Browsing by Author "Ashton-Miller, James A."

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    An Adolescent Murine In Vivo Anterior Cruciate Ligament Overuse Injury Model
    (Sage, 2023) Loflin, Benjamin E.; Ahn, Taeyong; Colglazier, Kaitlyn A.; Banaszak Holl, Mark M.; Ashton-Miller, James A.; Wojtys, Edward M.; Schlecht, Stephen H.; Orthopaedic Surgery, School of Medicine
    Background: Overuse ligament and tendon injuries are prevalent among recreational and competitive adolescent athletes. In vitro studies of the ligament and tendon suggest that mechanical overuse musculoskeletal injuries begin with collagen triple-helix unraveling, leading to collagen laxity and matrix damage. However, there are little in vivo data concerning this mechanism or the physiomechanical response to collagen disruption, particularly regarding the anterior cruciate ligament (ACL). Purpose: To develop and validate a novel in vivo animal model for investigating the physiomechanical response to ACL collagen matrix damage accumulation and propagation in the ACL midsubstance, fibrocartilaginous entheses, and subchondral bone. Study design: Controlled laboratory study. Methods: C57BL/6J adolescent inbred mice underwent 3 moderate to strenuous ACL fatigue loading sessions with a 72-hour recovery between sessions. Before each session, randomly selected subsets of mice (n = 12) were euthanized for quantifying collagen matrix damage (percent collagen unraveling) and ACL mechanics (strength and stiffness). This enabled the quasi-longitudinal assessment of collagen matrix damage accrual and whole tissue mechanical property changes across fatigue sessions. Additionally, all cyclic loading data were quantified to evaluate changes in knee mechanics (stiffness and hysteresis) across fatigue sessions. Results: Moderate to strenuous fatigue loading across 3 sessions led to a 24% weaker (P = .07) and 35% less stiff (P < .01) ACL compared with nonloaded controls. The unraveled collagen densities within the fatigued ACL and entheseal matrices after the second and third sessions were 38% (P < .01) and 15% (P = .02) higher compared with the nonloaded controls. Conclusion: This study confirmed the hypothesis that in vivo ACL collagen matrix damage increases with tissue fatigue sessions, adversely impacting ACL mechanical properties. Moreover, the in vivo ACL findings were consistent with in vitro overloading research in humans. Clinical relevance: The outcomes from this study support the use of this model for investigating ACL overuse injuries.
  • Thumbnail Image
    Item
    Association of pubovisceral muscle tear with functional capacity of urethral closure: evaluating maternal recovery from labor and delivery
    (Elsevier, 2020-06) Sheng, Ying; Liu, Xuefeng; Kane Low, Lisa; Ashton-Miller, James A.; Miller, Janis M.; School of Nursing
    Background Vaginal birth is a risk factor for pubovisceral muscle tear, decreased urethral closure pressure, and urinary incontinence. The relationship between these 3 factors is complicated. Urinary continence relies on maintaining urethral closure pressure, particularly when low urethral closure pressure can usefully be augmented by a volitional pelvic muscle (Kegel) contraction just before and during stress events like a cough. However, it is unknown whether a torn pubovisceral muscle decreases the ability to increase urethral closure during an attempted pelvic muscle contraction. Objective We tested the null hypothesis that a pubovisceral muscle tear does not affect the ability to increase urethral closure pressure during a volitional pelvic muscle contraction in the Evaluating Maternal Recovery from Labor and Delivery (EMRLD) study. Study Design We studied 56 women 8 months after their first vaginal birth. All had at least 1 risk factor for pubovisceral muscle tear (eg, forceps and long second stage). A tear was assessed bilaterally by magnetic resonance imaging. Urethral closure pressure was measured both at rest and during an attempted volitional pelvic muscle contraction. A Student t test was used to compare urethral closure pressures. Multiple linear regression was used to estimate the effect of a magnetic resonance imaging–confirmed pubovisceral muscle tear on volitionally contracted urethral closure pressure after adjusting for resting urethral closure pressure. Results The mean age was just a little more than 30 years, with the majority being white. By magnetic resonance imaging measure, unadjusted for other factors, the 21 women with tear had significantly lower urethral closure pressure during an attempted contraction compared with the 35 women without tear (65.9 vs 86.8 cm H 2O, respectively, P = .004), leading us to reject the null hypothesis. No significant group difference was found in resting urethral closure pressure. After adjusting for resting urethral closure pressure, pubovisceral muscle tear was associated with lower urethral closure pressure (beta = –21.1, P = .001). Conclusion In the first postpartum year, the presence of a pubovisceral muscle tear did not influence resting urethral closure. However, women with a pubovisceral muscle tear achieved a 25% lower urethral closure pressure during an attempted pelvic muscle contraction than those without a pubovisceral muscle tear. These women with pubovisceral muscle tear may not respond to classic behavioral interventions, such as squeeze when you sneeze or strengthen through repetitive pelvic muscle exercises. When a rapid rise to maximum urethral pressure is used as a conscious volitional maneuver, it appears to be reliant on the ability to recruit the intact pubovisceral muscle to simultaneously contract the urethral striated muscle.
  • Thumbnail Image
    Item
    Fatigue-driven compliance increase and collagen unravelling in mechanically tested anterior cruciate ligament
    (Springer Nature, 2023-05-26) Putera, Kevin H.; Kim, Jinhee; Baek, So Young; Schlecht, Stephen H.; Beaulieu, Mélanie L.; Haritos, Victoria; Arruda, Ellen M.; Ashton-Miller, James A.; Wojtys, Edward M.; Banaszak Holl, Mark M.; Orthopaedic Surgery, School of Medicine
    Approximately 300,000 anterior cruciate ligament (ACL) tears occur annually in the United States, half of which lead to the onset of knee osteoarthritis within 10 years of injury. Repetitive loading is known to result in fatigue damage of both ligament and tendon in the form of collagen unravelling, which can lead to structural failure. However, the relationship between tissue's structural, compositional, and mechanical changes are poorly understood. Herein we show that repetitive submaximal loading of cadaver knees causes an increase in co-localised induction of collagen unravelling and tissue compliance, especially in regions of greater mineralisation at the ACL femoral enthesis. Upon 100 cycles of 4× bodyweight knee loading, the ACL exhibited greater unravelled collagen in highly mineralized regions across varying levels of stiffness domains as compared to unloaded controls. A decrease in the total area of the most rigid domain, and an increase in the total area of the most compliant domain was also found. The results highlight fatigue-driven changes in both protein structure and mechanics in the more mineralized regions of the ACL enthesis, a known site of clinical ACL failure. The results provide a starting point for designing studies to limit ligament overuse injury.
  • Thumbnail Image
    Item
    The Right to Move: A Multidisciplinary Lifespan Conceptual Framework
    (Hindawi, 2012-12-03) Antonucci, Toni C.; Ashton-Miller, James A.; Brant, Jennifer; Falk, Emily B.; Halter, Jeffrey B.; Hamdemir, Levent; Konrath, Sara H.; Lee, Joyce M.; McCullough, Wayne R.; Persad, Carol C.; Seydel, Roland; Smith, Jacqui; Webster, Noah J.
    This paper addresses the health problems and opportunities that society will face in 2030. We propose a proactive model to combat the trend towards declining levels of physical activity and increasing obesity. The model emphasizes the need to increase physical activity among individuals of all ages. We focus on the right to move and the benefits of physical activity. The paper introduces a seven-level model that includes cells, creature (individual), clan (family), community, corporation, country, and culture. At each level the model delineates how increased or decreased physical activity influences health and well-being across the life span. It emphasizes the importance of combining multiple disciplines and corporate partners to produce a multifaceted cost-effective program that increases physical activity at all levels. The goal of this paper is to recognize exercise as a powerful, low-cost solution with positive benefits to cognitive, emotional, and physical health. Further, the model proposes that people of all ages should incorporate the "right to move" into their life style, thereby maximizing the potential to maintain health and well-being in a cost-effective, optimally influential manner.
  • Thumbnail Image
    Item
    State of the mineralized tissue comprising the femoral ACL enthesis in young women with an ACL failure
    (Wiley, 2021) Patton, Daniella M.; Ochocki, Danielle N.; Martin, Colin T.; Casden, Michael; Jepsen, Karl J.; Ashton-Miller, James A.; Wojtys, Edward M.; Schlecht, Stephen H.; Orthopaedic Surgery, School of Medicine
    Despite poor graft integration among some patients that undergo an ACL reconstruction, there has been little consideration of the bone quality into which the ACL femoral tunnel is drilled and the graft is placed. Bone mineral density of the knee decreases following ACL injury. However, trabecular and cortical architecture differences between injured and non-injured femoral ACL entheses have not been reported. We hypothesize that injured femoral ACL entheses will show significantly less cortical and trabecular mass compared to non-injured controls.Femoral ACL enthesis explants from 54 female patients (13 – 25 years) were collected during ACL reconstructive surgery. Control explants (n = 12) were collected from 7 donors (18 - 36 years). Injured (I) femoral explants differed from those of non-injured (NI) controls with significantly less (p ≤ 0.001) cortical volumetric bone mineral density (vBMD) (NI: 736.1 – 867.6 mg/cc; I: 451.2 – 891.9 mg/cc), relative bone volume (BV/TV) (NI: 0.674 – 0.867; I: 0.401 – 0.792) and porosity (Ct.Po) (NI: 0.133 – 0.326; I: 0.209 – 0.600). Injured explants showed significantly lesstrabecular vBMD (p = 0.013) but not trabecular BV/TV (p = 0.314), thickness (p = 0.412), or separation (p = 0.828). We found significantly less cortical bone within injured femoral entheses compared to non-injured controls.Lower cortical and trabecular bone mass within patient femoral ACL entheses may help explain poor ACL graft osseointegration outcomes in the young and may be a contributor to the osteolytic phenomenon that often occurs within the graft tunnel following ACL reconstruction.