Normal Shoulder Function Research Articles

Which is the Optimal Exercise to Strengthen Supraspinatus?

Supraspinatus strengthening is an important part of shoulder rehabilitation programs. Because of the force-couple relationship between supraspinatus and deltoid during shoulder abduction, it has been proposed that the optimal exercise to strengthen supraspinatus is one that would maximize supraspinatus activity while minimizing surrounding muscle activity, particularly deltoid. The aim of this study was to simultaneously examine all exercises known to recruit supraspinatus at high levels and to compare the level of recruitment in supraspinatus, deltoid, and infraspinatus. Using a combination of surface and intramuscular electrodes, EMG recordings were taken from supraspinatus, infraspinatus, and the three parts of deltoid of 15 subjects with normal dominant shoulder function during maximal isometric contractions in "empty can," "full can," prone elevation, pendant external rotation, and prone external rotation exercise positions. There was no significant difference in the level of supraspinatus activation for all exercise positions examined. No significant difference was found in activation levels across all muscles during the "can" exercise positions. The exercise positions using external rotation were found to activate parts of deltoid significantly less than the "can" and prone elevation positions. Infraspinatus was activated at greater levels than supraspinatus during the external rotation exercises. Using the criteria that the optimal exercise to strengthen supraspinatus should maximize supraspinatus activity while particularly minimizing deltoid activity, this study has shown that the pendant external rotation and prone external rotation exercises are more valid than the "can" and prone elevation exercises for supraspinatus strengthening in subjects with normal dominant shoulder function.

Anatomy and Mechanics of the Shoulder: Review of Current Concepts

This narrative review is intended to provide hand and upper extremity therapists, who occasionally treat patients with shoulder diagnoses, with several current concepts related to normal shoulder anatomy and function. It is hoped that this review will be useful for 1) appreciating patho-anatomy and pathophysiology, 2) planning treatment approaches, and 3) stimulating research aimed at improved understanding of the shoulder.

Return of Shoulder Girdle Function After Anterior Versus Posterior Adolescent Idiopathic Scoliosis Surgery

Multicenter, prospective, cohort study. To compare minimum 2-year postoperative shoulder function after 3 different surgical approaches for the treatment of primary thoracic curves in patients with adolescent idiopathic scoliosis (AIS). Thoracic spinal instrumentation and fusion can be performed via posterior (PSF), open anterior (OASF), or thoracoscopic anterior (TASF) techniques. Although the morbidity of these 3 surgical approaches is beginning to be understood, no reports have been published comparing 2-year postoperative shoulder strength and range of motion. AIS patients who underwent selective fusion of primary thoracic curves were studied. Right-sided shoulder strength (flexion, abduction) and range of motion (flexion, extension, abduction) measurements were collected prospectively at selected intervals. An arbitrary threshold (80% of preoperative value) was defined as postoperative return of normal shoulder function. Univariate analysis of variance (P < 0.05) was used to compare differences in shoulder function for the 3 approaches at each postoperative time-point. Ninety-two patients with minimum 2-year postoperative shoulder function data were included in this study (24 PSF, 32 OASF, and 36 TASF). On average, patients who had an OASF failed to reach the 80% threshold for right shoulder forward flexion and abduction strength until 1-year and 6-months after surgery, respectively; whereas patients that had a TASF or PSF returned to normal shoulder strength by the 3-month follow-up visit. With regards to ROM, patients in all 3 groups surpassed the 80% preoperative threshold for right shoulder active forward flexion and extension by the 6-week visit, with no clinically significant differences between the groups. However, for active abduction range of motion, patients that had an OASF required 3-months to regain 80% of their preoperative motion, compared to 6-weeks for patients in both the TASF and PSF groups. Approach-related differences in shoulder morbidity do exist in the treatment of primary thoracic curves in AIS. Specifically, OASF imparts a significantly greater magnitude and duration of postoperative shoulder dysfunction than do the TASF or PSF approaches. Nonetheless, these negative effects are transient as shoulder function in those patients treated via an open thoracotomy normalized by the 1-year postoperative time-point at the latest. Accordingly, viewed in isolation, shoulder morbidity should not deter surgeons from using an open anterior approach in the surgical treatment of AIS.

In vivo articular cartilage contact at the glenohumeral joint: preliminary report

BackgroundLittle is known about normal in vivo mechanics of the glenohumeral joint. Such an understanding would have significant implications for treating disease conditions that disrupt shoulder function. The objective of this study was to determine articular contact locations between the glenoid and humeral articular surfaces in normal subjects during shoulder abduction with neutral, internal, and external rotations. We hypothesized that glenohumeral articular contact is not perfectly centered and is variable in normal subjects tested under physiological loading conditions. MethodsOrthogonal fluoroscopic images and magnetic resonance image-based computer models were used to characterize the centroids of articular cartilage contact of the glenohumeral joint at various static, actively stabilized abduction and rotation positions in five healthy shoulders. The shoulder was investigated at 0°, 45°, and 90° abduction with neutral rotation and then at 90° abduction combined with active maximal external rotation and active maximal internal rotation. ResultsFor all the investigated positions, the centroid of contact on the glenoid surface for each individual, on average, was more than 5 mm away from the geometric center of the glenoid articular surface. Intersubject variation of the centroid of articular contact on the glenoid surface was observed with each investigated position, and 90° abduction with maximal internal rotation showed the least variability. On the humeral head surface, the centroids of contact were located at the superomedial quarter for all investigated positions, except in two subjects’ positions at 0° abduction, neutral rotation. ConclusionsThe data showed that the in vivo glenohumeral contact locations were variable among subjects, but in all individuals they were not at the center of the glenoid and humeral head surfaces. This confirms that “ball-in-socket” kinematics do not govern normal shoulder function. These insights into glenohumeral articular contact may be relevant to an appreciation of the consequences of pathology such as rotator cuff disease and instability.

Surgical Management of Type IV SLAP Lesions (SS-13)

Repair of type II SLAP lesions has been shown to be effective in numerous studies. Repair of type IV SLAP lesions has been more controversial. Repair would allow theoretical preservation of the biceps anchor, and more normal shoulder function. This represents the first report outlining the outcome of repair of type IV SLAP lesions. Twenty-five patients had isolated type IV SLAP lesions which were repaired and followed for at least two years. Lesions which split directly vertically into the biceps in a red-on-red pattern were repaired side to side using multiple PDS sutures. Lesions which presented with a white-on–white bucket handle portion were treated with excision of the bucket and the repair of the remaining biceps anchor to bone. Patients were immobilized in a sling for three weeks, and then started on active assisted range of motion. No complications occurred. Two patients were reoperated for persistent pain and treated successfully with biceps tenodesis; both had labral excision and repair with loss of 30% or greater of the biceps substance. Primary repair provided good to excellent results in most patients, with improvement in UCLA scores from 18 to 31.7 and ASES scores from 66 to 91. Second-look data was available for two patients in this group, showing solid healing. Repair of type IV SLAP lesions can be anticipated to be successful provided no more than 30% of the biceps root is compromised by the injury; arthroscopic biceps tenodesis will provide a more predictable outcome for these patients.

Asymptomatic anterior shoulder dislocation of 24-year duration

A 73-year-old woman presented with a very long-standing anterior dislocation of her right shoulder. She had no pain, mild impairment of active shoulder motion and clinical features suggesting no tear of the rotator cuff. CT 3D reconstructions showed a newly formed glenoid cavity below the coracoid process. This case indicates that an anterior shoulder dislocation lasting even decades may be compatible with an almost normal shoulder function.

In vivo glenohumeral contact forces—Measurements in the first patient 7 months postoperatively

Knowledge of forces in the glenohumeral joint is essential for understanding normal and pathologic shoulder function. It forms the basis for performing fracture treatment or joint replacement surgery, for optimizing implant design and fixation and for improving and verifying analytical biomechanical models of the shoulder. An instrumented shoulder implant with telemetric data transmission was developed to measure six components of joint contact forces and moments. A patient with humeral head arthrosis achieved good joint function after its implantation. During the first 7 postoperative months, the contact force remained below 100% BW (percent body weight) for most activities of daily living. It ranged up to 130% BW for arm positions close to the limits of motion or when acting against external resistance. When the patient tried to turn a blocked steering wheel with maximum effort, the force rose to about 150% BW, the highest level observed thus far. Of great interest were the force directions relative to the humerus, especially those in the sagittal plane, which were not greatly influenced by the type of exercise, the arm position or the external resistance. The moments due to friction in the joint reached 5.2 N m. The friction-induced shift of contact forces relative to the implant head centre ranged up to 6.3 mm. These first worldwide in vivo measurements of glenohumeral contact forces are being continued in more patients and for longer postoperative times.

Scapulothoracic and Glenohumeral Kinematics Following an External Rotation Fatigue Protocol

Repeated-measures experimental design. To determine the effects of shoulder external rotator muscle fatigue on 3-dimensional scapulothoracic and glenohumeral kinematics. The external rotator muscles of the shoulder are important for normal shoulder function. Impaired performance of these muscles has been observed in subjects with impingement syndrome and it is possible that external rotator muscle fatigue leads to altered kinematics of the shoulder girdle. Twenty subjects without a history of shoulder pathology participated in this study. Three-dimensional scapulothoracic and glenohumeral kinematics were determined from electromagnetic sensors attached to the scapula, humerus, and thorax. Surface electromyographic (EMG) data were collected from the upper and lower trapezius, serratus anterior, anterior and posterior deltoid, and infraspinatus muscles. Median power frequency (MPF) values were derived from the raw EMG data and were used to indicate the degree of local muscle fatigue. Kinematic and EMG measures were collected prior to and immediately following the performance of a shoulder external rotation fatigue protocol. After completing the fatigue protocol subjects demonstrated less external rotation of the humerus. Additionally, they had less posterior tilt of the scapula in the beginning phase of arm elevation, and more scapular upward rotation and clavicular retraction in the mid ranges of arm elevation. Performance of an external rotation fatigue protocol results in altered scapulothoracic and glenohumeral kinematics. Further studies are needed to investigate the effects of external rotator muscle fatigue on scapulothoracic and glenohumeral kinematics in subjects with shoulder pathology.

Shoulder muscle recruitment patterns during a kayak stroke performed on a paddling ergometer

Precise muscle co-ordination is required to maintain normal shoulder function and alterations in synchrony between shoulder muscles can result in loss of full range of movement and pain. Although shoulder pain in kayakers is high with 53% of elite international paddlers reporting shoulder injuries, little information is available regarding the pattern of shoulder muscle recruitment during paddling. The aim of this study was to investigate the normal recruitment pattern of shoulder muscles during the kayak stroke. Nine recreational paddlers without shoulder pain were examined. EMG data from eight shoulder muscles of the dominant arm were collected simultaneously with video data during simulated paddling on an ergometer. EMG data was normalized to time and peak amplitude. Intersubject consistency was evaluated using Pearson correlation analysis. The results of this study indicated a fair to high correlation in at least one phase of the kayak stroke in five of the muscles examined: upper trapezius, supraspinatus, latissimus dorsi, serratus anterior and rhomboid major. This normative data will enable comparisons with the shoulder muscle recruitment patterns in kayakers with shoulder pain in order to determine the role of altered motor control in the painful kayaking shoulder.

Results of early operative treatment of rotator cuff tears with acute symptoms

The distinction among an acute tear, acute symptoms of a chronic tear, or the acute extension of an existing chronic tear is very difficult, if not impossible, to make. In general, operative treatment of lesions with a sudden onset has yielded favorable results in many studies. However, the timing of the operation for tears with an acute onset of symptoms is still a very controversial issue, as are the treatment options for chronic tears with acute symptoms. This study analyzes the follow-up results of early operative treatment of rotator cuff tears with an acute onset of symptoms, regardless of tear type. Twenty-nine patients with a sudden onset of symptoms and significant impairment of shoulder function had a full-thickness rotator cuff tear. The patients were operated on within 3 weeks from the beginning of the symptoms. Twenty-six patients underwent follow-up. The results were evaluated by use of the UCLA shoulder rating scale. At follow-up, 22 patients (85%) had no pain and 21 (81%) had returned to normal activities and had normal shoulder function. Active forward flexion averaged 51 degrees preoperatively and 167 degrees at follow-up. After repair of the tear, shoulder strength was normal in 22 of 26 shoulders (85%); 3 patients had fair strength, all after repair of a massive tear. Of the patients, 25 (96%) were satisfied with the result. The overall result was excellent in 20 patients (77%), good in 4 (15%), fair in 1 (4%), and poor in 1 (4%). Early operative treatment appears to be better for rotator cuff tears with a sudden onset of symptoms and poor function to achieve maximal return of shoulder function. With time, the tear may enlarge, and the cuff may lose its elasticity, thus making the late surgical repair more difficult or even impossible.

Elastisch stabile intramedulläre Nagelung (ESIN) von Klavikulaschaftfrakturen — Wandel eines Therapiekonzeptes?

Midshaft fractures of the clavicle are mostly treated conservatively. For the few cases in which stabilisation is needed, open reduction and plate fixation is the standard procedure. We report a minimally invasive technique of intramedullary stabilisation using a titanium nail carried out in 35 markedly displaced midclavicular fractures. Twelve fractures were simple and 23 consisted of more than two fragments. A total of 62.9% (22/35) of the patients presented additional injuries; 37.1% (13/35) with additional fractures. There were four ipsilateral scapular neck fractures. In 74.3% (26/35) of patients closed reduction was possible, whereas nine fractures required open reduction before the nail inserted from the sternal end of the clavicle could be introduced into the peripheral fragment. All fractures healed clinically and radiologically within 6 weeks. In contrast to conservatively treated fractures, length discrepancies of 1 cm or more, mainly shortening, could be avoided. Using a visual analog scale, significant pain relief (8.4-2.4 points) was already recorded on the first day after surgery. Patients with an isolated fracture of the clavicle showed a nearly normal range of motion only 1 week after surgery, whereas patients with associated scapular or rib fractures needed up to 3 weeks to reach normal shoulder function. No patient complications requiring interventional procedures occurred. Minimally invasive, elastic, stable intramedullary nailing of midshaft fractures of the clavicle should be recommended as an alternative to conservative treatment because of early pain relief, associated rapid functional recovery and anatomical restoration of the clavicle.

Glenohumeral interposition of a torn rotator cuff in a young motorcyclist

This report describes the rare case of a traumatic rotator cuff tear in a young patient which led to a pseudo-paralyzed shoulder by interposition of the tendon stump into the glenohumeral joint. The patient underwent an open rotator cuff repair and regained an almost normal shoulder function after 12 weeks. A review of the literature is presented.

Shoulder and Elbow Injuries in the Skeletally Immature Athlete

The intensity of training and competition among young athletes can place them at increased risk of acute and chronic injuries, which occur in patterns unique to the skeletally immature athlete. Prompt recognition and treatment of these injuries are critical to prevent long-term functional disability and deformity. Children and adolescents participating in recreational and organized sports are particularly susceptible to a broad spectrum of shoulder and elbow injuries involving both osseous and soft-tissue structures. Understanding the relevant functional anatomy, biomechanics of throwing, and pathophysiology of injury can help the clinician manage common acute traumatic injuries, some of which may result in chronic problems. Over-use injuries occur more frequently than do acute, traumatic injuries, and early recognition, coupled with appropriate treatment or prevention, can help restore and maintain normal shoulder and elbow function.

Long-term outcome of a proximal humerus fracture predicted after 1 year

Background Earlier reports of results after proximal humerus fractures have often been short- or medium-term studies. The aim of this investigation was to follow an unselected group of patients prospectively and assess the long-term results in relation to fracture type and health, and to evaluate the possibility of predicting the long-term results after 1 year.Method 258 consecutive urban patients who sustained a proximal humerus fracture in 1987 were followed prospectively and examined after 1 and 13 years. 158 patients had died by the year 2000 and 47 of the surviving patients were available for clinical and radiographic evaluation. The Constant-Murley score (CM-score) was used in the clinical assessment. In the final follow-up group, all patients except 1 were treated non-operatively.Results 21 patients had asymptomatic, pain-free shoulders. In 26 patients with shoulder symptoms, 11 had severe pain and 10 had moderate pain, and only 2 of these 21patients had normal shoulder function. The remaining 5 patients in the symptomatic group had no shoulder pain but had reduced shoulder function. Shoulders with a displaced fracture and also injured shoulders of patients with a chronic disease were significantly worse at the long-term follow-up. The 1-year examination had been able to predict the long-term results with 71% sensitivity for protracted pain and 88% sensitivity for persistent shoulder dysfunction.Interpretation Our results suggest that there is a substantial mortality in patients with a proximal humerus fracture, as we have previously reported, and that surviving patients frequently have persistent symptoms that can be predicted as early as after 1 year.

Normalization procedures using maximum voluntary isometric contractions for the serratus anterior and trapezius muscles during surface EMG analysis

The serratus anterior and trapezius muscles are considered to be the only upward rotators of the scapula and are very important for normal shoulder function. A variety of methods have been used to produce a maximum voluntary isometric contraction (MVIC) of these muscles for normalization of EMG data. The purpose of this study was to quantify the surface EMG activity of the serratus anterior muscle and the upper, middle, and lower parts of the trapezius during 9 manual muscle tests performed with maximum effort in 30 subjects. It was found that no one muscle test produced a MVIC for all individuals. Therefore, to perform normalization within each subject, it is suggested that the 2 or 3 tests identified in this study that produce high levels of EMG activity for each muscle be performed. The scapular protraction muscle test that is often used to normalize data for the serratus anterior muscle produced relatively low levels of EMG activity and was not found to be an optimal test. Muscle tests in which an attempt was made to de-rotate the scapula from an upwardly rotated position produced much higher levels of EMG activity in the serratus anterior muscle.

Influence of age on scapulo-thoracic orientation

Background. Scapular activity during shoulder motion is critical for normal shoulder function. With aging, muscle function deteriorates in almost all people, which may lead to shoulder impingement syndrome. Methods. Forty-four normal subjects, 23 men and 21 women aged from 16 to 73 years with a mean age 48, were enrolled in the study. Static antero-posterior radiography at both 0° and 90° of abduction were undertaken and correlation between age and scapular orientations were evaluated by Pearson’s correlation coefficient test. The purpose of this study is to investigate the relationship between aging and scapulo-thoracic orientation. Findings. Significant correlation coefficients were observed between aging and scapular orientations. With the shoulder at 0° abduction, posterior tilt showed significant negative correlation with aging. At 90° abduction, both posterior tilt and upward rotation angle correlated negatively with aging. The correlation was apparent at 90° abduction. Interpretation. The results indicate that shoulder aging closely relates to changes of scapular orientation, which consist of decreases of the posterior tilt at 0° and 90° abduction and the upward rotation angle at 90°. The current study indicated that one of the effects of aging on the shoulder is a decrease of posterior tilt and upward rotation angle as seen in an abducted position; and that these alterations are similar to the scapular kinematics of shoulder impingement syndrome. By taking this concept into consideration, the effects of aging on shoulder kinematics can be appropriately evaluated.

Gentle thawing of the frozen shoulder: A prospective study of supervised neglect versus intensive physical therapy in seventy-seven patients with frozen shoulder syndrome followed up for two years

Seventy-seven patients with idiopathic frozen shoulder syndrome were included in a prospective study to compare the effect of intensive physical rehabilitation treatment, including passive stretching and manual mobilization (stretching group) versus supportive therapy and exercises within the pain limits (supervised neglect group). There were no significant differences in age, sex, time elapsed since onset, and disease severity at inclusion. All patients were followed up for 24 months after the start of treatment. In the patients treated with supervised neglect, 89% had normal or near-normal painless shoulder function (Constant score ≥80) at the end of the observation period. This end result was reached by 64% within 12 months. In contrast, of the group receiving intensive physical therapy treatment, only 63% reached a Constant score of 80 or higher after 24 months. Both the level of the Constant score at the end of the study and the moment a Constant score of 80 or higher was reached confirm that supervised neglect yields better outcomes than intensive physical therapy and passive stretching in patients with frozen shoulder.

Muscle transfers for irreparable rotator cuff tears

Abstract Muscle transfers can yield favorable clinical results in selected patients with irreparable rotator cuff tears. For anterior superior cuff tears the sternocostal portion of the pectoralis under the conjoined tendon is the author’s preferred technique. For the posterior superior cuff tear the latissimus dorsi transfer is preferred. The transfers often provide improvement in function and pain but do not restore normal shoulder function.

Consequences of deltoid muscle elongation on deltoid muscle performance: a computerised study

Background. The deltoid muscle plays an important role in normal shoulder function. Knowledge of the position of the glenohumeral rotational centre and of the deltoid muscle length is essential to understand optimal placement of a total shoulder prosthesis. Objective. This study is designed to analyse the effect of deltoid muscle elongation on shoulder joint function. Design. A three-dimensional model of the glenohumeral joint with deltoid muscle analysis in the scapular plane. Methods. A geometrical three-dimensional ball-and-socket model of the shoulder joint was developed. From dry bones, the position of the origins and insertions of the three parts of the deltoid muscle relative to the calculated centre of rotation of the humeral head was defined. The position and the direction of the muscle force working lines relative to this humeral centre were calculated using former measurements and CT-data of the deltoid. Muscle length–tension data were applied to obtain angle–force relationships. The model was used to calculate the angle–force relationships, the moment arm and the moment of the deltoid muscle components for successive arm elevation angles in the scapular plane. These data were compared to those of a theoretical situation assuming a 10% elongation of the muscle. Results. Muscle angle–force curves show a more favourable slope after moderate (10%) deltoid muscle elongation. Elongating the muscle by changing the distance between the humeral rotation point and the deltoid insertion along the humeral axis does not affect moment arms. The moments of the deltoid muscle forces themselves, however, seem more adapted to elevation in the scapular plane. The deltoid maximal moment exceeds the arm-weight moment by about 40% instead of being approximately equal, and that the maximum is situated around 100° of elevation. Conclusions. From a biomechanical point of view, stretching the deltoid muscle by 10% seems to result in a significantly more favourable position in case of shoulder elevation at 90° of abduction in the scapular plane in a centred glenohumeral joint. Relevance This model suggests that a 10% elongation of the deltoid muscle, the most important shoulder abductor, improves its ability to elevate the arm. If properly implemented, this observation can be very important in the treatment and early rehabilitation of rotator-cuff-insufficient shoulders treated by a specific total shoulder replacement design.

Rehabilitation of the shoulder after rotator-cuff repair

Normal shoulder function requires a balanced relationship between glenohumeral mobility and glenohumeral stability. Restoration of shoulder function following an injury or surgery requires an appropriately outlined physical therapy program directed by the treating physician. Rehabilitation of the shoulder following a rotator cuff repair is variable and is dependent not only on the qualityof the repair, but also on the tear size and extent of medial retraction. The first phase of therapy focuses on pain control, restoration of motion within specific guidelines while preserving the integrity of the repair. When tendon healing is complete, active motion exercises are instituted. Strengthening exercises are added during the third phase of therapy, and functional strengthening is instituted prior to a return to full activity. It is important that the operating physician is intimately involved with creating the rehabilitation protocol of each patient and that there is an open line of communication between the physician, patient, and therapist.