Abstract
A novel CT-free image-guided navigation system for acetabular cup placement has been designed, implemented and evaluated in laboratory and clinical environments. The most common postoperative complications for total hip arthroplasty (THA), subluxation and dislocation, is directly related to acetabular component orientation. Recent developments in the area of CT-based cup navigation have proven to be a valuable aid. However, a CT scan often unwarranted and has a significant impact on the total cost of treatment.
The method proposed in this paper utilizes reference coordinates from the anterior pelvic plane (APP) to compute the angular orientation of the cup. The APP is aligned to a vertical plane of a standing patient defined by the two anterior superior iliac spines and the pubic tubercles. A hybrid strategy for the acquisition of these landmarks has been introduced involving percutaneous pointer-based digitization with the possibility of non-invasive bi-planar landmark reconstruction using multiple registered fluoroscopy images. An intuitive graphical user interface, combined with a sterile virtual keyboard control, effectively support the navigation of acetabular preparation and cup placement.
A detailed validation of the system was performed in a laboratory setting. Seven full body human specimens were used to confirm the APP reference concept using custom made software to simulate worst case scenarios.
System usability was evaluated throughout an early clinical trial involving 25 patients. A postoperative study of all patients found that the accuracy was better than 4° inclination and 5° anteversion under standard clinical conditions. This implies that there is no significant difference in performance from the established CT-based navigation methods.
The abstracts were prepared by Nico Verdonschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, University Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
