Mechanics of glenohumeral instability

The glenohumeral joint is designed for mobility and is normally lax. It is stabilized in its midrange by its limited joint volume and concavity-compression. It is stabilized at the extremes of motion by its ligaments. An enhanced understanding of these stabilizing mechanisms helps us in the diagnosis and management of glenohumeral instability.     

Shoulder MRI after surgical treatment of instability.

OBJECTIVE: To analyze magnetic resonance imaging (MRI) findings of the shoulder after an instability operation. MATERIALS AND METHODS: Physical examinations, radiographs and MRI of 10 patients after anterior glenoid bone block insertion for ventral instability were compared. MRI included T1-weighted spin-echo (TR = 600, TE = 20 ms) and T2*-weighted gradient-echo sequences (TE = 600, TE = 18, Flip = 30 degrees) in the axial, oblique-coronal and oblique-sagittal planes. RESULTS: No patient suffered from recurrent subluxation. We found fusion of the bone block with the anterior glenoid in seven cases, dislocation of the bone block without contact to the glenoid in one case, and no visible bone block in two cases. On MRI, the bone block showed either signal intensity equivalent to fatty bone marrow (n = 4) or was devoid of signal consistent with cortical bone or bone sclerosis (n = 4). In all patients, a low signal intensity mass, 2-4 cm in diameter, was visible next to the glenoid insertion site. CONCLUSION: Insertion of a bone block onto the anterior glenoid induces formation of scar tissue, increasing the stability of the shoulder joint. This scar is well visible on MRI and forms independently of the behavior of the bone block itself. MRI is ideally suited for evaluating postoperative shoulder joints after bone-grafting procedures.     

Arthroscopic management of glenohumeral instability

There has been substantial development of techniques for performing arthroscopic surgery of the shoulder over the past 20 years. A multitude of arthroscopic techniques have been developed in an attempt to manage the unstable glenohumeral joint while decreasing surgical morbidity. The results obtained with arthroscopic stabilization have been widely variable. This review will examine the current status of arthroscopic management of glenohumeral instability. The techniques and results of arthroscopic stabilization for primary anterior glenohumeral instability, recurrent anterior instability, and multidirectional instability will be discussed. A brief discussion on thermal capsulorrhaphy is included.     

Shoulder instability: return to play

Shoulder instability in the competitive athlete is a relatively common problem. The etiology of glenohumeral instability that can affect the athlete runs a wide spectrum, from an isolated traumatic dislocation to repeated microtrauma or congenital laxity. Although many athletes are able to adapt to a mild laxity that might only occasionally affect them, it can be much more difficult to adapt or return to play after a dislocation or repeated subluxation episodes. This article focuses on the return to play for competitive individuals after a glenohumeral dislocation or reconstructive surgery for shoulder instability.     

Magnetic resonance imaging of glenohumeral instability: new concepts

The shoulder is the most unstable joint in the human body and is therefore susceptible not only to acute dislocations but also to minimal states of subluxation related to overuse. The latter condition is known as microinstability and is translated clinically into internal impingement syndromes. Both in dislocations due to acute traumatism and in microinstability, a series of injuries to the glenoid lip, glenohumeral capsule, the articular cartilage, the head of the humerus, the tendons of the rotator cuff, the long tendon of the biceps, the glenohumeral ligaments, and coracohumeral ligament can occur. Glenoid lip lesions are the most common and may present as isolated lesions or in combination with lesions of any of the other structures. These lesions most often affect the anteroinferior margin of the glenoids (the classic Bankard lesion), with different characteristics and variations on its location, (Bankard variants). Another predominant location of glenoid lip lesions is the superior margin (SLAP lesions). Magnetic resonance imaging (MRI), especially after intra-articular injection of contrast material, has shown great diagnostic accuracy in this type of lesions, although the interpretation of these images requires knowledge not only of the different lesions and combinations of lesions, but also of the normal variants that can easily be confused with these lesions.     

Intra-articular volume assessment in glenohumeral instability

It is commonly claimed that instability of the shoulder is associated with an enlarged joint volume. The purpose of our study was to assess the intra-articular volume in acute and chronic glenohumeral dislocation. Sixty-seven patients were examined by intra-articular infusion of saline solution. Three groups could be formed. Group 1 (n = 51) consisted of patients with first time traumatic dislocation, group 2 (n = 8) of cases with recurrent post-traumatic dislocation. The patients of group 3 (n = 8) suffered from impingement syndrome and served as the control group. The joint volume was correlated to the body surface area (BSA). We found a strong correlation between height, sex and intra-articular joint volume. There was no statistically significant difference in joint volume correlated to BSA between the three groups. There is no statistically significant difference in joint volume correlated to BSA in patients with traumatic anterior instability, chronic instability and individuals without glenohumeral instability.     

MR imaging in sports-related glenohumeral instability

Sports-related shoulder pain and injuries represent a common problem. In this context, glenohumeral instability is currently believed to play a central role either as a recognized or as an unrecognized condition. Shoulder instabilities can roughly be divided into traumatic, atraumatic, and microtraumatic glenohumeral instabilities. In athletes, atraumatic and microtraumatic instabilities can lead to secondary impingement syndromes and chronic damage to intraarticular structures. Magnetic resonance (MR) arthrography is superior to conventional MR imaging in the diagnosis of labro-ligamentous injuries, intrinsic impingement, and SLAP (superior labral anteroposterior) lesions, and thus represents the most informative imaging modality in the overall assessment of glenohumeral instability. This article reviews the imaging criteria for the detection and classification of instability-related injuries in athletes with special emphasis on the influence of MR findings on therapeutic decisions.     

Magnetic resonance imaging in glenohumeral instability

The glenohumeral joint is the most commonly dislocated joint of the body and anterior instability is the most common type of shoulder instability.Magnetic resonance (MR) imaging,and more recently,MR arthrography,have become the essential investigation modalities of glenohumeral instability,especially for pre-procedure evaluation before arthroscopic surgery.Injuries associated with glenohumeral instability are variable,and can involve the bones,the labor-ligamentous components,or the rotator cuff.Anterior instability is associated with injuries of the anterior labrum and the anterior band of the inferior glenohumeral ligament,in the form of Bankart lesion and its variants;whereas posterior instability is associated with reverse Bankart and reverse Hill-Sachs lesion.Multidirectional instability often has no labral pathology on imaging but shows specific osseous changes such as increased chondrolabral retroversion.This article reviews the relevant anatomy in brief,the MR imaging technique and the arthrographic technique,and describes the MR findings in each type of instability as well as common imaging pitfalls.     

Shoulder instability: evaluation with MR imaging

Instability of the glenohumeral joint is a common cause of chronic shoulder pain and disability. One or more episodes of subluxation or dislocation may result in a tear, detachment, or attenuation of the glenoid labrum, stripping of the joint capsule from the scapula, or trauma to the tendons or muscles of the rotator cuff. A series of 27 shoulders examined with magnetic resonance (MR) imaging showed changes of glenohumeral instability, which were confirmed with open or arthroscopic surgery. MR imaging was capable of displaying common types of pathologic conditions resulting from instability, including labral trauma, capsular detachment, and retraction of the subscapularis muscle. MR imaging is a valuable diagnostic tool for the evaluation of glenohumeral instability.     

Magnetic resonance imaging of glenohumeral joint instability

Shoulder instability is common, especially anterior subluxation and dislocation. The sequelae are well seen on magnetic resonance imaging and include tears of the labrum, glenohumeral ligaments, capsule, tendons, and muscles. This article seeks to discuss and illustrate common pitfalls and lesions associated with instability. Anatomic and technical considerations, including the use of magnetic resonance arthrography, are also addressed.     

Treatment of glenohumeral instability in rugby players

Rugby is a high-impact collision sport, with impact forces. Shoulder injuries are common and result in the longest time off sport for any joint injury in rugby. The most common injuries are to the glenohumeral joint with varying degrees of instability. The degree of instability can guide management. The three main types of instability presentations are: (1) frank dislocation, (2) subluxations and (3) subclinical instability with pain and clicking. Understanding the exact mechanism of injury can guide diagnosis with classical patterns of structural injuries. The standard clinical examination in a large, muscular athlete may be normal, so specific tests and techniques are needed to unearth signs of pathology. Taking these factors into consideration, along with the imaging, allows a treatment strategy. However, patient and sport factors need to be also considered, particularly the time of the season and stage of sporting career. Surgery to repair the structural damage should include all lesions found. In chronic, recurrent dislocations with major structural lesions, reconstruction procedures such as the Latarjet procedure yields better outcomes. Rehabilitation should be safe, goal-driven and athlete-specific. Return to sport is dependent on a number of factors, driven by the healing process, sport requirements and extrinsic pressures. Level of evidence V.     

Evidence-based rehabilitation of athletes with glenohumeral instability

Purpose

To give an overview of current knowledge and guidelines with respect to evidence-based rehabilitation of athletes with glenohumeral instability.

Methods

This narrative review combines scientific evidence with clinical guidelines based on the current literature to highlight the different components of the rehabilitation of glenohumeral instability.

Results

Depending on the specific characteristics of the instability pattern, the severity, recurrence, and direction, the therapeutic approach may be adapted to the needs and demands of the athlete. In general, attention should go to (1) restoration of rotator cuff strength and inter-muscular balance, focusing on the eccentric capacity of the external rotators, (2) normalization of rotational range of motion with special attention to the internal rotation ROM, (3) optimization of the flexibility and muscle performance of the scapular muscles, and (4) gradually increasing the functional sport-specific load on the shoulder girdle. The functional kinetic chain should be implemented throughout all stages of the rehabilitation program. Return to play should be based on subjective assessment as well as objective measurements of ROM, strength, and function.

Conclusions

This paper summarizes evidence-based guidelines for treatment of glenohumeral instability. These guidelines may assist the clinician in the prevention and rehabilitation of the overhead athlete.

Level of evidence

Expert opinion, Level V.

     

CT arthrographic patterns in recurrent glenohumeral instability

CT double-contrast arthrograms were performed on 54 shoulders in 53 patients with recurrent dislocation or subluxation to detect responsible underlying bony or soft-tissue abnormalities. Lesions of the anterior labrum in 52 (96%) of 54 cases and of the capsuloligamentous complex in 42 (78%) of 54 cases were the two most common abnormalities. There was no difference in the degree or number of labral lesions between subluxations and dislocations. However, more severe capsular lesions, subscapularis tendon tears, and widened subscapularis bursae were consistently found among patients with dislocations. Subsequent clinical, arthroscopic, and surgical findings showed that the use of CT double-contrast arthrograms resulted in improved definition of the multiple lesions associated with glenohumeral dysfunction.     

Shoulder instability in thefemale athlete

Glenohumeral instability is relatively commonly observed in the female athlete. Studies have shown an increased incidence of both asymptomatic and pathological laxity among women. Female athletes participating in sports involving repetitive use of the upper extremity may be at particular risk for developing symptoms. Shoulder instability is classified according to etiology, onset, degree, and direction. Accurate diagnosis is important to determine proper management. Female athletes presenting with symptoms of shoulder instability should be initially treated with a comprehensive rehabilitation program emphasizing strengthening of the rotator cuff and dynamic scapular stabilizing muscles. After failure of nonoperative management, satisfactory results can be obtained using either open or arthroscopic surgical techniques.     

Imaging techniques for the evaluation of glenohumeral instability

The ability to image lesions associated with glenohumeral instability has evolved significantly over the past 2 decades. In the past, several imaging techniques ranging from conventional radiography to computerized axial arthrography and, most recently, to magnetic resonance imaging have been used to depict various labral abnormalities. In most instances, conventional radiography remains the initial imaging study for evaluating the patient with persistent shoulder pain and instability. Recently, however, magnetic resonance arthrography has been firmly established as the imaging modality of choice for demonstrating specific soft tissue abnormalities associated with glenohumeral instability. This article will review the role of various imaging modalities including conventional radiography, conventional arthrography, computerized axial arthrography, magnetic resonance imaging, and magnetic resonance arthrography. Emphasis will be placed on the role of magnetic resonance arthrography as it pertains to the lesions associated with glenohumeral instability. A thorough discussion of the appearance of normal anatomic structures, anatomic variations that mimic abnormality, and the various lesions associated with glenohumeral instability will be provided.     

Nontraumatic glenohumeral instability and coracoacromial impingement in swimmers

Competitive swimming is one of the most demanding and time-consuming sports. Swimmers at elite level practice 20–30 h per week. During 1 year's practice, the average top level swimmer performs more than 500,000 stroke revolutions per arm. These innumerable repetitions over many years of hard training together with an increasing muscular imbalance around the shoulder girdle seem to be the main etiological factors in the development of the overuse syndrome swimmer's shoulder. Shoulder pain in swimmers has in general been regarded as synonymous with coracoacromial impingement, i.e. anterior shoulder pain due to rotator cuff tendinitis, but new knowledge suggests that a concomitant glenohumeral instability plays an additional role. The diagnostic complexity of the problem is as challenging as the search for the gold standard of treatment. The condition should ideally be diagnosed as early as possible, and intensive functional rehabilitation of the shoulder girdle including the scapular muscles should be started in order to restore muscle balance. The surgical possibilities include subacromial decompression in cases of purely mechanical impingement. If a painful glenohumeral instability persists after intensive functional rehabilitation, anterior capsulolabral reconstruction can be performed. Still, however, short- and long-term results show that surgery is less successful in elite athletes involved in overhead sports. Prevention protocols include education of coaches in primary injury prophylaxis and the institution of resistance strength training in prepubescent swimmers. Emphasis should be made to improve muscular balance around the glenohumeral and scapulothoracic joints.     

Evidence-based conservative rehabilitation for posterior glenohumeral instability: A systematic review

Study designSystematic review.ObjectivesTo identify the best evidenced-based approach for the conservative rehabilitation of patients with posterior glenohumeral instability.BackgroundPosterior glenohumeral instability is more common than previously thought. Proper management is imperative to control symptoms and maximize function.MethodsWe conducted an electronic search, up to November 2014, for English-language studies involving rehabilitation of posterior shoulder instability. A manual search of reference lists of included articles and previously published reviews was also performed.ResultsFive studies met the review inclusion criteria. Most studies demonstrated that rotator cuff and posterior deltoid strengthening could reduce instability recurrence and pain, and increase function, mainly in those with atraumatic posterior instability without previous surgery. These studies were mainly case series or retrospective designs.ConclusionsRotator cuff and posterior deltoid strengthening may help with symptom-management and functioning in those with posterior glenohumeral instability. Further research is needed to detect statistically significant outcomes from conservative treatment.Level of evidenceTherapy, Level 3.