Influence of femoral anteversion on proximal femoral loading: measurement and simulation in four patients

OBJECTIVE: The aim of this study was to determine the loading of the proximal femur during daily activities and to quantify the influence of femoral anteversion. DESIGN: This study combined experimental and analytical approaches to determine the in vivo loading at the hip joint. A numerical musculo-skeletal model was validated against measured in vivo hip contact forces and then used to analyse the influence of anteversion on the loading conditions in the femur. BACKGROUND: Musculo-skeletal loading of long bones is essential for joint replacement and fracture healing. Although joint contact forces have previously been measured in selected patients, the interaction between femoral anteversion and the associated musculo-skeletal loading environment remains unknown. METHODS: The gait of four patients with force measuring hip prostheses was analysed during walking and stair-climbing. Musculo-skeletal loading was determined using individual numerical models by minimising the sum of the muscle forces. RESULTS: Experimentally and numerically determined hip contact forces agreed both qualitatively and quantitatively. Muscle activity resulted in compression of the femur and small shear forces in the meta- and epi-physeal regions. Increasing the anteversion to an angle of 30 degrees increased hip contact forces and bending moments up to 28%. CONCLUSIONS: This study has shown that femoral anteversion has a strong influence on the musculo-skeletal loading environment in the proximal femur. RELEVANCE: Detailed musculo-skeletal modelling may allow pre-surgical, patient specific optimisation of loading on implant, bone and soft tissues.     

A comparison of kinetic gait parameters for 3-13 year olds

BACKGROUND: Normative gait data is essential for diagnosing and treating abnormal gait patterns. The examination of the onset of adult-like kinetic gait patterns in children has generated inconsistent results. The purpose of this study was to identify age-related differences in kinematic and kinetic gait parameters across children aged 3-13 years old. METHODS: A motion capture system and three force plates were employed to compute sagittal joint angles and joint kinetics during walking and compare results between children aged 3-4 years (n=13), 5-6 years (n=10), 7-8 years (n=12), and 9-13 years (n=12). Anthropometric data was estimated using a mathematical model (elliptical cylinder method). Peak flexion and extension joint angles and moments, and peak concentric and eccentric joint powers were analyzed using multivariate analyses of variance. FINDINGS: For most of the variables examined, similar results were obtained across age groups. Reduced peak hip flexion moments and knee extension moments were observed in the 3-4 year olds compared to the oldest group of walkers. Compared to the 9-13 year olds, reduced ankle joint moments and power were observed in most age groups. INTERPRETATION: The results suggest that adult-like kinetic patterns for the hip and knee were attained by 5 years of age. However, for the ankle joint, adult-like patterns are not achieved until nine years of age or older. These findings stress the importance of using age-matched normative data for clinical gait analysis.     

Load moments about the hip and knee joints during ergometer cycling

The aim of the study was to calculate the magnitudes of moments of force acting about the bilateral hip and knee joint axes during ergometer cycling. Six healthy subjects pedalled a weight-braked bicycle ergometer at different workloads, pedalling rates, saddle heights and pedal foot position. During cycling at 120 Watts, 60 revolutions per minute with mid-saddle height and anterior pedal foot position, the mean peak flexing and extending hip load moments were 34.3 and 8.9 Nm, respectively. Mean peak flexing knee load moments was 28.8 Nm and extending moment was 11.9 Nm. Hip load moments were significantly increased by increasing the ergometer workload or pedalling rate. For knee load moments, workload was the most important factor. The flexing knee load moment did not change with changes in pedalling rate. Different saddle heights or pedal food positions had a slight but not always statistically significant influence on the hip and knee joint loads. The maximum hip and knee joint load moments induced during cycling were small compared with those obtained during other exercises or normal activities such as level walking, stair climbing, and lifting.     

Effects of exercise on bone density,balance, and self-efficacy in older women

The effects of weighted vest walking and strength-training exercises on bone mineral density (BMD), balance, strength, and self-efficacy were tested in older women. Eighteen women, age 69.2 +/- 3.5 years, were randomly assigned to an exercise group (EG) (n = 9), or a sedentary control group (CG) (n = 9). The EG participated in 32 weeks (three 1-h sessions/week) of supervised strength training and walking, stair climbing, and balance exercises while wearing weighted vests. The CG did not exercise. All women took Ca2+ and vitamin D during the study period. Measures included 1) BMD of the hip and lumbar spine measured by dual-energy X-ray absorptiometry, 2) strength, 3) balance, and 4) scores on a self-efficacy instrument. The EG had significant improvements in bone density of the femoral neck and balance and a significant weight loss (P < 0.05). There were no changes in self-efficacy in either group.     

Explaining the hip adduction moment variability during gait: Implications for hip abductor strengthening

Background

There is emerging interest in hip abductor function during gait and its potential relationship to knee joint pathology. During gait, the hip abductor muscles are primarily responsible for generating moments of force to control frontal plane movement. The current study investigated the relationship between hip abductor muscle function and frontal plane hip moments of force during gait.

Methods

Frontal plane hip moments of force and electromyographic features of gluteus medius were measured during walking in 22 healthy individuals. Hip abductor strength, subject anthropometrics and gait velocity were recorded. Multiple regression models were used to evaluate the relationship between the anthropometric, velocity, strength and electromyographic variables and the initial and mid-stance magnitude of the hip adduction moment.

Findings

A positive relationship was found between the initial peak moment (Nm), and both body mass and gait speed (R² = 90%). Body mass (positive) and hip abductor strength (negative) explained significant levels of mid-stance magnitude variability (R² = 62.5%). Gait speed (positive) explained significant levels of variability in the normalized initial peak moment (Nm/kg) (R² = 52%). No variables were included in the normalized mid-stance moment model (P > 0.05).

Interpretation

Body mass was the key factor associated with high hip adduction moments during initial and mid-stance of the gait cycle. Increased gait velocity was associated with higher initial peaks and higher muscle strength was associated with lower mid-stance magnitude of the external hip adductor moment during walking. These findings suggest that in a healthy adult population, hip abductor strength and activation were not directly related to the hip adduction moment magnitude during gait.     

Passive elastic contribution of hip extensors to joint moments during walking in people with low back pain

BackgroundIt has been found that alterations in passive muscle properties may be associated with low back pain, and these may be responsible for the altered gait parameters often observed in subjects with back pain. The purpose of the present study was to assess total hip and passive hip extensor moments in people with or without low back pain during the hip flexion component of walking.Methods52 subjects volunteered for this study (low back pain group, n = 25 (male n = 13, female n = 12), control group, n = 27 (male n = 15, female n = 12)). Passive hip moments were calculated using an adapted force transducer during supine testing. A biomechanical model and predictive equation were used to calculate passive hip moments during walking. Total hip moments were calculated with the use of a 9 camera, 3-D motion-capture system.FindingsIndependent samples t-tests demonstrated no significant differences between groups for gait parameters or hip or knee angles. Results of the ANOVAs demonstrated significant differences in passive hip flexor moments during the second half of hip flexion (P < 0.05).There were also significant differences in hip power and work done during peaks of power absorption and the second peak of power generation (P < 0.05).InterpretationThe present data demonstrates that subjects with low back pain have altered passive hip extensor and total power and work done during walking compared with healthy controls. Biomechanical models should include individual measurements of passive joint moments.     

Joint kinetics during Tai Chi gait and normal walking gait in young and elderly Tai Chi Chuan practitioners

BACKGROUND: Tai Chi Chuan is becoming a popular exercise among elders. This study measured the inter-segmental forces and moments at the lower extremity joints during a Tai Chi gait as compared to those during normal walking gait, in both apparently healthy young and elderly Tai Chi Chuan practitioners. METHODS: Three-dimensional inter-segmental joint reaction force and moment were computed using the Inverse Dynamic Approach based on the kinematics and ground reaction force measurements in a laboratory setting in six young (two females, mean age 28; SD 6 years) and six elderly (five females, mean age 72; SD 8 years) subjects who had previous training of Yang style Tai Chi Chuan. FINDINGS: The results showed significant gait differences in both age groups, with significantly smaller peak compressive forces, larger peak shear forces in the ankle, knee and hip joints, and larger peak moments in the knee and hip joints during Tai Chi gait as compared to normal gait. Moreover, the peak shear force was oriented more in the medial-lateral direction at the ankle and knee joints, and the peak moment was in the frontal plane at the knee and hip joints. The results also showed significant age differences, with significantly smaller peak shear forces in all three joints in the elderly group than in the young group during Tai Chi gait. INTERPRETATION: Tai Chi gait has an increased shear force and frontal plane torque at lower extremity joints than normal gait. The shear force at all three lower extremity joints during Tai Chi gait is lower in the elderly subjects than young subjects. This data suggest that, in Tai Chi Chuan training, elderly people with degenerative joint diseases in the lower extremity should use caution when practicing Tai Chi Chuan.     

Changes in knee moments with contralateral versus ipsilateral cane usage in females with knee osteoarthritis

BACKGROUND: Conservative treatment for osteoarthritis often involves educating the patient in methods of decreasing the load transmitted through the diseased joint. The use of a cane is one such method and the correct placement of the cane with respect to an abnormal knee joint is crucial. The purpose of this study was to compare effects on knee moments of force of contralateral versus ipsilateral cane usage in female subjects with osteoarthritic knees. METHODS: A convenience sample of 14 subjects volunteered for this study. Subjects walked over force platforms while ground reaction force and three-dimensional kinematic data were captured using a Vicon 370 System. The subjects were tested walking: (a) unaided, (b) with ipsilateral cane, and (c) with contralateral cane. Inverse dynamics were employed to calculate temporal-spatial, kinematic and kinetic variables. Dependent variables included hip and knee frontal plane and sagittal plane moments of force, walking speed, cadence and stride length. Repeated measures ANOVA assessed differences among walking conditions. FINDINGS: Subjects walked significantly faster in the unaided gait condition owing to a higher cadence. Ipsilateral cane use resulted in significantly larger hip (versus contralateral P=0.018; versus unaided P=0.036) and knee (versus contralateral P=0.043; versus unaided P=0.030) frontal plane peak moments during gait. Contralateral cane placement was associated with the smallest peak knee abductor (P=<0.001) and flexor (P=<0.001) moments. Knee deformity (varus or valgus) did not have any significant effect on any variable possibly due to small sample size. INTERPRETATION: The results suggest that as is the case for the hip contralateral cane placement is the most efficacious for persons with knee osteoarthritis. In fact, no cane use may be preferable to ipsilateral cane usage as the latter resulted in the highest knee moments of force, a situation which may exacerbate pain and deformity.     

The relationship of lower-extremity muscle torque to locomotor performance in people with stroke

BACKGROUND AND PURPOSE: Improved walking is a common goal after stroke. The purpose of this study was to examine the relationship between the torque generated by the muscles of both lower extremities and 2 locomotor tasks: gait on level surfaces and stair climbing in people who had strokes. SUBJECTS: Twenty community-dwelling individuals (mean age=61.2 years, SD=8.4, range=52-82) who had strokes and who were able to walk independently participated in the study. The mean time since stroke was 4.0 years (SD=2.6, range=1.5-10.0). METHODS: Pearson correlations and multiple regression were used to measure the relationship between concentric isokinetic torque of the flexor and extensor muscles of the hip, knee, and ankle bilaterally and locomotor performance (gait on level surfaces and stair-climbing speed). RESULTS: The isokinetic torques of the paretic ankle plantar flexors, hip flexors, and knee flexors had moderate to high correlations (r=.5-.8) with gait and stair-climbing speeds. Muscle force could explain 66% to 72% of the variability in gait and stair-climbing speeds. Correlations for the nonparetic side were as high as or higher than those for the paretic side for some muscle groups. DISCUSSION AND CONCLUSION: Muscle performance measurements of both limbs should be included in the evaluation of locomotion and treatment of people following a stroke.     

Comparison of Hip and Low Back Loads between Normal Gait,Axillary Crutch Ambulation and Walking with a Hands-free Crutch in a Healthy Population

BackgroundInstead of using axillary crutches, using a hands-free crutch (HFC) has been associated with higher functional outcome scores. However, hip and back pain have been reported as side effects.Purpose/HypothesisThe purpose of this study was to compare range of motion and joint reaction forces at the hip and low back between HFC walking, normal walking, and standard crutch walking. It was hypothesized that hip joint reaction forces and low back joint reaction forces would be higher with HFC walking compared with normal walking and axillary crutch walking.Study DesignControlled Laboratory StudyMethodsUsing 3D motion analysis and force plates, kinematics and ground reaction forces were measured in 12 healthy subjects during gait, crutch ambulation and HFC walking. Gait speed, hip and trunk range of motion, and hip and low back reaction forces, were compared using repeated-measures ANOVA.ResultsGait speed during HFC ambulation was reduced 33% compared to crutch ambulation (P<0.001) and 44% compared to normal gait (p<0.001). Hip range of motion was reduced during both crutch conditions compared to gait (p<0.001). Trunk range of motion was greatest during HFC walking compared to both gait and crutch ambulation (p<0.001). Peak hip joint reaction force during HFC walking was 11% lower than during gait (p=0.026) and 30% lower than during crutch walking (p<0.001). Peak low back reaction force during HFC walking was 18% higher than during gait (p=0.032) but not different than during crutch walking.ConclusionHip joint reaction forces during HFC walking did not exceed those during gait or axillary crutch ambulation. However, a reduction in hip motion using the HFC was associated with increases in trunk motion and low-back loading. These could be a cause for reports of low-back pain accompanying HFC usage.Level of EvidenceLevel 3     

The hip joint: structure, stability, and stress; a review.

A review of the structure of the hip joint as related to its stability is presented. The forces exerted at the hip and along the proximal end of the femur are discussed in relation to the anatomical position of bone and to normal stresses incurred during standing and gait. Clinical considerations of selected hip abnormalities include a review of changes in normal mechanical forces found in coxa valga, coxa vava, arthritis, and fracture.     

Effects of a home program on strength, walking speed, and function after total hip replacement

OBJECTIVE: To assess the efficacy of a home exercise program in increasing hip muscle strength, walking speed, and function in patients more than 1.5 years after total hip replacement (THR). DESIGN: Randomized controlled trial. SETTING: Kinesiology laboratory. PARTICIPANTS: Fifty-three patients with unilateral THR were randomly assigned to the training (n=26) and control (n=27) groups. Patients in the training group were further divided into exercise-high (n=13) and exercise-low (n=13) compliance groups according to their practice ratio (high, > or =50%). INTERVENTION: The training group underwent a 12-week home program that included hip flexion range of motion exercises for both hip joints; strengthening exercises for bilateral hip flexors, extensors, and abductors; and a 30-minute walk every day. The control group did not receive any training. MAIN OUTCOME MEASURES: Strength of bilateral hip muscles, free and fast walking speeds while walking over 3 different terrains, and functional performance were assessed by using a dynamometer, videotape analysis, and the functional activity part of the Harris Hip Score, respectively, before and after the 12-week period. RESULTS: Subjects in the exercise-high compliance group showed significantly (P <.05) greater improvement in muscle strength for the operated hip, fast walking speed, and functional score than those in the exercise-low compliance and control groups. CONCLUSIONS: The designed home program was effective in improving hip muscle strength, walking speed, and function in patients after THR who practiced the program at least 3 times a week, but adherence to this home program may be a problem.     

Joint loading and bone mineral density in persons with unilateral, trans-tibial amputation

Background. Persons with unilateral, lower-extremity amputation sometimes develop osteoarthritis in the intact limb. The purpose of this study was to investigate gait mechanics and bone mineral density in unilateral, trans-tibial amputees to test the hypotheses that the intact limb knee and hip will have larger frontal plane net joint moments and bone mineral density than the prosthetic side and the limbs of control subjects.

Methods. Proximal tibia and femoral neck bone mineral density and gait mechanics were measured from nine subjects with a unilateral, trans-tibial amputation and from age, gender, and mass matched control subjects.

Findings. The amputee intact proximal tibia bone mineral density and peak knee internal abduction moment were 45% (P = 0.001) and 56% (P = 0.028) greater, respectively, than the prosthetic side. The intact limb femoral neck bone mineral density and peak hip internal abduction moment were 12% (P = 0.095) and 33% (P = 0.03) greater, respectively, than the prosthetic side. The intact knee frontal plane moment and bone mineral density were moderately larger than the control knee, while the intact and control hip were similar.

Interpretation. Elevated frontal plane net joint moments and bone mineral density suggest the potential exists for premature knee joint degradation. Measuring frontal plane joint mechanics and bone mineral density may be important tools for assessing joint health in persons with unilateral, trans-tibial amputation.     

A home exercise program for tibial bone strengthening based on in vivo strain measurements

OBJECTIVE: To compare the strain and strain rates generated during lower limb calisthenics with walking, an exercise that has been found to have only minimal effect on bone mass. Strengthening of bone, while it still has adaptive ability, can be achieved by exercise. Mechanical loading during physical activity produces strains and strain rates within the bones. It is thought that strain and strain rates higher than the usual provide the stimulus for the bones' adaptation. DESIGN: Three strain-gauged bone staples were inserted percutaneously in a 30 degrees rosette pattern in the medial aspect of the midtibial diaphysis of two volunteers. The principal compression, tension, shear strains, and strain rates were measured during various lower limb calisthenics and compared with those of jogging and walking. RESULTS: Zig-zag hopping was in the grouping of exercises with the highest principal compression, tension, and shear strains and compression strain rates, whereas walking was in the lowest or next-to-the-lowest grouping for all principal strain or strain rates. CONCLUSION: Zig-zag hopping, based on the high strain and strain rates that it produces, may be an optimal tibial bone-strengthening exercise.     

Genetic determinants of bone mass in adults. A twin study.

The relative importance of genetic factors in determining bone mass in different parts of the skeleton is poorly understood. Lumbar spine and proximal femur bone mineral density and forearm bone mineral content were measured by photon absorptiometry in 38 monozygotic and 27 dizygotic twin pairs. Bone mineral density was significantly more highly correlated in monozygotic than in dizygotic twins for the spine and proximal femur and in the forearm of premenopausal twin pairs, which is consistent with significant genetic contributions to bone mass at all these sites. The lesser genetic contribution to proximal femur and distal forearm bone mass compared with the spine suggests that environmental factors are of greater importance in the aetiology of osteopenia of the hip and wrist. This is the first demonstration of a genetic contribution to bone mass of the spine and proximal femur in adults and confirms similar findings of the forearm. Furthermore, bivariate analysis suggested that a single gene or set of genes determines bone mass at all sites.     

Effect of a hip flexor-stretching program on gait in the elderly

OBJECTIVES: To test whether a reduction in peak hip extension during the terminal stance phase of walking in elderly compared with young adult subjects represents a hip flexor contracture impairment rather than some dynamic consequence and to test the hypothesis that stretching the hip flexors improves both static and dynamic peak hip extension, as well as other age-related gait changes about the ankle. DESIGN: A double-blinded, randomized, controlled trial. SETTING: Stretching exercises were performed in the subjects' homes. Pre- and postassessments were performed in a gait laboratory. PARTICIPANTS: Ninety-six healthy elderly individuals in 2 groups: treatment (n=47) and control (n=49). INTERVENTION: The treatment group received a 1-time instruction in hip flexor stretching, whereas the control group received a 1-time instruction in shoulder abductor stretching. Participants in each group were asked to perform stretching exercises on their own twice daily for 10 weeks. MAIN OUTCOME MEASURES: Static and dynamic peak hip extension, peak anterior pelvic tilt, and other peak kinematic and kinetic variables during the gait cycle. RESULTS: There was a modest improvement in static peak hip extension as measured by a goniometer within the treatment group (mean +/- standard deviation, 6.1 degrees +/-2.5 degrees to 7.7 degrees +/-3.6 degrees, P=.032) compared with no change in the control group. At comfortable walking speed, dynamic hip extension tended to increase in the treatment group (5.1 degrees +/-9.7 degrees to 7.1 degrees +/-8.0 degrees, P=.103) compared with no real change in the control group (5.3 degrees +/-8.9 degrees to 5.4 degrees +/-7.5 degrees, P=.928). Similarly, at fast walking speed, dynamic hip extension tended to increase in the treatment group (6.4 degrees +/-9.8 degrees to 8.4 degrees +/-8.0 degrees, P=.093) compared with no change in the control group. Changes in ankle kinematics and kinetics included a significant improvement in peak ankle plantarflexion and a tendency to improved ankle power generation. CONCLUSION: The static and dynamic trends to improvement in peak hip extension were of similar magnitude, suggesting that age-related reduction in peak hip extension during gait is the result of a static hip flexion contracture rather than a dynamic consequence. Additionally, age-related changes in ankle kinematics and kinetics may be secondarily related to hip flexion contracture impairment rather than impairment at the ankle per se. This study was limited by the exercises being unsupervised and relying on 1-time instruction. A more rigorous and supervised hip flexor-stretching exercise program may yield more substantial improvements in gait parameters.     

A comparative study between axial compression and lateral fall configuration tested in a rat proximal femur model

BACKGROUND: Conventional testing method for evaluation of rat hip failure force is based on an axial compression approach. However, as the most osteoporotic hip fractures are a result of a lateral fall, it is necessary to establish mechanical testing methods more close to clinical conditions. This study was therefore designed to evaluate the differences in hip mechanical failure force to be tested between 'axial compression' and 'lateral fall configuration' in a rat proximal femur model. METHODS: Eighteen 10-month-old female Wistar rats were body-weight matched and divided into ovariectomized group (n = 9) and sham group (n = 9). All rats were euthanized 3 months after surgery. The bilateral proximal femora of each rat were excised. The left femur served for testing to failure in a fall configuration fashion while the right femur was tested using axial compression approach. After mechanical testing, the anterior-posterior radiographs were taken to identify the fracture mode and measure the Pauwel's angle between the fracture line and the line perpendicular to the femoral shaft long axis. FINDINGS: The failure force in fall configuration was significantly correlated with but lower than that tested in axial compression. A comparison between the ovariectomized and sham group showed that the failure force in both fall configuration and axial compression was found significantly higher in the sham group than that in the ovariectomized group. However, the logistic regression analysis revealed that the fall configuration approach had larger discrimination power. Radiographs showed that almost all samples fractured at the base of the femur neck. The Pauwel's angle in fall configuration group was significantly larger than that in axial compression group. INTERPRETATION: In comparison with the characteristics of axial compression test, the fall configuration approach generated higher shearing stress with larger bending moment to the bone and induced susceptibility to fracture at lower mechanical load. Although the failure force obtained from the two testing configurations revealed significant correlation, the mechanical testing in fall configuration demonstrated higher sensitivity in identifying the estrogen-deficiency induced deterioration of hip mechanical failure force as compared with that in axial compression. These findings suggested the potential application of lateral fall configuration in evaluation of improvement effects of intervention stratagems on hip mechanical failure force involving an ovariectomized rat model.