Utilization of 3-dimensional scanner technology to measure circumference and volume of limbs in patients bitten by venomous snakes.

Introduction: The objective of this study was to compare limb circumference measurements between a three-dimensional scanner and a measuring tape.

Methods: Patients older than 18 years, who were bitten by a green pit viper and visited the emergency department between 1 October and 20 December, 2019 were included. Two physicians measured the circumference of a bitten limb and a contralateral unaffected limb twice using both a measuring tape and a three-dimensional scanner. Each patient was measured at the first emergency department visit and again at 24 h, 48 h, and 72 h post-snakebite. There were three points of measurement on both limbs.

Results: There were 408 anatomical locations from 17 patients for measurement. The three-dimensional scanner and the measuring tape demonstrated a very high correlation (r-squared >0.940, P value <0.001) in measuring limb circumferences. Bland Altman plots also demonstrated the two methods measured limb circumferences with similar results with mean differences <1 cm. Intraclass correlation coefficient between the two methods was greater than 0.8 in every site for the lower limbs, but for the upper limbs, most sites had a poor agreement (ranges: 0.073-0.633). For limb volume measurement, the three-dimensional scanner provided excellent and moderate inter and intrarater reliabilities for the lower and upper limbs, respectively.

Discussion: The three-dimensional scanner could be reliably used to assess limb circumference with a strong correlation and with a relatively small error compared with the conventional method. Pictures from the scan can also be constructed to calculate limb volume that could have potential for other clinical purposes such as in evaluating antivenom response for limb swelling.

Conclusions: Circumferences from the three-dimensional scanner were comparable to those from the measuring tape, especially for the lower limbs, and the three-dimensional scanner demonstrated an added value for calculating limb volume.