Reduction in Variability of Acetabular Cup Abduction Using Computer Assisted Surgery: A Prospective and Randomized Study

Abstract

Optimal orientation of the acetabular component of a total hip prosthesis is an important factor in determining the early and long-term result of a total hip arthroplasty (THA). Conventional positioning of the cup component is usually done using a free-hand method, or with the help of a mechanical acetabular alignment guide. However, these methods have proven to be inaccurate, and a great variation in orientation of the cup is found postoperatively. In this study, we wished to determine if the variability of the abduction angle of acetabular cups could be reduced with the use of computer navigation. The abduction angles of the acetabular components of three groups of 50 THAs were assessed. In the first group, a free-hand method was used to position the cup component. This group was operated in the period before we started using computer navigation for hip surgery. In the second group, CT-based computer navigation was used to plan and help position the cup. The third group consisted of 50 THA cases in which a free-hand method was used to position the cup, although these procedures were performed in the period after we had begun using the Computer Assisted Surgery (CAS) system. The variability in cup abduction angle was assessed in all three groups and compared. There was a significant reduction in variability in the CAS group compared to the first group. There was also a reduction in variability in the CAS group compared to the third group, although this was not statistically significant. It is concluded that the use of computer navigation helped the surgeon to place the cup component with less variability of the abduction angle, and, more importantly, we found that no cups were placed in the more extreme positions (outliers).

Application of Rapid Prototyping Pelvic Model for Patients with DDH to Facilitate Arthroplasty Planning: A Pilot Study

“…Intraoperative navigation systems have been used for over a decade. Greater accuracy can be achieved by navigated implantation when compared with traditional manual implantation in respect of cup-positioning [27][28][29][30][31][32][33]. Although a number of application researches on navigated cup implantation have been published, there are inadequate data about patients with DDH.…”

“…(2) A more complicated process matching patient's image data and anatomical structure and a longer operation duration. (3) Increased exposure to radiation of both surgeons and patients [28,35]. (4) Other restrictions like high cost, high human and system error rate and long learning curve.…”

Computer-assisted orthopedic surgery

“…This type of navigation is more useful for guiding socket orientation during THA than a conventional mechanical guide. 11,31 It can also be used to guide femoral components, control limb length, and select optimal modular parts for THA. 43 For periacetabular osteotomy, guiding osteotomes using this method increases the safety and accuracy of the procedure.…”

Accuracy of Computer Navigation for Acetabular Component Placement in THA

“…In the past decade, the accuracy of these methods has come into question. Freehand [23,36] and mechanically guided [6,12,16,31] techniques have resulted in inaccurate cup inclination and anteversion, with numerous cups placed outside the predefined safe zone as described by Lewinnek et al [24]. Cup position using these techniques, even in the hands of experienced surgeons, may result in considerable positional outliers.…”