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Jargon and the glenoid labrum

A users guide

AMSIG 99 Adelaide

Howard Galloway FRANZCR

Clinical Lecturer

The Canberra Clinical School

University of Sydney

Over the last few years the increased interest in arthroscopic surgery of the shoulder has lead to an explosion in the range of pathology recognised in the shoulder and especially the glenoid labrum and its associated structures. The simultaneous arrival of MR arthrography has tested our ability to recognise the abnormalities described at arthroscopy.

A major barrier to our understanding of advances in arthroscopic surgery of the shoulder has been the increasing use of jargon to describe lesions associated with the labrum. In this presentation I will try to provide a simple users guide to SLAP, SLOP and SLIP in the shoulder.

While conventional MRI is able to identify abnormalities of the shoulder and it's supporting structures with a reasonable degree of accuracy, full characterisation of the capsule, ligaments and labral abnormalities requires distension of the joint. MR arthrography is a simple, robust tool, which maximises the potential of MR for imaging the shoulder.

A low-grade controversy has existed in the literature regarding the optimal positioning of the shoulder, first for CT arthrography and more recently for MR arthrography. Studies comparing internal and external rotation and prone vs supine positioning have consistently shown that a small number of labral lesions may be missed if only one position is used. Tirman, Gennant et al, described ABER (abduction and external rotation) positioning in 1994. By placing the IGHL/antero-inferior labrum complex under tension this position provides a more reliable means of detecting labral pathology as well as providing a further perspective on superior labral impingement.

The normal labrum is comprised mostly of fibrous tissue rather than cartilage; hence its low signal intensity characteristics on MR. Over the age of 30 there is increasing fibrillation of the labral articular surface and intercellular matrix similar to changes in the meniscus of the knee. Antero-inferiorly the anatomy is fairly consistent. The labrum consists of a rounded fibrous elevation of the bony glenoid rim. Studies have shown a constant fibrocartilagenous transition zone between the hyaline cartilage of the glenoid articular surface and the fibrous tissue of the labrum. This may be seen on MRI as an intermediate signal intensity transition zone beneath the low signal intensity labrum.

Grossly and histologically the anterior band of the IGHL is intimately attached to the glenoid rim and labrum at the 4 o'clock position. The more medial the capsular insertion on the humeral neck the more well developed the anterior band appears.

Superiorly the labrum commonly has a meniscal pattern from the 10 o'clock position. Supero-anteriorly to this site the labrum has a loose attachment to the glenoid and there is a close association between the labrum and the long head of biceps tendon both grossly and histologically. At the 12 o'clock position the labrum inserts into the biceps tendon just distal to the tendon insertion into the supraglenoid tubecle. At this point hyaline cartilage extends over the edge of the glenoid rim and a synovial recess is commonly found. The antero-superior part of the labrum has a meniscal pattern and is roughly triangular with a free edge pointing into the joint. The antero-superior part of the labrum is inserted into the fibres of the MGHL.

The Buford complex consists of an absent antero-superior part of the labrum in combination with a cord-like middle glenohumeral ligament. This occurs in approximately 1.5% of patients and can be confused with a labral tear. However the absent labrum occurs in the superior-anterior quadrant which is an uncommon site of labral tear.

The sublabral foramen and sublabral hole are synonymous and refer to an anatomic variation in which the antero-superior portion of the labrum is not attached to the bony margin of the glenoid fossa. The sublabral foramen lies anterior to the biceps-labral complex.

The sublabral recess and the sublabral sulcus are also synonymous and refer to a recess between the biceps labral complex (BLC) and the superior portion of the glenoid fossa. The biceps tendon attaches to the supraglenoid tubercle some 5mm medial to the glenoid rim and 4 types of normal glenoid labral junction have been described. Smith et al found sublabral recesses in 73% of a series of cadaver shoulders and in 40% it was deeper than 2mm. Histologically this recess is smooth and lined with synovium. This can be recognised as normal if it is anterior to the biceps tendon. Congenital recesses are smooth and degenerative recesses are rough.

A type 1 BLC is firmly attached to the superior pole of the glenoid and there is no sublabral foramen

A type 2 BLC is attached to the supraglenoid tubercle. Hyaline cartilage extends over the top of the bony glenoid. A small sulcus may be continuous with a sublabral foramen and communicate with the subscapular bursa.

Types 3 and 4 have larger sublabral recesses (up to l0mm).

Kwak and Resnick (Radiol 1998) have shown that the biceps-labral complex is best imaged with

the humerus in external rotation.

Snyder described these in 1990 in 27/700 (4%) shoulder arthroscopies. They described a specific pattern of injury beginning posteriorly and extending anteriorly, stopping at or before the mid glenoid notch and including the anchor of the biceps tendon. The lesion was labelled SLAP (superior labrum anterior and posterior).

The most common clinical complaints are pain, greater with overhead activity and a painful catching or popping. The most common mechanism of injury was a compression force to the shoulder, often a fall on the outstretched arm with the shoulder in abduction and forward flexion. A less common mechanism is traction on the long head of biceps tendon. Snyder initially described 4 types.

Type I represents fraying of the superior labrum and in the older patient its significance may be uncertain.

Type II is the most common and its hallmark is detachment of the biceps-labral complex from the glenoid rim, extending posterior to the biceps anchor.

Type 1 and 2 are treated with debridement.

Type III is a bucket handle tear of the superior glenoid labrum and the fragment points into the centre of the glenoid fossa. The bucket handle fragment may be seen on the axial images as the "Cheerio" sign of Monu et al (AJR Dec 1994).

Type IV is a detachment of the superior glenoid with a bucket handle into the joint and extension of the tear into the long head of biceps tendon.

The type II SLAP tear may be differentiated from a sublabral recess by the "Oreo cookie " sign described by Smith et al (Radiol Oct 1996). In local practice this would be more correctly described as the Delta Cream sign.

As you can see a SLAP tear and a sublabral recess may coexist with a single Delta Cream sign If the fluid is seen solely anterior to the biceps tendon it is a sublabral recess. If it is also seen posterior to the biceps tendon it is a type II SLAP tear.

When a double Delta Cream sign is present the additional fluid represents a type III SLAP tear with extension of the tear into the substance of the labrum (c.f. a tear of the meniscus of the knee).

Stoller's Atlas also describes~

A type V tear which is a superior extension of a Bankart lesion to the superior labrum with separation of the biceps tendon.

A type VI tear has an unstable flap tear of the superior labrum with biceps tendon separation.

A type VII tear is an an extension of a type II lesion to include the MGHL.

What of the unstable shoulder? In a series of 30 consecutive patients with acute traumatic anterior dislocations (Taylor and Aciero Am J Sports Med May 1997) all patients had a Hill- Sachs lesion at acute MR or arthroscopy. These had not changed at six-month follow up regardless of whether or not there were recurrent dislocations.

There was gleno-humeral ligament injury in 66% and labral injury in 70%. There was capsulolabral detachment in 53% including all recurrent dislocators.

In an effort to clarify the imaging correlates of instability Palmer and Caslowitz (Radiol Dec 1995) published a series of 121 surgical shoulders. Of these 37 were unstable and of these 31 had discrete inferior labro-ligamentous injury. 6 had only capsular laxity.

In this group labro-ligamentous lesions predicted instability with 76% sensitivity and 98% specificity. Inferior labro-ligamentous lesions were strongly associated with unstable shoulders p«.0001. Lesions elsewhere were related to stable shoulders. Capsular insertion types showed no significance between stable and unstable shoulders.

Two major classifications of clinically unstable shoulders are the TUBS "torn loose" (traumatic unstable Bankart surgery) with discrete capsulo-labral abnormalities or the AMBRI "born loose"( atraumatic multidirectional ) which may not have specific imaging abnormalities.

The normal antero-inferior labrum is a rounded fibrous elevation of the glenoid rim and the anterior band of the IGHL is intimately attached to the glenoid rim and labrum at the 4 o'clock position.

The Bankart lesion was described (inconsistently) 1923 and 1939 and is the classic injury to the labrum with detachment of the antero-inferior capsulolabral complex and rupture of the scapular periosteum

The bony Bankart lesion is an avulsion fracture of the glenoid rim that carries with it the capsulolabral complex.

Perthes, prior to Bankart in 1906 described a lesion with incomplete avulsion of the labrum and capsular stripping from the scapular neck. Because of the intact periosteum these lesions may be occult at both imaging and surgery. Adding an ABER sequence to the imaging protocol significantly increases the sensitivity of MR arthrography in detecting these lesions by placing the IGHL complex under tension.

The ALPSA lesion (anterior ligamentous periosteal sleeve avulsion) was described by Nevaiser in 1993 as an avulsion of the antero-inferior labrum with an intact periosteum. The labro-ligamentous complex rolls up in a sleeve -like fashion and becomes displaced medially and inferiorly, "the medialised Bankart lesion". The labrum and capsule will heal in a non-anatomic position resulting in chronic instability. The lesion may resynovialise and is difficult to identify arthroscopically. Preoperative recognition is important, as the surgical approach to these lesions is different to a Bankart lesion repair

The HAGL lesion is a labral avulsion of the capsule including the IGHL from the neck of the humerus. In Des Bokor's series from Parramatta this lesion was seen in 7.5% of 547 unstable shoulders. The lesion is usually the result of violent trauma and in Bokor's series patients with a first dislocation due to violent injury and no evidence of a Bankart lesion or multidirectional instability the incidence was 39%.

A BHAGL (bony HAGL) has been described where there is bony avulsion from the neck of the humerus. The lesion has also been described in association with a Bankart lesion leading to a "floating" IGHL.

GLOM (glenoid labrum ovoid mass) is a small low signal intensity mass occasionally seen anterosuperiorly in the setting of labral injury on the axial images. It is felt to represent a torn and retracted labrum or MGHL.

GLAD lesion (glenolabral articular disruption). Nevaiser described this in 1993. The lesion is a superficial tear of the antero-inferior labrum with an adjacent articular cartilage injury. The extent of the injury may vary from a cartilaginous flap tear to a depressed osteochondral injury of the articular cartilage and underlying bone. The usual mechanism of injury is glenohumeral impaction with the arm in abduction and external rotation. The patients present with persistent pain but the shoulder is stable to routine examination.

OCD of the glenoid. Previously thought to be uncommon this was recently reviewed by Yu et al. There are subchondral cystic lesions similar to OCD in the ankle and there may be intraarticular loose bodies. In Yu's series 6/8 patients had a history of acute trauma and 5/8 had a history of anterior dislocation or subluxation.

GARD lesion. Attributed to Snyder the Glenoid Rim Articular Divot lesion is not associated with instability. Three types have been described, type I a lesion of the peripheral rim of the glenoid articular cartilage, type II also has a wafer of subchondral bone and type III has a large deep "divot" of bone.

Mc Laughlin sign or reverse Hill Sach's lesion is a compression fracture of the anterior aspect of the humeral head associated with posterior dislocation. The trough sign.

Bennet lesion is an extra-articular posterior ossification associated with posterior labral injury. It is thought to be due to posterior capsular avulsion secondary to traction from the posterior band of the IGHL. Posterior capsule and labral injuries have been reported in 36% and 86% of shoulders with posterior instability respectively. There is also a high incidence of anterior labral abnormalities in shoulders with posterior instability.

SLIP (supraspinatus labral instability pattern)

Rotator cuff failure ( functional, pathoanatomic, or both) may result in glenohumeral instability. In the throwing athlete in the late cocking phase there is impingement of the under surface of the cuff on the postero-superior labrum. These patients show abnormalities of the cuff (usually partial tears),the postero-superior labrum, and humeral head at the point of impaction with the posterosuperior glenoid. This is generally associated with posterior shoulder pain and instability. The posterosuperior impingement syndrome.

A basic understanding of the recently described lesions of the glenoid labrum is required to make sense of the increasingly complex diagnostic problems we are asked to solve with MR arthrography. Hopefully now you will always check for SLIP, SLAP and SLOP before reporting on the unstable shoulder.

HilI-Sachs Lesion Fracture of the posterolateral surface of the humeral head indicative of previous anterior glenohumeral joint dislocation.

Trough Lesion Fracture of the medial surface of the humeral head indicative of previous posterior glenohumeral joint dislocation.

Bankart Lesion Injury of the anteroinferior portion of the glenoid labrum indicative of previous anterior glenohumeral joint dislocation.

Sublabral Foramen Normal variation in which a foramen is identified between the anterosuperior portion of the glenoid labrum and the articular cartilage of the glenoid cavity.

Buford Complex Normal variation in which a cord-like middle glenohumeral ligament is associated with absence of the anterosuperior portion of the glenoid labrum.

GLOM Sign Designation for a glenoid labral ovoid mass indicative of an injury with avulsion of a portion of the anterior aspect of the glenoid labrum.

ALPSA Lesion Designation for an anterior labroligamentous periosteal sleeve avulsion, which is associated with recurrent anterior glenohumeral joint dislocations owing to incompetence of the anterior portion of the inferior glenohumeral ligament complex

Perthes Lesion Designation for an avulsion of the anteroinferior portion of the glenoid labrum without displacement and with stripping of the periosteal membrane.

HAGL Lesion Designation for humeral avulsion of the glenohumeral ligament, which is seen usually in older patients and is associated with recurrent anterior glenohumeral joint instability and a tear of the subscapularis

tendon

GLAD Lesion Designation for glenolabral articular disruption, which is associated with a tear of the anteroinferior portion of the labrum and erosion of the articular cartilage of the glenoid fossa and which is not associated with anterior glenohumeral joint instability

SLAP Lesion Designation for superior labral, anterior and posterior tear, often seen in athletes involved in sports requiring repetitive overhead use of the arm and varying in severity but involving the superior portion of the glenoid labrum and, sometimes, the biceps anchor

Bennett Lesion Enthesophyte that arises from the posteroinferior portion of the glenoid rim, often seen in baseball pitchers and probably arising at the site of insertion of the posterior band of the inferior glenohumeral ligament complex

Osteochondritis Dissecans A lesion of the glenoid cavity related to an impaction force.

GARD Lesion A lesion involving the glenoid rim and/or the glenoid cavity, related to an impaction injury.

Perilabral Ganglion Cyst Ganglion cyst arising adjacent to the glenoid labrum and often associated with a labral tear