Introduction: Both the proximal humerus fracture and the acromioclavicular (AC) joint injury are commonly found in shoulder girdle injuries but there are no reports of them presenting together. The mechanism of the AC joint injury is similar to that of the proximal humerus fracture, a lateral impact to the shoulder girdle, but the arm positions are different, as the AC injury usually involves an adducted arm while the proximal humerus fracture normally occurs with the arm in a neutral position. Herein we report, to our knowledge, the first case of a combined proximal humerus fracture and AC joint injury.
Case presentation: A 40-year-old Thai male presented with right shoulder pain after a motorcycling accident. He was diagnosed as a proximal humerus fracture (Neer 4-part fracture). Open reduction and internal fixation with a Philos plate (Synthes®) in the supine position were then performed. However, an AC joint injury (Rockwood type III) was then noticed on the post-operative X-ray taken in the upright position. We had missed the AC joint injury because all pre-operative imaging had been done only in the supine position.
Conclusion: The combination of these two fracture types is uncommon and has not been previously reported. Our report suggests that in cases of a proximal humerus fracture resulting from a high-energy mechanism, the surgeon should obtain an X-ray or perform fluoroscopy with the patient in the upright or semi-upright position before surgery to avoid missing an AC joint injury.
Keywords: Acromioclavicular joint injury; Combined; Proximal humerus fracture; Supine position.
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