title: Mechanical properties vary for different regions of the finger extensor apparatus.
abstract: The extensor apparatus, an aponeurosis that covers the dorsal side of each finger, transmits force from a number of musculotendons to the phalanges. Multiple tendons integrate directly into the structure at different sites and the extensor apparatus attaches to the phalanges at multiple points. Thus, prediction of the force distribution within the extensor apparatus, or hood, and the transmission to the phalanges is challenging, especially as knowledge of the underlying mechanical properties of the tissue is limited. We undertook quantification of some of these properties through material testing of cadaver specimens. We punched samples at specified locations from 19 extensor hood specimens. Material testing was performed to failure for each sample with a custom material testing device. Testing revealed significant differences in ultimate load, ultimate strain, thickness, and tangent modulus along the length of the extensor hood. Specifically, thickness, ultimate load, and ultimate strain were greater in the more proximal sections of the extensor hood, while the tangent modulus was greater in the more distal sections. The variations in mechanical properties within the hood may impact prediction of force transmission and, thus, should be considered when modeling the action of the extensor apparatus. Across the extensor hood, tangent modulus values were substantially smaller than values reported for other soft tissues, such as the Achilles tendon and knee ligaments, while ultimate strains were much greater. Thus, the tissue in the extensor apparatus seems to have greater elasticity, which should be modeled accordingly.
authors.affiliation: Department of Biomedical Engineering, Illinois Institute of Technology, Wishnick Hall, Suite 314, 3255 S Dearborn St, Chicago, IL 60616, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: Qian
authors.affiliation: Department of Biomedical Engineering, Illinois Institute of Technology, Wishnick Hall, Suite 314, 3255 S Dearborn St, Chicago, IL 60616, United States.
authors.forename: Kay
authors.initials: K
authors.lastname: Traylor
authors.affiliation: Department of Biomedical Engineering, Catholic University of America, Washington, DC 20064, United States; Center for Applied Biomechanics and Rehabilitation Research, National Rehabilitation Hospital, Washington, DC 20010, United States.
authors.forename: Sang Wook
authors.initials: SW
authors.lastname: Lee
authors.affiliation: Department of Bioengineering, and Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT 84112, United States.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Ellis
authors.affiliation: Department of Bioengineering, and Scientific Computing and Imaging Institute, University of Utah, Salt Lake City, UT 84112, United States; Department of Orthopedics, University of Utah, Salt Lake City, UT 84108, United States.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Weiss
authors.affiliation: Department of Biomedical Engineering, Illinois Institute of Technology, Wishnick Hall, Suite 314, 3255 S Dearborn St, Chicago, IL 60616, United States; Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, IL 60611, United States. Electronic address: d-kamper@northwestern.edu.
authors.forename: Derek
authors.initials: D
authors.lastname: Kamper
mesh_terms: D001696:Biomechanical Phenomena; D002102:Cadaver; D005385:Fingers; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D055595:Mechanical Phenomena; D013314:Stress, Mechanical; D013710:Tendons; D013718:Tensile Strength
keywords: Extensor apparatus; Material properties; Soft tissue mechanics; Tensile