Humeral Abduction Angle Research Articles

Greater distance from the glenosphere center to the acromion reduces risk of acromial impingement in semi-inlay reverse shoulder arthroplasty

BackgroundRecently, the issue of subacromial notching, caused by acromial impingement has been reported. The purpose of this study was to assess the impact of differences in the distance between the glenosphere center and the greater tuberosity (DGT) and the distance between the glenosphere center and the acromion (DA) on the closest distance between the greater tuberosity and the acromion during active abduction in shoulders with reverse total shoulder arthroplasty (RSA). MethodsEleven shoulders with semi-inlay RSA were analyzed. Subjects underwent fluoroscopy during active scapular plane abduction. Computed tomography of their shoulders was performed to create 3-dimensional implant models at a mean of 16 months after surgery. Using model-image registration techniques, poses of 3-dimensional implant models were iteratively adjusted to match their silhouettes with the silhouettes in the fluoroscopic images (shape matching), and 3-dimensional kinematics of implants were computed. The closest distance between the acromion and greater tuberosity was computed at maximum abduction. DA and DGT were measured from 3-dimensional surface models. Shoulders were divided into two groups based on DA and DGT measurements and their closest distance data were compared between the groups. ResultsThere were 7 shoulders with DA ≥ DGT, and 4 shoulders with DA < DGT. Shoulders with DA ≥ DGT showed a significantly wider distance between the greater tuberosity and acromion at maximum abduction compared to those with DA < DGT (5.9 ± 2.4 mm vs. 0.6 ± 0.7 mm, respectively, P = 0.0021). There were no significant differences in maximum glenohumeral abduction angle and humeral abduction angle between the two groups. Although DA was significantly greater in shoulders with DA ≥ DGT than in those with DA < DGT (43.7 ± 4.4 mm vs. 35.1 ± 6.7 mm, respectively, P = 0.0275), there was no significant difference in DGT between the two groups. ConclusionsWhen DGT is less than DA in shoulders with RSA, the closest distance between the greater tuberosity and the acromion at maximum abduction is significantly wider compared to cases where DGT is greater than DA by 3-dimensional measurement. Therefore, acromial impingement is less likely to occur in shoulders with RSA when DA is greater than DGT. To avoid acromial impingement, it might be important to make DA greater than DGT.

The Effects of Body Positions and Abduction Angles on Shoulder Muscle Activity Patterns during External Rotation Exercises.

Excess and repetitive glenohumeral external rotation (ER) is at a higher risk for shoulder injuries, which occurs frequently in professional sports and specific occupations. Current rehabilitation programs emphasize selective targeting of muscle activity, which can help restore dysfunctional muscle imbalances or prevent injuries. However, the impact of different body postures on GH muscle activity during ER exercises has not been fully understood. Therefore, the purpose of this study was to investigate shoulder EMG activity for different body positions and humeral abduction angles during ER exercises. Twenty-three healthy young men (age: 22.3 ± 2.3, height: 175.75 ± 4.02, mass: 75.37 ± 9.14) participated in this study. Surface Electromyography was recorded from seven shoulder muscles: upper trapezius, lower trapezius, serratus anterior, infraspinatus, and deltoid. Six ER exercises: three postures (sitting, supine lying, and prone lying) and two abduction angles (ABD; 45° and 90°) were tested using an isokinetic dynamometer. During a sitting position, the lower trapezius/upper trapezius muscle activity ratios were significantly increased for sitting compared to supine lying and prone lying (p < 0.001, p = 0.004). Serratus anterior/upper trapezius co-contraction indices were significantly increased for 90° than 45° ABD (p < 0.001). These findings can provide insight into new training programs aimed at restoring GH muscle imbalances.

Influence of humeral abduction angle on axial rotation and contact area at the glenohumeral joint

Although the elevation angle of the arm affects the range of rotation, it has not been evaluated up to the maximal abduction angle. In this study we conducted an evaluation up to maximal abduction and determined the contact patterns at the glenohumeral (GH) joint. Fourteen healthy volunteers (12 men and 2 women; mean age, 26.9 years) with normal shoulders (14 right and 8 left) were instructed to rotate their shoulders at 0°, 90°, 135°, and maximal abduction for each shoulder at a time. Using 2-dimensional and 3-dimensional single-plane image registration, the internal rotation (IR), external rotation (ER), and range of motion (ROM; ie, axial rotations) at the thoracohumeral (TH) and GH joints, and the contribution ratio (%ROM = GH-ROM/TH-ROM) were calculated for each abduction. The glenoid position with respect to the humeral head was also analyzed. The TH-IR and TH-ER shifted toward an ER with increasing abduction angle, whereas the TH-ROM significantly decreased except at abduction between 0° and 90° (P < .001). The GH-IR and GH-ROM significantly decreased except at abduction between 0° and 90° (P < .001), but the GH-ER remained constant regardless of the abduction. The contribution ratio exceeded 80% for every abduction angle. The glenoid moved on the central and posterior areas of the humeral head at 0° and 90° abduction, respectively, and on the posterosuperior and anterosuperior areas at 135° and maximal abduction, respectively. Our results provide new knowledge about wide axial rotation up to maximal abduction and constant GH-ER at any abduction.

Female maximal push/pull strength capabilities by humeral abduction angle in bilateral exertions

Pushing or pulling an object constitutes the majority of manual materials handling tasks. Anthropometric differences between workers alter pushing and pulling strategies at fixed heights, potentially modifying exposures and causing overexertion. Capability normalized to arm posture rather than work height remains unknown, and the purpose of this research was to quantify maximal pushing and pulling strength and upper extremity joint moments using fixed humeral abduction angles and a flexed arm position. Twenty university-aged females completed maximal pushes and pulls at 0°, 30°, 60°, 90°, and 120° of humeral abduction with an elbow to 90°. Abduction angle was the largest modifier of both push and pull force generating capability (p < 0.01), with increasing abduction reducing force capability by up to 30%. While push exertions on average exceeded pulls by 17 N (p < 0.01), the difference is much smaller than previous reports. Ergonomists should consider humeral angle of the worker rather than work heights, as individuals working in increased abduction decreases capability and increases potential overexertion injury risk.

The effects of shoulder abduction angle and wrist angle on upper extremity muscle activity in unilateral right handed push/pull tasks

Workstation design often considers wrist posture or humeral angle in efforts to minimize worker injury risk. However, little research exists on examining co-dependencies between upper extremity joint angles for horizontal pushes and pulls. This study examined interactions of wrist posture and humeral abduction angle on upper extremity muscular activity in pushes and pulls. Twenty female participants exerted 30N while seated in neutral, flexed and extended wrist postures and humeral abduction angles of 0°, 45°, 90°, and 120°. Influences of wrist posture and humeral abduction angle existed for almost all muscles in both force directions, with interactions appearing in some muscles (p = .0001–.0436). A main effect of humeral abduction angle occurred for 8 of the 14 muscles tested in pushes (p = .0001–.045), and 12 of 14 muscles in pulls (p = .0001–.0488). The greatest increase in activation was in lower trapezius, experiencing a 25 %MVE activation when moving from low humeral angles to high angles. A bimodal distribution in activation by humeral angle appeared in many muscles, with 0° and 45° abduction generally eliciting lower activation levels than 90° and 120° exertions. Wrist posture affected over two thirds of muscle activation levels (p = .0001–.0436) with non-neutral wrist postures eliciting up to 13 %MVE increases over neutral wrist exertions. These novel findings indicate that these upper extremity joints should not be investigated in isolation, as effects at the distal joint affect muscles at the proximal one, and vice versa. Ergonomists and work task designers should focus on considering interactions of joints in the upper extremity, and use these insights to help devise future workstation designs.

Ultrasound comparison of the effects of prehabilitation exercises and the scapular assistance test on the acromiohumeral distance

Background: Prolonged participation in overhead sports creates shoulder muscle imbalances which eventually alter the efficacy of the shoulder stabiliser muscles and heighten injury risk, such as subacromial impingement syndrome. Objectives: The aim of this study was to determine if ultrasound is effective to measure the acromiohumeral distance (AHD) to compare the effect of the scapular assistance test (SAT) on the AHD with a prehabilitative exercise intervention programme in asymptomatic cricket players. Methods: Baseline testing on cricket players from the North- West University cricket squad (N=34) included AHD measurements performed by a sonographer at 0°, 30° and 60° humeral abduction angles respectively, with and without the SAT application. Players were then randomly assigned to an intervention and control group. The control group continued with their normal in-season programme, whereas the intervention group also performed shoulder stability exercises for six weeks. Results: The exercise intervention had a similar effect as the SAT on the AHD at 0o and 30o humeral abduction angles in the intervention group. The AHD measurements in the exercise intervention group indicated widening at all abduction angles after the six-week intervention period, whereas the AHD measurements in the control group were equal or smaller than baseline measurements without the SAT at 30o and 60o respectively. Conclusion: Exercise intervention has a similar effect on the AHD of asymptomatic cricket players compared to the SAT – especially in 0°and 30o of humeral abduction. Ultrasound can therefore be utilised to assist in identifying the risk of developing subacromial impingement syndrome (SIS) in asymptomatic overhead athletes by measuring the AHD at different angles of humeral abduction, without and with the SAT application.

Ultrasound comparison of the effects of prehabilitation exercises and the scapular assistance test on the acromiohumeral distance

Background: Prolonged participation in overhead sports creates shoulder muscle imbalances which eventually alter the efficacy of the shoulder stabiliser muscles and heighten injury risk, such as subacromial impingement syndrome. Objectives: The aim of this study was to determine if ultrasound is effective to measure the acromiohumeral distance (AHD) to compare the effect of the scapular assistance test (SAT) on the AHD with a prehabilitative exercise intervention programme in asymptomatic cricket players. Methods: Baseline testing on cricket players from the North- West University cricket squad (N=34) included AHD measurements performed by a sonographer at 0°, 30° and 60° humeral abduction angles respectively, with and without the SAT application. Players were then randomly assigned to an intervention and control group. The control group continued with their normal in-season programme, whereas the intervention group also performed shoulder stability exercises for six weeks. Results: The exercise intervention had a similar effect as the SAT on the AHD at 0o and 30o humeral abduction angles in the intervention group. The AHD measurements in the exercise intervention group indicated widening at all abduction angles after the six-week intervention period, whereas the AHD measurements in the control group were equal or smaller than baseline measurements without the SAT at 30o and 60o respectively. Conclusion: Exercise intervention has a similar effect on the AHD of asymptomatic cricket players compared to the SAT – especially in 0°and 30o of humeral abduction. Ultrasound can therefore be utilised to assist in identifying the risk of developing subacromial impingement syndrome (SIS) in asymptomatic overhead athletes by measuring the AHD at different angles of humeral abduction, without and with the SAT application.

In vivo kinematic analysis of the glenohumeral joint during dynamic full axial rotation and scapular plane full abduction in healthy shoulders.

The purpose of this study was to evaluate the kinematics of healthy shoulders during dynamic full axial rotation and scapular plane full abduction using three-dimensional (3D)-to-two-dimensional (2D) model-to-image registration techniques. Dynamic glenohumeral kinematics during axial rotation and scapular plane abduction were analysed in 10 healthy participants. Continuous radiographic images of axial rotation and scapular plane abduction were taken using a flat panel radiographic detector. The participants received a computed tomography scan to generate virtual digitally reconstructed radiographs. The density-based digitally reconstructed radiographs were then compared with the serial radiographic images acquired using image correlations. These 3D-to-2D model-to-image registration techniques determined the 3D positions and orientations of the humerus and scapula during dynamic full axial rotation and scapular plane full abduction. The humeral head centre translated an average of 2.5±3.1mm posteriorly, and 1.4±1.0mm superiorly in the early phase, then an average of 2.0±0.8mm inferiorly in the late phase during external rotation motion. The glenohumeral external rotation angle had a significant effect on the anterior/posterior (A/P) and superior/inferior (S/I) translation of the humeral head centre (both p<0.05). 33.6±15.6° of glenohumeral external rotation occurred during scapular plane abduction. The humeral head centre translated an average of 0.6±0.9mm superiorly in the early phase, then 1.7±2.6mm inferiorly in the late phase, and translated an average of 0.4±0.5mm medially in the early phase, then 1.6±1.0mm laterally in the late phase during scapular plane abduction. The humeral abduction angle had a significant effect on the S/I and lateral/medial (L/M) translation of the humeral head centre (both p<0.05). This study investigated 3D translations of the humerus relative to the scapula: during scapular plane full abduction, the humerus rotated 33.6° externally relative to the scapula, and during external rotation motion in the adducted position, the humeral head centre translated an average of 2.5mm posteriorly. Kinematic data will provide important insights into evaluating the kinematics of pathological shoulders. For clinical relevance, quantitative assessment of dynamic healthy shoulder kinematics might be a physiological indicator for the assessment of pathological shoulders.

Comparison of humeral rotation co-activation of breast cancer population and healthy shoulders

Upper limb morbidities are common amongst the breast cancer population (BCP) and have a direct impact on independence. Comparing muscle co-activation strategies between BCP and healthy populations may assist in identifying muscle dysfunction and promote clinical interpretation of dysfunction, which could direct preventative and therapeutic interventions. The purposes of this study were to define humeral rotation muscle co-activation of a BCP and to compare it with a previously defined co-activation relationship of a healthy population. Fifty BCP survivors performed 18 isometric internal and external rotation exertions at various postures and intensities. Surface and intramuscular electrodes recorded shoulder muscle activity. BCP co-activation was predicted at r2=0.77 during both exertion types. Humeral abduction angle and task intensity were important factors in the prediction of co-activation in both populations. Comparisons made between populations identified differing muscle strategies used by BCP to maintain postural control. Compared to healthy co-activation, the BCP demonstrated greater activation of internal (IR) and external rotator (ER) type muscles during their respective rotation type. The BCP demonstrated increased (⩾8.7%) activation of pectoralis major. This study has provided insight into how BCP muscles compensate during dysfunction. Continued advancement of this knowledge can provide more understanding of dysfunction, promote generation of evidence-based therapies, and can be useful in biomechanical modeling.

Comparing surface and indwelling electromyographic signals of the supraspinatus and infraspinatus muscles during submaximal axial humeral rotation

This study quantified the relationship between EMG signals recorded by surface and indwelling electrodes for the infraspinatus and supraspinatus during submaximal axial humeral rotation. Muscular activity was measured on 20 participants during 82 submaximal isometric internal or external axial humeral rotations in a range of postures and intensities. Equations to predict indwelling magnitudes from surface data were generated and the effects of humeral angle and intensity on this relationship were also evaluated.Supraspinatus surface data explained 72–76% of the variance in the indwelling data. Surface data overestimated indwelling data by up to 30% of maximal voluntary contraction (MVC). Infraspinatus surface data explained 62–64% of the variance in the indwelling data, but overestimated by 72% and 400% MVC in external and internal axial humeral rotation trials, respectively. Humeral abduction angle and exertion intensity both altered the relationship between electrode types modestly (p<0.01) for most muscles and exertions. Better variance explanation was achieved for these submaximal exertions than previously reported values for maximal exertions.These results help inform electrode type selection for the recording of supraspinatus and infraspinatus EMG. Caution is recommended when interpreting surface recordings as indicators of indwelling recordings for exertions where the muscle studied is not a primary mover.

Non-invasive Error-assessment of the Acromial-Sensor-Tracking Protocol for the Measurement of Scapular Orientation

The acromial-sensor-tracking protocol with an electromagnetic tracking device is a non-invasive measurement protocol for recording the three-dimensional scapular movement continuously. In the present study, the orientations of motionless scapula were determined with the acromial-sensor-tracking protocol and the magnitude of the measurement error attributable to the skin-movement was assessed non-invasively by the landmark-digitizing protocol with the digitizer. Three sensors of the electromagnetic tracking device were attached to the skin overlaying the sternum, acromion and humerus, and three or more bony landmarks for each segment were manually digitized with the stylus to define the anatomical meaningful orientation. After the initial digitizing, the subject was asked to maintain the arm at five positions. While the subject was maintaining the arm, the orientation of the scapula was determined simultaneously by the attached sensors and by the directly digitizing of the scapular bony landmarks (the landmark-digitizing protocol). The mean values for the root mean square (RMS) errors representing the differences in the measured scapular orientation between the acromial-sensor-tracking protocol and the landmark-digitizing protocol across the five humeral abduction angles were found to be <5.2°. The magnitude of the measurement error exhibited in acromial-sensor-tracking protocol was substantially smaller than the range of the scapular movement exhibited during the humeral abduction. The results demonstrate that the acromial-sensor-tracking protocol is a valid measurement protocol to describe the three-dimensional continuous scapular movement with sufficient accuracy.