Smartphone Improves Accuracy of Alignment Guide for Acetabular Cup Positioning: a Study in Plastic Bone Model

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Hemmaraj Sukapan


Background: Total hip arthroplasty requires accuracy of acetabular cup positioning. Traditional acetabular alignment guide is mostly relied on surgeon’s perception and probably cause error. Use of smartphone with angle measurement application may increase its accuracy.
Objective: To determine the accuracy of acetabular cup positioning with 2 types of alignment guides (X-bar and double bar), comparing between alignment guide alone and combined with smartphone.
Material and method: The pelvis plastic model was fixed to the x-ray table in lateral position. Ten surgeons placed acetabular cups at the target angle of operative inclination 45° and anteversion 20° by using 2 types of alignment guides. Thereafter, the cups were placed by using alignment guide combined with smartphone. Standard AP radiographs were taken and each surgeon repeated cup placement 5 times per tecnnique. Radiographic inclination and anteversion were measured by using PACS program. Comparison between each techniques were analyzed by t-test and Wilcoxon’s rank sum test.
Results: The cups positioned by alignment guide alone had more inclination than by using with smartphone significantly in both X-bar type [47.5° (SD 1.5°) vs 44.9° (SD 0.6°), p<0.001] and double bar type [46.3° (SD 1.4°) vs 45.6 °(SD 1.0°), p=0.004]. They also had less anteversion in X-bar type [10.6° (SD 2.0°) vs 12.6° (SD 2.6°), p<0.001] and double bar type [9.3° (SD 1.7°) vs 10.1° (SD 2.5°), p=0.208]. Using alignment guide combined with smartphone yielded cup position in less inclination in X-bar type (p=0.001) and more anteversion in double bar type (p<0.001).
Conclusion: Smartphone improved the accuracy of alignment guide for positioning acetabular cup by significantly reduced error of radiographic inclination and anteversion. Using with the X-bar alignment guide was more accurate than the double bar guide.


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Sukapan, H. (2022). Smartphone Improves Accuracy of Alignment Guide for Acetabular Cup Positioning: a Study in Plastic Bone Model. Lampang Medical Journal, 35(2), 56–67. Retrieved from
Original Article


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