Accuracy of acetabular cup implantation, as a function of body mass index and soft-tissue thickness, with a mechanical intraoperative support device: A retrospective observational study

Abstract

Background HipCOMPASS, a mechanical intraoperative support device used in total hip arthroplasty (THA), improves the cup-alignment accuracy. However, alignment accuracy in obese patients has not been examined. We aimed to compare the cup-alignment accuracy, using HipCOMPASS, between patients with and without obesity. Methods We retrospectively evaluated 448 consecutive patients who underwent primary THA using HipCOMPASS. We measured the soft-tissue thickness of the anterior-superior iliac spine (ASIS) and pubic symphysis using preoperative computed tomography (CT) images and the difference in cup angle pre- and postoperatively based on the cup-alignment error on CT. We used Pearson coefficients to determine the correlation of body mass index (BMI) and soft-tissue thickness with cup-alignment error. We created receiver operating characteristic (ROC) curves to determine the cutoff value for statistically significant cup-alignment error factors in radiographic inclination and anteversion of ≥ 5°. Results There were significant correlations between the absolute value of radiographic anteversion difference and BMI (r = 0.205), ASIS thickness (r = 0.419), and pubic symphysis thickness (r = 0.434). The absolute value of radiographic inclination difference was significantly correlated with ASIS (r = 0.257) and pubic symphysis thickness (r = 0.202). The ROC curve showed a pubic symphysis thickness of 37.2 mm for a ≥ 5° implantation error in both radiographic inclination and anteversion simultaneously. The cup-alignment error for HipCOMPASS was large in patients whose pubic symphysis thickness was ≥ 37.2 mm on preoperative CT. Conclusion We recommend using methods other than HipCOMPASS, including computed tomography-based navigation systems, in obese patients.

Accuracy of ZedView, the Software for Three-Dimensional Measurement and Preoperative Planning: A Basic Study

“…In addition, it also includes 3D construction and measurement software and 3D dynamic-analysis software. The software can perform various preoperative planning procedures, simulate postoperative bone movements during such planning, and perform three-dimensional measurements and evaluations of postoperative implant placement, angulation, and alignment, as well as rotation angles after osteotomy [ 13 , 19 , 20 ]. Although the measurement accuracy of this surgical-planning software has been evaluated using model bones [ 21 ], none of the previous studies evaluated its accuracy using human bones.…”