Clinical History: A 14 year old water polo player presents with chronic anterior shoulder pain. Axial proton density (1a) and oblique sagittal (1b) T1-weighted images are submitted for review. What are the findings? What is your diagnosis?
Isolated avulsion fracture of the lesser tuberosity.
Isolated fractures of the lesser tuberosity of the humerus are uncommon, with only a few pediatric cases reported.1-9 It is thought that in such cases the recently fused lesser tuberosity of the adolescent is the point of weakness, rather than the subscapularis tendon insertion.10 The injury most commonly occurs with forced external rotation during abduction, and can be seen in contact sports such as football or wrestling. However, it may also present, as in this case, as a chronic overuse injury in throwing athletes. In these patients, the stress upon the lesser tuberosity from contraction of the subscapularis tendon is maximal as the thrower transitions from the fully abducted cocking phase to the internal rotation of the acceleration phase.11
Affected patients most often present with a history of chronic shoulder pain. Physical exam may reveal tenderness over the anterior aspect of the shoulder, weakness in internal rotation, increased passive external rotation, or a positive lift-off test.
Delayed union of the lesser tuberosity fracture is common at presentaton, and the fracture is often not visible on AP x-rays. It can be visulized on axillary x-rays, but is best seen on MRI, which also assesses the integrity of the subscapularis tendon.
Images below are from an MRI on another patient who presented three months after being tackled while throwing a football.
Because the majority of cases of lesser tuberosity avulsion present with malunion or delayed union, continued pain and weakness with internal rotation frequently results. A trial of conservative treatment may be undertaken, but displaced fracture fragments and surrounding fibrosis may have to be excised to restore full strength and pain free throwing ability in the adolescent athlete.
Avulsion fractures of the lesser tuberosity are unusual injuries that should be suspected in an adolescent athlete who presents with chronic pain and focal anterior tenderness. The fracture is often not visible on AP x-rays. MRI not only reveals the size and location of the avulsed lesser tuberosity fragment, but can also provide important assessment of the integrity of the subscapularis tendon.
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11 Werner SL, Gill TJ, Murray TA, et al: Relationships between throwing mechanics and shoulder distraction in professional baseball pitchers. Am J Sports Med 29: 354-358, 2001