Accuracy of acetabular cup placement using CT-based navigation in total hip arthroplasty: Comparison between obese and non-obese patients

Background: In obese patients, malpositioning of the acetabular cup increases the risk of dislocation in total hip arthroplasty (THA). The aim of this study was to determine whether obesity affects the accuracy of acetabular cup positioning using a computed tomography (CT)-based navigation system. Methods: We retrospectively evaluated 226 consecutive patients who underwent cementless primary THAs assisted by the CT-based hip navigation system. We divided the patients into three groups according to body mass index (BMI) and examined the difference between preoperative planning and postoperative implantation angles from CT data. Results: There was no significant correlation between BMI and both inclination and anteversion differences (R = 0.028 and R = 0.045, respectively). There were no significant differences among the BMI < 25, 25 <= BMI < 30, and BMI >= 30 groups (p value: 0.725, 0.934, respectively); between the BMI < 25 and BMI >= 25 groups (p value: 0.542, 0.697, respectively); and between the BMI < 30 and BMI >= 30 groups with regard to inclination and anteversion (p value: 0.859, 0.456, respectively). Moreover, similar findings were observed with regard to the distance between the preoperative planning and postoperative cup positioning for the transverse, anteroposterior, and craniocaudal axes of the pelvis. Conclusion: We found that the accuracy of acetabular cup placement using CT based-navigation in THA was not affected in obese patients. Therefore, THAs with a CT-based navigation system are considered useful in obese patients. (c) 2018 The Japanese Orthopaedic Association. Published by Elsevier B.V. All rights reserved.