Andrea Giovanni Cutti

A framework for the definition of standardized protocols for measuring upper-extremity kinematics

BACKGROUND Increasing interest in upper extremity biomechanics has led to closer investigations of both segment movements and detailed joint motion. Unfortunately, conceptual and practical differences in the motion analysis protocols used up to date reduce compatibility for post data and cross validation analysis and so weaken the body of knowledge. This difficulty highlights a need for standardised protocols, each addressing a set of questions of comparable content. The aim of this work is therefore to open a discussion and propose a flexible framework to support: (1) the definition of standardised protocols, (2) a standardised description of these protocols, and (3) the formulation of general recommendations. METHODS Proposal of a framework for the definition of standardized protocols. FINDINGS The framework is composed by two nested flowcharts. The first defines what a motion analysis protocol is by pointing out its role in a motion analysis study. The second flowchart describes the steps to build a protocol, which requires decisions on the joints or segments to be investigated and the description of their mechanical equivalent model, the definition of the anatomical or functional coordinate frames, the choice of marker or sensor configuration and the validity of their use, the definition of the activities to be measured and the refinements that can be applied to the final measurements. Finally, general recommendations are proposed for each of the steps based on the current literature, and open issues are highlighted for future investigation and standardisation. INTERPRETATION Standardisation of motion analysis protocols is urgent. The proposed framework can guide this process through the rationalisation of the approach.

Gait symmetry and regularity in transfemoral amputees assessed by trunk accelerations

BackgroundThe aim of this study was to evaluate a method based on a single accelerometer for the assessment of gait symmetry and regularity in subjects wearing lower limb prostheses.MethodsTen transfemoral amputees and ten healthy control subjects were studied. For the purpose of this study, subjects wore a triaxial accelerometer on their thorax, and foot insoles. Subjects were asked to walk straight ahead for 70 m at their natural speed, and at a lower and faster speed. Indices of step and stride regularity (Ad1 and Ad2, respectively) were obtained by the autocorrelation coefficients computed from the three acceleration components. Step and stride durations were calculated from the plantar pressure data and were used to compute two reference indices (SI1 and SI2) for step and stride regularity.ResultsRegression analysis showed that both Ad1 well correlates with SI1 (R2 up to 0.74), and Ad2 well correlates with SI2 (R2 up to 0.52). A ROC analysis showed that Ad1 and Ad2 has generally a good sensitivity and specificity in classifying amputees walking trial, as having a normal or a pathologic step or stride regularity as defined by means of the reference indices SI1 and SI2. In particular, the antero-posterior component of Ad1 and the vertical component of Ad2 had a sensitivity of 90.6% and 87.2%, and a specificity of 92.3% and 81.8%, respectively.ConclusionsThe use of a simple accelerometer, whose components can be analyzed by the autocorrelation function method, is adequate for the assessment of gait symmetry and regularity in transfemoral amputees.

Literature Review on Needs of Upper Limb Prosthesis Users.

The loss of one hand can significantly affect the level of autonomy and the capability of performing daily living, working and social activities. The current prosthetic solutions contribute in a poor way to overcome these problems due to limitations in the interfaces adopted for controlling the prosthesis and to the lack of force or tactile feedback, thus limiting hand grasp capabilities. This paper presents a literature review on needs analysis of upper limb prosthesis users, and points out the main critical aspects of the current prosthetic solutions, in terms of users satisfaction and activities of daily living they would like to perform with the prosthetic device. The ultimate goal is to provide design inputs in the prosthetic field and, contemporary, increase user satisfaction rates and reduce device abandonment. A list of requirements for upper limb prostheses is proposed, grounded on the performed analysis on user needs. It wants to (i) provide guidelines for improving the level of acceptability and usefulness of the prosthesis, by accounting for hand functional and technical aspects; (ii) propose a control architecture of PNS-based prosthetic systems able to satisfy the analyzed user wishes; (iii) provide hints for improving the quality of the methods (e.g., questionnaires) adopted for understanding the user satisfaction with their prostheses.

Inter-operator reliability and prediction bands of a novel protocol to measure the coordinated movements of shoulder-girdle and humerus in clinical settings

A clinical motion analysis protocol was developed to measure the coordinated movements of shoulder-girdle and humerus (girdle-humeral rhythm—GD-H-R) during humerus flexion–extension (HFE) and ab-adduction (HAA), through an optoelectronic system. In particular, the protocol describes the GD-H-R with 2 angle–angle plots for each movement: girdle elevation–depression and protraction–retraction vs HFE, and vs HAA. Each of these plots is further divided in two subplots, one for the upward and one for the downward phases of the movement. By involving 11 participants and 2 operators, we measured the protocol’s inter-operator reliability which ranged from very-good to excellent depending on the angle–angle plot (median values of the inter-operator coefficient of multiple correlation for the angle–angle plots higher than 0.94). We then computed the subjects’ average control patterns, together with statistically meaningful prediction bands. ±1SD confidence bands were also computed and their width ranged from ±0.5° to ±4.6°. Based on these results we could conclude that the method is robust and able to identify even limited differences in the GD-H-R.

The reliability of upper limb kinematics in children with hemiplegic cerebral palsy

This study describes the reliability of a protocol for upper limb three-dimensional movement analysis (UL-3DMA) in children with hemiplegic cerebral palsy (HCP). The UL-3DMA is based on the ISB-recommendations, and contains a set of functional and clinically relevant tasks. Tasks were selected to reflect the characteristic movement deficits seen in children with HCP. The protocol consists of three reach tasks (forwards, upwards, sideways); two reach-to-grasp tasks (with objects requiring different hand orientations); and three gross motor tasks. Within and between session reliability was tested in a group of 12 children with HCP, aged 6-15 years. Reliability of movement duration/speed and joint angles at endpoint was assessed with the intraclass correlation coefficient; similarity of the waveforms with the coefficient of multiple correlation. Measurement errors were calculated for all parameters. Results indicated good within and between session reliability for movement duration/speed. Trunk, scapula, shoulder, elbow and wrist angles at endpoint generally showed moderately high to very high reliability. High levels of reliability were also found for scapula, shoulder and elbow waveforms and lower levels for the wrist and trunk. Within and between session measurement errors were below 5° and 7°, respectively, for most kinematic parameters. Joint angles in the transverse plane, as well as wrist flexion generally showed higher between session errors (7-10°). This study indicates that the proposed protocol is a reliable tool to quantify upper limb movements in children with HCP, providing a sound base for its clinical application. Further research is needed to establish the discriminative ability of the UL-3DMA.

Gait analysis in children with cerebral palsy via inertial and magnetic sensors

Abstract3D kinematic measurements in children with cerebral palsy (CP) to assess gait deviations can only be performed in gait laboratories using optoelectronic systems. Alternatively, an inertial and magnetic measurement system (IMMS) can be applied for ambulatory motion-tracking. A protocol named Outwalk has recently been developed to measure the 3D kinematics during gait with IMMS. This study preliminary validated the application of IMMS, based on the Outwalk protocol, in gait analysis of six children with CP and one typically developing child. Reference joint kinematics were simultaneously obtained from a laboratory-based system and protocol. On average, the root mean square error (RMSE) of Outwalk/IMMS, compared to the reference, was less than 17° in the transversal plane, and less than 10° in the sagittal and frontal planes. The greatest differences were found in offsets in the knee and ankle rotation, and in the hip flexion. These offset differences were mainly caused by a different anatomical calibration in the protocols. When removing the offsets, RMSE was always less than 4°. Therefore, IMMS is suitable for gait analysis of major joint angles in a laboratory-free setting. Further studies should focus on improvement of anatomical calibrations of IMMS that can be performed in children with CP.

Ambulatory measurement of the scapulohumeral rhythm: Intra- and inter-operator agreement of a protocol based on inertial and magnetic sensors

To measure the scapulohumeral rhythm (SHR) in outpatient settings, the motion analysis protocol named ISEO (INAIL Shoulder and Elbow Outpatient protocol) was developed, based on inertial and magnetic sensors. To complete the sensor-to-segment calibration, ISEO requires the involvement of an operator for sensor placement and for positioning the patients arm in a predefined posture. Since this can affect the measure, this study aimed at quantifying ISEO intra- and inter-operator agreement. Forty subjects were considered, together with two operators, A and B. Three measurement sessions were completed for each subject: two by A and one by B. In each session, the humerus and scapula rotations were measured during sagittal and scapular plane elevation movements. ISEO intra- and inter-operator agreement were assessed by computing, between sessions, the: (1) similarity of the scapulohumeral patterns through the Coefficient of Multiple Correlation (CMC(2)), both considering and excluding the difference of the initial value of the scapula rotations between two sessions (inter-session offset); (2) 95% Smallest Detectable Difference (SDD(95)) in scapula range of motion. Results for CMC(2) showed that the intra- and inter-operator agreement is acceptable (median≥0.85, lower-whisker ≥ 0.75) for most of the scapula rotations, independently from the movement and the inter-session offset. The only exception is the agreement for scapula protraction-retraction and for scapula medio-lateral rotation during abduction (inter-operator), which is acceptable only if the inter-session offset is removed. SDD(95) values ranged from 4.4° to 8.6° for the inter-operator and between 4.9° and 8.5° for the intra-operator agreement. In conclusion, ISEO presents a high intra- and inter-operator agreement, particularly with the scapula inter-session offset removed.

A simple test to assess the static and dynamic accuracy of an inertial sensors system for human movement analysis

In the present study we introduced a simple test to assess the orientation error of an inertial sensors system for human movement analysis, both in static and dynamic conditions. In particular, the test was intended to quantify the sensitivity of the orientation error to direction and velocity of rotation. The test procedure was performed on a 5 MT9B sensors Xsens acquisition system, and revealed that the system orientation error, expressed by Euler angles decomposition, was sensitive both to direction and to velocity, being higher for fast movements: for mean rotation velocities of 180deg/s and 360deg/s, the worst case orientation error was 5.4deg and 11.6deg, respectively. The test can be suggested therefore as a useful tool to verify the user specific system accuracy without requiring any special equipment. In addition, the test provides further error information concerning direction and velocity of the movement which are not supplied by the producer, since they depend on the specific field of application

Recommended number of strides for automatic assessment of gait symmetry and regularity in above-knee amputees by means of accelerometry and autocorrelation analysis

BackgroundSymmetry and regularity of gait are essential outcomes of gait retraining programs, especially in lower-limb amputees. This study aims presenting an algorithm to automatically compute symmetry and regularity indices, and assessing the minimum number of strides for appropriate evaluation of gait symmetry and regularity through autocorrelation of acceleration signals.MethodsTen transfemoral amputees (AMP) and ten control subjects (CTRL) were studied. Subjects wore an accelerometer and were asked to walk for 70 m at their natural speed (twice). Reference values of step and stride regularity indices (Ad1 and Ad2) were obtained by autocorrelation analysis of the vertical and antero-posterior acceleration signals, excluding initial and final strides. The Ad1 and Ad2 coefficients were then computed at different stages by analyzing increasing portions of the signals (considering both the signals cleaned by initial and final strides, and the whole signals). At each stage, the difference between Ad1 and Ad2 values and the corresponding reference values were compared with the minimum detectable difference, MDD, of the index. If that difference was less than MDD, it was assumed that the portion of signal used in the analysis was of sufficient length to allow reliable estimation of the autocorrelation coefficient.ResultsAll Ad1 and Ad2 indices were lower in AMP than in CTRL (P < 0.0001). Excluding initial and final strides from the analysis, the minimum number of strides needed for reliable computation of step symmetry and stride regularity was about 2.2 and 3.5, respectively. Analyzing the whole signals, the minimum number of strides increased to about 15 and 20, respectively.ConclusionsWithout the need to identify and eliminate the phases of gait initiation and termination, twenty strides can provide a reasonable amount of information to reliably estimate gait regularity in transfemoral amputees.

Treatment of the Partial Hand Amputation: An Engineering Perspective

Partial hand amputation is perhaps the most frequent amputation level, worldwide. Although its annual incidence in western countries is roughly 1:18 000 inhabitants, the treatments of partial hand amputations have modestly progressed so far. We have identified three main limitation factors to this progress: 1) the wide range of anatomical and functional presentations, which makes difficult to find standardized and scalable solutions; 2) the technological complexity in replacing the motor and sensory function of a lost digit in the size of a digit; and 3) the fact that a partial hand can be functionally successful mostly when it restores a lost opposition movement, i.e., the ability to oppose the thumb against the fingers while providing enough grasping force and aperture width. This review presents an overview of the existing surgical and technological solutions for treating partial hand amputations, and is specifically targeted to (biomedical) engineers. We critically highlighted the advantages, limitations, and open challenges. Remarkably, current fitting procedures rely on manual approaches by skilled prosthetic technicians rather than on modern engineering methods. Hence, the objective of this study is to comprehensively but concisely overview the field in order to inspire engineers to develop new systems and procedures able to address current open issues.