protected in aging. The gender difference in hip bone strength loss is consistent with the higher incidence of hip fracture among elderly women.

Associations Between Single-Leg Postural Control and Drop-Landing Mechanics in Healthy Women

Impaired postural control in single-limb stance and aberrant drop-landing mechanics have been implicated separately as risk factors for noncontact anterior cruciate ligament (ACL) injury, but associations between these variables has not been reported. To determine whether there are associations between single-limb postural control and drop-landing mechanics. University motion-analysis laboratory. Single-leg-landing kinematic and kinetic data were collected after participants dropped from a hang bar. Postural-control variables COP excursion and velocity were assessed during single-leg barefoot standing on a force platform. A convenience sample of 24 healthy women. Pearson product-moment correlation coefficients. Strong associations were measured between maximal knee-abduction moment and COP excursion (r = .529, P = .003) and average COP velocity (r = .529, P = .003). Strong inverse associations were measured between minimum hip-flexion angle and COP excursion (r = -.521, P = .003) and average COP velocity (r = -.519, P = .003). Participants with decreased postural control had higher knee-abduction moments and a more extended hip on landing, which have been implicated separately as risk factors for ACL injury. A longitudinal prospective analysis is needed to determine whether force-platform postural-control measures can identify athletes at risk for ACL injury.

Relationships between motor function and gait-related dual-task interference after stroke: A pilot study

The purpose of this pilot study was to examine the relationships between motor performance measures and dual-task interference in gait among community-dwelling adults with stroke. Dual-task costs on gait were correlated with Fugl-Meyer lower extremity score and usual gait speed in 13 community-dwelling adults with stroke. Individuals with greater lower extremity motor impairment and slower gait speed experienced greater cognitive-motor interference in gait. Paretic single limb stance was particularly susceptible to dual-task interference. Gait speed was only vulnerable to dual-task interference in the most complex dual-task. Thus, global characteristics of gait were vulnerable in the most difficult cognitive tasks, but even easy tasks impaired discrete components of dynamic balance.

Spatial postural control alterations with chronic ankle instability

Postural control deficits have been identified among individuals with chronic ankle instability (CAI) compared to healthy controls. Although deficits in static balance have previously been reported using center of pressure (COP) and, more recently, time to boundary (TTB) measures, the underlying mechanism behind these deficits warrants further investigation. It is unclear if there are differences in the spatial distribution of COP and TTB minima data points under the foot. Our purpose was to determine if there are differences in the location of the distribution of the COP and the TTB minima data points between groups with and without CAI. Fifty healthy and 61 CAI subjects participated in this case–control study. The subjects performed three successful 10-s trials of quiet single limb stance on a force plate with eyes-open and -closed conditions. Results showed that during eyes-open trials, the CAI group exhibited more COP and TTB minima data points on the anterolateral aspect of the foot compared to controls. With eyes-closed single limb balance, the CAI group demonstrated significantly more COP and TTB minima data points anterior to the horizontal midline of the foot compared to controls. Overall, the CAI group showed a greater anterior displacement of COP and TTB minima during single limb static stance compared to controls. This alteration may result from the CAI subjects adopting a more dorsiflexed position in an effort to keep the ankle in a more stable, closed pack position and limiting the available degrees of freedom in the distal lower extremity.

Differential Ability of Selected Postural-Control Measures in the Prediction of Chronic Ankle Instability Status

Chronic ankle instability (CAl) is a term used to identify a condition associated with recurrent ankle sprains and persistent symptoms. Balance deficits, evaluated using center-of-pressure (COP) force-plate measurements, have been shown to occur in people with CAl. To determine the differential abilities of selected force-plate postural-control measures to assess CAl. Case-control study. Laboratory. A total of 63 individuals with CAl (30 men, 33 women: age= 22.3± 3.7 years, height= 169.8 ±9.6 cm, mass= 70.7± 14.3 kg) and 46 healthy controls (22 men, 24 women: age= 21.2± 4.1 years, height= 173.3± 9.2 cm, mass =69.2± 13.2 kg) volunteered. Participants performed 3 10-second trials of quiet, single-limb stance on a force plate under 2 conditions: eyes open and eyes closed. Measures of COP area, COP velocity, COP SO, COP range of excursion, percentage of COP range used, time-to-boundary absolute minimum, time-to-boundary mean of the minima, and time-to-boundary SO of the minima were calculated. All measures with the exception of COP area were calculated in both the mediolateral (ML) and anteroposterior directions. For each measure, a receiver operator curve analysis was created, and the corresponding area under the curve was tested. The optimal diagnostic threshold value for each measure was determined, and the corresponding positive and negative likelihood ratios were calculated. Three eyes-closed, single-limb force-plate measures (COP ML SO, ML percentage of COP range used, and time-to-boundary absolute minimum) predicted CAl status. However, all 3 measures had positive likelihood ratios associated with only small shifts in the probability of a patient with a positive test having CAl and negative likelihood ratios associated with very small shifts in the probability of a patient with a negative test not having CAl. No single force-plate measure was very effective in predicting if an individual had CAl or not.