A system for aligning an acetabular prosthetic component in a patient's surgically prepared acetabulum, the system comprising: a reference sensor module securable to the patient's bony anatomy and including (i) a first orientation sensor configured to generate first sensor data indicative of the orientation of the patient's bony anatomy in three-dimensions and (ii) a first communication circuit to transmit the first sensor data; an inserter sensor module securable to an acetabular prosthetic component inserter, the inserter sensor module including (i) a second orientation sensor configured to generate second sensor data indicative of the orientation of the acetabular prosthetic component inserter in three-dimensions, (ii) a second communication circuit to transmit the second sensor data, and; a display module separate from the reference sensor module and the inserter sensor module, the display module including (i) a display, (ii) a third communication circuit configured to receive the first sensor data and the second sensor data, and (iii) a processing circuit to determine an orientation of an acetabular prosthetic component coupled to the acetabular prosthetic component inserter relative to the patient's bony anatomy based on the first sensor data and the second sensor data, display indicia of the determined orientation of the acetabular prosthetic component on the display, and characterised in that the inserter module further includes an alignment indicator, the processing circuit being arranged to communicate with the inserter sensor module to activate the alignment indicator in response to the determined orientation being within threshold amount of a reference orientation and wherein the processing circuit of the display module is configured to determine a coordinate system conversion factor to convert the first sensor data from a coordinate system of the inserter sensor module to a patient coordinate system of the patient's bony anatomy and determine the orientation of the acetabular prosthetic component inserter relative to the patient's bony anatomy using the coordinate system conversion factor. a reference sensor module securable to the patient's bony anatomy and including (i) a first orientation sensor configured to generate first sensor data indicative of the orientation of the patient's bony anatomy in three-dimensions and (ii) a first communication circuit to transmit the first sensor data; an inserter sensor module securable to an acetabular prosthetic component inserter, the inserter sensor module including (i) a second orientation sensor configured to generate second sensor data indicative of the orientation of the acetabular prosthetic component inserter in three-dimensions, (ii) a second communication circuit to transmit the second sensor data, and; a display module separate from the reference sensor module and the inserter sensor module, the display module including (i) a display, (ii) a third communication circuit configured to receive the first sensor data and the second sensor data, and (iii) a processing circuit to determine an orientation of an acetabular prosthetic component coupled to the acetabular prosthetic component inserter relative to the patient's bony anatomy based on the first sensor data and the second sensor data, display indicia of the determined orientation of the acetabular prosthetic component on the display, and characterised in that