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Abstract:

Sports-related anterior cruciate ligament (ACL) injuries continue to present as a serious and largely unexplained clinical dilemma. Currently, knee joint kinematic factors considered “high risk” are elucidated and screened via state-of-the-art motion capture methods. This strictly lab-based approach, however, has limited applicability to the true random sports environment, and does not afford instantaneous athlete feedback that may otherwise promote successful neuromuscular adaptation. Herein, we propose to develop and validate an alternative technology aimed at addressing these limitations explicitly. This technology, using light weight and extremely compact MEMS inertial sensors has the potential to significantly improve current ACL injury risk detection and prevention methods and to translate to other sports injury mechanisms. The current study aims to: 1) Develop a prototype MEMS system capable of quantifying knee joint kinematics during dynamic lower limb motions; Evaluate the efficacy of this measurement system during 2) Simulated (mechanical system) and 3) In vivo knee joint postures of increasing dynamic complexity. We will initially develop a prototype device based on our previously established designs for sports training aids. Above and below knee sensors will be fabricated and integrated within a novel body-worn measurement device wired to a light-weight (Palm Pilot) real-time data acquisition system. Temporarily based error functions will be obtained by comparing benchmark prototype and 3D motion capture kinematic outputs obtained for the pre-mentioned simulated and in vivo motion trials. Function norms will subsequently be defined, providing a scalar description of prototype efficacy for experimental case. If successful, this technology will enable extreme joint postures to be readily assessed within the true sports environment, providing the impetus for immediate and substantial further research. It will also facilitate the next important step towards the identification and subsequent prevention of realistic neuromechanical contributors to ACL injury risk. This will ultimately afford increased participation, quality of life and a reduced potential for long-term debilitation in a large number of relatively young individuals.

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Abstract:

Approximately 200,000 individuals suffer anterior cruciate ligament (ACL) ruptures annually in the U.S. A common clinical obstacle associated with ACL rupture and subsequent ACL reconstruction is an inability to achieve full voluntary activation of the quadriceps musculature. Quadriceps inhibition is thought to be the result of a neural inhibition preventing full voluntary muscle activation and is referred to as arthrogenic muscle inhibition (AMI). AMI hinders rehabilitation by preventing gains in strength, increasing the risk of re-injury, and potentially placing patients at risk for post-traumatic osteoarthritis. While much attention has been placed on identifying AMI after injury, little work has been conducted examining its consequences. The proposed research will determine: 1) the magnitude of quadriceps inhibition necessary to result in biomechanical and neuromuscular adaptations and 2) the feasibility of introducing neuromuscular electrical stimulation in rehabilitation post-ACL reconstruction to restore quadriceps activation and normal mechanics. We will capture the central activation ratio to assess quadriceps inhibition and lower extremity kinematics and kinetics during a forward hopping task to assess biomechanical adaptations. We hypothesize that 1) lower extremity mechanics and neuromuscular function will be dependent upon the magnitude of quadriceps inhibition and 2) neuromuscular electrical stimulation will increase quadriceps activation thereby improving lower extremity mechanics.

Relevance: ACL injury poses a high probability of lifetime compromise in physical functioning, as 70 percent ruptures ultimately result in osteoarthritis. Quadriceps inhibition is present following ACL injury and reconstruction and often persists for years following repair and its consequences remain elusive. Our work will allow for a better understanding of how muscle dysfunction impacts joint protective mechanisms. Introducing therapies focused on reducing AMI may promote sustained improvements in quadriceps activation thereby restoring lower extremity mechanics and potentially reducing the incidence of post-traumatic osteoarthritis. This knowledge will aid clinicians in designing appropriate rehabilitation protocols and return to play guidelines that will prevent future injury and joint degeneration.

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Abstract:

The CDC estimates that over 1.4 million people sustain a traumatic brain injury (TBI) each year in the U.S. About 75 percent of TBI that occur each year are concussions or mild TBI (MTBI). Up to 15 percent of patients diagnosed with MTBI may have persistent disabling symptoms. Adolescents and young adults are at the highest risk of sustaining a MTBI, while the pediatric brain is thought to be even more vulnerable. MTBI costs approximately $17 billion each year (CDC 1999). MTBI is likely to become an even bigger problem as Americans are increasingly encouraged to engage in physical activity to improve their health.

One of the leading causes of Mild Trauma Brain Injury (MTBI) includes sports activities. A recent study among high school athletes found that over one in eight of 1.4 million injuries reported were concussions. In our emergency department at the University of Michigan, 25 percent of concussions were sustained via participation in sports between 2005–2006 years. The percentage related to sports participation approached 70 percent when studied in the pediatric population. Recent NCAA data indicates that per exposure, women are at a higher risk of sustaining a head injury than men. For example, in 2005-06, collegiate women soccer players sustained concussions at a rate of 2.30 vs. 1.24 in men (13.9 percent vs. 6.3 percent of total injuries).

The sex hormones have been studied in animal models and in patients with severe TBI. Progesterone administration has been shown to be neuroprotective, associated with decreased cerebral edema, reduced mortality, and improved functional outcomes. Interestingly, hormones have been implicated in the risk of other injuries, including sprains, anterior cruciate ligament tears, and fractures. Perhaps the risk of all of these injuries has a common specific causal factor, which this study postulates is the effect of hormones on brain processing and reaction time.

This study will enroll seventy 15–24 year-old injured and thirty uninjured, male and female subjects presenting to the Adult or Pediatric Emergency Department and the NeuroSport Clinic at the University of Michigan. Survey, observational, and neuropsychological data will be evaluated. Urine and blood sampling will be performed and banked for future protein and DNA analysis.

The results of this study have major implications for female athletes, as well as physicians treating patients who have sustained a MTBI. If it can be shown that the increased risk of MTBI in women is due to neurocognitive differences, then strategies can be implemented to improve these parameters and decrease the risk of injury. In addition, if the risk of concussion is found to be influenced by the menstrual cycle, many elite athletes may choose to reduce this variable through use of oral contraceptive pills.

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Abstract:

Reaction time (RT) is important to the evaluation of sport-related concussion (SRC), with prolongation of RT often persisting beyond the point of clinical recovery and clearance for return to play. However, RT is most commonly measured with a personal computer and dedicated software, making its measurement unavailable to most athletes, particularly younger athletes who may be at increased risk for sequelae related to SRC. To expand the availability of RT measurement, we developed a clinical measure of RT (RTclin) using a simple, inexpensive, portable tool (a vertical cylinder which is released and caught as quickly as possible) that was a valid and reliable measure of RT in pilot studies. We will study 26 healthy young subjects, using kinematic and myoelectric methods, and pursue 2 aims:

The first aim is to test the hypothesis that RTclin predicts a sport-related protective reaction time (SPRT; raising the hands to protect the face and head from a projectile) with, and without, the prior administration of lorazepam, which is known to prolong RT by a central neurologic mechanism. If the hypothesis is confirmed the validity of RTclin with respect to a functional task relevant to the prevention of injury, the avoidance of a direct blow to the head or face is supported.

The second aim is to test the hypothesis that pre-motor time, rather than the other two components of RT (electromechanical delay and movement time), is primarily responsible for the lorazepam-induced prolongation of RTclin and SPRT. Because pre-motor time includes central neurologic events, data confirming this hypothesis support the validity of RTclin in the evaluation of associated delay in phalangeal or upper extremity acceleration. A sideline tool that can evaluate rapid central processing time is novel, and will be of benefit in monitoring the effects of sport-related head trauma and guiding decisions regarding return to play.

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Abstract:

The continued escalation of ACL injury rates, particularly in women, is a major clinical concern. We propose that by ignoring the impact of “non-modifiable” structural factors within the injury mechanism, which contribute significantly to resultant joint neuromechanics, and may in fact be modifiable, injury screening and prevention methods will remain severely flawed. Lower limb structural factors contribute directly to ACL injury risk and to the sex-disparity in injury rates. Many of these factors change considerably with growth and development, suggesting injury risk may be influenced by maturational progressions and the underlying mechanisms governing this pathway. Tracking the emergence and evolution of high-risk structural and mechanical factors across maturation, and identifying trainable parameters that may ultimately redirect this progression, such as habitual joint loading profiles, appears critical to long-term interventional prevention success.

Thus, the Specific Aims of the current study are to:

1. Demonstrate that individual-specific lower limb structural factors are significantly correlated with
high-risk knee joint mechanics during dynamic landing postures.

2. Demonstrate that structural and mechanical factors linked to ACL injury become increasingly and significantly correlated as maturation progresses.

3. Demonstrate that combined high-risk structural and mechanical profiles occur more often in maturing females than in maturing males.

4. Show that the development of combined high-risk structural and mechanical profiles is influenced by the habitual mechanical joint loading history.

Within a cross-sectional study design, at least 30 male and 30 females (8 -15 years) will have bi-lateral lower limb 3D joint biomechanics quantified during dynamic sports landings. Lower extremity structural (postural and anatomical) factors will also be quantified via standard clinical assessment and state-of-the-art magnetic resonance imaging techniques. Maturation and habitual physical activity levels will be initially determined for each subject via validated questionnaires. Regression models of increasing complexity will then be used to examine whether lower extremity mechanics can be predicted initially by structure, followed by cumulative limb, maturation and physical activity factors.  This study represents a critical step in identifying and ultimately countering the complex non-contact ACL injury mechanism. This in turn will afford a reduced potential for long-term debilitation and an increased quality of life in a large number of individuals, particularly females.

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Abstract:

The hip joint is one of the most common joints suffering from functionally limiting and debilitating
osteoarthritis, with end stage problems requiring total joint replacement. In the past, young patients with hip joint pain without advanced arthritis were often sent away from clinicians’ offices and told that nothing could be done. Until recently, this was common place. Now, with advanced arthroscopic and open techniques, new instrumentation, and a better clinical understanding of hip joint pathology, we are starting to make inroads into intervening earlier and more effectively than in the past. While there have been many studies focused on biomechanical parameters associated with hip reconstruction procedures, surprisingly few have focused on the fundamental biomechanical understanding of the native hip joint. Specifically, the role of the acetabular labrum in hip joint function remains unclear.

Understanding the functional anatomy of the acetabular labrum will not only help guide clinicians
to develop new techniques geared toward injury specific deficits, but also help us evaluate currently performed surgical interventions and decide which are appropriate from a functional anatomic standpoint or which should be modified. This research is critical before we proceed too far down the clinical path without sound biomechanical principles and basis to back our clinical decisions. Therefore, the purpose of this study is to determine the biomechanical function of the normal and injured labrum in the hip joint.

Our long-term research program will ultimately seek NIH R01 funding to further improve our understanding of the native hip joint by looking into the effects of clinically relevant dynamic muscle forces and joint positions on hip biomechanics, creating a biomechanical/mathematical model of the hip joint, then performing translational research based upon our findings to study 3-dimensional in vivo kinematics in healthy, diseased, and surgically treated hip joints.

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Abstract:

 Injury is the leading cause of morbidity and mortality in children.  Each year 92,000 children in the U.S. become permanently physically disabled as a result of their injuries. Falls are the leading cause of nonfatal unintentional injuries among hospitalized children (32.4%). Falls can results in injuries producing significant morbidity, future dysfunction, permanent disability (i.e. head injury) and death. In 2007, our database shows that 1,015 children under 18 years were hospitalized due to a fall at the University of Michigan CS Mott Children’s Hospital. Two hundred and forty two (24%) suffered traumatic brain injury while 678 (67%) sustained a fracture. A fall from playground equipment was the leading mechanism accounting for over 50% of the hospitalizations in school age children.

There are nationally recognized standards for playgrounds. At present, the diameters of the rungs and rails used on playground climbing structures are specified based on grip strength in children. But recent data from our group on work-related falls from ladders suggest that grip strength is not a reliable predictor of the breakaway force of a hand from a rail. Our working hypothesis is that an inappropriately large rail or rung diameter for the hand of a child of given age will lead to a one-handed breakaway force that is less than bodyweight, thereby causing a fall when the body is no longer supported by a foot. The goal of this study is to measure the effect of age, gender, body weight, and hand-hold orientation on the maximum volitional coupling force developed between a hand and a horizontal rung or inclined rail. We will test a total of 360 children between the ages of 5 and 11 years to establish the rational basis for the design of safer rails and rungs on the nations’ playground structures.

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Abstract:

Rotator cuff disorders are a common occupational and athletic musculoskeletal disorder. Physical therapy is an integral part of treating rotator cuff injuries, and it typically includes strengthening the shoulder musculature. Both payers and patients want to use as little time as possible to achieve therapeutic goals.  Therefore, there is a need to enhance the efficient use of each patient’s therapy session, regardless of whether it is done in a supervised setting or at home. The long-term goal of this project is to develop a mathematical model that can be used to
optimally plan physical therapy sessions to move efficiently use the available time.  The specific aim for this project is to develop a stochastic model for optimizing shoulder strength during rehabilitation of a rotator cuff disorder. The model will determine the best set of exercises to perform given a specified amount of time available for physical therapy. The best set of exercises may vary through course of treatment. We will formulate the model using the formalisms of a Markov decision process (MDP).This involves defining model states, decision rule (“policy”), probabilities of transitions between states, a function to be maximized (“contribution”), and planning horizon. The model will extend out previous work in two ways: (1) it will reflect the dynamically changing strength capability of the patient through the course of treatment, and (2) it will account for uncertainty in model parameters describing patient anatomy and physiology. Each stage of the model will correspond to a time point, t, during treatment. Uncertainty in how a patient will respond to a training stimulus will be modeled by treating strength gains as stochastic, i.e. a random process that describes how strength changes from time t to t+1. We will model changes in strength as changes in muscle physiological cross-sectional area (PCSA). The proposed work will fill in gaps that have been identified in critiques of our National Institute of Health grant applications on this topic.