Comparison of total hip replacements cup orientation and position. Navigation vs. conventional manual implantation of hip prostheses

BACKGROUND: Aim of this in-vitro study was to compare the hip cup placement for total hip replacement when using different navigation systems compared with the traditional, non-navigated technique. METHODS: Five different navigation systems were used: the CT-less systems Navitrack, Orthopilot and Surgetics Station, as well as the CT-based Navitrack and VectorVision. Three different surgeons carried out five cup implantations using all navigation systems and the manual approach on a surgery dummy. Cup orientation (inclination and anteversion) and the cup position (achieved cup center) were determined with a coordinate measuring machine. RESULTS: In the manual group the variability of the cup orientation was higher in comparison and hardly influenced by the surgeon. Navigation was identified as a significant factor for smaller deviations from planned inclination and anteversion angles (p<0,001 for both). Cup position was not affected by surgeon in the manual group (p=0,966). Compared with manual technique, the cup misplacement vector was significantly smaller in the CT-Navitrack group (p<0,001) but higher in the Navitrack (CT-less) and VectorVision group (p<0,001). CONCLUSIONS: The use of computer navigation will help the surgeon to orientate the acetabular component more accurately but not necessarily with regard to cup positioning.