Biomedical subjects

Richard E Hughes

Publications and source records attributed to Richard E Hughes.

16 recordsLinked to original sources

PubMed2006

Electromyographic analysis of physical examination tests for type II superior labrum anterior-posterior lesions.

Physical examination tests that place tension on the long head of the biceps may best reproduce symptoms in patients with type II superior labrum anterior-posterior (SLAP) lesions. The objective of this study is to compare the normalized electromyographic signal of the long head of the biceps for SLAP lesion physical examination tests. The active compression test, anterior-superior SLAP test, biceps load test II, biceps tension test, and pain provocation test were performed on 13 subjects while biceps electromyographic data were recorded. The active compression test and biceps tension test had significantly higher electromyographic signals than the other tests. We found no significant differences when comparing forearm supination and pronation within individual tests. Because the active compression and biceps tension tests maximize muscle activation on the long head of the biceps, they may be the best physical examination tests by which to identify type II SLAP lesions.

Adult↗

PubMed2006

Variability in isometric force and moment generating capacity of glenohumeral external rotator muscles.

BACKGROUND: Muscles which cause glenohumeral external rotation possess varying ability for generating force and moment due to differences in muscle architecture, moment arm, and the interaction of these two factors. This study's purpose was to determine a complete dataset of muscle-tendon parameters for predicting the moment generating capacity and force-length dependence for external rotation of infraspinatus, supraspinatus and teres minor muscles. METHODS: Muscle fascicle length, sarcomere length, pennation angle, and muscle volume were measured for sub-regions of infraspinatus and supraspinatus, and teres minor from 10 glenohumeral specimens. Tendon excursion was measured for glenohumeral rotation. From these parameter measurements, optimal fascicle length, physiological cross-sectional area, muscle force-length dependence, and maximum isometric moment generating capacity were calculated. FINDINGS: Substantial differences were found for optimal muscle length, physiologic cross-sectional area, and tendon length for the 10 specimens of this study. Muscle sub-region had a significant effect on the force-length relationship for infraspinatus (P<0.001), but was not significant for supraspinatus (P=0.49). For infraspinatus and supraspinatus, maximum isometric rotation moment capacity was greater at 10 degrees versus 60 degrees abduction (P<0.001). Maximum isometric rotation moment capacity for the teres minor was greater at 10 degrees versus 60 degrees abduction (P<0.01). Sub-regions demonstrated significant differences in isometric moment capacity (P<0.001). INTERPRETATION: Functional capabilities of these muscles depend on muscle architecture and moment arm as well as their combined effects. The results allow for development of stochastic and deterministic models of glenohumeral external rotation strength which can be used for prediction of muscle forces and joint moments.

Anatomy, Cross-Sectional↗

PubMed2006

A probabilistic model of glenohumeral external rotation strength for healthy normals and rotator cuff tear cases.

The reigning paradigm of musculoskeletal modeling is to construct deterministic models from parameters of an "average" subject and make predictions for muscle forces and joint torques with this model. This approach is limited because it does not perform well for outliers, and it does not model the effects of population parameter variability. The purpose of this study was to simulate variability in musculoskeletal parameters on glenohumeral external rotation strength in healthy normals, and in rotator cuff tear case using a Monte Carlo model. The goal was to determine if variability in musculoskeletal parameters could quantifiably explain variability in glenohumeral external rotation strength. Multivariate Gamma distributions for musculoskeletal architecture and moment arm were constructed from empirical data. Gamma distributions of measured joint strength were constructed. Parameters were sampled from the distributions and input to the model to predict muscle forces and joint torques. The model predicted measured joint torques for healthy normals, subjects with supraspinatus tears, and subjects with infraspinatus-supraspinatus tears with small error. Muscle forces for the three conditions were predicted and compared. Variability in measured torques can be explained by differences in parameter variability.

Computer Simulation↗

PubMed2006

Variation in external rotation moment arms among subregions of supraspinatus, infraspinatus, and teres minor muscles.

A rotator cuff tear causes morphologic changes in rotator cuff muscles and tendons and reduced shoulder strength. The mechanisms by which these changes affect joint strength are not understood. This study's purpose was to empirically determine rotation moment arms for subregions of supraspinatus, infraspinatus, and for teres minor, and to test the hypothesis that subregions of the cuff tendons increase their effective moment arms through connections to other subregions. Tendon excursions were measured for full ranges of rotation on 10 independent glenohumeral specimens with the humerus abducted in the scapular plane at 10 and 60 degrees . Supraspinatus and infraspinatus tendons were divided into equal width subregions. Two conditions were tested: tendon divided to the musculotendinous junction, and tendon divided to the insertion on the humerus. Moment arms were determined from tendon excursion via the principle of virtual work. Moment arms for the infraspinatus (p < 0.001) and supraspinatus (p < 0.001) were significantly greater when the tendon was only divided to the musculotendinous junction versus division to the humeral head. Moment arms across subregions of infraspinatus (p < 0.001) and supraspinatus (p < 0.001) were significantly different. A difference in teres minor moment arm was not found for the two cuff tendon conditions. Moment arm differences between muscle subregions and for tendon division conditions have clinical implications. Interaction between cuff regions could explain why some subjects retain strength after a small cuff tear. This finding helps explain why a partial cuff repair may be beneficial when a complete repair is not possible. Data presented here can help differentiate between cuff tear cases that would benefit from cuff repair and cases for which cuff repair might not be as favorable.

Biomechanical Phenomena↗

PubMed2006

Using support vector machines to optimally classify rotator cuff strength data and quantify post-operative strength in rotator cuff tear patients.

Shoulder strength data are important for post-operative assessment of shoulder function and have been used in diagnosis of rotator cuff pathology. Support vector machines (SVM) employ complex analysis techniques to solve classification and regression problems. A SVM, a machine learning technique, can be used for analysis and classification of shoulder strength data. The goals of this study were to determine the diagnostic competency of SVM based on shoulder strength data and to apply SVM analysis in efforts to derive a single representative shoulder strength score. Data were taken from fourteen isometric shoulder strength measurements of each shoulder (involved and uninvolved) in 45 rotator cuff tear patients. SVM diagnostic proficiency was found to be comparable to reported ultrasound values. Improvement of shoulder function was accurately represented by a single score in pairwise comparison of the pre-operative and the 12 month post-operative group (P < 0.004). Thus, the SVM-based score may be a promising metric for summarizing rotator cuff strength data.

Artificial Intelligence↗

PubMed2005

The effect of wearing a wrist splint on shoulder kinematics during object manipulation.

OBJECTIVES: To test the hypotheses that (1) wearing a flexible wrist splint while taking an object from a box increases known postural risk factors for shoulder disorders and (2) that the height of the front of the box modulates the effect on shoulder kinematics of wearing a wrist splint. DESIGN: A controlled laboratory experiment with 2 factors (splint wearing, box height). SETTING: Human performance laboratory. PARTICIPANTS: Ten consecutive healthy volunteers (5 men, 5 women; age range, 19-32 y). INTERVENTIONS: Experimental manipulation of wrist immobilization and box height. MAIN OUTCOME MEASURES: Humeral plane of elevation, humeral elevation, and humeral axial rotation. RESULTS: Wearing a wrist splint increased the maximum humeral elevation angle (P<.001), and the height of the barrier also increased the maximum humeral elevation angle (P<.001). The average difference in maximum humeral elevation between the splint and the no splint conditions was 6.8 degrees . CONCLUSIONS: Wearing a wrist splint while performing a job that requires removing objects from a box can increase risk factors for shoulder disorders. Workplace analysis should be performed to avoid secondary injuries before a patient wearing a wrist splint returns to work.

Adult↗

PubMed2005

Changes in the long head of the biceps tendon in rotator cuff tear shoulders.

BACKGROUND: Morphologic changes in the long head of the biceps tendon have been described in association with rotator cuff disease, yet mechanical significance of these changes remains unclear. METHODS: An experiment was designed to test the hypotheses that the cross-sectional area and material properties of the long head of the biceps tendon are different in shoulders with full thickness rotator cuff tears and shoulders with intact rotator cuff tendons. Seven pairs of cadaver shoulders were tested. In each pair one shoulder had a full thickness rotator cuff tear and the other did not. Thus, a matched design was used. Cross sectional areas were measured. Tendon material properties were measured using an optical strain system. FINDINGS: We were unable to detect a statistically significant difference in the long head of the biceps area or material properties between tendons in shoulders with and without rotator cuff tears. An a priori power analysis was conducted indicating the sample size was sufficient to detect a difference of 70 MPa in the elastic modulus measurement. INTERPRETATION: Our data indicate there is no difference in the long head of the biceps cross sectional area or material properties. Therefore, the long head of the biceps tendon appears to retain its material properties in the presence of a rotator cuff tear. The clinical significance of this finding is that the long head of the biceps can be retained in the presence of a rotator cuff tear without concern that mechanical properties have substantially deteriorated.

Anatomy, Cross-Sectional↗

PubMed2005

An EMG-driven model of the upper extremity and estimation of long head biceps force.

An electromyography (EMG) driven model of the upper extremity has been developed that incorporates musculoskeletal geometry of the glenohumeral and elbow joints, estimated relevant physiologic muscle parameters including optimal muscle lengths, and EMG activity. The model is designed to predict forces in muscles spanning the glenohumeral joint resulting from functionally relevant tasks. The model is composed of four sub-models that comprise a mathematical as well as graphical three-dimensional representation of the upper extremity: a musculoskeletal model for estimation of muscle-tendon lengths and moment arms, a Hill-based muscle force model, a model for estimating optimal muscle lengths, and a model for estimation of muscle activation from EMG signal of the biceps. The purpose of this paper is to describe the components of the model, as well as the data required to drive the model. Collection of data is described in the context of applying the model to determine biceps muscle forces for testing of functional tasks. Results obtained from applying the model to analyze the functional tasks are summarized, and model strengths and limitations are discussed.

Computer Simulation↗

PubMed2005

A stochastic model of elbow flexion strength for subjects with and without long head biceps tear.

The classical approach of musculoskeletal modeling is to predict muscle forces and joint torques with a deterministic model constructed from parameters of an average subject. However, this type of model does not perform well for outliers, and does not model the effects of parameter variability. In this study, a Monte-Carlo model was used to stochastically simulate the effects of variability in musculoskeletal parameters on elbow flexion strength in healthy normals, and in subjects with long head biceps (LHB) rupture. The goal was to determine if variability in elbow flexion strength could be quantifiably explained with variability in musculoskeletal parameters. Parameter distributions were constructed from data in the literature. Parameters were sampled from these distributions and used to predict muscle forces and joint torques. The median and distribution of measured joint torque was predicted with small errors (< 5%). Muscle forces for both cases were predicted and compared. In order to predict measured torques for the case of LHB rupture, the median force and mean cross-sectional area in the remaining elbow flexor muscles is greater than in healthy normals. The probabilities that muscle forces for the Tear case exceed median muscle forces for the No-Tear case are 0.98, 0.99 and 0.79 for SH Biceps, brachialis and brachioradialis, respectively. Differences in variability of measured torques for the two cases are explained by differences in parameter variability.

Computer Simulation↗

PubMed2004

Musculoskeletal parameters of muscles crossing the shoulder and elbow and the effect of sarcomere length sample size on estimation of optimal muscle length.

BACKGROUND: Knowledge of musculoskeletal parameters is essential to understanding and modeling a muscle's force generating capability. A study of musculoskeletal parameters was conducted in two parts: (I) Empirical measurement of upper extremity musculoskeletal parameters. (II) Computational bootstrap simulation to examine statistical power of detecting optimal muscle length as a function of sarcomere length sample size and effect size. METHODS: Parameters were determined with a cadaver model. Sarcomere lengths were measured for 120 samples per muscle using laser diffraction and the mean sarcomere length used to estimate optimal muscle length. A bootstrap computational simulation was conducted to estimate variance in mean sarcomere length as a function of sample size. Statistical power for detecting optimal muscle length as a function of sample size and effect size was then determined. FINDINGS: Parameters are reported in tabular format. Power is 80% at approximately 85, 50, 40 and 25 samples for effect sizes of 0.5, 0.75, 1.0 and 1.5 mm respectively. INTERPRETATION: Musculoskeletal parameters for predicting muscle forces can be adequately measured in a cadaver model. Measurement of 40-60 sarcomere lengths per muscle is sufficient to calculate mean sarcomere length for estimating optimal muscle length with power of 80% for an effect size of 0.75-1.0 mm.

Adult↗

PubMed2003

Glenoid inclination is associated with full-thickness rotator cuff tears.

Anatomic factors, such as a hooked acromion, have been associated with rotator cuff disorders. Orientation of the glenoid relative to the scapula has been implicated in shoulder instability, but it has not been linked to rotator cuff disorders. The purpose of the current study was to test the hypothesis that superior inclination of the glenoid is associated with full-thickness rotator cuff tears. Glenoid inclination angles were measured from 16 shoulder radiographs of a convenience sample of eight cadavers in which one shoulder had an intact rotator cuff and the other shoulder had a full-thickness rotator cuff tear. Glenoid inclination angles for shoulders with rotator cuff tears were compared with contralateral normal shoulders using nonparametric statistical analysis. The glenoid inclination angle was greater in cadaver shoulders having full-thickness rotator cuff tears (98.6 degrees ) than in shoulders without tears (91.0 degrees ). A second experiment was done to assess the reliability of using 34 Grashey view radiographs from a clinical population to measure glenoid inclination angle. A method to measure the glenoid inclination on Grashey views was tested and was found to correlate with the inclination angles measured on cadaveric scapulae. Intrarater reliability of measurements from clinical Grashey views was 0.93, and interrater reliability was at least 0.88.

Aged↗

PubMed2002

Quantitative morphology of full thickness rotator cuff tears.

The occurrence of full thickness rotator cuff tears (RCTs) at time of death, the size and distribution of those tears among the tendons of the rotator cuff, and the anterior to posterior and medial to lateral dimensions of the RCTs were determined. A subset of 57 shoulders from a group of 414 were found to have full thickness rotator cuff tears. The three-dimensional coordinates of specific bony landmarks and points defining the circumference of the RCT were digitized using a Flock of Birds DC electromagnetic tracking device. Bony landmarks were used to determine the separation between adjacent tendons of the rotator cuff. Points describing the circumference of the RCT were used to calculate the area of the tear. The majority of tears occurred in the supraspinatus tendon alone (25), or in both the supraspinatus and infraspinatus tendons (22). The areas of the RCTs ranged from 0.07 cm(2) to 19.17 cm(2) with an average of 4.43 cm(2). The mean anterior to posterior length was 1.95 cm. The mean medial to lateral length was 1.98 cm.

Aged↗

PubMedDate not supplied

Effect of rotator cuff pathology on shoulder rhythm.

The purpose of this study was to test the hypothesis that shoulder rhythm is affected by rotator cuff pathology during arm elevation. We divided 42 subjects into 3 groups: those with full-thickness rotator cuff tears (RCTs) (n = 14), those with tendinopathy (n = 13), and control subjects (n = 15). Shoulder kinematics was recorded while subjects performed elevation in the sagittal and scapular planes. Euler angles were computed for scapular and humeral elevation. Data were divided into 3 equal phases. Lines were fit and the slope determined for each phase. Significant differences in slopes ( P < .05) were found between experimental groups for both motions. The RCT group had higher slopes in the initial and middle phases for sagittal elevation and in the middle phase for scapular abduction. The scapula was elevated more in the RCT group in the initial two thirds of movement. This motion may change the length of remaining muscles so that they operate on a more effective part of their length-tension curve.

Adult↗

PubMedDate not supplied

The effect of glenoid inclination on superior humeral head migration.

Superior humeral head migration may contribute to the development of rotator cuff disease. The purpose of this study was to test the hypothesis that superior inclination of the glenoid facilitates superior humeral head migration. Eight cadaveric shoulders were tested by use of a custom test fixture, and rotator cuff forces were applied. Glenoid inclination was varied (intact, +5 degrees, +10 degrees, and +15 degrees ), and the force required to produce superior humeral head migration was measured. Each increase in glenoid inclination (more superiorly facing glenoid) produced significant reduction in the force required for superior humeral head migration (5 degrees, 14.2% reduction; 10 degrees, 29.9% reduction; and 15 degrees, 37.5% reduction; P <.001). These findings demonstrate that glenoid inclination is an important factor in determining the force required for superior humeral head migration. This suggests that a more upward-facing glenoid increases the risk for superior humeral translation and, in turn, may play a role in the development of rotator cuff disease.

Aged↗

PubMedDate not supplied

Ligamentous restraints to anterior and posterior translation of the sternoclavicular joint.

This experiment was conducted to determine the primary ligamentous restraints to anterior and posterior translation of the sternoclavicular joint. Twenty-four unpaired cadaver specimens were mounted in a custom fixture. Anterior and posterior translations were measured under a sub-failure load in the intact specimen and again after transecting one randomly chosen ligament (anterior capsule, posterior capsule, interclavicular ligament, and costoclavicular ligament; n = 6 for each group). Cutting the posterior capsule resulted in significant increases in anterior translation and posterior translation. Cutting the anterior capsule produced significant increases in anterior translation. Cutting the costoclavicular and interclavicular ligaments had little effect on sternoclavicular joint translation. The posterior capsule is the most important restraint for anterior and posterior translation of the sternoclavicular joint. The anterior capsule is another important restraint for anterior translation. The costoclavicular and interclavicular ligaments have little effect on anterior or posterior translation of the sternoclavicular joint.

Aged↗

PubMedDate not supplied

Shoulder muscle activity increases with wrist splint use during a simulated upper-extremity work task.

OBJECTIVE: The purpose of this study was to test the hypothesis that wearing a wrist splint while performing a common light manufacturing task (moving an object from a bin) increases shoulder muscle activity. METHODS: Electromyography (EMG) signals were evaluated from the anterior, middle, and posterior deltoid, trapezius, supraspinatus, and infraspinatus of 14 volunteers while they moved an object from a bin. Two test conditions were measured: with and without a wrist splint. The height of the bin was also varied. RESULTS: Wearing a wrist splint increased maximum EMG for all six muscles and average levels for the deltoid (anterior, middle, posterior) and trapezius. As bin height increased, maximum muscle activity increased in the deltoid (anterior, middle, and posterior) and trapezius, and the average increased in the deltoid (middle and posterior) and trapezius. CONCLUSIONS: Workplace factors can modify the activation of a patient's shoulder muscles when he or she is wearing a wrist splint. An ergonomic job analysis should be conducted for patients who are returning to work wearing wrist splints.

Adult↗