title: Importance of proximal A2 and A4 pulleys to maintaining kinematics in the hand: a biomechanical study.
abstract: OBJECTIVE
  The A2 and A4 pulleys have been shown to be important in finger flexor tendon function. Other authors have suggested either reconstruction or venting of portions of these pulleys in an attempt to preserve finger function in certain clinical situations. This study examines the effects of partial incision of these pulleys on finger flexion kinematics and biomechanics.
  
  
  METHODS
  The index and ring fingers of 16 cadaveric hands were studied. The flexor digitorum profundus tendon was isolated and attached to a computer driven servo-motor. Micro-potentiometers measured flexion angles of the metacarpophalangeal, proximal inter-phalangeal and distal inter-phalangeal joints. Joint inertial torques were calculated making use of this experimental kinematic data.
  
  
  RESULTS
  Proximal 50 % incisions of either the A2 or the A4 pulleys resulted in a statistically significant decrease in overall finger motion. This effect was greatest in the proximal inter-phalangeal joint, with a decrease in joint motion, as well as an earlier time to initiation of motion. These changes in finger motion were more pronounced with A2 pulley incision than they were with A4 pulley incision, but the changes were statistically significant in either case. No significant changes in joint inertial torques were shown.
  
  
  CONCLUSIONS
  Our data provides evidence to the importance of the proximal portions of the A2 and A4 pulleys, and may support partial distal incision of these pulleys in certain clinical situations.
authors.affiliation: Department of Orthopaedic Surgery, M/C 844, University of Illinois at Chicago, 835 S. Wolcott Avenue, Chicago, IL 60612-3748 USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Chow
authors.affiliation: Department of Mechanical Engineering, University of Illinois at Chicago, 2027 Engineering Research Facility, 842 W. Taylor Street, Chicago, IL 60607 USA ; Department of Bioengineering, University of Illinois at Chicago, 2027 Engineering Research Facility, 842 W. Taylor Street, Chicago, IL 60607 USA.
authors.forename: Jon
authors.initials: J
authors.lastname: Sensinger
authors.affiliation: Department of Mechanical Engineering, University of Illinois at Chicago, 2027 Engineering Research Facility, 842 W. Taylor Street, Chicago, IL 60607 USA ; Department of Bioengineering, University of Illinois at Chicago, 2027 Engineering Research Facility, 842 W. Taylor Street, Chicago, IL 60607 USA.
authors.forename: David
authors.initials: D
authors.lastname: McNeal
authors.affiliation: Department of Orthopaedic Surgery, M/C 844, University of Illinois at Chicago, 835 S. Wolcott Avenue, Chicago, IL 60612-3748 USA.
authors.forename: Bettina
authors.initials: B
authors.lastname: Chow
authors.affiliation: Department of Orthopaedic Surgery, M/C 844, University of Illinois at Chicago, 835 S. Wolcott Avenue, Chicago, IL 60612-3748 USA ; Department of Bioengineering, University of Illinois at Chicago, 2027 Engineering Research Facility, 842 W. Taylor Street, Chicago, IL 60607 USA.
authors.forename: Farid
authors.initials: F
authors.lastname: Amirouche
authors.affiliation: Department of Orthopaedic Surgery, M/C 844, University of Illinois at Chicago, 835 S. Wolcott Avenue, Chicago, IL 60612-3748 USA ; Department of Bioengineering, University of Illinois at Chicago, 2027 Engineering Research Facility, 842 W. Taylor Street, Chicago, IL 60607 USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Gonzalez
keywords: Biomechanics; Finger; Flexor tendon; Pulley excision; Range of motion