Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Clinical Science

Program

Surgery

Supervisor

Lanting, Brent

2nd Supervisor

Howard, James Layton.

3rd Supervisor

Teeter, Mathew G.

Abstract

Introduction

Malposition of the acetabular component has been thought to have an influence on increasing increase the risk instability, impingement, and ultimately revision surgery. Hip navigation technology has been developed to provide the surgeon with real time intraoperative metrics to make critical decisions in implant placement. The goal of this study was to compare the accuracy of acetabular component positioning in direct anterior approach hip replacements using conventional fluoroscopy only technique, fluoroscopic image dependent navigation, and imageless navigation.

Methods

A retrospective data collection and prospective analysis was conducted for this study. After sample size calculations, fifty patients were collected for each group for analysis. Intraoperative cup inclination and anteversion was collected for all three groups. Post-operative AP radiographs at six weeks post-surgery were analysed in all three cohorts to determine final inclination and anteversion. Two readers conducted radiographic analysis. The primary outcomes for the study included: absolute deviation from intraoperative and post operative anteversion/inclination, absolute mean deviation from surgeon’s target zone, and number of cups within target zone. Secondary outcomes included operative time and 60-day complications (dislocation, infections, periprosthetic fracture). In previous literature, the use Lewinnek’s safe zone has been utilised as the ideal target for acetabular component position. In our study, we used specific surgeon’s preference for the target zone. Surgeon A had a target zone of inclination 40O +/- 5O and anteversion 20O +/- 5O. Surgeon B had a target zone of inclination 35O +/- 5O and anteversion 15O +/- 5O.

Results

The inter-rater reliability demonstrated good agreement for radiographic analysis between observers for inclination (ICC = 0.855 (n=200)) and anteversion (ICC = 0.894 (n=200)). Our study analysed the absolute deviation of cup position determined by 6-week post-operative radiographs from target position, the mid-point of each surgeon’s specific safe zone. This variation was defined as placement error. There was no significant regarding final cup position from desired targets of anteversion (P=0.08) and inclination (P=0.94) when comparing all three groups. Our study also looked at intraoperative versus post operative cup positioning accuracy known as estimated error. Conventional fluoroscopic use demonstrated statistically significant inaccuracy in inclination and anteversion (P<0.0001). Imageless navigation demonstrated significant inaccuracy in anteversion (P=0.00043).

In terms of final cup positioning, Surgeon A achieved 59% (16/27 cups) within the specific target while Surgeon B obtained 48% (11/23 cups) when using conventional fluoroscopy only. With the use of image guided navigation, VELYS, Surgeon A achieved 83% (20/24 cups) while Surgeon B obtained 69% (18/26 cups) within their defined zones. With the use of imageless navigation, Surgeon A had 76% (20/26 cups) while Surgeon B had 50% (12/24 cups) within target zone.

Imageless navigation demonstrated increase length of operative time in comparison to VELYS and fluoroscopy only group on average with 75.5 mins (P<0.0001). There was no difference in complication rates across all three groups at 60 days follow-up.

Conclusion

Our study found that in comparison to conventional fluoroscopy, hip navigation allowed for more accurate placement of cups. Image guided navigation demonstrated significant estimated error in evaluation of cup anteversion. We found that operative time was increased when using imageless navigation.

Summary for Lay Audience

Malposition of the acetabular component has been thought to have an influence on increasing increase the risk instability, impingement, and ultimately revision surgery. Hip navigation technology has been developed to provide the surgeon with real time intraoperative metrics to make critical decisions in implant placement. The standard use of intraoperative fluoroscopy has been adopted to aid the surgeon in component placement in the direct anterior approach. At our institution, we utilise two hip navigation systems in direct anterior hip replacements. The image guided navigation system relies on intraoperative fluoroscopic imaging to create a digital map for intraoperative implant positioning. The imageless navigation system relies on intraoperative kinetic data points of anatomical landmarks to provide real-time component position parameters.

The goal of this study was to compare the accuracy of component positioning in direct anterior approach hip replacements using conventional fluoroscopy only technique, fluoroscopic image dependent navigation, and imageless navigation. This was achieved by comparing intraoperative measurements of acetabular component position with postoperative radiographic measurements.

We hypothesized that the use of navigation would demonstrate improved accuracy in comparison to conventional technique. When comparing VELYSTM (image-guided navigation) and INTELLIJOINT HIP ® (imageless navigation) accuracy, we predicted that the use of the two navigation systems will be equivalent. We hypothesized that operative time would be increased with the use of navigation however complications would be similar across all groups.

Our study found that in comparison to conventional fluoroscopy, hip navigation allowed for more accurate placement of cups.Image guided navigation demonstrated significant estimated error in evaluation of cup anteversion. We found that operative time was increased when using imageless navigation.

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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