Accuracy of a New Digital Templating Method for Total Hip Arthroplasty Using Picture Archiving and Communication System (PACS) and iPhone Technology: Comparison With Acetate Templating on Digital Radiography

Preoperative templating for total hip arthroplasty (THA) on digital radiography can be achieved using templating software or hybrid methods (acetate templates overlaid on digital images). No studies have examined templating with a mobile phone. We evaluated the accuracy and reproducibility of a new digital templating method using the picture archiving and communication system (PACS) and iPhone, compared with the hybrid method for cementless THA. A total of 113 hip radiographs were retrospectively templated by three observers. For the digital method, a circle was drawn on the acetabulum using PACS to represent the cup. The photograph of the computer screen was taken with an iPhone and imported into the Keynote presentation software. The femoral stem was then templated with transparent digital templates, which had been digitized from acetate templates. For the hybrid method, an acetate template was placed over the onscreen digital radiographs. Templated results were compared with the actual components used. The digital method was more accurate than the hybrid method to predict ±1 size of femoral stem [93.8% (106 hips) vs 84.1% (95 hips), P = .032] and offset [90.3% (102 hips) vs 75.2% (85 hips), P = .004)]. The accuracies of digital and hybrid techniques were comparable with predict ±1 size for acetabular cup [92.9% (105 hips) vs 89.4% (101 hips), P = .483] and neck length [98.2% (111 hips) vs 96.5% (109 hips), P = .683]. Both techniques had substantial to almost perfect agreement for intraobserver and interobserver reliability. Digital templating using PACS and iPhone is accurate and reproducible for predicting implant size of cementless THA.