Finger joint motion generated by individual extrinsic muscles: A cadaveric study

Ashish D Nimbarte,Zong-Ming Li,Rodrigo Kaz

doi:10.1186/1749-799x-3-27

Ashish D Nimbarte, Zong-Ming Li + Show 1 more

Open Access

https://doi.org/10.1186/1749-799x-3-27

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Abstract

BackgroundOur understanding of finger functionality associated with the specific muscle is mostly based on the functional anatomy, and the exact motion effect associated with an individual muscle is still unknown. The purpose of this study was to examine phalangeal joints motion of the index finger generated by each extrinsic muscle.MethodsTen (6 female and 4 male) fresh-frozen cadaveric hands (age 55.2 ± 5.6 years) were minimally dissected to establish baseball sutures at the musculotendinous junctions of the index finger extrinsic muscles. Each tendon was loaded to 10% of its force potential and the motion generated at the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints was simultaneously recorded using a marker-based motion capture system.ResultsThe flexor digitorum profundus (FDP) generated average flexion of 19.7, 41.8, and 29.4 degrees at the MCP, PIP, and DIP joints, respectively. The flexor digitorum superficialis (FDS) generated average flexion of 24.8 and 47.9 degrees at the MCP and PIP joints, respectively, and no motion at the DIP joints. The extensor digitorum communis (EDC) and extensor indicis proprius (EIP) generated average extension of 18.3, 15.2, 4.0 degrees and 15.4, 13.2, 3.7 degrees at the MCP, PIP and DIP joints, respectively. The FDP generated simultaneous motion at the PIP and DIP joints. However, the motion generated by the FDP and FDS, at the MCP joint lagged the motion generated at the PIP joint. The EDC and EIP generated simultaneous motion at the MCP and PIP joints.ConclusionThe results of this study provide novel insights into the kinematic role of individual extrinsic muscles.

Highlights

Our understanding of finger functionality associated with the specific muscle is mostly based on the functional anatomy, and the exact motion effect associated with an individual muscle is still unknown
The proximal interphalangeal (PIP) joint flexion positions at the 2.5%, 5%, and 7.5% forces were 82.4 (± 19.5), 87.2 (± 19.2), and 89.7 (± 18.1) degrees, respectively, representing 78.2%, 89.8%, and 95.8% of the total range of FtFhiinegaiurl rjroeeins2pteacntgivleesm(daexgimreuems) fgoernceeraptoetdenatiathlse MCP, PIP, and distal interphalangeal (DIP) joints by the individual extrinsic muscles when loaded to 10% of Final joint angles generated at the MCP, PIP, and DIP joints by the individual extrinsic muscles when loaded to 10% of their respective maximum force potentials
T1F0ihg%euroraefntg3heesirorfemspoeticotnive(dmegarxeimesu)mgefnoerrcaetepdotaetntthiaelsMCP, PIP, and DIP joints by the individual extrinsic muscles when loaded to The ranges of motion generated at the MCP, PIP, and DIP joints by the individual extrinsic muscles when loaded to 10% of their respective maximum force potentials

Summary

Introduction

Our understanding of finger functionality associated with the specific muscle is mostly based on the functional anatomy, and the exact motion effect associated with an individual muscle is still unknown. The purpose of this study was to examine phalangeal joints motion of the index finger generated by each extrinsic muscle. The kinetics and the kinematics of the index finger have been studied extensively because of its vital role in numerous manual tasks. A series of grasping, pinching, and gripping tasks require coordinated flexion-extension motion by the index finger joints. A set of extrinsic and intrinsic muscles contribute collectively to achieve the precise force and motion essential for the dexterous finger maneuvers. Natural finger flexion and extension is achieved by linearly coupled motion among the metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints [1,2]. A combined activation of the FDP and FDS using a biomechanical model demonstrated concurrent flexion at the MCP, PIP, and DIP joints (page number not for citation purposes). The in-vivo and in-vitro studies evaluating the fingertip force production [4,5] and grip strength [6] during maximal and submaximal exertions reported a high contribution from the extrinsic flexors and the intrinsic muscles, and a minimal contribution from the extrinsic extensors

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