Accuracy and potential pitfalls of fluoroscopy-guided acetabular cup placement

Abstract

Using a total of 30 cadaveric hips, the accuracy of a fluoroscopy-based computer navigation system for cup placement in total hip arthroplasty (THA) was investigated and an error analysis was carried out. The accuracy of placing the acetabular component within a predefined safe zone using computer guidance was compared to the precision that could be achieved with a freehand approach. Accurate control measurements of the implanted cup were obtained using fiducial-based matching to a pre-operative CT scan with respect to the anterior pelvic plane. A significantly higher number of cups were placed in the safe zone with the help of the navigation system. The variability of cup placement could be reduced for cup abduction but not substantially for cup version. An error analysis of inaccurate landmark reconstruction revealed that the registration of the mid-pubic point with fluoroscopy was a potential source of error. Keeping this pitfall in mind, fluoroscopy-based navigation in THA is a useful tool for registration of the pelvic coordinate system, particularly those points that cannot be reached by direct pointer digitization with the patient in the lateral decubitus position.

Six Sigma Analysis of Minimally Invasive Acetabular Arthroplasty: A Preliminary Investigation

“…Only one cadaver was used. However, published studies and our prior study used only limited numbers of cadaver specimens [17,29,35,38,40]. In clinical practice, there undoubtedly would be more variability for imageless referencing if more specimens would have been used.…”

“…In our example, we chose 10°above and below the reference position based on the historical comparison of Lewinnek et al [25]. To analyze the comparative ability of the Six Sigma ratio, we evaluated other similar computer navigation acetabular studies that adequately reported descriptive statistics [9,17,29,35,37,40] ( Table 3). CT for navigation referencing provided satisfactory precision, whereas fluoroscopy was capable in some studies but not in others.…”

Effect of CT slice thickness on accuracy of implant positioning in navigated total hip arthroplasty

“…It is not too difficult to measure the inclination of the cup intraoperatively, but it is difficult to recognize the sagittal pelvic plane with the patient in the decubitus position, with the result that accuracy in controlling cup anteversion without navigation is inferior to that when using navigation. Many imageless navigation systems can calculate the anatomical angle of the pelvis, but this has been reported to be inaccurate for cases of severe deformity in dysplasic hip patients [6]. As mentioned previously, the majority of Japanese hip osteoarthritis cases result from developmental dysplasia, and many of these patients exhibit severe deformity.…”

“…However, while CT-based navigation is regarded as the most accurate system available at present [5], it also has several disadvantages: it is expensive, time-consuming, and involves significant radiation exposure for the patient, while imposing limitations on the choice of implant design. The degree of radiation exposure for the patient [2,6] when using CT-based navigation depends on the pitch of CT employed. The use of thicker-pitched CT entails lower radiation exposure; however, accuracy of navigation is suspected to be worse.…”

“…Furthermore, as a standard THA procedure is performed with the patient in the decubitus position, it is difficult to check the implant position properly on the table. Therefore, numerous types of navigation system, including imageless, fluoroscopy-guided and CT-based systems, have been developed and improved to enable proper positioning in THA [2][3][4][5][6].…”