Extracting Information about the Rotator Cuff from Magnetic Resonance Images Using Deterministic and Random Techniques

We consider some methods to extract information about the rotator cuff based on magnetic resonance images; the study aims to define an alternative method of display that might facilitate the detection of partial tears in the supraspinatus tendon. Specifically, we are going to use families of ellipsoidal triangular patches to cover the humerus head near the affected area. These patches are going to be textured and displayed with the information of the magnetic resonance images using the trilinear interpolation technique. For the generation of points to texture each patch, we propose a new method that guarantees the uniform distribution of its points using a random statistical method. Its computational cost, defined as the average computing time to generate a fixed number of points, is significantly lower as compared with deterministic and other standard statistical techniques

Development of a probabilistic population model for the prediction of subacromial geometric variability

Subacromial impingement syndrome (SAIS) is common in the shoulder and precedes several additional pathologies. SAIS occurs when the tissues interposed between the acromion process of the scapula and superior surface of the humeral head become compressed. Though SAIS is well studied, definitive mechanical cause(s) of impingement still remain elusive due to the multitude of parameters contributing to subacromial space reduction. Within this multifactorial etiology, each exhibits considerable interpersonal variability, and because of this, deterministic approaches to estimate the subacromial space size are unable to assess the distribution of risk in the population. This research used a probabilistic modelling approach to quantify the variability in both morphological and fatigue-related kinematic factors in terms of how they modulate the minimum subacromial space width. Through four distinct symbiotic stages, this work employed a combination of experimental and modelling techniques to develop a novel probabilistic model of subacromial space geometry from which SAIS risk was estimated. The first stage applied probabilistic concepts to an existing deterministic model to evaluate the sensitivity of predicted muscle forces to model parameter variation. This model demonstrated that modest variation of muscle attachment locations and a glenohumeral stability constraint resulted in considerable variability in predicted rotator cuff muscle forces, with differences up to 50% between lower and upper confidence limits. This initial study provided a conceptual framework for the probabilistic subacromial geometry model. The subsequent interdependent experimental studies (Stages II and III) were designed to acquire the necessary kinematic and morphological input distributions for the large-scale probabilistic subacromial geometry model. The first of these studies evaluated the effects of muscle fatigue and arm elevation on shoulder kinematic parameters. Specific quantities measured included: superior/inferior humeral head translation and scapular rotation, tilt and protraction/retraction, as well as the minimum subacromial space width (SAS). While significant superior humeral head translation occurred following fatigue (mean = 0.5 to 4.3mm, 0 to 120° elevation), concurrent compensatory scapular movements appeared to maintain the subacromial space size. However, the fatigue responses and elevation responses were highly variable, with half of the population demonstrating a combination of fatigue-induced changes that reduced the subacromial space. The second study quantified intrinsic static morphological characteristics of the scapula, including: acromial anterior slope, lateral acromial angle, acromial tilt, acromion index and glenoid inclination. Additionally, the interposed subacromial tissue thicknesses, specifically the supraspinatus tendon and subacromial bursa, were measured. Similar to the kinematic outcomes, each of the parameters measured in these studies showed considerable interpersonal variability. However, even the average occupation ratio (65.3 [21.6 – 108.9] %) implied a high risk of tissue compression in elevated arm postures. The distributions of experimentally measured kinematic and morphological characteristics were used as inputs into a three-dimensional probabilistic subacromial geometry model which subsequently generated a distribution of SAS (Stage IV). Additionally, relative importance factors were obtained from the probabilistic modeling approach, which established which parameters (morphological, kinematic) contributed more to the variability in SAIS risk. Overall, the probability of tissue compression (a mechanical indicator of SAIS risk) increased markedly with elevation, from <5% at initial elevation, to ~50% at mid-elevation to 75% at maximal elevation. The considerable variability present in each of the measured characteristics in addition to the modelled output suggested a highly differential risk of fatigue-related SAIS across the population, with glenoid inclination identified as the most important factor in modulating the size of the subacromial space. At the average population level, the predominant recommendation elucidated from this work is avoidance of overhead exertions, which would contribute to rotator cuff tissue damage, facilitated through repetitive tissue compression at elevation angles ≥60°. Additionally, the presence of fatigue-induced superior humeral head translation, despite the maintenance of the subacromial space size, may increase the likelihood of several other degenerative pathologies (glenoid degeneration, osteophyte formation, glenohumeral instability). Thus, rotator cuff strengthening programs, to maintain a stable glenohumeral relationship, are suggested for those exposed to repetitive elevation or upper extremity fatiguing activities, particularly if diagnosed with scapular dyskinesis. Lastly, the outcomes of this research highlight the utility of probabilistic modelling approaches for characterizing interpersonal variability and subsequently estimating the distribution of musculoskeletal injury risk in a population

Comparison of peripheral quantitative computed tomography and magnetic resonance imaging for tissue characterisation in the gastrocnemius muscle

of the calf muscles. Magnetic resonance imaging (MRI) and ultrasound (US) are the medical imaging modalities that are usually used to assess such injuries. Texture analysis is a digital image processing technique that quantifies the relationship between pixel intensities (grey levels) and pixel positions. Texture can reveal valuable information that cannot be perceived by the naked eye. Dedicated image processing software is required to extract texture parameters. Texture analysis has been implemented for medical imaging modalities such as MRI, US and computed tomography (CT) for the evaluation sports muscle injury. Peripheral quantitative tomography (pQCT) is an adaptation of conventional CT. In this project, texture analysis was implemented on MRI and pQCT images of the gastrocnemius muscle (GM). MRI is an expensive technique that requires specialised facilities. Conversely, pQCT utilises a small-bore, low-dose X-ray scanner, which is portable and less costly than MRI. It has traditionally been used mainly for bone analysis. The aim of this study was to assess the suitability of pQCT for GM tissue characterisation using texture analysis compared with MRI. The study is novel in that it is the first to apply texture analysis to GM images using pQCT Texture analysis was done on image data acquired from MRI (GE, 1.5T) and pQCT (Stratec XCT 2000) in a group of healthy human subjects and an injured subject. A water phantom was also scanned with pQCT. An existing standard imaging protocol was observed for MRI acquisition, while pQCT image acquisition parameters were explored and optimised to yield a standard protocol. The pQCT scanner was shown to be capable of acquiring calf muscle images and distinguishing calf muscle boundaries. Texture parameters (grey level, variance, skewness, kurtosis, co-occurrence matrix, run length matrix, gradient, autoregressive (AR) model and wavelet transform) were extracted from the acquired images. The repeatability of these quantities for pQCT in a healthy human subject and a water phantom was assessed by calculating the coefficient of variation (%CV). The effect of pQCT parameters (scan speed and pixel size) was tested using multiple variate II analysis of variance (MANOVA). The effect of region of interest (ROI) area and anatomical position were evaluated using simple linear regression. The t-test was used to compare the mean values of the texture features in the right and left leg for both MRI and pQCT in a group of healthy human subjects. Neither MRI nor pQCT showed significant differences between the two legs for any of the texture features. In addition, there was no significant difference between the two modalities for the AR model and wavelet transform texture parameters. Reference ranges for the medial head of the GM were defined for both modalities. A study of a single injured subject revealed that the values of the AR model texture parameter fell outside the reference ranges for both MRI and pQCT, and so the AR model was identified as the most sensitive texture parameter for distinguishing injured from uninjured GM. The principal conclusion from this work is that pQCT has the potential to be used for imaging the gastrocnemius muscle and that GM images from both MRI and pQCT scanners can be objectively characterised by texture analysis. In addition, the autoregressive model texture parameter may be the most appropriate for muscle characterisation

Development of a Probabilistic Chimpanzee Glenohumeral Model: Implications for Human Function

Modern human shoulder function is affected by the evolutionary adaptations that have occurred to ensure survival and prosperity of the species. Robust examination of behavioral shoulder performance and injury risk can be holistically improved through an interdisciplinary approach that integrates anthropology and biomechanics. Anthropological research methods have attempted to resolve gaps in human shoulder evolution, while biomechanics research has attempted to explain the musculoskeletal function of the modern human shoulder. Coordination of these two fields can allow different perspectives to contribute to a more complete interpretation of, not only how the modern human shoulder is susceptible to specific injuries, but also why. How the modern human shoulder arose from a, likely, weight-bearing, arboreal past to its modern form, and what this has meant for modern behaviors, is not well understood. Despite a weight-bearing, locomotor ancestral usage, the modern human upper extremity is highly fatigable in repetitive, low to moderate force tasks, such as overhead reaching. The closest living human relative, modern chimpanzees, has retained an arboreal, locomotor upper extremity. Interdisciplinary comparative research on humans and chimpanzees could lead to greater insight on modern human shoulder function. The purpose of this research was to explore the modern human capacity for ancestral, brachiating behaviors and resultant injury mechanisms through comparative experimental, computational modeling and probabilistic modeling approaches with chimpanzees. The first study experimentally explored the modern human ability to perform a horizontal bimanual arm-suspensory climbing task. EMG of 12 upper extremity muscles and motion capture of the arm and thorax were monitored in experienced and inexperienced climbers. Results were also compared to previously published or collected data on chimpanzees performing an analogous task. While all human climbers used a high proportion of their muscular reserve to perform the task, experienced climbers had moderately reduced muscle activity in most muscles, particularly during phasic shifts of the climb cycle and moderately more efficient kinematics. Climbing kinematics and muscle activity were very similar between humans and chimpanzees. However, chimpanzees appear to have a different utility of the posterior deltoid, suggesting an influence of their habitual arboreal behaviors. The second and third studies describe the development of a deterministic chimpanzee musculoskeletal glenohumeral model. Study 2 developed geometric parameters of chimpanzee shoulder rhythm and glenoid stability ratios for the construction of a chimpanzee glenohumeral model. The chimpanzee glenohumeral model of Study 3 was designed to parallel an existing human glenohumeral model, enabling comparative analyses. The chimpanzee glenohumeral model consists of three modules – an external torque module, musculoskeletal geometric module, and an internal muscle force prediction module. Together, these modules use postural kinematics, subject specific anthropometrics and hand forces to estimate joint reaction forces and moments, subacromial space dimensions, and muscle and tissue forces. Using static postural data from Study 1, predicted muscle forces and subacromial space were compared between chimpanzees and humans during an overhead, weight-bearing climbing task. Compared to chimpanzees, the human model predicted a 2mm narrower subacromial space, deltoid muscle forces that were often double those of chimpanzees and a strong reliance on infraspinatus and teres minor (60-100% maximal force) over other rotator cuff muscles. Finally, the deterministic chimpanzee and human glenohumeral models were expanded in Study 4 to a probabilistic analysis of rotator cuff function between species. Using probabilistic software and the same postural climbing inputs, both models had anthropologically relevant musculoskeletal features perturbed in a series of Monte Carlo simulations – muscle origins and insertions, glenoid inclination and glenoid stability – to determine if rotator cuff muscle force prediction distributions would converge between species. Human rotator cuff muscle behavior did not converge with chimpanzees using probabilistic simulation. The human model continued to predict strong dependence on infraspinatus and teres minor, with 99% confidence intervals of [0-100]% maximal force, over supraspinatus and subscapularis, with confidence intervals of [0-5]% maximal force. Chimpanzee rotator cuff confidence intervals were typically between [0-40]% maximal force, with median force for all four rotator cuff muscles typically 5-20% maximal force. While perturbation of muscle origins and insertions had the greatest effect on muscle force output distributions, no musculoskeletal variation notably modified human climbing performance. Structural musculoskeletal differences between species dictated differences in glenohumeral function. The results from all studies indicate susceptibility for the fatigue-induced initiation of subacromial impingement syndrome and rotator cuff pathology in modern humans during overhead and repetitive tasks. Lower muscle absolute PCSA in humans, combined with a laterally oriented glenohumeral joint and laterally projecting acromion reduced the capacity for overhead postures and weight-bearing postures. These evolutionary differences may have been vestigial consequences, concurrent with necessary adaptions for important, evolutionary human-centric behaviors such as throwing. However, they have influenced the high rates of rotator cuff pathology in humans compared to closely related primates. The present work represents an important first step toward a broad scope of future research. Interdisciplinary computational modeling offers an evolving and improving alternative to traditional methods to study human evolution and function. Computational and probabilistic simulations can be expanded to numerous other biomechanical and evolutionary queries. The results of this thesis are a promising initial step to examining the evolutionary structural connection to biomechanical human function through comparative computational modeling

Applications of EMG in Clinical and Sports Medicine

This second of two volumes on EMG (Electromyography) covers a wide range of clinical applications, as a complement to the methods discussed in volume 1. Topics range from gait and vibration analysis, through posture and falls prevention, to biofeedback in the treatment of neurologic swallowing impairment. The volume includes sections on back care, sports and performance medicine, gynecology/urology and orofacial function. Authors describe the procedures for their experimental studies with detailed and clear illustrations and references to the literature. The limitations of SEMG measures and methods for careful analysis are discussed. This broad compilation of articles discussing the use of EMG in both clinical and research applications demonstrates the utility of the method as a tool in a wide variety of disciplines and clinical fields

Excellentia Eminentia Effectio

"In these pages you will learn about the fascinating research endeavors that each of our faculty members is undertaking. We have divided their research into the broad categories of health, sustainability, information, and systems. While we recognize the imperfect nature of categorizing research that, by its very nature may be interdisciplinary or transdisciplinary, we nonetheless believe it will be helpful as a way to see the depth and breadth of our research endeavors within each grouping. As you read the profiles on these pages, I know you will begin to appreciate that, taken as a whole, the research spectrum at Columbia Engineering is exceptional and that, as our professors go about their work, they are at the cusp of making breakthroughs that will have a major impact on the way we live our lives today and tomorrow.

Wearable and BAN Sensors for Physical Rehabilitation and eHealth Architectures

The demographic shift of the population towards an increase in the number of elderly citizens, together with the sedentary lifestyle we are adopting, is reflected in the increasingly debilitated physical health of the population. The resulting physical impairments require rehabilitation therapies which may be assisted by the use of wearable sensors or body area network sensors (BANs). The use of novel technology for medical therapies can also contribute to reducing the costs in healthcare systems and decrease patient overflow in medical centers. Sensors are the primary enablers of any wearable medical device, with a central role in eHealth architectures. The accuracy of the acquired data depends on the sensors; hence, when considering wearable and BAN sensing integration, they must be proven to be accurate and reliable solutions. This book is a collection of works focusing on the current state-of-the-art of BANs and wearable sensing devices for physical rehabilitation of impaired or debilitated citizens. The manuscripts that compose this book report on the advances in the research related to different sensing technologies (optical or electronic) and body area network sensors (BANs), their design and implementation, advanced signal processing techniques, and the application of these technologies in areas such as physical rehabilitation, robotics, medical diagnostics, and therapy