Biomechanical, psychosocial and individual risk factors for low back disorder have been studied extensively however few researchers have examined all three risk factors. The objective of this was to develop a low back disorder risk model in furniture distribution workers using biomechanical, psychosocial and individual risk factors.
This was a prospective study with a six month follow-up time. There were 454 subjects at 9 furniture distribution facilities enrolled in the study. Biomechanical exposure was evaluated using the American Conference of Governmental Industrial Hygienists (2001) lifting threshold limit values for low back injury risk. Psychosocial and individual risk factors were evaluated via questionnaires. Low back health functional status was measured using the lumbar motion monitor. Low back disorder cases were defined as a loss of low back functional performance of −0.14 or more.
There were 92 cases of meaningful loss in low back functional performance and 185 non cases. A multivariate logistic regression model included baseline functional performance probability, facility, perceived workload, intermediated reach distance number of exertions above threshold limit values, job tenure manual material handling, and age combined to provide a model sensitivity of 68.5% and specificity of 71.9%. Interpretation: The results of this study indicate which biomechanical, individual and psychosocial risk factors are important as well as how much of each risk factor is too much resulting in increased risk of low back disorder among furniture distribution workers.
Low back disorder; Psychosocial; Biomechanical; ACGIH
Instrumented measurement of asymmetry in anterior-posterior knee laxity is commonly used to assess anterior cruciate ligament integrity. Significant advances in arthrometric technology and data visualization have occurred since first generation arthrometers. However, little has changed with regard to diagnostic criteria employed. To our knowledge, no investigations have assessed the shape of laxity curves to diagnose anterior cruciate ligament (ACL) deficiency. We hypothesized that linear stiffness and compliance after positive curve inflection would be more sensitive and specific to anterior cruciate ligament injury than current measures and would require data from the involved limb only.
Laxity curves were obtained from 130 knees on 65 subjects (Anterior Cruciate Injured n=15, Controls n=50) using a CompuKT Knee Ligament Arthrometer. Traditional diagnostic variables and novel descriptive curve-shape variables [(1) inflection point, (2) pre- and post-inflection linear stiffness and (3) a modified compliance index based on the post-inflection linear stiffness] were assessed for sensitivity to anterior cruciate ligament deficiency. Statistical interactions were evaluated using 2-by-2 ANOVA.
Significant interactions (p<0.001) were identified for laxity symmetry, stiffness, compliance index and modified compliance index. Modified compliance index predicted anterior cruciate ligament deficiency with the highest sensitivity (93%) and specificity (100%). For a test performed on a single limb, modified compliance index demonstrated 98% sensitivity and 80% specificity.
The modified compliance index is a highly sensitive and specific measure to diagnose anterior cruciate ligament deficiency, and may serve as a simple and accurate diagnostic tool for individuals without a healthy contralateral limb.
knee laxity; ACL; knee injury; knee arthrometer
Charcot-Marie-Tooth disease is the most common inherited nerve disorder and typically presents with pes cavus foot deformity and ankle equinus during childhood. Level in the variation of symmetry of musculoskeletal lower limb involvement across the clinical population is unknown, despite early reports describing gross asymmetry.
We measured foot alignment and ankle flexibility of the left and right limbs using accurate and reliable standardised paediatric outcome measures in 172 patients aged 3–20 years with a variety of disease subtypes recruited from the United States, United Kingdom, Italy and Australia.
While a large range of differences existed between left and right feet for a small proportion of children, there was no overall significant difference between limbs.
There are two important implications of these findings. Children with Charcot-Marie-Tooth disease generally exhibit symmetrical foot alignment and ankle flexibility between limbs. As such, analysing one limb only for biomechanical-related research is appropriate and satisfies the independence requirements for statistical analysis. However, because there are large differences between feet for a small proportion of children, an individualised limb-focused approach to clinical care is required.
Foot; ankle; Charcot-Marie-Tooth disease; Foot Posture Index; children; pes cavus
Reducing weight-bearing stress to diabetic foot ulcers is critical to healing and commonly called offloading. Removable cast walkers are frequently used for offloading; however, patient compliance is often poor. Walkers commonly extend to the knee. Patients complain about walkers' weight and diminished balance with their use. This study compared the offloading capacity of walkers that varied by height. Heights included: knee, ankle, and shoe levels. To ensure a fair comparison the outsole and insole were standardized across the devices.
Eleven diabetic subjects with moderate to high risk of ulceration were recruited. Subjects completed four 20 m walking trials. Subjects performed one trial with each walker and one trial with an athletic shoe. Primary outcomes focused on plantar loading and were measured by pressure insoles. Secondary outcomes were associated with gait kinematics as collected by body worn sensors.
Significant differences were found for the peak pressure and pressure time integrals of the different footwear. All walkers performed better than the athletic shoe. The ankle and knee-high devices performed best. Center of mass rotation data showed a trend of the ankle walker yielding a smaller range of motion (18% medial/lateral and 22% anterior/posterior) than the knee level.
The ankle-high walker was able to provide similar offloading capacities as the knee-high walker. The diminished weight, along with potentially improved stability, may result in improved compliance with ankle-high walkers. A study comparing the use of the two devices for treating ulcers is now suggested.
Offloading; Diabetic foot ulcer; Diabetes; Pedobarography
A potential source of patellofemoral pain, one of the most common problems of the knee, is believed to be altered patellofemoral kinematics due to a force imbalance around the knee. Although no definitive etiology for this imbalance has been found, a weak vastus medialis is considered a primary factor. Therefore, this study’s purpose was to determine how the loss of vastus medialis obliquus force alters three-dimensional in vivo knee joint kinematics during a volitional extension task.
Eighteen asymptomatic female subjects with no history of knee pain or pathology participated in this IRB approved study. During the first visit, the patellofemoral and tibiofemoral kinematics were derived from velocity data acquired using dynamic cine-phase contrast MRI. The same kinematics were then acquired immediately after administering a motor branch block to the vastus medialis obliquus using 3–5cc of 1% lidocaine. A repeated measures analysis of variance was used to test the null hypothesis that the post- and pre-injection kinematics were no different.
The null hypothesis was rejected for patellofemoral lateral shift (p=0.003, max change=1.8mm, standard deviation=1.7mm), tibiofemoral lateral shift (p<0.001, max change=2.1mm, standard deviation=2.9mm), and tibiofemoral external rotation (p<0.001, max change=3.7°, standard deviation=4.4°).
The loss of vastus medialis obliquus function produced kinematic changes that mirrored the axial plane kinematics seen in individuals with patellofemoral pain, but could not account for the full extent of these changes. Thus, vastus medialis weakness is likely a major factor in, but not the sole source of, altered patellofemoral kinematics in such individuals.
MRI; patella; tibia; femur; correlation; muscle; function; dynamic; quadriceps
Fall prevention for older adults is dependent on the ability to maintain protective balance. This study measured the short-term changes of protective stepping following waist-pull perturbations in the medio-lateral direction, to identify what, if any, properties of protective stepping are improved with repeated perturbation exposures.
Sixty waist-pulls (2 directions × 5 intensities × 6 repetitions) from a single session were analyzed separately as early, middle, and late testing periods, for a comparison over time of typical responses. Outcome measures included the number of evoked steps, type of step, incidence of interlimb collisions, and kinematic and kinetic properties of the first step in frequently used crossover-type responses.
Improvements were evident as significantly reduced number of steps and collisions. However, these improvements could not be completely accounted for by significant changes in first step kinematic or kinetic properties.
We infer that older individuals experiencing repeated lateral waist-pull perturbations optimize the predictive or feed-forward motor control for balance recovery through stepping.
The purpose of this study was to use magnetic resonance imaging to measure the moment arm of the flexor digitorum superficialis tendon about the metacarpophalangeal joint of the index, middle, ring, and little fingers when the position and force production level of the index finger was altered. A secondary goal was to create regression models using anthropometric data to predict moment arms of the flexor digitorum superficialis about the metacarpophalangeal joint of each finger.
The hands of subjects were scanned using a 3.0T magnetic resonance imaging scanner. The metacarpophalangeal joint of the index finger was placed in: flexion, neutral, and extension. For each joint configuration subjects produced no active force (passive condition) and exerted a flexion force to resist a load at the fingertip (active condition).
The following was found: (1) The moment arm of the flexor digitorum superficialis at the metacarpophalangeal joint of the index finger (a) increased with the joint flexion and stayed unchanged with finger extension; and (b) decreased with the increase of force at the neutral and extended finger postures and did not change at the flexed posture. (2) The moment arms of the flexor digitorum superficialis tendon of the middle, ring, and little fingers (a) did not change when the index metacarpophalangeal joint position changed (p > 0.20); and (b) The moment arms of the middle and little fingers increased when the index finger actively produced force at the flexed metacarpophalangeal joint posture. (4) The moment arms showed a high correlation with anthropometric measurements.
Moment arms of the flexor digitorum superficialis change due to both changes in joint angle and muscle activation; they scale with various anthropometric measures.
MRI; moment arm; flexor digitorum superficialis; finger interaction
Amputees walk with an asymmetrical gait, which may lead to future musculoskeletal degenerative changes. The purpose of this study was to compare the gait asymmetry of active transfemoral amputees while using a passive mechanical knee joint or a microprocessor-controlled knee joint.
Objective 3D gait measurements were obtained in 15 subjects (12 men and 3 women; age 42, range 26–57). Research participants were longtime users of a mechanical prosthesis (mean 20 years, range 3–36 years). Joint symmetry was calculated using a novel method that includes the entire waveform throughout the gait cycle.
There was no significant difference in hip, knee and ankle kinematics symmetry when using the different knee prostheses. In contrast, the results demonstrated a significant improvement in lower extremity joint kinetics symmetry when using the microprocessor-controlled knee.
Use of the microprocessor-controlled knee joint resulted in improved gait symmetry. These improvements may lead to a reduction in the degenerative musculoskeletal changes often experienced by amputees.
amputee; artificial limbs; gait; knee; microprocessor
Anterior cruciate ligament rupture is the most common knee ligament injury sustained by active individuals, and the relative injury risk is sex-specific. Women not only demonstrate an increased risk for injury, but also a poorer response following ligament rupture. Perturbation training has shown positive results in healthy females, but gender-specific responses to training after injury have not been evaluated. The purpose of this investigation was to describe the effects of perturbation training on the gait characteristics of male and female non-copers.
Biomechanical data were collected before and after training on 12 male and nine female non-copers using standard motion analysis techniques. Subjects walked at a consistent, self-selected speed over an embedded force plate. Data from both limbs were post-processed and analyzed using a mixed model analysis of variance and minimal clinically important differences to compare the limb behaviors of men and women.
Prior to training, only women demonstrated significant hip joint excursion asymmetry (ES = 1.03; P = 0.009). Minimal clinically important difference values showed the involved limb of the women had reduced hip and knee flexion angles and moments, truncated knee excursions, and increased hip excursions when compared to their own uninvolved limb and the limbs of the male non-copers. Following training, only knee extensor moment values exceeded the minimal clinically important differences in the women.
Female non-copers demonstrated unique movement strategies following injury and perturbation training. Women may be a meaningful subgroup of non-copers, and future investigations should consider the effects of gender in the outcomes of non-copers.
anterior cruciate ligament injury; gait; neuromuscular training; gender differences
Joint instability has been suggested as a risk factor for knee osteoarthritis and a cause of significant functional declines in those with symptomatic disease. However, the relationship between altered knee joint mechanics and self-reports of instability in individuals with knee osteoarthritis remains unclear.
Fourteen subjects with knee osteoarthritis and complaints of joint instability and 12 control volunteers with no history of knee disease were recruited for this study. Dynamic stereo X-ray technology was used to assess the three-dimensional kinematics of the knee joint during the loading response phase of gait.
Individuals with concurrent knee osteoarthritis and joint instability demonstrated significantly reduced flexion and internal/external rotation knee motion excursions during the loading response phase of gait (P < 0.01), while the total abduction/adduction range of motion was increased (P < 0.05). In addition, the coronal and transverse plane alignment of the knee joint at initial contact was significantly different (P < 0.05) for individuals with concurrent knee osteoarthritis and joint instability. However, the anteroposterior and mediolateral tibiofemoral joint positions at initial contact and the corresponding total joint translations were similar between groups during the loading phase of gait.
The rotational patterns of tibiofemoral joint motion and joint alignments reported for individuals with concurrent knee osteoarthritis and joint instability are consistent with those previously established for individuals with knee osteoarthritis. Furthermore, the findings of similar translatory tibiofemoral motion between groups suggest that self-reports of episodic joint instability in individuals with knee osteoarthritis may not necessarily be associated with adaptive alterations in joint arthrokinematics.
Knee Instability; Knee Osteoarthritis; Arthrokinematics
Articular cartilage of young healthy individuals is dynamic and responsive to loading behaviors. The purpose of this study was to evaluate the relationship of cartilage T1ρ and T2 relaxation times with loading kinetics during jumping tasks in healthy young individuals.
Fourteen healthy subjects underwent: 1) motion analysis while performing a unilateral hopping task and bilateral drop jumping task; and 2) quantitative imaging using a 3 Tesla MRI for T1ρ and T2 relaxation time analysis. Three dimensional net joint moments and angular impulse was calculated using standard inverse dynamics equations. Average T1ρ and T2 relaxation times and medial-lateral ratios for each were calculated. Multiple regression was used to identify predictors of cartilage relaxation times.
Average knee flexion moment during hopping was observed to best predict overall T1ρ (R2=.185) and T2 (R2=.154) values. Peak knee adduction moment during a drop jump was the best predictor of the T1ρ medial-lateral ratio (R2=.220). The T2 medial-lateral ratio was best predicted by average internal rotation moment during the drop jump (R2=.174).
These data suggest that loads across the knee may affect the biochemistry of the cartilage. In young healthy individuals, higher flexion moments were associated with decreased T1ρ and T2 values, suggesting a potentially beneficial effect. The medial-to-lateral ratio of T1ρ and T2 times appears to be related to the frontal and transverse plane joint mechanics. These data offer promising findings of potentially modifiable parameters associated with cartilage composition.
MRI; Motion analysis; Biomechanics; Cartilage; Osteoarthritis
Physical activity is frequently reported in rheumatology but it is difficult to measure objectively outside the gait laboratory. A new generation of activity monitors offers this potential but it has not yet been evaluated in patients with rheumatoid arthritis. This study aimed to evaluate three types of activity monitors in patients with rheumatoid arthritis.
The Step-N-Tune, Activ4Life Pro V3.8, and the Intelligent Device for Energy Expenditure and Activity activity monitors were tested concurrently in 12 patients with rheumatoid arthritis as well as in a healthy control group of 12 volunteers. Participants walked at a self selected speed for two minutes and were filmed for later review. Temporal and spatial gait parameters were also validated against the GAITRite walkway and the total number of steps recorded by each activity monitor was compared to a gold standard derived from half speed video replays.
Activity monitor performance varied between devices but all showed poorer performance when used in the group with rheumatoid arthritis. Bland–Altman plots demonstrated wider 95% limits of agreement in the group with rheumatoid arthritis and a systematic decrease in agreement between activity monitors and the gold standard with decreasing functional ability.
Despite some variation between devices, all the activity monitors tested performed reasonably well in healthy young volunteers. All except the Activ4Life showed a marked decrease in performance in patients with rheumatoid arthritis, suggesting Activ4Life could be the most suitable for use in this patient group. The marked between group difference in functional ability, and systematic decrease in device performance with deteriorating gait, indicate that activity monitors require specific validation in target clinical populations.
Rheumatoid arthritis; Physical activity; Activity monitor
The purpose of this study was to estimate the loading environment for the distal femur during a novel standing exercise paradigm for people with spinal cord injury.
A mathematical model based on experimentally derived parameters.
Musculoskeletal deterioration is common after spinal cord injury, often resulting in osteoporotic bone and increased risk of lower extremity fracture. Potential mechanical treatments have yet to be shown to be efficacious; however, no previous attempts have been made to quantify the lower extremity loading during passive, active, and active–resistive stance.
A static, 2-D model was developed to estimate the external forces; the activated quadriceps forces; and the overall bone compression and shear forces in the distal femur during passive (total support of frame), active (quadriceps activated minimally), and active–resistive (quadriceps activated against a resistance) stance.
Passive, active, and active–resistive stance resulted in maximal distal femur compression estimates of ~45%, ~75%, and ~240% of body weight, respectively. Quadriceps force estimates peaked at 190% of body weight with active–resistive stance. The distal femur shear force estimates never exceeded 24% of body weight with any form of stance.
These results support our hypothesis that active–resistive stance induces the highest lower extremity loads of the three stance paradigms, while keeping shear to a minimum.
This model allows clinicians to better understand the lower extremity forces resulting from passive, active, and active–resistive stance in individuals with spinal cord injury.
Functional electrical stimulation (FES); Exercise; Bone; Osteoporosis; Paralysis; Rehabilitation; Compression; Shear
Studies suggest that 50% of children with cerebral palsy are prescribed ankle foot orthoses. One of the aims of ankle foot orthosis use is to aid in walking. This research examined the effects that ankle foot orthoses have on the energy recovery and the mechanical work performed by children with cerebral palsy during walking.
Twenty-one children with spastic diplegia walked with and without their prescribed bilateral ankle foot orthoses. Ten of the subjects wore articulated (hinged) orthoses and 11 subjects wore solid orthoses. Three dimensional kinematic data were collected and between and within group repeated measures ANOVAs were applied to the dependent measures.
The results were similar for both groups. There was an increase in stride length, energy recovery, and potential energy and the kinetic energy variation. There was no change in the mechanical work performed to walk or the normalized center of mass vertical excursion. Unfortunately, the increase in energy recovery did not alter the external work, as it was offset by increased variation in the potential and kinetic energies of the center of mass. There was a great deal of variability in the measured work, with both large increases and decreases in the work of individual subjects when wearing orthoses.
These results suggest that current ankle foot orthoses can reduce the work to walk, but do not do so for many children with cerebral palsy. This research suggests that ankle foot orthosis prescription could be aided by measuring the mechanical work during walking.
Weakness is often profound in the contralesional hand after stroke. Relative contributions of various neural and mechanical mechanisms to this impairment, however, have not been quantified. In this study, the extent of one potential contributor, muscle atrophy, was noninvasively assessed in index finger musculature using ultrasonographic techniques.
Twenty-five stroke survivors (45–65 years old) with severe hand impairment resulting from a stroke occurring 2–4 years prior participated, along with 10 age-matched control subjects. Muscle cross sectional area and thickness were geometrically measured from ultrasound images on both limbs of participants.
Muscle size on the paretic limb of stroke survivors was smaller for all 7 hand muscles investigated. An average difference of 15% (SD 4) was seen for muscle cross sectional area and 11% (SD 2) for muscle thickness, while the difference between the dominant and non-dominant limbs for control subjects (6% (SD 2) and 1% (SD 4) for the muscle cross sectional area and muscle thickness, respectively) was not significant.
Although muscle atrophy was detected in the paretic limb following stroke, it is not explanatory of the marked impairment in strength seen in this stroke population. However, other alterations in muscle morphology, such as fatty infiltrations and changes in fiber structure, may contribute to the emergent muscle weakness post-stroke.
hand; stroke; muscle; atrophy; ultrasound
Lateral epicondylosis is a prevalent and costly musculoskeletal disorder characterized by degeneration of the common extensor tendon origin at the lateral epicondyle. Grip strength is commonly affected due to lateral epicondylosis. However, less is known about the effect of lateral epicondylosis on other functional parameters such as ability to react to rapid loading.
Twenty-nine lateral epicondylosis participants and ten controls participated in a case-control study comparing mechanical parameters (mass, stiffness and damping), magnetic resonance imaging signal intensity and grip strength of injured and uninjured limbs. A mixed effects model was used to assess the effect of dominance and injury on mechanical parameters and grip strength.
Significant effect of injury and dominance was observed on stiffness, damping and grip strength. An injured upper limb had, on average, 18% less stiffness (p<0.01, 95% CI [9.8%, 26%]), 21% less damping (p<0.01, 95% CI [11%, 31%]) and 50% less grip strength (p<0.01, 95% CI [37%, 61%]) than an uninjured upper limb. The dominant limb had on average 15% more stiffness (p<0.01, 95% CI [8.0%, 23%], 33% more damping (p<0.01, 95% CI [22%, 45%]), and 24% more grip strength (p<0.01, 95% CI [6.6%, 44%]) than the non-dominant limb.
Lower mechanical parameters are indicative of a lower capacity to oppose rapidly rising forces and quantify an important aspect of upper limb function. For individuals engaged in manual or repetitive activities involving the upper limb, a reduction in ability to oppose these forces may result in increased risk for injury or recurrence.
lateral epicondylosis; tennis elbow; upper limb function; mechanical parameters; hand dominance
Spinal cord injury affects walking balance control, which necessitates methods to quantify balance ability. The purposes of this study were to 1) examine walking balance through foot placement variability post-injury; 2) assess the relationship between measures of variability and clinical balance assessments; and 3) determine if spatial parameter variability might be used as a clinical correlate for more complex balance measurements.
Ten persons with spinal cord injury walked without devices on a split-belt treadmill at self-selected speeds. Ten healthy controls walked at 0.3 and 0.6 m/s for comparison. Variability of step width and length, anteroposterior and mediolateral foot placements relative to center-of-mass, and margin-of-stability were calculated. Clinical assessments included Berg Balance Scale and Dynamic Gait Index.
Participants with spinal cord injury demonstrated significantly different variability in all biomechanical measures compared to controls (P≤0.007). Berg Balance Scale scores were significantly inversely associated with step length as well as anteroposterior and mediolateral foot placement variability (P≤0.05). Dynamic Gait Index scores were significantly inversely associated with mediolateral foot placement variability (P≤0.05). Participants with spinal cord injury showed significant correlations between spatial parameter variability and all other measures (P≤0.005), except between step length and margin-of-stability (P=0.068); controls revealed fewer correlations.
Persons post-spinal cord injury exhibit an abnormal amount of stepping variability when challenged to walk without devices, yet preserve the ability to avoid falling. When complex laboratory measures of variability are unavailable clinically, spatial parameter variability or standardized balance assessments may be plausible indicators of walking balance control.
spinal cord injury; walking; balance; margin of stability; variability
Very little is known about the effects of applied torque about the long axis of the tibia in combination with muscle loads on anterior cruciate ligament biomechanics. The purpose of this study was to determine the effect of muscle contraction and tibial torques applied about the long axis of the tibia on anterior cruciate ligament strain behavior.
Six cadaver knee specimens were used to measure the strain behaviour of the anterior cruciate ligament. Internal and external axial torques were applied to the tibia when the knee was between 30° and 120° of flexion in combination with the conditions of no muscle load, isolated quadriceps load, and simultaneous quadriceps and hamstring loading.
The highest anterior cruciate ligament strain values were measured when the muscles were not loaded, when the knee was at 120° of flexion, and when internal tibial torques were applied to the knee. During muscle loading the highest anterior cruciate ligament strain values were measured at 30° of flexion and then the strain values gradually decreased with increase in knee flexion. During co-contraction of the quadriceps and hamstring muscles the anterior cruciate ligament was unstrained or minimally strained at 60°, 90° and 120° of knee flexion.
This study suggests that quadriceps and hamstring muscle co-contraction has a potential role in reducing the anterior cruciate ligament strain values when the knee is in deep flexion. These results can be used to gain insight into anterior cruciate ligament injury mechanisms and to design rehabilitation regimens.
Knee; anterior cruciate ligament; biomechanics
Research has linked knee extensor moment and knee shear force to the non-contact anterior cruciate ligament injury during the landing motion. However, how these biomechanical performance factors relate to knee translations in vivo it is not known as knee translations cannot be obtained with traditional motion capture techniques. The purpose of this study was to combine traditional motion capture with high-speed, biplane fluoroscopy imaging to determine relationships between knee extensor moment and knee shear force profiles with anterior and lateral tibial translations occurring during drop landing in females athletes.
15 females performed drop landings from a height of 40 cm while being recorded using a high speed, biplane fluoroscopy system and simultaneously being recorded using surface marker motion capture techniques to estimate knee joint angle, reaction force and moment profiles.
No significant statistical relationships were observed between peak anterior or posterior knee shear force and peak anterior and lateral tibial translations; or, between peak knee extensor moment and peak anterior and lateral tibial translations. Although differences were noted in peak shear force (P = 0.02) and peak knee extensor moment (P < 0.001) after stratification into low and high shear force and moment cohorts, no differences were noted in anterior and lateral tibial translations (all P ≥ 0.18).
Females exhibiting high knee extensor moment and knee shear force during drop landings do not yield correspondingly high anterior and lateral tibial translations.
Biomechanics; ACL injury risk factors; Neuromuscular Training; ACL Injury Prevention
Step-up exercise is one of the most commonly utilized exercises during rehabilitation of patients after both ACL injury and reconstruction. Currently, insurance providers increasingly required a trial of intensified rehabilitation before surgical reconstruction is attempted. The purpose of this study was to investigate whether this “safe” rehabilitation exercise in the setting of ACL deficiency can cause altered knee kinematics.
Thirty patients with unilateral ACL rupture were recruited for this study. The mean time from injury was 3.3 months. Tibiofemoral kinematics were determined during a step-up exercise using a combination of MRI, dual fluoroscopy and advanced computer modeling.
The ACL-injured knee displayed an average 5° greater external tibial rotation than the uninjured knee (p<0.05), during the last 30% of step-up. The ACL-injured knee also demonstrated on average 2.5 mm greater anterior tibial shift during the last 40% of stance phase (p<0.01). In addition, during the last 30% of stance the tibia of the ACL-deficient knee tended to shift more medially (~1 mm) as the knee approached full extension (p<0.01).
The data confirmed the initial hypothesis as it was found that ACL deficient knees demonstrated significantly increased anterior tibial translation, medial tibial translation and external tibial rotation towards the end of the step-up as the knee approached full extension. Intensive rehabilitation utilizing the step-up exercise in the setting of ACL deficiency can potentially introduce repetitive microtrauma by way of altered kinematics.
To investigate the relationships among hip joint moments produced during functional activities and hip bone mass in sedentary older adults.
Eight male and eight female older adults (70–85 yr) performed functional activities including walking, chair sit–stand–sit, and stair stepping at a self-selected pace while instrumented for biomechanical analysis. Bone mass at proximal femur, femoral neck, and greater trochanter were measured by dual-energy X-ray absorptiometry. Three-dimensional hip moments were obtained using a six-camera motion analysis system, force platforms, and inverse dynamics techniques. Pearson’s correlation coefficients were employed to assess the relationships among hip bone mass, height, weight, age, and joint moments. Stepwise regression analyses were performed to determine the factors that significantly predicted bone mass using all significant variables identified in the correlation analysis.
Hip bone mass was not significantly correlated with moments during activities in men. Conversely, in women bone mass at all sites were significantly correlated with weight, moments generated with stepping, and moments generated with walking (p < 0.05 to p < 0.001). Regression analysis results further indicated that the overall moments during stepping independently predicted up to 93% of the variability in bone mass at femoral neck and proximal femur; whereas weight independently predicted up to 92% of the variability in bone mass at greater trochanter.
Submaximal loading events produced during functional activities were highly correlated with hip bone mass in sedentary older women, but not men. The findings may ultimately be used to modify exercise prescription for the preservation of bone mass.
Bone mineral density; Functional activity; Hip; Joint moment; Submaximal loads
To determine the effects of two different prosthetic feet on the three-dimensional kinetic patterns of both the prosthetic and sound limbs during unilateral trans-tibial amputee gait.
Eleven individuals with a unilateral trans-tibial amputation participated in two walking sessions: once while using the conventional SAFE foot, the other while using the dynamic Flex foot.
Despite the wide variation in the design of prosthetic feet, the benefits of these prostheses remain unclear.
During each test session, peak joint moments and powers in the sagittal, transverse and frontal planes were examined, as subjects walked at a comfortable speed.
The majority of the kinetic differences that occurred due to the changing of prosthetic foot type were limited to ankle joint variables in the sagittal plane with greater peak moments and power during propulsion for the Flex foot compared to the SAFE foot. However, effects were also found at joints proximal to the prosthesis (e.g. knee) and differences were also found in the kinetics of the sound limb.
The dynamic Flex foot allowed subjects to rely more heavily on the prosthetic foot for propulsion and stability during walking with minimal compensations at the remaining joints.
Determining the biomechanical differences between the conventional and dynamic prosthetic feet may advocate the use of one prosthetic foot type over another. This information, when used in conjunction with subjective preferences, may contribute to higher functioning and greater satisfaction for individuals with a lower limb amputation.
PMID: 15234485 CAMSID: cams2412
trans-tibial amputation; prosthetic foot; gait
To quantify the limits of stability during a leaning/reaching task and determine 1) test-retest reliability and 2) effect of movement direction and foot support.
Test-retest reliability design.
Seated reaching and leaning are used in rehabilitation programs to assess and train sitting balance and motor function. Continuous (as opposed to ordinal), multidirectional measures of seated postural stability have not been previously presented.
12 older adults performed a seated reaching/leaning task while net body centre of pressure displacement and velocity were measured with three forceplates (under buttocks and each foot) over two separate days. Conditions of movement direction (forward, backward, lateral) and foot support (with and without) were randomized.
Except for the backward movement in the supported foot condition, all measures had moderate to very high reliability. Measurements were sensitive to both foot support and movement direction.
PMID: 12206950 CAMSID: cams2411
postural control; forceplate; sitting balance; reliability
Antagonistic activation of abdominal muscles and raised intra-abdominal pressure are associated with both spinal unloading and spinal stabilization. Rehabilitation regimens have been proposed to improve spinal stability via selective recruitment of certain trunk muscle groups. This biomechanical study used an analytical model to address whether lumbar spinal stability is increased by selective activation of abdominal muscles.
The biomechanical model included anatomically realistic three-layers of curved abdominal musculature connected by fascia, rectus abdominis and 77 symmetrical pairs of dorsal muscles. The muscle activations were calculated with the model loaded with either flexion, extension, lateral bending or axial rotation moments up to 60 Nm, along with intra-abdominal pressure up to 5 or 10 kPa (37.5 or 75 mm Hg) and partial bodyweight. After solving for muscle forces, a buckling analysis quantified spinal stability. Subsequently, different patterns of muscle activation were studied by forcing activation of selected abdominal muscles to at least 10% or 20% of maximum.
The spinal stability increased by an average factor of 1.8 with doubling of intra-abdominal pressure. Forced activation of obliques or transversus abdominis muscles to at least 10% of maximum increased stability slightly for efforts other than flexion, but forcing at least 20% activation generally did not produce further increase in stability. Forced activation of rectus abdominis did not increase stability.
Based on predictions from an analytical spinal buckling model, the degree of stability was not substantially influenced by selective forcing of muscle activation. This casts doubt on the supposed mechanism of action of specific abdominal muscle exercise regimens that have been proposed for low back pain rehabilitation.
Abdominal muscles; Biomechanics; Stability; Rehabilitation