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[USE OF SMARTPHONE IN ACETABULAR COMPONENT ANGLE MEASUREMENT DURING TOTAL HIP ARTHROPLASTY].

OBJECTIVE
To evaluate the accuracy of using smartphone to measure the angle of acetabular component in total hip arthroplasty (THA).


METHODS
Between June 2012 and September 2015, the acetabular abduction and anteversion angles were measured in 50 patients undergoing THA. There were 24 males and 26 females, aged 37 to 83 years (mean, 71 years). The left hip was involved in 22 cases and the right hip in 28 cases. Of 50 patients, 34 suffered from fracture of the femoral neck, and 16 suffered from avascular necrosis of the femoral head. Acetabular dysplasia was excluded in all cases. A smartphone was used to measure the acetabular abduction and anteversion angles during operation; standard Picture Archiving and Communication Systems (PACS) was used to measured the acetabular abduction and anteversion angles on the X-ray film at 1 week after operation. It was defined as positive that the component angle values by PACS measurement were greater than those by the smartphone measurement, whereas as negative. The two measurement methods were compared, and intra-observer variability was assessed by analyzing the intraclass correlation coefficient (ICC), the Mann-Whitney U-test was used to analyze difference.


RESULTS
The ICC was 0.84 in the acetabular component angles by smartphone and PACS measurement methods. The acetabular component abduction angle was (44.02±1.33)° and the anteversion angle was (17.62±2.20)° by smartphone measurement. The acetabular component abduction angle was (44.74±4.05)° and the anteversion angle was (17.22±5.57)° by PACS measurement. There was no significant difference between two measurement methods (Z=-1.977, P=0.482; Z=-0.368, P=0.713). The acetabular component angle was in the safe zone in 44 cases; and the acetabular component anteversion angle was beyond safe range of 1 to 5°, and the abduction angle was beyond safe range of 1 to 3° in 6 cases. Intra-measurement variability was -21 to +10° for the anteversion angle and -10 to + 9° for the abduction angle, indicating that the acetabular component anteversion angle by smartphone measurement was greater than that by the PACS measurement, and the abduction angle was less than that by PACS measurement.


CONCLUSIONS
Smartphone is a convenient tool to measure the acetabular component angle in THA.