Related Experiment Video
Updated: Jan 5, 2026
Individualized Stem-positioning in Calcar-guided Short-stem Total Hip Arthroplasty
Published on: February 27, 2018
Anterior pelvic plane registration accuracy and cup position measurement using ultrasound- and pointer-based
Hartmuth Kiefer1,1, Jannis Löchel2,1, Keosun Sambo1
1Department of Orthopaedic and Trauma Surgery, Lukas-Hospital Bünde, Germany.
Background:
Incorrect cup positioning in primary total hip arthroplasty is known as a risk factor for early implant failure. The use of navigation systems leads to more accurate cup positioning.
Objective:
The aim of this study was to compare the registration accuracy of the anterior pelvic plane and the measurement accuracy of the definite cup position for a pointer computer-assisted orthopaedic navigation system (P-CAOS) and an ultrasound-based navigation tool (US-CAOS) in an intra-individual study design.
Methods:
Anterior pelvic plane registration was performed in 44 patients receiving a primary total hip arthroplasty with P-CAOS and US-CAOS. The cup implantation was performed using US-CAOS. Intraoperatively, the cup position was assessed using P-CAOS and US-CAOS. The postoperative cup position was determined via CT scan. Inclination and anteversion errors were calculated using intraoperative values and CT data. All operations were performed by a single, high-volume surgeon using a minimally invasive anterolateral approach.
Results:
The mean inclination error was 0.9∘ in the US-CAOS group and -1.1∘ in the P-CAOS group. This was not statistically significant. The mean anteversion error was significantly reduced (p< 0.001) in the US-CAOS group (1.4∘) compared to the P-CAOS group (-8.0∘). Significantly more cups (23 of 44; 52%) in the P-CAOS group were outliers regarding to the defined anteversion error range of 15∘± 10∘. Outliers in the US-CAOS group amounted to two (of 44; 5%) (p< 0.001). The number of outliers regarding the inclination error range of 40∘± 10∘, did not differ significantly between the P-CAOS (2; 5%) and US-CAOS (1; 2%) group.
Conclusion:
We were able to show a systematic anterior pelvic plane registration error in this intraindividual study design. US-CAOS based APP landmark registration showed to be significantly more precise compared to P-CAOS registration. The anteversion error of the cup using US-CAOS showed to be significantly reduced compared to the P-CAOS method.
