Detection of the movement of the humerus during daily activity

A new ambulatory technique for qualitative and quantitative movement analysis of the humerus is presented. 3D gyroscopes attached on the humerus were used to recognize the movement of the arm and to classify it as flexion, abduction and internal/external rotations. The method was first validated in a laboratory setting and then tested on 31 healthy volunteer subjects while carrying the ambulatory system during 8h of their daily life. For each recording, the periods of sitting, standing and walking during daily activity were detected using an inertial sensor attached on the chest. During each period of daily activity the type of arm movement (flexion, abduction, internal/external rotation) its velocity and frequency (number of movement/hour) were estimated. The results showed that during the whole daily activity and for each activity (i.e. walking, sitting and walking) the frequency of internal/external rotation was significantly higher while the frequency of abduction was the lowest (P<0.009). In spite of higher number of flexion, abduction and internal/external rotation in the dominant arm, we have not observed in our population a significant difference with the non-dominant arm, implying that in healthy subjects the arm dominance does not lie considerably on the number of movements. As expected, the frequency of the movement increased from sitting to standing and from standing to walking, while we provide a quantitative value of this change during daily activity. This study provides preliminary evidence that this system is a useful tool for objectively assessing upper-limb activity during daily activity. The results obtained with the healthy population could be used as control data to evaluate arm movement of patients with shoulder diseases during daily activit

A framework for forward-dynamics simulation of the human shoulder

A vast majority of the available biomechanical models of the human shoulder has been developed based on inverse dynamics, e.g. [1,2]. This imposes a number of limitations on their application. For instance, the glenohumeral joint is approximated as an ideal joint in an inverse-dynamics simulation. Therefore, the models fall short to predict the joint translations [3]. The different approaches developed to overcome the recurrent limitations of the models can be broadly divided in two categories. The first category tries to tailor an available inverse-dynamics model to a specific application, e.g. [3,4]. The second category aims to develop a framework allowing forward-dynamics simulation, e.g. [5,6]. Indeed, few studies have developed forward-dynamics simulations of the human body. In [5], dynamic optimization was used to develop a forward-dynamics model of the lower extremity. Dynamic optimization typically demands many times integration of the equations of motion. Given the computational expense incurred by the integrations, the method is impractical for common applications. In this study, a framework for forward-dynamics simulation of the human shoulder is developed. In contrast with the dynamic optimization, the developed framework requires a single integration of the system equations. It is based on a joint application of a biomechanical model of the shoulder and a controller. The controller defines the muscle forces allowing the model to be simulated in forward dynamics. Different control scenarios are considered to investigate the model convergence in terms of accuracy and computational effort

A semi-automated quantitative CT method for measuring rotator cuff muscle degeneration in shoulders with primary osteoarthritis

Background: Rotator cuff muscle degeneration is an important parameter to consider when planning shoulder arthroplasty. Hypothesis: We hypothesized that rotator cuff muscle degeneration is correlated with scapulohumeral subluxation in patients planned for anatomical total shoulder arthroplasty (TSA). Materials and methods: We developed a semi-automated quantitative CT method to measure rotator cuff muscle degeneration, and retrospectively analyzed 107 preoperative shoulder CT scans of patients with primary osteoarthritis. On a standardized sagittal-oblique CT slice perpendicular to the scapular axis, two observers measured the cross-sectional areas of residual rotator cuff muscle tissues, normalized by the estimated area of healthy muscles. Muscle degeneration was quantified in a semi-automated manner, and divided into atrophy and fatty infiltration. Scapulohumeral subluxation was determined in 3D as the distance between the humeral head center and the glenoid surface center, projected on the same CT slice, and normalized by the humeral head radius. We tested all potential correlations between muscle degeneration and scapulohumeral subluxation. Results: Muscle degeneration, primarily due to atrophy, predominated in the supraspinatus; it varied from 0.8% to 88.8%. Scapulohumeral subluxation varied from 2.5% to 72.9%, and was mainly in a posterior and postero-superior orientation. There was a significant but weak correlation between the amount of sublux- ation and both supraspinatus (R = 0.207, P = 0.032) and infraspinatus (R = 0.225, P = 0.020) degeneration. Inter- and intra-observer reproducibility of muscle degeneration measurements were both excellent (ICCs range = 0.955–0.987 and 0.971–0.988, respectively). Conclusion: This new semi-automated CT method allows to quantitatively and reproducibly measure rotator cuff muscle degeneration in shoulders with primary osteoarthritis. Muscle degeneration is weakly correlated with scapulohumeral subluxation in patients planned for anatomical TSA

Active Stability of Glenohumeral Joint Diminishes during the End-range Motions

The lack of congruence between the involved articular surfaces causes the inherent instability of the glenohumeral joint. This joint is therefore the most commonly dislocated joint in the human body. Anterior instability accounts for over 90% of the shoulder dislocations. The reason of this almost unidirectional dislocation remains unknown. Few studies have quantitatively discussed the joint stability utilizing musculoskeletal models. Other studies mainly utilized either purely clinical or cadaveric approaches to address the joint stability. The aim of this study is to identify the key factors contributing to anterior instability through a quantitative analysis of the shoulder's dynamic stabilizers

Heightened clinical utility of smartphone versus body-worn inertial system for shoulder function B-B score

Background The B-B Score is a straightforward kinematic shoulder function score including only two movements (hand to the Back + lift hand as to change a Bulb) that demonstrated sound measurement properties for patients for various shoulder pathologies. However, the B-B Score results using a smartphone or a reference system have not yet been compared. Provided that the measurement properties are comparable, the use of a smartphone would offer substantial practical advantages. This study investigated the concurrent validity of a smartphone and a reference inertial system for the measurement of the kinematic shoulder function B-B Score. Methods Sixty-five patients with shoulder conditions (with rotator cuff conditions, adhesive capsulitis and proximal humerus fracture) and 20 healthy participants were evaluated using a smartphone and a reference inertial system. Measurements were performed twice, alternating between two evaluators. The B-B Score differences between groups, differences between devices, relationship between devices, intra- and inter-evaluator reproducibility were analysed. Results The smartphone mean scores (SD) were 94.1 (11.1) for controls and 54.1 (18.3) for patients (P &lt; 0.01). The difference between devices was non-significant for the control (P = 0.16) and the patient group (P = 0.81). The analysis of the relationship between devices showed 0.97 ICC, -0.6 bias and -13.2 to 12.0 limits of agreement (LOA). The smartphone intra-evaluator ICC was 0.92, the bias 1.5 and the LOA -17.4 to 20.3. The smartphone inter-evaluator ICC was 0.92, the bias 1.5 and the LOA -16.9 to 20.0. Conclusions The B-B Score results measured with a smartphone were comparable to those of an inertial system. While single measurements diverged in some cases, the intra- and inter-evaluator reproducibility was excellent and was equivalent between devices. The B-B score measured with a smartphone is straightforward and as efficient as a reference inertial system measurement.sch_phy12pub4727pub