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Louis A. DiBerardino III, Chantal A. Ragetly, Sungjin Hong, Dominique J. Griffon and Elizabeth T. Hsiao-Wecksler

The regions of deviation method has been proposed as a technique for identifying regions of the gait cycle where joint motion deviates from normal (Shorter et al., 2008). The original statistical analysis distinguished only peak values during stance and swing. In the current article, we extend the approach by examining deviations from normal throughout the entire gait cycle using pointwise t tests. These methods were demonstrated on hind-limb joint angles of 21 Labrador Retrievers without and with cranial cruciate ligament disease. Results were compared with peak difference analysis previously performed on these subjects. All points in the gait cycle where symmetry deviations were significantly affected by cranial cruciate ligament disease (via pointwise t tests) were defined as regions of deviation from symmetry. Discriminant function analysis was used to consider single subjects and validate that these regions were truly areas of difference between groups. Regions of deviation encompassed previously determined significant peak differences, while extending analysis to additional areas of asymmetry. Discriminant function analysis suggested that the region of deviation method is a viable approach for distinguishing motion pattern differences. This enhanced method may help researchers better understand the mechanisms behind lameness and compensation.

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Francisco Javier Alonso, Publio Pintado and José María Del Castillo

The use of the Hodrick-Prescott (HP) filter is presented as an alternative to the traditional digital filtering and spline smoothing methods currently used in biomechanics. In econometrics, HP filtering is a standard tool used to decompose a macroeconomic time series into a nonstationary trend component and a stationary residual component. The use of the HP filter in the present work is based on reasonable assumptions about the jerk and noise components of the raw displacement signal. Its applicability was tested on 4 kinematic signals with different characteristics. Two are well known signals taken from the literature on biomechanical signal filtering, and the other two were acquired with our own motion capture system. The criterion for the selection of cutoff frequency was based on the power spectral density of the raw displacement signals. The results showed the technique to be well suited to filtering biomechanical displacement signals in order to obtain accurate higher derivatives in a simple and systematic way. Namely, the HP filter and the generalized cross-validated quintic spline (GCVSPL) produce similar RMS errors on the first (0.1063 vs. 0.1024 m/s2) and second (23.76 vs. 23.24 rad/s2) signals. The HP filter performs slightly better than GCVSPL on the third (0.209 vs. 0.236 m/s2) and fourth (1.596 vs. 2.315 m/s2) signals.

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Andre Filipe Santos-Magalhaes and Karen Hambly

Context:

The assessment of physical activity and return to sport and exercise activities is an important component in the overall evaluation of outcome after autologous cartilage implantation (ACI).

Objective:

To identify the patient-report instruments that are commonly used in the evaluation of physical activity and return to sport after ACI and provide a critical analysis of these instruments from a rehabilitative perspective.

Evidence Acquisition:

A computerized search was performed in January 2013 and repeated in March 2013. Criteria for inclusion required that studies (1) be written in English and published between 1994 and 2013; (2) be clinical studies where knee ACI cartilage repair was the primary treatment, or comparison studies between ACI and other techniques or between different ACI generations; (3) report postoperative physical activity and sport participation outcomes results, and (4) have evidence level of I–III.

Evidence Synthesis:

Twenty-six studies fulfilled the inclusion criteria. Three physical activity scales were identified: the Tegner Activity Scale, Modified Baecke Questionnaire, and Activity Rating Scale. Five knee-specific instruments were identified: the Lysholm Knee Function Scale, International Knee Documentation Committee Score Subjective Form, Knee Injury and Osteoarthritis Outcome Score, Modified Cincinnati Knee Score, and Stanmore-Bentley Functional Score.

Conclusions:

Considerable heterogeneity exists in the reporting of physical activity and sports participation after ACI. Current instruments do not fulfill the rehabilitative needs in the evaluation of physical activity and sports participation. The validated instruments fail in the assessment of frequency, intensity, and duration of sports participation.

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Jeremy R. Dicus and Jeff G. Seegmiller

Few ankle inversion studies have taken anticipation bias into account or collected data with an experimental design that mimics actual injury mechanisms. Twenty-three participants performed randomized single-leg vertical drop landings from 20 cm. Subjects were blinded to the landing surface (a flat force plate or 30° inversion wedge on the force plate). After each trial, participants reported whether they anticipated the landing surface. Participant responses were validated with EMG data. The protocol was repeated until four anticipated and four unanticipated landings onto the inversion wedge were recorded. Results revealed a significant main effect for landing condition. Normalized vertical ground reaction force (% body weights), maximum ankle inversion (degrees), inversion velocity (degrees/second), and time from contact to peak muscle activation (seconds) were significantly greater in unanticipated landings, and the time from peak muscle activation to maximum VGRF (second) was shorter. Unanticipated landings presented different muscle activation patterns than landings onto anticipated surfaces, which calls into question the usefulness of clinical studies that have not controlled for anticipation bias.

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Andreas Krüger and Jürgen Edelmann-Nusser

This study aims at determining the accuracy of a full body inertial measurement system in a real skiing environment in comparison with an optical video based system. Recent studies have shown the use of inertial measurement systems for the determination of kinematical parameters in alpine skiing. However, a quantitative validation of a full body inertial measurement system for the application in alpine skiing is so far not available. For the purpose of this study, a skier performed a test-run equipped with a full body inertial measurement system in combination with a DGPS. In addition, one turn of the test-run was analyzed by an optical video based system. With respect to the analyzed angles, a maximum mean difference of 4.9° was measured. No differences in the measured angles between the inertial measurement system and the combined usage with a DGPS were found. Concerning the determination of the skier’s trajectory, an additional system (e.g., DGPS) must be used. As opposed to optical methods, the main advantages of the inertial measurement system are the determination of kinematical parameters without the limitation of restricted capture volume, and small time costs for the measurement preparation and data analysis.

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Sean P. Flanagan and George J. Salem

In the analysis of human movement, researchers often sum individual joint kinetics to obtain a single measure of lower extremity function. The extent to which these summed measures relate to the mechanical objectives of the task has not been formally validated. The criterion validity of these measures was established with comparisons to the mechanical objective of two multiple-joint tasks. For the Work task 18 participants performed a loaded barbell squat using 4 resistances while instrumented for biomechanical analysis. For the Power they performed 2 predetermined amounts of work at both self-selected and fast speeds. Using inverse dynamics techniques, the peak net joint moment (PM) was calculated bilaterally in the sagittal plane at the ankle, knee, and hip and was summed into a single measure. This measure was correlated with the task objectives using simple linear regression. Similar procedures were used for the average net joint moment (AM), peak (PP), and average (AP) net joint moment power, and the net joint moment impulse (IM) and work (IP). For the Work task all 6 measures were significantly correlated with the task objective, but only AM, PM, and IP had correlation coefficients above 0.90. For the Power task, IM was not significantly correlated with the task objective, and only AP had a correlation coefficient above 0.90. These findings indicate that the validity of summing individual kinetic measures depends on both the measure chosen and the mechanical objective of the task.

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Jaclyn B. Caccese, Thomas A. Buckley and Thomas W. Kaminski

The Balance Error Scoring System (BESS) is often used for sport-related concussion balance assessment. However, moderate intratester and intertester reliability may cause low initial sensitivity, suggesting that a more objective balance assessment method is needed. The MobileMat BESS was designed for objective BESS scoring, but the outcome measures must be validated with reliable balance measures. Thus, the purpose of this investigation was to compare MobileMat BESS scores to linear and nonlinear measures of balance. Eighty-eight healthy collegiate student-athletes (age: 20.0 ± 1.4 y, height: 177.7 ± 10.7 cm, mass: 74.8 ± 13.7 kg) completed the MobileMat BESS. MobileMat BESS scores were compared with 95% area, sway velocity, approximate entropy, and sample entropy. MobileMat BESS scores were significantly correlated with 95% area for single-leg (r = .332) and tandem firm (r = .474), and double-leg foam (r = .660); and with sway velocity for single-leg (r = .406) and tandem firm (r = .601), and double-leg (r = .575) and single-leg foam (r = .434). MobileMat BESS scores were not correlated with approximate or sample entropy. MobileMat BESS scores were low to moderately correlated with linear measures, suggesting the ability to identify changes in the center of mass–center of pressure relationship, but not higher-order processing associated with nonlinear measures. These results suggest that the MobileMat BESS may be a clinically-useful tool that provides objective linear balance measures.

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Laura Seidl, Danijel Tosovic and J. Mark Brown

Whole muscle mechanomyography (MMG) has gained considerable interest in recent years for its ability to noninvasively determine muscle contractile properties (ie, contraction time [Tc], half-relaxation time [1/2Tr], and maximal displacement [Dmax)]). The aim of this study was to evaluate the test-retest reliability of two fairly novel MMG transducers: a laser-displacement sensor (LDS) and contact-displacement sensor (CDS). MMG was conducted on the rectus femoris muscle of 30 healthy individuals on 4 separate occasions. Test-retest reliability was quantified using intraclass correlation coefficients (ICCs). Both sensors were reliable for time-derived parameters Tc (ICCs, 0.85–0.88) and 1/2Tr (0.77–0.89), with Dmax identified as the most reproducible parameter (0.89–0.94). The 2 sensors produced similar Tc and Dmax measures, although significant (P < .05) systematic bias was identified with the CDS recording higher mean values, on average. However, these differences may not be considered clinically significant. The wide limits of agreement identified between 1/2Tr measures (–19.0 ms and 25.2 ms) are considered unreliable from a clinical perspective. Overall, MMG demonstrated good-to-excellent reliability for the assessment of muscle contractile properties with no significant differences identified between sessions, thus further validating its applicability as a noninvasive measure of muscle contractile properties.

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Aaron Chin, David Lloyd, Jacqueline Alderson, Bruce Elliott and Peter Mills

The predominance of upper-limb elbow models have been based on earlier lower-limb motion analysis models. We developed and validated a functionally based 2 degree-of-freedom upper-limb model to measure rotations of the forearm using a marker-based approach. Data were collected from humans and a mechanical arm with known axes and ranges of angular motion in 3 planes. This upper-limb model was compared with an anatomically based model following the proposed ISB standardization. Location of the axes of rotation relative to each other was determined in vivo. Data indicated that the functional model was not influenced by cross-talk from adduction-abduction, accurately measuring flexion-extension and pronation-supination. The functional flexion-extension axis in vivo is angled at 6.6° to the anatomical line defined from the humeral medial to lateral epicondyles. The pronation-supination axis intersected the anatomically defined flexion-extension axis at 88.1°. Influence of cross-talk on flexion-extension kinematics in the anatomical model was indicated by strong correlation between flexion-extension and adduction-abduction angles for tasks performed by the subjects. The proposed functional model eliminated cross-talk by sharing a common flexion axis between the humerus and forearm. In doing so, errors due to misalignment of axes are minimized providing greater accuracy in kinematic data.

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Steven Rowson, Jonathan G. Beckwith, Jeffrey J. Chu, Daniel S. Leonard, Richard M. Greenwald and Stefan M. Duma

The high incidence rate of concussions in football provides a unique opportunity to collect biomechanical data to characterize mild traumatic brain injury. The goal of this study was to validate a six degree of freedom (6DOF) measurement device with 12 single-axis accelerometers that uses a novel algorithm to compute linear and angular head accelerations for each axis of the head. The 6DOF device can be integrated into existing football helmets and is capable of wireless data transmission. A football helmet equipped with the 6DOF device was fitted to a Hybrid III head instrumented with a 9 accelerometer array. The helmet was impacted using a pneumatic linear impactor. Hybrid III head accelerations were compared with that of the 6DOF device. For all impacts, peak Hybrid III head accelerations ranged from 24 g to 176 g and 1,506 rad/s2 to 14,431 rad/s2. Average errors for peak linear and angular head acceleration were 1% ± 18% and 3% ± 24%, respectively. The average RMS error of the temporal response for each impact was 12.5 g and 907 rad/s2.