Erratum: Validity of estimating center of pressure during walking and running with plantar load from a three-sensor wireless insole - ERRATUM.

[This corrects the article DOI: 10.1017/wtc.2022.5.].

The effect of total ankle arthroplasty on mechanical energy exchange.

Total ankle arthroplasty (TAA) is a common surgical solution for patients with debilitating arthritis of the ankle. Prior to surgery patients experience high levels of pain and fatigue and low mechanical energy recovery. It is not known if TAA restores healthy levels of mechanical energy recovery in this patient population. This study was designed to determine whether mechanical energy recovery was restored following TAA. Ground reaction forces during self-selected speed walking were collected from patients with symptomatic, unilateral ankle arthritis (N = 29) before and one and two years after primary, unilateral TAA. The exchange of potential (PE) and kinetic (KE) energy was examined, and direction of change (%congruity) and energy exchange (%recovery) between the two curves was calculated, with those subjects with low congruity experiencing high energy recovery. Linear regressions were used to examine the impact of walking speed, congruity, and amplitude of the center of mass (COM) displacement on %recovery, while ANOVA and ANCOVA models were used to compare energy recovery and congruity across the three time points. Gender, BMI, and age at surgery had no effect in this study. TAA improved walking speed (p = 0.001), increased energy recovery (p = 0.020), and decreased congruity (p = 0.002), and these levels were maintained over at least two years. Differences in congruity were independent of walking speed. In some patients, especially those who are severely debilitated by ankle arthritis, TAA is effective in restoring mechanical energy recovery to levels similar to an asymptomatic population of a similar age recorded by other studies.

Characterizing upper extremity kinematics in typically developing children during box and blocks test.

Upper extremity kinematics are important for understanding functional ability and performance improvements. The Box and Blocks test (BBT) is a standardized functional test used to measure manual dexterity when evaluating children or patients following a stroke. The BBT measures the number of blocks moved in one minute and therefore, kinematic measures and compensatory strategies cannot be assessed. This study examined the correlation between upper extremity kinematics and cycle time per block movement during the BBT in three age groups (7-, 9-, and 11-year-olds). Participants completed one BBT session while test scores and kinematic measures (hand velocity and position and shoulder, elbow, and wrist range of motion and peak joint angles) were captured using standard three-dimensional motion capture techniques. Kinematic measures were determined for block movements during the middle of each BBT trial. A mixed-effects model was used to identify group differences (α = 0.05). BBT score was different (p = 0.005) between the 7- (44.88 ± 6.03) and the 11-year-old age group (56.95 ± 8.37) along with peak shoulder flexion (p = 0.024) and abduction (p = 0.022). Peak elbow flexion was different (p = 0.049) between the 9- and 11-year-old age groups. No differences were seen between the 7- and 9-year-old age groups. Pearson's Correlation Coefficients were determined between cycle time and each significant kinematic measure, where the cycle time is specific to each block movement (BBT score) and is correlated to the BBT score. This resulted in weak correlations for all the comparisons. Therefore, using BBT score alone is not representative of UE kinematics and both should be collected during this task to provide insight into movement mechanics in a pediatric population.

Impact of Race, gait speed and arch height on plantar loading.

Diabetes is a leading cause for death in the United States, with African Americans (AA) being twice as likely to die from diabetes than White Americans (WA). AA are twice as likely to experience diabetes-related foot amputation due to foot ulcers, which are most often caused by high plantar pressure. While it is known that arch height, sex, family history of diabetes, Body Mass Index (BMI), age, and gait speed can impact plantar loading, there is a need to test the hypothesis that race in combination with the previously mentioned variables are significant predictors of plantar loading. To answer this question, plantar loading data was collected from 107 participants using an EMED pressure-measurement system (Novel Electronics, Inc, St Paul, MN, USA). Each participant walked barefoot at a self-selected walking pace ten times. Contact area, maximum force, and were force-time integral collected for each step on the pressure plate. A multiple linear regression was used to test if race, age, Arch Height Index (AHI), gait speed, sex assigned at birth, family history of diabetes, and BMI significantly predicted plantar loading. Race, age, AHI, gait speed, sex, and BMI were considered significant predictor variables for plantar loading. Most importantly, race was a significant predictor of maximum force in the hallux (ß = 6.46, p < 0.001), rearfoot (ß = -6.36, p < 0.001), and lateral midfoot (ß = -2.72, p < 0.001), and the force-time integral in the hallux (ß = 2.37, p < 0.001), rearfoot (ß = -2.14, p < 0.001), and lateral midfoot (ß = -0.65, p < 0.001). These findings could help with understanding why AA are more likely to develop diabetic foot ulcers than WA.

Using load sensing insoles to identify knee kinetic asymmetries during landing in patients with an Anterior Cruciate Ligament reconstruction.

BACKGROUND: Knee extension moment asymmetry is a known second anterior cruciate ligament injury risk factor in patients who have had an anterior cruciate ligament reconstruction. Traditionally, assessing asymmetries requires motion capture and force platforms which are expensive and occupy a large space. Wireless force sensing insoles could be a feasible surrogate. METHODS: Twenty-nine patients following anterior cruciate ligament reconstruction performed ten bilateral stop jumps while insole forces, ground reaction forces, and lower extremity kinematics were collected. Peak knee extension moment symmetry was computed using the kinematic and kinetic data, and peak impact force symmetry and impulse symmetry were computed using both the insole force data and vertical ground reaction force data. The relationship between outcomes was analyzed using Pearson correlation coefficients. Patients were classified as symmetric or asymmetric for each outcome based on an 85% symmetry cutoff. The resulting classifications were qualitatively compared across outcome measures. FINDINGS: Peak knee extension moment symmetry had a strong association with the force plate symmetry outcomes (r = 0.72-0.96, p < 0.001) and a moderate to strong association with insole symmetry outcomes (r = 0.67-0.77, p < 0.001). There was strong agreement between insole and force plate symmetry outcomes (r = 0.69-0.90, p < 0.001). Four patients were identified as symmetric when using the peak knee extension moment symmetry, five when using force plate data, and eight when using insole data. INTERPRETATION: Force sensing insoles could be used as a surrogate for knee extension moment asymmetry in patients who have had an anterior cruciate ligament reconstruction.

Reflections on Presurgical and Postsurgical Gait Mechanics After 50 Years of Total Ankle Arthroplasty and Perspectives on the Next Decade of Advancement.

Although not the most prevalent form of lower limb pathology, ankle arthritis is one of the most painful and life-limiting forms of arthritis. Developing from overuse and various traumatic injuries, the effect of ankle arthritis on gait mechanics and effective treatment options for ankle arthritis remain an area of extensive inquiry. Although nonsurgical options are common (physical therapy, limited weight-bearing, and steroidal injections), surgical options are popular with patients. Fusion remains a common approach to stabilize the joint and relieve pain. However, starting in the early 1970s, total ankle arthroplasty was proposed as an alternative to fusion.

Adaptive locomotion: Foot strike pattern and limb mechanical stiffness while running over an obstacle.

Previous studies of level running suggest runners adjust foot strike to control leg stiffness. This study aimed to determine how runners adjusted mechanical stiffness and foot strike prior to, during, and after a drop in surface height. Ten healthy subjects (5 male, 5 female; 24.32 ± 5.0 years) were video recorded as they ran on an outdoor path with a single drop in surface height (12.5 cm). Foot strike was recorded, while subject velocity, duty factor (DF), normalized maximum ground reaction force (GRFbw), vertical hip displacement (Δy), leg compression (ΔL), vertical (Kvert) and leg stiffness (Kleg), touchdown (TD) and takeoff angle (TO), and flight (Tf) and contact time (Tc) were calculated. Compared to the step before the drop, Tf, GRFbw, Kvert, Kleg, and TO increased, while Tc, DF, Δy, ΔL, and TD decreased in the step after the drop. Across trials, runners had either consistent or variable foot strike patterns. Runners using a consistent pattern most often shifted from rear to fore-foot strike in the steps before and after the drop, while those with a variable pattern showed less dramatic shifts. All parameters, except TD, were significantly different (p < 0.04) based on foot strike pattern, and comparisons between steps before and after the drop (except TD) were significantly different (p < 0.004). Runners with a variable foot strike pattern experienced smaller shifts within mechanical parameters when traveling over the drop, suggesting these runners may be able to stabilize limb mechanics on interrupted surfaces.

Reduction of risk factors for ACL Re-injuries using an innovative biofeedback approach: A phase I randomized clinical trial.

OBJECTIVES: Determine the safety and initial efficacy of a novel biofeedback intervention to improve landing mechanics in patients following anterior cruciate ligament reconstruction (ACLR). METHODS: Forty patients post-ACLR (age: 16.9 ± 2.0 years) were randomly allocated to a biofeedback intervention or an attention control group. Patients in the biofeedback group completed 12 sessions over six-weeks that included bilateral unweighted squats with visual and tactile biofeedback. Patients in the control group completed a six-week educational program. Lower extremity mechanics were collected during a bilateral stop jump at baseline, six-weeks, and 12-weeks post-intervention. Linear mixed-effects models adjusted for sex and graft type determined the main effects of and interactions between group and time. RESULTS: No group by time interaction existed for peak knee extension moment symmetry. A group by time interaction existed for peak vertical ground reaction force symmetry (p = 0.012), where patients in the biofeedback group had greater improvements in symmetry between baseline and post-intervention that were not maintained through the retention assessments. CONCLUSION: This novel biofeedback program did not reduce risk factors for second ACL injuries. Future work could develop and test multidisciplinary interventions for reducing second ACL injury risk factors. CLINICALTRIALS: GOV IDENTIFIER: (NCT03273673).

The impact of sampling frequency on ground reaction force variables.

New portable and low-cost technologies for assessing limb loading may be useful in non-laboratory environments, but have relatively low sampling frequencies. The lowest recommended sampling frequency for impact kinetics has not been investigated. The purpose of this study was to determine the effect of sampling frequency on metrics of impact kinetics during landing, walking, and running. This was a retrospective analysis of bilateral drop vertical jumps, unilateral drop landings, treadmill running, and flat, inclined, and declined treadmill walking. Landing data were collected at 1920 Hz while walking and running data were collected at 1440 Hz. Impact kinetics were computed at the highest possible sampling frequency, and then data were continuously down-sampled to determine the impact on the following computed metrics: peak impact force, average LR, and impulse. The minimum sampling frequency to compute each outcome with 90%, 95%, and 99.5% accuracy when compared to the original sampling frequency were determined. To achieve 90% of the true value of impact force, a sampling frequency of 180 Hz was needed for running, 62 Hz for bilateral landing, and 48 Hz for remaining tasks. For average LR, a sampling frequency of 1440 Hz was need for running, 63 Hz for inclined walking, 192 Hz for bilateral landing, and 48 Hz for the remaining tasks. For impulse, 48 Hz was required for all tasks. The results of this study provide future researchers with a guide for selecting the sampling frequency required to accurately assess impact kinetics during walking, landing, or running.

Racial differences in running and landing measures associated with injury risk vary by sex.

It is unknown whether running and landing mechanics differ between racial groups despite injury disparities between African Americans (AA) and white Americans (WA). This study aimed to identify potential racial differences in running and landing mechanics and understand whether anthropometric, strength, and health status factors contribute to these differences. Venous blood samples, anthropometry, lower-extremity strength, and health status assessments were collected (n = 84, 18-30y). Three-dimensional motion capture and force plate data were recorded during 7 running and 7 drop vertical jump trials. Racial effects were determined, and regression models evaluated explanatory factors. AA females ran with longer stance times (p = 0.003) than WA females, while AA males ran with smaller loading rates (p = 0.046) and larger peak vertical ground reaction forces (p = 0.036) than WA males. Frontal plane knee range of motion during landing was greater in AA females (p = 0.033) than WA females; larger waist circumference and weaker knee extension strength accounted for this significance. Although outcome measures were associated with physiologic, anthropometric, and activity measures, their explanatory power for race was ambiguous, except for knee range of motion in females. Modifiable factors explaining racial effects during landing in females are potential intervention targets to reduce racial health disparities in running and landing injuries.

Landing biomechanics deficits in anterior cruciate ligament reconstruction patients can be assessed in a non-laboratory setting.

Landing biomechanics provide important information pertaining to second anterior cruciate ligament (ACL) injury risk in patients following ACL reconstruction (ACLR). While traditional motion analysis technologies are often impractical for use in non-laboratory settings, methods to assess landing biomechanics which are inexpensive, portable, and user-friendly have recently been developed and validated. The purpose of this study was to compare landing kinematics and kinetics between ACLR patients and uninjured controls in a non-laboratory setting. Sixteen ACLR patients (7 male/9 female, 6-12 months post-ACLR) and 16 gender-matched controls completed seven bilateral drop vertical jumps and seven unilateral drop landings on each limb. Plantar force was measured bilaterally using force sensing insoles and frontal and sagittal-plane knee kinematics were measured using two tablets, six reflective markers, and automated point tracking software. Plantar force impulse normalized symmetry index (NSI) and knee frontal plane projection angle (FPPA) range of motion were computed during bilateral landing, and knee flexion range of motion NSI was computed during unilateral landing and compared between groups using independent samples t tests. ACLR patients had larger NSIs (reflecting less symmetry) for plantar force impulse during bilateral landing (p < 0.001) and knee flexion range of motion during unilateral landing (p = 0.004). No between-group differences were observed for knee FPPA range of motion (p = 0.111). This study is an important step towards assessing landing biomechanics in non-research settings with the goal of providing quantitative injury risk metrics in a clinical setting that can be used for return to sport decision making.

Continuous similarity analysis in patient populations.

Decreased movement symmetry is associated with injury risk and accelerated disease progression. Methods to analyze continuous data either cannot be used in pathologic populations with abnormal movement patterns or are not defined in terms easily incorporated into clinical care. The purpose of this study was to develop a method of describing symmetry and movement quality in continuous time-series data that results in scores that can be readily incorporated into clinical care. Two scores were developed: (1) the symmetry score (SS) which evaluates similarities in time-series data between limbs and (2) the closeness-to-healthy score (CTHS) which evaluates the similarity of time-series data to a control population. Kinetic and kinematic data from 56 end-stage unilateral ankle arthritis (A-OA) patients and 56 healthy older adults, along with 16 anterior cruciate ligament reconstruction (ACLR) patients and 16 healthy young adults were used to test the ability for SS and CTHS to differentiate between healthy and patient groups. Unpaired t-tests, Cohen's D effect sizes, and receiver-operating-curve analyses assessed group differences [SPSS, V27, α = 0.05]. Patients had worse SS than controls and A-OA patients had worse CTHS compared to controls. SS had strong predictive capability, while the predictive capability of CTHS varied. Combined with clinically accessible data collection methods, the SS and CTHS could be used to evaluate patients' baseline movement quality, assess changes due to disease progression, and during recovery. Results could be utilized in clinical decision making to assess surgical intervention urgency and efficacy of surgical interventions or rehabilitation protocols to improve side-to-side limb symmetry.

Validity of estimating center of pressure during walking and running with plantar load from a three-sensor wireless insole.

The purpose of this study was to determine if estimated center of pressure (COP) from plantar force data collected using three-sensor loadsol insoles was comparable to the COP from plantar pressure data collected using pedar insoles during walking and running. Ten healthy adults walked and ran at self-selected speeds on a treadmill while wearing both a loadsol and pedar insole in their right shoe. Plantar force recorded from the loadsol was used to estimate COP along mediolateral (COPx) and anteroposterior (COPy) axes. The estimated COPx and COPy were compared with the COPx and COPy from pedar using limits of agreement and Spearman's rank correlation. There were significant relationships and agreement within 5 mm in COPx and 20 mm in COPy between loadsol and pedar at 20-40% of stance during walking and running. However, loadsol demonstrated biases of 7 mm in COPx and 10 mm in COPy compared to pedar near initial contact and toe-off.

Effect of osteopathic manipulation on gait asymmetry.

CONTEXT: Movement and loading asymmetry are associated with an increased risk of musculoskeletal injury, disease progression, and suboptimal recovery. Osteopathic structural screening can be utilized to determine areas of somatic dysfunction that could contribute to movement and loading asymmetry. Osteopathic manipulation treatments (OMTs) targeting identified somatic dysfunctions can correct structural asymmetries and malalignment, restoring the ability for proper compensation of stresses throughout the body. Little is currently known about the ability for OMTs to reduce gait asymmetries, thereby reducing the risk of injury, accelerated disease progression, and suboptimal recovery. OBJECTIVES: To demonstrate whether osteopathic screening and treatment could alter movement and loading asymmetry during treadmill walking. METHODS: Forty-two healthy adults (20 males, 22 females) between the ages of 18 and 35 were recruited for this prospective intervention. Standardized osteopathic screening exams were completed by a single physician for each participant, and osteopathic manipulation was performed targeting somatic dysfunctions identified in the screening exam. Three-dimensional (3-D) biomechanical assessments, including the collection of motion capture and force plate data, were performed prior to and following osteopathic manipulation to quantify gait mechanics. Motion capture and loading data were processed utilizing Qualisys Track Manager and Visual 3D software, respectively. Asymmetry in the following temporal, kinetic, and kinematic measures was quantified utilizing a limb symmetry index (LSI): peak vertical ground reaction force, the impulse of the vertical ground reaction force, peak knee flexion angle, step length, stride length, and stance time. A 2-way repeated-measures analysis of variance model was utilized to evaluate the effects of time (pre/post manipulation) and sex (male/female) on each measure of gait asymmetry. RESULTS: Gait asymmetry in the peak vertical ground reaction force (-0.6%, p=0.025) and the impulse of the vertical ground reaction force (-0.3%, p=0.026) was reduced in males following osteopathic manipulation. There was no difference in gait asymmetry between time points in females. Osteopathic manipulation did not impact asymmetry in peak knee flexion angle, step length, stride length, or stance time. Among the participants, 59.5% (25) followed the common compensatory pattern, whereas 40.5% (17) followed the uncommon compensatory pattern. One third (33.3%, 14) of the participants showed decompensation at the occipitoatlantal (OA) junction, whereas 26.2% (11), one third (33.3%, 14), and 26.2% (11) showed decompensation at the cervicothoracic (CT), thoracolumbar (TL), and lumbosacral (LS) junctions, respectively. Somatic dysfunction at the sacrum, L5, right innominate, and left innominate occurred in 88.1% (37), 69.0% (29), 97.6% (41), and 97.6% (41) of the participants, respectively. CONCLUSIONS: Correcting somatic dysfunction can influence gait asymmetry in males; the sex-specificity of the observed effects of osteopathic manipulation on gait asymmetry is worthy of further investigation. Osteopathic structural examinations and treatment of somatic dysfunctions may improve gait symmetry even in asymptomatic individuals. These findings encourage larger-scale investigations on the use of OMT to optimize gait, prevent injury and the progression of disease, and aid in recovery after surgery.

Including jump height when normalizing single hop impact kinetics can change the directionality of findings.

BACKGROUND: Assessing landing kinetics during hop testing could improve return to sport decisions following anterior cruciate ligament reconstruction (ACL) reconstruction. However, different methods for normalizing kinetic outcomes could influence the interpretation of landing kinetics and therefore the clinical recommendations. METHODS: Twenty-one females who had returned to sport following primary unilateral ACL reconstructed completed two single hops for maximum distance on each limb. Hop distance, hop height, peak impact force, and impulse were computed for each hop, and peak impact force and impulse magnitudes were assessed when 1) non-normalized 2) normalized by bodyweight, and 3) normalized by peak potential energy during the hop. FINDINGS: Along with hop distance and height, peak impact force and impulse were found to be lower on the surgical limb relative to the non-surgical limb for both non-normalized data and when normalized to bodyweight only (p < 0.001, d > 0.95). However, peak impact force and impulse were found to be higher on the surgical limb relative to the non-surgical limb when normalizing outcomes to peak potential energy (p < 0.001, d > 1.03). INTERPRETATION: Different normalization methods result in different interpretations of single hop kinetics. ACL reconstruction patients have shorter hop distances, lower hop heights, lower force magnitudes, and worse energy absorption when hopping on their surgical limb, relative to their non-surgical limb. We believe that normalizing landing kinetics using bodyweight and using peak potential energy provide different information, and as such, we suggest that future research use both methods based on the research question.

Bilateral Squatting Mechanics Are Associated With Landing Mechanics in Anterior Cruciate Ligament Reconstruction Patients.

BACKGROUND: Proper lower extremity biomechanics during bilateral landing is important for reducing injury risk in athletes returning to sports after anterior cruciate ligament reconstruction (ACLR). Although landing is a quick ballistic movement that is difficult to modify, squatting is a slower cyclic movement that is ideal for motor learning. HYPOTHESIS: There is a relationship between lower extremity biomechanics during bilateral landing and bilateral squatting in patients with an ACLR. STUDY DESIGN: Descriptive laboratory study. METHODS: A total of 41 patients after a unilateral ACLR (24 men, 17 women; 5.9 ± 1.4 months after ACLR) completed 15 unweighted bilateral squats and 10 bilateral stop-jumps. Three-dimensional lower extremity kinematics and kinetics were collected, and peak knee abduction angle, knee abduction/adduction range of motion, peak vertical ground-reaction force limb symmetry index (LSI), vertical ground-reaction force impulse LSI, and peak knee extension moment LSI were computed during the descending phase of the squatting and landing tasks. Wilcoxon signed-rank tests were used to compare each outcome between limbs, and Spearman correlations were used to compare outcomes between the squatting and landing tasks. RESULTS: The peak vertical ground reaction force, the vertical ground reaction force impulse, and the peak knee extension moment were reduced in the surgical (Sx) limb relative to the nonsurgical (NSx) limb during both the squatting and landing tasks (P < .001). The relationship between squatting and landing tasks was strong for the peak knee abduction angle (R = 0.697-0.737; P < .001); moderate for the frontal plane knee range of motion (NSx: R = 0.366, P = .019; Sx: R = 0.418, P = 0.007), the peak knee extension moment LSI (R = 0.573; P < .001), the vertical ground reaction force impulse LSI (R = 0.382; P < .014); and weak for the peak vertical ground reaction force LSI (R = 0.323; P = .039). CONCLUSION: Patients who have undergone an ACLR continue to offload their surgical limb during both squatting and landing. Additionally, there is a relationship between movement deficits during squatting and movement deficits during landing in patients with an ACLR preparing to return to sports. CLINICAL RELEVANCE: As movement deficits during squatting and landing were related before return to sports, this study suggests that interventional approaches to improve squatting biomechanics may translate to improved landing biomechanics in patients with an ACLR.

The impact of standardized footwear on load and load symmetry.

BACKGROUND: The inability to standardize footwear is a potential issue when measuring landing kinetics in non-laboratory settings. This study determined the impact of not standardizing footwear on load and load symmetry during landing. A secondary purpose of this study was to introduce the Load Analysis Program, an open-source MATLAB® user-interface for computing kinetic and kinetic symmetry from data collected using loadsol® sensors. METHODS: Forty uninjured participants completed bilateral and unilateral landing tasks in their own preferred athletic footwear and in laboratory-standardized footwear. Peak impact force, impulse, and a limb symmetry index of both kinetic outcomes were computed using loadsol® sensors (200 Hz) for both footwear conditions, and compared between footwear conditions using intraclass correlation coefficients and Bland-Altman plots. FINDINGS: The agreement between the preferred and standardized conditions was good to excellent for peak impact force, peak impact force limb symmetry index, and impulse limb symmetry index during the bilateral task (intraclass correlation coefficient = 0.870-0.951). The agreement was moderate to poor for unilateral limb symmetry index measures (intraclass correlation coefficient = 0.399-0.516). During the preferred footwear condition, impulse was greater for the left limb during bilateral landing, and peak impact force during unilateral landing on the right limb was decreased, when compared to the standardized footwear condition (p < 0.05). INTERPRETATION: These results suggest that while not standardizing footwear can alter the results of certain load metrics, laboratory-relevant landing mechanics information can be obtained with participants wearing their own footwear.

Sex-Specific Difference in Dynamic Balance Following Total Hip Replacement.

BACKGROUND AND OBJECTIVES: Total hip arthroplasty (THA) is a common surgical procedure in older adults (65 years or older). THA has high patient satisfaction, but little is known about balance and mobility limitations after surgery and if outcomes are sex-specific. This study was aimed to evaluate post-THA asymmetry during unilateral standing and a dynamic balance and reach test and test the hypotheses that balance performance would be decreased on the surgical limb and that balance deficits would be greater in women than in men. RESEARCH DESIGN AND METHODS: Primary, unilateral THA (70 male, 57 female) patients completed a bilateral 10-s single-leg stance test. Sixty male but only 34 female participants could maintain unilateral balance for 10 s or greater. The cohort who successfully completed the 10-s single-limb stance test then completed a Lower Quarter Y-Balance Test in which the maximum anterior (ANT), posteromedial (PM), and posterolateral reach distances were obtained bilaterally and used to calculate the asymmetry score. All variables were compared using a mixed-model repeated-measures analysis of variance (sex by limb), while independent samples t tests were used to assess sex-specific asymmetry. RESULTS: Women failed single-leg stance at a higher rate than men (85.7% vs 59.6%; p = .001). Reach distance was different between limbs for all reach directions (p < .004) with greater reach distance on the nonoperative limb for all patients. Men had a greater reach distance in the ANT (p = .004) and PM (p = .006) directions. DISCUSSION AND IMPLICATIONS: These results indicate that post-THA, the operative limb and female patients have greater balance limitations. These results are novel and reveal sex-specific patterns that emphasize the need for sex-specific postoperative rehabilitation programs to improve long-term outcomes, especially in older adults with muscle weakness and balance deficits.

Reduction of Risk Factors for ACL Re-injuries using an Innovative Biofeedback Approach: Rationale and Design.

Nearly 1 in 60 adolescent athletes will suffer anterior cruciate ligament (ACL) injuries with 90% of these athletes electing to undergo an ACL reconstruction (ACLR) at an estimated annual cost of $3 billion. While ACLR and subsequent rehabilitation allow these athletes to return to sports, they have a 15-fold increased risk of second ACL injuries. The modification of post-operative rehabilitation to improve movement and loading symmetry using visual and tactile biofeedback could decrease the risk factors for sustaining a second ACL injury. Participants included 40 adolescent ACLR patients who were intending to return to full sport participation. This preliminary randomized controlled trial (RCT) examined the changes in knee extension moment symmetry, a known risk factor for second ACL injuries, during landing from a stop-jump task between the following time-points: pre-intervention, immediate post-intervention, and subsequent follow-up 6-weeks post-intervention. Participants met twice per week for six-weeks (12-session). The intervention included bilateral squat biofeedback (visual and tactile); the attention control group attended weekly educational sessions. This RCT enrolled and randomize 40 participants over a two-and-a-half-year period. All participants were greater than 4.5 months post-op from a primary, unilateral ACLR and were released to participate by their treating physician. The findings from this pilot biofeedback RCT will provide critical effect size estimates for use in subsequent larger clinical trials.