Background We developed an augmented reality (AR)-based portable navigation system in which the surgeon can view the pelvic plane and placement angle of an acetabular cup on the display of a smartphone during THA. Questions/purposes (1) Is acetabular component placement more accurate using the AR-based portable navigation system compared with the conventional freehand technique? (2) Is intraoperative measurement of placement angle more accurate when using the AR-based portable navigation system compared with a goniometer? Methods Forty-six patients were randomly assigned to undergo acetabular cup placement during THA using the AR-based portable navigation system (AR navigation group) or placement of a mechanical alignment guide (conventional group). All surgeries were performed with the patient in the lateral decubitus position. We compared the absolute value of the difference between the targeted placement angle and postoperative measured placement angle between the groups using two types of imaging (radiography and CT). Results In terms of radiographic inclination, the mean differences between the targeted placement angle and postoperative measured angle were smaller in the AR navigation group than in the conventional group for both radiographs and CT images (2.3° ± 1.4° versus 3.9° ± 2.4°, respectively; p = 0.009 and 1.9° ± 1.3° versus 3.4° ± 2.6°, respectively; p = 0.02). There were no differences in radiographic anteversion between the two groups. No complications were associated with the use of the AR-based portable navigation system. Conclusions This system yielded no differences in acetabular anteversion accuracy, and no clinically important differences in acetabular inclination. Therefore, at this time we cannot recommend this device as its costs and risks cannot be justified based on the absence of a clinically meaningful difference in cup placement accuracy. Although we detected no complications, this was a small series, and this approach adds both surgical time and pins in the ilium. Level of Evidence Level I, therapeutic study.

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Objective To overcome the difficulties of one-stage secondary alveolar bone grafting for patients with bilateral cleft lip and palate (BCLP) who have a broad alveolar cleft, the value of two-stage alveolar bone grafting was examined. Patients Three patients (2 girls and 1 boy) with BCLP were treated by two-stage alveolar bone grafting. The procedure consisted of a first-stage surgery (mean age 8 year 6 months ± 7.8 months), which consisted of alveolar bone grafting for one side of the BCLP, and second-stage surgery for the contralateral side several months later. For the postoperative assessment, radiographs of the operated site were examined. Results The average amount of implanted bone per operation and per patient was 6.8 ± 1.1 g and 13.7 ± 1.0 g, respectively. Postoperative clinical and radiographic examinations revealed that an appreciable alveolar bone ridge had formed, and there were no major complications. Conclusions Two-stage alveolar bone grafting, which makes it possible to reduce the amount of implanted bone, could be an optional surgical procedure for patients with BCLP and a broad alveolar cleft.

Two-stage alveolar bone grafting, which makes it possible to reduce the amount of implanted bone, could be an optional surgical procedure for patients with BCLP and a broad alveolar cleft.