Daina L. Sturnieks

Repeatability of gait data using a functional hip joint centre and a mean helical knee axis

Repeatability of traditional kinematic and kinetic models is affected by the ability to accurately locate anatomical landmarks (ALs) to define joint centres and anatomical coordinate systems. Numerical methods that define joint centres and axes of rotation independent of ALs may also improve the repeatability of kinematic and kinetic data. The purpose of this paper was to compare the repeatability of gait data obtained from two models, one based on ALs (AL model), and the other incorporating a functional method to define hip joint centres and a mean helical axis to define knee joint flexion/extension axes (FUN model). A foot calibration rig was also developed to define the foot segment independent of ALs. The FUN model produced slightly more repeatable hip and knee joint kinematic and kinetic data than the AL model, with the advantage of not having to accurately locate ALs. Repeatability of the models was similar comparing within-tester sessions to between-tester sessions. The FUN model may also produce more repeatable data than the AL model in subject populations where location of ALs is difficult. The foot calibration rig employed in both the AL and FUN model provided an easy alternative to define the foot segment and obtain repeatable data, without accurately locating ALs on the foot.

Balance disorders in the elderly.

Good balance is an imperative skill for daily life that requires the complex integration of sensory information regarding the position of the body relative to the surroundings and the ability to generate appropriate motor responses to control body movement. Balance calls upon contributions from vision, vestibular sense, proprioception, muscle strength and reaction time. With increased age, there is a progressive loss of functioning of these systems which can contribute to balance deficits. Balance disorders represent a growing public health concern due to the association with falls and fall-related injuries, particularly in regions of the world in which high proportions of the population are elderly. Falls present one of the most serious and costly problems associated with older adulthood. Falls can mark the beginning of a decline in function and independence and are the leading cause of injury-related hospitalisation in older people. One in three people over the age of 65 years who are living in the community experience at least one fall each year and 10-15% of these falls are associated with serious injury. In economic terms, the direct and indirect costs associated with falls are large and will grow as the proportion of older people increases. Consequently, understanding age-related changes in the physiological systems imperative to balance is of utmost importance to prevent falls in older people and reduce the injury-related burden on individuals and society.

Mild Cognitive Impairment as a Predictor of Falls in Community-Dwelling Older People

OBJECTIVE : Incidence of falls in people with cognitive impairment with or without a formal diagnosis of dementia is estimated to be twice that of cognitively intact older adults. This study aimed to investigate whether mild cognitive impairment (MCI) is associated with falls in older people. DESIGN : Prospective cohort study. SETTING : Community sample, Sydney Memory and Ageing Study. PARTICIPANTS : A total of 419 nondemented community-dwelling adults, age 70-90 years. MEASUREMENTS : A comprehensive neuropsychological test battery measuring four cognitive domains provided classification being with or without MCI on the basis of objective published criteria. Assessments of medical, physiologic, and psychological measures were also performed. Fallers were defined as people who had at least one injurious fall or at least two noninjurious falls during a 12-month follow-up period. RESULTS : Of the participants, 342 (81.6%) had normal cognitive functioning, 58 (13.8%) had nonamnestic MCI, and 19 (4.5%) had amnestic MCI. People with MCI performed worse than people without MCI in measures of general health and balance. Logistic regression analyses showed that fall risk was significantly greater in people with MCI (odds ratio [OR]: 1.72, 95% confidence interval [95% CI]: 1.03-2.89). This association was mainly apparent when the analysis was restricted to those with nonamnestic MCI (OR: 1.98, 95% CI: 1.11-3.53), where the relationship was primarily explained by impaired executive functioning (OR: 1.27, 95% CI: 1.02-1.59). CONCLUSION : The findings indicate that objectively defined MCI is an independent risk factor for injurious or multiple falls in a representative sample of community-dwelling older people. The presence of nonamnestic MCI, based primarily on executive function, was found to be an important factor in increasing fall risk.

Concern About Falls Elicits Changes in Gait Parameters in Conditions of Postural Threat in Older People

BACKGROUND Previous studies have indicated that gait patterns in older people may be affected by concern about falling. The aim of this study was to examine the effects of concern about falling and physiological falls risk on gait performance using a paradigm in which concern about falling was experimentally induced. METHODS Forty-four community-living older adults (17 men, 27 women) with a mean age of 76.8 (standard deviation = 5.2) years walked at self-selected speeds on the floor and on a 60-cm elevated walkway in normal and dim lighting conditions. Temporal and spatial gait parameters, muscle activity, measures of physiological arousal, physiological falls risk, and concern about falls were assessed. RESULTS Physiological falls risk was associated with slower walking speeds in all conditions including the optimal (floor) condition (p = .029). In the elevated walkway conditions, concern about falls (both self-report and as indicated by physiological arousal) was increased and participants walked more slowly, took shorter steps, decreased their cadence, and spent more time in double support (p < .005). Disproportionately large reductions in walking speed were evident in participants with greater concern about falling (p = .018). CONCLUSIONS These findings suggest that walking performance is influenced by both physiological and psychological factors. Physiological falls risk appears to determine walking speed under optimal conditions, whereas concern about falling elicits greater (possibly excessive) gait adjustments under conditions of postural threat.

Consequences of lower extremity and trunk muscle fatigue on balance and functional tasks in older people: A systematic literature review

BackgroundMuscle fatigue reduces muscle strength and balance control in young people. It is not clear whether fatigue resistance seen in older persons leads to different effects. In order to understand whether muscle fatigue may increase fall risk in older persons, a systematic literature review aimed to summarize knowledge on the effects of lower extremity and trunk muscle fatigue on balance and functional tasks in older people was performed.MethodsStudies were identified with searches of the PUBMED and SCOPUS data bases.Papers describing effects of lower extremity or trunk muscle fatigue protocols on balance or functional tasks in older people were included. Studies were compared with regards to study population characteristics, fatigue protocol, and balance and functional task outcomes.ResultsSeven out of 266 studies met the inclusion criteria. Primary findings were: fatigue via resistance exercises to lower limb and trunk muscles induces postural instability during quiet standing; induced hip, knee and ankle muscle fatigue impairs functional reach, reduces the speed and power of sit-to-stand repetitions, and produces less stable and more variable walking patterns; effects of age on degree of fatigue and rate of recovery from fatigue are inconsistent across studies, with these disparities likely due to differences in the fatigue protocols, study populations and outcome measures.ConclusionTaken together, the findings suggest that balance and functional task performance are impaired with fatigue. Future studies should assess whether fatigue is related to increased risk of falling and whether exercise interventions may decrease fatigue effects.

The physiology of falling: assessment and prevention strategies for older people.

Balance calls upon contributions from vision, peripheral sensation, vestibular sense, muscle strength, neuromuscular control and reaction time. With increased age, there is a progressive loss of functioning of these systems and an increased likelihood of falls. Falls can mark the beginning of a decline in function and independence and are the leading cause of injury-related hospitalisation in older people. By using simple tests of vision, leg sensation, muscle strength, reaction time and standing balance, it is possible to identify accurately older people at risk of falls and assess intervention outcomes. This approach overcomes the limitations associated with traditional methods of assessing falls risk via medical diagnoses, including varied severity between individuals. Using a physiological approach provides information at the impairment and functional capacity levels to assist in understanding falls and developing and evaluating optimal falls prevention strategies for older people.

Knee joint biomechanics following arthroscopic partial meniscectomy

We investigated spatiotemporal data, joint kinematics, and joint kinetics during gait in a group of subjects who had recently undergone arthroscopic partial meniscectomy and compared the results to those of healthy controls. Gait analysis was performed on 105 pain‐free meniscectomy patients and 47 controls, walking at a self‐selected speed. The meniscectomy population was comparable to controls in spatiotemporal parameters and knee kinematics. However, they had reduced range of motion (ROM) and lower peak moments in the sagittal plane on the operated limb compared to the nonoperated limb. Compared to controls, the meniscectomy patients had significantly larger knee adduction moments over stance, even after accounting for their greater body weight. These differences likely increase articular loads on the medial compartment of the tibiofemoral joint and may contribute to the high risk of knee osteoarthritis following arthroscopic meniscal surgery.

The association between choice stepping reaction time and falls in older adults—a path analysis model

BACKGROUND choice stepping reaction time (CSRT) is a functional measure that has been shown to significantly discriminate older fallers from non-fallers. OBJECTIVE to investigate how physiological and cognitive factors mediate the association between CSRT performance and multiple falls by use of path analysis. METHODS 294 retirement-village residents, aged 62-95 years, undertook CSRT tests, requiring them to step onto one of four randomly illuminated panels, in addition to physiological and cognitive tests. Number of falls was collected during 1-year follow-up. RESULTS 79 participants (27%) reported two or more falls during the follow-up period. Regression analyses indicated CSRT was able to predict multiple falls by a factor of 1.76 for each SD change. The path analysis model revealed that the association between CSRT and multiple falls was mediated entirely by the physiological parameters reaction time and balance (postural sway) performance. These two parameters were in turn mediated over a physiological path (by quadriceps strength and visual contrast sensitivity) and a cognitive path (cognitive processing). CONCLUSIONS this study provides an example of how path analysis can reveal mediators for the association between a functional measure and falls. Our model identified inter-relationships (with relative weights) between physiological and cognitive factors, CSRT and multiple falls.

Knee Strength and Knee Adduction Moments following Arthroscopic Partial Meniscectomy

PURPOSE This study investigated the relationship between muscular strength about the knee and knee joint moments during gait in patients who had undergone arthroscopic partial meniscectomy (APM). METHODS One hundred and two APM patients and 42 age-matched nonoperated controls underwent strength testing and three-dimensional gait analysis. Patients were divided into weak and normal subgroups and compared with controls for spatiotemporal, kinematic, and kinetic gait parameters. RESULTS Spatiotemporal parameters, kinematics, and sagittal plane kinetics were similar between APM patients and controls. The APM group displayed weaker concentric knee extension and flexion strength compared with controls. The weak APM subgroup had an increased average and peak knee adduction moments over stance compared with the APM subgroup with normal strength levels and controls. The normal strength APM subgroup had a larger peak knee adduction moment in early stance compared with controls. CONCLUSION Achieving normal lower limb muscle strength following APM appears important to resume normal frontal plane loading of the knee while walking.

Force-controlled balance perturbations associated with falls in older people: a prospective cohort study.

Balance recovery from an unpredictable postural perturbation can be a challenging task for many older people and poor recovery could contribute to their risk of falls. This study examined associations between responses to unpredictable perturbations and fall risk in older people. 242 older adults (80.0±4.4 years) underwent assessments of stepping responses to multi-directional force-controlled waist-pull perturbations. Participants returned monthly falls calendars for the subsequent 12 months. Future falls were associated with lower force thresholds for stepping in the posterior and lateral but not anterior directions. Those with lower posterior force thresholds for stepping were 68% more likely to fall at home than those with higher force thresholds for stepping. These results suggest that amount of force that can be withstood following an unpredictable balance perturbation predicts future falls in community-dwelling older adults. Perturbations in the posterior direction best discriminated between future fallers and non-fallers.