Table 2.

Numbers of patients and vertebrae for training, validating, and testing

Parameter	Training data		Validation data		Test data
	Fracture (n = 655)	Normal (n = 3752)	Fracture (n = 226)	Normal (n = 1280)	Fracture (n = 220)	Normal (n = 1326)
Anatomic location
Thoracic	34 (223)	49 (1827)	38 (87)	46 (589)	36 (79)	48 (637)
Lumbar	66 (432)	51 (1925)	62 (139)	54 (691)	64 (141)	52 (689)

Data presented as % (n). The vertebrae above T9 in patients with plain lateral radiographs were not consistently clearly visualized because of the diaphragm or lung markings. Accordingly, YOLOv3 detected approximately eight vertebrae (three thoracic and five lumbar vertebrae) in one plain lateral radiograph in the dataset, regardless of whether the vertebrae was fractured or nonfractured. The vertebrae marked with a bonding box by YOLOv3 were categorized by thoracic and lumbar location and subcategorized into fractured and nonfractured vertebrae based on prior human labels by physicians.