Middle and ring fingers are more exposed to pulley rupture than index and little during sport-climbing: a biomechanical explanation.
BACKGROUND
Finger pulley injury is a common incident observed during sport-climbing. The total rupture of one or several pulleys is highly debilitating and requires surgical reconstruction and/or rehabilitation programs. Literature reports show that fingers are not equally exposed to this injury. The ring and middle fingers are usually injured while the index and little fingers are less exposed. The objective of this study was to determine the biomechanical factors leading to the enhanced exposure of ring and middle finger pulleys.


METHODS
Eight subjects were required to exert maximal four-finger force in a specific sport-climbing finger posture. External fingertip forces and finger joint postures were used as input data of a specifically developed biomechanical model of the four fingers (i.e., index, middle, ring and little). This model was based on classical Newton static laws and used an optimization process to quantify the flexor tendon tensions and the pulley forces in each finger. Passive participation of ligaments was also considered into mechanical equations.


RESULTS
Results showed that two main factors could explain the enhanced exposure of ring and middle fingers. Firstly, the fingertip force intensities applied by these two fingers were higher than those observed for the index and little fingers. Secondly, results show that the pulley forces of the ring and middle fingers were close to their rupture thresholds, while it was not the case for the two other fingers. This could be explained by a specific localisation of the finger pulleys of the ring and middle fingers leading to enhanced pulley forces.


CONCLUSIONS
These results are relevant and could help clinicians to understand finger pulley pathologies and adapt the surgical interventions to reconstruct the fingers pulleys.
Vigouroux
Laurent
L
Movement and Perception Laboratory, CNRS UMR 6152, University of the Mediterranean, Faculte des Sciences du Sport, Case postale 910, 163, avenue de Luminy, 13288 Marseille, France. laurent.vigouroux@univmed.fr
Quaine
Franck
F
Paclet
Florent
F
Colloud
Floren
F
Moutet
François
F
D000328:Adult; D001696:Biomechanical Phenomena / Q000379:methods*; D003198:Computer Simulation; D005383:Finger Injuries / Q000503:physiopathology*; D005385:Fingers / Q000503:physiopathology*; D018737:Hand Strength; D006801:Humans; D008297:Male; D008954:Models, Biological; D009051:Mountaineering / Q000293:injuries*; D012421:Rupture / Q000503:physiopathology; D013708:Tendon Injuries / Q000503:physiopathology*