Abstract
Introduction
Total hip arthroplasty has become an increasingly common procedure. Improper cup position contributes to bearing surface wear, pelvic osteolysis, dislocations, and revision surgery. The incidence of cup malposition outside of the safe zone (40° ± 10° abduction and 15° ± 10° anteversion) using traditional techniques has been reported to be as high as 50%. Our hypothesis is that computer assisted navigation will improve cup placement in total hip arthroplasty compared with traditional techniques.
Methods
This study retrospectively evaluated the position of 425 consecutive cups placed during primary total hip arthroplasty performed over a two-year period, from 8/1/2012 to 8/1/2014. All cups were placed with a direct-anterior muscle-sparing approach with computer-assisted imageless navigation by a single surgeon. Real-time intraoperative “screen shots” were taken of cup placement. Standard antero-posterior postoperative radiographs of the pelvis were taken within 6 weeks of surgery in the operating surgeon's office using the same standardized protocol for each patient. The radiographs were evaluated by two separate investigators for final abduction and anteversion utilizing the same method as other studies. Statistics were descriptive in nature.
Results
Intraoperative navigation screenshots from 425 hips showed that 100% were within the safe zone for abduction and anteversion. Postoperative radiographic review showed that 97% were within the safe zone for abduction (Mean 41 degrees, Range 29–54 degrees), 96% were within the safe zone for anteversion (Mean 16 degrees, Range 4–38 degrees) and 94% were within the safe zone for both abduction and anteversion.
Conclusion
In our series, computer assisted navigation improved cup placement in total hip arthroplasty compared with traditional techniques as reported in current literature. Cup position in our study, was within the safe zone for abduction and version at a comparable rate to similar studies examining THA's performed with navigation.
