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ORIGIN OF THE LONG HEAD OF TRICEPS
Abduelmenem Alashkhama,b, Abdulrahman Alraddadia,c, Roger Soamesa
a
Centre for Human Anatomy and Identification, University of Dundee, Dundee, UK
b
Human Anatomy Department, Faculty of Medicine, University of Zawia, Zawia, Libya
c
Human Anatomy Department, Faculty of Medicine, King Saud Bin Abdulaziz
University for Health Sciences , Riyadh, Saudi Arabia.
ABSTRACT
Anatomical anomalies of triceps are not
common. During the course of a cadaveric
dissection in CAHID a rare bilateral variation
of the attachment of the long head of triceps
was found in a 62 year old female cadaver.
The long head of triceps was attached to the
infraglenoid tubercle and the posteroinferior
aspect of the glenohumeral joint capsule, as
well as by a fibrous extension between 3 to 4
cm long to the superior part of the lateral
border of the scapula.
INTRODUCTION
Triceps is a large, strong fusiform muscle in
the posterior compartment of the arm (Smith
et al., 1983; Palastanga et al., 2006). It has
three heads, the long head arising from the
scapula and the medial and lateral heads from
the posterior aspect of the humerus (Rogers,
1992; Lumley et al., 1995).
The medial head is the deepest taking origin
from the lower half of the posterior aspect of
the humerus and the intermuscular septa
inferior and medial to the spiral groove
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(Abrahams et al., 2011; Sinnatamby, 2006).
The lateral head is superficial and lateral;
having a linear attachment from the superior
lip of the spiral groove and the posterior
surface of the upper 1/3rd of the humerus
between the attachment of deltoid and teres
minor as far superior as the surgical neck of
the humerus: it descends bridging over the
spiral groove forming its roof (Snell, 1995;
Moore et al., 2010). The long head is
superficial and medial, coming from the
infraglenoid tubercle and glenoid labrum. It
passes downwards interposed between teres
minor (posterior) and teres major (anterior),
running superficial to the medial head of
triceps. It forms the medial border of both the
quadrilateral and lower triangular spaces. The
long and lateral heads descend to join the
medial head, with the lateral head covering
the radial nerve and profunda brachii vessels
in the spiral groove (Monkhouse, 2001; Drake
et al., 2005).
Fusion of the three heads above the elbow
gives rise to a broad laminated tendon which
is inserts into the summit of the olecranon
process of the ulna. The tendon is separated
by a bursa from the posterior region of the
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elbow joint (Faiz and Moffat, 2006; Palastanga
et al, 2006). The three heads of triceps are
supplied separately by branches from the
radial nerve (Hall-Craggs, 1990; Ellis, 2006).
Triceps extends the forearm at the elbow
joint. In addition, as the long head crosses the
shoulder joint it helps in adduction and
extension of the arm, supports the head of
the humerus when the upper limb is abducted
counteracting inferior translation of the
humeral head (Sinnatamby, 2006; Palastanga
et al., 2006; Moore et al., 2010).
Triceps anomalies have seldom been reported
in the literature. In an assessment of twenty
fresh cadaveric shoulders (10 males, 10
females, mean age 65.8 years) Handling et al
(2010) reported that the long head of triceps
originates from the infraglenoid tubercle,
posterior aspect of the upper part of the
lateral border of the scapula with a persistent
attachment to the inferior aspect of the
capsule of the shoulder joint: the mean width
and thickness of the lateral and medial
aspects of the tendon of the long head of
triceps were 26.9 mm, 4.7 mm and 2.9 mm
respectively.
In an evaluation of 15 fresh cadaveric
shoulders Eiserloh et al (2000) reported that
the long head of triceps brachii originated
from the infraglenoid tubercle with a
contribution from the posteroinferior aspect
of the fibrous capsule of the shoulder joint.
The mean width and thickness of the long
head origin were 29.5 mm (range, 26 - 34
mm) and 5.7 mm (range 4 - 7 mm)
respectively. The authors noted that in all
specimens a fibrous extension, with an
average length of 3.7 mm, was consistently
present from the bony attachment of the long
head of triceps to the posteroinferior aspect
of the capsule where it was stretched in
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abduction and external rotation as well as in
flexion and internal rotation. It was
considered that the cardinal functions of the
fibrous extension is to (1) counteract the
inferior translation of the humeral head
during abduction, especially when it exceeds
90 degrees, and (2) tense the capsule
substantially when the arm is rotated.
Tubbs et al (2006) have reported that the
medial head of triceps is attached to the
posterior region of the surgical neck of the
humerus having a length of 6.5 cm and a
width of 0.5 cm. Soubhagya et al (2007) also
reported that the medial head of triceps had a
further bony origin, suggesting that triceps
has four heads with the fourth head attaching
to the medial aspect of the humerus inferior
to the insertion of teres major and latissimus
dorsi. The length and width of the fourth head
were 6 cm and 1.6 cm respectively. Earlier
Fabrizio and Clemente (1997) reported a
unilateral fourth head of triceps arising from
the posteromedial aspect of the humerus just
superior to the insertion of teres major
parallel to the lateral head of triceps. The
tendon passed inferiorly on the medial side of
the humerus deep to the medial head in the
lower third of the arm, as well as having a
direct relation to the profunda brachii artery
and radial nerve as they pass to the radial
groove: it attached to the medial aspect of the
olecranon process of the ulna.
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CASE REPORT
During dissection of the shoulder of a 62 year
old female, the long head of triceps was
observed to have an extended attachment. In
addition to its origin from the infraglenoid
tubercle there was some contribution from
the posteroinferior aspect of the
glenohumeral capsule, a fibrous slip to the
superior part of the lateral border of the
scapula on both sides (Fig. A, B).
The mean width, medial and lateral thickness
of the extension on the right side were 25
mm, 3.8 mm, 5 mm and on the left 26 mm,
3.3 mm, 5 mm respectively.
The long head passed distally to blend with
the lateral and medial heads before inserting
into the olecranon process of the ulna via a
broad tendon. There was no anatomical
variation in relation to teres minor and major,
the triangular interval, or the quadrangular
and triangular spaces and their contents.
Knowledge of the anatomical variation of the
long head of triceps is important because it
has a contribution to the posteroinferior
aspect of the fibrous capsule of the shoulder
joint, and may be damaged during open or
arthroscopic surgery of the shoulder joint. As
a consequence there could be a decrease in
the posteroinferior support of the fibrous
capsule to the head of humerus which could
potentially lead to dislocation of the shoulder
joint. More studies are therefore needed to
investigate the long head of triceps and its
potential contribution to the biomechanics of
the shoulder joint.
Figures A (right scapula) and B (left scapula)
illustrate the origin of the long head of triceps.
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