Glenohumeral Joint Instability: A Review of Anatomy, Clinical Presentation, and Imaging

The Role of Arthroscopy in Contemporary Glenoid Fossa Fracture Fixation

Glenoid fossa fractures are rare injuries accounting for 10 to 29% of all intra-articular scapula fractures. They are usually the result of high-energy trauma, and concomitant injuries are not uncommon. Patients with glenoid fractures are admitted with shoulder pain and restricted range of motion. Although shoulder plain radiographs could establish the diagnosis, a computed tomography scan is necessary to adequately define the fracture pattern and characteristics. The most commonly used classification system is that of Ideberg (modified by Goss), which includes five glenoid fossa fracture types according to the location, extension, and complexity of the lesion. Articular surface displacement and step-off are the most important factors that should be taken under consideration when deciding for conservative or surgical management. Operative treatment includes open reduction and internal fixation through a posterior or anterior approach depending on fracture morphology and displacement. However, open surgical techniques are related to extensive soft-tissue disruption, risk of neurovascular injury, and inadequate exposure of the entire glenoid cavity. Introduction of arthroscopy could facilitate better visualization of the glenoid articular surface and improved fracture reduction. However, it is a technically demanding procedure with many challenges and pitfalls. The aim of this review is to summarize the current evidence regarding the treatment of glenoid fossa fractures and present the beneficial effect of arthroscopy in improving the quality of fracture fixation and overall functional outcomes.

Single Working Portal Technique with 70-Degree Arthroscope for Arthroscopic Bankart Repair

The Bankart lesion is a common injury to the labrum in the shoulder joint, usually resulting from anterior shoulder dislocation. Arthroscopic Bankart repair is a surgical technique used to treat recurrent dislocations by reattaching the labrum to the glenoid rim using suture anchors. Typically, 3 portals are created: 1 for visualization and 2 for instrumentation. However, this Technical Note proposes a single working portal approach using a 70° arthroscope from the posterior portal. This technique enhances visualization and prevents portal jamming, particularly in cases with a small rotator interval.

Adhesive Capsulitis of the Shoulder: Current Concepts on the Diagnostic Work-Up and Evidence-Based Protocol for Radiological Evaluation

Adhesive capsulitis is an idiopathic and disabling disorder characterized by intense shoulder pain and progressive limitation of active and passive glenohumeral joint range of motion. Although adhesive capsulitis has been traditionally considered a diagnosis of exclusion that can be established based on a suggestive medical history and the detection of supporting findings at the physical exam, imaging studies are commonly requested to confirm the diagnostic suspicion and to exclude other causes of shoulder pain. Indeed, clinical findings may be rather unspecific, and may overlap with diseases like calcific tendinitis, rotator cuff pathology, acromioclavicular or glenohumeral arthropathy, autoimmune disorders, and subacromial/subdeltoid bursitis. Magnetic resonance imaging, magnetic resonance arthrography, and high-resolution ultrasound have shown high sensitivity and accuracy in diagnosing adhesive capsulitis through the demonstration of specific pathological findings, including thickening of the joint capsule and of the coracohumeral ligament, fibrosis of the subcoracoid fat triangle, and extravasation of gadolinium outside the joint recesses. This narrative review provides an updated analysis of the current concepts on the role of imaging modalities in patients with adhesive capsulitis, with the final aim of proposing an evidence-based imaging protocol for the radiological evaluation of this condition.

Posterior Dislocation of the Shoulder: The Light-Bulb Sign

Posterior dislocation is a rather rare injury, often misdiagnosed. The current report offers valuable insights regarding the anatomical background of this clinical entity and emphasizes the 'light-bulb sign,' which can be observed in anterior-posterior shoulder X-rays when there is a posterior dislocation. It is crucial for healthcare professionals, including emergency department physicians, radiologists, general practitioners, orthopedic surgeons, and other relevant medical experts, to be well-acquainted with this sign and maintain a heightened awareness when encountering such cases. A 57-year-old male presented to the Emergency Department due to right shoulder pain immediately after an epileptic seizure. His arm was locked in internal rotation, while the initial X-rays, although did not reveal evident malalignment, showed the light-bulb sign. Further imaging with a computer tomography (CT) scan exhibited a large (50%) reverse Hill-Sachs defect. The patient was treated surgically with hemiarthroplasty. The light-bulb sign should be a red flag for physicians who evaluate these patients or these X-rays. The patient's history, such as epileptic seizures and examination, especially the locked arm in internal rotation, are of paramount importance for not misdiagnosing these cases.

Current Concepts in the Measurement of Glenohumeral Bone Loss

PURPOSE

The extent of glenohumeral bone loss seen in anterior shoulder dislocations plays a major role in guiding surgical management of these patients. The need for accurate and reliable preoperative assessment of bone loss on imaging studies is therefore of paramount importance to orthopedic surgeons. This article will focus on the tools that are available to clinicians for quantifying glenoid bone loss with a focus on emerging trends and research in order to describe current practices.

RECENT FINDINGS

Recent evidence supports the use of 3D CT as the most optimal method for quantifying bone loss on the glenoid and humerus. New trends in the use of 3D and ZTE MRI represent exciting alternatives to CT imaging, although they are not widely used and require further investigation. Contemporary thinking surrounding the glenoid track concept and the symbiotic relationship between glenoid and humeral bone loss on shoulder stability has transformed our understanding of these lesions and has inspired a new focus of study for radiologists and orthopedist alike. Although a number of different advanced imaging modalities are utilized to detect and quantify glenohumeral bone loss in practice, the current literature supports 3D CT imaging to provide the most reliable and accurate assessments. The emergence of the glenoid track concept for glenoid and humeral head bone loss has inspired a new area of study for researchers that presents exciting opportunities for the development of a deeper understanding of glenohumeral instability in the future. Ultimately, however, the heterogeneity of literature, which speaks to the diverse practices that exist across the world, limits any firm conclusions from being drawn.

Arthroscopic Labral Repair and Pancapsular Shift With Knotless All-Suture Anchors in the Setting of Multidirectional Instability of the Shoulder

In the management of multidirectional type of shoulder instability (MDI), arthroscopic surgical stabilization is a preferred treatment option after failed conservative therapy regimens because of the ability to easily access all aspects of the capsule with one surgical procedure. As arthroscopic techniques have evolved, factors critical to postoperative success have been elucidated. Currently, optimal arthroscopic treatment of MDI involves circumferentially restoring labral integrity, a tailored, patient-specific surgical reduction of capsular volume, and adequately managing potential lesions of the biceps anchor. The purpose of this article and accompanying video is to present our technique for arthroscopic circumferential labral repair and pancapsular shift using knotless all-suture anchors in the setting of MDI with a concurrent type II SLAP lesion.

A stabilizing role of the glenoid labrum: the suction cup effect

BACKGROUND

The glenoid labrum acts as a bumper, deepening glenoid concavity and amplifying the concavity-compression mechanism, and serves as the scapular attachment for glenohumeral ligaments. The role of the posterosuperior labrum in anteroinferior glenohumeral stability, and the role of the anterior labrum in posterior stability has been debated. The purpose of this study was to quantify the contribution of anteroinferior and posterosuperior labral tears to loss of glenohumeral stability in multiple directions.

METHODS

Fourteen fresh-frozen cadaveric shoulders were tested on a custom stability ratio measurement apparatus. The peak force that was required to translate the humeral head in anterior, anteroinferior, posterior, and posteroinferior directions was measured under 5 conditions: intact labrum (n = 14), anteroinferior labral tear (n = 7), posterosuperior labral tear (n = 7), combined labral tear (n = 14), and no labrum (n = 14). The stability ratio was defined as the peak translational force divided by the compressive force. Within force-translation curves, we defined the suction cup effect as the force required to release the negative pressure created by an intact labrum.

RESULTS

The suction cup effect was usually present with the intact labrum and always disappeared after removal of the labrum for anterior (100% vs. 0%) and posterior (86% vs. 0%) translations (P < .001). After creation of an anteroinferior labral tear, the stability ratio for posterior direction decreased (P < .001) and the suction cup effect disappeared (P < .001). After creation of a posterosuperior labral tear, stability ratios in the anterior and anteroinferior directions decreased (P ≤ .006) and the suction cup effect disappeared (P ≤ .015). The stability ratio for anterior and anteroinferior testing was more diminished by posterosuperior labral tears than anteroinferior labral tears, and the stability ratio for posterior testing was more diminished by anteroinferior labral tears than posterosuperior labral tears.

CONCLUSION

Anteroinferior labral tears decreased posterior stability and posterosuperior labral tears decreased anterior and anteroinferior stability, largely because of loss of the suction cup effect.

Increased superior translation following multiple simulated anterior dislocations of the shoulder

PURPOSE

Recurrent shoulder dislocations can result in kinematic changes of the glenohumeral joint. The number of prior shoulder dislocations may contribute to increased severity of capsulolabral lesions. The kinematics of the glenohumeral joint following multiple dislocations remain poorly understood. The purpose of this study was to assess the kinematics of the glenohumeral joint during anterior dislocations of the shoulder, and more specifically, altered translational motion following multiple dislocations. The kinematics of the glenohumeral joint were hypothesized to change and correlate with the number of dislocations.

METHODS

Eight fresh-frozen cadaveric shoulders were dissected free of all soft tissues except the glenohumeral capsule. Each joint was mounted in a robotic testing system. At 60 degrees of glenohumeral abduction, an internal and external rotational torque (1.1 Nm) were applied to the humerus, and the resulting joint kinematics were recorded. Anterior forces were applied to the humerus to anteriorly dislocate the shoulder and the resulting kinematics were recorded during each dislocation. Following each dislocation, the same rotational torque was applied to the humerus, and the resulting joint kinematics were also recorded. A repeated-measures analysis of variance (ANOVA) was used to compare the kinematics following each dislocation.

RESULTS

During the 7th, 8th, 9th, and 10th dislocations, the humerus significantly translated superiorly compared with the shoulder during the 1st dislocation (p < 0.05). Following the 3rd, 4th, 5th, and 10th dislocations, the humeral head significantly translated superiorly compared with the shoulder following the 1st dislocation in the position of 60 degrees of abduction in response to external rotation torque (p < 0.05).

CONCLUSION

Multiple anterior shoulder dislocations lead to abnormal translational kinematics and result in increased superior translation of the humerus. This may contribute to pathologic superior extension of capsulolabral injuries. Superior translation of the humerus with overhead motion in the setting of recurrent instability may also place the shoulder at risk for extension of the capsulolabral injuries.

Knotless Arthroscopic Glenoid Labral Stabilization for a 270° Tear With Concurrent Remplissage in the Lateral Decubitus Position

Labral tears resulting in 270° near-circumferential pathology predispose patients to recurrent instability and are technically challenging to repair. Furthermore, when such lesions are associated with Hill-Sachs lesions, recurrent instability risk is significantly increased and can result in substantially lower clinical outcomes. When determining a surgical treatment algorithm for shoulder stabilization, it is important to consider both humeral- and glenoid-sided pathology because subtle defects can have significant influence on recurrence and patient reported outcomes. In this Technical Note and accompanying video, we discuss our surgical technique for knotless arthroscopic stabilization for a 270° labral tear with concurrent remplissage in the setting of recurrent shoulder instability.

[Effectiveness of a single threaded anchor fixation under shoulder arthroscopy in treatment of fresh bony Bankart injury]

OBJECTIVE

To investigate the effectiveness of a single threaded anchor fixation under shoulder arthroscopy in the treatment of fresh bony Bankart injury.

METHODS

Between January 2017 and May 2021, 12 patients with fresh bony Bankart injury caused by trauma were treated with a single threaded anchor fixation under shoulder arthroscopy. There were 10 males and 2 females with an average age of 38.8 years (range, 21-64 years). The time between injury and operation ranged from 7 to 30 days (mean, 15.8 days). Preoperative American Shoulder and Elbow Surgeons (ASES) score was 44.9±17.4, the University of California at Los Angeles (UCLA) score was 13.1±5.5; the forward supination, lateral external rotation, and lateral internal rotation of shoulder were (130.8±11.8)°, (25.0±7.9)°, and 9.2±1.6, respectively. CT scan and three-dimensional (3D) reconstruction showed that the fracture fragment area was less than 1/4 of the glenoid area in 10 cases, and 1/4-1/2 in 2 cases. The operation time was recorded. During follow-up, ASES score, UCLA score, Rowes score, and shoulder range of motion were used to evaluate the effectiveness, and shoulder CT scan and 3D reconstruction were used to evaluate the fracture position and healing.

RESULTS

The operation time ranged from 50 to 150 minutes (mean, 85.5 minutes). All patients were followed up 3-18 months (mean, 9.1 months). There was no serious adverse effect such as infection, re-dislocation, or thrombosis. Three patients had shoulder adhesions after operation. At last follow-up, the forward supination of shoulder [(162.1±30.3)°], lateral external rotation [(37.5±11.2)°], and lateral internal rotation (9.2±1.6) significantly improved when compared with those before operation ( t=3.331, P=0.003; t=3.153, P=0.005; t=2.716, P=0.013). The ASES score was 89.7±11.8 and the UCLA score was 32.8±2.4, which significantly increased when compared with those before operation ( t=7.368, P<0.001; t=11.370, P<0.001). The Rowes score ranged from 75 to 100 (mean, 92.9). Among them, 9 cases were excellent and 3 cases were good, with an excellent and good rate of 100%. CT re-examination showed that the fracture line disappeared in 11 cases, and the fracture alignment was good; the alignment of the fracture fragment was poor in 1 case whose fracture fragment area was between 1/4 and 1/2 of the glenoid area.

CONCLUSION

For the fracture fragment area not exceeding 1/4 of the glenoid, the labrum-capsule complex at the lower end of the bone fragment intact, and the non-comminuted fresh bony Bankart injury, a single threaded anchor fixation under shoulder arthroscopy can achieve better effectiveness, has the advantages of less trauma and faster postoperative recovery.