Image-Less THA Cup Navigation in Clinical Routine Setup: Individual Adjustments, Accuracy, Precision, and Robustness

Area of Science:

• Orthopedic Surgery
• Medical Engineering
• Radiology

Background:

• Accurate prosthetic cup placement is vital for total hip arthroplasty (THA) success, even after the decline of Lewinnek's safe zone.
• Surgical navigation systems enhance prosthetic cup placement accuracy.
• Evaluating acetabular component position traditionally requires postoperative CT scans, limiting large-scale studies.

Purpose of the Study:

• To assess the intraoperative adjustments of cup positioning compared to established target values (40° inclination, 15° anteversion).
• To evaluate the accuracy, precision, and robustness of an image-less navigation system in routine clinical THA.
• To determine the clinical acceptability of an image-less navigation system for acetabular component placement.

Main Methods:

• A retrospective accuracy study of 367 navigated primary THAs using an image-less navigation system (PiGalileoTM).
• Cup orientation was assessed intraoperatively and postoperatively using the validated HipMatch software on anterior-posterior pelvic X-rays.
• Individual adjustments, accuracy, precision, and outliers were analyzed using statistical methods including Bland-Altman analysis.

Main Results:

• Intraoperative adjustments showed cups were placed with higher inclination (mean 3.2°) and anteversion (mean 5.0°) than target values (p < 0.001).
• Navigated cup placement accuracy was -1.7° ± 3.0° for inclination and -4.9° ± 6.2° for anteversion (p < 0.001).
• Precision was higher for inclination (SD 3.0°) than anteversion (SD 6.2°) (p < 0.001), with a low outlier prevalence (1.9% inclination, 1.63% anteversion).

Conclusions:

• Image-less navigation systems offer accurate and reliable intraoperative feedback for THA.
• While accuracy and precision are lower than CT-based systems, particularly for anteversion, the results are clinically acceptable.
• This navigation approach aids in achieving adequate acetabular component placement with minimal outliers, especially in complex cases involving hip-spine relationships.