Abstract
Purpose:
Malpositioning of the acetabular cup component in total hip arthroplasty can result in increased wear, early nonseptic loosening and is the most common cause of dislocation. Previous research has defined a safe zone with an inclination of 40±10 degrees and anteversion of 15±10 degrees. The purpose of this study was to compare cup placement using imageless navigation to a matched control group using CT based measurements.
Methods:
30 patients receiving a primary hip replacement were included. Alignment of the implant is based on the acquisition of landmarks (ASIS and pubic tubercle) and placement of tracking pins into the ASIS. The target position for all patients was 45 degrees of inclination and 15 degrees of anteversion. A multi-slice CT scan was used to assess cup position.
Results:
There was no significant difference between mean inclination (p=0.11) and anteversion (p=0.24) but a statistically significant difference for mean deviation from the desired position for inclination (p=0.003) and anteversion (p=0.007). There was a significant difference in the percentages of correctly placed cups with inclination (p=0.046) and with anteversion (p=0.006). Combining both anteversion and inclination there was a significant difference (p=0.01).
Conclusion:
Computer navigation for total joint arthroplasty, if helpful to the surgeon, has to increase reliability of component placement and show a significant reduction in variation compared to freehand techniques. We demonstrated a significant increase in accuracy of placement of acetabular cups within the desired position and safe zone using imageless navigation.
