Review Question - QID 218119

Lesser tuberosity fractures can occur in the setting of posterior shoulder dislocations and are often missed. An isolated lesser tuberosity fracture (Figure A) should prompt a workup for posterior shoulder instability.

The lesser tuberosity is typically protected from direct injury by its small size and its location on the medial side of the head of the humerus, making isolated lesser tuberosity fractures uncommon; however, when the subscapularis muscle forcefully contracts to resist abduction and external rotation of the shoulder, it is forced to extend, and the resultant strong traction force can avulse the lesser tuberosity. Sudden involuntary muscular contractures, such as those that occur with epileptic events or electrocutions, have been shown to cause such fractures and are commonly associated with posterior shoulder dislocations by a similar mechanism. On plain radiographs, these fractures may be misdiagnosed as calcific tendonitis of the rotator cuff or osseous Bankart lesions if an axillary view is not obtained, especially in the case of small avulsion fractures. In these cases, an AP view in maximal internal rotation projects the lesser tuberosity in profile and may be helpful in diagnosis in conjunction with a standard AP showing the lightbulb sign (Illustration B), and an axillary lateral view showing a posteriorly subluxed or dislocated humeral head.

Tosun et al. present two cases of isolated lesser tuberosity fractures initially missed on standard AP radiographs, one associated with a traumatic posterior dislocation and another with an epileptic attack. The authors found that symptoms specific to acute cases include exacerbation of pain on external rotation, restricted internal rotation, and tenderness on the lesser tuberosity, and that open or arthroscopy-assisted reduction and fixation are available treatment modalities that may lead to excellent clinical and radiological results. They concluded that a successful functional outcome following isolated lesser tuberosity fractures requires a proper indication, good surgical technique, appropriate postoperative therapy, and patient compliance.

Robinson et al. provide a review of the approximate incidence of lesser tuberosity fractures, as well as the functional outcomes following operative treatment in a consecutive series of patients collected over eight years. The authors identified 22 adult patients who had a fracture of the lesser tuberosity, leading them to estimate a low annual incidence of 0.46 per 100,000 population/year during the study period, with most patients regaining nearly normal range of motion in the affected shoulder by three months. They concluded that a lesser tuberosity fracture, without an associated humeral head or greater tuberosity fracture, is a rare injury and that open reduction and internal fixation provides excellent restoration of function and range of shoulder movement with a low risk of complications.

Figure A represents an AP radiograph of the right shoulder showing an isolated lesser tuberosity fracture of the proximal humerus. Illustration A demonstrates the avulsed lesser tuberosity with a red arrow.

Incorrect Answers:
Answer 1: The ability to maintain external rotation with the arm locked at the side (demonstrating lack of a lag sign) would be testing the rotator cuff tendons that attach to the greater tuberosity, not the subscapularis, which attaches to the lesser tuberosity.
Answer 2: Posterior shoulder dislocations, not anterior dislocations, have a unique association with isolated lesser tuberosity fractures and should be carefully assessed for in the history, exam, and imaging.
Answer 3: Klumpke's palsy can occur from traction injuries to the brachial plexus after a fall, often affecting the lower nerve roots, but this is not associated with an isolated lesser tuberosity fracture of the proximal humerus as shown in Figure A.
Answer 5: Weakness with empty can testing would signify a supraspinatus injury, which is not consistent with an isolated lesser tuberosity fracture.