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Anterosuperior Labrum

This portion of labrum is situated between the biceps anchor and the glenoid notch [6] and, similar to the superior labrum, has a meniscal like appearance. [20]

Cooper et al [20] reported the antero-superior labrum to mainly insert “…into the fibers of the middle or inferior glenohumeral ligament, rather than to the actual glenoid margin…” Snyder [6] reported firm attachment of the labrum to the glenoid margin in approximately 80% of cases, whereas Cooper et al [20] described it occurring in 18% of specimens. 

Antero-superior labral variations commonly occur, with a prevalence of between 13.4% and 25%. [24-26]

The sublabral foramen is an antero-superior glenoid labrum variant characterised by detachment of the labrum from the underlying glenoid [Figure 6]. [24] It may vary in size from being a few millimetres to encompass the whole antero-superior quadrant. [6] It is associated with a normal or a cord-like middle glenohumeral ligament. [24-26] It has a prevalence of between 0% and 40% and should not be confused with pathology such as a Bankart type labral detachment or SLAP lesions (Superior labral anterior-posterior tears). [6,20,24-29]

 
Figure 6 – Arthroscopic image of a small sublabral foramen on left and large on right(arrows). This is an antero-superior labrum variant characterised by detachment of the labrum from the underlying glenoid. [24] It may vary in size from being a few millimetres to encompass the whole antero-superior quadrant. [6]

The sublabral foramen is an age related phenomenon, increasing in prevalence with age. [30-31] Taking this into account, the age of patients chosen for a study would influence its incidence [Table 7]. Park et al [28] reviewed MR Arthrograms of patients between the ages of 19 and 24 years old and reported the incidence of a sublabral foramen to be 7%. In contrast, Yeh et al [27] performed a MR Arthrographic study on cadaveric shoulders between the ages of 61 and 96 years old and reported the incidence of sublabral foramen to be 40%. It is clearly possible to see that the age of patients chosen for a study alters the prevalence of a sublabral foramen.  

 The “Buford complex” is another antero-superior glenoid labrum variant. It is characterised by an absent antero-superior labrum and a cord-like middle gleno-humeral ligament that originates at the superior labrum, at the base of the biceps tendon and crosses the subscapularis tendon at 45º to insert on the humerus [Figure 7]. [6,25] Snyder [6] commented on the appearance of the labrum and the cord-like middle glenohumeral ligament in such variants, reporting no labrum fraying to be present and the edges of the ligament to be smooth. The “Buford complex” has a prevalence of between 1.2% and 6.5%, and should not be confused with pathological SLAP lesions [Table 8]. [6,24-26,28-29]

Buford Variant
Figure 7
– Arthroscopic image of the “Buford complex”. This is a variant of the antero-superior labrum characterised by absent antero-superior labrum and a cord-like middle gleno humeral ligament that originates from the superior labrum, at the base of the long head of biceps [6]

An arthroscopic study reported a positive association between finding antero-superior labral variants and “…anterosuperior labral fraying, an abnormal superior gleno-humeral ligament, and increased passive internal rotation with the arm in 90° of abduction”. [24] A negative association was reported between these variants and a painful arc sign and a supraspinatus tear, both partial and full-thickness. [24]

From our study:
Similar to other studies [20-21,34], variations in the antero-superior labrum were found collectively in 20.5% of cases [Table 19].
The prevalence of the sublabral foramen was found to be 14.4%, which is within the 0%-40% range mentioned in the literature [Table 20]. [6,17,20-22,34-36] The size of the sublabral hole was variable, the medium size being most commonly encountered. The shape and appearance of the sublabral foramen varied between examples, and was at times difficult to classify. Similar to the literature, [20-21,34] we found the sublabral foramen to be more commonly associated with a cord-like middle gleno-humeral ligament rather than with a normal one [Table 21].
The 6.1% prevalence of the Buford complex in the present study is similar to that already mentioned in the literature [Table 22]. [6,20-22,34-35] Like Rao et al [20], we found the Buford complex to be more commonly associated with an abnormal superior gleno-humeral ligament.    
 

Table 19 – Prevalence of Antero-superior labral variations

% Prevalence of Antero-superior labral variations

13.4% - Arthroscopic study [20]

 

13.5% - Arthroscopic study [21]

 

20.5% - Arthroscopic study

 

25% - Arthroscopic study [34]

 

 

Table 20 – Prevalence of a Sublabral foramen – an antero-superior glenoid labrum variant characterised by detachment of the labrum from the underlying glenoid. [20]

 

% Prevalence

Type of study

 

 

0%

Cadaveric study [35]

7%

MR Arthrographic study [22]

12%

Arthroscopic study [20]

12%

Arthroscopic study [21]

14%

Arthroscopic study [6]

14.4%

Arthroscopic study

18.5%

Arthroscopic study [34]

27%

Cadaveric study [36]

36%

Cadaveric study [17]

40%

MR Arthrographic study [36]

 

 Table 21 – Prevalence of a normal and a cord-like middle gleno-humeral ligament in patients with a sublabral foramen, an antero-superior glenoid labrum variant.

 

% Prevalence of a normal middle gleno-humeral ligament in patients with a sublabral foramen

% Prevalence of a cord-like   middle gleno-humeral ligament in patients with a sublabral foramen

26.3% - Arthroscopic study

72% - Arthroscopic study [20]

 

28% - Arthroscopic study [20]

73.7% - Arthroscopic study

35% - Arthroscopic study [34]

 

75% - Arthroscopic study [21]

 

 

 

65% - Arthroscopic study [34]

 

 

Table 22 – Prevalence of the Buford complex – an antero-superior labrum variant

% Prevalence of the Buford complex

1%    - Arthroscopic study [20]

1.2% - Cadaveric study [35]

1.5% - Arthroscopic study [21]

2%    - MR Arthrography [22]

6%    - Arthroscopic study [6]

6.1% - Arthroscopic study

6.5% - Arthroscopic study [34]

 

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