Changes In Gait Speed Research Articles

Obstacle crossing following stroke improves over one month when the unaffected limb leads, but not when the affected limb leads

While it is well established that obstacle crossing is impaired following stroke, it is not known whether obstacle crossing improves as gait improves following stroke. The purpose of this study was to determine whether obstacle crossing changed over a one month time period in people with a recent stroke. Twenty participants receiving rehabilitation following a recent stroke were tested on two occasions one month apart. Participants received usual care rehabilitation, including physiotherapy, between the tests. The main outcome measure was obstacle crossing speed as participants stepped over a 4-cm high obstacle. Secondary measures were spatiotemporal variables. Data were collected via a three dimensional motion analysis system. When leading with the affected limb no changes in obstacle crossing speed or spatiotemporal variables were observed over the one month period. When leading with the unaffected limb, crossing speed significantly increased (p=.002), and affected trail limb swing time (p=.03) and crossing step double support time reduced (p=.016). While not significant, the lead and trail limb pre-obstacle distance increased (p=.08), and lead swing time (p=.052) reduced. Change in obstacle crossing speed did not correlate with change in level gait speed. Obstacle crossing does not necessarily improve over a one month time period in people receiving rehabilitation following stroke. These findings suggest that there may be a need for more targeted training of obstacle crossing, particularly when leading with the affected limb.

Test-retest reliability and sensitivity of the 20-meter walk test among patients with knee osteoarthritis

BackgroundThe 20-meter walk test is a physical function measure commonly used in clinical research studies and rehabilitation clinics to measure gait speed and monitor changes in patients’ physical function over time. Unfortunately, the reliability and sensitivity of this walk test are not well defined and, therefore, limit our ability to evaluate real changes in gait speed not attributable to normal variability. The aim of this study was to assess the test-restest reliability and sensitivity of the 20-meter walk test, at a self-selected pace, among patients with mild to moderate knee osteoarthritis (OA) and to suggest a standardized protocol for future test administration.MethodsThis was a measurement reliability study. Fifteen consecutive people enrolled in a randomized-controlled trial of intra-articular corticosteroid injections for knee OA participated in this study. All participants completed 4 trials on 2 separate days, 7 to 21 days apart (8 trials total). Each day was divided into 2 sessions, which each involved 2 walking trials. We compared walk times between trials with Wilcoxon signed-rank tests. Similar analyses compared average walk times between sessions. To confirm these analyses, we also calculated Spearman correlation coefficients to assess the relationship between sessions. Finally, smallest detectable differences (SDD) were calculated to estimate the sensitivity of the 20-meter walk test.ResultsWilcoxon signed-rank tests between trials within the same session demonstrated that trials in session 1 were significantly different and in the subsequent 3 sessions, the median differences between trials were not significantly different. Therefore, the first session of each day was considered a practice session, and the SDD between the second session of each day were calculated. SDD was −1.59 seconds (walking slower) and 0.15 seconds (walking faster).ConclusionsPractice trials and a standardized protocol should be used in administration of the 20-meter walk test. Changes in walk time between −1.59 seconds (walking slower) and 0.15 seconds (walking faster) should be considered within the range of normal variability of 20-meter walking speed. The primary limitation of our study was a small sample size, which may influence the generalizability of our findings.

Trabecular bone microstructure scales allometrically in the primate humerus and femur

Most analyses of trabecular microarchitecture in mammals have focused on the functional significance of interspecific variation, but they have not effectively considered the influence of body size or phylogeny on bone architecture. The goals of this study were to determine the relationship between trabecular bone and body size in the humeral and femoral heads of extant primates, and to assess the influence of phylogeny on bone microstructure. Using a sample of 235 individuals from 34 primate species, ranging in body size from 0.06 to 130 kg, the relationships between trabecular bone structure and body size were assessed by using conventional and phylogenetic regression analyses. Bone volume fraction, trabecular thickness and trabecular spacing increase with body size, whereas bone surface-area-to-volume ratio decreases. Shape variables such as trabecular number, connectivity density and degree of anisotropy scale inversely with size. Most of these variables scale with significant negative allometry, except bone surface-area-to-volume ratio, which scales with slight positive allometry. Phylogenetic regressions indicate a relatively weak phylogenetic signal in some trabecular bone variables. These data demonstrate that, relative to body size, large primates have thinner and more tightly packed trabeculae than small primates. The relatively thin trabeculae in large primates and other mammals, coupled with constraints on trabecular thickness related to osteocyte function, suggest that increased skeletal loads in the postcranial joints of large mammals are probably mitigated not only through alterations in trabecular microarchitecture, but also through other mechanisms such as changes in cortical bone distribution, limb posture and gait speed.

Effect of gait speed changes on foot loading characteristics in children

Gait speed has been shown to influence foot loading patterns in adults but the mechanism has not been investigated in children. The present study investigated the effects of changes in gait speed on foot loading characteristics in 20 typically developing children who participated in plantar pressure measurements at normal, slow and fast walking speeds. In spite of shorter contact times in the fast walking speed condition, significantly increased foot loading was seen in the hindfoot, medial and central forefoot and toes while it slightly decreased in the lateral midfoot and forefoot. The results generally confirm the findings in adults that gait speed does not uniformly affect foot loading characteristics and that these effects should be kept in mind when comparing different subject groups or children at repeated measurement occasions.

Impact of leg length and body mass on the stride length and gait speed of infants with normal motor development: A longitudinal study

Gait acquisition is supported by changes in the neuromusculoskeletal system of the child. Changes in the dimensions of the body structures resulting from the growth of the child partly explain gait improvement in the first year of life. To evaluate whether changes in body mass and leg length modulate the effect of independent gait practice (experience) on gait speed and stride length. Thirty-two infants with normal development were monitored monthly from the acquisition of independent gait until six months post-acquisition. Longitudinal evaluations included measurements of the body mass and leg length of each child. Temporospatial variables of gait (speed and stride length) were documented using the Qualisys Pro-reflex(r) system. The data were analyzed using multilevel regression models, with a significance level of α=0.05. An effect of the practice time on speed (p<0.0001) and stride length (p<0.0001) was observed. The change in leg length had a marginal effect on the rate of gait speed change: children whose leg growth was faster showed a higher rate of speed change (p=0.07). No other effects of anthropometric parameters were observed. The results suggest that the practice time promotes the improvement of the gait pattern of infants in the first year of life. However, the effects of the leg length and body weight of infants on the benefit of practice time remain undefined.

Reliability and sensitivity of the 20-meter walk test among patients with knee osteoarthritis

Purpose: The 20-meter walk test is a physical function measure commonly used in clinical research studies and rehabilitation clinics to measure gait speed and monitor changes in patients’ physical function over time. Unfortunately, the reliability and sensitivity of this walk test are not well defined and therefore limit our ability to evaluate changes in gait speed. The aim of this study was to assess the reliability and sensitivity of the 20-meter walk test, at a self-selected pace, among patients with knee osteoarthritis (OA). Methods: This was a measurement reliability study that included fifteen consecutive participants enrolled in a randomized-controlled trial of intra-articular corticosteroid injections for knee OA. The study sample included consecutive participants attending screening (Day 1) and baseline (Day 2) visits between July 2011 and December 2011. All participants met the American College of Rheumatology criteria for OA; had radiographic knee OA, as defined by Kellgren-Lawrence grade 2 or 3; and knee synovitis, defined by a synovial pouch depth greater than 2.0 mm measured by ultrasound. All participants were also required to have knee pain symptoms, defined as a WOMAC Osteoarthritis Index (version 3.1, 5-point Likert) pain subscore > 2 at the beginning of their first visit (Day 1). All participants completed 4 trials on 2 separate days, 7 to 21 days apart (8 trials total). Each day was divided into 2 sessions, which each involved 2 walking trials. Day 1 contained sessions 1 (trial 1 and 2) and session 2 (trial 3 and 4) and Day 2 contained session 3 (trial 5 and 6) and session 4 (trial 7 and 8). All trials were administered by the same investigator following a standardized script and protocol. We compared walk times between trials with Wilcoxon signed-rank tests. We also calculated Spearman correlation coefficients to assess the relationship between sessions. Finally, smallest detectable differences (SDD) were calculated to estimate the sensitivity of the 20-meter walk test. Results: Participants were 53% female, 67% (n 1⁄4 10) Caucasian, on average 61.0 7.8 years of age and had a mean body mass index of 28.9 5.4 kg/m2. Twelve participants (80%) had Kellegren-Lawrence Grade 1⁄4 3. WOMAC pain scores were 5.3 1.3 on Day 1 and 4.9 2.0 on Day 2. The figure depicts walk times across trials. We found that walking times in the first session were slower than the second session (median difference 1⁄4 0.53 seconds, -0.04 m/s; Table). We also found that the correlation between session 1 and sessions 3 and 4 were lower than the correlations between session 2 and sessions 3 and 4 (Table). Therefore, we considered the first session of each day a practice session and calculated the SDD between the second session of each day (session 2 and 4). SDD were -2.59 seconds (walking slower) and 1.65 seconds (walking faster). There was a potential systematic bias of participants walking slower during the second session on Day 2 compared to the second session of Day 1 (10 [67%] participants walked slower in session 4 compared to session 2; based on differences below zero). Conclusions:We found that the average of the first two 20-meter walk times did not agree with subsequent average walk times among participants with knee OA. Therefore, practice trials may be advised prior to a measuring a participants walk time. Despite concerns about thewalk times of session 1, the following sessions were reliable and had good agreement. Finally, changes in walk time between -2.59 seconds (walking slower) and 1.65 seconds (walking faster) should be considered within the range of normal variability of 20-meter walking speed.

Reliability and Responsiveness of Gait Speed, Five Times Sit to Stand, and Hand Grip Strength for Patients in Cardiac Rehabilitation

Following a cardiac event patients are at risk for deficits in mobility and function. However, measures of physical performance are not commonly used and have not been extensively studied in patients enrolled in cardiac rehabilitation. The purpose of this study was to determine the reliability and the minimal detectable change (MDC) of gait speed, 5 times sit to stand (5 STS) and hand grip strength for individuals enrolled in cardiac rehabilitation. Forty-nine individuals enrolled in phase II or III cardiac rehabilitation participated in the study. Gait speed, 5 STS, and hand grip strength were measured over two sessions held on the same day. Intraclass correlation coefficient was used to determine reliability and MDC95 was calculated to measure responsiveness. All 3 measures showed high reliability (ICC for gait speed = 0.96, 5 STS = 0.87, right hand grip strength = 0.97, left hand grip strength = 0.97). The MDC95 for gait speed was 0.16 meters/second, 3.12 seconds for 5 STS, 5.2 kilograms for right and 5.1 kilograms for left hand grip strength. Gait speed, 5 STS, and hand grip strength are reliable and responsive measures for patients in cardiac rehabilitation. Findings support their use in clinical practice and future cardiac rehabilitation studies.

Gait Speed Improves During Physical Therapy in General Acute Care, Skilled Nursing, and Inpatient Rehabilitation - a Pilot Study

Objective: To describe gait speed and gait speed changes that occurred in patients who received physical therapy in general health care settings of acute care, skilled nursing, and inpatient rehabilitation settings. Design: Pre-post observational cross-sectional study of changes in gait speed. Setting: Acute care, skilled nursing, and inpatient rehabilitation facilities of a regional medical center in the United States. Participants: Individuals (n=110) admitted with physical therapy referrals with full weight bearing status who could ambulate 20 feet and consented to participate. Main Outcome Measure: Change in gait speed from initial visit to therapy discharge. Results: Two-way mixed ANOVA determined that mean gait speed improved significantly between initial and discharge time points (p<.001). An interaction effect between gait speed and health care settings (p<.001), indicated varying levels of speed achieved across different health care settings. Post hoc tests using Bonferroni adjustments showed acute care discharge gait speed was not significantly different from skilled nursing (p=0.352), but inpatient rehabilitation was significantly different from both acute care (p<.001) and skilled nursing (p=0.02) units. Paired t-tests of the individual health care settings revealed that gait speed was significantly improved in acute care [initial vs. discharge; 0.31(0.22) vs. 0.38 (0.21) m/s], skilled nursing [0.36 (0.19) vs. 0.61(0.39) m/s], and inpatient rehabilitation [0.60( 0.70) vs. 0.98 (0.72) m/s]. Minimal detectable change for gait speed was 0.16m/s in acute care, 0.14m/s in skilled nursing, and 0.51m/s inpatient rehabilitation. Conclusions: Self-selected gait speed is an informative measure. Gait speed improved from physical therapy initial evaluation to discharge in 3 different health care settings. In acute care, gait speeds improved over a short course of therapy, but these speeds would still be considered to be slow relative to community requirements. In skilled nursing and inpatient rehabilitation, patients achieve gait speeds required for limited community level ambulation.

Assessing the Reliability and Validity of a Shorter Walk Test Compared With the 10-Meter Walk Test for Measurements of Gait Speed in Healthy, Older Adults

Walking speed is associated with several health-related outcomes. Research examining how differences in test walking distance affect walking speed reliability and validity is limited. The primary purpose of this study was to examine the reliability and concurrent validity of gait speed measurements obtained from a 4-Meter Walk Test compared with the commonly used 10-Meter Walk Test. A second objective was to similarly examine 2 different timing methods: stopwatch and automatic timers. Forty-three healthy, older adults (mean age = 84.3 ± 6.9 years) performed 3 consecutive walking trials on the 4- and 10-Meter Walk Tests at their self-selected walking speed. Gait speed measurements for both tests were shown to have excellent test-retest reliability (ICC values of 0.96-0.98), with similar results for stopwatch and automatic timer assessments (ICC values of 0.99-1.00). Standard error of the measurement (SEM) values were small (0.004-0.008 m/s) across measurement methods. While the ICC value for gait speed measurements between the 2 walk tests was 0.93, the Bland-Altman analysis revealed a discrepancy of ±0.15 to ±0.17 m/s between measurement methods. Both 4- and 10-m gait speed assessments had excellent test-retest reliability with similar SEM and minimal detectable change values. There was little difference in SEM values between the 2 timing methods. While the mean difference in gait speed between the 4- and 10-Meter Walk Tests was small, the range of the measurement differences was large enough to potentially mask meaningful changes in gait speed over time if both methods were used interchangeably. While the reliability of both walking tests is excellent, the 4-Meter Walk Test does not exhibit a high enough degree of concurrent validity with the 10-Meter Walk Test to be used interchangeably for gait speed assessments in healthy, older adults. We therefore recommend using the 10-Meter Walk Test to obtain the most valid clinical assessment of walking speed when using it as a 1-time indicator of health status.

The Effects of Different Gait Speeds and Lower Arm Weight on the Activities of the Latissimus Dorsi, Gluteus Medius, and Gluteus Maximus Muscles

[Purpose] This study researched the effects of different gait speeds and lower arm weight on the activities of the latissimus dorsi, gluteus medius, and gluteus maximus muscles. [Subjects] Fourteen healthy adult men participated in this study. [Methods] All the participants carried out walking on a treadmill at speeds of 3.5 km/h and 5.5 km/h for half a minute. During treadmill gait, electromyographic activity muscle was measured of the latissimus dorsi, gluteus medius and gluteus maximus. [Result] There were significant differences in the muscle activities due to changes in gait speed and lower arm load in the latissimus dorsi and gluteus maximus, but there were no significant differences in the muscle activities of the gluteus medius. [Conclusion] According to our results, arm swing is related to increasing gait speed, and lower arm load is influences the muscle activity of the lower extremities through the posterior oblique sling system.

Walking Activity of Older Patients in Rehabilitation: A Prospective Study.

To quantify, using accelerometry, walking activity of older rehabilitation inpatients and to examine the relationship between walking activity and functional outcomes. Prospective cohort study. Inpatient geriatric rehabilitation unit. Of 74 consecutive eligible patients, aged 60 years or older and able to walk independently or with assistance, 60 participants (32 males, 28 females) with a mean (SD) length of stay of 37 (26) days completed the study. Intervention Measures: An accelerometer was worn in daytime hours from study recruitment until discharge to monitor daily walking minutes. On study entry, patients spent a median (IQR) of 33 (20 to 48) minutes (7%) of the daily monitored eight hour period walking. By discharge, this had increased to 43 (30 to 56) minutes (9%) (p< 0.001). Average daily walking activity over the week prior to discharge correlated with change in gait speed from admission to discharge (p<0.05). Walking activity prior to discharge was significantly different (p<0.05) between the slowest gait speed group (≤0.4 m/s) and the fastest gait speed group (≥0.8 m/s). Those with discharge gait speeds ≥0.8 m/s (associated with ability to be ambulant in the community) had median (IQR) daily walking times at discharge of 51 (33 to 78) minutes. Activity monitoring has the potential to assist clinicians and patients set goals around activity levels to achieve better outcomes.

Minimal Clinically Important Difference for Comfortable Speed as a Measure of Gait Performance in Patients Undergoing Inpatient Rehabilitation after Stroke

[Purpose] The purpose of this retrospective study was to determine the minimal clinically important difference for comfortable gait speed for patients with stroke. [Subjects] Data were analyzed from 35 patients undergoing inpatient rehabilitation. [Methods] Two characteristics of gait were measured, assistance required and comfortable gait speed. Patients were grouped as either experiencing or not experiencing a decrease of 2 or more levels of assistance required over the course of rehabilitation. Receiver operating characteristic curve analysis was used to identify the change in gait speed that best differentiated between patients who did and did not experience the requisite decrease in assistance required for gait. [Results] Twenty-one patients decreased 2 or more levels of assistance whereas 14 did not. Walking speed increased significantly more in the group who experienced a decrease in assistance of at least 2 levels. The receiver operating characteristic curve analysis showed a change in walking speed of 0.13 m/s best distinguished between patients who did versus did not experience a reduction in assistance required. [Conclusion] An improvement in gait speed of 0.13 m/s or more is clinically important in patients with stroke.

30-day hospital readmission of older adults using care transitions after hospitalization: a pilot prospective cohort study

PurposePatients leaving the hospital are at increased risk of functional decline and hospital readmission. The Employee and Community Health service at Mayo Clinic in Rochester developed a care transition program (CTP) to provide home-based care services for medically complex patients. The study objective was to determine the relationship between CTP use, 30-day hospital readmission, and Emergency Room (ER) visits for adults over 60 years with high Elder Risk Assessment scores.Patients and methodsThis was a pilot prospective cohort study that included 20 patients that used the CTP and 20 patients discharged from the hospital without using the CTP. The medically complex study patients were drawn from the department of Employee and Community Health population between October 14, 2011 and September 27, 2012. The primary outcomes were 30-day hospital readmission or ER visit after discharge from the hospital. The secondary outcomes were within-group changes in grip strength, gait speed, and quality of life (QOL). Patients underwent two study visits, one at baseline and one at 30 days postbaseline. The primary analysis included time-to-event from baseline to rehospitalization or ER visit. Paired t-tests were used for secondary outcomes, with continuous scores.ResultsOf the 40 patients enrolled, 36 completed all study visits. The 30-day hospital readmission rates for usual care patients were 10.5% compared with no readmissions for CTP patients. There were 31.6% ER visits in the UC group and 11.8% in the CTP group (P = 0.37). The secondary analysis showed some improvement in physical QOL scores (pre: 32.7; post: 39.4) for the CTP participants (P < 0.01) and no differences in gait speed or grip strength.ConclusionBased on this pilot study of care transition, we found nonsignificant lower hospital and ER utilization rates and improved physical QOL scores for patients in the CTP group. However, the data leads us to recommend future studies with larger sample sizes (N = 250).

Muscle strength and ankle mobility for the gait parameters in diabetic neuropathies

AimsTo evaluate the spatio-temporal variables of gait and the isometric muscle strength component of the ankle in patients with peripheral diabetic neuropathy. Also, verify the relationship between these variables and gait parameters. MethodsThis study involved 25 diabetic peripheral neuropathy (DPN) participants (62.4±8.36 years) and 27 age-matched healthy control individuals (64.48±6.21 years). The assessment of the spatio-temporal parameters of gait was performed using an electronic baropodometry treadmill. Prior to the collection data, each participant was instructed to walk on the treadmill in her/his habitual self-selected speed. ResultsDiabetic neuropathy group showed impairment of gait, with a smaller stride and length speed of the cycle, and increased duration of support time. Restricted dorsiflexion mobility and increased plantarflexion mobility were found, with a decrease in muscle strength of the dorsiflexors and plantiflexors. There was a significant relationship between plantiflexor muscle strength and the length and speed of the gait cycle. Also the muscle strengths of the plantiflexors and dorsiflexors, and the range of motion of dorsiflexion were predictors of gait performance. ConclusionsThe ankle, muscle strength and ankle mobility variables could explain changes in gait speed and range of motion in patients with DPN, allowing for the application of preventive strategies.

Assessing the Temporal Relationship Between Cognition and Gait: Slow Gait Predicts Cognitive Decline in the Mayo Clinic Study of Aging

The association between gait speed and cognition has been reported; however, there is limited knowledge about the temporal associations between gait slowing and cognitive decline among cognitively normal individuals. The Mayo Clinic Study of Aging is a population-based study of Olmsted County, Minnesota, United States, residents aged 70-89 years. This analysis included 1,478 cognitively normal participants who were evaluated every 15 months with a nurse visit, neurologic evaluation, and neuropsychological testing. The neuropsychological battery used nine tests to compute domain-specific (memory, language, executive function, and visuospatial skills) and global cognitive z-scores. Timed gait speed (m/s) was assessed over 25 feet (7.6 meters) at a usual pace. Using mixed models, we examined baseline gait speed (continuous and in quartiles) as a predictor of cognitive decline and baseline cognition as a predictor of gait speed changes controlling for demographics and medical conditions. Cross-sectionally, faster gait speed was associated with better performance in memory, executive function, and global cognition. Both cognitive scores and gait speed declined over time. A faster gait speed at baseline was associated with less cognitive decline across all domain-specific and global scores. These results were slightly attenuated after excluding persons with incident mild cognitive impairment or dementia. By contrast, baseline cognition was not associated with changes in gait speed. Our study suggests that slow gait precedes cognitive decline. Gait speed may be useful as a reliable, easily attainable, and noninvasive risk factor for cognitive decline.

White matter hyperintensity volume and impaired mobility among older adults.

Gait speed is associated with multiple adverse outcomes of aging. White matter hyperintensities (WMH) on magnetic resonance imaging (MRI) have been associated with gait speed, though few studies have examined changes in gait speed over time in population-based studies comprising participants from diverse cultural backgrounds. The purpose of this study was to examine the association between a decline in gait speed and total and regional WMH volumes in a community-based study of aging. Participants (n=701) underwent gait-speed measurement via a 4-m walk test at the time of initial enrollment and MRI at a second time interval (mean 4.7 [SD=0.5] years apart). Logistic regression was used to examine the association between large WMH volume and regional WMH volume with gait speed <0.5m/s (abnormal speed), and a transition to abnormal gait speed. Analyses were adjusted for demographic and clinical factors. Large WMH volume was associated with abnormal gait speed and a transition to abnormal gait speed between the two visits, but not after adjustment for modifiable vascular disease risk factors. Increased frontal lobe WMH volume was associated with abnormal gait speed and transition to abnormal gait speed, but not in adjusted models. WMH are associated with slowing of gait over time. Prevention of WMH presents a potential strategy for the prevention of gait speed decline.

Application of Adapted Tango as Therapeutic Intervention for Patients With Chronic Stroke

Dance has demonstrated beneficial effects on mobility in older individuals with movement disorders; yet, effects of partnered dance remain unexamined in individuals with chronic stroke. The purpose of this study was to describe the effects of adapted tango classes on balance, mobility, gait, endurance, dual-task ability, quality of life (QOL), and enjoyment in an older individual with chronic stroke and visual impairment. D.L. was a 73-year-old African American man, 13 years poststroke with spastic hemiplegia, visual impairment, and multiple comorbidities. D.L. attended 20 1?-hour tango classes adapted for older individuals with sensory and motor impairments over 11 weeks. Measures of balance, mobility, gait, endurance, dual-task ability, and QOL were evaluated before and after the intervention and at 1-month follow-up. D.L. improved on the Berg Balance Scale, 30-s chair stand, Timed Up and Go (single, manual, and cognitive conditions), 6-minute walk test, and backward gait speed. Not all measures improved: balance confidence decreased, and there was no change in forward and fast gait speed or QOL, as measured by the short form-12 and the visual function questionnaire-25. Some gains were maintained at one-month follow-up. D.L. reported enjoying the classes, noted improvement in physical well-being, and wanted to continue the program. Thirty hours of adapted tango lessons improved balance, mobility, endurance, and dual-task ability in a participant with chronic stroke. The participant enjoyed the classes, was adherent, and wished to continue. This is the first reported use of adapted tango dance as rehabilitation for an individual with chronic stroke and low vision.

The 2012 Frank Stinchfield Award: Decreasing Patient Activity With Aging: Implications for Crosslinked Polyethylene Wear

Patient activity influences polyethylene wear. However, it is unclear how individual activity changes with patient aging after THA. We quantified changes in individual gait cycles and gait speed, assessed age-related differences in these parameters, and determined their relationship to polyethylene wear. A microprocessor was worn on the ankle to quantify the activity of 14 healthy patients with a well-functioning THA at two time periods: early (within 3.5 years of implantation) and late (10-13 postoperative years). Wear was measured on serial radiographs using edge detection-based software. Mean activity decreased by 16% from the early to the late period: 2.04 million gait cycles/year to 1.71 million gait cycles/year. Mean gait speed decreased by 9%: 15.4 cycles/minute to 14.0 cycles/minute. The activity of the 10 patients who were younger than 65 years at surgery decreased by 14% (2.34million gait cycles/year to 2.02 million gait cycles/year), while the four patients 65 years or older at surgery decreased by 28% (1.29 million gait cycles/year to 0.94 million gait cycles/year). Gait speed was 26% slower for patients 65 years or older than for patients younger than 65 years. The mean linear penetration rate decreased by 42% from the first 5 years (early wear rate) to the next 8 years (late wear rate, 5-13 years): 0.043 mm/year to 0.025 mm/year. The greatest patient activity and wear occurred during the first 5 years. Walking speed and gait cycles both decreased with aging, resulting in deceasing wear over time.

Institutional Outcomes in Patients Evaluated for Possible Normal Pressure Hydrocephalus: Which Factors Are Predictive of Positive Response to Ventriculoperitoneal Shunt Placement? (P02.245)

Objective: The goal of this study was to examine patient outcomes after their initial evaluation in the Movement Disorders (MD) Clinic at our institution for possible normal pressure hydrocephalus (NPH). We attempted to identify predictive factors that lead to the clinical diagnosis of NPH and ultimately to pursuit of ventriculoperitoneal shunt (VPS) placement, as well as those that lead to positive post-surgical outcomes. Background First, we wanted to review patient outcomes after VPS placement for NPH at our institution. Second, given current limitations in successfully identifying optimal surgical candidates among patients with possible NPH, we wanted to review the clinical and radiological data utilized for decision-making with each patient to see if certain factors were more predictive of positive outcome. Design/Methods: This was a retrospective chart review of patients evaluated in MD Clinic for gait disturbance between January 2007 and October 2010. Outcomes were based on the patients9 postoperative assessments in Neurosurgery and/or MD Clinic and Clinical Global Impression (CGI) scale scores. Results: Fourteen of 25 patients initally evaluated in MD Clinic for gait disturbance and possible NPH ultimately underwent VPS placement, 12 of those at our institution. Of those, 11 had post-operative CGIs between 1 (very much improved) and 3 (minimally improved). Only one patient had no change after surgery. In the patients that underwent high-volume lumbar puncture (LP) as part of evaluation for possible NPH, a higher percent change in gait speed and lower post-LP CGI were associated with surgery, but not necessarily with more positive post-surgical outcome. Conclusions: In general, patients undergoing VPS placement for probable NPH after evaluation in MD Clinic had positive outcomes, with improvement in gait dysfunction. However, measures such as percent change in gait speed after high-volume lumbar puncture, frequently used to predict response to VPS, were not necessarily predictive of the degree of improvement after surgery. Disclosure: Dr. Tate has nothing to disclose. Dr. Siddiqui has nothing to disclose.

Cybernetic knee prosthesis: application of an adaptive central pattern generator

PurposeThe purpose of this paper is to generate a virtual knee angle reference to be followed by a knee prosthesis control, using an adaptive central pattern generator (CPG). Also, to study the feasibility of this approach to implement a continuous control strategy on the prosthesis.Design/methodology/approachA CPG based on amplitude controlled phase oscillators (ACPOs) to track the current percentage of gait cycle on the prosthesis is proposed. Then, the virtual knee angle reference is generated along gait cycle, by interpolation with the corresponding angle of a sound knee. The structure and coupling of the CPG, as well as the control strategy are presented.FindingsThe coupling of the CPG with real gait on the prosthesis was proven, regardless of gait speed. Also, it was found that the maximum knee angle reached during walking is proportional to gait speed. Finally, generation of virtual knee angle reference to be followed by a prosthesis is demonstrated.Research limitations/implicationsAs only one event detected along gait cycle was used to update the CPG phase, the response to gait speed changes might be slow. Updating the CPG with more events remains for a future work.Practical implicationsThe coupling of the CPG with real gait on the prosthesis results in a continuous gait cycle tracker, useful for any control strategy to be applied.Originality/valueIt is the first time a bio‐inspired concept as CPGs is applied to the prosthetic field. This could mean the beginning of a new era of cybernetic prostheses, which reproduce the lost limb and also the control functions of it.