scholarly journals Anatomy and Biomechanic of the Shoulder

2019 ◽  
Vol 7 (11_suppl6) ◽  
pp. 2325967119S0046
Author(s):  
Troydimas Panjaitan
Keyword(s):  
Rotator Cuff ◽  
Humeral Head ◽  
Glenohumeral Joint ◽  
External Rotation ◽  
Central Component ◽  
Subscapularis Tendon ◽  
Glenoid Fossa ◽  
Greater Tuberosity ◽  
Glenohumeral Ligaments ◽  
Shoulder Complex

The shoulder is one of the most complex joints of the human body. Consequently, they are susceptible to injury and degeneration. Mechanical shoulder pathology typically results when overuse, extremes of motion, or excessive forces overwhelm intrinsic material properties of the shoulder complex resulting in tears of the rotator cuff, capsule, and labrum. The fundamental central component of the shoulder complex is the glenohumeral joint. It has a ball-and-socket configuration with a surface area ratio of the humeral head to glenoid fossa of about 3:1 with an appearance similar to a golf ball on a tee. Overall, there is minimal bony covering and limited contact areas that allow extensive translational and rotational ability in all three planes. The glenohumeral joint has 2 groups of stabilizers, which are static (passive) and dynamic (active) restrains. Static stabilizers include the concavity of the glenoid fossa, glenoid fossa retroversion and superior angulation, glenoid labrum, the joint capsule, and glenohumeral ligaments, and a vacuum effect from negative intra-articular pressure. Dynamic stabilization is merely the coordinated contraction of the rotator cuff muscles that create forces that compress the articular surfaces of the humeral head into the concave surface of the glenoid fossa. During upper extremity movement, the effects of static stabilizers are minimized and dynamic or active stabilizers become the dominant forces responsible for glenohumeral stability The simple act of arm elevation is a complex task that occurs via the combination of glenohumeral and scapulothoracic motion, together known as scapulohumeral rhythm. In the first 1200, glenohumeral arm abduction, the supraspinatus and deltoid work together and create a force couple that promotes stability, while raising the arm (deltoid contraction). In addition, the humerus must undergo 450 external rotation to not only clear the greater tuberosity posteriorly but also loosen the inferior glenohumeral ligament (IGHL) to allow maximum elevation. There are several anatomical updates regarding the rotator cuff and capsular footprint. The footprint of the supraspinatus on the greater tuberosity is much smaller than previously believed, and this area of the greater tuberosity is actually occupied by a substantial amount of the infraspinatus. The superior-most insertion of the subscapularis tendon extends a thin tendinous slip, which attaches to the fovea capitis of the humerus. The teres minor muscle inserts to the lowest impression of the greater tuberosity of the humerus and additionally inserts to the posterior side of the surgical neck of the humerus.

Ligamentous Restraints to External Rotation of the Humerus in the Late-Cocking Phase of Throwing

2000 ◽  
Vol 28 (2) ◽  
pp. 200-205 ◽  
Author(s):  
John E. Kuhn ◽  
Michael J. Bey ◽  
Laura J. Huston ◽  
Ralph B. Blasier ◽  
Louis J. Soslowsky
Keyword(s):  
Rotator Cuff ◽  
Glenohumeral Joint ◽  
External Rotation ◽  
Coracoacromial Ligament ◽  
Glenohumeral Ligament ◽  
Coracohumeral Ligament ◽  
Potential Source ◽  
Glenohumeral Ligaments ◽  
Inferior Glenohumeral Ligament ◽  
Glenohumeral Capsule

The late-cocking phase of throwing is characterized by extreme external rotation of the abducted arm; repeated stress in this position is a potential source of glenohumeral joint laxity. To determine the ligamentous restraints for external rotation in this position, 20 cadaver shoulders (mean age, 65 16 years) were dissected, leaving the rotator cuff tendons, coracoacromial ligament, glenohumeral capsule and ligaments, and coracohumeral ligament intact. The combined superior and middle glenohumeral ligaments, anterior band of the inferior glenohumeral ligament, and the entire inferior glenohumeral ligament were marked with sutures during arthroscopy. Specimens were mounted in a testing apparatus to simulate the late-cocking position. Forces of 22 N were applied to each of the rotator cuff tendons. An external rotation torque (0.06 N m/sec to a peak of 3.4 N m) was applied to the humerus of each specimen with the capsule intact and again after a single randomly chosen ligament was cut (N 5 in each group). Cutting the entire inferior glenohumeral ligament resulted in the greatest increase in external rotation (10.2° 4.9°). This was not significantly different from sectioning the coracohumeral ligament (8.6° 7.3°). The anterior band of the inferior glenohumeral ligament (2.7° 1.5°) and the superior and middle glenohumeral ligaments (0.7° 0.3°) were significantly less important in limiting external rotation.

scholarly journals Shoulder: Instability

2021 ◽  
pp. 1-9
Author(s):  
Michael J. Tuite ◽  
Christian W. A. Pfirrmann
Keyword(s):  
Glenohumeral Joint ◽  
External Rotation ◽  
Rotator Cuff Tears ◽  
Glenoid Fossa ◽  
Glenohumeral Instability ◽  
Glenoid Labrum ◽  
Glenohumeral Ligaments ◽  
Labral Tears ◽  
The Stability ◽  
Spinoglenoid Notch

AbstractGlenohumeral instability is the inability to keep the humeral head centered in the glenoid fossa. Glenohumeral instability can be classified according to etiology and direction of instability. The glenoid labrum, the glenohumeral ligaments, and the bony structures contribute to the stability glenohumeral joint and need to be addressed with imaging. One of the difficulties with accurately diagnosing labral tears on MR imaging is the normal labral variants, which can sometimes appear similar to tears. The location and extent of a Hill-Sachs lesion and glenoid rim defects need to be related to recognize engaging Hill-Sachs lesions or off-track situations. There are several types of labral tears that are not associated with a prior dislocation. SLAP tears are one of the more common tears of the labrum and can sometimes be difficult to distinguish from a normal variant superior sublabral recess. Labral tears in overhead thrower occur in the posterosuperior labrum, adjacent to the posterior rotator cuff tears in these athletes. Tears in the posterosuperior labrum are also associated with spinoglenoid notch paralabral cysts, which can be painful and cause external rotation weakness.

Massive Cuff Tears Alter Joint Function and Decrease Cartilage Mechanics Following Return to Overuse Activity in a Rat Model

2012 ◽  
Author(s):  
Katherine E. Reuther ◽  
Stephen J. Thomas ◽  
Joseph J. Sarver ◽  
Jennica J. Tucker ◽  
Chang-Soo Lee ◽  
...  
Keyword(s):  
Rotator Cuff ◽  
Humeral Head ◽  
Glenohumeral Joint ◽  
Joint Damage ◽  
Force Balance ◽  
Subscapularis Tendon ◽  
Joint Function ◽  
Massive Rotator Cuff Tear ◽  
Secondary Damage ◽  
Anterior Posterior

Rotator cuff tendon tears are common conditions which can alter shoulder joint function and over time, cause secondary damage to the surrounding tissues, including the cartilage and other remaining tendons. Glenohumeral joint stability is dependent on a dynamic balance between rotator cuff forces, in particular the subscapularis anteriorly and the infraspinatus posteriorly. An intact rotator cuff stabilizes the joint, allowing for concentric rotation of the humeral head on the glenoid. However, a massive rotator cuff tear involving the supraspinatus and infraspinatus may disrupt the normal balance of forces at the joint, resulting in abnormal joint loading. This is of particular concern in populations who perform activities requiring repeated overhead activity (e.g., laborers, athletes). Our lab has previously demonstrated that restoration of the subscapularis-infraspinatus anterior-posterior force balance improves shoulder function by providing a stable fulcrum for concentric rotation of the humeral head on the glenoid [1]. However, the long term consequences caused by disruption of the anterior-posterior force balance (supraspinatus and infraspinatus tear) on the glenoid cartilage and adjacent (intact) tendons, particularly in the case of an overuse population, remains unknown. Therefore, the objective of this study was to investigate the effect of disrupting the anterior-posterior force balance on joint function and joint damage using a clinically relevant overuse model system. We hypothesized that a disrupted anterior-posterior force balance (supraspinatus and infraspinatus tear) would result in H1) decreased joint function and H2) inferior adjacent tissue (glenoid cartilage, biceps and subscapularis tendon) properties compared to an intact anterior-posterior force balance (supraspinatus only tear).

scholarly journals The Area of Impingement in the Throwing Versus Nonthrowing Shoulder of Collegiate Baseball Players: An MRI Study of the Simulated Late-Cocking Phase of Throwing

2021 ◽  
Vol 9 (3) ◽  
pp. 232596712199213
Author(s):  
Makoto Takahashi ◽  
Koji Iwamoto ◽  
Masahiko Monma ◽  
Hirotaka Mutsuzaki ◽  
Masafumi Mizukami
Keyword(s):  
Rotator Cuff ◽  
Glenohumeral Joint ◽  
External Rotation ◽  
Rotator Cuff Tears ◽  
Shoulder Abduction ◽  
Baseball Players ◽  
Greater Tuberosity ◽  
Internal Impingement ◽  
Collegiate Baseball ◽  
Cystic Changes

Background: During shoulder abduction and external rotation, internal impingement can occur when compressive forces between the greater tuberosity and the posterior glenoid rim pinch the undersurface of the rotator cuff. Previous studies on internal impingement have focused on qualitative results such as pathological findings; however, few studies have quantified the area of impingement (AOI) of the rotator cuff muscles between the greater tuberosity and the posterior glenoid rim. Purpose: To compare the AOI between the throwing and nonthrowing shoulders of baseball players. Study Design: Controlled laboratory study. Methods: A total of 14 asymptomatic male collegiate baseball players participated in this study. The AOI in both the throwing and the nonthrowing shoulders was calculated using magnetic resonance imaging (MRI) scans. The MRI measurements were collected with the shoulder at 90° of abduction and at 90° and 100° of external rotation. The area, width, and depth of impingement as well as cystic changes in the greater tuberosity and degeneration in the posterior labrum were compared between the throwing and nonthrowing shoulders. Results: The AOI was significantly greater in the throwing shoulders than in the nonthrowing shoulders (90° of external rotation: 32.4 vs 19.1 mm2, respectively; 100° of external rotation, 28.0 vs 15.6 mm2, respectively; P < .001 for both). Compared with the nonthrowing shoulders, there were more positive findings in the throwing shoulders regarding greater tuberosity cystic changes (0 vs 7, respectively; P = .006) and posterior labral degeneration (3 vs 13, respectively; P < .001). Conclusion: The AOI and the number of lesions in the greater tuberosity and posterior labrum were greater in throwing shoulders than in nonthrowing shoulders. Therefore, damage to the insertion of the rotator cuff muscles may affect internal impingement. Clinical Relevance: Lesions in the greater tuberosity and posterior labrum in throwing shoulders may increase the AOI by expanding the joint gap behind the glenohumeral joint. Impingement of the greater tuberosity and the posterior glenoid rim may lead to rotator cuff tears.

Shoulder Range of Motion and Strength Characteristics in Circus Acrobats

2020 ◽  
Vol 35 (3) ◽  
pp. 145-152
Author(s):  
Carlie Huberman ◽  
Melissa Scales ◽  
Srikant Vallabhajosula
Keyword(s):  
General Population ◽  
Range Of Motion ◽  
Glenohumeral Joint ◽  
External Rotation ◽  
Hand Dominance ◽  
Cross Sectional ◽  
Shoulder Range Of Motion ◽  
Shoulder Strength ◽  
Shoulder Complex ◽  
Shoulder Range

OBJECTIVES: To begin to establish normative data for shoulder range of motion (ROM) and strength in the circus acrobats and to compare these values based on age, sex, hand dominance, and acrobatic subgroup. METHODS: Active (AROM) and passive (PROM) of the full shoulder complex and PROM of the isolated glenohumeral joint were measured in 193 circus acrobats using standardized techniques for anterior elevation (flexion), posterior elevation (extension), lateral elevation (abduction), and external and internal rotation. Shoulder strength was measured using a hand-held dynamometer in all planes of motion. Measurements were taken twice and averaged. Mixed ANOVA were performed. One-sample t-tests were used to compare with general population. RESULTS: Several significant differences were noted between dominant and non-dominant sides, but not between the sex or age groups tested. Acrobats who did both aerial and ground acrobatics had significantly greater full shoulder complex flexion AROM than the aerial group, and AROM extension than the ground group. Circus acrobats had significantly greater AROM full shoulder complex extension, abduction, internal and external rotation, and shoulder strength than the general population. CONCLUSION: Overall, results from this cross-sectional study revealed that circus acrobats had greater shoulder strength and ROM than the general population, which could affect the way these patients should be treated in a clinical setting. Age and sex seemed to have minimal effects, but there was clearly an effect of hand dominance. Acrobats who train both aerial and ground acrobatics may have greater ROM in certain planes than those who train in only one type of discipline.

Effect of Posterior Capsule Tightness on Glenohumeral Translation in the Late-Cocking Phase of Pitching

2007 ◽  
Vol 16 (1) ◽  
pp. 41-49 ◽  
Author(s):  
Kim M. Clabbers ◽  
John D. Kelly ◽  
Dov Bader ◽  
Matthew Eager ◽  
Carl Imhauser ◽  
...  
Keyword(s):  
Outcome Measures ◽  
Humeral Head ◽  
Glenohumeral Joint ◽  
External Rotation ◽  
Head Position ◽  
Posterior Capsule ◽  
Nonsignificant Trend ◽  
Before And After ◽  
Fresh Frozen ◽  
Head Translation

Context:Throwing injuries.Objective:To study the effects of posterior capsule tightness on humeral head position in late cocking simulation.Design:Eight fresh frozen shoulders were placed in position of “late cocking,” 90 degrees abduction, and 10 degrees adduction and maximal external rotation. 3D measurements of humeral head relationship to the glenoid were taken with an infrared motion sensor, both before and after suture plication of the posterior capsule. Plications of 20% posterior/inferior capsule and 20% entire posterior capsule were performed, followed by plications of 40% of the posterior/inferior capsule and 40% entire posterior capsule.Setting:Cadaver Lab.Intervention:Posterior capsular placation.Main Outcome Measures:Humeral head position.Results:40%, but not 20%, posterior/inferior and posterior plications demonstrated a trend to increased posterior-superior humeral head translation relative to controls.Conclusion:Surgically created posterior capsular tightness of the glenohumeral joint demonstrated a nonsignificant trend to increased posterior/superior humeral head translation in the late cocking position of throwing.

scholarly journals Kinematic Differences between Two Types of Forward Elevations of the Shoulder Joint: Flexion and Reaching Elevation

2020 ◽  
Vol 14 (1) ◽  
pp. 15-25
Author(s):  
Ryo Sahara ◽  
Junichiro Hamada ◽  
Kunio Yoshizaki ◽  
Kazuhiro Endo ◽  
Daisuke Segawa ◽  
...  
Keyword(s):  
Rotator Cuff ◽  
Elbow Joint ◽  
Glenohumeral Joint ◽  
External Rotation ◽  
Three Dimensional ◽  
Coronal Plane ◽  
Shoulder Flexion ◽  
Joint Flexion ◽  
Motion Plane ◽  
Teres Minor

Background: Extension of the elbow joint is maintained during shoulder flexion. In contrast, the arm starts from the flexed position of the elbow joint and the joint gradually extends during reaching elevation. Objectives: This study aimed to compare the kinematic elements and electromyographic (EMG) activities of the rotator cuff muscles between flexion and reaching elevation. Methods: The study included 10 healthy young men. (average age, 21.5 ± 3.4 years), and measurements were performed on their dominant arms. A three-dimensional motion analyzer was used to record the following elements during shoulder flexion and reaching elevation: the angles of glenohumeral joint elevation and scapular upward rotation, scapulohumeral rhythm, external rotation of the humerus, and glenohumeral plane shifting from the coronal plane. The EMG activities in the supraspinatus, infraspinatus, subscapularis, and teres minor were recorded simultaneously. Results: The plane of reaching elevation was retained at 60° from the coronal plane. The glenohumeral planes (P < 0 .01) and the external rotation angles of the humerus below 90° of elevation (P < 0.05) were significantly different between both the motions. The EMG activities in the supraspinatus (P < .01), infraspinatus (P < 0.05), and teres minor (P < 0.01) were significantly lower while reaching elevation than those during flexion. Conclusion: The motion plane at 60° from the coronal plane, movement of the humeral external rotation, and EMG activities of the rotator cuff muscles were different during reaching elevation and shoulder flexion.

scholarly journals Four-Dimensional Computed Tomography Evaluation of Shoulder Joint Motion in Collegiate Baseball Pitchers

2021 ◽  
Author(s):  
Daisuke Momma ◽  
Alejandro A Espinoza Orías ◽  
Tohru Irie ◽  
Tomoyo Irie ◽  
Eiji Kondo ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Internal Rotation ◽  
Contact Area ◽  
Humeral Head ◽  
Glenohumeral Joint ◽  
External Rotation ◽  
Ct Scanning ◽  
4D Ct ◽  
Collegiate Baseball ◽  
Baseball Pitchers

Abstract The purpose of this study is to evaluate the glenohumeral contact area, center of glenohumeral contact area, and center of humeral head during simulated pitching motion in collegiate baseball pitchers using four-dimensional computed tomography (4D CT). We obtained 4D CT data from the dominant and non-dominant shoulders of eight collegiate baseball pitchers during the cocking motion. CT image data of each joint were reconstructed using a 3D reconstruction software package. The glenohumeral contact area, center of glenohumeral contact area, center of humeral head, and oblateness of humeral head were calculated from 3D bone models using customized software. The center of glenohumeral contact area translated significantly from anterior to posterior during maximum external rotation to maximum internal rotation. The center of humeral head translated from posterior to anterior during maximum external rotation to maximum internal rotation. There was a high negative correlation between anterior translation of the center of glenohumeral contact area and center of humeral head, and a positive correlation between the translation and the oblateness. 4D CT analyses demonstrated that the center of humeral head translated in the opposite direction to that of the center of glenohumeral contact area during external rotation to internal rotation in abduction in the dominant and non-dominant shoulders. This diametric translation can be explained by the oblateness of the humeral head. 4D CT scanning and the software for bone surface modeling of the glenohumeral joint enabled quantitative assessment of glenohumeral micromotion and identified humeral head oblateness as the cause of diametric change.

scholarly journals Ultrasound-guided Arthroscopic Tuberoplasty for Greater Tuberosity Malunion: A Case Report

2020 ◽  
Vol 14 (1) ◽  
pp. 204-208
Author(s):  
Akira Ando ◽  
Kazuaki Suzuki ◽  
Masashi Koide ◽  
Yoshihiro Hagiwara
Keyword(s):  
Case Report ◽  
Rotator Cuff ◽  
Rotator Cuff Repair ◽  
External Rotation ◽  
Ultrasound Images ◽  
Fluoroscopic Guidance ◽  
Greater Tuberosity ◽  
Dynamic Evaluation ◽  
Arthroscopic Excision ◽  
Cuff Repair

Background: Greater Tuberosity (GT) malunion can lead to impingement against the acromion, resulting in pain, stiffness, and weakness of the rotator cuff. For patients with lesser degrees of displacement, partial removal of the GT with rotator cuff repair (tuberoplasty) under fluoroscopic guidance is considered. Case report: A sixty-five year old female fell from a standing height and suffered a minimally displaced isolated GT fracture. She was conservatively managed for four months and referred to our institution due to persisting pain and stiffness. The shoulder motion was severely restricted (anterior elevation: 90°, lateral elevation: 45°, external rotation with the arm at side: 25°, hand behind back: 4th lumber vertebrae) and pain aggravated especially when laterally elevated. Plain radiography and computed tomography showed small superiorly malunited GT and magnetic resonance imaging showed no rotator cuff pathology. Ultrasound images showed impingement of the GT against the acromion when laterally elevated. Arthroscopic excision of the malunited GT and rotator cuff repair along with capsular release and acromioplasty was performed under ultrasound guidance. The ultrasound images were simultaneously delineated to the arthroscopic monitor. Dynamic evaluation of the reshaped GT passing under the acromion was possible. Conclusion: Intraoperative use of ultrasound during arthroscopic tuberoplasty offers advantages over fluoroscopic guidance concerning control of the amount of bone resection and dynamic evaluation between the GT and the acromion in addition to the problems of radiation and space-occupying devices.

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