Shoulder Arthrogram

Anatomy and Physiology

Overview of Shoulder Joint Anatomy

The glenohumeral joint, a synovial ball-and-socket articulation, connects the upper limb to the axial skeleton. This joint is formed by the articulation of the large, convex humeral head with the smaller, shallow glenoid fossa of the scapula. The extensive mobility of the glenohumeral joint—encompassing circumduction, flexion, extension, abduction, adduction, and rotation— is achieved because of a significant mismatch in the size of its articular surfaces. However, this remarkable range of motion results at the expense of the joint's inherent stability.

To mitigate this instability, several anatomical structures enhance the joint's congruity and provide reinforcement. The articular surfaces of both the humeral head and the glenoid fossa are covered by hyaline cartilage. The cartilage on the glenoid is characteristically thinner at its center and thicker at the periphery, which deepens the socket. Conversely, the cartilage covering the humeral head is thickest centrally and thins toward its periphery. A fibrocartilaginous rim, the glenoid labrum, attaches to the periphery of the glenoid fossa, effectively increasing its surface area and deepening the socket by approximately 50%, which contributes significantly to joint stability.

The entire joint is enclosed by a fibrous joint capsule that extends from the anatomical neck of the humerus to the border of the glenoid fossa. The capsule is notably lax, a feature that facilitates the joint's wide range of motion. Lining the inner surface of this capsule is the synovial membrane, which is responsible for producing synovial fluid. This fluid lubricates the joint, minimizing friction between the articulating surfaces during movement.

To further reduce friction, particularly between tendons and bony structures, the shoulder contains several synovial bursae. These fluid-filled sacs cushion the joint's moving parts. The most clinically significant of these are the subacromial-subdeltoid bursa and the subscapularis bursa. The subacromial-subdeltoid bursa is located superior to the supraspinatus tendon and joint capsule, and deep to the deltoid muscle and the coracoacromial arch. The bursa promotes the free movement of the rotator cuff tendons beneath these overlying structures. The subscapularis bursa is situated between the subscapularis tendon and the neck of the scapula, reducing wear on the tendon as it moves across the bone.

Vascular supply to the glenohumeral joint is robust, primarily originating from the anterior and posterior circumflex humeral arteries, which are branches of the axillary artery. Additional supply comes from branches of the suprascapular artery. Innervation is provided by the suprascapular, axillary, and lateral pectoral nerves.

Static Stabilizers: Osseous and Ligamentous Anatomy

Bony architecture and ligamentous complexes provide the shoulder with static stability.

Osseous anatomy

The osseous anatomy of the shoulder joint functions as the underlying structural framework for the other ligamentous and capsular anatomical components of the shoulder.

Clavicle

This S-shaped bone articulates with the sternum medially (sternoclavicular joint) and the acromion laterally (acromioclavicular joint). Its shape can vary, and the lateral half features an irregular ridge for the attachment of the deltoid and trapezoid muscles.

Scapula

This triangular bone consists of a body, neck, and spine. The scapula features the following 3 key processes that articulate with the clavicle and humerus:

• Glenoid fossa
• Coracoid process
• Acromion

The glenoid fossa is the pear-shaped articular surface for the humeral head, measuring approximately 6 to 8 square cm. The glenoid fossa comprises the supraglenoid tubercle, the origin of the long head of the biceps tendon, and the infraglenoid tubercle, the origin of the long head of the triceps. The glenoid is typically oriented in approximately 2 to 5 degrees of anteversion. The pear shape is crucial for stability; anterior bone loss, often resulting from dislocations, can lead to an "inverted pear" appearance, compromising stability. A central bare area on the glenoid cartilage, known as the tubercle of Assaki, corresponds to a thickened area of subchondral bone.

Coracoid process

This process arises from the anterolateral aspect of the scapula and serves as the origin for the short head of the biceps and the pectoralis minor muscle. The orientation of the coracoid process can influence the subcoracoid space, and variations in its morphology may contribute to subcoracoid impingement.

Acromion and modern morphometrics

Historically, acromial morphology was described using the Bigliani classification, which categorized the acromion as type I (flat), type II (curved), or type III (hooked) based on its sagittal profile.[24] A type III acromion was postulated to cause mechanical impingement and subsequent rotator cuff tears. However, the clinical utility of this classification is now considered limited due to poor-to-fair inter-observer reliability across multiple imaging modalities and among observers of varying expertise.[24] Furthermore, a direct causal link between a specific Bigliani type and rotator cuff pathology has not been consistently supported by evidence, with several studies finding no significant association.[24] Contemporary assessment has shifted toward more objective, quantitative, and biomechanically relevant radiographic parameters [25], including:

• Critical shoulder angle (CSA): This angle reflects the balance between compressive and shear forces at the joint. A large CSA (>35-38 degrees) is strongly associated with increased shear forces, leading to tensile overload of the supraspinatus and a higher risk of degenerative rotator cuff tears. Conversely, a small CSA (<30-33 degrees) is associated with increased compressive forces and an increased risk of glenohumeral osteoarthritis.[25]
• Lateral acromial angle (LAA): This measures the coronal slope of the acromion. A lower (more inferiorly sloped) LAA reduces the volume of the subacromial space and is associated with a higher prevalence of impingement symptoms and cuff tears.[26]
• Acromion index: This ratio quantifies the lateral extension of the acromion. A greater lateral extension is associated with an increased risk of rotator cuff pathology, likely due to alterations in deltoid muscle forces and an increased load on the supraspinatus.[26]

This paradigm shift reflects a more nuanced understanding of rotator cuff disease, moving from a simple model of extrinsic mechanical abrasion to a biomechanical model that incorporates intrinsic tendinosis from chronic tensile overload.[25]

Humerus and the coracohumeral interval

The articular surface of the humeral head is normally retroverted by approximately 30 degrees. Its hyaline cartilage is thickest in the center and thins peripherally, with an average thickness of 1.24 mm. A bare area exists on the posterosuperior aspect of the humeral head, between the synovial membrane insertion and the articular cartilage. Another bare area is found between the supraspinatus insertion on the greater tuberosity and the adjacent cartilage; this area can enlarge with undersurface cuff tears.

Coracohumeral interval 

Coracohumeral interval (CHI), or subcoracoid space, is the distance between the coracoid process and the lesser tuberosity. This is a dynamic space that narrows with internal rotation and forward flexion. While early studies suggested a normal range of 10 to 11.5 mm, its diagnostic value is now considered controversial.[27] The CHI is highly variable, influenced by patient sex and arm position, and its utility as a standalone marker for subcoracoid impingement or subscapularis tears is poor.[28] While some studies have proposed pathologic thresholds of less than 9.5 mm or less than 5.9 mm, others have found no significant correlation between the CHI measurement and subscapularis pathology, particularly in younger populations.[29] A diagnosis of subcoracoid impingement should therefore be based on a combination of clinical symptoms and supportive imaging findings, eg, a narrowed interval accompanied by direct evidence of subscapularis tendinopathy or bursal inflammation.[28]

Ligamentous and capsular anatomy

The ligamentous and capsular structures provide strong, stabilizing connections between the bones of the shoulder joint. 

Acromioclavicular joint

The acromioclavicular (AC) joint is stabilized by the AC ligaments, which reinforce the capsule, and dynamically by the deltoid and trapezius muscles. The primary stabilizer of this synovial joint is the coracoclavicular ligament.

Coracoclavicular and coracoacromial ligaments

The coracoclavicular ligament consists of 2 parts, the medial conoid and the lateral trapezoid, which prevent displacement of the clavicle. The coracoacromial ligament forms the coracoacromial arch, which acts as the roof of the subacromial space.

Glenoid labrum and associated variants

As a fibrocartilaginous structure, the glenoid labrum not only makes the glenoid socket deeper but also acts as the attachment site for the glenohumeral ligaments and the long head of the biceps tendon. It typically has a triangular shape, though other morphologies exist. While direct MRA has historically been considered the gold standard for labral evaluation, the diagnostic capabilities of noncontrast 3-Tesla (3T) MRI have advanced significantly. A 2018 meta-analysis found that while 3T MRA offers higher sensitivity for detecting anterior and posterior labral tears, this study has significantly lower specificity for superior labrum anterior-posterior (SLAP) lesions compared to 3T MRI.[30] The choice of imaging is therefore patient- and question-specific. Several anatomical variants are crucial to recognize to avoid misdiagnosis, including:

• Sublabral recess: This is a normal, smooth-margined synovial-lined gap between the superior labrum and the glenoid cartilage, typically at the 11-to-1 o'clock position. The sublabral recess can mimic a SLAP tear but should not extend laterally into the labral substance or be associated with paralabral cysts.[31]
• Buford complex: This variant, present in 1.5% to 6.5% of individuals, consists of a congenitally absent anterosuperior labrum and a thickened, cord-like middle glenohumeral ligament (MGHL) that originates directly from the biceps anchor. Historically considered benign, the Buford complex is now recognized as a significant risk factor for developing SLAP tears due to altered biomechanics that concentrate force on the biceps anchor.[32] Misidentifying this variant as a tear and attempting surgical repair can lead to iatrogenic loss of external rotation and pain.[32]

Biceps tendon and bicipital-labral complex

The long head of the biceps tendon (LHBT) originates from the supraglenoid tubercle and the superior labrum. The attachment site is known as the biceps anchor or bicipital-labral complex. Several other types of attachments are present, some of which create a deep synovial recess (sublabral recess) that is a normal variant.

The aponeurotic expansion of the supraspinatus tendon (AEST) is a common anatomical variant originating from the anterior supraspinatus tendon, which then courses superficially along the bicipital groove to insert on the pectoralis major tendon. Because this structure runs parallel to the long head of the biceps tendon, its primary clinical significance is that the AEST can be mistaken for a longitudinal tear of the biceps tendon on shoulder imaging studies.[33]

Glenohumeral ligaments and joint capsule

The joint capsule is reinforced by thickenings that form the glenohumeral ligaments. The superior glenohumeral ligament (SGHL) originates near the biceps anchor and inserts into a small depression superior to the lesser tuberosity. The middle glenohumeral ligament (MGHL) is highly variable and may be absent in up to 30% of shoulders. 

The inferior glenohumeral ligament (IGHL) provides vital stability against anterior and inferior translation through its structure, which includes an anterior band, a posterior band, and an axillary pouch. Normal communication channels exist between the glenohumeral joint and the subscapularis bursa, including the foramen of Weitbrecht (between the SGHL and MGHL) and the foramen of Rouviere (between the MGHL and IGHL).

Functional Complexes: The Rotator Interval and Biceps Pulley

The anterosuperior aspect of the shoulder contains a critical functional region known as the rotator interval. This triangular space is bordered by the supraspinatus tendon superiorly, the subscapularis tendon inferiorly, and the coracoid process medially.[34] This interval is not an empty space but a multi-layered area containing the coracohumeral ligament (CHL), the superior glenohumeral ligament (SGHL), the rotator interval capsule, and the intra-articular portion of the LHBT.[34]

Within this interval, a vital soft tissue sling known as the biceps reflection pulley stabilizes the LHBT as it exits the joint. This pulley is a composite structure formed by the interwoven fibers of the CHL, SGHL, and the adjacent supraspinatus and subscapularis tendons.[35] This complex wraps around the LHBT, acting as the primary restraint against medial subluxation or dislocation.[35]

The rotator interval is a key functional crossroads. Pathologic laxity of its structures can contribute to glenohumeral instability, while pathologic thickening and contracture, particularly of the CHL and interval capsule, are the hallmark findings in adhesive capsulitis (ie, frozen shoulder).[34]

Active Stabilizers: The Rotator Cuff Muscles

The dynamic stability of the glenohumeral joint is provided by the following 4 muscles of the rotator cuff, which originate from the scapula and form a musculotendinous cuff that envelops the humeral head:

• Supraspinatus: Originating from the supraspinous fossa, its tendon inserts on the highest impression of the greater tuberosity. The supraspinatus muscle is responsible for initiating abduction.
• Infraspinatus and teres minor: These muscles originate from the infraspinous fossa and insert on the greater tuberosity posterior to the supraspinatus. The infraspinatus and teres minor are the primary external rotators of the shoulder.
• Subscapularis: Arising from the anterior surface of the scapula, its multi-tendinous structure inserts primarily on the lesser tuberosity. The subscapularis muscle is the primary internal rotator of the shoulder. The superior fibers of the subscapularis tendon cross over the bicipital groove to blend with the supraspinatus tendon, contributing to the biceps pulley system.

Indications

MRI is a cornerstone in the evaluation of intra-articular shoulder pathology. The choice between noncontrast MRI and MRA is nuanced and depends on the specific clinical question, patient factors, and the availability of joint injection support. While MRA, which involves the intra-articular injection of a dilute gadolinium-based contrast agent, provides maximal joint distention and outlines intra-articular structures, its use has become more selective with the advent of high-field (3T) MRI.[36]

High-field noncontrast MRI can provide excellent diagnostic accuracy for many conditions, reserving the more invasive MRA for specific indications where the highest sensitivity is required or when noncontrast imaging is indeterminate.[36] MRA is particularly valuable for evaluating the biceps-labral complex, glenohumeral ligaments, and joint capsule, especially in the context of suspected subtle instability or for evaluating specific, less common pathologies, eg, posterior synovial folds.[37]

Glenohumeral Instability

Glenohumeral instability is a primary indication for advanced imaging to identify labral, capsular, and osseous lesions, which guide treatment decisions and may include surgical versus nonsurgical pathways.[38] In patients with suspected labral tears, particularly young, active individuals with a history of dislocation or clinical findings of microtrauma, direct MRA is often considered the imaging reference standard. Its superiority is attributed to the joint distention and contrast outlining of subtle tears, including SLAP lesions and variants of Bankart lesions.[38]

However, the performance gap between MRA and noncontrast MRI has narrowed significantly with the advancement of modern technology. Multiple studies and meta-analyses have demonstrated that noncontrast 3T MRI has high sensitivity (83% to 90%) and specificity (>99%) for detecting labral tears, approaching the performance of MRA.[39] Therefore, in alignment with the ACR Appropriateness Criteria, noncontrast 3T MRI may be a sufficient and appropriate initial advanced study. MRA is often reserved for cases where clinical suspicion for a reparable lesion remains high despite a negative or equivocal non-contrast MRI, for elite athletes, or for detailed preoperative planning.[22]

Rotator Cuff Integrity

In evaluating rotator cuff integrity, the role of MRA is highly specific. For suspected primary (nonoperative) tears, noncontrast MRI or high-resolution ultrasound are the preferred advanced imaging modalities. Both demonstrate excellent and comparable accuracy for full-thickness defects, which is the key determinant for surgical intervention.[15] The primary and most robust indication for MRA in assessing the rotator cuff is in the postoperative setting. Following rotator cuff repair, the injected contrast helps to definitively distinguish a full-thickness retear (indicated by contrast extravasation through the defect) from postoperative granulation tissue or scarring. This distinction can be extremely challenging and often indeterminate on noncontrast studies.[40]

As with any advanced imaging, radiographs of the glenohumeral joint should be performed first to assess for fractures, dislocation, glenohumeral arthritis, and other significant osseous lesions.[22] In cases of suspected adhesive capsulitis, a condition diagnosed primarily on clinical grounds, MRI can serve as a valuable adjunct. The role of imaging is to exclude other causes of a stiff, painful shoulder and to demonstrate supportive findings, eg, thickening and signal abnormalities of the coracohumeral ligament and the joint capsule at the rotator interval and axillary recess. These findings are typically well visualized on noncontrast MRI, making MRA unnecessary for this indication.[17] Finally, MRA remains a critical problem-solving tool for patients with persistent or new symptoms following orthopedic shoulder surgery, where it can be used to assess the integrity of labral and rotator cuff repairs, evaluate for capsular pathology, and identify intra-articular osteochondral bodies.[36]

Imaging Modality Selection

The choice between CTA and MRA is driven by the specific clinical question and suspected pathology, as these modalities have distinct and complementary strengths.

CT arthrography

CTA is the superior modality for evaluating osseous and chondral structures and should be considered a primary imaging tool, not merely a salvage procedure. Its high spatial resolution makes CTA the gold standard imaging modality for the following joint pathologies:

• Glenoid bone loss: CTA is recommended to accurately measure the size of bony Bankart lesions and the percentage of glenoid bone loss, which is critical for surgical planning in patients with instability.[41]
• Osseous lesions: Because CTA can provide detailed morphology of Hill-Sachs lesions and complex glenoid rim fractures, this modality is preferred for characterizing osseous lesions.[42] 
• Articular cartilage: CTA is the reference standard for detecting and grading cartilage surface defects.[41]

CTA is also faster to acquire, more accessible, and less susceptible to motion and metallic hardware artifacts than MRA.[41]

MR arthrography 

MRA is the preferred modality for the detailed evaluation of soft-tissue structures, including the labroligamentous complex and rotator cuff. MRA is preferred over CTA for the following:

• Evaluating the labrum and ligaments: MRA has high sensitivity for labral tears and is superior to CTA for assessing the integrity of the glenohumeral ligaments, particularly the inferior glenohumeral ligament (IGHL).[42]
• Diagnosing rotator cuff tears: MRA is more accurate for detecting partial-thickness rotator cuff tears.[41]
• Detecting associated pathology: MRA is uniquely capable of identifying bone marrow edema (contusion) and injuries to extra-articular soft tissues.[42]

For complex cases of shoulder instability where both bone and soft-tissue injuries are suspected, a combined imaging approach, eg, MRA plus a nonarthrographic CT, may provide the most comprehensive preoperative assessment.[42]

Contraindications

Absolute Contraindications

The primary absolute contraindication for glenohumeral arthrography is an active infection. This includes septic arthritis of the shoulder joint itself, as well as cellulitis or an abscess in the soft tissues overlying the planned needle trajectory. Performing an arthrogram in the presence of such infection carries a significant risk of iatrogenically introducing or spreading pathogens into the sterile joint space, which can lead to septic arthritis.[43]

Relative Contraindications and Special Considerations

Contrast allergy 

A prior moderate or severe allergic-like reaction to the same class of contrast medium (iodinated or gadolinium-based) is a relative contraindication. In patients with a known allergy to GBCAs, a direct MRA should be avoided. Alternatives include a CT arthrogram (if no iodine allergy exists) or an indirect MRA. For patients with a known allergy to iodinated contrast, a CT arthrogram should be avoided.

If a contrast-enhanced study is deemed medically necessary despite a prior reaction, consultation with the radiology department regarding premedication protocols is essential. The ACR provides specific corticosteroid and antihistamine regimens that can significantly reduce the risk of a recurrent reaction.[ACR Contrast Manual] Clinicians should also be aware that acute adverse reactions following the arthrogram procedure can be related to the local anesthetic or the antiseptic skin preparation solution, rather than the contrast agent itself.[44]

Anticoagulant or antiplatelet therapy

Periprocedural management of antithrombotic therapy should be based on a risk-stratified approach that balances the procedure's bleeding risk against the patient's thromboembolic risk. Shoulder arthrography is categorized as a low-risk procedure for bleeding. Based on current consensus guidelines from the Society of Interventional Radiology (SIR) and other bodies, the following recommendations apply:

• Warfarin (coumadin): Patients may continue warfarin. The procedure can be performed safely if the INR on the day of the procedure is 3.0 or less. An INR check is recommended before the procedure.
• Direct oral anticoagulants (DOACs): For low-risk procedures, DOACs (eg, apixaban, rivaroxaban) do not need to be withheld.
• Antiplatelet agents: Aspirin and P2Y12 inhibitors (eg, clopidogrel) do not need to be withheld for low-risk procedures.

Unnecessarily discontinuing these medications for a low-risk procedure may place the patient at a significant risk for a thromboembolic event. Additionally, using a smaller gauge needle (eg, 22-gauge or 25-gauge) is a prudent measure in any patient with a potential bleeding diathesis.[45]

Complex regional pain syndrome 

A history of complex regional pain syndrome (CRPS), formerly known as reflex sympathetic dystrophy, is a relative contraindication. CRPS is a complex neuro-inflammatory pain disorder, and any noxious stimulus, including a needle puncture, can potentially trigger a painful flare-up.[46] However, since various injection-based therapies are used in the treatment of CRPS, the condition is not an absolute contraindication for a diagnostically necessary procedure.[47] A thorough discussion of the risks (symptom exacerbation) and benefits (obtaining critical diagnostic information) with the patient and referring clinician is mandatory before proceeding.

Special Patient Populations

Pregnant patients

The use of GBCAs during pregnancy requires a careful risk-benefit analysis. GBCAs cross the placenta, and their effects on the human fetus are not fully understood. Therefore, according to ACR guidelines, an MRA should only be performed in a pregnant patient if the diagnostic information is essential for the patient's or fetus's health and cannot be obtained by other means (eg, noncontrast MRI or ultrasound).[ACR Contrast Manual]

Lactating patients

According to the 2024 ACR Manual on Contrast Media, discontinuing breastfeeding after receiving a GBCA is unnecessary.[ACR Contrast Manual] The recommendation to "pump and dump" breast milk is obsolete. This evidence-based guideline is based on pharmacokinetic data showing that the dose of contrast absorbed by a nursing infant is clinically insignificant (<0.0004% of the maternal dose) and unlikely to be harmful.[48] This updated recommendation avoids unnecessary disruption and stress for both the mother and the infant.

Equipment

A direct arthrogram of the glenohumeral joint involves the injection of a contrast solution to distend the joint capsule for subsequent cross-sectional imaging.[49] The procedure requires strict aseptic technique, utilizing skin cleansers, sterile drapes, and swabs to maintain a sterile field.[50]

Guidance and Needle Placement

Image guidance is standard practice to ensure accurate intra-articular needle placement. While fluoroscopy and CT are effective, ultrasound guidance is now frequently favored as it avoids ionizing radiation and allows for real-time visualization of soft tissues, which can prevent inadvertent needle passage through tendons.[49] A 25-gauge needle is typically used to administer a local anesthetic to the skin and subcutaneous tissues.[50] For the arthrogram injection itself, a 20- to 22-gauge spinal needle is commonly employed.[51] The anterior approach targeting the rotator cuff interval is a widely adopted technique that minimizes the risk of damaging anterior stabilizing structures.[51]

Injectate Formulation for Diagnostic Arthrography

The composition of the injectate is tailored to the subsequent imaging modality (CT or MRI) and specific clinical and safety considerations.

Local anesthetic

A local anesthetic is used to numb the area around the needle tract. For diagnostic blocks intended to confirm an intra-articular source of pain, a long-acting anesthetic is used.[2] However, extensive evidence has shown that local anesthetics can be toxic to cartilage cells (chondrotoxicity) in a dose- and time-dependent manner.[52] Bupivacaine and lidocaine have demonstrated higher chondrotoxicity in laboratory studies compared to ropivacaine.[53] Therefore, when an anesthetic is included in the intra-articular mixture, low-concentration ropivacaine (eg, 0.2% or 0.5%) is often preferred to minimize the risk of cartilage damage.[52]

CT and MR arthrography

The injectate for CTA studies consists of a nonionic iodinated contrast agent, typically diluted with sterile saline or a local anesthetic.[2]

The injectate for MRA is based on a GBCA. In light of evidence of gadolinium retention in the body, the use of more stable macrocyclic GBCAs is strongly recommended over less stable linear agents.[54] The GBCA is highly diluted, and the optimal concentration depends on several factors, including:

• Without iodinated contrast (eg, ultrasound guidance): For imaging on a 1.5T or 3.0T MRI scanner, a gadolinium concentration of approximately 1.25 to 2.5 mmol/L is often used.[55] A common formulation involves diluting 0.1 mL of a macrocyclic GBCA in a total volume of 20 mL of saline and/or a low-toxicity local anesthetic (eg, ropivacaine).
• With iodinated contrast (eg, fluoroscopic/CT guidance): The presence of iodinated contrast alters the magnetic properties of the solution. To achieve optimal image quality and avoid signal loss, a lower gadolinium concentration, in the range of 0.625 to 1.25 mmol/L, is required.[55]

Therapeutic Injection

For therapeutic purposes, a corticosteroid may be added to the injectate without adversely impacting the MR signal.[55] Corticosteroids are contraindicated if a joint infection is suspected.[56] Following the injection, which distends the joint capsule, the patient proceeds to CT or MRI for detailed cross-sectional imaging. The imaging should be performed relatively promptly, typically within 90 minutes after injection, to ensure optimal joint distension and contrast visualization before significant absorption occurs.[57]

Personnel

The performance of shoulder arthrography, whether followed by MRI or CT, is a collaborative procedure conducted by a physician-led team. The supervising radiologist retains ultimate responsibility for the patient's safety and the diagnostic quality of the examination. The team includes the radiologist, potentially an advanced practitioner, and a radiologic technologist, each with clearly defined roles and responsibilities governed by professional standards, state laws, and institutional policies.

The referring clinician initiates the request for the examination and is responsible for providing the relevant clinical history necessary to establish medical necessity. The referring clinician should have a fundamental understanding of the indications and contraindications for arthrography to facilitate an appropriate patient referral and initial discussion.[58]

The radiologist, a physician with specialized training in medical imaging, is responsible for all medical aspects of the study, including confirming the appropriateness of the examination, developing the imaging protocol, and ensuring adherence to safety standards. The radiologist must apply current knowledge of contrast agents, including the ACR safety classifications for GBCAs and the risks of NSF and gadolinium deposition.[59] The radiologist provides the necessary level of supervision for all team members and performs the final image interpretation to generate the diagnostic report.

The intra-articular injection may be performed by the radiologist or delegated to another qualified clinician under appropriate supervision. The following roles of these clinicians are distinct and not interchangeable:

• The registered radiologic assistant (RRA) is an advanced practice radiographer who has completed a nationally accredited, radiology-focused educational program and holds ARRT certification as an RRA.[60] The RRA scope of practice, as defined by the ASRT and recognized by many state laws, explicitly includes performing patient assessments and management, as well as carrying out selected radiologic procedures, including joint injections for arthrography, under the supervision of a radiologist. The RRA communicates initial observations only to the supervising radiologist and does not provide an interpretation of the findings.
• A physician assistant or nurse practitioner may also be part of the radiology care team. These clinicians are licensed general medical practitioners who work under a collaborative practice agreement with a physician. While they are qualified to perform patient assessments, obtain consent, and manage patient care, their authority to administer the arthrogram injection itself is not nationally standardized and varies significantly, being strictly governed by individual state practice acts and institutional credentialing policies.[61]

The radiologic technologist is a vital team member responsible for patient safety and the technical acquisition of images. The technologist prepares the patient and the sterile equipment for the procedure, positions the patient for the injection and the subsequent MRI or CT scan, and operates the imaging equipment to obtain high-quality diagnostic data as specified in the protocol determined by the radiologist.

Preparation

As with any invasive procedure, a comprehensive discussion of the risks, benefits, and alternatives is conducted with the patient, and written informed consent is obtained. The specific joint and laterality must be confirmed. A thorough review of the patient's history, including any allergies to medications, contrast media, or skin preparation solutions, is mandatory.

If the patient is scheduled to undergo an MRI following the arthrogram, a rigorous safety screening process must be completed in accordance with the most current institutional policies and the ACR Manual on MR Safety.[62] To ensure patient safety, this involves screening for all contraindications, especially implanted electronic devices, eg, cardiac pacemakers, neurostimulators, and implantable cardioverter-defibrillators (ICDs). Many such devices are now "MR Conditional," meaning they are safe for MRI under specific manufacturer-defined conditions. The screening process must therefore identify the exact make and model of any implanted device to verify its MR compatibility and ensure that all conditions for a safe scan can be met.[62]

For elective procedures, periprocedural management of anticoagulation is a critical consideration, guided by the 2019 Society of Interventional Radiology Consensus Guidelines.[63] Shoulder arthrography is classified as a low-risk procedure for bleeding. Therefore, for patients on warfarin, the procedure can typically proceed without interruption if the INR is less than 3.0.[63]

For patients on DOACs, the decision to hold the medication depends on the specific agent, the patient's renal function, and institutional protocol. However, interruption is often not required for low-risk procedures.[63] Consultation with the referring physician or an anticoagulation management service is recommended. Although the risk of a significant postprocedural hematoma is low, this possibility should be included in the informed consent discussion.

The intra-articular injection is performed under image guidance, typically using fluoroscopy, ultrasound, or CT. The composition of the injectate depends on the subsequent imaging modality. For CTA, the injectate consists of a diluted solution of nonionic iodinated contrast. To minimize beam-hardening artifacts that can obscure intra-articular anatomy, standard contrast (eg, 300 mgI/mL) is typically diluted with sterile saline or a local anesthetic to a final iodine concentration of approximately 150 mgI/mL. 

For MRA, the injectate is a dilute solution of a GBCA. To maximize patient safety, a Group II (macrocyclic) GBCA should be used, as these agents have higher molecular stability and a lower risk of long-term gadolinium retention compared to Group I agents.[21] The GBCA is diluted with sterile saline to a standard concentration, typically 1:200, which corresponds to approximately 2.5 mmol/L.[64] A local anesthetic may be added to the mixture to reduce periprocedural pain. Given concerns about the potential chondrotoxicity of some agents, ropivacaine may be preferred over bupivacaine or lidocaine. The informed consent process for MRA should note that the intra-articular use of GBCAs is an "off-label" application and should mention the potential risks associated with local anesthetics.[64]

A typical MRA solution typically consists of 0.1 mL of a Group II GBCA, 5 to 10 mL of local anesthetic (eg, 0.5% ropivacaine), and 10 to 15 mL of sterile saline. The total injection volume for the glenohumeral joint is typically 10 to 15 mL, which is adequate to distend the joint capsule for optimal visualization of intra-articular structures. Under fluoroscopic or CT guidance, a small, confirmatory injection of 1 to 2 mL of iodinated contrast is first administered to verify intra-articular needle placement. To ensure optimal diagnostic quality due to contrast absorption over time, the MRI scan should be initiated within 90 minutes of the intra-articular injection.[57]

Technique or Treatment

The technical execution of the intra-articular injection is the cornerstone of a successful arthrogram. The choice of image guidance defines the injection procedure, the selection of an anatomic approach, and the composition of the injectate.

Guidance Modalities

The choice of modality used to guide examiners during a shoulder arthrogram is a critical decision point that significantly influences the procedure's efficiency, safety, and patient comfort. While fluoroscopy was the historical standard, ultrasound is now considered an equivalent or even preferred method in many centers.

Ultrasound guidance

Ultrasound guidance involves using a high-frequency linear transducer to obtain real-time images of the needle path in relation to the surrounding soft tissues, including the rotator cuff tendons, biceps tendon, and neurovascular structures.[65] An in-plane approach, where the entire needle shaft and tip are visualized within the imaging plane, is generally preferred as ultrasound is technically easier and associated with fewer injection attempts than an out-of-plane approach.[49] The primary advantages of ultrasound are the complete avoidance of ionizing radiation, its portability, which enables office-based procedures, lower cost, and superior real-time visualization of soft tissues, thereby reducing the risk of iatrogenic injury. Multiple studies have demonstrated that ultrasound guidance is associated with faster procedure times, higher first-attempt success rates, and reduced patient discomfort compared to fluoroscopy.[49] Its primary disadvantage is that ultrasound is more operator-dependent, and image quality can be degraded in patients with a very large body habitus. However, fluoroscopy has been shown to obtain more fluid during aspiration in this specific population.[66]

Fluoroscopic guidance

Fluoroscopic guidance is a technique that uses pulsed x-rays and osseous landmarks to guide the needle into the joint space. Proper needle placement is verified by administering a small volume of iodinated contrast and monitoring its typical distribution throughout the joint space.[50] Its advantages include being a familiar technique to many radiologists, providing excellent visualization of bone and contrast flow, and being less affected by patient body habitus than ultrasound.[66] The principal disadvantages are the requisite exposure of both the patient and medical staff to ionizing radiation, the inability to directly visualize soft tissues at risk, and longer procedural times compared to ultrasound guidance.[67]

Computed tomography guidance

CT guidance is used less commonly, typically in situations where fluoroscopy is unavailable or when exact targeting is necessary relative to complex osseous anatomy or hardware.[68] A higher radiation dose limits its use compared to fluoroscopy, and a lack of real-time, dynamic feedback, which both fluoroscopy and ultrasound provide.[68]

Anatomic Approaches to the Glenohumeral Joint

Several needle pathways can be used to access the glenohumeral joint. The anterior rotator interval and posterior approaches are the most common and have replaced mainly older techniques that carried a higher risk of injury to intra-articular structures. These approaches include:

• Anterior rotator interval approach: This is the most frequently used approach for both ultrasound and fluoroscopic guidance.[50] The patient is positioned supine with the arm in slight external rotation to move the long head of the biceps tendon laterally. The needle is directed into the rotator interval—the triangular space defined by the supraspinatus and subscapularis tendons and the base of the coracoid process. The anterior rotator interval approach is favored for its direct, short path to the joint, which avoids traversing major tendons and allows for the use of shorter needles, enhancing patient comfort.

• Posterior approach: For this approach, the patient is typically positioned prone or seated and leaning forward. The needle is advanced from posterior to anterior, traversing the infraspinatus muscle to enter the joint space between the posterior glenoid labrum and the humeral head.[69] The posterior approach is a common and effective technique, particularly when used with ultrasound guidance, which provides excellent visualization of the posterior joint space and the infraspinatus tendon.[69] The posterior approach is the preferred alternative when anterior pathology, eg, extensive synovitis or surgical hardware, would interfere with an anterior approach.
• Articular recess targeting principle: A unifying concept that enhances the safety and ease of all joint injections is the principle of targeting a capacious articular recess rather than the narrow, cartilage-lined joint space itself.[49] Instead of aiming for the "clear space" between the humeral head and glenoid, which risks iatrogenic damage to the labrum or articular cartilage, the needle is aimed at a recess, eg, along the medial humeral neck or in the inferior axillary pouch. The needle is advanced until it makes gentle contact with bone, providing a definitive depth limit. A slight retraction of 1 to 2 mm then places the needle tip safely within the joint capsule. This technique is technically simpler, inherently safer, and readily applicable to both ultrasound and fluoroscopic guidance.

Injectate Composition

The composition of the arthrographic injectate is not universally standardized and varies by institution, imaging modality (MR versus CT), and radiologist preference. However, modern formulations are guided by principles of safety, efficacy, and patient comfort.

MR arthrography injectate

The following injectate agents may be considered for MRA:

• Standard mixture: The typical injectate is a solution containing a GBCA, sterile saline, and a long-acting local anesthetic (eg, ropivacaine, bupivacaine).[49] The local anesthetic serves a dual purpose of providing analgesia during and after the procedure, and as a diagnostic block, confirming an intra-articular source of the patient's symptoms if a successful test injection relieves their primary pain.
• Gadolinium: A highly dilute concentration of GBCA is used, typically a 1:200 or 1:250 dilution in saline, to achieve a final concentration of approximately 0.002 to 0.0025 mmol/mL.[49] Recognizing that the intra-articular administration of GBCAs is considered an off-label use in many jurisdictions, including by the United States Food and Drug Administration (FDA).[64]
• Epinephrine: The addition of epinephrine (eg, 0.3 mL of a 1:1000 solution) is a matter of controversy. While epinephrine acts as a vasoconstrictor to delay the resorption of contrast from the joint, evidence suggests it may increase the incidence and severity of postprocedural pain due to synovial irritation.[70] However, many centers now omit it, particularly when the time between injection and MRI is short.
• Emerging agents: Due to concerns about gadolinium deposition and the off-label use of gadolinium in intra-articular applications, new contrast agents are being developed. Recent studies on iron-based positive T1 contrast agents (eg, NEMO-103) have shown comparable or even superior image quality to GBCAs for shoulder MRA, offering a potential on-label alternative in the future.[64]

CT arthrography injectate

The injectate for CTA consists of a nonionic, low-osmolar iodinated contrast agent, sterile saline, and local anesthetic.[71] The iodinated contrast must be diluted, typically to a concentration of no more than 240 mg of iodine per mL, to prevent beam-hardening artifacts on the CT images that could obscure subtle pathology.[49]

Injection volume

The goal is to achieve adequate capsular distention without causing iatrogenic capsular rupture. A typical volume for a shoulder arthrogram is 10 to 16 mL, or until the operator feels a mild increase in resistance to injection. Pathologic conditions can alter the required volume; for example, a patient with adhesive capsulitis has a contracted, low-volume capsule and may only accept 5 to 7 mL, whereas a patient with chronic instability may have a capacious capsule that accepts a larger volume.

Postinjection Image Acquisition Protocols

Direct MR arthrography

The following should be considered when performing direct MRA:

• Timing: To ensure optimal joint distention and contrast concentration, the MRI scan should be performed promptly after the injection, ideally commencing within 90 minutes.[57]
• Core sequences: The foundation of an MRA protocol is a set of T1-weighted, fat-suppressed sequences acquired in the standard imaging planes: axial, oblique sagittal (parallel to the glenoid face), and oblique coronal (perpendicular to the glenoid face). These sequences provide the highest contrast between the bright intra-articular fluid and the surrounding low-signal labrum and tendons.[64]
• Adjunctive sequences
  • A nonfat-suppressed T1-weighted sequence, typically in the oblique sagittal plane, is essential for assessing fatty infiltration of the rotator cuff musculature, a key prognostic indicator.[64]
  • A fluid-sensitive, fat-suppressed sequence (eg, proton density or T2-weighted) is valuable for detecting pathology characterized by increased water content, eg, bone marrow edema, muscle edema, or tendinosis, which are less conspicuous on T1-weighted images.[64]
• ABER (abduction and external rotation) position
  • Nuanced application: The ABER position is a specialized sequence, not a routine addition to all protocols. It requires positioning the patient with their arm abducted and externally rotated (often with the palm placed behind the head) and acquiring oblique axial images.
  • Proven benefit: This position specifically tensions the anteroinferior capsuloligamentous structures. ABER has been shown to significantly increase sensitivity for detecting pathology of the anteroinferior labroligamentous complex, eg, Bankart lesions and their variants (eg, Perthes lesions), by separating the torn labrum from the glenoid rim.[72]
  • No proven benefit: In contrast, evidence shows that the ABER position does not improve the diagnostic accuracy for detecting rotator cuff tears.[72]
  • Recommendation: The ABER sequence should be reserved for cases where shoulder instability or a tear of the anteroinferior labrum is the primary clinical concern. Its use should be targeted to balance its diagnostic yield against the increased scan time and potential patient discomfort.

CT arthrography

The following should be considered when performing CTA:

• Technique: The key to high-quality CTA is the use of a multidetector CT (MDCT) scanner to acquire an isotropic volumetric dataset, meaning the voxels are of equal dimension in all 3 axes (eg, 0.625 mm x 0.625 mm x 0.625 mm).[71]
• Reformats: This isotropic raw data enables the generation of high-quality multiplanar reformats (MPRs) in any plane without loss of spatial resolution. Oblique coronal and oblique sagittal reformats, prescribed parallel and perpendicular to the glenoid articular surface or the long axis of the supraspinatus muscle, are essential for a complete diagnostic evaluation.

Indirect MR Arthrography

Indirect MR arthrography involves the intravenous injection of a standard dose of a gadolinium-based contrast agent, followed by a delay of 5 to 15 minutes, during which the patient exercises the shoulder to facilitate the diffusion of contrast from the bloodstream into the joint fluid. While less invasive than a direct injection, its clinical utility is limited, and it has been largely superseded.[73] Its significant drawbacks include:

• Unpredictable and often insufficient intra-articular contrast enhancement.
• Lack of joint distention. Distention of the joint is a significant benefit of the direct arthrography method for evaluating the labrum and capsule.
• Confounding enhancement of other structures, such as synovium, granulation tissue, and blood vessels, which can be misinterpreted as pathology.
• Inability to consistently demonstrate abnormal communications between the joint and adjacent bursae, as both spaces enhance simultaneously.

Postprocedural Care and Complication Management

Clear postprocedural instructions should be provided to the patient both verbally and in writing before they leave the department. Patients should be advised to use over-the-counter analgesics (eg, acetaminophen or NSAIDs, if not contraindicated) and apply ice packs as needed to manage the expected delayed-onset shoulder pain.[70] Reassuring patients that this is an expected adverse effect, which should begin to improve within 24 to 48 hours and resolve over several days, is essential.

Additionally, patients must be given clear "red flag" instructions. They should be advised to seek immediate medical evaluation for severe, worsening pain that persists beyond 48 to 72 hours, particularly if other warning signs appear, eg, fever, chills, malaise, or redness and swelling of the shoulder. These symptoms are highly concerning for septic arthritis and constitute a medical emergency requiring urgent assessment, potentially including joint aspiration and antibiotic therapy. Patients should be advised to avoid strenuous activity or heavy lifting with the affected arm for 24 to 48 hours to minimize discomfort. Minimizing activity does not decrease contrast leakage from the joint.[74]

Complications

The primary risks of shoulder arthrography include postinjection joint pain (chemical synovitis), vasovagal reactions, and hypersensitivity reactions to the contrast agent or other medications. More severe but exceedingly rare complications include septic arthritis and bleeding. The risk of chondrolysis (cartilage damage) is a significant concern, but shoulder arthrography has been primarily associated with the continuous postoperative infusion of local anesthetics—a practice that is significantly different from diagnostic arthrography.[75]

Septic Arthritis

Septic arthritis is an exceedingly rare but serious complication, with a reported incidence of approximately 0.003%.[76] The most critical preventative measure is the strict adherence to aseptic technique throughout the procedure. While systemic conditions, eg, diabetes mellitus and rheumatoid arthritis, are known risk factors for joint infections [77], procedural integrity is paramount. Lapses in environmental control have been reported as a source of infection, underscoring the need for a dedicated, clean procedural setting.[78] Prophylactic antibiotics are not recommended. Patients should be instructed to report any signs of infection, eg, fever, chills, or escalating joint pain and swelling.

Chemical Synovitis

The most common adverse event is a transient, postinjection chemical synovitis, which affects approximately 66% of patients.[79] This discomfort is an expected adverse effect, not a rare complication. Chemical synovitis has a characteristic delayed onset, with pain typically peaking around 4 hours after the injection and resolving to baseline levels within 1 week.[80] The average pain intensity is moderate (approximately 4.8/10) and is often more pronounced in patients younger than 30.[70] Management is supportive, consisting of rest, ice, and over-the-counter anti-inflammatory medications.

No confirmed cases of NSF have been identified following the intra-articular administration of a GBCA. This exceptional safety record is due to the minimal, nonsystemic dosage used and the development of highly stable macrocyclic (Group II) GBCAs, which have virtually eliminated new cases of NSF even in high-risk patients receiving intravenous doses.[21] While gadolinium deposition in tissues has been identified as a concern with repeated systemic GBCA administration, the risk from a single, low-dose intra-articular injection is considered theoretical and negligible.[21]

Technical Failure

Technical failure resulting in extra-articular contrast can occur, but is minimized with image guidance. Other potential adverse events include mild hypersensitivity reactions, such as urticaria (hives), and vasovagal episodes, which are typically benign and self-limiting.[81]

Clinical Significance

Arthrogram With Normal Findings

The interpretation of a normal arthrographic study relies on understanding the high-resolution, multiplanar appearance of intra-articular anatomy enhanced by contrast.

On an MRA with normal findings, the intra-articular structures are clearly delineated. The gadolinium-based contrast solution appears bright on T1-weighted images, providing a stark background against which the low-signal-intensity (dark) structures are visualized. Structures visualized include:

• Glenoid labrum: Appears as a sharp, dark, triangular structure firmly attached to the glenoid rim. Its edges are smooth and well-defined. The superior labrum may have a more variable, meniscoid appearance, and a smooth, narrow sulcus between the biceps anchor and the superior labrum can be a normal finding.[82]
• Glenohumeral ligaments and capsule: The superior, middle, and inferior glenohumeral ligaments are visible as thin, dark bands thickening the joint capsule. The axillary pouch should appear as a smooth, redundant fold inferiorly, which becomes taut in abduction.
• Articular cartilage: Covers the humeral head and glenoid fossa as a smooth layer of intermediate signal intensity, distinct from both the bright intra-articular contrast and the dark subchondral bone.
• Biceps tendon: The long head of the biceps tendon is a round, dark structure seen coursing from its anchor on the superior labrum, through the rotator interval, and into the bicipital groove, surrounded by a contrast-filled synovial sheath.

On a typical CTA, the interpretation is based on density differences. The iodinated contrast appears hyperdense (bright white), outlining the articular surfaces. Structures visualized include:

• Glenoid labrum and capsule: These soft-tissue structures are visible as intermediate-density triangular and linear structures, respectively, outlined by the high-density contrast. Their morphology can be assessed, though intrinsic tissue characterization is limited compared to MRA.[71]
• Articular cartilage: Appears as a smooth, low-to-intermediate density layer covering the osseous surfaces, clearly demarcated by the adjacent hyperdense contrast. CTA is considered excellent for evaluating the cartilage surface.[41]
• Osseous structures: The subchondral bone of the glenoid and humeral head is exquisitely depicted, allowing for precise evaluation of bony contours and integrity, which is a primary strength of CT.[83]

Rotator Cuff Tear Arthrogram Findings

The clinical significance of an abnormal arthrogram is best understood by organizing findings according to the underlying clinical problem. While noncontrast MRI and ultrasound are highly accurate for diagnosing full-thickness rotator cuff tears, MRA and CTA are particularly valuable for assessing partial-thickness tears, evaluating the postoperative cuff, and providing key prognostic information.[84] The focus of modern reporting has shifted beyond simple diagnosis to include features that predict treatment outcomes.

Tear diagnosis

The following are the tear classifications:

• Full-thickness tear: Diagnosed by the direct visualization of contrast material extending from the glenohumeral joint through the full thickness of the tendon into the overlying subacromial-subdeltoid bursa on MRA or CTA.[85] The simple presence of bursal contrast is suggestive but must be correlated with a visible defect in the tendon.
• Partial-thickness tears (subclassified by their location)
  • Articular-surface tears: Articular-surface tears, eg, PASTA (Partial Articular Supraspinatus Tendon Avulsion), are the most common type of partial tear. On MRA, they appear as contrast extending into the articular surface of the tendon.[36] MRA is more sensitive than noncontrast MRI for these lesions because the joint distension forces contrast into the tear.[86]
  • Bursal-surface tears: These tears are less common and more difficult to diagnose with arthrography, as the contrast is injected on the articular side. They are better visualized on noncontrast MRI fluid-sensitive sequences (eg, T2-weighted images) or with direct subacromial bursography, which is rarely performed.
  • Intrasubstance tears: These do not communicate with either surface and are also best seen on noncontrast MRI as areas of intrinsic high signal within the tendon.

Prognostic imaging findings

The clinical significance of a rotator cuff tear is defined not just by its presence, but by features that affect the potential for healing after repair. A comprehensive report must include:

• Tear size and retraction: Tears are classified based on the degree of medial retraction of the torn tendon edge (eg, retracted to the level of the mid humeral head or glenoid) and by their size, with small tears being less than 1 cm, medium tears measuring 1 to 3 cm, large tears spanning 3 to 5 cm, and massive tears exceeding 5 cm.[85] Larger, more retracted tears have a poorer prognosis.

• Fatty infiltration: This refers to the replacement of muscle tissue with fat, a largely irreversible consequence of chronic disuse and denervation that often follows a tendon tear. Fatty infiltration is most commonly graded using the following Goutallier classification on sagittal MRI or CT images:
  • Goutallier classification: Stage 0 (no fat), Stage 1 (some fatty streaks), Stage 2 (more muscle than fat), Stage 3 (equal muscle and fat), and Stage 4 (more fat than muscle).
  • The clinical importance of this finding cannot be overstated. Goutallier stages 3 and 4 are associated with a significantly higher rate of repair failure and poor functional outcomes, as the muscle no longer has the capacity to generate effective force.[87]

• Muscle atrophy: A decrease in muscle bulk is often assessed on sagittal images using the "tangent sign" for the supraspinatus.[88] Atrophy, like fatty infiltration, is a negative prognostic indicator.

Glenohumeral Instability and Labroligamentous Abnormal Findings

The evaluation of shoulder instability is a prime indication for arthrography. The choice between MRA and CTA depends on whether the primary clinical question relates to soft-tissue or osseous injury. Often, both are critical for comprehensive surgical planning. Abnormal findings include:

• Soft-tissue lesions: MRA is the gold standard for delineating the spectrum of injuries to the capsulolabral complex that result from dislocation events, as these lesions are best seen on MRA.[89]
  • Bankart lesion: The classic injury, defined as an avulsion of the anteroinferior labrum and the attached inferior glenohumeral ligament (IGHL) from the glenoid rim. On MRA, contrast is seen extending between the detached labrum and the glenoid.
  • Bankart variants
    • Perthes lesion: A nondisplaced Bankart lesion where the labrum is avulsed with an intact but stripped scapular periosteum. Contrast can be seen beneath the labrum, which remains in a near-anatomic position.[90]
    • ALPSA (anterior labral ligamentous periosteal sleeve avulsion) lesion: The avulsed anteroinferior labroligamentous complex displaces medially and rotates inferiorly, scarring down to the glenoid neck deep to an intact periosteum. This can be a cause of failed Bankart repair if not recognized.[91]
    • GLAD (glenolabral articular disruption) lesion: A superficial tear of the anterior labrum associated with an adjacent chondral injury of the glenoid articular cartilage. The labrum is not typically displaced.[92]
• Capsular avulsions
  • HAGL (humeral avulsion of the glenohumeral ligament) lesion: A tear of the IGHL from its humeral insertion, a key cause of instability that can be missed if not specifically sought. An MRA will reveal that the axillary pouch has lost its typical U-shape, and contrast may be seen tracking along the humeral neck.[93]
• Osseous assessment and the glenoid track concept: The recognition that recurrent instability is often driven by bone loss has revolutionized the management of this condition. While large osseous defects can be visualized on MRA, CT and CTA modalities are considered the gold standard due to their precise quantification capabilities.[94] This assessment is mandatory in cases of recurrent instability or when considering surgery.
  • Hill-Sachs lesion: A compression fracture of the posterosuperior humeral head, caused by impaction against the anterior glenoid rim during dislocation.[95]
  • Glenoid bone loss: A fracture or chronic erosion of the anteroinferior glenoid rim (a "bony Bankart" is the acute fracture fragment). The circle method, applied to CT images, is the standard approach for quantifying bone loss, calculating the percentage of the glenoid that has been lost relative to its total width.[96]
  • The glenoid track concept: This critical concept mathematically relates the size and location of the Hill-Sachs lesion to the amount of glenoid bone loss.[97] The "glenoid track" is the zone of contact between the glenoid and the humeral head during normal motion. If the Hill-Sachs lesion is larger than the glenoid track (an "off-track" lesion), the lesion can engage with the edge of the glenoid during abduction and external rotation, leading to a high risk of redislocation.[94] Imaging, particularly 3D-CT, is used to measure the glenoid track and determine if a lesion is "on-track" or "off-track." This determination directly guides surgical decision-making. "On-track" lesions may be treated with a standard arthroscopic Bankart repair, whereas "off-track" lesions often require a bone-augmenting procedure, eg, the Latarjet procedure, to restore stability.[97]

Superior Labral Anteroposterior Lesions

SLAP lesions are injuries to the superior labrum at and around the anchor of the long head of the biceps tendon. MRA is the preferred imaging modality for their detection.

Snyder classification

The Snyder classification, which divided SLAP lesions based on characteristic findings, has been expanded to 10 types since its origination, including associated injuries; however, the clinical utility and reliability of the expanded classification are debated.[98] The following original classification describes the 4 main types of SLAP lesions, which remains a useful basic framework.[99]

• Type I: This type of lesion is characterized by fraying and degeneration of the superior labrum, with the anchor intact.
• Type II: These lesions are defined by detachment of the superior labrum and the biceps anchor from the glenoid. Type II SLAP lesions are the most common type.
• Type III: A bucket-handle tear of the superior labrum, which is displaced into the joint, but the biceps anchor remains intact, is characteristic of type III lesions.
• Type IV: A bucket-handle tear of the superior labrum that extends into the substance of the biceps tendon is categorized as a type IV SLAP lesion.

MRA findings of superior labral anteroposterior lesions

The key finding of a significant SLAP tear (type II and above) is the visualization of high-signal contrast extending into the substance of the superior labrum and undermining the biceps anchor.[100] This finding should not be confused with a smooth sublabral recess, a common anatomic variant found in the anterosuperior labrum.[82] The presence of a paralabral cyst adjacent to the superior labrum is a highly specific secondary sign of an underlying labral tear.

Management approaches

The diagnosis and management of SLAP lesions are subjects of considerable controversy. One source of debate is the clinical application of these lesions. SLAP-type abnormalities are frequently found on MRI in asymptomatic overhead athletes and middle-aged individuals. This high prevalence in asymptomatic individuals raises questions about the clinical significance of an isolated imaging finding.[100] Additionally, the diagnostic reliability of these lesions is arguable. The arthroscopic diagnosis of SLAP tears has shown poor inter- and intra-observer reliability, making it a challenging diagnosis to standardize.[101] 

A significant trend has emerged away from surgical repair of many SLAP lesions, particularly in patients older than 40. For many cases, biceps tenotomy or tenodesis (releasing or reattaching the biceps tendon outside the joint) provides more reliable pain relief and better outcomes than attempting to repair the labral anchor.[100] Therefore, the "clinical significance" of a SLAP tear on MRA is highly dependent on the patient's age, activity level, clinical symptoms, and the presence of other coexisting pathologies.

Adhesive Capsulitis 

Adhesive capsulitis, also known as frozen shoulder, is a clinical diagnosis characterized by painful, progressive loss of both active and passive shoulder motion.[102] While imaging is used to exclude other pathologies, MRI and MRA can show characteristic findings, and arthrography can also serve a therapeutic purpose.

Diagnostic imaging findings

The classic findings of adhesive capsulitis on MRI and MRA are typically observed in the rotator interval and axillary pouch. These findings include thickening (>3-4 mm) of the joint capsule, which may demonstrate high T2 signal and enhancement after contrast administration, reflecting the underlying synovitis and fibrosis.[103] Thickening of the coracohumeral ligament and obliteration of the fat triangle inferior to the coracoid process are also characteristic signs.[102]

Additionally,  a conventional or CT arthrogram will demonstrate a markedly reduced joint volume. The patient will often experience pain with the injection of a small amount of contrast, and the normal recesses (axillary and subscapularis) will fail to distend.

Therapeutic Arthrography

The arthrogram procedure itself can be therapeutic. The forceful injection of a larger volume of fluid (saline, anesthetic, and corticosteroid), known as hydrodilatation or hydroplasty, aims to distend and mechanically rupture the contracted, fibrotic capsule.[104] Hydrodilatation can lead to a significant improvement in pain and range of motion and is an established treatment option for refractory cases.

Technological Advances

Notably, artificial intelligence (AI) and deep learning are revolutionizing the field of shoulder arthrograms.[105] Deep learning reconstruction can reduce scan times by over 50% while preserving diagnostic quality, making the inclusion of additional valuable sequences, eg, ABER, more practical.[106] Moreover, AI-based diagnostic algorithms demonstrate performance comparable to that of human experts and can serve as powerful decision-support tools, augmenting radiologists' ability to deliver precise and timely diagnoses.[107][108] Enhancing healthcare team outcomes in the modern era thus depends on a systems-based approach that combines human expertise with protocol optimization and the intelligent application of technology.[109] Additionally, technological advancements have revolutionized shoulder imaging. The use of higher-field-strength (eg, 3T) magnets improves image resolution and diagnostic confidence.[110] 

Enhancing Healthcare Team Outcomes

Shoulder arthrography plays a crucial role in diagnosing traumatic shoulder instability, as its diagnostic accuracy directly impacts treatment planning and patient outcomes. Key factors influencing performance include radiologist expertise, protocol optimization with pathology-specific sequences such as the ABER view, and the integration of advanced imaging technologies, including high-field magnets and artificial intelligence.[111] Collaborative interpretation further enhances reliability, supporting the delivery of precise, patient-centered care.

Physicians, general practitioners, and advanced practitioners carry the responsibility of identifying patients who will benefit most from MRA and ensuring that referrals provide a detailed clinical context. Radiologists contribute specialized interpretive skills, with fellowship training and consensus reading improving accuracy.[111] Nurses support patient preparation and monitoring during imaging, while pharmacists ensure safe use of intra-articular contrast. Optimal care depends on coordinated communication across disciplines, where results are shared clearly and decisions tailored to patient-specific pathology. By integrating advanced technology, evidence-based imaging protocols, and team-based strategies, healthcare professionals collectively improve safety, diagnostic confidence, and outcomes for patients with traumatic shoulder instability.