A simulating analysis of the effects of increased joint stiffness on muscle loading in a thumb

John Z. Wu, Zong Ming Li, Robert G. Cutlip, Kai Nan An

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

Background: The development of osteoarthritis (OA) in the hand results in increased joint stiffness, which in turn affects the grip strength. The goal of the present study is to theoretically analyze the muscle forces in a thumb in response to the increased joint stiffness.Methods: The thumb was modeled as a linkage system consisting of a trapezium, a metacarpal bone, a proximal and a distal phalanx. Nine muscles were included in the model: flexor pollicis longus (FPL), extensor pollicis longus (EPL), extensor pollicis brevis (EPB), abductor pollicis longus (APL), flexor pollicis brevis (FPB), abductor pollicis brevis (APB), the transverse head of the adductor pollicis (ADPt), the oblique head of the adductor pollicis (ADPo), and opponens pollicis (OPP). Numerical tests were performed using an inverse dynamic approach. The joints were prescribed to an angular motion at one degree-of-freedom (DOF) each time with all other DOFs of the joints being mechanically constrained, while the muscle forces in response to the joint motions were predicted. The normal joint stiffness was assumed to be 0.05, 0.10, and 0.15 N m/rad for interphalangeal (IP), metacarpophalangeal (MCP), and carpometacarpal (CMC) joint, respectively. The joint stiffness was assumed to increase by 50% and 100%, simulating the biomechanical consequences of OA.Results: Our simulations indicated that the increase in joint stiffness induced substantial increases in muscle forces, especially in the EPL and FPL muscles in response to IP, MCP, or CMC extension/flexion motions.Conclusions: Because the strength of the muscles in the fingers is limited, the muscles will not be able to overcome joint resistance if joint stiffness is increased to its limit due to OA. This may contribute to the reduced range of motion typically seen in OA.

Original languageEnglish (US)
Article number41
JournalBioMedical Engineering Online
Volume8
DOIs
StatePublished - Dec 6 2009

Fingerprint

Thumb
Muscle
Joints
Stiffness
Muscles
Osteoarthritis
Carpometacarpal Joints
Head
Metacarpophalangeal Joint
Metacarpal Bones
Bone
Muscle Strength
Hand Strength
Articular Range of Motion
Fingers
Hand

ASJC Scopus subject areas

  • Biomedical Engineering
  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging
  • Biomaterials

Cite this

A simulating analysis of the effects of increased joint stiffness on muscle loading in a thumb. / Wu, John Z.; Li, Zong Ming; Cutlip, Robert G.; An, Kai Nan.

In: BioMedical Engineering Online, Vol. 8, 41, 06.12.2009.

Research output: Contribution to journalArticle

Wu, John Z. ; Li, Zong Ming ; Cutlip, Robert G. ; An, Kai Nan. / A simulating analysis of the effects of increased joint stiffness on muscle loading in a thumb. In: BioMedical Engineering Online. 2009 ; Vol. 8.
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abstract = "Background: The development of osteoarthritis (OA) in the hand results in increased joint stiffness, which in turn affects the grip strength. The goal of the present study is to theoretically analyze the muscle forces in a thumb in response to the increased joint stiffness.Methods: The thumb was modeled as a linkage system consisting of a trapezium, a metacarpal bone, a proximal and a distal phalanx. Nine muscles were included in the model: flexor pollicis longus (FPL), extensor pollicis longus (EPL), extensor pollicis brevis (EPB), abductor pollicis longus (APL), flexor pollicis brevis (FPB), abductor pollicis brevis (APB), the transverse head of the adductor pollicis (ADPt), the oblique head of the adductor pollicis (ADPo), and opponens pollicis (OPP). Numerical tests were performed using an inverse dynamic approach. The joints were prescribed to an angular motion at one degree-of-freedom (DOF) each time with all other DOFs of the joints being mechanically constrained, while the muscle forces in response to the joint motions were predicted. The normal joint stiffness was assumed to be 0.05, 0.10, and 0.15 N m/rad for interphalangeal (IP), metacarpophalangeal (MCP), and carpometacarpal (CMC) joint, respectively. The joint stiffness was assumed to increase by 50{\%} and 100{\%}, simulating the biomechanical consequences of OA.Results: Our simulations indicated that the increase in joint stiffness induced substantial increases in muscle forces, especially in the EPL and FPL muscles in response to IP, MCP, or CMC extension/flexion motions.Conclusions: Because the strength of the muscles in the fingers is limited, the muscles will not be able to overcome joint resistance if joint stiffness is increased to its limit due to OA. This may contribute to the reduced range of motion typically seen in OA.",
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