Accuracy of Acetabular Cup Position Using CT Navigation During Total Hip Arthroplasty in Patients With Developmental Dysplasia of the Hip.

Background CT-based navigation systems for total hip arthroplasty (THA) have been used to prevent complications in cup placement. It has been reported that the accuracy of cup alignment, known as inclination and anteversion, has improved with the use of a navigation system. However, while cup placement height and medialization are important, there are few reports on the accuracy of cup positioning. Methods CT-based navigation was used for cup placement, and the discrepancy between preoperative planning and postoperative CT evaluation was examined in three dimensions. It was also investigated whether the degree of developmental dysplasia of the hip (DDH) (Crowe classification and double floor) made a difference in the accuracy of cup placement. Results The absolute discrepancies between preoperative plans and postoperative measurements were 1.7 (range 0-8) mm in the transverse axis, 2.3 (range 0-12) mm in the sagittal axis, and 2.2 (range 0-11) mm in the longitudinal axis. No significant variation was found in any of the three-dimensional measurements taken for all Crowe classifications, with or without the presence of an acetabular "double floor". However, the double-floor subgroup showed a trend toward greater discrepancy in all directions. Conclusions CT-based navigation systems can position the cup with high three-dimensional accuracy in primary THA without affecting acetabular deformity.