Introduction:
Acute shoulder injuries are common in female gymnasts, and uneven bars
is the dominating mechanism of injury1. We present a
case report of a conjoined tendon avulsion of both the latissimus dorsi
(LD) and teres major (TM) muscles in a high-performance, middle-aged,
veteran artistic gymnast. The challenges associated with these types of
injuries are related to the complex anatomy, a potentially low degree of
clinical suspicion because of unfamiliarity with the diagnosis among
clinicians, and the fact that these injuries are not well visualized at
standard shoulder imaging.
The LD and TM muscles act as one muscle unit in a wide variety of
movements. The large LD muscle originates from the iliac crest´s
posterior third, the sacrum, all lumbar vertebrae, the spinous processes
of vertebrae T7-T12, and sometimes from the 9th to the
12th rib and the inferior angle of the scapula. It is
oriented in a craniocaudal direction, dorso-laterally along the torso.
The TM muscle originates from the scapular inferior angle. It follows
the LD laterally and both muscles merge together to form a conjoined
tendon and insert into the bicipital groove at the proximal humerus
(Fig. 1a-c). The LD/TM muscle unit adducts, extends, and rotate the
humerus internally when the shoulder is abducted. An intact LD muscle is
mandatory for shoulder stability and plays a crucial role in stabilizing
the lower back and the sacroiliac joint together with the contralateral
gluteus maximus muscle during bodily motions like walking and
running2,3. Together with the pectoralis major, the LD
and TM are the main adductors of the shoulder4. A
sudden contraction, against resistance, from a hyper-abducted position
of the shoulder with the arm externally rotated and/or hyperextended can
cause injury to the LD/TM muscle bellies, avulsion from their origins,
or avulsion of the conjoined tendon insertion from the proximal humerus.
Due to the rarity of injury to the LD and/or the TM, the literature
mainly consists of case reports and case series of high-level
athletes5. Latissimus dorsi tendon tears have been
reported in baseball, cricket, weightlifting, soccer, water-skiing,
wrestling, steer wrestling (rodeo event), cross-fit, and
tennis5-14. Isolated teres major tendon tears have
been reported in baseball6,7. Furthermore, reports of
a combined tear to both the LD and the TM tendons are, to the best of
our knowledge, restricted to baseball, golf, and
water-skiing6,7,15,16. The incidence of LD tear seems
to be increasing and the injury is predominantly found in baseball
pitchers1. Because baseball is a sport with variable
popularity around the world, injury to the LD/TM may be unfamiliar for
physicians and physiotherapists in health care systems outside the
Americas and South Asia. Consequently, the diagnosis may be overlooked,
even in high quality health care countries. A clear classification
system will be helpful when orthopaedic surgeons with limited knowledge
of these injuries are consulted for treatment
recommendations17.