Multi-segmented foot and ankle (FandA) models provide more information regarding intrinsic foot motion compared to rigid-body models due to additional markers on bony landmarks of the foot. Marker placement sensitivity is a concern, especially in patients with bony abnormalities, because kinematics vary with marker placement deviations. PURPOSE: Assess kinematic changes due to marker placement error using the TSRHC multi-segmented FandA model. METHODS: Our participant was an 18yo female lacking any prior orthopedic conditions. The Plug-in-Gait model was used with the TSRHC model. An experienced clinician executed all marker placements, systematically moving each marker approximately 2.5mm within two planes. Three dynamic trials were collected for each condition, and static trials were used to calculate exact distances markers moved. Six force plates (AMTI) were utilized to confirm a consistent walking pattern. Graphs analyzed included: 1)PIG–ankle dorsiflexion, foot rotation, foot progression angle, 2)TSRHC–hindfoot, forefoot, FF-tibia. For each condition, the peaks of affected kinematic graphs were compared to assess correlations. Intra-trial error was determined by the maximum difference across walking trials. CONCLUSION: The hindfoot was most sensitive to transverse plane marker placement errors. Markers on metatarsals periodically rose vertically when moved laterally due to foot curvature causing errors in the sagittal plane as well. The forefoot also had transverse plane errors when metatarsal markers were moved. This case study illustrates the importance of proper marker placement training when utilizing a multi-segmented foot model. A thorough understanding of a utilized model is imperative, including how sensitive the model is to marker placement.
This study presents a new technique for acquiring ground reaction forces from novel, nanocomposite piezo-responsive foam (NCPF) sensors. A shoe was fitted with four NCPF sensors located at the heel, arch, ball, and toe positions. Running data was collected simultaneously from both the shoe sensors and from a force-sensing treadmill. A portion (30 randomly selected stance phases) of the treadmill data was used to develop a predictive stochastic model of GRF based on the sensor inputs. The stochastic model was then used to predict GRF for the remaining shoe sensor data, which was then benchmarked against the treadmill data. The results indicated that this model was able to predict forces in the x-axis (anterior-posterior) with 2.38% error, forces in the y-axis (medial-lateral) with 6.01% error, and forces in the z-axis (vertical) with 2.43% error. These novel sensors hold potential to dramatically improve both the ease and expense associated with GRF data, as well as allow unprecedented ability to measure GRF during real world applications outside of the laboratory.
Nucleotomy is a surgical procedure following herniation and also simulates the reduced nucleus pulpousus (NP) pressure that occurs with disc degeneration. Internal disc strains are an important factor in disc function, yet it is unclear how internal strains are affected by nucleotomy. Grade II L3-L4 human cadaveric discs (n=6) were analyzed intact and after a partial nucleotomy that removed 30-50% of the NP through a left posterolateral incision (incision) while the contralateral side remained intact (uninjured). Two cycles of stress-relaxation testing were performed for reference (50N) and loaded (0.70MPa) configurations. After each 8hour equilibration period, the reference and loaded discs were imaged separately in a 7T MRI scanner (0.3mm isotropic resolution). The reference and loaded images were registered to calculate internal strain within the annulus fibrosus (AF) lamellae and discs were averaged to create anatomical templates. Circumferential, radial, and axial strains for each disc were transformed to the average templates, effectively normalizing the strains. Five circumferential regions were defined within the mid-third of the templates. Nucleotomy altered disc strains on both the incision and uninjured sides from the intact state. Strain fields were inhomogeneous through the five regions. Mean circumferential strain was unaffected by nucleotomy on the uninjured side, but decreased with incision, showing hoop strains through the AF were disrupted. Mean compressive axial strains were higher after nucleotomy, effectively reducing AF stiffness, and mean radial strains were unaltered after partial nucleotomy. These findings are important to address etiology and progression of degeneration, and to develop and evaluate therapeutic interventions.
Purpose: To validate an instrumented figure skating blade that is designed to measure impact forces while skating. Methods: Seven subjects (Age: 21.3±2.8 yrs, Ht: 166.9±2.5 cm, Mass: 64.7±7.9 kg) performed 20 landings each onto artificial ice while landing on the instrumented blade from heights of 17.5cm, 25cm, and 33cm. A custom instrumented blade calibrated to measure in forces in Newtons (N) was used to measure impact forces (1000Hz) during landings. These forces were compared to forces obtained while subjects landed on AMTI force plates located underneath the artificial ice surface. Boot angle (250Hz) and force plate data (1000Hz) were collected using Vicon Nexus. Custom LabVIEW programs were used to determine peak force, loading rate, impulse, and the correlation between the blade force data and the force plate data. Paired T-tests were used to compare peak force, loading rate, and impulse between the blade and force plate data. Alpha = 0.05. Results: Correlations between the blade force data and force plate data were good to excellent: mean r (±SD) = .86 ± 0.08. No significant differences were found for peak force and impulse between the blade and force plate data. Peak force means (±SD) were 1353.7 ± 352.2 N for the blade and 1361.2 ± 309.7 N for the force plate (p=.86). Conclusion: The custom instrumented blade is a valid tool for measuring peak forces and impulse during landings. Current research is focused on increasing the gain of the instrumented blade to improve loading rate accuracy.
Asymmetries in discrete measures following anterior cruciate ligament reconstruction (ACL-R) during landing have been reported to be risk factors for secondary ACL injuries. Our purpose was to examine the impact of functional brace wear on kinematic and kinetic inter-limb movement symmetry during landing in ACL-R patients. 20 adolescent athletes (15.8 ± 1.2 years) (7 male, 13 female) 6 months following ACL reconstruction performed 5 trials of a stop-jump task in both a braced (B) and non-braced (NB) condition, with the first landing being analyzed. A custom fit functional knee brace (DJO, Vista, CA) was worn on the ACL reconstructed limb (AL) during the B trials. Mean curves were created for each limb (AL and unaffected limb (UL)) for the vertical (vGRF) and anterior-posterior ground reaction forces (apGRF) and frontal and sagittal knee angles and moments. Coefficients of multiple determination (CMD) between the AL and UL curves were compared between B and NB conditions with students’ t-tests (p≤0.05). No significant differences existed for movement and loading symmetry between B and NB conditions among all subjects. Secondary analysis revealed significant differences in apGRF (p=0.014), vGRF (p=0.011) and sagittal knee angles (p=0.003) in subjects with improved sagittal knee angle symmetry in the B condition. The data show that brace wear improves loading symmetry in adolescent patients that also exhibit improved sagittal knee angle symmetry while braced 6 months following ACL-R. Identifying factors that affect inter-limb movement and loading response to brace wear could assist in determining each patient’s need for a brace.
Purpose: Research supports the use of ballroom dance to improve balance in individuals with Parkinson’s disease (PD). This study used the Mark Morris Dance for PD program as a template for dance classes to examine the effects of dance on gait, balance, and quality of life in individuals with PD.
Subjects : Eleven individuals with mild to moderate PD participated in the study.
Methods : A trained instructor led dance classes for subjects once a week for 12 weeks. Participants were encouraged to use the Mark Morris Dance for PD At Home DVD twice a week for 45 minutes. Classes included a 20 min. seated warm up; a 20 min. supported standing portion focused on balance and strength; and 30 min. partnered movements for swing, shag, or tango. Data collected before and after the intervention included gait parameters (Protokinetics Zeno walkway), sway area (AMTI force platform) during mCTSIB, Mini-BESTest, Falls Efficacy Scale, Apathy Scale and PDQ-39. A paired-samples t-test was performed.
Results : Participants had significant decrease in apathy following the intervention (P = 0.018). A significant decrease in the percentage of the double support phase of gait indicated individuals spent less time with both feet in contact with the ground (P = 0.019).
Conclusions : An instructor-led dance class based on the Dance for PD program once per week for 12 weeks improved certain aspects of quality of life, but not necessarily gait and balance. Further research with increased frequency of supervised dance classes is indicated.
Dual-mobility (DM) bearing implants reduce the incidence of dislocation following total hip arthroplasty (THA) also it increases hip stability and range of motion (ROM). However, it is unclear whether the improved ROM will lead to better mechanical symmetry. Ground reaction forces (GRF) analysis would help to understand joint compensatory effects and symmetry in THA patients. The purpose was to compare GRF symmetry between the operated and non-operated limbs in THA patients, of either DM or conventional-cup (CC) implant, during standing and sitting tasks. Twenty-four patients and 10 control participants (5M/5F; 62±10 years; 26±4 kg/m2) were recruited and underwent motion analysis before and nine months after THA. Patients were randomly assigned to either a DM (8M/4F; 63±5 years; 28±3 kg/m2) or CC (9M/3F; 62±5 years; 28±5 kg/m2) cementless replacement. Participants performed five sit-to-stand and stand-to-sit trials, with a bench adjusted to their knee heights and each foot on an individual force plate, with motion capture and GRF data been collected. Control group demonstrated standing (0.4±1.6%) and sitting (1.2±1.6%) symmetry. During sit-to-stand, DM group reduced its SI from pre- (5.5±1.6%) to post-op (1.2±1.9%, p=0.09), while the CC group showed a significant improvement (from 8.7±2.1% to 1.5±1.4%, p=0.02). For stand-to-sit, DM group reduced its SI (from 3.3±2.2% to 0.5±1.7%) while the CC group again had a significant improvement (from 8.2±2.1% to 1.2±1.1%, p=0.02). Larger improvements in symmetry were noticed for both groups during trunk flexion when standing; and for CC group during trunk extension when sitting. After surgery, patients with either implant reached SI inside the margin of 1.5 standard deviation from the CTRL (p>0.05). Statistical significance on paired condition was only observed on CC group due to its high pre-op score; however, both surgical groups showed an improved symmetry after THA.
Gait Mechanics Depend Upon Quadriceps Central Activation Ratio in an Anterior Knee Pain Cohort
Son SJ*, Kim HS†, Wiseman B‡, Seeley MK*, Hopkins JT*: *Brigham Young University, Provo, UT, †West Chester University, West Chester, PA, ‡West Virginia University, Morgantown, WV.
Context: Quadriceps deficits are often present in an anterior knee pain (AKP) population. However, common self-reported classification tools including Visual Analog Scale (VAS), Kujala Anterior Knee Pain (KAKP), Tampa Scale for Kinesiophobia (TSK), Tegner Activity Level (TAL) scores, and/or other subject inclusion criteria may not be sensitive enough to identify specific movement characteristics in patients with AKP. Quadriceps central activation ratio (CAR) may help to discriminate movement characteristics in patients with AKP. Objective: To examine gait mechanics between two subdivisions of AKP patients, separated by quadriceps function (CAR < 0.95 and CAR > 0.95). AKP patients were defined by VAS, KAKP, TSK, and TAL scores. Design: Cohort. Setting: Controlled laboratory. Patients or Other Participants: 30 (M=16, F=14; 22.3±3 yrs, 175±9 cm, 72.5±14 kg) AKP patients participated: 15 Quadriceps Deficit (QD: CAR = 0.91±0.04, VAS = 3.87±1.3, KAKP = 82.9±6.6, TSK = 37.9±4.7, TAL = 6.3±1.2) and 15 Quadriceps Functional (QF: CAR = 0.97±0.01, VAS = 3.93±0.7, KAKP = 79.3±7.9, TSK = 36.9±5.2, TAL = 6.8±1.4). Interventions: Subjects performed three quadriceps maximum voluntary contractions (MVC) for 3 sec on a Biodex dynamometer (100 Hz). When MVC torque plateaued 1.5-2 sec later, a superimposed burst was transmitted to two electrodes placed on their quadriceps to measure CAR. Two successful trials were averaged for data analysis. Subjects performed five gait trials at a self-selected walking speed. Gait data were collected using high-speed video (240 Hz) and a force plate (1200 Hz). A functional analysis was used to detect mean between-group differences in gait mechanics during the entire stance phase (0-17% = loading response, 18-50% = mid-stance, 51-83% = terminal stance, and 84-100% = pre-swing). This analysis allowed us to compare variables as polynomial functions rather than discrete values. If 95% confidence intervals did not overlap zero, significant differences existed between groups (p < 0.05). Main Outcome Measures: Sagittal-plane knee joint angle (˚), internal knee joint torque (N∙m), and vertical ground reaction force (VGRF; N/kg). Results: Relative to QF patients, QD patients demonstrated (i) decreased knee flexion angle at 4-90% of stance, (ii) reduced internal knee extension torque at 14-32% of stance, and (iii) reduced VGRF at 19-37% of stance and increased VGRF at 46-70% of stance (p < 0.05). Conclusions: The present data suggest that relative to QF patients, QD patients adopt quadriceps weakness gait mechanics that have been reported in individuals with knee osteoarthritis, ACL reconstruction, and effused knee joints. These alterations may create long-term compensatory gait patterns at the knee and adjacent ankle and hip joints, which may lead to mechanical and biological changes in knee articular cartilage. Future research is needed to examine a potential relationship between these gait alterations and articular cartilage health over the long-term.
The established pathway of cognitive decline identifies Mild Cognitive Impairment (MCI) as a common pre-dementia syndrome. As MCI can represent the endpoint of cognitive decline or a transient state, more predictive diagnostic tools are required. A new pre-dementia syndrome, Motoric Cognitive Risk (MCR) syndrome, has been proposed. It is defined by slow gait and cognitive complaints but absence of dementia and mobility disability. MCR aims to improve on the predictive power of MCI, this study aims to explore it’s claim.
Associations have been uncovered between differing cognitive domains and specific characteristics of gait. Leveraging the gait-cognitive function relationship is a novel approach to potentially highlighting those experiencing cognitive decline. However, the diagnostic tool of MCR is a new construct and currently imperfect, its efficacy not fully validated and sensitivity for dementia prediction relatively unknown. Reliable data on prevalence and risk factors help contribute to this validation process.
In this presentation prevalence data for a multi-country aging study and a nationally representative community dwelling aging study will be presented. The variables available in both datasets which will be of interest in this study include; Gait Speed, Global Cognition (Mini-Mental State Exam (MMSE) score), Presence of Cognitive Complaints, Age, Body Mass Index (BMI), Dementia diagnosis (reported or imputed) and Waist Circumference. This study will inform the following research project, which will aim to assess whether specific gait components or combinations alone are better than the MCR construct in their association to cognitive decline.
INTRODUCTION: Patellofemoral pain (PFP) is a common condition seen in orthopedic practice, accounting for approximately 25-40% of all knee injuries . A commonly cited hypothesis as to the cause of PFP is elevated patellofemoral joint (PFJ) stress  secondary to abnormal PFJ structure. Previous studies have shown that persons with PFP exhibit altered patella position , abnormal femoral morphology , and decreased patella cartilage thickness  when compared to healthy individuals. However, the influence of the abnormal morphology on PFJ stress is unknown.
METHODS: Nineteen subjects (10 PFP and 9 pain-free controls) were recruited for this study. Each subject completed 2 phases of data collection: magnetic resonance imaging (MRI) assessment and biomechanical testing. The measurement of morphological variables (patella height (Insall-Salvati ratio or ISR), lateral trochlear inclination angle (LTI), and patella cartilage thickness). For the biomechanical testing, kinematic, kinetic, and electromyographic were obtained.
RESULTS AND DISCUSSION: Pearson correlation coefficients revealed that only patella height (r=0.48, p=0.018) and patella cartilage thickness (r=-0.58, p=0.005) were significantly correlated with peak hydrostatic pressure (Table 1). Results of the stepwise regression analysis revealed that patella cartilage thickness was the single best predictor of peak hydrostatic pressure, followed by patella height. Together, these 2 variables explained 50% of the variance in peak PFJ stress.
The results of the current study support the premise that PFJ stress is associated with PFJ morphology. Patella height was the best predictor of PFJ stress with greater degrees of patella height being correlated with greater stress. This is logical given that a higher positioned patella articulates with the more shallow portion of the trochlear groove, thus decreasing PFJ contact area . The finding that patella cartilage thickness was negatively correlated with PFJ stress is in agreement with the results of Li et al. , who demonstrated that a reduction of cartilage thickness causes increase cartilage stress. Furthermore, our findings revealed that 50% of the variance in PFJ stress could be explained by morphological factors.
CONCLUSIONS: Identifying the underlying factors that contribute to elevated PFJ stress is an important step in developing effective interventions for persons with PFP. Although abnormal structure may not be correctable through conservative measures, it is important to recognize abnormal structure may play a role in contributing to pain and pathology.