Discussion:
Injury to the latissimus dorsi muscle is rare in non-baseball-athletes
and most often occurs after an acute traumatic event, typically as an
avulsion of the tendon rather than injury to the myotendinous
junction18.
Standard imaging studies of the shoulder may not visualize injuries to
the latissimus dorsi, as its attachment could be in the periphery of the
chosen field of view. The referral should clearly state clinical
suspicion of latissimus dorsi injury to ensure that the correct area is
covered. In our case, there were both clinical suspicion and an alert
radiographer who added extra slices to the axial series to cover an area
of suspected soft-tissue edema. The oblique course of the latissimus
dorsi along the thoracic cage makes it often difficult, even with
adequate MRI imaging, to visualize a traumatized muscle and
tendon19.
In the subsequent follow-up imaging examinations, we attempted to cover
more of the muscle belly, but at the price of somewhat reduced image
quality.
In the literature, treatment recommendations for LD/TM injuries are
predominantly based on younger male baseball pitchers treated
non-operatively or surgically.
Erickson and co-workers reported a return to sport rate of 75% amongst
120 baseball pitchers from 2006 to 2011 with a latissimus dorsi / teres
major regardless of treatment (non-operative or surgical
treatment)20. Interestingly, they found a shorter
recovery time to the same competition level in the non-operatively
treated pitchers compared to those who underwent surgery, which can be
explained by a more extensive injury in those receiving surgical
treatment. A grading system based on MRI is proposed by Erickson et
al.17:
Grade I: Fluid tracking along latissimus dorsi / teres major
Grade II: Partial-thickness tear
Grade III: Full-thickness tear, < 2 cm of retraction
A: Muscle is torn off the humerus.
B: Tear is at the musculotendinous junction.
Grade IV: Full-thickness tear, > 2 cm of retraction
A: Muscle is torn off the humerus.
B: Tear is at the musculotendinous junction
Non-operative management of grade I and II injuries and surgical repair
in avulsion injuries in grade III and IV tears were recommended. In the
present case report, the injury was an avulsion of both latissimus dorsi
and the teres major, and the retraction of the LD tendon was
> 2 cm. According to the suggested treatment algorithm by
Erickson et al., our patient´s injury may be classified as grade IV-A
which implies recommendation for surgical intervention. However, the
patient’s choice of non-operative management with self-administered
early accelerated functional rehabilitation guided by the gradual reveal
of symptoms and limitations led to a full functional recovery with only
a negligible cosmetic sequel. The MRI findings of reduced thickness of
the muscle fibers on the right side compared to the uninjured left side
38 weeks post-injury suggest that the potential injury-related reduction
in strength of the teres major and latissimus dorsi muscles has been
compensated by biomechanical adjustments of motion pattern and/or
increased contribution from accessory muscles around the shoulder.
The classification system by Erickson et al. does not distinguish
between isolated tears to either the LD or the TM, and the conjoined
tendon as a whole. The current case demonstrates the need for a
clarification of the MRI classification system. A full thickness tear of
the LD with a retraction of more than 2 cm may be classified as a severe
(grade IV) injury which should be treated surgically according to
recommended guidelines17. The successful non-operative
treatment of the patient in the current case may be explained by the
fact that a small string of the TM tendon remained in contact with its
bony attachment on the humerus despite the tear of the rest of the TM
and the whole LD with large retractions of more than 2 cm. We propose
that tears to the LD and TM tendons are graded as one conjoined tendon
tear and that a complete rupture of both the LD and the TM must be
present to classify the injury as a grade III or IV according to
Erickson et al. As exemplified by the injury in our female middle-aged
gymnast, this additional specification would have led to non-operative
treatment recommendations similar to the grade II injuries.