National Science Foundation     |     Directorate for Engineering  (ENG)
Division of Chemical, Bioengineering, Environmental, & Transport Systems  (CBET)
 
CBET Research Highlights 
Notable Accomplishments from CBET Awards
 
 
5342 - Part A - Unraveling the Mechanisms of Sprains
 
Raffaella De Vita  -  Virginia Polytechnic Institute and State University

Outcome or Accomplishment:  An interdisciplinary team of researchers at Virginia Tech and Rutgers University have discovered that a decrease in stiffness and an increase in laxity in ligaments are ideal mechanical parameters for characterizing the onset of sprains in knee ligaments.  Most importantly, the results suggest that sprains may occur differently in young and old adults.  The experimental studies will ultimately be used to create novel predictive tools for the prevention and treatment of sprains.

Raffaella De Vita  Image 1
    Figure 1a and 1b.  Scanning electron microscopy of a normal (a) and mechanically damaged (b) rat medial collateral ligament.  The structure of the collagen fibrils appears to be altered in the damaged ligament (Figure 1b).
   
Credit for Images 1a and 1b:  Raffaella De Vita, Virginia Tech
 
Raffaella De Vita Image 2
    Figure 2.  Dr. Raffaella De Vita and Ph.D. candidate Albert Kwansa discussing the results of the molecular dynamics simulations. The image on the computer monitor shows an atomistic molecular model of a collagen type I microfibril unit.
 
Credit for Image 2:  Michael Diersing, Virginia Tech
 
Raffaella De Vita Image 3
    Figure 3.  Scanning electron microscopy of a novel replacement graft for knee ligaments.
 
Credit for Image 3:  Joseph W. Freeman, Rutgers University

Impact:  This research program has a significant impact in the area of engineering materials for replacement grafts and biological scaffolds (Figure 3).  It offers crucial knowledge of the structural and mechanical properties to target in developing novel replacements for ligaments.  The findings will also suggest the design of braces or stretching routines that limit strain in the knee joint thus preventing the occurrence of sprains during sport and recreational-related activities.

Explanation/background:  Sprains of the knee ligaments are among the most common orthopedic injuries.  They usually occur when the knee is forced beyond its normal range of motion, such as in a fall.  They also happen when the knee experiences an impact, such as in a car accident or during a football tackle.  These injuries can consist of a slight over-stretch, a partial tear, or a complete disruption of the ligaments.  While many investigators in biomechanics have focused on characterizing the ultimate loads and deformations of knee ligaments, little has been done to determine their damage thresholds.  This is, perhaps, due to the lack of standardized methods in biomechanics for defining and measuring the onset of damage in ligaments.  This research aims at developing and integrating new experimental, theoretical, and computational tools that can be employed to accurately characterize sprains.



CBET Research Highlight - Part B - Engineering Technical Information

5342 - Unraveling the Mechanisms of Sprains

Raffaella De Vita  -  Virginia Polytechnic Institute and State University

Background:  Sprains of the knee ligaments are among the most common orthopedic injuries.  They usually occur when the knee is forced beyond its normal range of motion, such as in a fall.  They also happen when the knee experiences an impact, such as in a car accident or during a football tackle.  These injuries can consist of a slight over-stretch, a partial tear, or a complete disruption of the ligaments.  While many investigators in biomechanics have focused on quantifying the material properties of ligaments, such as tangent modulus, tensile strength, and ultimate strain, little is known about the mechanisms that lead to sprains.  Experimental, theoretical and computational tools need to be developed to unravel the mechanical and micro-structural alterations in ligaments that initiate sprains.

Results:  - 1 -  Researchers at Virginia Tech and Rutgers University have discovered that a decrease in stiffness and increase in laxity in ligaments are ideal mechanical parameters for characterizing the onset of sprains.  They have shown that sprains quantified by these parameters are induced by two significantly different strain levels.
 
- 2 -  The breakage of collagen fibrils, which are the basic structural components of ligaments, determines the decrease in stiffness (Figure 1).  Currently, the role of collagen cross-links on the damage evolution process is being investigated by performing mechanical experiments and molecular dynamics simulations (Figure 2).

CBET Strategic Outcome Goals include:
 
- 1Discovery:  This fundamental research aims at understanding the mechanical role of the structural components of knee ligaments in sprains.  The research advances knowledge about the mechanisms that lead to sprains and, thus, has the potential to change the current prevention and treatment strategies for sprains.
 
- 2Learning:  The interdisciplinary nature of the project has allowed the faculty to train several undergraduate and graduate students to be creative and independent thinkers, who can solve problems at the intersection of science, engineering, and medicine.

Transformative Research:  The research combines state-of-the-art experimental, computational, and theoretical methods in order to provide fundamental knowledge of sprains.  New experimental protocols are used to characterize the damage evolution process in ligaments.  The findings of the mechanical experiments are then correlated to the results of microscopic analysis of the fibrillar structure of ligaments.  The molecular mechanisms that are responsible for sprains are investigated by performing molecular dynamics simulations.  The ultimate goal of the research is developing structurally based mathematical models that capture the experimental observation and molecular dynamics predictions.  The models will be employed as predictive tools for the development of grafts for ligaments and stretching routines that minimize the occurrence of sprains.

Intellectual Merit:  This word is notable because the research focuses on fundamental understanding of the mechanisms that lead to sprains, the most common orthopedic injuries.  The research findings will also contribute to uncover the damage evolution process of more complex biological tissues such as, for example, skin and arteries.

The Broader Impacts of this research include:
 
- 1Broadening Participation: The principal investigators of the project, two females and one African-American, are underrepresented in science and engineering.  Through this research, they have been able to recruit two African American graduate students, one of whom is female, and one female research specialist.  Moreover, female, African-American, and undergraduate and graduate students with disabilities have also contributed to various experimental, theoretical and computational components of the research.  The project has been extremely successful not only in recruiting but also retaining minority groups in science and engineering.
 
- 2Benfits to Society:  Several kinds of grafts are utilized for knee ligament reconstruction when complete rupture occurs.  Orthopedic surgeons most commonly use autografts, grafts harvested from the patients themselves.  The autografts are obtained from the middle-third of the patellar tendon, from one or two hamstring tendons, or from the distal portion of the iliotibial tract.  Allografts represent the other grafts of choice in knee ligament surgery.  The source material for these grafts is primarily human donor hamstring tendons, patellar tendons, and Achilles tendons.  Although xenografts, which are grafts harvested from an animal donor, and synthetic polymer grafts have been employed for ligament reconstruction, they are not recommended for reconstructive surgery due to their short-term durability and poor biocompatibility.  In recent years, fibroblast seeded collagen matrix, fibroblast seeded polymer scaffolds and growth factors that enhance the healing of ligament injuries have shown promising success in research models for ligament tissue engineering.  Advances on understanding the mechanisms of sprains in knee ligaments will serve to improve the current treatment strategies and construct unprecedented graft substitutes.


 
Program Director:
 
 
 
Ted Conway
CBET Program Director - General and Age Related Disabilities Engineering
     
NSF Award Number:   0932024
     
Award Title:   Micro-Mechanical Characterization of Damage in Ligaments
     
Principal Investigator:   Raffaella De Vita
     
Institution Name:   Virginia Polytechnic Institute and State University
     
Program Element Code:   5342
     
CBET Research Highlight:   Fiscal Year 2012
     
Approved by CBET on:   27 March 2012
     
     


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This CBET Research Highlight was Updated on 16 April 2012.