Incidence and mechanism of the pivot shift. An in vitro study.

Accepted versio

ACL Research Retreat VII: An Update on Anterior Cruciate Ligament Injury Risk Factor Identification, Screening, and Prevention March 19–21, 2015; Greensboro, NC

The seventh ACL Research Retreat was held March 19–21, 2015, in Greensboro, North Carolina. The retreat brought together clinicians and researchers to present and discuss the most recent advances in anterior cruciate ligament (ACL) injury epidemiology, risk factor identification, and injury risk screening and prevention strategies. Subsequently, our goal was to identify important unknowns and future research directions

Dynamic Simulations and Data Mining of Single-Leg Jump Landing: Implications for Anterior Cruciate Ligament Injury Prevention

It is estimated that 400,000 anterior cruciate ligament (ACL) injuries occur in the United States each year with the cost of ACL reconstruction surgery and rehabilitation exceeding $1 billion annually. The majority of ACL injuries are non-contact injuries occurring during cutting and jump landing movements. Because the majority of the injuries are non-contact injuries there is the potential to develop programs to reduce the risk of injury. Given our understanding of the joint kinematics and kinetics that place an individual at high risk for ACL, researchers have developed neuromuscular training programs that focus on improving muscle function in order to help the muscles support and stabilize the knee during the dynamic movements that increase the strain on the ACL. Yet, despite the implementation of these neuromuscular-based ACL injury training intervention programs ACL rates continue to rise. Thus the objective of this dissertation is to determine the cause and effect relationship between joint biomechanics and muscle function with respect ACL injury. There are four studies in this dissertation. The first two studies rely heavily on the development of subject-specific musculoskeletal models to analyze muscle contribution during single-leg jump landing. These studies will generate forward dynamic simulations to estimate muscle force production and contribution to movement. The results of these studies will aid in the development of muscle-targeted ACL injury training intervention programs. The last two studies will employ data mining techniques; such as, principal component analysis (PCA) and wavelet analysis along with stability methods from control theory, to evaluate an individual’s risk of ACL injury and determine how muscle function differs for individuals at varying levels of injury risk. The goal will be to use this information to develop a more robust ACL injury prescreening tool. The use of both dynamic simulations and data mining techniques provides a unique approach to investigating the relationship between joint biomechanics and muscle function with respect to ACL injury. And this approach has the potential to gain much needed insight about the underlying mechanism of ACL injury and help progress ACL research forward

In Vitro Biomechanical Analyses of The PCL and Medial Ligaments of The Human Knee

Previous studies have shown that surgical treatments of PCL injuries are not successful in all cases and there is room for improvement. The effectiveness of an isolated PCL reconstruction, in the setting of what actually is a multi-ligament injury, may be inadequate, and therefore the biomechanical contribution of other ligaments in a PCL-deficient knee need to be better understood. A new apparatus was used to analyze the effect of medial ligaments transection on the kinematics of the PCL-deficient knee during simulated clinical tests and activities of daily living. We observed that the anterior translation of the medial side of the joint increased after transection of the POL; however, this increase was small. Transection of neither the POL nor dMCL affected the posterior translation of the medial aspect of the joint; however, both contributed to resisting loads crossing the joint, which increase after the PCL transection

Functional Tissue Engineering of the Healing Anterior Cruciate Ligament: A Combined Experimental and Computational Approach

The anterior cruciate ligament (ACL) is the most important knee stabilizer and is frequently injured during sports and work related activities. Unfortunately, midsubstance ACL ruptures have a limited healing capacity. As such, surgical reconstruction using soft tissue autografts is often performed. However, long-term follow-up studies have revealed that 20-25% of patients had a less than satisfactory outcome. These negative results have renewed clinical interests in healing of a torn ACL by means of biological stimulation. Thus, there is a need for basic science studies in order to better understand such an approach and also to logically develop an effective functional tissue engineering (FTE) treatment for an injured ACL. The overall objective of this dissertation was to evaluate the positive impact of biological and mechanical augmentation on the healing of the ACL using a combined experimental and computational approach. The ability of an extracellular matrix (ECM) bioscaffold in combination with an ECM hydrogel to enhance ACL healing following suture repair was first demonstrated in the goat model. At 12 weeks of healing, ECM-treatment led to an increase in neo-tissue formation as well as improved biomechanical properties of the healing ACL compared to suture repair alone. Second, as the healing process of the ACL was relatively slow even with ECM treatment, mechanical augmentation to better restore initial joint stability was required. Therefore, a suture augmentation procedure was developed, and improved joint function was achieved versus suture repair alone at the time of surgery. Further, there was increased tissue formation and improved biomechanical properties of the healing ACL at 12 weeks of healing. Finally, as a step toward predicting long-term outcomes following these biological and mechanical augmentation procedures, a preliminary mathematical model was developed to describe the remodeling process of healing ligaments. The results of this work can now be used to guide future experiments using FTE treatments to enhance ACL healing. With a sound scientific basis, it is hoped that such exciting new technologies could then be translated into the clinical arena to improve patient outcome following ACL injuries

Motor coordination during gait after anterior cruciate ligament injury: a systematic review of the literature

AbstractTo investigate the state of art about motor coordination during gait in patients with anterior cruciate ligament (ACL) injury. Searches were carried out, limited from 1980 to 2010, in various databases with keywords related to motor coordination, gait and ACL injury. From the analysis of titles and applying the inclusion/exclusion criteria 24 studies were initially selected and, after reading the abstract, eight studies remained in the final analysis. ACL deficient patients tend to have a more rigid and less variable gait, while injured patients with ACL reconstruction have less rigid and more variable gait with respect to healthy individuals. The overall results suggest the existence of differences in motor coordination between the segments with intact and those with injured knee, regardless of ligament reconstruction. ACL injured patients present aspects related to the impairment of the capability to adapt the gait pattern to different environmental conditions, possibly leading to premature knee degeneration. However, the techniques used for biomechanical gait data processing are limited with respect to obtaining information that leads to the development of intervention strategies aimed at the rehabilitation of that injury, since it is not possible to identify the location within the gait cycle where the differences could be explained

ACL Research Retreat V: An Update on ACL Injury Risk and Prevention, March 25–27, 2010, Greensboro, NC

Multiple factors, whether individually or in combination, likely contribute to noncontact anterior cruciate ligament (ACL) injury. Although research has increased our understanding of contributing factors, much remains unknown, and continued research is needed. To that end, the fifth ACL Research Retreat was held at the University of North Carolina at Greensboro, March 25–27, 2010. The retreat's ongoing mission is to (1) present and discuss the most recent research on ACL injury risk and prevention and (2) identify new research directives aimed at understanding the epidemiology, risk factors, and prevention of noncontact ACL injury. This year, 75 clinicians and researchers representing 6 countries participated.All the keynote presenters are expert scientists engaged in cutting-edge research on ACL injury risk and prevention. Edward Wojtys, MD; Stephen W. Marshall, PhD; Darin A. Padua, PhD, ATC; and Christopher M. Powers, PT, PhD, focused on issues related to clinical and research considerations for ACL-injured pediatric and adolescent athletes, current trends in injury epidemiology, and new directions in risk-factor assessment and efficacy of injury-prevention programs. Forty podium and poster presentations were organized into thematic sessions: risk-factor assessment (specifically factors associated with spinal and trunk control, muscle strength and fatigue, anatomical and hormonal factors, and landing and cutting strategies), injury mechanisms, risk-factor screening, and prevention. A meeting hallmark is the substantial time provided for group discussion after each keynote address and thematic podium session. To close the meeting, participants revisited and updated the consensus statement from the 2008 ACL Research Retreat IV1 and charted new directions for future research. Following are the updated consensus statement, keynote presentation summaries, and abstracts organized by topic and presentation order