Abstract:

Objective To clarify the feasibility of the 3D scanning volume method for distal upper limb volume measurement, and to analyze its scorer reliability and criterion-related validity.

Methods From January to March, 2022, a therapist (operator A) who had not been exposed to 3D scanning volume method and water displacement method was trained to use a handheld 3D laser scanner and a spilt cup to measure the volume of a PVC distal upper limb model. The operation time of 30 operations of each method was recorded. The learning curves of the two methods were plotted using cumulative sum (CUSUM) analysis. The curve was cut into the learning stage and the mastery stage by the vertex of peak. The times required to reach the mastery stage and the operation time of the mastery stage for the two methods were recorded. A total of 20 healthy subjects were recruited from Huashan Hospital of Fudan University. Two trained therapists (operator A and operator B) measured the bilateral distal upper limb volume using a handheld 3D laser scanner, and operator A measured the bilateral distal upper limb volume using a spilt cup.

Results The fitting learning curve of the 3D scanning volume method (R² = 0.984) reached its peak after eight times of operation; while that of the water displacement method (R² = 0.494) reached its peak after five times of operation. At mastery stage, the operator spent less time using 3D scanning volume method than using water displacement method (P < 0.05). The intraclass correlation coefficient between the two operators were both 0.979 for bilateral distal upper limb volume measure (P < 0.001). The Pearson coefficients was above 0.979 between 3D scanning volume method and water displacement method (P < 0.001).

Conclusion A therapist can master the use of the 3D scanning volume method after eight times of operation, and the operation time of 3D scanning volume method is shorter than that of water displacement method at mastery stage. The 3D scanning volume method is well reliable and valid, that can be used as an alternative to the water displacement method for distal upper limb volumetric measurement.

Key words: upper limb, volume, 3D scanning volume method, water displacement method, learning curve, measurement, reliability, validity