OBJECTIVE To clarify and improve a cranial cruciate ligament (CrCL) deficient stifle stabilization technique using a semitendinosus tendon (ST) autograft fixed with an interference fit screw (IFS) in a closed-joint trauma lapine... more
OBJECTIVE To clarify and improve a cranial cruciate ligament (CrCL) deficient stifle stabilization technique using a semitendinosus tendon (ST) autograft fixed with an interference fit screw (IFS) in a closed-joint trauma lapine osteoarthritis (OA) model. STUDY DESIGN Experimental OA model. ANIMALS Forty-one Flemish Giant rabbits. METHODS Following arthrotomy of traumatized lapine stifles, the ST insertion on the tibial plateau was exposed and the ST was transected near its origin. The graft was passed through tibial and femoral tunnels, manually tensioned and then secured in place with a custom IFS and periosteal sutures. Drawer was manually assessed during and immediately after surgery intraoperatively. Upon euthanasia, joint laxity was measured at 2, 10, or 22 weeks postoperatively and compared to that of the contralateral, intact stifles and stifles with a surgically transected CrCL. RESULTS Minimal postoperative drawer was present in 34% of the rabbits and potentially correlated with meniscal injury and subsequent meniscectomy. CrCL reconstruction significantly reduced joint laxity to a level (3.6 ± 1.6 mm) similar to that (2.7 ± 0.8 mm) in contralateral intact stifles. CONCLUSION Surgical replacement of a traumatically injured CrCL using a ST autograft fixed with an IFS replicated a common human surgical technique and effectively restored joint stability in the short, medium, and long terms of the study. CLINICAL SIGNIFICANCE The study provides researchers a useful, clinically relevant, post-traumatic CrCL deficient rabbit model for the study of OA and investigations of interventions to mitigate or prevent long-term joint degeneration.
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According to the National Accident Sampling System (NASS), 10% of all automobile accident injuries involve the knee. These injuries involve bone fracture and/or "soft tissue" injury. Previous... more
According to the National Accident Sampling System (NASS), 10% of all automobile accident injuries involve the knee. These injuries involve bone fracture and/or "soft tissue" injury. Previous investigators have determined the tibial-femoral (TF) joint failure load for an experimentally constrained human knee at 90 degrees flexion. In these experiments bone fractures have been documented. During TF joint compression, however, anterior motion of the tibia has been noted by others. It was therefore the objectives of this study to document effects of flexion angle and anterior-posterior joint constraint on the nature and severity of knee injury during TF compression loading via axial loads in the tibia. The effect of flexion angle was examined using 10 unconstrained human knees from 5 cadavers aged 73.2+/-9.4 years. The tibial-femoral joint was loaded in compression as a result of axial loading along the tibia using a servo-hydraulic testing machine until gross failure with the knee flexed 60 degrees or 120 degrees . Pressure sensitive film measured the distribution of internal TF joint loads. Both 60 degrees and 120 degrees flexed preparations failed by rupture of the anterior cruciate ligament (ACL) at 4.6+/-1.2 kN, and the internal joint loads were significantly higher (2.6+/-1.5 kN) on the medial versus the lateral (0.4+/-0.5 kN) aspect of the tibial plateau. The effect of anterior-posterior (AP) constraint of the femur along the longitudinal axis of the femur was investigated in a second series of tests using the same TF joint loading protocol on 6 pairs of human joints (74.3+/-10.5 years) flexed at 90 degrees . The primary mode of failure for the AP constrained joints was fracture of bone via the femoral condyle at a maximum load of 9.2+/-2.6 kN. The mode of failure for unconstrained joints was primarily due to rupture of the ACL at a maximum load of 5.8+/-2.9 kN. Again, the pressure film indicated an unequal internal TF load distribution for the unconstrained knee (medial plateau 4.1+/-1.9 kN versus lateral plateau 0.8+/-0.8 kN). However, there was a more equal distribution of internal loads between the medial (4.4+/-1.8 kN) and lateral (2.8+/-1.9 kN) aspects of the tibial plateau in the constrained joints. This study showed that the mechanism of tibial-femoral knee joint injury and internal TF joint load distribution depends on the degree of AP constraint offered by the test apparatus. Flexion angle did not significantly affect failure load or the mechanism of failure for the unconstrained knee. The findings from this study may be useful in understanding the complex failure mechanisms for an unconstrained knee under axial compression loads in the tibia during automobile crashes.
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The tensile strength of skin is associated, in part, with its potential for laceration from impact. The quasi-static tensile strength of skin depends on orientation. The objective of this study was to determine whether the strength of... more
The tensile strength of skin is associated, in part, with its potential for laceration from impact. The quasi-static tensile strength of skin depends on orientation. The objective of this study was to determine whether the strength of skin in high speed tensile failure experiments exhibits a similar dependence on orientation. Tensile experiments were conducted at 6000 percent/s and 30 percent/s on dorsal skin of rats aged 1–6 months. Experiments were performed on specimens cut perpendicularly and longitudinally to the spine at cranial and caudal locations. The tensile failure properties depended on location, orientation, age and strain rate. The strength was dependent on orientation to the same degree in high and low speed tests. This helps explain why accident statistics show that skin lacerates preferentially on the body.
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ABSTRACT Effective prevention and treatment of osteoarthritis for horses is still needed. This research tests the ability of glucosamine and chondroitin sulfate (GLN/CS) to mitigate inflammatory and mechanical stress in vitro. In this... more
ABSTRACT Effective prevention and treatment of osteoarthritis for horses is still needed. This research tests the ability of glucosamine and chondroitin sulfate (GLN/CS) to mitigate inflammatory and mechanical stress in vitro. In this study, GLN/CS mediate this effect by a decrease of the synthesis of nitric oxide (NO) and a decrease of proteoglycan release from the extracellular matrix in stressed cartilage explants. Explants were cultured with interleukin-1 (IL-1) + mechanical trauma with and without GLN/CS. NO and prostaglandin E2 were measured as indicators of an inflammatory response. Glycosaminoglycans were measured as an indicator of cartilage breakdown. NO levels in the stressed explants with GLN/CS treatment were lower than the IL-1 + mechanical impact treatment alone and did not differ from control group. The glycosaminoglycan release was also lower in the GLN/CS treatment than the IL-1 + mechanical impact treatment, although the prostaglandin E2 concentration was not affected. This study offers some evidence that GLN/CS treatment can partially mitigate the catabolic response to inflammatory stress and mechanical trauma in equine cartilage explants. These results provide additional support for the continued study on the benefit of GLN/CS for horses with cartilage degeneration.
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The human body is composed of four primary groups of tissues: (1) Epithelial tissues are characterized by having cells closely joined one to another and found on free surfaces of the body.(2) Muscle tissues are characterized by the high... more
The human body is composed of four primary groups of tissues: (1) Epithelial tissues are characterized by having cells closely joined one to another and found on free surfaces of the body.(2) Muscle tissues are characterized by the high degree of contractility of their cells or fibers. Their primary function is to move the skeleton.(3) Nervous tissues are composed of cells specialized in the properties of irritability and conductility. (4) Connective tissues are those in which the cells are separated by large amounts of extracellular materials.
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The rotational stiffness of footwear has been previously shown to have an effect on ankle kinematics and injury risk, but this relationship has not yet been modeled. The aim of this study was to derive equations from experimental data... more
The rotational stiffness of footwear has been previously shown to have an effect on ankle kinematics and injury risk, but this relationship has not yet been modeled. The aim of this study was to derive equations from experimental data that were able to predict ankle kinematics under various torsional stiffness constraints and use these equations to estimate ligament strains. Three athletic tapes were tested for their ability to constrain the ankle during external rotation. Six subjects then performed a voluntary external foot rotation using the selected tape designs to constrain the ankle, as well as with no constraints. The motion of the calcaneus with respect to the tibia (tibiocalcaneal motion) from 0° to 15° of tibia rotation and predictive equations were determined to establish tibiocalcaneal rotation, eversion, and flexion as a function of gross tibia motion and tape stiffness. These predictive equations were then used to drive a computational model in which ankle ligament strains were determined at 15° of tibia rotation and for ankle constraint stiffness ranging from 0 to 30 N m/deg. The three tapes provided significantly different constraint stiffnesses during external foot rotation. There was no statistical effect of ankle constraint on the dorsiflexion response of the ankle (p = 0.461). In contrast, there was an effect of constraint stiffness on tibiocalcaneal external rotation (p < 0.001) and tibiocalcaneal eversion (p < 0.001). Results of the model simulation revealed the highest ligament strains in the anterior tibiotalar ligament and anterior tibiofibular ligament. Anterior tibiotalar ligament strain increased with increasing constraint stiffness, while there was little effect of constraint stiffness on anterior tibiofibular ligament strain. Results from this study could aid in the design of footwear, as well as the analysis of clinical injuries.
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The meniscus is comprised of two semilunar disks resting between the articular surface of the tibial plateaus and femoral condyles within the knee joint of each leg [1–3]. Both the medial and lateral menisci play a vital role in... more
The meniscus is comprised of two semilunar disks resting between the articular surface of the tibial plateaus and femoral condyles within the knee joint of each leg [1–3]. Both the medial and lateral menisci play a vital role in maintaining the joint’s integrity by distributing loads, stabilizing and lubricating the joint, and proprioceptive functions [2,3]. While the meniscus is found in many animals, morphological variations are present between species, indicating differences in the biomechanics of the joint [1,2]. These anatomical variations have not been quantified and, thus, remain unlinked to further structural changes that occur with injury. The goals of this study were aimed towards characterizing the normal lapine meniscal tissue using regional comparisons for tissue area and cell density measurements. The preliminary data from this research will be used as a comparison against future animal injury models. It was hypothesized that a difference would be observed between anterior, central, and posterior divisions in the normal lapine meniscus.
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ABSTRACT Acute knee joint injury has been associated with the development and progression of secondary osteoarthritis (OA). Previous work implicates that acute damage to tissue matrix and cells of the meniscus and articular cartilage may... more
ABSTRACT Acute knee joint injury has been associated with the development and progression of secondary osteoarthritis (OA). Previous work implicates that acute damage to tissue matrix and cells of the meniscus and articular cartilage may play important roles in early-stage OA [1]. Additionally, it has been shown that articular cartilage matrix repair hinges on chondrocyte preservation [2]. Therefore, inhibition of cell death may halt tissue degeneration. Recently, the FDA-approved surfactant Poloxamer 188 (P-188) has been shown to decrease acute cell death by repair of its plasma membrane, as well as mediate p38 signaling and subsequent inflammatory and apoptotic signaling leading to a reduction in degeneration of impacted cartilage [3, 4]. Therefore, it was hypothesized that matrix glycosaminoglycans of the meniscus will be preserved in the long-term following traumatic impaction and subsequent treatment with P-188.
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ABSTRACT Participation in sports, recreation, and exercise is progressively gaining more popularity in American culture and, along with it, the risk of acute and chronic injuries. People who injure a knee before the age of 22 have a... more
ABSTRACT Participation in sports, recreation, and exercise is progressively gaining more popularity in American culture and, along with it, the risk of acute and chronic injuries. People who injure a knee before the age of 22 have a greater than 3-fold risk of developing osteoarthritis (OA) in the injured joint by their mid 50s5. Specifically, anterior cruciate ligament (ACL) and meniscal injuries are strongly associated with the development of OA4, a common and widespread musculoskeletal disease1.
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Numerous studies have been conducted to evaluate the properties of shoe-surface interface conditions on natural grass and synthetic turfs [2,7,9]. It is suggested that ankle injuries are related to the torque generated in the joint.... more
Numerous studies have been conducted to evaluate the properties of shoe-surface interface conditions on natural grass and synthetic turfs [2,7,9]. It is suggested that ankle injuries are related to the torque generated in the joint. Recently, our laboratory has developed a surrogate ankle [10] for use with a rotational traction measurement apparatus on various surfaces [9]. External rotation, commonly thought as the mechanism of a high ankle sprain in football, is applied to the surrogate foot and the resistive torque is measured. The study suggests that synthetic turfs generate higher ankle torques than natural grasses, therefore implying a high injury risk on turfs. One disadvantage of these studies is that only artificial devices are used to represent the ankle. Consequently, it is not possible to determine ligament strains, which is crucial in determining ankle injury.
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High ankle sprains are commonly associated with injury to the distal tibiofibular syndesmotic ligaments and represent a more disabling problem for athletes than other ankle sprains [1]. This injury is associated with excessive internal... more
High ankle sprains are commonly associated with injury to the distal tibiofibular syndesmotic ligaments and represent a more disabling problem for athletes than other ankle sprains [1]. This injury is associated with excessive internal rotation of the body relative to a planted foot [2]. Torsional traction between the shoe and the playing surface is a factor in these injuries [3].
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In this study it is shown that subfracture impact loading to a joint creates stresses in cartilage and bone which can initiate a chronic osteoarthrosis. The magnitude and location of the impact induced stresses are dependent on the... more
In this study it is shown that subfracture impact loading to a joint creates stresses in cartilage and bone which can initiate a chronic osteoarthrosis. The magnitude and location of the impact induced stresses are dependent on the orientation and the intensity of loading. Impact loading produced lesions on retro-patellar cartilage and their depths increased as the thickness of subchondral bone increased with time post-impact. Mechanical tests of cartilage indicated significant softening twelve months post-impact. These alterations are similar to those documented clinically as early OA (osteoarthrosis, osteoarthritis). In vitro impacts of isolated limbs, together with mathematical models, showed that high mean stress generated during impact may help protect joint tissues from acute injury. This study and other studies are used to develop stress-based tissue failure criteria for predicting an osteoarthrosis following subfracture impact loading. (A) For the covering abstract of the conference see IRRD 891635.
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Abstractconsuming and serial sections were difficult to acquire with the paraffin tape-transfer technique. We also investigated procedures to reduce processing time by drilling shallow holes in the anterior surface to improve the... more
Abstractconsuming and serial sections were difficult to acquire with the paraffin tape-transfer technique. We also investigated procedures to reduce processing time by drilling shallow holes in the anterior surface to improve the penetration of fixative and decalcification fluids. The processing time was significantly reduced from 50 to 32 days. (The J Histotechnol 21:151, 1998)
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Various studies suggest impact trauma may initially soften cartilage, damage subchondral bone, or a combination thereof. The initial damages are commonly thought due to excessive contact pressures generated on cartilage and the underlying... more
Various studies suggest impact trauma may initially soften cartilage, damage subchondral bone, or a combination thereof. The initial damages are commonly thought due to excessive contact pressures generated on cartilage and the underlying bone. The objective of this research was to develop a small animal model for studying post-traumatic OA and to correlate contact pressures with tissue damage. Blunt insult was graded by dropping a rigid mass onto the hyperflexed hind limb of rabbits. Contact pressure in the patello-femoral joint was measured with pressure sensitive film. One, 3, 6, and 14 days later the animals were euthanized. Damage to cartilage and the underlying bone was assessed visually and in microscopic sections. Indentation experiments were performed on the patellar cartilage with a rigid, flat probe. Contact pressures were nonuniform over the articular surfaces and a high frequency of surface fissures were generated on the lateral facet in severe insults. The appearance of surface fissures correlated better with the magnitude of contact pressure gradients in the damage zone than the magnitude of contact pressures on the facet, per se. Blunt trauma causing surface fissures resulted in a measurable degree of softening in the patellar cartilage, especially close to the defects. Surgical intervention of the joint to insert pressure sensitive film, however, also resulted in significant softening of the cartilage.
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ABSTRACT The meniscus is an important load-bearing structure in the knee, as it provides load distribution and cushioning properties during weight-bearing activities. The compressive modulus and permeability of the meniscus is attributed... more
ABSTRACT The meniscus is an important load-bearing structure in the knee, as it provides load distribution and cushioning properties during weight-bearing activities. The compressive modulus and permeability of the meniscus is attributed to the tissue’s glycosaminoglycan (GAG) content, as charged proteoglycan side chains allow for tissue swelling and resistance to compression [1]. The distribution of sulphated GAGs throughout the meniscus has not been thoroughly documented. Although load differs across the knee joint, few researchers have investigated medial/lateral and coronal differences in meniscal architecture and GAG distribution [2, 3]. It is hypothesized that the distribution of positive histological staining for sulfated GAGs will differ across spatial regions of rabbit menisci. Primarily, it is hypothesized that regions of the menisci that likely see higher loading will demonstrate an increase in sulfated GAG-positive staining area.
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OBJECTIVE To determine the efficacy of single and multiple administrations of Poloxamer 188 (P188) in saving meniscal cells following an injurious impact. METHODS Meniscal explants were harvested from both the lateral and medial menisci... more
OBJECTIVE To determine the efficacy of single and multiple administrations of Poloxamer 188 (P188) in saving meniscal cells following an injurious impact. METHODS Meniscal explants were harvested from both the lateral and medial menisci of Flemish Giant rabbits. After a 24-h incubation period, explants were subjected to 50% impact strain to simulate traumatic joint injury, and the explants were then placed in media with or without supplemented P188. Temporal administrations of P188 over a 14-day period were given based on one of 6 different treatments regimes. Over the 14-day period, explants were cyclically loaded to 10% strain at 1 Hz for 1 h per day, five days a week. Cell viability was assessed on day 14, with the remainder of the tissue being fixed to determine cell apoptosis levels and proteoglycan changes via histology. RESULTS The injurious impact proved to produce significant levels of cell death in meniscal explants. The ability of P188 to prevent cell death was not affected by the number of P188 doses (single versus multiple). P188 treatment proved to maintain cell viability levels comparable to those from unimpacted explants. There were no significant changes in cell apoptosis or proteoglycan coverage in the tissues over a 14-day period for any group, all treatment groups were statistically similar to the unimpacted explants. CONCLUSION A single dose of P188 following impact is all that is necessary to inhibit cell death in the meniscus following a traumatic impact. Thus, orthopaedic surgeons may choose to administer P188 in addition to treating any other acute damage due to a traumatic load to the knee, such as anterior cruciate ligament rupture, although more in depth in vivo studies are necessary.
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Recent studies, using two different manners of foot constraint, potted and taped, document altered failure characteristics in the human cadaver ankle under controlled external rotation of the foot. The posterior talofibular ligament... more
Recent studies, using two different manners of foot constraint, potted and taped, document altered failure characteristics in the human cadaver ankle under controlled external rotation of the foot. The posterior talofibular ligament (PTaFL) was commonly injured when the foot was constrained in potting material, while the frequency of deltoid ligament injury was higher for the taped foot. In this study an existing multibody computational modeling approach was validated to include the influence of foot constraint, determine the kinematics of the joint under external foot rotation, and consequently obtain strains in various ligaments. It was hypothesized that the location of ankle injury due to excessive levels of external foot rotation is a function of foot constraint. The results from this model simulation supported this hypothesis and helped to explain the mechanisms of injury in the cadaver experiments. An excessive external foot rotation might generate a PTaFL injury for a rigid foot constraint, and an anterior deltoid ligament injury for a pliant foot constraint. The computational models may be further developed and modified to simulate the human response for different shoe designs, as well as on various athletic shoe–surface interfaces, so as to provide a computational basis for optimizing athletic performance with minimal injury risk.
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ABSTRACT Long-term participation in vigorous physical activity increases the risk of acute and chronic injuries to the knee. Two specific types of injury strongly associated with subsequent knee osteoarthritis (OA) are cruciate ligament... more
ABSTRACT Long-term participation in vigorous physical activity increases the risk of acute and chronic injuries to the knee. Two specific types of injury strongly associated with subsequent knee osteoarthritis (OA) are cruciate ligament damage and meniscal tears. Many clinical studies have discussed the high frequency of noncontact ACL injuries, for example, from jump landings. Axial compressive loading of the knee during landing from a jump can generate approximately 6–8 times bodyweight. With the tibial plateau having an inherent posterior slope of 10–15°, these loads can produce an anterior shift of the tibia during jump landings that result in isolated rupture of the anterior cruciate ligament (ACL) in the laboratory.1 These studies have shown acute damages in the articular cartilage and underlying subchondral and trabecular bone in the human cadaver joint.2 Clinically, in over 80% of ACL injury cases, characteristic osteochondral lesions occur in the posterolateral aspect of the tibia and/or anterolateral aspect of the lateral femoral condyle, potentially due to these levels of joint compressive loads.3
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Eversion prior to excessive external foot rotation has been shown to predispose the anterior tibiofibular ligament (ATiFL) to failure, yet protect the anterior deltoid ligament (ADL) from failure despite high levels of foot rotation. The... more
Eversion prior to excessive external foot rotation has been shown to predispose the anterior tibiofibular ligament (ATiFL) to failure, yet protect the anterior deltoid ligament (ADL) from failure despite high levels of foot rotation. The purpose of the current study was to measure the rotations of both the subtalar and talocrural joints during foot external rotation at sub-failure levels in either a neutral or a pre-everted position as a first step towards understanding the mechanisms of injury in previous studies. Fourteen (seven pairs) cadaver lower extremities were externally rotated 20° in either a pre-everted or neutral configuration, without producing injury. Motion capture was performed to track the tibia, talus, and calcaneus motions, and a joint coordinate system was used to analyze motions of the two joints. While talocrural joint rotation was greater in the neutral ankle (13.3±2.0° versus 10.5±2.7°, p=0.006), subtalar joint rotation was greater in the pre-everted ankle (2.4±1.9° versus 1.1±1.0°, p=0.014). Overall, the talocrural joint rotated more than the subtalar joint (11.9±2.8° versus 1.8±1.6°, p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). It was proposed that the calcaneus and talus &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;lock&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; in a neutral position, but &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;unlock&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; when the ankle is everted prior to rotation. This locking/unlocking mechanism could be responsible for an increased subtalar rotation, but decreased talocrural rotation when the ankle is pre-everted, protecting the ADL from failure. This study may provide information valuable to the study of external rotation kinematics and injury risk.
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ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth... more
ABSTRACT Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal
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SummaryObjective: To compare the mechanical properties of pancarpal arthrodesis (PCA) constructs stabilized at 20° of extension using either a 3.5 mm limited contact dynamic compression plate (LC-DCP) or a 3.5/2.7 mm hybrid plate... more
SummaryObjective: To compare the mechanical properties of pancarpal arthrodesis (PCA) constructs stabilized at 20° of extension using either a 3.5 mm limited contact dynamic compression plate (LC-DCP) or a 3.5/2.7 mm hybrid plate (HP).Methods: Seven forelimb pairs were used from dogs of similar size. All soft tissues were removed except for supporting structures of the carpus and proximal metacarpal region. All plates were accurately bent to 20°, and then instrumented with two, 350Ω strain gauges applied at the level of the bend. Constructs were embedded in epoxy moulds then mounted onto a servo-hydraulic testing machine. Specimens were loaded for 10 cycles at 100N, 200N and 300N. Tenth cycle construct compliance (CC), maximum angular deformation (MAD), and peak plate strain (PPS) were compared using two-factor analysis of variance (ANOVA) and Student-Newman- Keuls post-hoc tests (p &lt;0.05).Results: Regardless of load, CC was 29% to 33% smaller in the HP than the LC-DCP group (p &lt;0.03). In each group, the CC significantly increased with increasing loads (p &lt;0.02). Mean MAD was 19% to 22% less in HP than LC-DCP constructs, with significant differences seen at 200N and 300N loads. In both groups, MAD was significantly greater with increasing loads (p &lt;0.02). In addition, PPS was 37% to 43% smaller for HP than LC-DCP.Clinical significance: The mechanical advantages of the HP over the LC-DCP make it a viable alternative for PCA. Smaller CC, MAD and PSS of the HP may reduce the risk of implant failure and postoperative morbidity following PCA.
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Post-traumatic osteoarthritis (PTOA) is a debilitating disease that is a result of a breakdown of knee joint tissues following traumatic impact. The interplay of how these tissues influence each other has received little attention because... more
Post-traumatic osteoarthritis (PTOA) is a debilitating disease that is a result of a breakdown of knee joint tissues following traumatic impact. The interplay of how these tissues influence each other has received little attention because of complex interactions. This study was designed to correlate the degeneration of the menisci, cartilage and subchondral bone following an acute traumatic event that resulted in anterior cruciate ligament (ACL) and medial meniscus tears. We used a well-defined impact injury animal model that ruptures the ACL and tears the menisci. Subsequently, the knee joints underwent ACL reconstruction and morphological analyses were performed on the menisci, cartilage and subchondral bone at 1-, 3- and 6-months following injury. The results showed that the morphological scores of the medial and lateral menisci worsened with time, as did the tibial plateau and femoral condyle articular cartilage scores. The medial meniscus was significantly correlated to the med...
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Previous studies have shown that reconstructive surgery alone following injury to the anterior cruciate ligament (ACL) does not prevent the development of post-traumatic osteoarthritis (PTOA). Poloxamer 188 (P188) has been shown to... more
Previous studies have shown that reconstructive surgery alone following injury to the anterior cruciate ligament (ACL) does not prevent the development of post-traumatic osteoarthritis (PTOA). Poloxamer 188 (P188) has been shown to prevent cell death following trauma in both articular cartilage and meniscal tissue. This study aims to test the efficacy of single or multiple administrations of P188 in conjunction with reconstructive surgery to help prevent or delay the onset of the disease. Thirty skeletally mature rabbits underwent closed-joint trauma that resulted in ACL rupture and meniscal damage and were randomly assigned to one of four treatment groups with varying doses of P188. ACL reconstruction was then performed using an autograft from the semitendinosus tendon. Animals were euthanized 1-month following trauma, meniscal tissue was assessed for changes in morphology, mechanical properties, and proteoglycan content. Femurs and tibias were scanned using microcomputed tomograph...
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Despite reconstruction surgery to repair a torn anterior cruciate ligament (ACL), patients often still show signs of post-traumatic osteoarthritis (PTOA) years following the procedure. The goal of this study was to document changes in the... more
Despite reconstruction surgery to repair a torn anterior cruciate ligament (ACL), patients often still show signs of post-traumatic osteoarthritis (PTOA) years following the procedure. The goal of this study was to document changes in the meniscus and subchondral bone due to closed-joint impact and surgical reconstruction in a lapine model. Animals received insult to the joint followed by surgical reconstruction of the ACL and partial meniscectomy. Following euthanasia of the animals at 1, 3, and 6-months post-impact, meniscal tissue was assessed for changes in morphology, mechanical properties and proteoglycan content. Femurs and tibias were scanned via micro-computed tomography to determine changes in bone quality, morphometry, and formation of osteophytes. Both the lateral and medial menisci showed severe degradation and tearing at all-time points, with higher degree of degeneration being observed at 6-months. Decreases in both the instantaneous and equilibrium modulus were documented in both menisci. Minimal changes were found in bone quality and morphometry, with most change documented in the tibia. Bones from the reconstructed limbs showed large volumes of osteophyte formations, with an increase in volume over time. The initial changes that were representative of PTOA may have been limited to the meniscus, but at later time points consistent changes due to the disease were seen in both tissues. This study, which builds on a previous study by this laboratory, suggests that the addition of surgical reconstruction of the ACL to our model was not sufficient to prevent the development of PTOA.