Ecchymosis at the zygomatic buttress specifically indicates trauma to the zygomatic bone, as this area forms a critical structural point of the zygoma. The zygomatic buttress transmits masticatory forces and connects the zygoma to the maxilla and frontal bone; hence, fractures here lead to visible bruising and swelling. Other facial bones do not produce ecchymosis localized to the zygomatic buttress. Identification of this sign aids in diagnosing zygomatic complex fractures, critical for planning surgical repair to restore facial contour and function. Prompt recognition prevents complications such as malar flattening and orbital dysfunction.

Reference: Oral and Maxillofacial Trauma, Fonseca, Edition 4.