Accuracy of portable navigation during THA in patients with severe developmental dysplasia of hip

Introduction Correct cup placement in total hip arthroplasty (THA) for patients with developmental dysplasia of the hip (DDH) is considerably difficult. This study aimed to analyze the orientation accuracy of cup insertion during THA using a portable navigation system in patients with DDH. Materials and methods In this retrospective cohort study, we analyzed data from 64 patients who underwent THA using infrared stereo camera-matching portable navigation. Patients underwent THA via the anterolateral approach in the lateral decubitus position. Navigation records for intraoperative cup angles, postoperative cup angles measured on computed tomography (CT) images, and cup angle measurement differences were measured and compared between patients with non-DDH/mild DDH and severe DDH. Furthermore, the predictive factors for outliers of accurate acetabular cup placement were analyzed. Results The average measurement absolute abduction differences (postoperative CT-navigation record) were 3.9 +/- 3.5 degrees (severe DDH) and 3.3 +/- 2.6 degrees (non-DDH/ mild DDH), and the anteversion differences were 4.7 +/- 3.4 degrees (severe DDH) and 2.3 +/- 2.1 degrees (non-DDH/ mild DDH). The anteversion difference was different between the two groups. Multivariate analysis showed that the navigation difference (absolute difference in anteversion between postoperative CT and navigation records of > 5 degrees) was significantly associated with severe DDH (odds ratio [OR]: 3.3; p = 0.049, 95% confidence interval [CI]: 1.0-11.1) and posterior pelvic tilt (OR: 1.1; p = 0.042, 95% CI: 1.0-1.27). Conclusions In patients with severe DDH, it is important to pay close attention during THA using portable navigation. However, the average difference was < 5 degrees even in patients with severe DDH, and the accuracy may be acceptable in a clinical setting when the cost is considered.