The Association Between Annular Pulley Morphology and Maximal Fingertip Force

Area of Science:

• Orthopedics
• Biomechanics
• Sports Medicine

Background:

• The digital pulley system is crucial for finger flexion, with A2 and A4 pulleys being biomechanically critical.
• Injury to these pulleys can lead to tendon bowstringing and impaired grip.
• Tendon-bone distance (TBD) is a common diagnostic measure for pulley injury, often using a 2 mm threshold, but this may not account for adaptive remodeling.

Purpose of the Study:

• To quantify pulley morphology in a diverse sample population.
• To investigate the potential for structural adaptation in pulley morphology.
• To test the hypothesis that pulley morphology correlates with climbing experience and force production.

Main Methods:

• Ultrasound assessment of A2 and A4 pulley TBD, pulley thickness, flexor tendon thickness, and volar plate thickness in 56 climbers and 18 controls.
• Measurement of maximal voluntary contraction (MVC).
• Analysis using linear mixed-effects models to correlate morphology, MVC, and climbing status.

Main Results:

• TBD exceeded 2.0 mm in 7.2% of fingers at A2 and 15.3% at A4.
• Increased MVC correlated with increased A2 TBD and A2/A4 pulley thickness.
• Climber status was associated with increased distal interphalangeal volar plate thickness.

Conclusions:

• Fingertip force production is associated with annular pulley morphology, supporting use-dependent adaptation.
• Observed structural changes align with mechanical loading demands.
• Further research into patient-specific diagnostic cutoffs is recommended to avoid overdiagnosis.