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1.  [No title available] 
PMCID: PMC3943591  PMID: 24345591
2.  [No title available] 
PMCID: PMC3943624  PMID: 24355703
3.  [No title available] 
PMCID: PMC4006952  PMID: 24332719
4.  Timing Sequence of Multi-Planar Knee Kinematics Revealed by Physiologic Cadaveric Simulation of Landing: Implications for ACL Injury Mechanism 
Background
Challenges in accurate, in vivo quantification of multi-planar knee kinematics and relevant timing sequence during high-risk injurious tasks pose challenges in understanding the relative contributions of joint loads in non-contact injury mechanisms. Biomechanical testing on human cadaveric tissue, if properly designed, offers a practical means to evaluate joint biomechanics and injury mechanisms. This study seeks to investigate detailed interactions between tibiofemoral joint multi-planar kinematics and anterior cruciate ligament strain in a cadaveric model of landing using a validated physiologic drop-stand apparatus.
Methods
Sixteen instrumented cadaveric legs, 45(SD 7) years (8 female and 8 male) were tested. Event timing sequence, change in tibiofemoral kinematics (position, angular velocity and linear acceleration) and change in anterior cruciate ligament strain were quantified.
Findings
The proposed cadaveric model demonstrated similar tibiofemoral kinematics/kinetics as reported measurements obtained from in vivo studies. While knee flexion, anterior tibial translation, knee abduction and increased anterior cruciate ligament strain initiated and reached maximum values almost simultaneously, internal tibial rotation initiated and peaked (p<0.015 for all comparisons) significantly later. Further, internal tibial rotation reached 1.8(SD 2.5)°, almost 63% of its maximum value, at the time that peak anterior cruciate ligament strain occurred, while both anterior tibial translation and knee abduction had already reached their peaks.
Interpretation
Together, these findings indicate that although internal tibial rotation contributes to increased anterior cruciate ligament strain, it is secondary to knee abduction and anterior tibial translation in its effect on anterior cruciate ligament strain and potential risk of injury.
doi:10.1016/j.clinbiomech.2013.10.017
PMCID: PMC3894911  PMID: 24238957
Anterior cruciate ligament; Biomechanics; Cadaveric experiments; Landing; Injury
5.  Effect of alignment changes on socket reaction moments while walking in transtibial prostheses with energy storage and return feet 
Background
Energy storage and return feet are designed for active amputees. However, little is known about the socket reaction moments in transtibial prostheses with energy storage and return feet. The aim of this study was to investigate the effect of alignment changes on the socket reaction moments during gait while using the energy storage and return feet.
Methods
A Smart Pyramid™ was used to measure the socket reaction moments in 10 subjects with transtibial prostheses while walking under 25 alignment conditions, including a nominal alignment (as defined by conventional clinical methods), as well as angle malalignments of 2°, 4° and 6° (flexion, extension, abduction, and adduction) and translation malalignments of 5mm, 10mm and 15mm (anterior, posterior, lateral, and medial) referenced from the nominal alignment. The socket reaction moments of the nominal alignment were compared with each malalignment.
Findings
Both coronal and sagittal alignment changes demonstrated systematic effects on the socket reaction moments. In the sagittal plane, angle and translation alignment changes demonstrated significant differences (P<0.05) in the minimum moment, the moment at 45% of stance and the maximum moment for some comparisons. In the coronal plane, angle and translation alignment changes demonstrated significant differences (P<0.05) in the moment at 30% and 75% of stance for all comparisons.
Interpretation
The alignment may have systematic effects on the socket reaction moments in transtibial prostheses with energy storage and return feet. The socket reaction moments could potentially be a useful biomechanical parameter to evaluate the alignment of the transtibial prostheses.
doi:10.1016/j.clinbiomech.2013.11.005
PMCID: PMC3951460  PMID: 24315709
amputation; direct measurement; load; malalignment; kinetics
6.  VARIABILITY OF PEAK SHOULDER FORCE DURING WHEELCHAIR PROPULSION IN MANUAL WHEELCHAIR USERS WITH AND WITHOUT SHOULDER PAIN 
Clinical biomechanics (Bristol, Avon)  2013;28(0):10.1016/j.clinbiomech.2013.10.004.
Background
Manual wheelchair users report a high prevalence of shoulder pain. Growing evidence shows that variability in forces applied to biological tissue is related to musculoskeletal pain. The purpose of this study was to examine the variability of forces acting on the shoulder during wheelchair propulsion as a function of shoulder pain.
Methods
Twenty-four manual wheelchair users (13 with pain, 11 without pain) participated in the investigation. Kinetic and kinematic data of wheelchair propulsion were recorded for three minutes maintaining a constant speed at three distinct propulsion speeds (fast speed of 1.1 m/s, a self-selected speed, and a slow speed of 0.7 m/s). Peak resultant shoulder forces in the push phase were calculated using inverse dynamics. Within individual variability was quantified as the coefficient of variation of cycle to cycle peak resultant forces.
Findings
There was no difference in mean peak shoulder resultant force between groups. The pain group had significantly smaller variability of peak resultant force than the no pain group (p < 0.01, η2 = 0.18).
Interpretation
The observations raise the possibility that propulsion variability could be a novel marker of upper limb pain in manual wheelchair users.
doi:10.1016/j.clinbiomech.2013.10.004
PMCID: PMC3858527  PMID: 24210512
Movement variability; Shoulder; Joint kinetics; Pain; Inverse dynamics
7.  Intrinsic Foot Muscle Deterioration is Associated with Metatarsophalangeal Joint Angle in People with Diabetes and Neuropathy 
Background
Metatarsophalangeal joint deformity is associated with skin breakdown and amputation. The aims of this study were to compare intrinsic foot muscle deterioration ratios (ratio of adipose to muscle volume), and physical performance in subjects with diabetic neuropathy to controls, and determine their associations with 1) metatarsophalangeal joint angle and 2) history of foot ulcer.
Methods
23 diabetic, neuropathic subjects [59 (SD 10) years] and 12 age-matched controls [57 (SD 14) years] were studied. Radiographs and MRI were used to measure metatarsophalangeal joint angle and intrinsic foot muscle deterioration through tissue segmentation by image signal intensity. The Foot and Ankle Ability Measure evaluated physical performance.
Findings
The diabetic, neuropathic group had a higher muscle deterioration ratio [1.6 (SD 1.2) vs. 0.3 (SD 0.2), P < 0.001], and lower Foot and Ankle Ability Measure scores [65.1 (SD 24.4) vs. 98.3 (SD 3.3) %, P < 0.01]. The correlation between muscle deterioration ratio and metatarsophalangeal joint angle was r = −0.51 (P = 0.01) for all diabetic, neuropathic subjects, but increased to r = −0.81 (P < 0.01) when only subjects with muscle deterioration ratios >1.0 were included. Muscle deterioration ratios in individuals with diabetic neuropathy were higher for those with a history of ulcers.
Interpretation
Individuals with diabetic neuropathy had increased intrinsic foot muscle deterioration, which was associated with second metatarsophalangeal joint angle and history of ulceration. Additional research is required to understand how foot muscle deterioration interacts with other impairments leading to forefoot deformity and skin breakdown.
doi:10.1016/j.clinbiomech.2013.10.006
PMCID: PMC3893062  PMID: 24176198
Intermuscular adipose tissue; muscle; foot deformity
8.  Timing differences in the generation of ground reaction forces between the initial and secondary landing phases of the drop vertical jump ☆ 
Background
Rapid impulse loads imparted on the lower extremity from ground contact when landing from a jump may contribute to ACL injury prevalence in female athletes. The drop jump and drop landing tasks enacted in the first and second landings of drop vertical jumps, respectively, have been shown to elicit separate neuromechanical responses. We examined the first and second landings of a drop vertical jump for differences in landing phase duration, time to peak force, and rate of force development.
Methods
239 adolescent female basketball players completed drop vertical jumps from an initial height of 31 cm. In-ground force platforms and a three dimensional motion capture system recorded force and positional data for each trial.
Findings
Between the first and second landing, rate of force development experienced no change (P > 0.62), landing phase duration decreased (P = 0.01), and time to peak ground reaction force increased (P < 0.01). Side-by-side asymmetry in rate of force development was not present in either landing (P > 0.12).
Interpretation
The current results have important implications for the future assessment of ACL injury risk behaviors. Rate of force development remained unchanged between first and second landings from equivalent fall height, while time to peak reaction force increased during the second landing. Neither factor was dependent on the total time duration of landing phase, which decreased during the second landing. Shorter time to peak force may increase ligament strain and better represent the abrupt joint loading that is associated with ACL injury risk.
doi:10.1016/j.clinbiomech.2013.07.004
PMCID: PMC4166408  PMID: 23899938
Drop jump; ACL; Drop land; Ground reaction force; Rate of force development
9.  Instantaneous Helical Axis Methodology to Identify Aberrant Neck Motion 
Background
Neck pain afflicts 30-50% of the U.S. population annually; however we currently have poor diagnostic differentiation techniques to inform individualized treatment. Planar neck kinematics has been shown to be correlated with neck pain, but neck motion is much more complex than pure planar activities. Our objective was to define a methodology for determining aberrant neck kinematics and assess it.
Methods
We examined a complex neck kinematic activity of neck circumduction, computed the pathway of motion using the instantaneous helical axis approach in 81 patients with non-specific neck pain and in 20 non-matched symptom free subjects. Neck circumduction, or rolling of the head, represents a complex neck kinematic activity, investigating the innate coupled motion of the cervical spine at the end ranges of motion in all directions. Instance of discontinuities in the helical axis patterns, or folds, were identified and labeled as occurrences of aberrant motion.
Findings
The instances of aberrant motion, or folds, which are nearly non-existent in the healthy sample group, are present in both the pre and post treatment neck pain patients. Following a treatment intervention of the symptomatic patients, pain and neck disability index decreased significantly (p<0.001) concomitant with a decrease in the number of folds (p=0.021).
Interpretation
The present study highlights a new technique using an instantaneous helical axis approach to detect subtle abnormalities in the pathway of motion of the head about the trunk, during a neck circumduction exercise.
doi:10.1016/j.clinbiomech.2013.07.006
PMCID: PMC3771663  PMID: 23911108
neck pain; helical axis; aberrant motion; kinematics; cervical spine
10.  Diurnal variation of gait in patients with rheumatoid arthritis: The DIVIGN study☆ 
Background
Circadian variation of joint stiffness (morning stiffness) and its impact on functional ability are widely recognised in rheumatoid arthritis. Subsequent within-day variation of walking ability is important due to the increased availability of instrumented gait analysis. This study aimed to quantify diurnal variation of gait in patients with rheumatoid arthritis, and explore associations with disease characteristics.
Methods
Thirty one inpatients with rheumatoid arthritis walked at a self-selected speed along a GAITRite instrumented walkway 5 times during a single day.
Findings
Participants showed marked diurnal variation in gait, leading to a systematic variation throughout the day (F = 19.56, P = < 0.001). Gait velocity and stride length both increased, whereas the proportion of each gait cycle spent in stance phase or double support decreased, consistent with improving function throughout the day. Although absolute gait velocity correlated with disease characteristics, the magnitude of diurnal variation appeared to be independent of disease activity (rho = 0.26, P = 0.15), disease duration (rho = − 0.19, P = 0.324), and underlying functional ability (rho = 0.09, P = 0.65).
Interpretation
Although morning stiffness is well recognised in rheumatoid arthritis, this is the first time that its effect on gait has been quantified. Patients with rheumatoid arthritis exhibited a systematic change in walking ability throughout the day, which was independent of disease characteristics. These findings have important implications for the interpretation of existing data and the design of future studies. Repeat measures should be conducted at the same time of day to exclude the effects of diurnal variation.
Highlights
•Patients with rheumatoid arthritis exhibited a systematic change in walking ability throughout the day.•The magnitude of within day change appeared independent of disease characteristics.•In future, repeat measures should be conducted at the same time of day to exclude the effects of diurnal variation.
doi:10.1016/j.clinbiomech.2014.05.009
PMCID: PMC4166456  PMID: 24954102
Rheumatoid arthritis; Gait analysis; Diurnal variation
11.  Load response of the medial longitudinal arch in patients with flatfoot deformity: in vivo 3D study 
Background
The acquisition of flatfoot by an adult is thought to primarily be caused by posterior tibial tendon dysfunction, although some other causes, such as congenital flexible flatfoot or an accessory navicular, may also be responsible. The objective of this study was to evaluate the bone rotation of each joint in the medial longitudinal arch (MLA) and compare the response in healthy feet with that in flat feet by analyzing the reconstructive three-dimensional (3D) CT image data during weightbearing.
Methods
CT scans of 20 healthy feet and 24 feet with flatfoot deformity were taken in non-load condition followed by full-body weightbearing condition. Images of the tibia and MLA bones (first metatarsal bone, cuneiforms, navicular, talus, and calcaneus) were reconstructed into 3D models. The volume merge method in three planes was used to calculate the bone-to-bone relative rotations.
Findings
Under loading conditions, the flatfoot dorsiflexed more in the first tarsometatarsal joint, and everted more in the talonavicular and talocalcaneal joints compared with the healthy foot. The total relative rotation was larger in the flatfoot compared with the healthy foot only in the first tarsometatarsal joint.
Interpretation
Supporting the MLA in the sagittal direction and the subtalar joint in the coronal direction may be useful for treating flatfoot deformity. The first tarsometatarsal joint may play an important role in diagnosing or treating flatfoot deformity.
doi:10.1016/j.clinbiomech.2013.04.004
PMCID: PMC4098854  PMID: 23643289
Three-dimensional Image; Flatfoot; Medial Longitudinal Arch; Weightbearing
12.  Leg preference associated with protective stepping responses in older adults 
Background
Asymmetries in dynamic balance stability have been previously observed. The goal of this study was to determine whether leg preference influenced the stepping response to a waist-pull perturbation in older adult fallers and non-fallers.
Methods
39 healthy, community-dwelling, older adult (>65 years) volunteers participated. Participants were grouped into non-faller and faller cohorts based on fall history in the 12 months prior to the study. Participants received 60 lateral waist-pull perturbations of varying magnitude towards their preferred and non-preferred sides during quiet standing. Outcome measures included balance tolerance limit, number of recovery steps taken and type of recovery step taken for perturbations to each side.
Findings
No significant differences in balance tolerance limit (P ≥ 0.102) or number of recovery steps taken (η2partial ≤ 0.027; P ≥ 0.442) were observed between perturbations towards the preferred and non-preferred legs. However, non-faller participants more frequently responded with a medial step when pulled towards their non-preferred side and cross-over steps when pulled towards their preferred side (P = 0.015).
Interpretation
Leg preference may influence the protective stepping response to standing balance perturbations in older adults at risk for falls, particularly with the type of recovery responses used. Such asymmetries in balance stability recovery may represent a contributing factor for falls among older individuals and should be considered for rehabilitation interventions aimed at improving balance stability and reducing fall risk.
doi:10.1016/j.clinbiomech.2013.07.015
PMCID: PMC4083490  PMID: 23962655
Falls; Stepping response; Leg preference; Older adults
13.  The influence of merged muscle excitation modules on post-stroke hemiparetic walking performance 
Background
Post-stroke subjects with hemiparesis typically utilize a reduced number of modules or co-excited muscles compared to non-impaired controls, with at least one module resembling the merging of two or more non-impaired modules. In non-impaired walking, each module has distinct contributions to important biomechanical functions, and thus different merged module combinations post-stroke may result in different functional consequences.
Methods
Three-dimensional forward dynamics simulations were developed for non-impaired controls and two groups of post-stroke hemiparetic subjects with different merged module combinations to analyze how paretic leg muscle contributions to body support, forward propulsion, mediolateral control and leg swing are altered.
Findings
The potential of the plantarflexors to generate propulsion was impaired in both hemiparetic groups while the remaining functional consequences differed depending on which modules were merged. Paretic leg swing was impaired during pre-swing when Modules 1 (hip abductors and knee extensors during early stance) and 2 (plantarflexors during late stance) were merged and during late swing when Modules 1 and 4 (hamstrings during swing into early stance) were merged. When Modules 1 and 4 were merged, body support during early stance was also impaired.
Interpretation
These results suggest that improving plantarflexor ability to generate propulsion is critical during rehabilitation regardless of module composition. If Modules 1 and 2 are merged, then rehabilitation should also focus on improving paretic leg pre-swing whereas if Modules 1 and 4 are merged, then rehabilitation should also focus on improving early stance body support and late paretic leg swing.
doi:10.1016/j.clinbiomech.2013.06.003
PMCID: PMC3732538  PMID: 23830138
Forward dynamics simulation; muscle synergies; gait; biomechanics
14.  Kinetics and Kinematics after the Bridle Procedure for Treatment of Traumatic Foot Drop 
Background
The Bridle procedure restores active ankle dorsiflexion through a tri-tendon anastamosis of the tibialis posterior, transferred to the dorsum of the foot, with the peroneus longus and tibialis anterior tendon. Inter-segmental foot motion after the Bridle procedure has not been measured. The purpose of this study is to report kinetic and kinematic variables during walking and heel rise in patients after the Bridle procedure.
Methods
18 Bridle and 10 control participants were studied. Walking and heel rise kinetic and kinematic variables were collected and compared using an ANOVA.
Findings
During walking the Bridle group, compared with controls, had reduced ankle power at push off [2.3 (SD 0.7) W/kg, 3.4 (SD 0.6) W/kg, respectively, P<.01], less hallux extension during swing [−13 (SD 7)°, 15 (SD6)°, respectively, P<.01] and slightly less ankle dorsiflexion during swing [6 (SD4)°, 9 (SD 2)°, respectively, P=.03]. During heel rise the Bridle group had 4 (SD 6)° of forefoot on hindfoot dorsiflexion compared to 8 (SD 3)° of plantarflexion in the controls (P<.01).
Interpretation
This study provides evidence that the Bridle procedure restores the majority of dorsiflexion motion during swing. However, plantarflexor function during push off and hallux extension during swing were reduced during walking in the Bridle group. Abnormal mid-tarsal joint motion, forefoot on hindfoot dorsiflexion instead of plantarflexion, was identified in the Bridle group during the more challenging heel rise task. Intervention after the Bridle procedure must maximize ankle plantarflexor function and midfoot motion should be examined during challenging tasks.
doi:10.1016/j.clinbiomech.2013.04.008
PMCID: PMC3934630  PMID: 23684087
15.  Proximal and Distal Kinematics in Female Runners with Patellofemoral Pain 
Background
Female runners have a high incidence of developing patellofemoral pain. Abnormal mechanics are thought to be an important contributing factor to patellofemoral pain. However, the contribution of abnormal trunk, hip, and foot mechanics to the development of patellofemoral pain within this cohort remains elusive. Therefore the aim of this study was to determine if significant differences during running exist in hip, trunk and foot kinematics between females with and without patellofemoral pain.
Methods
32 female runners (16 patellofemoral pain, 16 healthy control) participated in this study. All individuals underwent an instrumented gait analysis. Between-group comparisons were made for hip adduction, hip internal rotation, contra-lateral pelvic drop, contra-lateral trunk lean, rearfoot eversion, tibial internal rotation, as well as forefoot dorsiflexion and abduction
Findings
The patellofemoral pain group had significantly greater peak hip adduction and hip internal rotation. No differences in contra-lateral pelvic drop were found. A trend towards reduced contra-lateral trunk lean was found in the patellofemoral pain group. No significant differences were found in any of the rearfoot or forefoot variables but significantly greater shank internal rotation was found in the patellofemoral pain group.
Interpretation
We found greater hip adduction, hip internal rotation and shank internal rotation in female runners with patellofemoral pain. We also found less contra-lateral trunk lean in the patellofemoral pain group. This may be a potential compensatory mechanism for the poor hip Control seen. Rehabilitation programs that correct abnormal hip and shank kinematics are warranted in this population.
doi:10.1016/j.clinbiomech.2011.10.005
PMCID: PMC3984468  PMID: 22071426
16.  Narrowing carpal arch width to increase cross-sectional area of carpal tunnel – a cadaveric study 
Background
Carpal tunnel morphology plays an essential role in the etiology and treatment of carpal tunnel syndrome. The purpose of this study was to observe the morphological changes of the carpal tunnel as a result of carpal arch width narrowing. It was hypothesized carpal arch width narrowing would result in increased height and area of the carpal arch.
Methods
The carpal arch width of eight cadaveric hands was narrowed by a custom apparatus and cross-sectional ultrasound images were acquired. The carpal arch height and area were quantified as the carpal arch width was narrowed. Correlation and regression analyses were performed for the carpal arch height and area with respect to the carpal arch width.
Findings
The carpal tunnel became more convex as the carpal arch width was narrowed. The initial carpal arch width, height, and area were 25.7 (SD 1.9) mm, 4.1 (SD 0.6) mm, and 68.5 (SD 14.0) mm2, respectively. The carpal arch height and area negatively correlated with the carpal arch width, with correlation coefficients of −0.974 (SD 0.018) and −0.925 (SD 0.034), respectively. Linear regression analyses showed a 1 mm narrowing of the carpal arch width resulted in proportional increases of 0.40 (SD 0.14) mm in the carpal arch height and 4.0 (SD 2.2) mm2 in the carpal arch area.
Interpretation
This study demonstrates that carpal arch width narrowing leads to increased carpal arch height and area, a potential mechanism to reduce the mechanical insult to the median nerve and relieve symptoms associated with carpal tunnel syndrome.
doi:10.1016/j.clinbiomech.2013.02.014
PMCID: PMC3669224  PMID: 23583095
Carpal arch; carpal tunnel; width; height; area
17.  Kinetic and kinematic differences between first and second landings of a drop vertical jump task: Implications for injury risk assessments✩ 
Clinical biomechanics (Bristol, Avon)  2013;28(4):10.1016/j.clinbiomech.2013.02.013.
Background
Though the first landing of drop vertical jump task is commonly used to assess biomechanical performance measures that are associated with anterior cruciate ligament injury risk in athletes, the implications of the second landing in this task have largely been ignored. We examined the first and second landings of a drop vertical jump for differences in kinetic and kinematic behaviors at the hip and knee.
Methods
Acohort of 239 adolescent female basketball athletes (age = 13.6 (1.6) years) completed drop vertical jump tasks from an initial height of 31 cm. A three dimensional motion capture system recorded positional data while dual force platforms recorded ground reaction forces for each trial.
Findings
The first landing demonstrated greater hip adduction angle, knee abduction angle, and knee abduction moment than the second landing (P-values < 0.028). The second landing demonstrated smaller flexion angles and moments at the hip and knee than the first landing (P-values < 0.035). The second landing also demonstrated greater side-to-side asymmetry in hip and knee kinematics and kinetics for both the frontal and sagittal planes (P-values < 0.044).
Interpretation
The results have important implications for the future use of the drop vertical jump as an assessment tool for anterior cruciate ligament injury risk behaviors in adolescent female athletes. The second landing may be a more rigorous task and provides a superior tool to evaluate sagittal plane risk factors than the first landing, which may be better suited to evaluate frontal plane risk factors.
doi:10.1016/j.clinbiomech.2013.02.013
PMCID: PMC3809751  PMID: 23562293
Kinematics; Kinetics; Drop vertical jump; ACL injury risk; Knee biomechanics
18.  Hip and knee joint loading during vertical jumping and push jerking 
Background
The internal joint contact forces experienced at the lower limb have been frequently studied in activities of daily living and rehabilitation activities. In contrast, the forces experienced during more dynamic activities are not well understood, and those studies that do exist suggest very high degrees of joint loading.
Methods
In this study a biomechanical model of the right lower limb was used to calculate the internal joint forces experienced by the lower limb during vertical jumping, landing and push jerking (an explosive exercise derived from the sport of Olympic weightlifting), with a particular emphasis on the forces experienced by the knee.
Findings
The knee experienced mean peak loadings of 2.4-4.6 × body weight at the patellofemoral joint, 6.9-9.0 × body weight at the tibiofemoral joint, 0.3-1.4 × body weight anterior tibial shear and 1.0-3.1 × body weight posterior tibial shear. The hip experienced a mean peak loading of 5.5-8.4 × body weight and the ankle 8.9-10.0 × body weight.
Interpretation
The magnitudes of the total (resultant) joint contact forces at the patellofemoral joint, tibiofemoral joint and hip are greater than those reported in activities of daily living and less dynamic rehabilitation exercises. The information in this study is of importance for medical professionals, coaches and biomedical researchers in improving the understanding of acute and chronic injuries, understanding the performance of prosthetic implants and materials, evaluating the appropriateness of jumping and weightlifting for patient populations and informing the training programmes of healthy populations.
doi:10.1016/j.clinbiomech.2012.10.006
PMCID: PMC3966561  PMID: 23146164
musculoskeletal modelling; inverse dynamics; joint contact forces; vertical jumping; weightlifting
19.  Factors contributing to lumbar region passive tissue characteristics in people with and people without low back pain 
Background
Previously, we demonstrated that people in the Rotation with Extension low back pain subgroup display greater asymmetry of passive tissue characteristics during trunk lateral bending than people without low back pain. The purpose of this secondary analysis is to examine factors that explain the group differences.
Methods
Twenty-two people in the Rotation with Extension subgroup, and 19 people without low back pain were examined. Torque, lumbar region kinematics, and trunk muscle activity were measured during passive and isometric resisted trunk lateral bending. The dependent variables were lumbar region passive elastic energy to each side; the independent variables included group, gender, anthropometrics, trunk muscle characteristics, and an interaction factor of group and trunk muscle characteristics. Multiple linear regression was used for the analysis.
Findings
Anthropometrics explained passive measures to the left (P=.03). Anthropometrics (P<.01), trunk muscle characteristics (P<.01), and the interaction of group and trunk muscle characteristics (P=.01) explained passive measures to the right. After accounting for gender and anthropometrics, 43.7% of the variance in passive measures to the right was uniquely accounted for by trunk muscle characteristics for the Rotation with Extension subgroup, compared to 0.5% for the group without low back pain.
Interpretation
Anthropometrics explained passive measures with trunk lateral bending to both sides, in both groups. For people in the Rotation with Extension subgroup, there was a direct relationship between trunk muscle performance and passive measures to the right. Muscle is an important contributing factor to asymmetry in this subgroup and should be considered in treatment.
doi:10.1016/j.clinbiomech.2013.01.005
PMCID: PMC3677531  PMID: 23402957
Low back; Stiffness; Muscle
20.  Dynamic Joint Stiffness and Co-contraction in Subjects after Total Knee Arthroplasty 
Background
Although total knee arthroplasty reduces pain and improves function, patients continue to walk with asymmetrical movement patterns, that may affect muscle activation and joint loading patterns. The purpose of this study was to evaluate the specific biomechanical abnormalities that persist after total knee arthroplasty and examine the neuromuscular mechanisms that may contribute to these asymmetries.
Methods
Dynamic joint stiffness at the hip, knee and ankle, as well as co-contraction at the knee and ankle, were compared between the operated and non-operated limbs of 32 subjects who underwent total knee arthroplasty and 21 subjects without lower extremity impairment. Dynamic joint stiffness was calculated as the slope of the line of joint moment plotted as a function of joint angle.
Findings
Subjects after total knee arthroplasty demonstrated higher dynamic joint stiffness in the operated knee compared to the non-operated knee (0.056 (0.023) Nm/kg/m/deg vs. 0.043 (0.016) Nm/kg/m/deg, P=0.003) and the knees from a control group without lower extremity pathology (controls: 0.042(0.015) Nm/kg/m/deg, P =0.017). No differences were found between limbs or groups for dynamic joint stiffness at the hip or ankle. There was no relationship between dynamic joint stiffness at the knee and ankle and the amount of co-contraction between antagonistic muscles at those joints.
Interpretation
Patients after total knee arthroplasty walk with less knee joint excursion and greater knee stiffness, although no differences were found between groups for stiffness at the hip or ankle. Mechanisms other than co-contraction are likely the underlying cause of the altered knee mechanics. These findings are clinically relevant because the goal should be to create interventions to reduce these abnormalities and increase function.
doi:10.1016/j.clinbiomech.2012.11.008
PMCID: PMC3604158  PMID: 23219062
Total Knee Arthroplasty; Knee Osteoarthritis; Dynamic Joint Stiffness; Co-contraction; Knee Biomechanics
21.  Changes in the Flexor Digitorum Profundus Tendon Geometry in the Carpal Tunnel Due to Force Production and Posture of Metacarpophalangeal Joint of the Index Finger: an MRI Study 
Background
Carpal tunnel syndrome is a disorder caused by increased pressure in the carpal tunnel associated with repetitive, stereotypical finger actions. Little is known about in vivo geometrical changes in the carpal tunnel caused by motion at the finger joints and exerting a fingertip force.
Methods
The hands and forearms of five 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 posture subjects either produced no active force (passive condition) or exerted a flexion force to resist a load (~4.0 N) at the fingertip (active condition). Changes in the radii of curvature, position and transverse plane area of the flexor digitorum profundus tendons at the carpal tunnel level were measured.
Results
The radius of curvature of the flexor digitorum profundus tendons, at the carpal tunnel level, was significantly affected by posture of the index finger metacarpophalangeal joint (p<0.05) and the radii was significantly different between fingers (p<0.05). Actively producing force caused a significant shift (p<0.05) in the flexor digitorum profundus tendons in the ventral (palmar) direction. No significant change in the area of an ellipse containing the flexor digitorum profundus tendons was observed between conditions.
Interpretation
The results show that relatively small changes in the posture and force production of a single finger can lead to significant changes in the geometry of all the flexor digitorum profundus tendons in the carpal tunnel. Additionally, voluntary force production at the fingertip increases the moment arm of the FDP tendons about the wrist joint.
doi:10.1016/j.clinbiomech.2012.11.004
PMCID: PMC3609902  PMID: 23219762
MRI; carpal tunnel syndrome; moment arm; flexor digitorum profundus
22.  Temporal structure of variability decreases in upper extremity movements post stroke 
Background
The objective of this study was to determine movement variability in the more-affected upper-extremity in chronic stroke survivors. We investigated two hypotheses: (1) individuals with stroke will have increased amount of variability and altered structure of variability in upper-extremity joint movement patterns as compared to age-matched controls; and (2) the degree of motor impairment and joint kinematics will be correlated with the temporal structure of variability.
Methods
Sixteen participants with chronic stroke and nine age-matched controls performed three trials of functional reach-to-grasp. The amount of variability was quantified by computing the standard deviation of shoulder, elbow, wrist and index finger flexion/extension joint angles. The temporal structure of variability was determined by calculating approximate entropy in shoulder, elbow, wrist and index finger flexion/extension joint angles.
Findings
Individuals with stroke demonstrated greater standard deviations and significantly reduced approximate entropy values as compared to controls. Furthermore, motor impairments and kinematics demonstrated moderate to strong correlations with temporal structure of variability.
Interpretation
Changes in the temporal structure of variability in upper-extremity joint angles suggest that movement patterns used by stroke survivors are less adaptable. This knowledge may yield additional insights into the impaired motor system and suggest better interventions that can enhance upper-extremity movement adaptability.
doi:10.1016/j.clinbiomech.2012.11.006
PMCID: PMC3615058  PMID: 23337766
Time-dependent structure; Motor skills; Complexity; Kinematics; Upper extremity
23.  Activity progression for anterior cruciate ligament injured individuals☆ 
Background
Functional exercises are important in the rehabilitation of anterior cruciate ligament deficient and reconstructed individuals but movement compensations and incomplete recovery persist. This study aimed to identify how tasks pose different challenges; and evaluate if different activities challenge patient groups differently compared to controls.
Methods
Motion and force data were collected during distance hop, squatting and gait for 20 anterior cruciate ligament deficient, 21 reconstructed and 21 controls.
Findings
Knee range of motion was greatest during squatting, intermediate during hopping and smallest during gait (P < 0.01). Peak internal knee extensor moments were greatest during distance hop (P < 0.01). The mean value of peak knee moments was reduced in squatting and gait (P < 0.01) compared to hop. Peak internal extensor moments were significantly larger during squatting than gait and peak external adductor moments during gait compared to squatting (P < 0.01). Fluency was highest during squatting (P < 0.01). All patients demonstrated good recovery of gait but anterior cruciate ligament deficient adopted a strategy of increased fluency (P < 0.01). During squatting knee range of motion and peak internal knee extensor moment were reduced in all patients (P < 0.01). Both anterior cruciate ligament groups hopped a shorter distance (P < 0.01) and had reduced knee range of motion (P < 0.025). Anterior cruciate ligament reconstructed had reduced fluency (P < 0.01).
Interpretation
Distance hop was most challenging; squatting and gait were of similar difficulty but challenged patients in different ways. Despite squatting being an early, less challenging exercise, numerous compensation strategies were identified, indicating that this may be more challenging than gait.
doi:10.1016/j.clinbiomech.2013.11.010
PMCID: PMC3969717  PMID: 24447417
Clinical biomechanics; Movement analysis; Anterior cruciate ligament; Rehabilitation; Knee joint; Functional exercise; Physiotherapy
24.  Longitudinal Changes in Lumbar Bone Mineral Density Distribution May Increase the Risk of Wedge Fractures 
Background
Trabecular bone strength diminishes as a result of osteoporosis and altered biomechanical loading at the vertebral and spine level. The spine consists of the anterior, middle and posterior columns and the load supported by the anterior and middle columns will differ across different regions of the spine. Stress shielding of the anterior column can contribute to bone loss and increase the risk of wedge fracture. There is a lack of quantitative data related to regional spinal bone mineral density distribution over time. We hypothesize that there is an increase in the posterior-to-anterior vertebral body bone mineral density ratio and a decrease in whole-body bone mineral density over time.
Methods
Bone mineral density was measured in 33 subjects using quantitative computed tomography scans for L1–L3 vertebrae, region (anterior and posterior vertebral body), and time (baseline and 6 years after).
Findings
Lumbar bone mineral density decreased significantly (Δ: ~15%) from baseline to the 6th year visit. Individual vertebrae differences over time (L1: ~14%, L2: ~14%, L3:~17%) showed statistical significance. Anterior bone mineral density change was significantly greater than in the posterior vertebral body region (Δ anterior: ~18%; Δ posterior: ~13%). Posterior-to-anterior bone mineral density ratio was significantly greater in the 6th year compared to baseline values (mean (SD), 1.33 (0.2) vs. 1.23 (0.1)).
Interpretation
This study provides longitudinal quantitative measurement of bone mineral density in vertebrae as well as regional changes in the anterior and posterior regions. Understanding bone mineral density distribution over time may help to decrease the risk of wedge fractures if interventions can be developed to bring spine loading to its normal state.
doi:10.1016/j.clinbiomech.2012.10.005
PMCID: PMC3551990  PMID: 23142501
Lumbar; Bone Mineral Density; Time; Risk of Fracture; Vertebrae
25.  Interlimb coordination is impaired during walking in persons with Parkinson’s disease 
Background
Coordination between the upper and lower extremities is important to providing dynamic stability during human gait. Though limited, previous research has suggested that interlimb coordination may be impaired in persons with Parkinson’s disease. We extend this previous work using continuous analytical techniques to enhance our understanding of interlimb coordination during gait in persons with Parkinson’s disease.
Methods
Eighteen adults with Parkinson’s disease and fifteen healthy older adults walked overground while undergoing three-dimensional motion capture. Ipsilateral and contralateral interlimb coordination between the sagittal shoulder and hip angles was assessed using cross-covariance techniques. Independent samples and paired samples t-tests compared measures of interlimb coordination between groups and between sides within the participants with Parkinson’s disease, respectively. Pearson’s correlations were applied to investigate associations between interlimb coordination measures and subscores of gait, posture, and bradykinesia on the Unified Parkinson’s Disease Rating Scale.
Findings
Ipsilateral and contralateral interlimb coordination was reduced in persons with Parkinson’s disease compared to the healthy older adults. Ipsilateral coordination between the upper and lower extremities more affected by disease was found to be negatively associated with clinical scores of gait and posture. Interlimb coordination was not significantly associated with clinical measures of bradykinesia.
Interpretation
Persons with Parkinson’s disease exhibit reduced interlimb coordination during gait when compared to healthy older adults. These reductions in coordination are related to clinically-meaningful worsening of gait and posture in persons with PD and coordination of arm and leg movements should be considered in future research on gait therapy in this population.
doi:10.1016/j.clinbiomech.2012.09.005
PMCID: PMC3552037  PMID: 23062816
Parkinson’s disease; gait; interlimb coordination; cross-covariance

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