Finger Tendon Travel Associated with Sequential Trigger Nail Gun Use

Abstract

OCCUPATIONAL APPLICATIONS This article reports a method for assessing finger tendon motion associated with the use of a sequential actuation trigger pneumatic nail gun. The two-stage actuation process of the sequential actuation trigger reduces risk of nail puncture injury from unintended nail discharge (relative to the higher risk of the contact actuation trigger). However, widespread adoption of the sequential actuation trigger nail gun throughout the construction industry has been hindered by beliefs about productivity and musculoskeletal concerns about the repetitive trigger actuation and finger motion for each nail fired. Though existing guidelines for finger tendon travel exposure are not well established, predictions derived with the present method combined with productivity standards suggest insufficient evidence to contradict the safety-based recommendation to adopt the sequential actuation trigger trigger.

TECHNICAL ABSTRACT Background: Pneumatic nail guns used in wood framing are equipped with one of two triggering mechanisms. Sequential actuation triggers have been shown to be a safer alternative to contact actuation triggers because they reduce traumatic injury risk. However, the sequential actuation trigger must be depressed for each individual nail fired as opposed to the contact actuation trigger, which allows the trigger to be held depressed as nails are fired repeatedly by bumping the safety tip against the workpiece. As such, concerns have been raised about risks for cumulative trauma injury, and reduced productivity, due to repetitive finger motion with the sequential actuation trigger. Purpose: This study developed a method to predict cumulative finger flexor tendon travel associated with the sequential actuation trigger nail gun from finger joint kinematics measured in the trigger actuation and productivity standards for wood-frame construction tasks. Methods: Finger motions were measured from six users wearing an instrumented electrogoniometer glove in a simulation of two common framing tasks—wall building and flat nailing of material. Flexor tendon travel was calculated from the ensemble average kinematics for an individual nail fired. Results: Finger flexor tendon travel was attributable mostly to proximal interphalangeal and distal interphalangeal joint motion. Tendon travel per nail fired appeared to be slightly greater for a wall-building task than a flat nailing task. The present study data, in combination with construction industry productivity standards, suggest that a high-production workday would be associated with less than 60 m/day cumulative tendon travel per worker (based on 1700 trigger presses/day). Conclusion and Applications: These results suggest that exposure to finger tendon travel from sequential actuation trigger nail gun use may be below levels that have been previously associated with high musculoskeletal disorder risk.

KEYWORDS:

• Nail gun
• trigger
• repetitive motion
• finger tendon

Acknowledgments

This article not subject to US copyright law. Received February 2011Accepted October 2012