Glenoidal labrum
Encyclopedia
The glenoid labrum is a fibrocartilaginous rim attached around the margin of the glenoid cavity
in the shoulder blade. The shoulder joint is considered a 'ball and socket' joint. However, in bony terms the 'socket' (the glenoid fossa of the scapula) is quite shallow and small, covering at most only a third of the 'ball' (the head of the humerus). The socket is deepened by the glenoidal labrum.
The labrum is triangular in section, the base is fixed to the circumference of the cavity, while the free edge is thin and sharp.
It is continuous above with the tendon of the long head of the Biceps brachii, which gives off two fasciculi to blend with the fibrous tissue of the labrum.
It deepens the articular cavity, and protects the edges of the bone.
In order to examine acute (no longer than 14 days after the luxation) shoulder injuries, the conventional MRI is the modality of choice. The joint effusion, caused by the trauma, shows the fluid dispersal and leads therefore to a highly differentiated image. Proper conventional sequences are T1w-intermedial, w-TSE-axial, -paracoronal, --parasagittal.
For chronic shoulder problems the MR-arthrography has significant advantages and should be recommended to illustrate labrum and ligaments. The precise measurement of the extent of the degenerative and scarred transformation leads to the accurate next therapeutic steps. Whether the patient should be treated arthroscopically or through an open surgery. Between 12 and 20 ml of contrast agent should be injected ventrally. A solution of 1:200 diluted 0.5 molar gadepentate-dimeglumine. Proper sequences are T1w-axial, –parasagittal and spectrally fat-saturated -paracoronal. Supplementary a fat suppressed paracoronal intermedial w-TSE sequence.
MR-Arthrographic findings for:
Bankart lesion : Contrast agent leaks between labrum and glenoid.
Perthes lesion : The towards medial stripped but still intact periosteum shows as a signal weak line.
ALPSA (anterior labro-ligamentous sleeve avulsion) lesion : Dislocation of the labro-ligamentous complex towards the medial glenoid. Characteristically is there no contrast agent detectable between labrum and bone.
GLAD lesion : Inflow of contrast agent and consequently demarcation of the lesion.
SLAP (superior labral anterior to posterior) lesion : Snyder et al. described 4 subtypes which have been extended up to 9 subtypes. Given that increasingly further pathologies accompany the classifications, it is recommended to use the original four Snyder classifications. Further findings should be valuated as additional pathologies.
Type 1: Fraying of the superior labrum. Imaging can be omitted if there are hardly any clinical symptoms. The biceps tendon anchor complex is stable. It’s a usual degenerative sign of old age. No therapy required, at the most a debridement.
Type 2: Detachment of the labro-bicipital complex off the glenoid. Contrast agent inflow into the superior labrum and the biceps tendon insertion. Most common SLAP lesion. An important differential diagnose is the sublabral recessus, which is a non-pathological variation from the norm. Criteria for a pathological finding: Contrast agent inflow towards cranial and lateral into the labro-bicipital complex, compared to a medial inflow between labrum and glenoid. Irregular boundary of the contrast agent. Further separation of labrum and glenoid. It‘s an unstable injury and requires an arthroscopic refixation.
Type 3: “bucket handle tear” of the superior labrum. A larger traumatic and triangular tear, the central portion (the bucket handle) can stay in situ or be displaced into the joint cavity. It’s a stable injury which requires debridement.
Type 4: Type 3 including involvement of the biceps tendon. Its an unstable injury and requires an arthroscopic refixation.
Sublabral recessus:
Linear inflow of contrast agent between labrum and glenoid at the paracoronal sequence. Typically straightened medially towards the tuberculum supraglenoidale. The superior labrum often isn’t completely attached to the glenoid. There can be a variously deep sulcus which communicates with the joint cavity.
Sublabral foramen:
Inflow of contrast agent between labrum and glenoid at the axial sequence. A circumscribed lack of attachment of the superior ventral labrum. The range of the foramen is large. From few milimeters up to a complete ablation of the anterosuperior labrum. Helpful and of differential diagnostic value is the exact localisation of the finding. This variation of the norm is at the anterosuperior glenoid. Bankart lesions for example have an anteroinferior localisation.
Buford complex:
Absence of the anterosuperior labrum and a thickened cord-like medial glenohumeral ligament.
Another variation of the norm, equally common as the recessus, is a ventral sulcus between the biceps tendon and the superior labrum. This particular variation can be easily discriminated and is therefore not a serious differential diagnostic pitfall.
Glenoid cavity
The glenoid cavity is a shallow pyriform, articular surface, which is located on the lateral angle of the scapula. It is directed laterally and forward and articulates with the head of the humerus; it is broader below than above and its vertical diameter is the longest.This cavity forms the...
in the shoulder blade. The shoulder joint is considered a 'ball and socket' joint. However, in bony terms the 'socket' (the glenoid fossa of the scapula) is quite shallow and small, covering at most only a third of the 'ball' (the head of the humerus). The socket is deepened by the glenoidal labrum.
The labrum is triangular in section, the base is fixed to the circumference of the cavity, while the free edge is thin and sharp.
It is continuous above with the tendon of the long head of the Biceps brachii, which gives off two fasciculi to blend with the fibrous tissue of the labrum.
It deepens the articular cavity, and protects the edges of the bone.
Imaging
In order to examine acute (no longer than 14 days after the luxation) shoulder injuries, the conventional MRI is the modality of choice. The joint effusion, caused by the trauma, shows the fluid dispersal and leads therefore to a highly differentiated image. Proper conventional sequences are T1w-intermedial, w-TSE-axial, -paracoronal, --parasagittal.
For chronic shoulder problems the MR-arthrography has significant advantages and should be recommended to illustrate labrum and ligaments. The precise measurement of the extent of the degenerative and scarred transformation leads to the accurate next therapeutic steps. Whether the patient should be treated arthroscopically or through an open surgery. Between 12 and 20 ml of contrast agent should be injected ventrally. A solution of 1:200 diluted 0.5 molar gadepentate-dimeglumine. Proper sequences are T1w-axial, –parasagittal and spectrally fat-saturated -paracoronal. Supplementary a fat suppressed paracoronal intermedial w-TSE sequence.
MR-Arthrographic findings for:
Bankart lesion : Contrast agent leaks between labrum and glenoid.
Perthes lesion : The towards medial stripped but still intact periosteum shows as a signal weak line.
ALPSA (anterior labro-ligamentous sleeve avulsion) lesion : Dislocation of the labro-ligamentous complex towards the medial glenoid. Characteristically is there no contrast agent detectable between labrum and bone.
GLAD lesion : Inflow of contrast agent and consequently demarcation of the lesion.
SLAP (superior labral anterior to posterior) lesion : Snyder et al. described 4 subtypes which have been extended up to 9 subtypes. Given that increasingly further pathologies accompany the classifications, it is recommended to use the original four Snyder classifications. Further findings should be valuated as additional pathologies.
SLAP lesion
Proper MRI sequence: paracoronal. Classification on the basis of contrast agent inflow into the superior labrum and the biceps tendon insertion.Type 1: Fraying of the superior labrum. Imaging can be omitted if there are hardly any clinical symptoms. The biceps tendon anchor complex is stable. It’s a usual degenerative sign of old age. No therapy required, at the most a debridement.
Type 2: Detachment of the labro-bicipital complex off the glenoid. Contrast agent inflow into the superior labrum and the biceps tendon insertion. Most common SLAP lesion. An important differential diagnose is the sublabral recessus, which is a non-pathological variation from the norm. Criteria for a pathological finding: Contrast agent inflow towards cranial and lateral into the labro-bicipital complex, compared to a medial inflow between labrum and glenoid. Irregular boundary of the contrast agent. Further separation of labrum and glenoid. It‘s an unstable injury and requires an arthroscopic refixation.
Type 3: “bucket handle tear” of the superior labrum. A larger traumatic and triangular tear, the central portion (the bucket handle) can stay in situ or be displaced into the joint cavity. It’s a stable injury which requires debridement.
Type 4: Type 3 including involvement of the biceps tendon. Its an unstable injury and requires an arthroscopic refixation.
Variations from the norm of the superior labrum-biceps tendon-complex
There are common variations which have to be considered and should not be wrongly interpreted as pathological findings.Sublabral recessus:
Linear inflow of contrast agent between labrum and glenoid at the paracoronal sequence. Typically straightened medially towards the tuberculum supraglenoidale. The superior labrum often isn’t completely attached to the glenoid. There can be a variously deep sulcus which communicates with the joint cavity.
Sublabral foramen:
Inflow of contrast agent between labrum and glenoid at the axial sequence. A circumscribed lack of attachment of the superior ventral labrum. The range of the foramen is large. From few milimeters up to a complete ablation of the anterosuperior labrum. Helpful and of differential diagnostic value is the exact localisation of the finding. This variation of the norm is at the anterosuperior glenoid. Bankart lesions for example have an anteroinferior localisation.
Buford complex:
Absence of the anterosuperior labrum and a thickened cord-like medial glenohumeral ligament.
Another variation of the norm, equally common as the recessus, is a ventral sulcus between the biceps tendon and the superior labrum. This particular variation can be easily discriminated and is therefore not a serious differential diagnostic pitfall.