Definition and measurement of functional first web space: A scoping review

The first web space of hands has been understood to be important in daily activities involving the motions of cylindrical grasp and pinch. However, surgical and rehabilitation decision-making based on first web deficiency is challenging without clear definitions of function. This study aimed to evaluate the methods used to measure first web space and synthesize the evidence on its functional definition in children up to 18 years old.

This review followed Arksey and O'Malley's six-stage framework operationalized by the Joanna Briggs Institute (JBI) methodology for conducting a scoping review. In conjunction with a medical librarian, 4440 term combinations were searched on MEDLINE from inception until January 2023. Title/abstract and full-text screening processes were conducted, followed by charting, collating, and summarizing included articles by two independent reviewers.

Of 162 studies screened, 20 studies were included. The first web space was most commonly measured in palmar abduction (50%) of the carpometacarpal angle (45%) radiographically (30%). Systematic methods were rarely used (5%) to evaluate activity and participation function of first web limitations. Definition of a cutoff angle or first-web span that represented sufficient functional outcome was difficult to synthesize due to a lack of standard measurement methods.

While the first web function was quantified in the studies, these values are problematic due to inconsistent measurement methods. A standardized assessment of first web space impairment and its relationship with activity and participation function is clinically significant for evaluating the need and meaningful outcomes of surgical and therapy interventions in children.