A novel technique for digital assessment of hand volume.

Background: Swelling is an anticipated nonspecific response following hand trauma, arthritis, infection, or surgery, which can decrease range of motion and increase pain. Approaches to quantify swelling, typically performed through hand volume measurement, are lacking in routine clinical assessments. A hand volumetry technique that is quick, inexpensive, noninvasive, and reliable is still in demand. With advances in computer imaging, new technologies are increasingly gaining attention to enable the digital assessment of hand volume as a surrogate marker of swelling.

Purpose: This study aims to develop a webcam-based method using computer vision technology for digital hand volume assessment and compare its results with those from conventional water displacement and figure-of-eight techniques to evaluate its feasibility in healthy hands.

Study design: Cross-sectional observational pilot study.

Methods: A novel algorithm was developed to process hand images captured through a webcam. Digital hand volume was computed using both palmar and lateral view area calculations. Thirty healthy participants were recruited. The volumes of their hands were measured using three methods: the proposed digital method (V_D), water displacement (V_W), and figure-of-eight taping (C_FOE). Digital volumes were compared to conventional approaches using Pearson correlation coefficients and Bland-Altman analysis.

Results: A strong correlation was observed between V_D and C_FOE (r=0.89, p<0.00001). Similarly, V_D demonstrated a significant correlation with V_W (r=0.96, p<0.00001). However, a systematic overestimation by V_D was identified and subsequently adjusted using a calibration curve derived from regression analysis, resulting in the calibrated hand volume (V_D*). Bland-Altman analysis between V_D* and V_W indicated Limits of Agreement (LOA) of ±33.6 mL, with percentage limits ranging from -9.5% to 9.3%.

Conclusions: This study demonstrates a novel approach to digital hand volume assessment. Our findings suggest that when LOA of ±9.5% is considered clinically acceptable, the digital method can be used interchangeably with water displacement volumetry in nonpathological hands.