scholarly journals Comprehending Optimality of Finger Flexor Tendon Pulley System using Computational Analysis

2021 ◽  
Author(s):  
Vitthal Khatik ◽  
Shyam Sunder Nishad ◽  
Anupam Saxena
Keyword(s):  
Rigid Body ◽  
Parametric Study ◽  
Computational Analysis ◽  
Flexor Tendon ◽  
Pulley System ◽  
Reconstruction Surgery ◽  
Tendon Tension ◽  
Insight Into ◽  
Body Method ◽  
High Range

Abstract It is rare that existing prosthetic/orthotic designs are based on kinetostatics of a biological finger, especially its tendon- pulley system (TPS). Whether a biological TPS is optimal for use as a reference, say for design purposes, and if so in what sense, is also relatively unknown. We expect an optimal TPS to yield high range of flexion while operating with lower tendon tension, bowstringing, and pulley stresses. To gain insight into the TPS designs, we present a parametric study which is then used to determine optimal TPS configurations for the flexor mechanism. A compliant, flexure-based computational model is developed and simulated using the pseudo rigid body method, with various combinations of pulley/tendon attachment point locations, pulley heights, and widths. Results suggest that three distinct types of TPS configurations corresponding to single stiff pulley, or two stiff pulleys, or one stiff and one flexible-inextensible pulley per phalange can be optimal. For a TPS configuration similar to a biological one, the distal pulleys on the proximal and intermediate phalanges need to be like flexible-inextensible string loops that effectively model the behavior of joint and cruciate pulleys. We reckon that a biological flexor TPS may have evolved to maximize flexion range with minimum possible actuation tension, bowstringing and pulley stress. Our findings may be useful in not only developing efficient hand devices, but also in improving TPS reconstruction surgery procedures.

scholarly journals Closed-form time derivatives of the equations of motion of rigid body systems

2021 ◽  
Author(s):  
Andreas Müller ◽  
Shivesh Kumar
Keyword(s):  
Rigid Body ◽  
Closed Form ◽  
Multibody Systems ◽  
Equations Of Motion ◽  
Alternative Formulation ◽  
Dynamics Of Rigid Body ◽  
Control Forces ◽  
And Control ◽  
Derivatives Of ◽  
Insight Into

AbstractDerivatives of equations of motion (EOM) describing the dynamics of rigid body systems are becoming increasingly relevant for the robotics community and find many applications in design and control of robotic systems. Controlling robots, and multibody systems comprising elastic components in particular, not only requires smooth trajectories but also the time derivatives of the control forces/torques, hence of the EOM. This paper presents the time derivatives of the EOM in closed form up to second-order as an alternative formulation to the existing recursive algorithms for this purpose, which provides a direct insight into the structure of the derivatives. The Lie group formulation for rigid body systems is used giving rise to very compact and easily parameterized equations.

Predictors of outcome after primary flexor tendon repair in zone 1, 2 and 3

2016 ◽  
Vol 41 (8) ◽  
pp. 793-801 ◽  
Author(s):  
I. Z. Rigo ◽  
M. Røkkum
Keyword(s):  
Flexor Tendon ◽  
Linear Regression Analysis ◽  
Tendon Repair ◽  
Tendon Sheath ◽  
Multiple Linear Regression Analysis ◽  
Level Of Evidence ◽  
Pulley System ◽  
Skeletal Injury ◽  
Active Mobilization

We retrospectively reviewed the outcomes of flexor tendon repairs in zones 1, 2 and 3 in 356 fingers in 291 patients between 2005 and 2010. The mean (standard deviation) active ranges of motion of two interphalangeal joints of the fingers were 98° (40) and 114° (45) at 8 weeks postoperatively and at the last follow-up (mean 7 months, range 3–98), respectively. Using the Strickland criteria, ‘excellent’ or ‘good’ function was obtained in 95 (30%) out of 322 fingers at 8 weeks and 107 (48%) out of 225 fingers at the last follow-up. A total of 48 (13%) fingers required reoperation because of rupture, adhesion, contracture or other complications. The prevalence of rupture was 4%. We carried out multiple linear regression analysis to identify the predictors of the active digital motion. The following variables were found as negative predictors: age; smoking; injury localization between subzones 1C and 2C; injury to the little finger; the extent of soft tissue damage; concomitant skeletal injury; delay to surgery; use of a 2-strand Kessler repair technique; attempted suture or preservation of the tendon sheath–pulley system; and resecting or leaving the concomitant superficial flexor tendon cuts untreated. Analysing the 8 weeks results of tendon repairs in zones 1 and 2, early active mobilization was found to be superior to Kleinert’s regime. Level of evidence: III

scholarly journals Polyacrylamide Bead Sensors for in vivo Quantification of Cell-Scale Stress in Zebrafish Development

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
N. Träber ◽  
K. Uhlmann ◽  
S. Girardo ◽  
G. Kesavan ◽  
K. Wagner ◽  
...  
Keyword(s):  
Computational Analysis ◽  
Tissue Level ◽  
Quantitative Investigation ◽  
Pulsatile Pressure ◽  
Spatio Temporal ◽  
Stress Sensing ◽  
Living Organisms ◽  
Insight Into

AbstractMechanical stress exerted and experienced by cells during tissue morphogenesis and organ formation plays an important role in embryonic development. While techniques to quantify mechanical stresses in vitro are available, few methods exist for studying stresses in living organisms. Here, we describe and characterize cell-like polyacrylamide (PAAm) bead sensors with well-defined elastic properties and size for in vivo quantification of cell-scale stresses. The beads were injected into developing zebrafish embryos and their deformations were computationally analyzed to delineate spatio-temporal local acting stresses. With this computational analysis-based cell-scale stress sensing (COMPAX) we are able to detect pulsatile pressure propagation in the developing neural rod potentially originating from polarized midline cell divisions and continuous tissue flow. COMPAX is expected to provide novel spatio-temporal insight into developmental processes at the local tissue level and to facilitate quantitative investigation and a better understanding of morphogenetic processes.

The Direct Midlateral Approach with Lateral Enlargement of the Pulley System for Repair of Flexor Tendons in Fingers

1996 ◽  
Vol 21 (4) ◽  
pp. 463-468 ◽  
Author(s):  
A. MESSINA ◽  
J. C. MESSINA
Keyword(s):  
Flexor Tendon ◽  
Skin Flap ◽  
Tendon Repair ◽  
Tendon Sheath ◽  
Flexor Tendon Repair ◽  
Anterior Compartment ◽  
Pulley System ◽  
Neurovascular Pedicle ◽  
Anchoring System ◽  
Palmar Skin

The direct midlateral approach and the lateral enlarging procedure of the pulley system have been utilized in our service since 1972. The incision runs directly behind the neurovascular pedicle, which is left in the palmar skin flap of the anterior compartment of the finger, in order to ensure its blood supply and sensibility. The transverse digital lamina of Landsmeer’s skin anchoring system and Cleland’s ligament are preserved and are used to perform a lateral enlargement of the pulleys after tendon repair. The technique allows wide surgical exposure of the digital fibro-osseous tunnel, enlargement and reconstruction of the pulley system and tendon sheath, flexor tendon repair (using the technique of choice) and reduces postoperative impingement in zone 2.

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