Hand Biomechanics Research Articles

손가락 하중과 신경명령 사이의 다중 관계에 관한 연구

During multi-finger force-production tasks, finger forces can be generated without the involvement of neural commands which called the enslaving effect. In addition, the force produced by a given finger in a multi-finger task is smaller than the force generated by this finger in its single-finger maximal force-production task which called the force deficit effect. The purposes of this study were to represent quantitatively both the enslaving effect and the force deficit effect and propose the relationship between the finger force and the neural command by the experimental results. Seven subjects were instructed to press one, two, three and four fingers on the finger sensors as hard as possible acting in parallel in all possible combinations. The results confirmed that the finger forces were generated without the neural commands up to 20% of their maximal forces as the enslaving effect. In addition, the force deficit effect increased with the number of fingers involved. The mathematical model proposed in this paper could explicitly describe the two effects of finger interaction. The present results could be useful information to understand the basic neuro-muscular mechanism in hand biomechanics and the fundamentals of intelligent hand robots.

The unstable radiocarpal joint in rheumatoid arthritis

The inflammation of the wrist occurs very early in Rheumatoid arthritis. In cases of wrist deviation the biomechanics of the hole hand are affected. Carpal collapse will severely influence the range of motion (ROM) of the fingers. Operative techniques of how to maintain hand function are discussed. There are different procedures available - partial arthrodesis, arthrodesis and arthroplasty.

The Role of the Fifth Metacarpophalangeal Joint in the Recovery of the Burnt Hand - is it Great or Small?

Clinical observation has shown that despite complying with text book regimes of exercises and splinting the outcome for some patients with partial thickness burns is extension contracture of the Fifth Metacarpophalangeal Joint (5th MCP joint). This observation led to a review of the architecture and biomechanics of the hand in order to consider what could improve hand function following recovery of a thermal injury. This paper reviews the architecture and biomechanics of the burnt hand and suggests that in the short term, the 5th MCP joint plays a central role in returning the hand to maximum function. With this in mind a modified form of treatment has been adopted focusing attention on the 5th MCP joint and related structures.

Wrist ligament strain during external fixation: a cadaveric study.

The purpose of this study was to evaluate the change in strain (elongation) that occurs in 2 extrinsic ligaments of the wrist (volar radioscaphocapitate and dorsal radiotriquetral) as the wrist is sequentially distracted with an external fixator. Six fresh cadaver specimens were dissected to expose the dorsal radiotriquetral and volar radioscaphocapitate ligaments. A differential variable reluctance transducer strain gauge was applied to both ligaments and the wrist was serially distracted in increments of 5 mm with an Agee WristJack (Hand Biomechanics Laboratory, Sacramento, CA). The distraction increments were measured on the WristJack. X-rays were obtained at each level of distraction. At 10 mm of WristJack distraction, the strain in both the volar radioscaphocapitate and dorsal radiotriquetral ligaments increased to greater than 20%. An increase to a 0.63 carpal height index resulted in an increase in strain of 20%. This increased strain may contribute to wrist stiffness.

Intra-articular fractures of the distal end of the radius treated with an adjustable fixator system

Twenty-five wrists with comminuted, displaced, intra-articular fractures of the distal radius were prospectively treated with an adjustable external fixator for an average of 51 days. Twenty fractures (80% [20 of 25] were available for follow-up) in 16 adults (mean age, 34 years) were treated with the Wrist Jack external fixator system (Hand Biomechanics Lab, Sacramento, CA) and evaluated at a mean follow-up period of 25 months. Ten patients (12 fractures) sustained high-energy trauma with multiple injuries, while 6 patients (8 fractures) sustained isolated distal radius fractures. Percutaneous pins supplemented the fixation in 6 fractures. All fractures were reduced to restore articular congruity to within 1 mm. At follow-up, 5% were excellent, 75% good, 20% fair, and none as poor using the demerit point system of Gartland and Werley as modified by Sarmiento. Grip strength averaged 80% of the unaffected limb. Seventeen of the 20 fractures showed some evidence of articular incongruity at follow-up evaluation. Restoration of palmar tilt, radial inclination, radial length, and range of motion were at acceptable values. Subjective analysis confirmed 85% of the patients to have only occasional pain or none at all and 15% to have some pain with weakness or limitation of motion. Two patients required additional surgery: 1 underwent a Darrach procedure and the other a tendon transfer for a rupture of the extensor pollicis longus tendon. Results suggest that an external fixator system provides an additional alternative to the surgical armamentarium for an otherwise difficult fracture fixation problem.

A linear force-summing hand dynamometer independent of point of application

Theort, design and construction details are presented for a versatile strain gauge hand dynamometer. What distinguishes this instrument is that sensitivity is completely independent of the location. Force is applied so it is capable of linearly summing forces exerted at multiple locations along the length of the active area of the dynamometer. In addition to including the basic principles of this transducer, a template for the instrument and an accompanying spread sheet is provided for computing transducer response characteristics for instruments of arbitrary size, including sensitivity and force range, depending on particular measurement requirements. Variations of this dynamometer were constructed and used for measuring grip and pinch strength, as well as for measuring submaximal exertions produced during manual activities and tasks. Because this dynamometer is compact and rigid, one of suitable dimensions may be substituted as a handle for tools or objects handled during work for directly measuring applied exertions and grip force. Examples of practical applications of this instrument are given for hand biomechanics, hand tool ergonomics, and clinical evaluations.

Advances in hand biomechanics simulation

Advances in hand biomechanics simulation

A kinematic model of the flexor tendons of the hand

The multi-joint model is a kinematic simulation of the long flexor tendons of the fingers. The tendons modeled are the flexor pollicis longus, the flexor digitorum profundus, and the flexor digitorum superficialis. The simulated tendons are displayed on an Evans and Sutherland PS330 color graphics terminal attached to a display of articulated bones of the hand. As a user changes the position of the joints of the simulated hand, the simulation displays the new tendon path and the excursion of the tendon for the new position of the hand. The multi-joint model is one component of a comprehensive model for use in a hand biomechanics computer workstation.

A hand biomechanics workstation

Interactive graphics for hand surgery was used to apply mathematical modeling and describe the kinematics of the hand and its resultant effect on hand function. Dynamic high resolution displays and three-dimensional images were tailored for use with a specific patients' hand and a new and powerful design and analysis tool produced. Methods were developed to portray kinematic information such as muscle excursion and effective moment arm and extended to yield dynamic information such as torque and work. This prototype workstation has been developed in concert with leading orthopedic surgeons and therapists.

Hand Function, Biomechanics and Disability

A functional assessment and biomechanical analysis of certain joints of the fingers are presented. The functional assessment has been carried out on rheumatoid arthritis patients who were assessed pre- and post-surgically after metacarpophalangeal joint replacement. Twenty normal subjects have been assessed in the biomechanical tests as they carried out two activities, tap turning and jar closing. The load actions applied by the index finger were measured by a six component transducer and the three-dimensional coordinates of the joint centres were derived from external markers attached to the skin of the index finger. From this information the forces and components of moment to be transmitted at the proximal interphalangeal and metacarpophalangeal joints have been calculated.