Analysis of the scapulo-humeral rhythm for periarthritis scapulohumeralis

To clarify the scapulo-humeral rhythm in twenty-five patients with periarthritis scapulo-humeralis, the movements of the scapula and the humerus during arm elevation were measured and analysed using a fluoroscope and a computer, and the rhythm of five patient with rotator cuff tear was compared with that of seven normal subjects. The ratio of scapular movement to humeral one in the patients with severe shoulder contracture due to periarthritis scapulohumeralis was greater than that of patients with mild contracture and that of normal subjects. In the patients with rotator cuff tear, wider range of scapular rotation was observed in the early phase of the motion. During the early phase of arm elevation, the humeral head moved to the upper direction by means of gliding in the patients with severely contracted shoulder and rotator cuff tear, and in the patients with mildly contracted shoulder the humeral head moved to the upper direction by means of ball rolling. In the normal subjects no such upward movement of the humeral head was observed. We believe that the restriction of the glenohumeral joint motion and dysfunction of the rotator cuff, which were caused by periarthritis scapulohumeralis, may break down the scapulohumeral rhythm.     

Isokinetic and isometric measurement of strength of external rotation and abduction of the shoulder.

The strength of active external rotation and of abduction of the shoulder when the humerus was in the plane of the scapula (30 degrees of horizontal flexion anterior to the coronal plane) was measured isokinetically and isometrically in thirty-nine normal volunteers, who were stratified by age and sex. The angles at which peak torque was produced were similar when tested isokinetically and isometrically; these angles were similar for external rotation (at 60 and 30 degrees of internal rotation) and for abduction (at 30 and 60 degrees of abduction). Isometric peak torque was greater than slow-speed (90 degrees per second) isokinetic peak torque, which in turn was greater than fast-speed (210 degrees per second) isokinetic peak torque. There were highly significant differences in strength, measured isokinetically and isometrically, between younger and older men and between older men and older women. The variability of normal values for torque was similar in each group. Repeat testing demonstrated a high reliability of isokinetic measurements and of isometric measurements at angles within the range of the production of peak torque. Complete testing was performed in four normal volunteers before and after a block of the suprascapular nerve. The supraspinatus and infraspinatus components of the rotator cuff contributed a variable proportion to the total strength of abduction (25 to 50 per cent) and external rotation (50 to 75 per cent) throughout the range of motion. This study demonstrated that both isokinetic and isometric testing in the scapular plane are valid methods for measurement of the strength of external rotation and abduction of the shoulder. The data support standardization of the positions for testing the strength of motions of the shoulder: isometric strength of external rotation should be measured in the scapular plane with the shoulder in 45 degrees of abduction and 45 degrees of internal rotation; isometric strength of abduction, in the scapular plane with the shoulder in 45 degrees of abduction; and isokinetic strength of external rotation and abduction, in the scapular plane at 90 degrees per second.     

Scapulohumeral rhythm: relationship between motion velocity and rhythm

The relative contributions of scapulothoracic and glenohumeral motion at different rates of shoulder motion were studied through adduction to abduction in the scapular plane. Nineteen shoulders of 10 healthy individuals (all men, 24-30 years of age) were analyzed using an image intensifier and a high-resolution digital video system. High- and low-speed motion consisted of 2 and 4 seconds per one cycle, respectively, from abduction to adduction in the scapular plane. Glenohumeral and scapulothoracic ratios were fixed at low speed and these results agree with the finding of other researchers. Ratios at high speed were not fixed and differed significantly from those at low speed. Ratios were high at the beginning of abduction or adduction and at angles beyond 40 degrees abduction, then decreased according to the arm movement. Glenohumeral motion at high speed was more dominant at the beginning of abduction or adduction beyond the setting phase, then became less dominant according to the arm movement, compared with the motion at low speed.     

Normal and abnormal motion of the shoulder.

The roentgenographic parameters of motion in normal and abnormal shoulders, including the movement of the scapula, arm angle, glenohumeral angle, scapulothoracic angle, excursion of the humeral head, and instant center of motion for abduction in the plane of the scapula, were determined in twelve normal subjects and fifteen patients. The scapula rotated externally with abduction. The ratio of glenohumeral to scapulothoracic movement was 5:4 after about 30 degrees of abduction. The center of rotation of the glenohumeral joint for abduction in the plane of the scapula was located within six millimeters of the geometric center of the humeral ball. The average excursion of the humeral ball on the face of the glenoid in the superoinferior plane between each 30-degree arc of motion was less than 1.5 millimeters in normal subjects. Significant previous injury resulting in abnormal mechanics of the shoulder joint was associated with abnormal values for excursion of the instant center and of the humeral head. An abnormal glenohumeral-to-scapulothoracic ratio was associated with significant pain in the shoulder. The fact that these various parameters were sensitive indicators of normal and abnormal motion raises the possibility of diagnostic clinical application.     

Comparison of In Vivo Three-Dimensional Glenohumeral Positions and Scapular Kinematics between Young and Older Male Groups

BackgroundMany researchers have questioned whether shoulder kinematics such as the glenohumeral position and scapular kinematics would be different in different age groups. However, studies comparing shoulder kinematics between different age groups have been rare. The aim of this study was to analyze and compare the three-dimensional (3D) glenohumeral position, scapular kinematics, and scapulohumeral rhythm (SHR) during scapular plane arm abduction between a normal young male group and a normal older male group.MethodsTwenty normal men (10 young and 10 older) were enrolled in this controlled laboratory study. Fluoroscopic images were obtained using a single plane X-ray system. Bilateral computed tomography scans were taken to create a 3D model. A 3D-2D registration technique was used to determine the 3D position and orientation of the bones of the shoulder.ResultsDuring scapular plane arm abduction, there were significant differences in scapular kinematics between the groups. The older male group showed more upward rotation, posterior tilt, and external rotation than the young male group. On the other hand, the glenohumeral position such as superior inferior translation, anterior posterior translation, and external rotation of the humeral head did not show significant difference between the groups. The mean value of SHR for the overall arm elevation range from start to maximum elevation angle for the older group and young group was 2.298 ± 0.964 and 2.622 ± 0.931, respectively, showing a significant difference between the two groups (p = 0.035).ConclusionsScapular kinematics and SHR were significantly different between the older male group and the young male group. Our study could provide reference values of shoulder kinematics for older men aged 55–65 years.     

肱骨外展动作中肩袖生物力学的有限元分析

目的构建肩关节有限元模型，用于分析肩袖生物力学。 方法采集1名26岁健康男性志愿者右肩CT、MRI数据，构建肩关节有限元模型，包含肩胛骨、肱骨、锁骨，以及肩袖肌群（冈上肌、冈下肌、小圆肌、肩胛下肌）。模拟肱骨在肩胛骨平面外展，分析肩袖肌肉应力变化。 结果肱骨在肩胛骨平面外展0°~30°过程中，各组肌腱与肱骨头连接处的应力均增大。冈上肌腱应力变化速率较快；肩胛骨前方的肩胛下肌对比肩胛骨后方的冈下肌-小圆肌，两组肌腱的应力变化较为同步。当肱骨在肩胛骨平面外展30°时，冈上肌腱、肩胛下肌腱及冈下肌腱-小圆肌腱与肱骨头连接面的平均应力分别为7.894 8、4.721 7、3.768 8 Mpa，冈上肌腱关节面与滑囊面结点平均应力分别为7.931 4、4.099 0 Mpa。冈上肌腱的关节面与滑囊面应力有明显差异，应力差值随肱骨在肩胛骨平面外展而增大，造成的剪切力可造成冈上肌腱撕裂。 结论肩袖对肩关节的活动与稳定性有重要作用，其受力特点易引起肩袖损伤。     

Direct 3-dimensional measurement of scapular kinematics during dynamic movements in vivo.

The purpose of this study was to describe 3-dimensional scapular motion patterns during dynamic shoulder movements with the use of a direct technique. Direct measurement of active scapular motion was accomplished by insertion of 2 1.6-mm bone pins into the spine of the scapula in 8 healthy volunteers (5 men, 3 women). A small, 3-dimensional motion sensor was rigidly fixed to the scapular pins. Sensors were also attached to the thoracic spine (T3) with tape and to the humerus with a specially designed cuff. During active scapular plane elevation, the scapula upwardly rotated (mean [SD] = 50 degrees [4.8 degrees ]), tilted posteriorly around a medial-lateral axis (30 degrees [13.0 degrees ]), and externally rotated around a vertical axis (24 degrees [12.8 degrees ]). Lowering of the arm resulted in a reversal of these motions in a slightly different pattern. The mean ratio of glenohumeral to scapulothoracic motion was 1.7:1. Normal scapular motion consists of substantial rotations around 3 axes, not simply upward rotation. Understanding normal scapular motion may assist in the identification of abnormal motion associated with various shoulder disorders.     

Glenohumeral movements of the involuntary inferior and multidirectional instability

The glenohumeral movements of the involuntary inferior and multidirectional instability were studied by means of cineradiography. Using the devised two parameters, i.e., the shoulder center edge and glenoid angles, the author compared the glenohumeral movements of the normal shoulder with the involuntary inferior and multidirectional instability of the shoulder. The glenohumeral movements of the involuntary inferior and multidirectional instability showed not only an excessive excursion and sliding motion but also a deterioration of the scapular abduction and external rotation, with the arm progressively abducted. These phenomena were especially remarkable at the maximum elevation of the arm. The roentgenogram of the overhead view of the shoulder joint indicates whether or not there is an involuntary inferior and multidirectional instability, and whether or not these parameters can be useful for diagnosis of shoulder lesions.     

Scapular dyskinesis and its relation to shoulder injury

The scapula plays a key role in nearly every aspect of normal shoulder function. Scapular dyskinesis-altered scapular positioning and motion-is found in association with most shoulder injuries. Basic science and clinical research findings have led to the identification of normal three-dimensional scapular kinematics in scapulohumeral rhythm and to abnormal kinematics in shoulder injury, the development of clinical methods of evaluating the scapula (eg, scapular assistance test, scapular retraction test), and the formulation of rehabilitation guidelines. Primary scapular presentations such as scapular winging and snapping should be managed with a protocol that is focused on the scapula. Persons with associated conditions such as shoulder impingement, rotator cuff disease, labral injury, clavicle fracture, acromioclavicular joint injury, and multidirectional instability should be evaluated for scapular dyskinesis and treated accordingly.     

Dynamic analysis of the shoulder girdle muscles during tracking movements in the scapular plane and in the sagittal plane--an electromyographic study

Analyse were made of electromyograms from the upper trapezius, middle deltoideus, supraspinatus and infraspinatus during tracking movements in the scapular plane and the sagittal plane of ten males. The purpose was to determine electromyographically how these muscles act in various phases and speeds of the shoulder movements in those planes. The middle deltoideus and the supraspinatus showed significantly greater electrical activity with a shoulder motion in the scapular plane than in sagittal plane having a higher efficiency in the scapular plane. There was no change observed in the electrical activity of the infraspinatus, whatever the speed or direction of the shoulder movements was. The upper trapezius seemed to play an important role in the fast scapulohumeral rhythm. The middle deltoideus played a similar important role in the slow rhythm and the supraspinatus was important in both fast and slow rhythms.     

The influence of handheld weight on the scapulohumeral rhythm

Scapulohumeral rhythm (SHR) provides insight to neuromuscular control and fundamental biomechanics of the shoulder. This rhythm often is disrupted in pathologic shoulders. As the first step, we sought to quantify SHR in healthy subjects for diagnostic assessment of shoulder function. Ten healthy shoulders were studied. Three-dimensional models of the humerus and scapula were created from computed tomography scans. Dynamic shoulder motion was recorded by use of single-plane fluoroscopy during arm abduction with 0-kg and 3-kg handheld loads. Shoulder kinematics were quantified by use of model-based 3-dimensional-to-2-dimensional registration techniques. SHR decreased (more scapular motion) with increasing abduction. With a 3-kg load, scapulothoracic motion was significantly reduced through the range of 35 degrees to 45 degrees of glenohumeral motion. Muscular stabilization of the scapula increased with external loading, as shown by decreased SHR during early lifting. Dynamic scapular stabilization provides a critical platform for upper extremity activity.     

Influence of humeral prosthesis height on biomechanics of glenohumeral abduction. An in vitro study

BACKGROUND: During shoulder replacement surgery, the normal height of the proximal part of the humerus relative to the tuberosities frequently is not restored because of differences in prosthetic geometry or problems with surgical technique. The purpose of the present study was to determine the effect of humeral prosthesis height on range of motion and on the moment arms of the rotator cuff muscles during glenohumeral abduction. METHODS: Tendon excursions and abduction angles were recorded simultaneously in six cadaveric specimens during passive glenohumeral abduction in the scapular plane. Moment arms were calculated for each muscle by computing the slope of the tendon excursion-versus-glenohumeral abduction angle relationship. The experiments were carried out with the intact joint and after replacement of the humeral head with a prosthesis that was inserted in an anatomically correct position as well as 5 and 10 mm too high. RESULTS: Insertion of the prosthesis in positions that were 5 and 10 mm too high resulted in significant and marked reductions of the maximum abduction angle of 10 degrees (range, 5 degrees to 18 degrees ) and 16 degrees (range, 12 degrees to 20 degrees ), respectively. In addition, the moment arms of the infraspinatus and subscapularis decreased by 4 to 10 mm. This corresponded to a 20% to 50% decrease of the abduction moment arms of the infraspinatus and an approximately 50% to 100% decrease of the abduction moment arms of the subscapularis, depending on the abduction angle and the part of the muscle being considered. CONCLUSIONS: If a humeral head prosthesis is placed too high relative to the tuberosities, shoulder function is impaired by two potential mechanisms: (1) the inferior capsule becomes tight at lower abduction angles and limits abduction, and (2) the center of rotation is displaced upward in relation to the line of action of the rotator cuff muscles, resulting in smaller moment arms and decreased abduction moments of the respective muscles. Clinical Relevance: In patients managed with shoulder replacement surgery, limitation of range of motion, loss of abduction strength, and overload with long-term failure of the supraspinatus tendon are potential consequences of positioning the humeral head of the prosthesis proximal to the anatomic position.     

Functional recovery after a reverse prosthesis for reconstruction of the proximal humerus in tumor surgery

An alternative treatment for primary bone tumors of the proximal humerus was assessed. Four patients, who made full functional recovery after complete resection of the proximal humerus inclusive of the rotator cuff and subsequent reconstruction with a reverse shoulder prosthesis, were examined clinically and radiographically. Distinct medialization of the center of rotation of the glenohumeral joint (28 mm) and elongation of the remaining deltoid muscle (116%) were measured. Increased scapular rotation (118%) was observed. The radiologic results and thoracoscapular rhythm analyses were implemented in a three-dimensional computerized model of the glenohumeral joint. This allowed us to calculate a doubling of the moment of the deltoid abductor muscle in the true scapular plane. After tumor surgery, in which the proximal humerus is resected without reinserting the rotator cuff, full functional recovery of the shoulder can be obtained with a total shoulder prosthesis, medializing the glenohumeral center of rotation and elongating the remaining deltoid muscle. Level of Evidence: Therapeutic study, Level IV (case series-no, or historical control group).     

Shoulder electromyography in multidirectional instability

We studied shoulder muscle activity in multidirectional instability (MDI) and multidirectional laxity (MDL) of the shoulder, our hypothesis being that altered muscle activity plays a role in their pathogenesis. Six muscles (supraspinatus, infraspinatus, subscapularis, anterior deltoid, middle deltoid, and posterior deltoid) were investigated by use of intramuscular dual fine-wire electrodes in 7 normal shoulders, 5 MDL shoulders, and 6 MDI shoulders. Each subject performed 5 types of exercise (rotation in neutral, 45 degrees of abduction, 90 degrees of abduction, flexion/extension, and abduction/adduction) on an isokinetic muscle dynamometer at two rates, 90 degrees /s and 180 degrees /s. After filtering, rectification, and smoothing, the electromyography signal was normalized by using the peak voltage of the movement cycle. In subjects with MDI, compared with normal subjects, activity patterns of the anterior deltoid were different during rotation in neutral and 90 degrees of abduction, whereas those of the middle and posterior deltoid were different during rotation in 90 degrees of abduction. In subjects with MDL, the posterior deltoid showed increased activity compared with normal subjects during adduction. Activity patterns of the supraspinatus, infraspinatus, and subscapularis appeared similar in both groups. Dual fine-wire electromyography offers insight into the complex role of shoulder girdle muscle function in normal movement and in instability. Altered patterns of shoulder girdle muscle activity and imbalances in muscle forces support the theory that impaired coordination of shoulder girdle muscle activity and inefficiency of the dynamic stabilizers of the glenohumeral joint are involved in the etiology of MDI. Interestingly, the abnormalities are in the deltoid rather than the muscles of the rotator cuff.     

Shoulder kinematics with two-plane x-ray evaluation in patients with anterior instability or rotator cuff tearing

The goals of this study were to define biplanar glenohumeral kinematics and glenohumeral-scapulothoracic motion relationships in normal patients with a two-plane radiograph series and then in patients with anterior shoulder instability or rotator cuff tear both before surgery and after surgical repair and postoperative rehabilitation. A two-plane radiographic series of x-ray films in the scapular and horizontal (axillary) planes was performed. With these films, measurements of the relationship between the centers of the humeral head and glenoid and measurements of the component contributions of glenohumeral and scapulothoracic motion to total arm abduction were made. Six normal adults underwent x-ray evaluation to establish normal control values. Kappa analysis was used to determine reliability of technique. Eighteen patients with confirmed anterior shoulder instability (group A) and 15 with confirmed rotator cuff tears (group B) were studied before surgery. Seven (39%) of 18 of the patients in group A and all 15 (100%) of the patients in group B demonstrated superior translation of the humeral head during scapular plane abduction. In the horizontal plane 14 (78%) of 18 patients in group A (instability) and none in group B (rotator cuff tear) demonstrated abnormal anterior translation of the humeral head on the glenoid. Both groups demonstrated altered glenohumeral-scapulothoracic motion relationships compared with the normal control group. Two years after surgery 12 patients from group A and 14 patients from group B were restudied. All of these patients had demonstrated abnormalities of humeral head translation before surgery. For group A 12 (100%) of 12 patients demonstrated normal glenohumeral kinematics in both planes after open anterior stabilization. For group B 12 (86%) of 14 patients demonstrated normal glenohumeral kinematics in both planes after open rotator cuff repair. In group A the altered glenohumeral-scapulothoracic motion relationships persisted, whereas in group B these relationships became normal.     

Scapulocostal stabilization for scapular winging in facioscapulohumeral muscular dystrophy

A surgical procedure has been devised to prevent scapular winging and to increase shoulder abduction in facioscapulohumeral muscular dystrophy. The operation improves the limited shoulder abduction and scapular winging caused by the loss of scapular fixation to the thoracic cage, while passive abduction at the glenohumeral joint remains normal. Preventing scapular malrotation by eliminating scapulothoracic motion increases shoulder abduction. This is achieved by fastening the scapula to several underlying ribs with fascia. The operation has resulted in a 37 per cent increase in abduction, increased shoulder strength and endurance, and the prevention of scapular winging.     

Shoulder rhythm in patients with impingement and in controls: Dynamic RSA during active and passive abduction

Background and purpose Impingement syndrome is probably the most common cause of shoulder pain. Abnormal abduction and proximal humeral translation are associated with this condition. We evaluated whether the relative distribution between glenohumeral and scapular-trunk motions (the scapulohumeral rhythm) and the speed of motion of the arm differed between patients with impingement and a control group without shoulder symptoms.Patients and methods 30 patients with shoulder impingement (Neer stage 2) and 11 controls were studied during active abduction and 21 patients and 9 controls were studied during passive abduction. Dynamic RSA at a speed of 2 simultaneous exposures per second was used to record the shoulder motions for 5–6 seconds.Results Within the interval statistically evaluated (observations between 20–55° of relative active abduction in the glenohumeral joint), the patient group showed more scapular and trunk motions (p = 0.04), especially at up to 40°. The pattern of motion at passive abduction was somewhat similar to that in the controls.Both controls and patients showed an increasing absolute (i.e. global) proximal displacement of the center of the humeral head with increasing active and passive abduction of the glenohumeral joint and humerus, without any certain difference between the groups. The mean maximum absolute proximal displacement in the patient and control groups amounted to about 30 mm and 20 mm, respectively. The corresponding relative displacement (with fixed scapula) was only 2.0 and 0.5 mm.Active abduction was initiated with angular velocity of about 50 and 80 degrees per second, respectively, in the patients and the controls. In both groups it decreased with progressing abduction down to about 20 degrees per second (controls) after 3 seconds without there being any statistically significant difference. The angular velocities at passive abduction showed a similar pattern, still without any difference.In both groups, the speed of proximal translation during active abduction peaked 0.5–1 second later than the speed of rotation and remained relatively even for about 1 second, followed by a deceleration.Interpretation We found that the glenohumeral-thoracoscapular ratio during abduction of the arm in our study, measured as the distribution of motion between the glenohumeral joint and the trunk in both controls and patients with impingement, was less than or equal to 1:1. This finding differs from earlier results, probably due to the use of a method with high resolution and small influence of motions out of the frontal plane. The reason for reduced glenohumeral motions in the early phase of active abduction in the patient group is uncertain, but pain or avoidance of pain elicited by the motion was probably of importance.     

Effective rehabilitation in patients with scapular dyskinesis

For a balanced scapulohumeral rhythm in arm elevation, it is necessary to have an optimal position, motion, stability and muscle performance of the scapula and scapular muscles. In the case of abnormal movements, so-called scapular dyskinesis, the tendons (e.g. biceps tendon, rotator cuff) can be irritated and may cause pain in overhead activity. There are various causes for scapular dyskinesis and, therefore, the treatment is a challenge for therapists. The aim of conservative treatment is to restore normal position and movement of the scapula and furthermore dynamic scapular stability during overhead activities. Rehabilitation based on effective exercises should be tailored individually and the complexity of the exercises should be increased slowly.     

Determination of in vivo glenohumeral translation using fluoroscopy and shape-matching techniques

The purpose of this study was to investigate glenohumeral translation in-vivo during active shoulder abduction in the scapular plane. Three-dimensional (3D) models of 9 shoulders were created from CT scans. Fluoroscopic views aligned to the plane of the scapula were recorded during active arm abduction with neutral rotation. 3D motions were determined using model-based 3D-to-two-dimensional (2D) registration. Humeral translation was referenced to the glenoid center in the superior/inferior direction. The humerus moved an average of 1.7 mm superior with arm abduction, from an inferior location to the glenoid center. The humeral head was centered within 1 mm from the glenoid center above 80 degrees abduction. Variability in glenohumeral translation between shoulders decreased significantly from initial to final arm abduction. Our findings agree with some authors' observations of inferior-to-central translation of the humerus and behavior as a congruent ball and socket. We believe this information will help improve the understanding of shoulder function.     

Contemporary use of reverse total shoulder arthroplasty

Reverse total shoulder arthroplasty (RTSA) has evolved as the treatment for glenohumeral joint disease in patients with rotator cuff pathology because it allows for the deltoid to be further recruited during abduction. Surgical procedure for an RTSA can be done via two approaches, deltopectoral and superolateral. The most commonly reported complications include infection, dislocation, humeral fracture, glenoid fracture, hematoma, neurological damage, implant loosening, and scapular notching. The RTSA has become prominent in the treatment of shoulder pathology due to its ability to treat a gamut of complex disorders, while awarding pain relief and enhanced functional range of motion.