Supplemental Table 1.

ICD-9 procedure modifier codes used to identify patients undergoing computer- or robot-assisted THA.

ICD-9 procedure modifier codes
Computer-assisted
00.31	Computer-assisted surgery with computed tomography/ computed tomography angiography
00.32	Computer-assisted surgery with MR/MRA
00.33	Computer-assisted surgery with fluoroscopy
00.34	Imageless computer-assisted surgery
00.35	Computer-assisted surgery with multiple data sets
00.39	Other computer-assisted surgery
Robot-assisted
17.41	Open robot-assisted procedure
17.49	Other unspecified robot-assisted procedure

MR/MRA, magnetic resonance/magnetic resonance angiography.