Electromagnetic Motion Tracking System Research Articles

Analyzing the Evolution of Needle and Ultrasound Probe Manipulation Skills of Interventional Radiology Trainees With Time and Experience.

To test the hypothesis that hand motion analysis can measure the progression of needle and ultrasound probe manipulation skills of interventional radiology trainees in central venous line placement. An expert cohort of 6 interventional radiologists and 4 anesthesiologists and a trainee cohort of 6 novice trainees (<50 central lines) and 5 experienced trainees (>50 central lines) performed simulated central venous access. Four novices and 1 experienced trainee repeated the task 1 year later. An electromagnetic motion tracking system tracked the needle hand and ultrasound probe. Path length, translational, and rotational movements were calculated separately for the needle hand and probe sensor. These metrics were used to calculate motion metrics based scores on a scale of 0 to 3 for each sensor. Nonparametric statistics were used, and the data are reported as median ± interquartile range. Comparing novice and experienced trainees, there was a significant difference in probe scores (experienced vs. novice: 1 ± 2 vs. 0 ± 0, P = 0.04) but not in needle-hand scores (1 ± 1.5 vs. 0 ± 1, P = 0.26). Trainees showed a significant increase in probe scores at the 1-year follow-up (baseline vs. follow-up: 0 ± 1 vs. 2.5 ± 1.8, P = 0.003), but no significant difference was observed in the needle manipulation metrics. Experts differed significantly from experienced trainees for all metrics for both sensors (P < 0.05), with the exception of the path length of the probe. Acquisition of improved dexterity of the probe may occur before improvement in the dexterity with the needle hand for interventional radiology trainees.

Cadaveric Analysis of Plantar Fascia Tension and Windlass Mechanism and Development of Plantar Fascia-Specific Stretching Device

Category:OtherIntroduction/Purpose:Plantar fasciitis is the most common cause of heel pain in adults, affecting 1 out of 10 of the population at some point during their lifetime. Plantar specific stretching programs are popularity among foot and ankle surgeons consisting of passively dorsiflexing foot and using thumb to apply pressure. This technique is not without limitations. Certain patients are unable to properly perform the stretching techniques, such as limited mobility from advanced age, disability, or simply from performing stretching exercises incorrectly. The aims of this study are; first, identify what configuration of plantar-specific stretching combined with applied pressure to the plantar aponeurosis generates the greatest tensional force in the plantar fascia. And second, to construct a prototype device that could simulate these forces in a hands-free technique.Methods:Six (will be 10) fresh-frozen, morphologically normal cadaver feet (Medcure, RI) were utilized. Plantar fascia was exposed, ankle was fixed at 90-degree dorsiflexion using Calcaneo-Tibial Schanz Pin, specimen was then inverted and potted in a custom-made box (Smooth-Cast 300q, PA). Using an electromagnetic motion tracking system (Liberty, Polhemus, VT), the motion of sensors was recorded at 120 Hz. Utilizing tissue adhesive glue (Vetbond, 3M, Minnesota), the first sensor was attached to medial calcaneal tuberosity, and the second sensor was placed 5 cm distal to the first sensor on the plantar aponeurosis. Custom- built testing apparatus was made for induction of MTP dorsiflexion application of pressure on the plantar aponeurosis to mimic current conservative treatments. Weights were added to the custom build stretcher device in 10Lb increments. Strain percentage was calculated as the change in length divided by the baseline length position (condition 1) using the formula: ([L − Lo]/Lo) × 100Results:Dorsiflexion of 2nd-5th MTPs increases strain percentage more in comparison with 1st MTP dorsiflexion (Condition 3>4>2). This might show that dorsiflexing of 1st metatarsal is less effective at straining the plantar fascia because of the midfoot motion. By adding thumb pressure, strain percentages go higher, up to a point that in condition 7 (dorsiflexing all MTPs in combination of thumb pressure) it is significantly higher than our baseline condition (P=0.0385). It is noteworthy that, stretcher device itself (condition 8), cannot replicate conditions 4 or 7 strain percentages. When adding direct pressure and weight to the stretcher device (conditions 12 and 13), strains are even higher than condition 7 and also are significantly higher than the baseline (P= 0.0090 and 0.0291 respectively).Conclusion:The stretcher device itself is insufficient for stretching the plantar fascia, supporting the hypothesis of this study that we need a direct forceful pressure on the plantar aponeurosis as well. Our customized plantar stretcher not only can replicate the conventional stretching program, but also can produce higher strains on the plantar aponeurosis than the current manual application of plantar specific stretching. This device may impact the rehabilitation process in patients with advanced age as well as patients with spine mobility limitation who cannot perform manual stretching programs.

Smoothness metric during reach-to-grasp after stroke: part 2. longitudinal association with motor impairment

BackgroundThe cause of smoothness deficits as a proxy for quality of movement post stroke is currently unclear. Previous simulation analyses showed that spectral arc length (SPARC) is a valid metric for investigating smoothness during a multi-joint goal-directed reaching task. The goal of this observational study was to investigate how SPARC values change over time, and whether SPARC is longitudinally associated with the recovery from motor impairments reflected by the Fugl-Meyer motor assessment of the upper extremity (FM-UE) in the first 6 months after stroke.MethodsForty patients who suffered a first-ever unilateral ischemic stroke (22 males, aged 58.6 ± 12.5 years) with upper extremity paresis underwent kinematic and clinical measurements in weeks 1, 2, 3, 4, 5, 8, 12, and 26 post stroke. Clinical measures included amongst others FM-UE. SPARC was obtained by three-dimensional kinematic measurements using an electromagnetic motion tracking system during a reach-to-grasp movement. Kinematic assessments of 12 healthy, age-matched individuals served as reference. Longitudinal linear mixed model analyses were performed to determine SPARC change over time, compare smoothness in patients with reference values of healthy individuals, and establish the longitudinal association between SPARC and FM-UE scores.ResultsSPARC showed a significant positive longitudinal association with FM-UE (B: 31.73, 95%-CI: [27.27 36.20], P < 0.001), which encompassed significant within- and between-subject effects (B: 30.85, 95%-CI: [26.28 35.41], P < 0.001 and B: 50.59, 95%-CI: [29.97 71.21], P < 0.001, respectively). Until 5 weeks post stroke, progress of time contributed significantly to the increase in SPARC and FM-UE scores (P < 0.05), whereafter they levelled off. At group level, smoothness was lower in patients who suffered a stroke compared to healthy subjects at all time points (P < 0.05).ConclusionsThe present findings show that, after stroke, recovery of smoothness in a multi-joint reaching task and recovery from motor impairments are longitudinally associated and follow a similar time course. This suggests that the reduction of smoothness deficits quantified by SPARC is a proper objective reflection of recovery from motor impairment, as reflected by FM-UE, probably driven by a common underlying process of spontaneous neurological recovery early post stroke.

Assessment of the cervical spine mobility by immersive and non-immersive virtual reality

IntroductionDespite many devices are helpful for motion analysis, there is still no established standard technique for the assessment of cervical spine mobility. ObjectiveTo compare differences in using immersive or non-immersive virtual reality (VR) for the assessment of the sensorimotor movement of the cervical spine in healthy subjects. MethodsThirty-five healthy adults were asked to perform head rotation, flexion, extension, lateral flexion, reaching and repositioning tasks with the head. The same tasks were performed interacting with both non-immersive and immersive virtual reality. Random sequence determined which of the environments was used as first assessment. Range of motion and kinematics i.e. number of completed targets, time of execution (seconds), spatial length (cm), angle distance (°), jerk of the cervical spine, were automatically computed by a 6D electromagnetic motion tracking system. ResultsThe following variables were significantly larger in immersive than non-immersive VR: head right rotation (p = 0.027), extension (p = 0.047), flexion (p = 0.000), time (p = 0.001), spatial length (p = 0.004), jerk target (p = 0.032), trajectory repositioning (p = 0.003), jerk target repositioning (p = 0.007). A regression model showed that assessment in both VR environments can be influenced by dependent and independent variables. ConclusionsImmersive VR provided more accurate measurement of cervical spine than non-immersive VR in healthy adults.

Effects of illuminance and contrast on the reading of Chinese text by myopes

Twenty-four young adults with myopia in both eyes and no anisometropia participated in this study. Observers were instructed to read one A4-sized page of Chinese text at different levels of illuminance and text contrast, while their reading distance, head tilt angle and reading speed were recorded using an electromagnetic motion tracking system. Four illuminances (3, 30, 300 and 600 lx) and two text contrast levels (90% and 45%) were tested in randomised order. Observers tended to shorten their reading distance and increase their head tilt angle when reading at low illuminance. In addition, their reading speed was markedly slower at low illuminance and low contrast. These effects were found for both text contrast conditions but were greater at low contrast. Illuminance and text contrast play a critical role in myope’s reading behaviour. An illuminance of 300 lx or more with high-contrast text allows for good reading posture and rapid reading of Chinese text.

A Biomechanical Evaluation of the DRUJ After Distal Oblique Bundle Reconstruction

Distal oblique bundle (DOB) reconstruction for distal radioulnar joint (DRUJ) instability is an alternative to the Adams 2-incision distal radioulnar ligament reconstruction. The DOB reconstruction offers a single incision and is a technically less demanding procedure requiring a shorter tendon autograft. The DOB and Adams reconstruction may provide similar stability. This study sought to compare the biomechanical stability of the 2 DRUJ reconstructions. We hypothesized that DOB reconstruction would result in equivalent DRUJ translation, cyclic loading to failure, and maximal load to failure compared with the Adams reconstruction. Ten fresh-frozen cadaver arms underwent DOB or Adams reconstructions. Volar, dorsal, and total translation of the radius relative to the ulna at the DRUJ were measured before and after each reconstruction. Translation was measured with a 20-N force in neutral position and 60° in pronation and supination. Measurements were obtained using a custom jig and electromagnetic motion-tracking system sensors. Total cycles and maximal load to failure of each reconstruction were measured and recorded using an electromechanical testing machine. There was a DOB incidence of 70%. Distal radioulnar joint translation, total cycles, and failure load were similar for the 2 reconstructions. On average, the DOB reconstruction had less dorsal translation than did the Adams in supination. Translation in the DOB reconstruction was similar to that of native DRUJs. In supination, on average, the Adams reconstruction had greater total, volar, and dorsal translation compared with native DRUJs. In terms of translation, cyclical loading, and maximal load to failure, the DOB reconstruction for DRUJ instability is similar to the Adams reconstruction. This pilot study supports the DOB reconstruction as a possible alternative to the Adams reconstruction for DRUJ instability. The DOB reconstruction may theoretically reduce patient morbidity because it requires only one incision and a shorter tendon graft. However, further clinical and cadaveric studies are required to determine biomechanical equivalence and impact on patient morbidity.

Back muscle activity and sagittal spinal alignment during quadruped upper and lower extremity lift in young men with low back pain history

BackgroundQuadruped upper and lower extremity lift (QULEL) is performed for selective training of the lumbar multifidus muscle in patients with low back pain (LBP) or individuals with LBP history (LBPH). However, the activities of the back muscles and sagittal spinal alignment during QULEL are not clarified in individuals with LBPH. Research questionThis study aimed to analyze the activities of the back muscles and sagittal spinal alignment during QULEL in young male with LBPH. MethodsThe study comprised 9 asymptomatic young men and 8 young men with LBPH. The activities of the lumbar multifidus, latissimus dorsi and thoracic erector spinae, and lumbar erector spinae muscles were measured using surface electromyography. The flexion angles of the upper and lower thoracic spine, and extension angle of the lumbar spine were measured using a 6-DF electromagnetic motion tracking system. The association with LBPH was investigated using multiple logistic regression analysis with a forward selection method, with the activities of the back muscles, sagittal spinal alignment, age, body height, and body weight as independent variables. ResultsMultiple logistic regression analysis (p = 0.0002) showed that the activity of the latissimus dorsi and thoracic erector spinae muscles in the side on which the lower extremity was lifted and body height were significant and independent determinants of LBPH, but other factors were not. SignificanceThe results of this study suggest that the activity of the latissimus dorsi and thoracic erector spinae muscles increases while there are no decrease in activity of the lumbar multifidus muscle and excessive extension of the lumbar spine during QULEL in young men with LBPH.

Sample Entropy of Speed Power Spectrum as a Measure of Laparoscopic Surgical Instrument Trajectory Smoothness.

In this study the complexity of the speed power spectrum is assessed as a metric for measuring trajectory smoothness. There are a variety of published methods for analyzing trajectory smoothness but many lack validity. This preliminary study took an information theoretic approach to assess trajectory smoothness by applying the sample entropy measure to the speed power spectrum of simulated and experimental trajectories. The complexity measurements of the speed power spectrum were compared to a traditional jerk-based measure of trajectory smoothness, namely $\log $-dimensionless jerk. The approach was first tested on basic simulated shape tracings with varying locations of sporadic movement, simulated as Gaussian noise. This method was duplicated in an experimental setting with the same shapes and locations of sporadic movement by capturing the trace trajectories using an electromagnetic motion tracking system. Finally, this approach was applied to kinematic data of laparoscopic surgical instrument tips, captured over 105 iterations of a basic surgical task. Analysis from all three testing scenarios showed that there is a statistically significant linear correlation between $\log $-dimensionless jerk and the sample entropy of speed power spectra.

Effects of Increased Gluteus Muscle Activation on Hip and Trunk Kinematics during Single-leg Landing

The gluteus maximus (GM) has a triplanar function at the hip joint. It was hypothesized that increased GM activation before and after foot contact (FC) on landing would affect triplanar hip and trunk kinematics and anterior cruciate ligament (ACL) injury risk. PURPOSE: To examine how increased GM activation before and after FC affect hip angles and trunk inclination during single-leg landing. METHODS: A double-leg drop jump from a 30-cm box, followed by single-leg landing onto a force plate, was performed by 13 males and 15 females in both control (CC) and experimental conditions (EC). In EC, transcutaneous electrical stimulation was applied to increase GM activation immediately before FC and during single-leg landing. Kinetic and kinematic data were collected using a force plate and 3-dimensional electromagnetic motion tracking system, respectively. Hip joint angles and sacrum and thorax inclination angles in space on FC, peak ground reaction force (GRFpk), and peak knee extensor moment (KEMpk) during single-leg landing were calculated. Comparisons were performed using two-way (sex×conditions) repeated measures analysis of variance with a significance level < .05. RESULTS: The hip joint exhibited more abduction (EC vs. CC at FC, GRFpk, and KEMpk, respectively: -13.2 ± 7.8° vs. -9.5 ± 6.3°, -8.9 ± 7.7° vs. -4.9 ± 6.8°, -3.3 ± 8.9° vs. -.2 ± 6.5°) and external rotation (-14.8 ± 8.5° vs. -9.8 ± 9.9°, -8.0 ± 3.6° vs. -3.6 ± 9.7°, -6.1 ± 9.7° vs. -1.6 ± 11.2°) at all time points in EC than in CC. The sacrum showed more lateral inclination toward the supporting leg at all time points (14.3 ± 6.4° vs. 11.1 ± 6.4°, 12.1 ± 6.4° vs. 9.0 ± 6.1°, 8.9 ± 7.1° vs. 6.7 ± 6.2°) and more erect position at KEMpk in EC (-1.0 ± 10.6°) than at CC (-4.6 ± 10.5°). No significant differences were observed in thoracic inclination angles. No significant interactions were observed among all variables. CONCLUSIONS: Increased GM before and after FC on single- leg landing may have positive effects on frontal and transverse plane hip motion to reduce ACL injury risk. However, excessive GM activation may result in excessive trunk lean toward the supporting leg and more erect position, which increase risk for ACL loading. Thus, appropriate GM activation is necessary to protect the ACL during single-leg landing.

Elbow Biomechanics of Pitching: Does Age or Experience Make a Difference?

Background:Elbow pain and elbow injuries are common in youth baseball players. It is not clear whether pitching experience and/or age creates biomechanical differences at the elbow and whether these differences place an athlete at greater risk.Hypotheses:(1) Youth pitchers will have differing elbow kinematics with regard to flexion/extension, internal/external rotation, and pronation/supination when compared with nonbaseball athletes and (2) younger youth pitchers will have differing elbow kinematics when compared with older youth pitchers.Study Design:Case-control study.Level of Evidence:Level 4.Methods:Twenty-seven healthy male youths age 10 to 18 years were recruited and divided into an experience group (n = 18 pitchers) and a no experience group (n = 9 nonbaseball athletes). The experience group was subdivided by age into the younger experience subgroup (n = 10 pitchers) and the older experience subgroup (n = 8 pitchers). Biomechanics were recorded using an electromagnetic motion tracking system. Subjects from each group were averaged together, and a Mann-Whitney U test was utilized for statistical analysis.Results:The experience group had greater external rotation during late cocking (−47.8° vs 5.8°) and greater flexion during early cocking (112.8° vs 100.1°). The younger experience subgroup had greater range of motion with supination-pronation during early cocking (21.9° vs 11.2°) and late cocking (5.9° vs 2.0°).Conclusion:Youth athletes with pitching experience had an increase in maximal external rotation in late cocking and maximal flexion in early cocking, which suggests experience may be a factor to these parameters. The age of experienced baseball pitchers may be a factor due to differences observed with supination and pronation.Clinical Relevance:Learning to throw is a skill that leads to changes in elbow motion; however, these changes may be stable once athletes reach grade school age. Minimal differences were noted between the younger and older experience subgroups, which may underscore the importance of teaching proper mechanics at a young age.

Quantitative Assessment of Parkinsonian Tremor Based on an Inertial Measurement Unit

Quantitative assessment of parkinsonian tremor based on inertial sensors can provide reliable feedback on the effect of medication. In this regard, the features of parkinsonian tremor and its unique properties such as motor fluctuations and dyskinesia are taken into account. Least-square-estimation models are used to assess the severities of rest, postural, and action tremors. In addition, a time-frequency signal analysis algorithm for tremor state detection was also included in the tremor assessment method. This inertial sensor-based method was verified through comparison with an electromagnetic motion tracking system. Seven Parkinson’s disease (PD) patients were tested using this tremor assessment system. The measured tremor amplitudes correlated well with the judgments of a neurologist (r = 0.98). The systematic analysis of sensor-based tremor quantification and the corresponding experiments could be of great help in monitoring the severity of parkinsonian tremor.

Influence of Near Tasks on Posture in Myopic Chinese Schoolchildren.

ABSTRACTPurposeTo investigate near-vision posture in Chinese myopic schoolchildren and compare near-vision posture during different near-vision tasks (i.e., playing video games, reading, and writing).MethodsThe study investigated 120 myopic children (grades 1 through 6 and aged 6 to 13 years). An electromagnetic motion-tracking system was used for continuous measurements of the working distance and head declination of the subjects while they were playing video games or reading or writing at a desk. The reading and writing documents were adjusted by grade level (i.e., grades 1 to 2, 3 to 4, and 5 to 6). For analysis, the subjects were grouped in two refractive groups according to their median spherical equivalent refractive error (−1.50D).ResultsThe myopic schoolchildren used close working distances for all tasks: 21.3 ± 5.2 cm (video games), 27.2 ± 6.4 cm (reading), and 24.9 ± 5.8 cm (writing). The mean head declinations were 63.5 ± 12.2 deg (video games), 37.1 ± 12.8 deg (reading), and 44.5 ± 14.1 deg (writing). Working distance decreased significantly across time for the reading and writing tasks (p < 0.001). Head declination increased significantly across time only for the reading task (p < 0.001). Grade level significantly influenced working distance, but the difference was not significant when working distance was adjusted by the subject’s size. No differences were observed within the refractive or the accommodative lag groups in terms of the posture data (p > 0.05). Working distance was negatively correlated with head declination (r = −0.53, p < 0.001).ConclusionsClose working distances were observed for Chinese myopic schoolchildren. The attention dedicated to each task, the task difficulty, and the page/screen size may affect near working distance and head declination. Handheld video games were associated with the closest working distance, which may be a risk factor for myopia progression, according to previous studies.

Sex Differences During an Overhead Squat Assessment.

A disparity exists between the rates of male and female lower extremity injuries. One factor that may contribute to this disparity is high-risk biomechanical patterns that are commonly displayed by females. It is unknown what biomechanical differences exist between males and females during an overhead squat. This study compared lower extremity biomechanics during an overhead squat and ranges of motion between males and females. An electromagnetic motion tracking system interfaced with a force platform was used to quantify peak lower extremity kinematics and kinetics during the descent phase of each squat. Range of motion measurements were assessed with a standard goniometer. Differences between male and female kinematics, kinetics, and ranges of motion were identified with t tests. Males displayed greater peak knee valgus angle, peak hip flexion angle, peak vertical ground reaction forces, and peak hip extension moments. Males also displayed less active ankle dorsiflexion with the knee extended and hip internal and external rotation than females. No other differences were observed. The biomechanical differences between males and females during the overhead squat may result from differences in lower extremity ranges of motion. Therefore, sex-specific injury prevention programs should be developed to improve biomechanics and ranges of motion.

The effect of cross links on rotational stiffness of scoliosis constructs

The purpose of this study is to investigate what effect cross links have on scoliosis constructs and whether cross links may be used instead of pedicle screws at the apex of the deformity The rotational stiffness of six different construct designs was investigated on scoliotic sawbone models with zero, one or two cross links. In three of the constructs the screws at the apex were removed. Testing was performed to an average torque of 3Nm and ration was detected using electromagnetic motion tracking system. The stiffness in axial rotation of all constructs increased with the number of cross links, however the difference was not statistically significant. In constructs with apical screws the stiffness increased by 3.01% and 12.9% for one and two cross links respectively. In constructs without apical screws the increase was 1.64% and 14.3% for one and two cross links respectively. The total stiffness of the construct increased with the addition of apical screws by 20%, 21.7% and 18.8% for zero, one and two cross links respectively. This increase was statistically significant using a paired t-test (p= 0.01142). On the basis of these results we conclude that the use of cross links in scoliosis correction surgery is not necessary. Pedicle screws positioned at the apex of the scoliosis curve statistically increase the stiffness in axial rotation and are therefore necessary to promote an environment suitable for bony fusion.

Acromiohumeral distance and 3-dimensional scapular position change after overhead muscle fatigue.

Muscle fatigue due to repetitive and prolonged overhead sports activity is considered an important factor contributing to impingement-related rotator cuff pathologic conditions in overhead athletes. The evidence on scapular and glenohumeral kinematic changes after fatigue is contradicting and prohibits conclusions about how shoulder muscle fatigue affects acromiohumeral distance. To investigate the effect of a fatigue protocol resembling overhead sports activity on acromiohumeral distance and 3-dimensional scapular position in overhead athletes. Cross-sectional study. Institutional laboratory. A total of 29 healthy recreational overhead athletes (14 men, 15 women; age = 22.23 ± 2.82 years, height = 178.3 ± 7.8 cm, mass = 71.6 ± 9.5 kg). The athletes were tested before and after a shoulder muscle-fatiguing protocol. Acromiohumeral distance was measured using ultrasound, and scapular position was determined with an electromagnetic motion-tracking system. Both measurements were performed at 3 elevation positions (0°, 45°, and 60° of abduction). We used a 3-factor mixed model for data analysis. After fatigue, the acromiohumeral distance increased when the upper extremity was actively positioned at 45° (Δ = 0.78 ± 0.24 mm, P = .002) or 60° (Δ = 0.58 ± 0.23 mm, P = .02) of abduction. Scapular position changed after fatigue to a more externally rotated position at 45° (Δ = 4.97° ± 1.13°, P < .001) and 60° (Δ = 4.61° ± 1.90°, P = .001) of abduction, a more upwardly rotated position at 45° (Δ = 6.10° ± 1.30°, P < .001) and 60° (Δ = 7.20° ± 1.65°, P < .001) of abduction, and a more posteriorly tilted position at 0°, 45°, and 60° of abduction (Δ = 1.98° ± 0.41°, P < .001). After a fatiguing protocol, we found changes in acromiohumeral distance and scapular position that corresponded with an impingement-sparing situation.

Effects of craniocervical flexion exercise on upper-limb postural stability during a goal-directed pointing task.

[Purpose] This study investigated the effects of craniocervical flexion exercise on upper-limb postural stability by measuring upper-limb postural tremor during a goal-directed pointing task. [Subjects and Methods] Twenty-four subjects were randomly assigned to the exercise or control group. The exercise group performed craniocervical flexion exercise four days per week for five weeks. Upper-limb postural tremor was measured by using a three-dimensional electromagnetic motion tracking system (trakSTAR™, Ascension Technology Corporation, Burlington, VT, USA) during a goal-directed pointing task. [Results] In the exercise group, the range and velocity of the trajectories of the shoulder, wrist, and finger in the lateral direction improved significantly. However, no significant changes were observed in the control group. [Conclusion] Craniocervical flexion exercise reduces the range and velocity of upper-limb postural tremor, thereby increasing postural stability.

Kinematic Differences Between Those With and Without Medial Knee Displacement During a Single-leg Squat

A greater knee valgus angle is a risk factor for lower extremity injuries. Visually observed medial knee displacement is used as a proxy for knee valgus motion during movement assessments in an attempt to identify individuals at heightened risk for injury. The validity of medial knee displacement as an indicator of valgus motion has yet to be determined during a single-leg squat. This study compared three-dimensional knee and hip angles between participants who displayed medial knee displacement (MKD group) during a single-leg squat and those who did not (control group). Participants completed five single-leg squats. An electromagnetic motion tracking system was used to quantify peak knee and hip joint angles during the descent phase of each squat. MANOVA identified a difference between the MKD and control group kinematics. ANOVA post hoc testing revealed greater knee valgus angle in the MKD (12.86 ± 5.76) compared with the control (6.08 ± 5.23) group. There were no other differences between groups. Medial knee displacement is indicative of knee valgus motion; however, it is not indicative of greater knee or hip rotation, or hip adduction. These data indicate that clinicians can accurately identify individuals with greater knee valgus angle through visually observed medial knee displacement.

Ergonomic assessment of the French and American position for laparoscopic cholecystectomy in the MIS Suite

Cholecystectomy was one of the first surgical procedures to be performed with laparoscopy in the 1980s. Currently, two operation setups generally are used to perform a laparoscopic cholecystectomy: the French and the American position. In the French position, the patient lies in the lithotomy position, whereas in the American position, the patient lies supine with the left arm in abduction. To find an ergonomic difference between the two operation setups the movements of the surgeon's vertebral column were analyzed in a crossover study. The posture of the surgeon's vertebral column was recorded intraoperatively using an electromagnetic motion-tracking system with three sensors attached to the head and to the trunk at the levels of Th1 and S1. A three-dimensional posture analysis of the cervical and thoracolumbar spine was performed to evaluate four surgeons removing a gallbladder in the French and American position. The body angles assessed were flexion/extension of the cervical and thoracolumbar spine, axial rotation of the cervical and thoracolumbar spine, lateroflexion of the cervical and thoracolumbar spine, and the orientation of the head in the sagittal plane. For each body angle, the mean, the percentage of operation time within an ergonomic acceptable range, and the relative frequencies were calculated and compared. No statistical difference was observed in the mean body angles or in the percentages of operation time within an acceptable range between the French and the American position. The relative frequencies of the body angles might indicate a trend toward slight thoracolumbar flexion in the French position. In a modern dedicated minimally invasive surgery suite, the body posture of the neck and trunk and the orientation of the head did not differ significantly between the French and American position.

Motion analysis of throwing Boccia balls in children with cerebral palsy

Boccia is a sport suitable for children with cerebral palsy (CP). Throwing Boccia balls requires upper extremity and torso coordination. This study investigated the differences between children with CP and normally developed children regarding throwing patterns of Boccia balls. Thirteen children with bilateral spastic CP and 20 normally developed children participated in this study. The tests in this study were a pediatric reach test and throwing of Boccia balls. A 3D electromagnetic motion tracking system and a force plate were synchronized to record and analyze biomechanical parameters of throwing Boccia balls. The results of the pediatric reach test for participants with CP were significantly worse than those for normally developed participants. The 2 groups of participants did not significantly differ regarding the distance between a thrown Boccia ball and a target ball (jack). Participants with CP demonstrated significantly longer movement duration, smaller amplitude of elbow movement, greater amplitudes of shoulder abduction and flexion, slower maximal velocity of torso flexion and the linear velocity of moving the wrist joint forward, faster maximal velocity of head flexion, and smaller sway ratio compared with normally developed participants when throwing Boccia balls. Participants with CP seemed to mainly use head and shoulder movements to bring the Boccia balls forward with limited torso movement. Normally developed participants brought the Boccia ball forward with faster torso and greater elbow movement while stabilizing head and shoulder movements. Nevertheless, participants with CP did not demonstrate significantly worse performance in the throwing accuracy of Boccia balls.

Measurement System for the Characterization of Micro-Manipulation Motion and Force

Vascular anastomoses are essential microsurgery tasks that demand levels of manual dexterity and precision barely tenable by even the most practiced and skilled surgeons. Teleoperated robotic micromanipulation devices have the potential to improve the availability and proficiency of procedures involving these anastomoses by enabling precise, repeatable motion while filtering out physiological noise that often hampers manual manipulation. In order to be clinically effective and commercially viable, such robotic microsurgery devices must provide significant improvements in the feasible workspace, motion bandwidth, precision, and dexterity achievable with current manual microsurgery procedures [1]. The research presented here constitutes further steps toward the empirical characterization of manual microsurgery motion and interaction forces, and the development of proper microsurgery robot performance requirements based upon that characterization [2]. We design a multimodal measurement device comprised of an electromagnetic (EM) motion tracking system, three-axis accelerometers, and a high resolution force-torque sensor to precisely record both the motions of microsurgical instruments and the forces applied at the tips of those instruments during a set of experimental anastomosis procedures. In addition to providing force data, this research aims to improve upon previous work by increasing motion tracking fidelity using sensor cross validation. The resulting data will be used inform the design of dexterous robotic micromanipulation system components, including tactile sensors, which enable safe tissue handling and suturing on the sub-millimeter scale, robotic wrists, and microgrippers.