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Individuals with cerebral palsy tend to have altered muscle architecture and composition, but little is known about the muscle material properties, specifically stiffness. Shear wave ultrasound elastography allows shear wave speed, which is related to stiffness, to be measured in vivo in individual muscles. Our aim was to evaluate the material properties, specifically stiffness, as measured by shear wave speed of the medial gastrocnemius and tibialis anterior muscles in children with hemiplegic cerebral palsy across a range of ankle torques and positions, and fascicle strains.
Shear wave speed was measured bilaterally in the medial gastrocnemius and tibialis anterior over a range of ankle positions and torques using shear wave ultrasound elastography in eight individuals with hemiplegic cerebral palsy. B-mode ultrasound was used to measure muscle thickness and fascicle strain.
Shear waves traveled faster in the medial gastrocnemius and tibialis anterior of the more-affected limb by 14% (p=0.024) and 20% (p=0.03), respectively, when the ankle was at 90°. Shear wave speed in the medial gastrocnemius increased as the ankle moved from plantarflexion to dorsiflexion (less affected: r2=0.82,p<0.001; more-affected: r2=0.69,p<0.001) and as ankle torque increased (less affected: r2=0.56,p<0.001; more-affected: r2=0.45,p<0.001). In addition, shear wave speed was strongly correlated with fascicle strain (less affected: r2=0.63,p<0.001; more-affected: r2=0.53,p<0.001).
The higher shear wave speed in the more-affected limb of individuals with cerebral palsy indicates greater muscle stiffness, and demonstrates the clinical potential of shear wave elastography as a non-invasive tool for investigating mechanisms of altered muscle properties and informing diagnosis and treatment.
PMCID: PMC4729598  PMID: 26490641
cerebral palsy; muscle; ultrasound; shear wave elastography
2.  Identification of preferred landing leg in athletes previously injured and uninjured: A brief report 
Preferred or dominant limb is often subjectively defined by self-report. The purpose was to objectively classify preferred landing leg during landing in athletes previously injured and uninjured.
Subjects with history of anterior cruciate ligament reconstruction (n=101) and uninjured controls (n=57) participated. Three trials of a drop vertical jump were collected. Leg dominance was defined as the leg used to kick a ball while landing leg preference was calculated as the leg which landed first during landing trials. Limb symmetry index was also calculated during a single leg hop battery. The distribution of subjects that landed first on their uninvolved or dominant leg, respectively, was statistically compared. Limb symmetry from the single leg hop tests were compared within each subgroup.
The distribution of preferred landing leg to uninvolved limb for injured (71%) and dominant limb for controls (63%) was not statistically different between groups (p=0.29). Limb symmetry was decreased in injured subjects that preferred to land on their uninvolved limb compared to their involved limb during single leg (p<0.001), triple (p<0.001), cross-over (p<0.001), and timed hops (p=0.007). Differences in limb symmetry were not statistically different in controls (p>0.05).
The leg that first contacts the ground during landing may be a useful strategy to classify preferred landing leg. 29% of injured subjects preferred to land on their involved leg which may relate to improved confidence and readiness to return to sport as improved limb symmetry were present during hop tests.
PMCID: PMC4729638  PMID: 26490640
Preferred landing leg; dominant limb; landing biomechanics; limb asymmetries; anterior cruciate ligament reconstruction; drop vertical jump
3.  A comparative study of A1 pulley compliance 
Trigger finger is most common in the ring finger, but the reason for this is not known. We hypothesized that the compliance of the A1 pulley might be one of the factors responsible for this phenomenon. The purpose of this study was therefore to compare the compliance of the normal A1 pulley of the thumb, index, middle, ring and little fingers using human cadavers.
Eight normal thumbs, index, middle, ring and little fingers from eight fresh frozen human hand cadavers were used in this experiment. The compliance of the A1 pulley was measured by the resistance when passing a tapered metal rod through the A1 pulley. The slopes of the linear region of radial force/increasing area ratio curve were calculated and analyzed.
The mean slope of the linear region of the radial force/increasing area ratio curve was significantly different among the five digits (p<0.05). Post hoc analysis indicated that the mean slope for the middle finger A1 pulleys was larger than the thumb and little finger A1 pulleys (p<0.05).
The findings did not support our clinical hypothesis that A1 pulley stiffness would parallel the relative frequency of trigger finger by digit.
PMCID: PMC5156867  PMID: 20363060
Trigger digits; Tenosynovitis; Pulley; Hand; Human; Biomechanics
4.  Step activity and stride-to-stride fluctuations are negatively correlated in individuals with transtibial amputation 
Clinical biomechanics (Bristol, Avon)  2015;30(10):1225-1229.
Variability occurs naturally from stride to stride in healthy gait. It has been shown that individuals with lower limb loss have significantly increased stride-to-stride fluctuations during walking. This is considered indicative of movement disorganization and is associated with less healthy movement. Given that lower limb prosthesis users perform on average less physical activity than able bodied individuals, the purpose of this study was to determine whether increased fluctuations also correspond to a reduced level of activity in daily life.
Twenty-two transtibial amputees wore an activity monitor (Actigraph, Pensacola, FL, USA) for 3 weeks. Lower limb kinematics during treadmill walking were measured using a 12-camera motion capture system. The largest Lyapunov exponent (λ) was calculated bilaterally at the ankle, knee and hip to quantify the stride-to-stride fluctuations of the lower limb joints. Pearson correlations were used to identify the relationships between the average daily step count over the 3 week collection period and λ.
Significant, moderate negative correlations between daily step count and λ were found at the intact ankle (r = 0.57, P = 0.005), and the knee on the affected side (r = 0.44, P = 0.038). No such correlation was found at any other lower limb joint.
The negative correlation evident at these two joints demonstrates that increased stride-to-stride fluctuations are related to decreased activity levels, however it remains unclear whether these changes in the stride-to-stride fluctuations promote decreased activity or whether less active individuals do not gain sufficient motor learning experience to achieve a skilled movement.
PMCID: PMC4767157  PMID: 26319219
Biomechanics; Human movement variability; Amputee; Rehabilitation; Lyapunov exponent
Clinical biomechanics (Bristol, Avon)  2015;30(10):1108-1113.
Falls can cause moderate to severe injuries such as hip fractures and head trauma in older adults. While declines in muscle strength and sensory function contribute to increased falls in older adults, skeletal muscle fatigue is often overlooked as an additional contributor to fall risk. The purpose of this investigation was to examine the effects of acute lower extremity muscle fatigue and age on reactive postural control in healthy adults.
A sample of 16 individuals participated in this study (8 healthy older adults and 8 healthy young persons). Whole body kinematic and kinetic data were collected during anterior and posterior reproducible fall tests before (T0) and immediately after (T1) eccentric muscle fatiguing exercise, as well as after 15-minutes (T15) and 30-minutes (T30) of rest.
Lower extremity joint kinematics of the stepping limb during the support (landing) phase of the anterior fall were significantly altered by the presence of acute muscle fatigue. Step velocity was significantly decreased during the anterior falls. Statistically significant main effects of age were found for step length in both fall directions. Effect sizes for all outcomes were small. No statistically significant interaction effects were found.
Muscle fatigue has a measurable effect on lower extremity joint kinematics during simulated falls. These alterations appear to resolve within 15 minutes of recovery. The above deficits, coupled with a reduced step length, may help explain the increased fall risk in older adults.
PMCID: PMC4674343  PMID: 26351001
postural control; muscle fatigue; aging
6.  Prospectively Identified Deficits in Sagittal Plane Hip-Ankle Coordination in Female Athletes who Sustain a Second Anterior Cruciate Ligament Injury after Anterior Cruciate Ligament Reconstruction and Return to Sport 
Clinical biomechanics (Bristol, Avon)  2015;30(10):1094-1101.
Athletes who return to sport after anterior cruciate ligament reconstruction are at increased risk of future ACL injury. Altered coordination of lower extremity motion may increase this risk. The purpose of this study was to prospectively determine if altered lower extremity coordination patterns exist in athletes who go on to sustain a 2nd anterior cruciate ligament injury.
Sixty-one female athletes who were medically cleared to return to sport after anterior cruciate ligament reconstruction were included. Hip-ankle coordination was assessed prior to return to sport with a dynamic postural coordination task. Within 12 months, 14 patients sustained a 2nd ACL injury. Fourteen matched subjects were selected for comparative analysis. Cross-recurrence quantification analysis characterized hip-ankle coordination patterns. A group × target speed (slow vs. fast) × leg (involved vs. uninvolved) analysis of variance was used to identify coordination differences.
A main effect of group (p = 0.02) indicated that the single injury group exhibited more stable hip-ankle coordination [166.2 (18.9)] compared to the 2nd injury group [108.4 (10.1)]. A leg × group interaction was also observed (p = .04). The affected leg of the single injury group exhibited more stable coordination [M = 187.1 (23.3)] compared to the affected leg of the 2nd injury group [M = 110.13 (9.8)], p = 0.03.
Hip-ankle coordination was altered in female athletes who sustained a 2nd anterior cruciate ligament injury after return to sport. Failure to coordinate lower extremity movement in the absence of normal knee proprioception may place the knee at high-risk.
PMCID: PMC4674344  PMID: 26416200
ACL Reconstruction; Postural Coordination; Second Injury; ACL; injury; recurrent injury
7.  Anterior cruciate ligament reconstruction and cartilage contact forces – a 3D computational simulation 
Clinical biomechanics (Bristol, Avon)  2015;30(10):1175-1180.
Clinical outcome studies showed a high incidence of knee osteoarthritis after anterior cruciate ligament reconstruction. Abnormal joint kinematics and loading conditions were assumed as risking factors. However, little is known on cartilage contact forces after the surgery.
A validated computational model was used to simulate anatomic and transtibial single-bundle anterior cruciate ligament reconstructions. Two graft fixation angles (0° and 30°) were simulated for each reconstruction. Biomechanics of the knee was investigated in intact, anterior cruciate ligament deficient and reconstructed conditions when the knee was subjected to 134N anterior load and 400N quadriceps load at 0°, 30°, 60° and 90° of flexion. The tibial translation and rotation, graft forces, medial and lateral contact forces were calculated.
When the graft was fixed at 0°, the anatomic reconstruction resulted in slightly larger lateral contact force at 0° compared to the intact knee while the transtibial technique led to higher contact force at both 0° and 30° under the muscle load. When graft was fixed at 30°, the anatomic reconstruction overstrained the knee at 0° with larger contact forces, while the transtibial technique resulted in slightly larger contact forces at 30°.
This study suggests that neither the anatomic nor the transtibial reconstruction can consistently restore normal knee biomechanics at different flexion angles. The anatomic reconstruction may better restore anteroposterior stability and contact force with the graft fixed at 0°. The transtibial technique may better restore knee anteroposterior stability and articular contact force with the graft fixed at 30° of flexion.
PMCID: PMC4674370  PMID: 26320976
Anterior cruciate ligament reconstruction; Biomechanics; Computational model; Contact force
8.  Acetabular cartilage defects cause altered hip and knee joint coordination variability during gait 
Clinical biomechanics (Bristol, Avon)  2015;30(10):1202-1209.
Patients with acetabular cartilage defects reported increased pain and disability compared to those without acetabular cartilage defects. The specific effects of acetabular cartilage defects on lower extremity coordination patterns are unclear. The purpose of this study was to determine hip and knee joint coordination variability during gait in those with and without acetabular cartilage defects.
A combined approach, consisting of a semi-quantitative MRI-based quantification method and vector coding, was used to assess hip and knee joint coordination variability during gait in those with and without acetabular cartilage lesions.
The coordination variability of the hip flexion-extension/knee rotation, hip abduction-adduction/knee rotation and hip rotation/knee rotation joint couplings were reduced in the acetabular lesion group compared to the control group during loading response of the gait cycle. The lesion group demonstrated increased variability in the hip flexion-extension/knee rotation and hip abduction-adduction/knee rotation joint couplings, compared to the control group, during the terminal stance/pre-swing phase of gait.
Reduced variability during loading response in the lesion group may suggest reduced movement strategies and a possible compensation mechanism for lower extremity instability during this phase of the gait cycle. During terminal stance/pre-swing, a larger variability in the lesion group may suggest increased movement strategies and represent a compensation or pain avoidance mechanism caused by the load applied to the hip joint.
PMCID: PMC4674371  PMID: 26298706
Acetabular Cartilage Lesions; Vector Coding; Joint Coordination; Gait; Lower Extremity; MRI
9.  The Influence of Speed and Grade on Wheelchair Propulsion Hand Pattern 
The hand pattern used during manual wheelchair propulsion (i.e., full-cycle hand path) can provide insight into an individual's propulsion technique. However, previous analyses of hand patterns have been limited by their focus on a single propulsion condition and reliance on subjective qualitative characterization methods. The purpose of this study was to develop a set of objective quantitative parameters to characterize hand patterns and determine the influence of propulsion speed and grade of incline on the patterns preferred by manual wheelchair users.
Kinematic and kinetic data were collected from 170 experienced manual wheelchair users on an ergometer during three conditions: level propulsion at their self-selected speed, level propulsion at their fastest comfortable speed, and graded propulsion (8%) at their level self-selected speed. Hand patterns were quantified using a set of objective parameters and differences across conditions were identified.
Increased propulsion speed resulted in a shift away from under-rim hand patterns. Increased grade of incline resulted in the hand remaining near the handrim throughout the cycle.
Manual wheelchair users change their hand pattern based on task-specific constraints and goals. Further work is needed to investigate how differences between hand patterns influence upper extremity demand and potentially lead to the development of overuse injuries and pain.
PMCID: PMC4631660  PMID: 26228706
Propulsion pattern; propulsion technique; speed; incline; manual wheelchair
10.  Rotator Cuff Repair with a Tendon-Fibrocartilage-Bone Composite Bridging Patch 
To compare the mechanical performance of a rotator cuff repaired with a novel tendon-fibrocartilage-bone composite bridging patch vs the traditional Mason-Allen repair in an in vitro canine model.
Twenty shoulders and 10 bridging patches from patellar tendon were harvested. The patches were trimmed and sliced into 2 layers. An infraspinatus tendon tear was created in each shoulder. Modified Mason-Allen sutures were used to repair the infraspinatus tendon to the greater tuberosity, with or without the bridging patch (bridging patch group and controls, respectively). Shoulders were loaded to failure under displacement control at a rate of 0.5mm/sec.
The ultimate tensile load was significantly higher in the bridging patch group than control (mean [SD], 365.46 [36.45] vs 272.79 [48.88] N; P<.001). Stiffness at the greater tuberosity repair site and the patch-infraspinatus tendon repair site was significantly higher than the control repair site (93.96 [27.72] vs 42.62 [17.48] N/mm P<.001; 65.94 [24.51] vs 42.62 [17.48] N/mm P=.02, respectively).
The tendon-fibrocartilage-bone composite bridging patch achieved higher ultimate tensile load and stiffness at the patch–greater tuberosity repair site compared with traditional repair in a canine model. This composite tissue transforms the traditional tendon-to-bone healing interface (with dissimilar tissues) into a pair of bone-to-bone and tendon-to-tendon interfaces, which may improve healing quality and reduce retear rate.
PMCID: PMC4631669  PMID: 26190097
rotator cuff repair; bridging patch; tendon-to-bone healing
11.  The effect of changing plantarflexion resistive moment of an articulated ankle-foot orthosis on ankle and knee joint angles and moments while walking in patients post stroke 
The adjustment of plantarflexion resistive moment of an articulated ankle-foot orthosis is considered important in patients post stroke, but the evidence is still limited. Therefore, the aim of this study was to investigate the effect of changing the plantarflexion resistive moment of an articulated ankle-foot orthosis on ankle and knee joint angles and moments in patients post stroke.
Gait analysis was performed on 10 subjects post stroke under four different plantarflexion resistive moment conditions using a newly designed articulated ankle-foot orthosis. Data were recorded using a Bertec split-belt instrumented treadmill in a 3-dimensional motion analysis laboratory.
The ankle and knee sagittal joint angles and moments were significantly affected by the amount of plantarflexion resistive moment of the ankle-foot orthosis. Increasing the plantarflexion resistive moment of the ankle-foot orthosis induced significant decreases both in the peak ankle plantarflexion angle (P<0.01) and the peak knee extension angle (P<0.05). Also, the increase induced significant increases in the internal dorsiflexion moment of the ankle joint (P<0.01) and significantly decreased the internal flexion moment of the knee joint (P<0.01).
These results suggest an important link between the kinematic/kinetic parameters of the lower-limb joints and the plantarflexion resistive moment of an articulated ankle-foot orthosis. A future study should be performed to clarify their relationship further so that the practitioners may be able to use these parameters as objective data to determine an optimal plantarflexion resistive moment of an articulated ankle-foot orthosis for improved orthotic care in individual patients.
PMCID: PMC4568124  PMID: 26149007
AFO; gait disorders; orthotic devices; stiffness; kinetics; kinematics
12.  The Influence of Task Complexity on Knee Joint Kinetics Following ACL Reconstruction 
Previous research indicates that subjects with anterior cruciate ligament reconstruction exhibit abnormal knee joint movement patterns during functional activities like walking. While the sagittal plane mechanics have been studied extensively, less is known about the secondary planes, specifically with regard to more demanding tasks. This study explored the influence of task complexity on functional joint mechanics in the context of graft-specific surgeries.
In 25 participants (10 hamstring tendon graft, 6 patellar tendon graft, 9 matched controls), three-dimensional joint torques were calculated using a standard inverse dynamics approach during level walking and stair descent. The stair descent task was separated into two functionally different sub-tasks—step-to-floor and step-to-step. The differences in external knee moment profiles were compared between groups; paired differences between the reconstructed and non-reconstructed knees were also assessed.
The reconstructed knees, irrespective of graft type, typically exhibited significantly lower peak knee flexion moments compared to control knees during stair descent, with the differences more pronounced in the step-to-step task. Frontal plane adduction torque deficits were graft-specific and limited to the hamstring tendon knees during the step-to-step task. Internal rotation torque deficits were also primarily limited to the hamstring tendon graft group during stair descent. Collectively, these results suggest that task complexity was a primary driver of differences in joint mechanics between anterior cruciate ligament reconstructed individuals and controls, and such differences were more pronounced in individuals with hamstring tendon grafts.
The mechanical environment experienced in the cartilage during repetitive, cyclical tasks such as walking and other activities of daily living has been argued to contribute to the development of degenerative changes to the joint and ultimately osteoarthritis. Given the task-specific and graft-specific differences in joint mechanics detected in this study, care should be taken during the rehabilitation process to mitigate these changes.
PMCID: PMC4568131  PMID: 26101055
ACL Reconstruction; Knee; Joint Torques; Motion Analysis; Gait; Stair Descent
13.  Biomechanical evaluation of a novel suturing scheme for grafting load-bearing collagen scaffolds for rotator cuff repair 
Currently, there are no well-established suture protocols to attach fully load-bearing scaffolds which span tendon defects between bone and muscle for repair of critical sized tendon tears. Methods to attach load-bearing tissue repair scaffolds could enable functional repair of tendon injuries.
Sixteen rabbit shoulders were dissected (New Zealand white rabbits, 1 yr. old, female) to isolate the humeral-infraspinatus muscle complex. A unique suture technique was developed to allow for a 5 mm segmental defect in infraspinatus tendon to be replaced with a mechanically strong bioscaffold woven from pure collagen threads. The suturing pattern resulted in a fully load-bearing scaffold. The tensile stiffness and strength of scaffold repair was compared with intact infraspinatus and regular direct repair.
The failure load and displacement at failure of the scaffold repair group were 59.9 N (Standard Deviation, SD = 10.7) and 10.3 mm (SD = 2.9), respectively and matched those obtained by direct repair group which were 57.5 N (SD = 15.3) and 8.6 mm (SD = 1.5), (p > 0.05). Failure load, displacement at failure and stiffness of both of the repair groups were half of the intact infraspinatus shoulder group.
With the developed suture technique, scaffolds repair showed similar failure load, displacement at failure and stiffness to the direct repair. This novel suturing pattern and the mechanical robustness of the scaffold at time zero indicates that the proposed model is mechanically viable for future in vivo studies which has a higher potential to translate into clinical uses.
PMCID: PMC4523401  PMID: 26009492
segmental rotator cuff defect; scaffold; collagen suture technique; mechanical properties; strength; infraspinatus tendon
14.  An Approach for Determining Quantitative Measures for Bone Volume and Bone Mass in the Pediatric Spina Bifida Population 
The pediatric spina bifida population suffers from decreased mobility and recurrent fractures. This study aimed to develop a method for quantifying bone mass along the entire tibia in youth with spina bifida. This will provide information about all potential sites of bone deficiencies.
Computed tomography images of the tibia for 257 children (n=80 ambulatory spina bifida, n=10 non-ambulatory spina bifida, n=167 typically developing) were analyzed. Bone area was calculated at regular intervals along the entire tibia length and then weighted by calibrated pixel intensity for density weighted bone area. Integrals of density weighted bone area were used to quantify bone mass in the proximal and distal epiphyses and diaphysis. Group differences were evaluated using analysis of variance.
Non-ambulatory children suffer from decreased bone mass in the diaphysis and proximal and distal epiphyses compared to ambulatory and control children (P≤0.001). Ambulatory children with spina bifida showed statistically insignificant differences in bone mass in comparison to typically developing children at these sites (P>0.5).
This method provides insight into tibial bone mass distribution in the pediatric spina bifida population by incorporating information along the whole length of the bone, thereby providing more information than dual-energy x-ray absorptiometry and peripheral quantitative computed tomography. This method can be applied to any population to assess bone mass distribution across the length of any long bone.
PMCID: PMC4523422  PMID: 26002057
spina bifida; myelomeningocele; bone density; bone mass; image analysis
15.  Combination of Eccentric Exercise and Neuromuscular Electrical Stimulation to Improve Biomechanical Limb Symmetry After Anterior Cruciate Ligament Reconstruction 
We have previously reported that an eccentrically-based rehabilitation protocol post-ACLr induced greater quadriceps activation and strength than a neuromuscular electrical stimulation (NMES) intervention and was just as effective as a combined NMES and eccentric intervention. However, the effect an eccentrically-based intervention has on restoring normal knee mechanics during a single-legged landing task remains unknown.
Thirty-six individuals post-injury were placed into four treatment groups: NMES and eccentrics, eccentrics-only, NMES-only, standard of care, and Healthy controls participated. NMES and eccentrics received a combined NMES and eccentric protocol post-reconstruction (each treatment 2x per week for 6 wks), whereas groups NMES-only and eccentric-only received only the NMES or eccentric therapy, respectively. To evaluate knee mechanics limb symmetry, the area under the curve for knee flexion angle and extension moment was derived and then normalized to the contralateral limb. Quadriceps strength was evaluated using the quadriceps index.
Compared to Healthy, reduced sagittal plane knee limb symmetry was found for groups NMES-only, ECC-only and standard of care for knee extension moment (P<0.05). No difference was detected between Healthy and NMES and eccentrics (P>0.06). No difference between groups was detected for knee flexion angle limb symmetry (P>0.05). Greater knee flexion angles and moments over stance were related to quadriceps strength.
The NMES and eccentrics group was found to restore biomechanical limb symmetry that was most closely related to Healthy individuals following ACL reconstruction. Greater knee flexion angles and moments over stance were related to quadriceps strength.
PMCID: PMC4523427  PMID: 25953255
ACL; knee; rehabilitation; strength testing; biomechanics
16.  Measuring movement symmetry using tibial-mounted accelerometers for people recovering from total knee arthroplasty 
The purpose of this investigation was to examine movement symmetry changes over the first 26 weeks following unilateral total knee arthroplasty in community environments using skin-mounted tibial accelerometers. Comparisons to healthy participants of similar age were also made.
Patients (N = 24) with unilateral knee osteoarthritis (mean (SD), 65.2 (9.2) years) scheduled to undergo total knee arthroplasty and a control group (N = 19 healthy people; mean (SD), 61.3 (9.2) years) were recruited. The total knee arthroplasty group participated in a standardized course of physical rehabilitation. Tibial acceleration data were recorded during a Stair Climb Test and 6-Minute Walk Test. Tibial acceleration data were reduced to initial peak acceleration for each step. An inter-limb absolute symmetry index of tibial initial peak acceleration values was calculated.
The total knee arthroplasty group had greater between limb asymmetry for tibial initial peak acceleration and initial peak acceleration absolute symmetry index values five weeks after total knee arthroplasty, during the Stair Climb Test and the 6-Minute Walk Test.
Tibial accelerometry is a potential tool for measuring movement symmetry following unilateral total knee arthroplasty in clinical and community environments. Accelerometer-based symmetry outcomes follow patterns similar to published measures of limb loading recorded in laboratory settings.
PMCID: PMC4523451  PMID: 25979222
total knee arthroplasty; movement symmetry; accelerometer; community environment
17.  Gait Behaviors as an Objective Surgical Outcome in Low Back Disorders: A Systematic Review 
Objective motor performance measures, especially gait assessment, could improve assessment of surgical low back disorder procedures. However, no study has compared the relative effectiveness of gait parameters for assessing motor performance in low back disorder after surgery. The purpose of the current review was to determine the sensitive gait parameters that address physical improvements in each specific spinal disorder after surgical intervention.
Articles were searched with the following inclusion criteria: 1) population studied consisted of individuals with low back disorders requiring surgery; 2) low back disorder was measured objectively using gait assessment tests pre- and post-surgery. The quality of the selected studies was assessed using Delphi consensus, and meta-analysis was performed to compare pre- and post-surgical changes.
Thirteen articles met inclusion criteria, which, almost exclusively, addressed only two types of spinal disorders/interventions: 1) scoliosis/spinal fusion; and 2) stenosis/decompression. For patients with scoliosis, improvements in motion of hip and shoulder (effect size=0.32–1.58), energy expenditure (effect size=0.59–1.18), and activity symmetry of upper-body muscles during gait were present after spinal fusion. For patients with spinal stenosis, increases in gait speed, stride length, cadence, symmetry, smoothness of walking, and walking endurance (effect size=0.60–2.50), and decrease in gait variability (effect size=1.45) were observed after decompression surgery.
For patients with scoliosis, improvements can be better assessed by measuring upper-body motion and EMG rather than the lower extremities during gait. For patients with spinal stenosis, motor performance improvements can be captured by measuring walking spatio-temporal parameters, gait patterns, and walking endurance.
PMCID: PMC4714541  PMID: 25921552
Back pain; physical impairment; operation; functional disorder; outcome; evidence
18.  Knee motion variability in patients with knee osteoarthritis: the effect of self-reported instability 
Knee osteoarthritis has been previously associated with a stereotypical knee-stiffening gait pattern and reduced knee joint motion variability due to increased antagonist muscle co-contractions and smaller utilized arc of motion during gait. However, episodic self-reported instability may be a sign of excessive motion variability for a large subgroup of patients with knee osteoarthritis. The objective of this work was to evaluate the differences in knee joint motion variability during gait in patients with knee osteoarthritis with and without self-reported instability compared to a control group of older adults with asymptomatic knees.
Forty-three subjects, 8 with knee osteoarthritis but no reports of instability (stable), 11 with knee osteoarthritis and self-reported instability (unstable), and 24 without knee osteoarthritis or instability (control) underwent Dynamic Stereo X-ray analysis during a decline gait task on a treadmill. Knee motion variability was assessed using parametric phase plots during the loading response phase of decline gait.
The stable group demonstrated decreased sagittal-plane motion variability compared to the control group (p=0.04), while the unstable group demonstrated increased sagittal-plane motion variability compared to the control (p=0.003) and stable groups (p<0.001). The unstable group also demonstrated increased anterior-posterior joint contact point motion variability for the medial tibiofemoral compartment compared to the control (p=0.03) and stable groups (p=0.03).
The finding of decreased knee motion variability in patients with knee osteoarthritis without self-reported instability supports previous research. However, presence of self-reported instability is associated with increased knee motion variability in patients with knee osteoarthritis and warrants further investigation.
PMCID: PMC4428966  PMID: 25796536
Instability; Variability; Kinematics; Gait
Proximal row carpectomy and scaphoid-excision four-corner fusion are salvage procedures that relieve pain by removing arthritic joint surfaces. While numerous studies have examined how these procedures affect joint motion, few have examined how they influence muscle mechanical actions. This study examines whether muscle moment arms change after these procedures.
Moment arms of primary wrist muscles were measured in 8 cadaveric specimens using the tendon excursion method. In each specimen, moment arms were measured for two degrees of freedom (flexion-extension and radial-ulnar deviation) and three conditions (nonimpaired, scaphoid-excision four-corner fusion, and proximal row carpectomy). For each muscle and degree of freedom, moment arm versus joint angle curves for the three conditions were statistically compared.
Wrist salvage procedures significantly alter moment arms of the primary wrist muscles. Proximal row carpectomy primarily alters flexion-extension moment arms, while scaphoid-excision four-corner fusion primarily alters radial-ulnar deviation moment arms. Both procedures also alter the balance between agonist and antagonist wrist muscles. Following proximal row carpectomy, wrist extensors have smaller moment arms in extended postures. Following scaphoid-excision four-corner fusion, radial deviators have larger moment arms throughout radial-ulnar deviation.
Different moment arms indicate that different forces are required to complete the same tasks in nonimpaired and surgically altered wrists. The altered muscle moment arms likely contribute to post-operative impairments. Understanding how salvage procedures alter muscle mechanical actions is a critical first step toward identifying the cause of post-operative impairments and is necessary to develop effective interventions to augment deficient muscles and improve overall function.
PMCID: PMC4428973  PMID: 25843482
four-corner fusion; moment arm; proximal row carpectomy; wrist
20.  Individuals with Isolated Patellofemoral Joint Osteoarthritis Exhibit Higher Mechanical Loading at the Knee during the Second Half of the Gait Cycle 
Patellofemoral joint osteoarthritis is a highly prevalent condition and an important source of pain and disability. Nonetheless, biomechanical risk factors associated with patellofemoral joint osteoarthritis remain unclear. The purpose of this study was to compare biomechanical factors that are associated with patellofemoral joint loading during walking between individuals with isolated patellofemoral joint osteoarthritis and no osteoarthritis.
MR images of the knee were obtained using a 3D fast-spin echo sequence to identify patellofemoral joint cartilage lesions (patellofemoral joint osteoarthritis group). Thirty-five subjects with isolated patellofemoral joint osteoarthritis (29 females) and 35 control subjects (21 females) walked at a self-selected speed and as fast as possible. Peak knee flexion moment, flexion moment impulse and peak patellofemoral joint stress during the first and second halves of the stance phase were compared between groups.
When compared to the controls, individuals with patellofemoral joint osteoarthritis demonstrated significantly higher peak knee flexion moment (P =.03, Eta2 =.07), higher knee flexion moment impulse (P =.03, Eta2 =.07) and higher peak patellofemoral joint stress (P =.01, Eta2 =.10) during the second half of the stance phase. No significant group difference was observed during the first half of the stance phase.
Findings of this study suggest that increased mechanical loading (i.e. knee flexion moment, impulse and patellofemoral joint stress) during the second half of the stance phase is associated with patellofemoral joint osteoarthritis. Prevention and rehabilitation programs for patellofemoral joint osteoarthritis may focus on reducing the loading on the patellofemoral joint, specifically during late stance.
PMCID: PMC4404202  PMID: 25726158
patellofemoral joint; osteoarthritis; gait; stress; kinetics
21.  Morphological and positional changes of the carpal arch and median nerve during wrist compression 
The carpal tunnel is a fibro-osseous structure containing the median nerve and flexor tendons. Its cross-sectional area has been shown to increase during compressive force application to the carpal bones in modeling and in vitro studies. The purpose of this study was to investigate the morphological and positional changes of the carpal arch and median nerve while in vivo compressive force was applied in the radioulnar direction across the wrist.
Ultrasound images of the carpal tunnel and its contents were captured for 11 healthy, female volunteers at the distal tunnel level prior to force application and during force application of 10 and 20 N.
With applied force, the carpal arch width significantly decreased, while the carpal arch height and area significantly increased (P < 0.001). The median nerve shape became more rounded as the compressive force magnitude increased, reflected by decreases in the nerve’s flattening ratio and increases in its circularity (P < 0.001). The applied force also resulted in nerve displacement in the radial-volar direction.
This study demonstrates that noninvasively applying radioulnar compressive force across the wrist may potentially provide relief of median nerve compression to patients suffering from carpal tunnel syndrome.
PMCID: PMC4363297  PMID: 25661267
carpal tunnel syndrome; compression; force; median nerve; wrist
22.  Shoulder limited joint mobility in people with diabetes mellitus 
Limited joint mobility at the shoulder is an understudied problem in people with diabetes mellitus. The purpose of this study was to determine the differences in shoulder kinematics between a group with diabetes and those without diabetes.
Fifty-two participants were recruited, 26 with diabetes and 26 non-diabetes controls (matched for age, BMI and sex). Three-dimensional position of the trunk, scapula and humerus were collected using electromagnetic tracking sensors during scapular plane elevation and rotation movements.
Glenohumeral external rotation was reduced by 11.1° – 16.3° (P<0.05) throughout the humerothoracic elevation range of motion, from neutral to peak elevation, in individuals with diabetes as compared to controls. Peak humerothoracic elevation was decreased by 10–14°, and peak external rotation with the arm abducted was decreased 22° in the diabetes group compared to controls (P<0.05). Scapulothoracic and glenohumeral internal rotation motions were not different between the two groups.
Shoulder limited joint mobility, in particular decreased external rotation, was seen in individuals with diabetes as compared to control participants. Future research should investigate causes of diabetic limited joint mobility and strategies to improve shoulder mobility and prevent additional detrimental changes in movement and function.
PMCID: PMC4363299  PMID: 25595462
shoulder; limited joint mobility; kinematics; diabetes mellitus
23.  Glucose uptake heterogeneity of the leg muscles is similar between patients with multiple sclerosis and healthy controls during walking 
Difficulties in ambulation are one of the main problems reported by patients with multiple sclerosis. A previous study by our research group showed increased recruitment of muscle groups during walking but the influence of skeletal muscle properties, such as muscle fiber activity, has not been fully elucidated. The purpose of this investigation was to use the novel method of calculating glucose uptake heterogeneity in the leg muscles of patients with multiple sclerosis and compare these results to healthy controls.
Eight patients with multiple sclerosis (4 men) and 8 healthy controls (4 men) performed 15 min of treadmill walking at a comfortable self-selected speed following muscle strength tests. Participants were injected with ≈8 millicuries of [18F]-Fluorodeoxyglucose during walking after which positron emission tomography/computed tomography imaging was performed.
No differences in muscle strength were detected between multiple sclerosis and control groups (P > 0.27). Within the multiple sclerosis group differences in muscle volume existed between the stronger and weaker legs in the vastus lateralis, semitendinosus, and semimembranosus (P < 0.03). Glucose uptake heterogeneity between the groups was not different for any muscle group or individual muscle of the legs (P > 0.16, P ≥ 0.05).
Patients with multiple sclerosis and healthy controls showed similar muscle fiber activity during walking. Interpretations of these results, with respect to our previous study, suggest that walking difficulties in patients with multiple sclerosis may be more associated with altered central nervous system motor patterns rather than alterations in skeletal muscle properties.
PMCID: PMC4323621  PMID: 25541392
Positron Emission Tomography; Exercise; [18F]-Fluorodeoxyglucose; Computed Tomography; Clinical Disability; Muscle fiber activity
24.  Anterior Cruciate Ligament Biomechanics During Robotic and Mechanical Simulations of Physiologic and Clinical Motion Tasks: A Systematic Review and Meta-Analysis 
Investigators use in vitro joint simulations to invasively study the biomechanical behaviors of the anterior cruciate ligament. The aims of these simulations are to replicate physiologic conditions, but multiple mechanisms can be used to drive in vitro motions, which may influence biomechanical outcomes. The objective of this review was to examine, summarize, and compare biomechanical evidence related to anterior cruciate ligament function from in vitro simulations of knee motion. A systematic review was conducted (2004 to 2013) in Scopus, PubMed/Medline, and SPORTDiscus to identify peer-reviewed studies that reported kinematic and kinetic outcomes from in vitro simulations of physiologic or clinical tasks at the knee. Inclusion criteria for relevant studies were articles published in English that reported on whole-ligament anterior cruciate ligament mechanics during the in vitro simulation of physiologic or clinical motions on cadaveric knees that were unaltered outside of the anterior-cruciate-ligament-intact, -deficient, and -reconstructed conditions. A meta-analysis was performed to synthesize biomechanical differences between the anterior-cruciate-ligament-intact and reconstructed conditions. 77 studies met our inclusion/exclusion criteria and were reviewed. Combined joint rotations have the greatest impact on anterior cruciate ligament loads, but the magnitude by which individual kinematic degrees of freedom contribute to ligament loading during in vitro simulations is technique-dependent. Biomechanical data collected in prospective, longitudinal studies corresponds better with robotic-manipulator simulations than mechanical-impact simulations. Robotic simulation indicated that the ability to restore intact anterior cruciate ligament mechanics with anterior cruciate ligament reconstructions was dependent on loading condition and degree of freedom examined.
PMCID: PMC4298459  PMID: 25547070
anterior cruciate ligament reconstruction; knee kinetics and kinematics; knee injury prevention; joint motion simulation; robotic manipulation of joints; knee ligament mechanics
Patients six months after total knee arthroplasty demonstrate movement asymmetries and functional deficits, which may be related to poor functional performance. The aims of this study were to 1) compare biomechanical variables between subjects 6 months after total knee arthroplasty and an agematched healthy control group during a step up and over task and 2) determine the relationship between quadriceps strength, movement patterns and stair climbing performance.
Twenty patients 6 months following unilateral total knee arthroplasty and twenty healthy controls were enrolled. Participants completed questionnaires, isometric quadriceps strength testing and performance based tests to quantify functional performance. Motion analysis was performed during a step up and over task. Functional and biomechanical variables were analyzed using a 2×2 ANOVA. The symmetry ratios (operated/non-operated limb *100) for biomechanical variables were analyzed using independent t-tests. Pearson correlations were performed to determine the relationships between biomechanical variables, strength and stair climbing performance.
In the TKA group, subjects had lower peak moments, power and sagittal plane excursion in the operated knee compared to the contralateral knee (p < .05), while the hip on the operated side had greater power generation (p = .014). Compared to the control group, all symmetry ratios were significantly lower in the surgical group (p < .05). Stair climbing time was correlated with quadriceps strength of the operated limb (R=−0.762, p<0.001).
Individuals 6 months after total knee arthroplasty had worse performance with respect to biomechanics, quadriceps strength, and performance-based tests. Biomechanical asymmetries after TKA reduce the demand on the operated knee and increase reliance on the contralateral limb and ipsilateral hip.
PMCID: PMC4298478  PMID: 25467765

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