Standing on the Shoulders of Giants: A Review of MRI Arthrography of the Shoulder

Transcription

1 Standing on the Shoulders of Giants: A Review of MRI Arthrography of the Shoulder Poster No.: P-0035 Congress: ESSR 2012 Type: Scientific Exhibit Authors: H. Gajjar, P. A. Tyler, M. Calleja, D. Fox, L. K. Singh; Stanmore/ UK Keywords: Musculoskeletal joint, MR, Arthrography, Athletic injuries, Trauma DOI: /essr2012/P-0035 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 73

2 Purpose The concept of shoulder arthrography was initially introduced in the 1930's by 1 Oberholzer. Its role has evolved from its initial use to assess capsular distortion, assessment of the rotator cuff to its current role in assessing the stabilising structures of the glenohumeral articulation in combination with MRI. Arthrography allows distinction of individual structures by improved soft-tissue contrast and physical separation by the intraarticular fluid. In addition, it allows analysis of the distribution of contrast 2 material in and around the joint. A series of 49 Shoulder MRI arthrograms performed between February 2011 and February 2012 have been reviewed with the purpose of demonstrating the following: Indications for an arthrographic study Techniques of performing the arthrogram Technical elements including scanning protocols and parameters Normal anatomical structures specifically evaluated in the arthrographic technique Normal variants that may simulate pathology Common pathologies encountered with this technique Methods and Materials Not applicable Results Common Indications for MRI shoulder arthrography: Assessment of anatomical structures poorly visualised without arthrography: Labrum Biceps-labral complex Ligaments Rotator interval Joint capsule Improved accuracy in assessment: Page 2 of 73

3 Rotator cuff articular surface pathology Differentiating a partial thickness rotator cuff tear from a full thickness tear Retear in repaired rotator cuff tendons Contraindications for MRI arthrography: Sepsis within or overlying the joint for injection Previous reaction to contrast agents Any contraindication for an MRI study Anticoagulation therapy with an INR >1.2 Pregnancy Low dose aspirin (75mg) is not a contraindication for arthrography. It is our policy that patients receiving larger doses of aspirin or clopidogrel should stop their medication 1 week prior to the injection. Arthrographic Technique Written informed consent is obtained prior to the procedure with the rare risks of infection, haemorrhage and extracapsular injection explained. The probability of temporary increased shoulder pain is explained and advice is given regarding post procedure analgesia. Numerous reliable and safe techniques have been described. The modality used in image 2-4 guidance varies and possibilities include fluoroscopy route of entry is generally either anterior or posterior placement in both approaches varies., ultrasound 4-6,8 5,6 7, CT and MRI. The. The exact location of needle 9 The authors preference is a fluoroscopic guided anterior rotator interval approach. If previous imaging is available for comparison, this is reviewed. The patient is placed in either a supine or supine oblique position. In the supine oblique position, the asymptomatic shoulder is elevated to allow visualisation of the glenohumeral joint space en face as per a Grashy view. Page 3 of 73

4 Fig. 1: Patient positioning for an anterior supine oblique approach targetting the right shoulder. A pillow has been placed under the left shoulder (not visible). Note the right hand is placed in supination and supported with a sandbag. Although some articles have indicated that a supine oblique position endangers the anterior labrum if the middle of the glenohumeral articulation is targetted, this is not the 3 case with a rotator interval approach. The arm is placed in external rotation if tolerable and supported with a sand bag placed in the patient's palm. A neutral position with the thumb facing the ceiling is acceptable if external rotation is not tolerated. A skin entry point is marked at the superomedial quadrant of the humeral head, approximately 5mm from the cortex, with the entry point within the center of the field of view to avoid errors of parallax. Strict aseptic technique is observed. 5-10ml 1% lidocaine (B. Braun Melsungen AG, Germany) is injected into the adjacent soft tissues. A 22G spinal needle is inserted with the hub ideally projected over the needle tip, until resistance is felt when the needle tip abuts the humeral head. It is often useful to rotate the hub to ensure capsular penetration. To minimise the chance of injecting air locules, a few drops of the fluid to be injected is placed in the hub of the spinal needle. 1-2ml Page 4 of 73

5 levobupivicaine (Chirocaine 0.5%. Abbott S.r.l. Italy) is initially injected followed by 1-3ml Iohexal (Omnipaque 300. GE Healthcare AS, Norway). Some resistance may occur if the needle tip firmly abuts the humeral head. Gentle retraction of 1-2mm should reduce resistance. Confirmation of intra-articular placement is determined by visualisation of contrast filling or outlining intra-articular structures. Page 5 of 73

6 Fig. 2: Rotator interval approach. Contrast is noted pooling in the posterior aspect of the joint capsule (long arrow), outlining the glenohumeral articulation (short arrow) and extending medially into the subscapularis recess (double arrow). Page 6 of 73

7 Fig. 3: With further contrast injection, there is filling of the axillary pouch (double arrows), outlining of the undersurface of supraspinatus (arrow) and the biceps-labral complex (long arrow). With further injection, contrast may be seen in the long head biceps tendon sheath. Page 7 of 73

8 A mixture of 15ml prediluted gadopentetate dimeglumine (Magnevist 2mmol/l. Bayer Schering Pharma, United Kingdom) and 5ml o.5% levobupivicaine is prepared and between 10-15ml of this mixture is injected. Injection volume depends on the patient's gender (reduced volume in females), size (reduced volume for smaller patients) and tolerance of the injection. Page 8 of 73

9 Fig. 4: Anterior approach targetting the middle third of the humeral head. Page 9 of 73

10 Fig. 5: Anterior approach targetting the inferior third of the humeral head. Page 10 of 73

11 A posterior fluoroscopic approach can be utilised targetting the middle or inferior third of the humeral head with the patient in a prone oblique position with the symptomatic 2,8 shoulder elevated. The symptomatic shoulder is adducted and placed in internal rotation and the glenohumeral joint is visualised en face. The injection technique is otherwise identical to the anterior approach. Both anterior and posterior ultrasound guided approaches have been described, with the benefit of a lack of ionising radiation. In the more commonly utilised posterior approach, the patient is positioned as for a posterior fluoroscopic injection. A high frequency linear transducer is placed in a transverse plane to visualise the posterior glenohumeral articulation and the posterior labrum. The needle is inserted in the plane of the transducer until the tip abuts the medial aspect of the humeral head. Fig. 6: Transverse ultrasound image at the level of the posterior glenohumeral articulation. The hyperechoic posterior labrum (arrow) and posterior joint capsule (arrowhead) are well visualised. The path of the needle for a posterior approach (long arrow) traverses the infraspinatus tendon. The needle tip should lie adjacent to the hypoechoic humeral head cartilage. Page 11 of 73

12 Iodinated contrast is not used and the initial injection would consist of the premixed gadolinium and local anaesthetic mixture. Injection will not initially results in distention of 6 the posterior capsule as the fluid flows freely anteriorly. There are occasionally findings detected in an MRI arthrographic study directly related to the injection procedure, that could be misinterpreted as pathology. These include injected gas locules, placement of extracapsular contrast and contrast injection into a tendon most commonly the subscapularis with the anterior approach. Fig. 7: T1FS axial image depicting an injected locule of gas adjacent to the biceps tendon. Gas locules can be differentiated from loose bodies by their non-dependant position, rounded shape and sharp border. Page 12 of 73

13 Page 13 of 73

14 Fig. 8: T1FS axial image depicting contrast anterior to the subscapularis tendon. On review of the study, no pathological cause could account for this finding which was interpreted as injection related. Page 14 of 73

15 Fig. 9: T1FS axial image. Contrast is visualised within the subscapularis tendon (arrow) related to injection technique. Numerous variations in contrast mixture for the arthrographic study have been described. In some institutions, a single mixture including local anaesthetic, iodinated contrast and dilute gadolinium is injected. An alternative technique involves omitting gadolinium and utilizing fluid sensitive sequences eg. PD or T2 fat suppressed sequences. MRI Protocols and Technical Factors: Our scans are performed on a Philips Achieva 1.5T magnet. The patient is imaged in a supine position with the affected shoulder adducted with mild external rotation. Flex coils are positioned to encase the shoulder. The coronal oblique slices are planned parallel to the supraspinatus tendon, with the sagittal slices orientated perpendicular to the coronal sequence. Sequence FOV Slice thickness/ gap Matrix TE/TR Scan time T1 FS 160 3/ x / mins 160 3/ x / mins FS 160 3/ x / mins 160 3/ x / mins PD coronal 160 oblique 3/ x / mins PD sagittal 160 oblique 3/ x / mins STIR coronal oblique 3/ x / mins axial T1 FS coronal oblique T1 sagittal oblique PD axial 160 TI 150 Page 15 of 73

16 If an abduction external rotation (ABER) view is required, the patient is asked to place the hand under their head on the affected side. Slices are prescribed angled along the line of the humeral shaft to include the whole of the humeral head and gleno-humeral joint laterally. Sequence FOV Slice thickness/ gap Matrix TE/TR Scan time ABER 140 3/ x / mins T1 FS Numerous protocols have been described for MRI shoulder arthrography. One valuable technique involves substituting some of the T1 FS sequences with PD FS sequences to improve sensitivity for internal rotator cuff signal and bursal surface pathology. Normal Arthrographic Anatomy: Anatomical structures well demonstrated on non-arthrographic MRI will not be discussed. The structures that require an arthrogram for optimal assessment include the: Capsule and ligamentous structures Glenoid labrum Biceps-labral complex Rotator interval and biceps pulley Capsule and Ligamentous Structures: The glenohumeral ligaments are thickened bands of the anterior joint capsule with attachments to both the glenoid margins and the proximal humerus. These structures are 10 normally lax and can be considered check reins on extremes of movement. Inferior Glenohumeral Ligament (IGHL): The largest and most important of the glenohumeral ligaments Consists of an anterior and posterior band and axillary pouch Originates from the glenoid labrum or neck and inserts onto the humeral neck at the periphery of the articular margin Page 16 of 73

17 Taut in abduction and external rotation where it occupies a more anterior and superior location relative to the humeral head Is the primary restraint of anterior and posterior dislocations at 90 degrees of abduction Page 17 of 73

18 Fig. 10: T1FS sagittal image demonstrating the anterior band (single arrow) and posterior band (double arrow) of the inferior glenohumeral ligament. Page 18 of 73

19 Fig. 11: PD sagittal image demonstrating the normal axillary pouch (arrow). Page 19 of 73

20 Fig. 12: T1FS ABER view demonstrating a taut, intact IGHL (double arrow) and inferior labrum (arrow). Page 20 of 73

21 Middle Glenohumeral Ligament (MGHL): Great variation in size and thickness Originates from the superior labrum below the origin of the superior glenohumeral ligament and scapular neck Attaches medially to the lesser tuberosity 10 Is poorly defined or absent in 30% of patients Has a role in stability from 0-45 degrees of abduction Page 21 of 73

22 Fig. 13: T1FS sagittal image demonstrating a normal middle glenohumeral ligament. Page 22 of 73

23 Fig. 14: T1FS axial image demonstrating a normal middle glenohumeral ligament. Superior Glenohumeral Ligament (SGHL): Page 23 of 73

24 Small calibre ligament Originates from the upper pole of the glenoid and base of the coracoid process Attaches just superior to the lesser tuberosity in the region of the bicipital groove Together with the coracohumeral ligament, forms the biceps pulley Page 24 of 73

25 Fig. 15: PD sagittal image demonstrating the superior glenohumeral ligament (single arrow) and coracohumeral ligament (double arrow) which form the biceps pulley. Page 25 of 73

26 The Glenoid Labrum: The labrum is the fibrous attachment of the glenohumeral ligaments and capsule to the glenoid rim. It consists of fibrocartilage, is ovoid and conforms to the kidney-shaped glenoid rim. The labrum increases the depth and surface area of the glenoid fossa to 10 better accommodate the humeral head. The anterior labrum provides the major area of attachment for the anterior band of the IGL. A six quadrant system is used to describe the location of a subsection of the glenoid labrum. Page 26 of 73

27 Fig. 16: T1FS sagittal image. A six quadrant system provides useful nomenclature for describing the location of a labral lesion. Page 27 of 73

28 There is significant variation in the size, shape and configuration of the labrum. It is useful when analysing the labrum to subdivide it utilising the glenoid equator or physeal line, located at the junction of the upper and middle thirds of the glenoid fossa. Page 28 of 73

29 Fig. 17: T1FS axial image depicting a normal slightly rounded anterior (arrow) and posterior (double arrow) labrum. Above the physeal line, there is significant variability in the attachment of the labrum. At the biceps-labral complex (BLC), where the long head of biceps tendon becomes contiguous with the superior labrum, three types of attachment to the glenoid are found: Type 1 attachment: The labrum is firmly adherent to the glenoid. Type 2: The BLC attaches several millimeters medial to the sagittal plane of the glenoid. This results in a small sulcus at the superior pole of the glenoid termed the biceps-labral sulcus or sublabral sulcus. Type 3: A meniscoid labrum with a large sulcus. Page 29 of 73

30 Fig. 18: T1FS coronal image depicting a type 1 BLC. Note the absence of a sulcus between the labrum and glenoid rim. Page 30 of 73

31 Fig. 19: T1FS coronal image demonstrating a type 2 BLC with a sulcus between the labrum and glenoid rim. Note the sulcus is smooth, well defined, follows the contour of the glenoid rim and is less than 3mm in diameter (medial to lateral). Page 31 of 73

32 Fig. 20: T1FS coronal image depicting a type 3 BLC with a meniscoid labrum and prominent biceps-labral sulcus. Page 32 of 73

33 A biceps-labral sulcus should be distinguished from a superior labral anterior to posterior tear (SLAP). A sulcus has the following features: Smooth and well-defined with no extension of contrast into the labrum Follows the contour of the glenoid rim Must measures less than 5mm in medial to lateral diameter and is usually less than 3mm in diameter 10 The sublabral foramen is an area of lack of attachment of the glenoid labrum in the anterosuperior quadrant. It has been reported in 11-17% of individuals and can vary in size from a few millimeters up to the entire anterosuperior quadrant above the level of the subscapularis tendon. Note that this foramen is never located below the equator. Page 33 of 73

34 Fig. 21: T1FS axial image depicting a sublabral foramen (arrow) as an area of nonattachment of the anterosuperior labrum. Page 34 of 73

35 The Buford complex has been described in 1.5% of shoulder arthroscopies and consists of: A cord like MGHL MGHL that attaches directly to the superior labrum anterior to the biceps An absent anterosuperior labrum Fig. 22: T1FS axial (left) and sagittal (right) images demonstrating the features of a Buford complex. The thickened cord-like MGHL (arrow) attaches directly to the superior labrum and the anterosuperior labrum is hypoplastic (double arrow). A high attachment of the anterior band of the IGHL can be mistaken for a labral tear. In this variant, the anterior band attaches at or above the equator and the anterosuperior labrum is attenuated or absent. Analysing consecutive images of the anterior labrum from inferior to superior will assist in recognising this variant. Page 35 of 73

36 Fig. 23: T1FS sagittal images demonstrating a high attachment of the anterior band of the IGHL (double arrow). Note the normal course of the MGHL (arrow). Page 36 of 73

37 The Rotator Interval: The rotator interval is a triangular area of tissue that functions to allow movement around the coracoid process. It is bordered by the: Supraspinatus tendon above Cranial aspect of subscapularis below Base of the coracoid medially Transverse humeral ligament laterally The biceps pulley is located in the interval and consists of the coracohumeral ligament and SGHL which function as a sling to stabilise the biceps tendon. The SGHL is initially located anterior to the tendon and subsequently arches posteroinferiorly to form the floor of the pulley. The coracohumeral ligament (CHL) originates from the lateral aspect of the base of the coracoid and forms the roof over the biceps tendon. Fig. 24: PD coronal (left) and sagittal (right) images demonstrate the CHL (double arrows) which in combination with the SGHL (arrow) support the biceps tendon (arrowhead) within the biceps pulley. The lateral band of the CHL inserts on the greater tuberosity and anterior border of supraspinatus. The smaller medial band inserts on the lesser tuberosity, the superior fibres of subscapularis and the transverse ligament. Page 37 of 73

38 Common Pathological Entities: Glenohumeral Instability: Glenohumeral instability may be classified by its aetiology (traumatic, atraumatic and microinstability) and its direction (unidirectional or multidirectional). In our practice, it is the most common indication for an arthrographic study. Traumatic instability is typically unidirectional with an anterior direction in approximately 95% of cases. It usually follows a single episode of dislocation and may then become recurrent. It is often referred to by the acronym TUBS (traumatic, unidirectional, Bankart, surgery). Atraumatic instability is typically multidirectional and is often seen in patients with congenital hypermobility syndromes. It is often referred to by the acronym AMBRI (atraumatic, multidirectional, bilateral, rehabilitation, inferior capsular shift [if surgery is required]). Stability of the glenohumeral joint depends on both dynamic and static factors. Dynamic stabilises include the rotator cuff muscles. Static stabilisers include the bony glenoid and hyaline cartilage, the glenoid labrum, the glenohumeral ligaments and the joint capsule. Anterior subcoracoid dislocation results in a specific pattern of pathological lesions 11 comprising a variable combination of soft-tissue and bony injuries. These common entities are discussed below. Anteroinferior Labral Tears: Anterior labral pathology in the anteroinferior quadrant may vary based on the degree of involvement of the anterior inferior labrum, the scapular periosteum, the IGHL, the osseous glenoid rim and the articular cartilage of the anterior inferior glenoid and displacement of the anterior labrum. The most common lesion is the soft tissue Bankart, named after Mr A.S. Blundell Bankart, an orthopaedic surgeon who practiced at the RNOH for most of his career. It 11 is seen in approximately 74% of patients following an anterior dislocation. This lesion is characterised by avulsion of the anteroinferior labrum with disruption of the scapular periosteum without fracture of the glenoid rim. Arthrographic findings include: Page 38 of 73

39 An avulsed anteroinferior labrum, resulting in a bare anterior glenoid rim Linear contrast medium extending between the labrum and glenoid rim and possibly into the labral substance A blunted labrum resulting in an altered contour Fig. 25: T1FS axial (left) and sagittal images (right). A classic soft tissue Bankart lesion is demonstrated with separation of the labrum from the glenoid rim (arrow) and disruption of the scapular periosteum (arrowhead). In addition, adjacent glenoid chondral high signal and delamination is visible on the axial image. An osseous Bankart presents with a variably sized anteroinferior glenoid rim fracture that may extend anterior and superior to the equator. Page 39 of 73

40 Fig. 26: PD axial image depicting a large fracture of the anteroinferior rim with attached labral tissue (arrow) consistuting a bony Bankart Page 40 of 73

41 It is important to differentiate between an acute and chronic bony Bankart lesion. In acute lesions, there is increased signal in the subchondral bone of the glenoid on fluid sensitive sequences. Chronic lesions can heal with hypertrophic bone and maintain stability, depending on the size of the fracture. A bony Bankart that results in a loss of the normal 'pear shape' of the glenoid is considered clinically relevant and often results in recurrent dislocations. Fig. 27: T1FS sagittal image on the left demonstrating a chronic bony Bankart (arrow) with loss of the normal 'pear shape', in comparison with the normal glenoid morphology on the right (arrowhead). The mass of tissue inferior to the bony Bankart (double arrow) consists of the avulsed labrum, capsule and IGHL. Note the lack of visualisation of the MGHL associated with this injury. The Perthes lesion is a Bankart variant consisting of labral ligamentous avulsion with an intact scapular periosteum. The IGHL and labrum are positioned normally relative to the underlying glenoid. This lesion can be subtle and an ABER view will assist in its detection. Page 41 of 73

42 Fig. 28: T1FS axial image demonstrating a Perthes lesion. Contrast extends between the labrum and glenoid rim (arrow) but the scapular periosteum is intact (arrowhead). Page 42 of 73

43 An anterior labroligamenous periosteal sleeve avulsion (ALPSA lesion) is also termed a medialised Bankart. It represents an avulsion of anterior scapular periosteum with the attached anteroinferior labrum and IGHL. It differs from the Bankart lesion in that the periosteum, although avulsed from the glenoid, is intact. This results in marked medial and inferior rotation of the labroligamentous structures. Chronic lesions typically scar down in an inferior and medially displaced location. Page 43 of 73

44 Fig. 29: PD axial image depicting a chronic ALPSA scarred down medial to the anteroinferior glenoid rim (arrow). Page 44 of 73

45 Glenolabral articular disruption (GLAD) is caused by impaction of the humeral head against the anteroinferior glenoid and comprises a superficial tear of the anteroinferior labrum with an anterior inferior glenoid articular cartilage injury. Page 45 of 73

46 Fig. 30: PDFS axial image demonstrates a GLAD lesion. There is a shallow anteroinferior labral tear (arrow) with adjacent disruption of the articular cartilage (arrowhead). Capsular-Related Lesions: Humeral avulsion of the glenohumeral ligament (HAGL lesion) is significantly less frequent than the classic Bankart as a cause of anterior shoulder instability. It is often associated with a severe dislocation and has been reported in % of patients with anterior dislocation, usually in males patients involved in contact sports or those with a 11 first episode of dislocation over the age of 35 years. The axillary pouch is converted from a fluid distended U-shaped structure to a J-shaped structure as the IGHL drops inferiorly. Direct extension of contrast or fluid between the humerus and the avulsed IGHL is another valuable sign. Page 46 of 73

47 Fig. 31: T1FS coronal image demonstrating a HAGL lesion. The IGHL has been avulsed from the humerus (long arrow) resulting in a J-shaped axillary pouch (short arrows). Page 47 of 73

48 Fig. 32: T1FS sagittal image demonstrating a HAGL lesion. There is disruption of the anterior aspect of the axillary pouch and anterior band of the IGHL (long arrow). A Page 48 of 73

49 normal well defined, intact capsular-ligamentous contour is evident posteriorly (short arrows). There are a number of variants of IGHL disruption. Rarely, the IGHL avulsion is associated with a bony humeral fragment termed a bony HAGL (BHAGL). Glenoid avulsion of the IGHL without associated disruption of the inferior labrum is uncommon and termed a GAGL. Axillary pouch mid-ligament tears and sprains are uncommonly seen with disruption or hyperintensity and thickening of the axillary pouch respectively. Adhesive capsulitis, which is more common than post traumatic axillary pouch strain, can present with identical findings but can be differentiated by the clinical history. Bony Lesions following anterior dislocation: The Hill-Sachs deformity also termed a Broca lesion results from an impaction fracture of the posterolateral humeral head against the anteroinferior glenoid rim and may be cartilaginous or osteocartilaginous. Its incidence based on arthroscopy following firsttime anterior dislocation is reported as per cent. Defects that are less than onethird of the humeral circumference are regarded as prognostically insignificant but larger lesions, particularly if orientated parallel to the glenoid are more likely to result in repeated 11 dislocation. An acute Hill-Sachs deformity may be associated with bone bruising. Page 49 of 73

50 Fig. 33: PD axial image demonstrating a typical Hill-Sachs deformity (arrow) with a small defect in the posterosuperior aspect of the humeral head. Page 50 of 73

51 Fig. 34: STIR coronal image demonstrating a large chronic Hill-Sachs deformity (arrow) with adjacent bone bruising (double arrows) related to a more recent episode of dislocation. Page 51 of 73

52 Fig. 35: T1FS coronal images demonstrating the spectrum of findings in a Hill Sachs lesion. The image on the left depicts an isolated chondral Hill Sachs lesion (arrowhead). On the right, a large osteochondral loose body in the axillary recess (arrow) is related to a large Hill Sachs lesion that is partially visible on this image (double arrows). A Hill-Sachs deformity must be differentiated from the normal bare area of bone where the capsule attaches laterally to the anatomical neck of the humerus posteriorly. This area shows normal flattening of the posterior aspect of the humeral head in its inferior 10 portion. Normal posterolateral cysts and erosions can be found in this area. If the bony abnormality is not visible on the first two cranial slices of the humeral head above the level of the great tuberosity (correlation with coronal imaging required) caution should be maintained in diagnosing a Hill-Sachs lesion. Page 52 of 73

53 Fig. 36: T1FS axial image demonstrating the normal flattened contour of the bare area (arrow). Note that this slice is too caudal to diagnose a Hill-Sachs lesion. Page 53 of 73

54 Posterior Instability: Posterior dislocation is uncommon and usually results from violent muscle contraction associated with an epileptic seizure or electric shock. Pathological lesions in posterior dislocation are of a similar spectrum to that found in anterior dislocation but their location differs. A reverse Bankart lesion is a common finding involving the posteroinferior labrum. A reverse Hill-Sachs lesion may be seen at the anterior aspect of the humeral head, which often has a vertical orientation in the sagittal plane due to impaction of the lesser tuberosity on the posterior glenoid rim. This has been termed a notch or trough sign. Analogous to the HAGL lesion, a posterior or reverse HAGL lesion is sometimes seen. Page 54 of 73

55 Fig. 37: PD axial image demonstrating a chronic combined bony and soft tissue reverse Bankart lesion (arrow) and reverse Hill-Sachs lesion (long arrow). Page 55 of 73

56 Fig. 38: T1FS coronal (left) and sagittal images (right) depicting a reverse HAGL lesion (arrow). The findings are similar to a HAGL lesion as described above, but involve the posterior band of the IGHL and posterior aspect of the axillary recess. Note the intact anterior band of the IGHL (double arrow). Posterior instability may also result from recurrent micro-trauma in the throwing athlete or those involved in overhead activities eg. swimmers. The condition is typically unilateral and affects the dominant arm. A common finding in this group of patients is the posterior peel-back lesion. This is a posterior SLAP 2 lesion and can extend posteroinferiorly as a posterior labral tear. Page 56 of 73

57 Fig. 39: T1FS axial imaging depicting a subtle posterior peel-back lesion. A linear high signal cleft (arrow) separates the posterosuperior labrum from the glenoid rim. Page 57 of 73

58 Other findings include rotator cuff injuries from secondary impingement particularly affecting the conjoined tendon, posterior humeral head subluxation and a posterior eccentric glenohumeral wear pattern. Atraumatic Instability: This condition is also referred to as multidirectional instability (MDI) or AMBRI. It may be seen in both athletic and non-athletic individuals with excessive capsular laxity and 10 the incidence is higher in females. A structural lesion is usually not found. A capacious subscapularis recess can be seen with excessive labroligamentous laxity and absence of the MGHL. In non-athletes the anteroinferior labrum is typically normal, whereas in athletes the labrum may be hypoplastic, torn or degenerative. Paralabral Cysts: Paralabral cysts can develop in association with a glenoid labral tear, due to passage of joint fluid through the tear into the adjacent soft tissues. They may be unilocular or multiseptated and may arise in a variety of locations but are most common superiorly and posteriorly. Paralabral cysts do not typically fill with intra-articular contrast and be missed if only T1FS images are acquired. Cyst extension into the suprascapular and/or spinoglenoid notch may cause a compressive neuropathy of the suprascapular nerve. Page 58 of 73

59 Fig. 40: T1FS axial image (left) and PD coronal image (right) demonstrate a posterior paralabral cyst (arrows) associated with a small posterior labral tear visible only on the axial image. Contrast is noted within the cyst on the T1FS image which is uncommon. The humeral head is subluxed posteriorly, relative to the glenoid. Superior Labral Tears: Assessment of SLAP or superior labrum from anterior to posterior tears is a common indication for MRI arthrography. These lesions are relatively common in athletes, usually resulting from repetitive traction or torsion injury to the biceps tendon (types 1 and 2) or 11 a fall onto the outstretched arm or flexed elbow (types 3 and 4). Normal variants of the superior and anterosuperior labrum may be mistaken for a SLAP lesion. Guidelines that improve accuracy for SLAP detection include: The biceps labral sulcus always measures <5mm and usually measures <3mm in transverse dimension on coronal imaging A biceps labral sulcus is well defined and follows the contour of the glenoid rim There should not be high signal intensity located between the intra-articular biceps and the superior labrum on a coronal image that includes the inferior glenoid rim. A normal high signal cleft is visible anterior to the biceps labral junction Contrast should not extend into the labral substance A superior paralabral cyst usually communicates with a classic SLAP 2 or posterior component of a SLAP 2 lesion SLAP 1: Superior labral degeneration and fraying. Common in older individuals and should not be labelled as a labral tear. Page 59 of 73

60 Fig. 41: PD coronal image demonstrating subtle intralabral high signal and irregularity (arrow) consistent with labral degeneration (SLAP 1). Page 60 of 73

61 SLAP 2: The commonest type of SLAP lesion. Separation of the superior labrum and biceps anchor from the glenoid labrum. Variants of a SLAP 2 include the posterior peelback where the tear involves only the posterior aspect of the superior labrum and the SLAC lesion where an anterior SLAP 2 lesion is associated with an anterior supraspinatus articular-side partial thickness tear. Page 61 of 73

62 Fig. 42: T1FS coronal image depicting a SLAP 2. Contrast material is noted between the superior labrum and the intra-articular biceps tendon (arrow). High signal is also noted between the irregular labrum and glenoid which does not follow the contour of the glenoid rim. Page 62 of 73

63 Page 63 of 73

64 Fig. 43: PD coronal image depicting a SLAP 2 lesion. Linear high signal is noted between an irregular labrum and glenoid rim (arrow). High signal is also noted extending into the labral substance. SLAP 3: A bucket-handle tear of the superior labrum without extension into the biceps tendon. The inferiorly displaced labral fragment may become entrapped in the glenohumeral joint. Page 64 of 73

65 Fig. 44: PD coronal image demonstrating an inferiorly displaced bucket-handle labral fragment (long arrow) with some intact labral tissue (arrow), constituting a SLAP 3. Page 65 of 73

66 SLAP 4: Bucket-handle tear of the superior labrum but extending to involve the biceps tendon. Fig. 45: T1FS coronal image depicting extension of a bucket-handle SLAP tear to involve the biceps tendon (arrows) in keeping with a SLAP 4. References: Saifuddin A. Musculoskeletal MRI. London: Hodder Arnold; 2008 Six additional SLAP tear subtypes have been described (SLAP 5-10) and will not be discussed as they have been well demonstrated on a previous presentation. Rotator Cuff Pathology: MR arthrography is used at our institution as a problem solving tool in difficult cases with regard to the assessment of the rotator cuff. Ultrasound and conventional MRI are usually sufficient for the assessment of non-complex rotator cuff pathology. The addition of intra-articular contrast improves detection of articular surface cuff pathology 12 and can assist in differentiation a partial thickness tear from a full thickness tear. This Page 66 of 73

67 differentiation is important with regard to surgical planning and management. Contrast within the subacromial space is an important finding in the non-operative shoulder and care must be taken to seek a cause eg. a small full thickness tear. Page 67 of 73

68 Fig. 46: T1FS coronal image demonstrating a small partial thickness articular surface supraspinatus tear (arrow) with adjacent fraying. The appearance of the biceps-labral complex is related to previous biceps tenodesis. Page 68 of 73

69 Fig. 47: PD coronal image demonstrating a partial thickness articular surface tear of the conjoined tendon (junction of supraspinatus and infraspinatus tendons) with delamination and retraction (arrow). Page 69 of 73

70 Fig. 48: T1FS coronal image depicting a subtle obliquely orientated full thickness tear of the supraspinatus tendon. The articular surface component is depicted with an arrow and the bursal surface component with adjacent contrast extension into the subacromial bursa is depicted with an arrowhead. Although debatable, some studies have demonstrated that an arthrographic study improves assessment of the rotator cuff post surgery. Contrast may enter recurrent tears that are obscured by granulation tissue on conventional MRI studies. The repaired rotator cuff is not usually water tight and thus contrast in the subacromial space may not be of significance. Page 70 of 73

71 Fig. 49: T1FS coronal image depicting an extremely attenuated supraspinatus tendon post repair. Artefact from suture anchors is noted within the humeral head. Note the presence of contrast in the subacromial bursa, which may be a normal finding post Page 71 of 73

72 surgery (arrow). Contrast fills the AC joint due to disruption of the inferior capsule (double arrows). This could be a precursor to a 'geyser phenomenon'. Conclusion MR Arthrography of the shoulder is a valuable tool in the assessment of shoulder pathology. We have reviewed a series of shoulder arthrograms and reviewed the indications for an arthrographic study, the injection technique and the technical parameters of the MRI study. The normal anatomy, normal variants that may simulate pathology and the most common pathological entities encountered have been demonstrated. References 1. Oberholzer J. Die Arthropneumoradiographie bei habituleller schulterluxation. Rontgenpraxis 1933 ; 5: Chung CB, Dwek JR, Feng S, Resnick D. MR Arthrography of the Glenohumeral Joint: A Tailored Approach. AJR 2001;177: Jacobson JA, Lin J, Jamadar DA, Hayes CW. Aids to Successful Shoulder Arthrography Performed with a Fluoroscopically Guided Anterior Approach. Radiographics 2003;23: Redondo MV et al. MR Arthrography of the Shoulder Using an Anterior Approach: Optimal Injection Site. AJR 2008;191: Neethling-du Toit M, de Villiers R. Anterior approach v. posterior approach ultrasound guided shoulder arthrogram injection. SAJR October 2008; Zwar RB, Read JW, Noakes JB. Sonographically Guided Glenohumeral Joint Injection. AJR 2004;183: Petersilge CA, Lewin JS, Duerk JL, Hatem SF. MR Arthrography of the Shoulder: Rethinking Traditional Imaging Procedures to Meet the Technical Requirements of MR Imaging Guidance. AJR 1997;169: Farmer KD, Hughes PM. MR Arthrography of the Shoulder: Fluoroscopically Guided Technique Using a Posterior Approach. AJR 2002;178: Dépelteau H, Bureau NJ, Cardinal E, Aubin B, Brassard P. Arthrography of the Shoulder: A Simple Fluoroscopically Guided Approach for Targeting the Rotator Cuff Interval. AJR 2004;182: Stoller DW. Magnetic Resonance Imaging in Orthopaedics and Sports Medicine. 3rd Ed. Philadelphia: Lippincott Williams & Wilkins; Saifuddin A. Musculoskeletal MRI. London: Hodder Arnold; 2008 Page 72 of 73

73 12. de Jesus JO, Parker L, Frangos AJ, Nazarian LV. Accuracy of MRI, MR Arthrography, and Ultrasound in the Diagnosis of Rotator Cuff Tears: A MetaAnalysis. AJR 2009;192: Personal Information Page 73 of 73