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Effects of the Flip Technique on Measurement Accuracy of the Acetabular Cup Position Using a Portable Hip Navigation
Hiromasa Tanino1, Ryo Mitsutake1, Hiroshi Ito1
1Department of Orthopaedic Surgery, Asahikawa Medical University, Asahikawa city, Hokkaido, Japan.
Background:
Accurate cup placement is performed for achieving satisfactory outcomes after total hip arthroplasty. Portable hip navigation systems are novel intraoperative tools for accurate cup placement. Several factors have been reported to affect their accuracy, including the flip technique, in which the pelvic reference plane is registered in the supine position and the patient is subsequently repositioned to the lateral decubitus position for surgery. The effectiveness of the flip technique remains a subject of debate. Therefore, this study assessed and compared the accuracy of cup position measurements using an inertial portable hip navigation system in the lateral decubitus position.
Methods:
Measurement accuracy was assessed in 78 hips. The accuracy of the system was compared with and without the flip technique, employing an identical method for registering the pelvic reference plane. Cup angles displayed on the system during surgery were compared with those measured postoperatively.
Results:
Measurement errors with and without the flip technique were 3.7° ± 2.8° and 2.8° ± 2.6° for cup abduction (P = .029) and 2.9° ± 2.5° and 3.9° ± 2.9° for cup anteversion (P = .037). The system achieved measurement errors within 10° in 97 and 98% of hips for cup abduction (P = .636), and 99 and 96% of hips for cup anteversion (P = .364) with and without the flip technique.
Conclusions:
This system provided reliable intraoperative measurements of cup positions, irrespective of the use of the flip technique. However, cup abduction measurements were more accurate without the flip technique, while cup anteversion measurements were more accurate with the flip technique.
