Quantitative assessment of the tendon-pulley interface in trigger finger: a pilot feasibility study of a wearable electrical contact resistance sensor

Jhih-Fong Huang; Rajat Subhra Karmakar; Yu-Chun Lin; Jui-I Chao; Yen-Wen Lu

doi:10.1186/s13018-026-06990-2

Quantitative assessment of the tendon-pulley interface in trigger finger: a pilot feasibility study of a wearable electrical contact resistance sensor

J Orthop Surg Res. 2026 Jun 6. doi: 10.1186/s13018-026-06990-2. Online ahead of print.

Authors

Jhih-Fong Huang¹, Rajat Subhra Karmakar², Yu-Chun Lin², Jui-I Chao¹, Yen-Wen Lu^{3

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Affiliations

¹ 1Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, 300068, Taiwan.
² 2Department of Biomechatronics Engineering, National Taiwan University, Taipei, 10617, Taiwan.
³ 1Department of Biological Science and Technology, National Yang Ming Chiao Tung University, Hsinchu, 300068, Taiwan. yenwenlu@ntu.edu.tw.
⁴ 2Department of Biomechatronics Engineering, National Taiwan University, Taipei, 10617, Taiwan. yenwenlu@ntu.edu.tw.
⁵ 3Institute of Biotechnology, National Taiwan University, Taipei, 10617, Taiwan. yenwenlu@ntu.edu.tw.

PMID: 42251423
DOI: 10.1186/s13018-026-06990-2

Abstract

Background: Trigger finger (stenosing tenosynovitis) reflects abnormal tendon-pulley mechanics, primarily at the A1 pulley; however, objective assessment during functional motion remains limited in routine clinical practice. We evaluated electrical contact resistance (ECR) from a wearable tactile sensor during standardized digit motion and examined its association with symptoms.

Methods: Nine participants with Green grade II-III trigger finger were prospectively enrolled. An origami-inspired pentagon-knot graphene-paper tactile sensor measured ECR over the A1 and A2 pulleys during repeated flexion-extension cycles. A 4-week intervention program (electrical stimulation plus infrared irradiation; three sessions per week) enabled repeated measurements. ECR and patient-reported outcomes were collected at weekly Tuesday assessments, with ECR recorded immediately before and after the session (ECR_pre and ECR_post). Outcomes included pain (visual analog scale [VAS]) and triggering severity (ST), frequency (FT), and functional impact (FIT). Within-session change was defined as ΔECR_session = ECR_pre - ECR_post. Analyses used linear mixed-effects models, repeated-measures correlation (rmcorr; r_rm coefficient) and week-adjusted fixed-effects regression.

Results: Sensor placement and recording were feasible, with no adverse events. Across 27 paired weekly sessions (Weeks 1-4), ECR decreased from pre- to post-session at both pulleys (model-estimated mean ΔECR_session: A1 0.0795; A2 0.0990; both P < 0.001). A1 ECR_pre declined over Weeks 1-4 (r_rm = - 0.672; P = 0.0016). At matched weekly timepoints (N = 6; n = 24), A1 ECR_pre correlated with VAS (r_rm = 0.781; P < 0.001), FT (r_rm = 0.578; P = 0.0095), and ST (r_rm = 0.543; P = 0.0164), but not FIT (r_rm = 0.165; P = 0.50). Larger A1 ΔECR_session values were associated with greater subsequent week-to-week pain improvement (r_rm = 0.625; P = 0.0042). In a fixed-effects model adjusting for week, A1 ECR_pre independently predicted VAS (β = 29.19; P = 0.018).

Conclusions: Wearable ECR sensing was safe and feasible in this pilot study and demonstrated consistent within-session responsiveness. Clinically, motion-acquired ECR may serve as an objective adjunct for tracking session-level changes and week-to-week status with symptom scales.

Trial registration: Retrospectively registered at ChiCTR (ChiCTR2600120811 approved).

Keywords: Biomechanical monitoring; Electrical contact resistance; Tendon–pulley interface; Trigger finger; Wearable tactile sensor.