Influence of Instrument Handle Design on Ergonomic Strain and Clinical Performance in Clinicians with and without Carpal Tunnel Syndrome

Abstract

Background: Musculoskeletal disorders (MSDs) are among the leading causes of disability worldwide, and carpal tunnel syndrome (CTS) is one of the most prevalent conditions in professionals who perform repetitive, high-precision tasks with handheld tools. While adaptive instrument handle designs can reduce ergonomic strain, their specific effects in individuals with CTS vs. their healthy counterparts have not been evaluated.

Aims: To employ periodontal hand instrumentation by dental hygienists as a clinical model to investigate the effects of a novel adaptive hand instrument design on ergonomic outcomes in clinicians with and without carpal tunnel syndrome, with the objective of advancing strategies for the prevention and mitigation of repetitive strain injuries.

Methods: Forty-eight clinicians (24 healthy, 24 with physician-diagnosed CTS) each performed a separate, standardized instrumentation task using two curettes: one a rigid silicone tool and the other an adaptive silicone over stainless steel instrument. Surface electromyography mapped muscle activity in hand and forearm muscles, while ultrathin force sensors measured thumb and forefinger grip force. Visual analogue scales recorded discomfort and fatigue, grasp correctness was scored by means of a 7-point scale, and task completion was quantified using ImageJ software. All data was analyzed using a two-way mixed ANOVA followed by Bonferroni's multiple comparisons testing (p<0.05).

Results: Clinicians with CTS experienced more than twice the levels of discomfort (204%), fatigue (212%), and muscle workload (208%) compared with healthy clinicians (p < 0.0001). They also applied an approximately one-third greater grip force during instrumentation (p < 0.0001). The adaptive handle design significantly improved all outcomes related to strain in both experimental groups (p<0.0001). It significantly reduced muscle work by approximately 38% in clinicians with CTS and by 51% in healthy clinicians (p<0.0001). A similar but smaller trend was observed for grasp correctness (p=0.045). Deposit removal did not significantly differ between groups or instruments, averaging >93% task completion.

Conclusion: Individuals with CTS exhibited altered instrumentation biomechanics, including increased muscle work, grip force, discomfort, and fatigue, despite comparable task performance to healthy controls. An adaptive handle design significantly improved ergonomic outcomes in both groups, underscoring its potential to reduce musculoskeletal disorder risk and reduce strain in professions requiring repetitive, high-precision hand movements.