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Journal of the Anatomical Society of India

Anatomical Variations in the Labral Attachment of the Long Head of Biceps Brachii

Author(s): Paul S., Sehgal R and *Khatri K

Vol. 53, No. 2 (2004-07 - 2004-12)

Maulana Azad Medical College & *University College of Medical Sciences, New Delhi.

Abstract:

The proximal attachment of the long head of biceps brachii was studied in 61 formalin preserved joints to see the extent of its attachment to the labrum glenoidale. In all specimens, the biceps tendon was found to be attached to the supraglenoid tubercle as well as to the labrum glenoidale. In 67% of specimens, the major part of the tendon was attached to the posterior part of the labrum while in 33%, it was seen in the anterior part as well. Further study of the labrum showed that the posterior labral attachment extended up to the lower part where as the anterior attachment was limited to the upper & middle part only. The awareness of the posterior attachment till the lowest part of labrum glenoidale might help the clinicians in planning their surgical procedures. It might be of immense clinical interest in sports medicine.

Key words: labrum glenoidale, biceps brachii, labral attachment.

Introduction:

The tendon of the long head of Biceps brachii musclehas been described in most anatomical texts as takingorigin from the supraglenoid tubercle Hollinshead (1958), Woodburne (1961), Hamilton (1978), Snell (1981), Habermeyer (1987), Prodromas et al (1990), Rockwood & Matsen (1990). Other studies have however shownits additional attachment to labrum glenoidale Gardneret al (1975) Williams & Warwick (1980) Romanes (1981) Last (1984) Pal et al (1991) Cooper et al (1992). Thepurpose of the present study was to define the extent ofthe labral attachment of the tendon of biceps brachii.

Material and Method:

The specimens for the present study consisted of 61 shoulder joints of adult humans of both sexes. Thejoint cavity was exposed by making an incision in theanterior part of the capsule of the joint. The long head ofbiceps was dissected and its attachment studied. Theglenoid cavity was divided into upper, middle & lowerparts to see the extent of the attachment of the tendonto the labrum glenoidale as illustrated below.

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Observations & Results:

The biceps tendon was seen to arise from thesupraglenoid tubercle which extended onto the labrumglenoidale (both anteriorly & posteriorly) in all thespecimens, although the extent of this labral attachmentvaried (Fig.1). An anterior labral attachment was observed

in 33% specimens while a posterior labral attachmentwas seen in 100% of the shoulder joints studied. Isolatedposterior labral attachment was seen in 67% specimens(Fig.2). None of the specimens showed isolated anteriorlabral attachment. The anterior and posterior labralmargins were examined to see how far the attachmentextended i.e., upper, middle or lower third. The resultsare summarized in Table-I. To the best of our knowledgethe extension of attachment up to lower third of posteriorglenoidal labrum has not been reported earlier. In 30% of specimens, the labrum glenoidale was complete andfirmly adherent to the margin of the glenoid cavity. Manyspecimens showed a gap between the tendon andglenoid cavity where the labrum itself was deficient.

Table-I: Percentage distribution of attachment of biceps brachii to different parts of labrum glenoidale.

Labral attachment Upper third Middle third Lower third
Anterior 27% 6% 0%
Posterior 22% 46% 32%

The present study revealed that the tendon of longhead of biceps brachii has a dual attachment to thesupraglenoid tubercle as well as labrum glenoidale whichconforms with the arthroscopic analyses of Bankart(1980), Detrisac & Johnson (1986), Pal et al (1991) andCooper et al (1992).

Anatomical variations in the labral attachment of the biceps tendon help us to explain the association ofrecurrent shoulder dislocation & labral detachment. This aids interpretation of biomechanical electromyographic(EMG) data showing maximum activity of long tendonof biceps in the late phase of throwing when the shoulderis abducted & externally rotated, Gowan et al (1987) and record of a higher, biceps activity in pitchers withknown anterior instability Glousman et at (1988), whereinthe biceps force has been shown to increase the torsionalrigidity of the glenohumeral joint by 32%, Rodosky et al(1994).

Many specimens showed a deficient glenoid labrumand presence of a gap between the tendon and the glenoid cavity posterosuperiorly, which corroborates thefindings of Pal et al (1991). Observations on dry, macerated scapulae done by the author, Paul et al (1988) revealed the presence of a small crescentric faceton the posterosuperior margin of the glenoid cavity in70% cases which corresponds well with the percentageshowing a deficient labrum.

Fig. 1 b

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Tendon of biceps brachii with its anterior and posterior extension.

Fig. 2:

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Arrow shows isolated posterior extension of biceps brachii.

Fig. 3:

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Arrow shows posterior extension of the tendon up to lower 1/3rd.

Fig. 4

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Arrow shows anterior extension of the tendon up to upper 1/3rd.

The biceps tendon courses over the head of thehumerus to continue with the labrum, thus helping toretain the head in the glenoid fossa and assisting the "rotator cuff". Our study has demonstrated that in 32% of specimens the posterior labral attachment of thetendon extended up to the lower third of the glenoidcavity (Fig.3), a finding which has not been reportedearlier. This extensive attachment in the posteriorglenoidal labrum is expected to provide a better stabilityto the shoulder .

Boyd & Sisk (1972) have made surgical use of thislabral attachment in patients with detached posteriorlabrum by combining an operative posteriorcapsulorraphy with a transfer of tendon of long headaround the neck of the humerus and across the posteriorcapsule to be re-attached to the posterior scapular neck. The tendon may be elongated by as much as 1 cm. toachieve this procedure due to the presence of its labralattachment.

The present study has successfully accomplishedits purpose of demonstrating the variability of the labralattachment and has shown that this attachment has a strong posterior orientation, which is comparable withthe findings of Vangsness et al ( 1994 ). In all specimens, the tendon extended posteriorly, mostly up to the middlethird of the posterior glenoidal margin.

In 33% it was attached to the anterior part as well but limited in most cases to the upper third only (Fig.4). None of the specimens showed isolated anteriorattachment. An understanding of the labral attachmentof the long tendon of biceps brachii plays an importantrole in evaluation and surgical correction of labralpathology.

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