Accuracy of Acetabular Cup Positioning by Using Smartphone: Comparison between Two Program Applications and Operating System

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Narat Prasopchoke


Background: Acetabular cup positioning in total hip arthroplasty is usually performed by using alignment guide for cup orientation and often difficult to assess. Smartphone technology of the iPhone and its downloaded applications were found to be accurate for improving acetabular cup placement in the optimal zone.
Objective: To compare the accuracy of acetabular cup positioning between using single application of 1 Android phone with alignment guide and dual applications of 2 iPhones without alignment guide.
Material and method: An experimental study was conducted on pelvic sawbone secured on the table in lateral decubitus position. Each surgeon (5 experienced staffs and 5 residents) placed cementless cup into the pelvis 20 times by holding an insertion rod and orientating by two methods. Firstly, handling 1 Android phone on top and parallel to the alignment guide and secondly, handling 2 iPhones on top the insertion rod and parallel to table border. The target positions  were operative inclination 45o/ operative anteversion 20o (OI45o/OA20o) and OI40o/OA30o. AP digitized radiographs were taken. Radiographic inclination (RI) and radiographic anteversion (RA) were measured and calculated by using PACS program. Cup positions were analyzed, compared between each methods and between two groups of surgeons by using t-test and Mann-Whitney U test.
Results: Using Android phone with alignment guide at OI45o/OA20o target resulted less average RI than using iPhones (44.9o± 0.6o vs 45.8o± 1.1o, p<0.001) but more average RA (12.6o± 2.6o vs 11.0o± 3.1o, p=0.009). At OI40o/OA30o target, there was no difference between groups in both RI (p=0.524) and RA (p=0.526). Cups positioned by experienced staffs had more RA than by residents (13.0o± 2.8o vs 10.6o± 2.7o, p<0.001) at OI45o/OA20o target but no difference in RI (p=0.929). At OI40o/OA30o target, experienced staffs positioned cups in more RI (43.7o± 1.5o vs 42.7o± 1.4o, p=0.001) and RA (18.2o± 2.9o vs 14.3o± 3.2o, p<0.001). Reducing OI by 5° and increasing OA by 10° resulted in 2°- 3° less RI and 4°- 5° more RA.
Conclusion: Android smartphone with single application was more accurate in acetabular cup positioning than iPhones with dual applications at OI45o/OA20o target but indifferent at OI40o/OA30o target.


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Prasopchoke, . N. (2022). Accuracy of Acetabular Cup Positioning by Using Smartphone: Comparison between Two Program Applications and Operating System. Lampang Medical Journal, 35(2), 68–79. Retrieved from
Original Article


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