Relationship between bone strength index of the hemiparetic tibial diaphysis and muscle strength in people with chronic stroke: influence of muscle contraction type and speed.

This study was conducted to examine the association between the tibial bone strength index and leg muscle strength of different contraction types and speeds among people with chronic stroke. We found that concentric muscle power at moderate speed was more associated with tibial bone strength index than other types. INTRODUCTION: To compare the influence of muscle strength of different contraction types and speeds on the bone strength index of tibial diaphysis in people with chronic stroke. METHODS: Eighty individuals with chronic stroke (age: 62.6 ± 8.0 years; men/women: 46/34; post-stroke duration: 9.0 ± 5.4 years) underwent scanning of the tibia at the 66% site on both sides using peripheral quantitative computed tomography. Each participant was also evaluated for isometric and dynamic (at 60°/s and 120°/s) strength of knee flexors/extensors and ankle dorsiflexors/plantarflexors using an isokinetic dynamometer. For a given contraction type and speed, the strength values of the four muscle groups were summed to yield a composite score. Multiple regression analysis was used to identify the association of the percent side-to-side difference (%SSD) in tibial polar-stress-strain index (p-SSI) with %SSD in muscle strength of different contraction types and speeds. RESULTS: The p-SSI and all muscle strength parameters on the paretic side had lower values than the non-paretic side (p ≤ 0.001). The %SSD in concentric muscle power at angular speed of 60°/s (R2 = 0.317, p = 0.006) and 120°/s (R2 = 0.298, p = 0.020) remained independently associated with that in p-SSI, after controlling for age, sex, body mass index, post-stroke duration, motor impairment, spasticity, and physical activity level. The effect of isometric strength and eccentric muscle power was not significant in multivariate analysis. CONCLUSIONS: Concentric muscle power was more predictive of %SSD in p-SSI at the tibial diaphysis than other contraction types and may be an important target for intervention to promote bone health in people with chronic stroke.

The impact of stroke on bone properties and muscle-bone relationship: a systematic review and meta-analysis.

To systematically review available evidence related to the characteristics of bone changes post-stroke and the relationship between various aspects of muscle function (e.g., strength, spasticity) and bone properties after stroke onset. An extensive online database search was undertaken (last search in January 2019). Articles that examined the bone properties in stroke patients were included. The quality of the studies was evaluated with the National Institutes of Health (NIH) Study Quality Assessment Tools. Publication bias of meta-analyses was assessed using the Egger's regression asymmetry test. The selection and evaluation of the articles were conducted by two independent researchers. Fifty-nine studies were identified. In subacute and chronic stroke studies, the skeletal sites in the paretic limbs sustained a more pronounced decline in bone quality than did their counterparts in the non-paretic limbs. The rate of changes showed a decelerating trend as post-stroke duration increased, but the timing of achieving the steady rate differed across skeletal sites. The magnitude of bone changes in the paretic upper limb was more pronounced than the paretic lower limb. There was a strong relationship between muscle strength/mass and bone density/strength index. Muscle spasticity seemed to have a negative impact on bone integrity in the paretic upper limb, but its influence on bone properties in the paretic lower limb was uncertain. Substantial bone changes in the paretic limbs occurred particularly in the first few months after stroke onset. Early intervention, muscle strength training, and long-term management strategies may be important to enhance bone health post-stroke. This review has also revealed the knowledge gaps which should be addressed in future research.

Chronic effects of stroke on hip bone density and tibial morphology: a longitudinal study.

UNLABELLED: The study aimed to quantify the long-term effects of stroke on tibial bone morphology and hip bone density. Only the trabecular bone mineral density and bone strength index in the hemiparetic tibial distal epiphysis showed a significant decline among individuals who had sustained a stroke 12-24 months ago. INTRODUCTION: This study aims to determine the changes in bone density and morphology in lower limb long bones during a 1-year follow-up period and their relationship to muscle function in chronic stroke patients. METHODS: Twenty-eight chronic stroke patients (12-166 months after the acute stroke event at initial assessment) and 27 controls underwent bilateral scanning of the hip and tibia using dual-energy X-ray absorptiometry and peripheral quantitative computed tomography, respectively. Each subject was re-assessed 1 year after the initial assessment. RESULTS: Twenty stroke cases and 23 controls completed all assessments. At the end of the follow-up, the paretic tibial distal epiphysis suffered significant decline in trabecular bone density (-1.8 ± 0.6 %, p = 0.006) and bone strength index (-2.7 ± 0.6 %, p < 0.001). More severe decline in the former was associated with poorer leg muscle strength (ρ = 0.447, p = 0.048) and motor recovery (ρ = 0.489, p = 0.029) measured at initial assessment. The loss in trabecular bone density remained significant among those whose stroke onset was 12-24 months ago (p < 0.001), but not among those whose stroke onset was beyond 24 months ago (p > 0.05) at the time of initial assessment. The changes of outcomes in the tibial diaphysis, except for cortical bone mineral content on the non-paretic side (-1.3 ± 0.3 %, p = 0.003), and hip bone density were well within the margin of error for precision. CONCLUSIONS: There is evidence of continuous trabecular bone loss in the paretic tibial distal epiphysis among chronic stroke patients, but it tends to plateau after 2 years of stroke onset. The steady state may have been reached earlier in the hip and tibial diaphysis.

Psychometric properties of dual-task balance assessments for older adults: a systematic review.

BACKGROUND: The ability to maintain balance while simultaneously performing a cognitive task is essential for daily living and has been implicated as a risk factor of falls in older adults. AIMS: To evaluate the evidence related to the psychometric properties of dual-task balance assessments in older adults. METHODS: An extensive literature search of electronic databases was conducted. Articles were included if they evaluated the psychometric properties of dual-task balance assessment tools in older adults. The data were extracted by two independent researchers and confirmed with the principal investigator. The methodology quality of each study was rated by using the Consensus-based Standards for the Selection of Health Measurement Instruments (COSMIN) checklist. RESULTS: Twenty-six articles were included in this systematic review. For dual-task static standing balance assessments, the center of pressure-related parameters (displacement, velocity) and reaction time measurements were reliable but not useful for prediction of falls. For walking balance assessments, the gait outcomes derived generally demonstrated good to excellent reliability (intraclass correlation coefficient >0.75), but their ability to predict falls varied. Outcomes derived from the cognitive tasks and the dual-task cost (dual-task performance minus single-task performance) mostly demonstrated low to fair reliability. The methodological quality of majority of studies was poor to fair, mainly due to small sample size. CONCLUSIONS: Among the dual-task balance assessments examined, the reliability and validity varied. The findings of this review should be useful in guiding the selection of dual-task balance measures in future research.

Influence of chronic stroke impairments on bone strength index of the tibial distal epiphysis and diaphysis.

SUMMARY: The influence of various stroke impairments on bone health is poorly understood. This study showed that muscle function and small artery compliance were more strongly associated with the bone strength index at the tibial diaphyseal and epiphyseal regions, respectively. These impairments should be targeted in promoting bone health post-stroke. INTRODUCTION: This study examined the bone structural properties of the tibial distal epiphysis and diaphysis after chronic stroke and identified the clinical correlates of the bone strength index measured at these sites. METHODS: The tibial distal epiphysis (4% site) and diaphysis (66% site) were scanned on both sides in 66 chronic stroke patients and 23 control participants using peripheral quantitative computed tomography. Dynamic knee muscle strength, balance function, spasticity, arterial compliance, and endurance were also measured in the stroke group. RESULTS: At the 4% site, multivariate analysis showed a significant side×group interaction effect (Wilk's lambda=3.977, p<0.001), with significant side-to-side differences in total volumetric bone mineral density (vBMD), trabecular vBMD, and bone strength index in the stroke group, but not in the control group. A significant side×group interaction was also found at the 66% site (Wilk's lambda=4.464, p<0.001), with significant side-to-side differences in cortical vBMD, cortical area, cortical thickness, and bone strength index in the stroke group only. Balance and endurance were independently associated with bone strength index at both tibial sites in the paretic leg (p<0.05) after adjusting for relevant factors in multivariate regression analysis. Small artery compliance and muscle strength were significantly associated with the bone strength index at the 4% site and 66% site, respectively. CONCLUSIONS: The influence of various stroke impairments on bone was region-specific. While muscle function was more strongly associated with the bone strength index in the diaphyseal region, the effect of vascular health was more apparent in the tibial epiphysis in the paretic leg.

Voxel-based approach to generate entire human metacarpal bone with microscopic architecture for finite element analysis.

With the development of micro-computed tomography (micro-CT) technology, it is possible to construct three-dimensional (3D) models of human bone without destruction of samples and predict mechanical behavior of bone using finite element analysis (FEA). However, due to large number of elements required for constructing the FE models of entire bone, this demands a substantial computational effort and the analysis usually needs a high level of computer. In this article, a voxel-based approach for generation of FE models of entire bone with microscopic architecture from micro-CT image data is proposed. To enable the FE analyses of entire bone to be run even on a general personal computer, grayscale intensity thresholds were adopted to reduce the amount of elements. Human metacarpal bone (MCP) bone was used as an example for demonstrating the applicability of the proposed method. The micro-CT images of the MCP bone were combined and converted into 3D array of pixels. Dual grayscale intensity threshold parameters were used to distinguish the pixels of bone tissues from those of surrounding soft tissues and improve predictive accuracy for the FE analyses with different sizes of elements. The method of selecting an appropriate value of the second grayscale intensity threshold was also suggested to minimize the area error for the reconstructed cross-sections of a FE structure. Experimental results showed that the entire FE MCP bone with microscopic architecture could be modeled and analyzed on a personal computer with reasonable accuracy.

The effects of whole-body vibration therapy on bone turnover, muscle strength, motor function, and spasticity in chronic stroke: a randomized controlled trial.

BACKGROUND: Whole-body vibration (WBV) has been used in older adults to improve bone health and neuromuscular function, and may have potential applications for stroke patients. AIM: To investigate the effects of WBV on bone turnover, leg muscle strength, motor function, and spasticity among chronic stroke patients. DESIGN: Randomized controlled trial (RCT). SETTING: Community. POPULATION: Eighty-two chronic stroke patients. METHODS: The experimental group underwent exercise training with WBV stimulation for a maximum of 15 minutes, 3 days per week for 8 weeks. The controls received the same exercises without WBV. Participants were evaluated for isokinetic knee muscle strength, serum levels of bone formation and resorption markers, spasticity and motor function of the paretic leg at baseline, immediately after the 8-week training period, and 1-month follow-up. RESULTS: Intention-to-treat analysis revealed no significant changes in levels of bone turnover markers and motor function of the paretic leg over time in both groups. Muscle strength outcomes showed no significant group×time interaction, with similar significant improvements found in both groups. Spasticity of the paretic knee was significantly reduced in the experimental group (P=0.005), but not in controls (P=0.465). No serious adverse events were reported. CONCLUSION: The WBV protocol used in this study did not induce additional effects on bone turnover, knee muscle strength and paretic leg motor function among chronic stroke patients. WBV may have potential to modulate spasticity, but this requires further investigation. CLINICAL REHABILITATION IMPACT: More study on WBV is required before it can be recommended as an adjunct treatment in rehabilitation of chronic stroke patients.

Changes in bone density and geometry of the radius in chronic stroke and related factors: a one-year prospective study.

OBJECTIVES: To describe the changes in bone density and geometry of the radius after chronic stroke and the associated clinical factors. METHODS: Twenty stroke patients (12 men and 8 women, age=42-78 years, time post-stroke=12-166 months) and 23 control participants (14 men and 9 women, age=53-77 years) were assessed at the time of enrolment and one year later. Peripheral quantitative computed tomography was used to scan the radius epiphysis (4% site) and diaphysis (33% site). Grip strength, spasticity, paretic arm disuse, physical activity, and vascular health were also evaluated. RESULTS: During the follow-up period, only the cortical thickness and cortical bone mineral content (BMC) in the paretic radius diaphysis showed a decline that exceeded the least significant change value (p=0.002). Paretic arm disuse, lower vascular elasticity and physical activity level at initial assessment were significantly related to more decline in cortical thickness at this site (p<0.01). CONCLUSIONS: The paretic radius diaphysis sustained significant reduction in cortical thickness and cortical BMC over time in chronic stroke, but these changes were less pronounced than those previously reported in sub-acute stroke. Strategies to modify vascular health, disuse, and physical activity may be important in improving upper limb bone health but will need further investigations.

Relative impact of neuromuscular and cardiovascular factors on bone strength index of the hemiparetic distal radius epiphysis among individuals with chronic stroke.

UNLABELLED: The objective of this study was to examine the associations of neuromuscular and cardiovascular impairments with the bone strength index of the hemiparetic distal radius epiphysis in chronic stroke survivors. The results showed that grip strength is the most predominant predictor of the bone strength index. INTRODUCTION: The purpose of the study was to examine the associations of neuromuscular and cardiovascular impairments with the bone strength index of the hemiparetic distal radius epiphysis in chronic stroke survivors. METHODS: Sixty-five chronic stroke survivors and 34 healthy control subjects underwent scanning of the distal radius epiphyseal site on both sides using peripheral quantitative computed tomography to measure trabecular volumetric bone mineral density (vBMD) (mg/cm(3)), total vBMD (mg/cm(3)), total area (mm(2)), and compressive bone strength index (cBSI) (g(2)/cm(4)). Various indicators of neuromuscular (grip strength, spasticity) and cardiovascular function (vascular elasticity, oxygen consumption during 6-min walk test) were evaluated. RESULTS: Analysis of variance revealed a significant main effect of side (p < 0.001) and group × side interaction (p < 0.05) for total BMC, total vBMD, trabecular vBMD, and cBSI (p < 0.05), with the stroke group showing greater side-to-side difference in these variables. However, no significant side-to-side difference in total area was detected in either group (p > 0.05). Sex-specific analysis yielded similar results. Multiple regression analyses revealed that the cBSI of the hemiparetic distal radius epiphysis had a stronger association with neuromuscular factors than cardiovascular factors. Overall, grip strength was the strongest determinant of the cBSI of the hemiparetic distal radius epiphysis (p < 0.01). CONCLUSIONS: Muscle weakness is the most predominant determinant of cBSI in the hemiparetic distal radius epiphysis among chronic stroke patients. Future studies should investigate the efficacy of different muscle-strengthening strategies in enhancing bone strength of this skeletal site in the chronic stroke population.

Compromised bone strength index in the hemiparetic distal tibia epiphysis among chronic stroke patients: the association with cardiovascular function, muscle atrophy, mobility, and spasticity.

SUMMARY: The purpose of this study was to identify the determinants of the bone strength index of the distal tibia epiphysis in chronic stroke patients. The results showed that lower cardiovascular fitness, more muscle atrophy, poorer mobility, and more severe spasticity were independently associated with lower tibial bone strength index. INTRODUCTION: To identify the determinants of the bone strength index (BSI) at the distal tibia in chronic stroke patients METHODS: Sixty-three chronic stroke survivors underwent scanning of the distal tibia at the 4% site on both sides using peripheral quantitative computed tomography. The primary outcomes were trabecular bone mineral density (BMD; milligram per cubic centimeter), total BMD (milligram per cubic centimeter), total bone area (square millimeter), and BSI (square gram per centimeter to the power of four). Cardiovascular fitness, leg lean mass, gait velocity, and spasticity were also measured. RESULTS: Scans from 45 subjects were deemed to have acceptable quality and were included for subsequent analysis. The paretic side had significantly lower trabecular BMD, total BMD, and BSI than the nonparetic side (p < 0.05). However, the total bone area demonstrated no significant side-to-side difference (p > 0.05). After adjusting for relevant biological factors, peak oxygen consumption, leg muscle mass, and gait velocity remained positively associated with tibial BSI on both sides (R (2) change = 6.9-14.2%), whereas spasticity of the paretic leg was negatively associated with tibial BSI on the same side (R (2) change = 4.8%). CONCLUSIONS: Cardiovascular function, muscle atrophy, mobility, and spasticity are independently associated with BSI of the distal tibia epiphysis among chronic stroke patients.

An assessment of the osteogenic index of therapeutic exercises for stroke patients: relationship to severity of leg motor impairment.

SUMMARY: Exercise may be a viable way to promote bone health in stroke survivors. This study used the osteogenic index to evaluate the osteogenic potential of selected exercises for stroke survivors. The results show that brisk walking and stepping may be good skeletal loading exercises for this population. INTRODUCTION: Exercise may induce positive effects on bone health in stroke patients. The purpose of this study was to evaluate the osteogenic potential of selected exercises for stroke survivors. METHODS: Sixty stroke patients were categorized into group 1 (moderate to severe leg motor impairment) and group 2 (mild to moderate impairment). Each subject performed five exercises in random order: walking at self-selected speed, walking at maximal speed, stepping onto a 6-in. riser, sit-to-stand, and jumping. The peak ground reaction force (GRF) on the hemiparetic side and the number of loading cycles achieved in 1 min were determined. The osteogenic index (OI) was computed for each exercise, based on the formula: OI = Peak GRF (in body weight) x In (number of loading cycles + 1). Two-way analysis of variance was used to compare the OI among the five exercises between the two groups. RESULTS: For group 1, stepping had significantly higher OI than other exercises (p < 0.001). For group 2, both walking at maximal speed and stepping had significantly higher OI than other exercises (p < 0.001). CONCLUSIONS: Stepping had the highest OI for those with more severe leg motor impairment. Both stepping and brisk walking had superior OI for those with mild leg motor impairment.

Fall-related self-efficacy, not balance and mobility performance, is related to accidental falls in chronic stroke survivors with low bone mineral density.

UNLABELLED: Chronic stroke survivors with low hip bone density are particularly prone to fractures. This study shows that fear of falling is independently associated with falls in this population. Thus, fear of falling should not be overlooked in the prevention of fragility fractures in these patients. INTRODUCTION: Chronic stroke survivors with low bone mineral density (BMD) are particularly prone to fragility fractures. The purpose of this study was to identify the determinants of balance, mobility and falls in this sub-group of stroke patients. METHODS: Thirty-nine chronic stroke survivors with low hip BMD (T-score <-1.0) were studied. Each subject was evaluated for the following: balance, mobility, leg muscle strength, spasticity, and fall-related self-efficacy. Any falls in the past 12 months were also recorded. Multiple regression analysis was used to identify the determinants of balance and mobility performance, whereas logistic regression was used to identify the determinants of falls. RESULTS: Multiple regression analysis revealed that after adjusting for basic demographics, fall-related self-efficacy remained independently associated with balance/mobility performance (R2 = 0.494, P < 0.001). Logistic regression showed that fall-related self-efficacy, but not balance and mobility performance, was a significant determinant of falls (odds ratio: 0.18, P = 0.04). CONCLUSIONS: Fall-related self-efficacy, but not mobility and balance performance, was the most important determinant of accidental falls. This psychological factor should not be overlooked in the prevention of fragility fractures among chronic stroke survivors with low hip BMD.

Muscle weakness, spasticity and disuse contribute to demineralization and geometric changes in the radius following chronic stroke.

UNLABELLED: Bone health status of the radius in individuals with chronic stroke was evaluated using peripheral quantitative computed tomography. Bone mineral density and cortical thickness on the affected side were compromised when compared with the unaffected side. Muscle weakness, spasticity, and disuse were identified as contributing factors to such changes. INTRODUCTION: Following a stroke, demineralization and geometric changes occur in bone as a result of disuse and residual impairments, and these can contribute to an increased risk of fragility fractures. METHODS: This study used peripheral quantitative computed tomography (pQCT) to evaluate volumetric bone mineral density and geometry at the midshaft radius in people living with chronic stroke. Older individuals with chronic stroke were recruited. Each subject underwent a pQCT scan of the midshaft radius at the 30% site on both upper limbs. Muscle strength, motor function, spasticity, and chronic disuse were also evaluated. Data from 47 subjects (19 women) were assessed. RESULTS: A significant difference was found between the two limbs for cortical bone mineral content, cortical bone mineral density, cortical thickness, and polar stress-strain index. There was no significant side-to-side difference in total bone area. Percent side-to-side difference in muscle strength, spasticity, and chronic disuse were significant determinants of percent side-to-side difference in cortical bone mineral content and cortical thickness. CONCLUSIONS: The findings suggest that following chronic stroke, endosteal resorption of the midshaft radius occurred with a preservation of total bone area. Muscle weakness, spasticity, chronic disuse significantly contributed to demineralization and geometric changes in the radius following chronic stroke.

A 19-week exercise program for people with chronic stroke enhances bone geometry at the tibia: a peripheral quantitative computed tomography study.

BACKGROUND: We assessed the impact of a 19-week exercise program on bone health in chronic stroke. RESULTS: Those who underwent the program reported significantly more gain in tibial trabecular bone content and cortical bone thickness on the affected side. CONCLUSION: Regular exercise is thus beneficial for enhancing bone health in this population.