bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of MODIS Active Fire Detection Products Derived from Two Algorithms
Authors: Morisette Jeffrey T. , Giglio Louis , Csiszar Ivan , Setzer Alberto , Schroeder Wilfrid , Morton Douglas , Justice Christopher O.
Published: July 2005

Fire influences global change and tropical ecosystems through its connection to land-cover dynamics, atmospheric composition, and the global carbon cycle. As such, the climate change community, the Brazilian government, and the Large-Scale Biosphere–Atmosphere (LBA) Experiment in Amazonia are interested in the use of satellites to monitor and quantify fire occurrence throughout Brazil. Because multiple satellites and algorithms are being utilized, it is important to quantify the accuracy of the derived products. In this paper the characteristics of two fire detection algorithms are evaluated, both of which are applied to Terra’s Moderate Resolution Imagine Spectroradiometer (MODIS) data and with both operationally producing publicly available fire locations. The two algorithms are NASA’s operational Earth Observing System (EOS) MODIS fire detection product and Brazil’s Instituto Nacional de Pesquisas Espaciais (INPE) algorithm. Both algorithms are compared to fire maps that are derived independently from 30-m spatial resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery. A quantitative comparison is accomplished through logistic regression and error matrices. Results show that the likelihood of MODIS fire detection, for either algorithm, is a function of both the number of ASTER fire pixels within the MODIS pixel as well as the contiguity of those pixels. Both algorithms have similar omission errors and each has a fairly high likelihood of detecting relatively small fires, as observed in the ASTER data. However, INPE’s commission error is roughly 3 times more than that of the EOS algorithm.
The Influence of Topography on the Stability of Shelfbreak Fronts
Authors: Lozier M. Susan , Reed Mark S. C.
Published: July 2005

In an attempt to understand the degree to which the stability of a shelfbreak front, characterized by continuous horizontal and vertical shear, is affected by topography, a linear stability analysis was conducted for a range of frontal jets and bottom-slope configurations. Three-dimensional perturbations superposed on a continuously stratified shelfbreak front were investigated using linearized, hydrostatic primitive equations. For all model runs in the study, the frontal instability mode, which is the fastest-growing mode for a baroclinic flow, was not influenced by the bottom: Retrograde, prograde, and flat-bottom jets all share the same stability characteristics. In contrast, weakly baroclinic jets are strongly influenced by bottom topography. The presence of a bottom slope stabilizes prograde jets and destabilizes retrograde jets, a difference attributed to the orientation of the isopycnals relative to the bottom slope. Temporal and/or downstream changes in the bottom slope and/or background stratification are shown to produce sizeable changes in the instability of a weakly baroclinic jet.
Stability of the Global Ocean Circulation: Basic Bifurcation Diagrams
Authors: Dijkstra Henk A. , Weijer Wilbert
Published: July 2005

A study of the stability of the global ocean circulation is performed within a coarse-resolution general circulation model. Using techniques of numerical bifurcation theory, steady states of the global ocean circulation are explicitly calculated as parameters are varied. Under a freshwater flux forcing that is diagnosed from a reference circulation with Levitus surface salinity fields, the global ocean circulation has no multiple equilibria. It is shown how this unique-state regime transforms into a regime with multiple equilibria as the pattern of the freshwater flux is changed in the northern North Atlantic Ocean. In the multiple-equilibria regime, there are two branches of stable steady solutions: one with a strong northern overturning in the Atlantic and one with hardly any northern overturning. Along the unstable branch that connects both stable solution branches (here for the first time computed for a global ocean model), the strength of the southern sinking in the South Atlantic changes substantially. The existence of the multiple-equilibria regime critically depends on the spatial pattern of the freshwater flux field and explains the hysteresis behavior as found in many previous modeling studies.
The Short-Wave Limit of Linear Equatorial Kelvin Waves in a Shear Flow
Authors: Boyd John P.
Published: July 2005

The effects of latitudinal shear on equatorial Kelvin waves in the one-and-one-half-layer model are examined through a mixture of perturbation theory and numerical solutions. For waves proportional to exp(ikx), where k is the zonal wavenumber and x is longitude, earlier perturbation theories predicted arbitrarily large distortions in the limit k → ∞. In reality, the distortions are always finite but are very different depending on the sign of the equatorial jet. When the mean jet is westward, the Kelvin wave becomes very, very narrow. When the mean jet flows eastward, the Kelvin wave splits in two with peaks well off the equator and exponentially small amplitude at the equator itself. The phase speed is always a bounded function of k, asymptotically approaching a constant. This condition has important implications for the nonlinear behavior of Kelvin waves. Strong nonlinearity cannot be balanced by contracting longitudinal scale, as in the author’s earlier Korteweg–deVries theory for equatorial solitons: for sufficiently large amplitude, the Kelvin wave must always evolve to a front.
The Effect of a Bottom Shelf Front upon the Generation and Propagation of Near-Inertial Internal Waves in the Coastal Ocean
Authors: Davies Alan M. , Xing Jiuxing
Published: July 2005

A three-dimensional nonlinear baroclinic model in cross-sectional form is used to study the generation and propagation of wind-forced near-inertial internal waves in a coastal region in the presence of a bottom front. Initially calculations are performed with the front in an infinite domain region. By this means coastal effects are removed. The initial response is in terms of inertial oscillations in the surface layer. However, in the frontal area these are modified by interaction through the nonlinear momentum terms with regions of positive and negative vorticity associated with the alongfront flow. This leads to a change in amplitude, phase, and frequency of the inertial current, and a resulting Ekman pumping that drives near-inertial internal waves in the frontal region. On the positive vorticity side of the front these waves are at the superinertial frequency and rapidly propagate away. On the negative side they are at the subinertial frequency and are trapped and inertial energy leaks to depth. Calculations with a coastal boundary and no front show that the offshore propagation of near-inertial waves is similar to that found on the positive vorticity side of the front. This shows that in terms of superinertial internal wave generation and propagation the front acts in a similar manner to a coastal boundary. However, with a coastal boundary, inertial currents below the thermocline are phase shifted by 180° from those above. This phase shift is only found in the frontal case when the front is adjacent to a coast and is due to the no-normal-flow condition at the coast. For the case of a stratified region between the coast and the front, near-inertial energy is trapped in this region and is dissipated at a rate depending upon the local value of vertical eddy viscosity. The offshore spatial distribution of near-inertial internal waves is found to be independent of whether the coastal region is represented by a vertical wall or a more realistic sloping seabed. However, in the case of a weak coastal front, the near-frontal distribution of near-inertial energy is influenced by the horizontal spatial variability of stratification within the front.
The East Greenland Spill Jet*
Authors: Pickart Robert S. , Torres Daniel J. , Fratantoni Paula S.
Published: July 2005

High-resolution hydrographic and velocity measurements across the East Greenland shelf break south of Denmark Strait have revealed an intense, narrow current banked against the upper continental slope. This is believed to be the result of dense water cascading over the shelf edge and entraining ambient water. The current has been named the East Greenland Spill Jet. It resides beneath the East Greenland/Irminger Current and transports roughly 2 Sverdrups of water equatorward. Strong vertical mixing occurs during the spilling, although the entrainment farther downstream is minimal. A vorticity analysis reveals that the increase in cyclonic relative vorticity within the jet is partly balanced by tilting vorticity, resulting in a sharp front in potential vorticity reminiscent of the Gulf Stream. The other components of the Irminger Sea boundary current system are described, including a presentation of absolute transports.
Intensification of Ocean Fronts by Down-Front Winds
Authors: Thomas Leif N. , Lee Craig M.
Published: July 2005

Many ocean fronts experience strong local atmospheric forcing by down-front winds, that is, winds blowing in the direction of the frontal jet. An analytic theory and nonhydrostatic numerical simulations are used to demonstrate the mechanism by which down-front winds lead to frontogenesis. When a wind blows down a front, cross-front advection of density by Ekman flow results in a destabilizing wind-driven buoyancy flux (WDBF) equal to the product of the Ekman transport with the surface lateral buoyancy gradient. Destabilization of the water column results in convection that is localized to the front and that has a buoyancy flux that is scaled by the WDBF. Mixing of buoyancy by convection, and Ekman pumping/suction resulting from the cross-front contrast in vertical vorticity of the frontal jet, drive frontogenetic ageostrophic secondary circulations (ASCs). For mixed layers with negative potential vorticity, the most frontogenetic ASCs select a preferred cross-front width and do not translate with the Ekman transport, but instead remain stationary in space. Frontal intensification occurs within several inertial periods and is faster the stronger the wind stress. Vertical circulation is characterized by subduction on the dense side of the front and upwelling along the frontal interface and scales with the Ekman pumping and convective mixing of buoyancy. Cross-front sections of density, potential vorticity, and velocity at the subpolar front of the Japan/East Sea suggest that frontogenesis by down-front winds was active during cold-air outbreaks and could result in strong vertical circulation.
Differential Diffusion in Breaking Kelvin–Helmholtz Billows
Authors: Smyth W. D. , Nash J. D. , Moum J. N.
Published: July 2005

Direct numerical simulations are used to compare turbulent diffusivities of heat and salt during the growth and collapse of Kelvin–Helmholtz billows. The ratio of diffusivities is obtained as a function of buoyancy Reynolds number Reb and of the density ratio Rρ (the ratio of the contributions of heat and salt to the density stratification). The diffusivity ratio is generally less than unity (heat is mixed more effectively than salt), but it approaches unity with increasing Reb and also with increasing Rρ. Instantaneous diffusivity ratios near unity are achieved during the most turbulent phase of the event even when Reb is small; much of the Reb dependence results from the fact that, at higher Reb, the diffusivity ratio remains close to unity for a longer time after the turbulence decays. An explanation for this is proposed in terms of the Batchelor scaling for scalar fields. Results are interpreted in terms of the dynamics of turbulent Kelvin–Helmholtz billows, and are compared in detail with previous studies of differential diffusion in numerical, laboratory, and observational contexts. The overall picture suggests that the diffusivities become approximately equal when Reb exceeds O(102). The effect of Rρ is significant only when Reb is less than this value.
Impacts of Shortwave Penetration Depth on Large-Scale Ocean Circulation and Heat Transport
Authors: Sweeney Colm , Gnanadesikan Anand , Griffies Stephen M. , Harrison Matthew J. , Rosati Anthony J. , Samuels Bonita L.
Published: July 2005

The impact of changes in shortwave radiation penetration depth on the global ocean circulation and heat transport is studied using the GFDL Modular Ocean Model (MOM4) with two independent parameterizations that use ocean color to estimate the penetration depth of shortwave radiation. Ten to eighteen percent increases in the depth of 1% downwelling surface irradiance levels results in an increase in mixed layer depths of 3–20 m in the subtropical and tropical regions with no change at higher latitudes. While 1D models have predicted that sea surface temperatures at the equator would decrease with deeper penetration of solar irradiance, this study shows a warming, resulting in a 10% decrease in the required restoring heat flux needed to maintain climatological sea surface temperatures in the eastern equatorial Atlantic and Pacific Oceans. The decrease in the restoring heat flux is attributed to a slowdown in heat transport (5%) from the Tropics and an increase in the temperature of submixed layer waters being transported into the equatorial regions. Calculations were made using a simple relationship between mixed layer depth and meridional mass transport. When compared with model diagnostics, these calculations suggest that the slowdown in heat transport is primarily due to off-equatorial increases in mixed layer depths. At higher latitudes (5°–40°), higher restoring heat fluxes are needed to maintain sea surface temperatures because of deeper mixed layers and an increase in storage of heat below the mixed layer. This study offers a way to evaluate the changes in irradiance penetration depths in coupled ocean–atmosphere GCMs and the potential effect that large-scale changes in chlorophyll a concentrations will have on ocean circulation.
Dependence of Differential Mixing on N and Rρ
Authors: Merryfield William J.
Published: July 2005

Mechanisms and parameter dependence of differential mixing of heat and salt by ocean turbulence are investigated numerically by extending a previous study to examine dependence upon buoyancy frequency N and density gradient ratio Rρ. In these experiments a burst of turbulence mixes temperature T and pseudosalinity S having molecular diffusivity 0.1 times that of T across background vertical gradients of both quantities. In contrast to previous results, which found turbulent diffusivity ratios d = KS/KT < 1 at a fixed N, the present study finds that d > 1 when N = 0 and that d tends to approach this value as N → 0. In all cases considered, d is larger at high Rρ (buoyancy dominated by T) than at low Rρ (buoyancy dominated by S). It is shown that this tendency is consistent with differential mixing being largely due to preferential restratification of the slower-diffusing component S. This conclusion is reinforced by the finding that d scales linearly with a fractional restratification measure over a wide range of conditions.
Assessing the Rationales for Educational Reforms: An Examination of Policy Claims About Professional Development, Comprehensive Reform, and Direct Instruction
Authors: St. John Edward P. , Manset-Williamson Genevieve , Chung Choong-Geun , Michael Robert S.
Published: July 2005

Evaluation studies seldom examine whether the rationales used to argue for an educational reform actually hold up when empirical evidence is examined after the reform has been implemented. This article examines survey data from 3 years of analyses of early reading interventions to examine three rationales that were used to argue for the program. First, there was evidence to support the argument that teachers need time to collaborate about improving educational outcomes. This study found that 2 years of funding for early reading reforms provided a margin of difference for collaborative efforts among teachers to promote reading-related outcomes. Second, the argument that comprehensive reform strategies promote gains in student outcomes was also supported, but not all reform models had their intended effects. Finally, there was no evidence from this study that the direct/explicit approach to reading instruction improved student outcomes, although this claim merits more systematic study in the future.
Understanding Instructional Leadership Through the Mental Models of Three Elementary School Principals
Authors: Ruff William G. , Shoho Alan R.
Published: July 2005

Mental models are described and discussed as a means of communicating the underlying aspects of instructional leadership. An empirical study identifying the mental models of instructional leadership held by three urban elementary school principals at different stages in their careers was used to support the thesis. Using a collective case study design, the similarities and differences in mental models of a novice principal and two experienced principals, one of whom was an award winning principal, were examined. The results demonstrated differing levels of integration as well as variation regarding the conceptualization of instructional leadership. This study underscored the usefulness of the mental model concept in discussing instructional leadership.
The Fail-Safe Schools Challenge: Leadership Possibilities From High Reliability Organizations
Authors: Bellamy G. Thomas , Crawford Lindy , Marshall Laura Huber , Coulter Gail A.
Published: July 2005

As public policies increasingly hold schools responsible for preventing school failure, experiences of other organizations that must operate with high reliability may be helpful. This article builds on previous studies of high reliability organizations to inquire how their strategies might inform efforts to improve reliability in loosely coupled professional organizations such as schools. The article draws on features of high reliability organizations to propose a three-part framework for fail-safe schools that includes (a) efforts to improve normal operations, (b) early detection of learning problems, and (c) rapid recovery from those problems, together with the school structures and cultures needed to support all three. Without assuming that the exact strategies used in very different organizations will work in schools, the article explores how high reliability organizations might serve as a metaphor that poses new questions for research, policy, and practice associated with school improvement and student learning.
Hobbes and the Matter of Self-Consciousness
Authors: Frost Samantha
Published: July 2005

Observing that René Descartes’s dualistic philosophy haunts our conceptualization of matter, this essay argues that Thomas Hobbes develops a non-Cartesian materialism, which is to say that he articulates a materialism in which matter is not construed as essentially unthinking. Tracing his accounts of sense, perception, and thinking, this essay reconstructs Hobbes’s account of self-consciousness and proposes that in a subject conceived as wholly embodied, self-knowledge or self-awareness takes the form of memory. The essay elaborates how Hobbes’s account of self-consciousness as memory transforms our understanding both of the form taken by the subject’s self-mastery and of the relationship between the individual and the collective. It concludes by speculating about the implications of this account for our understanding of Hobbes’s theories of ethics and politics.
Performing Conscience
Authors: Turner Jack
Published: July 2005

Does Henry Thoreau have a positive politics? Depending on how one conceives of politics, answers will vary. Hannah Arendt famously portrayed Thoreau’s commitment to the sanctity of individual conscience as distinctly unpolitical. More recent commentators grant that Thoreau has a politics, but they characterize it as profoundly negative in character. This essay argues that Thoreau indeed sponsors a positive politics—a politics of performing conscience. The performance of conscience before an audience transforms the invocation of conscience from a personally political act into a publicly political one. The aim of the performance is to provoke one’s neighbors into a process of individual self-reform that will make them capable of properly vigilant democratic citizenship and conscientious political agitation. I establish this claim through a sustained reading of a relatively neglected text that deserves wider attention in political theory: Thoreau’s 1859 lecture defending insurrectionary activities by radical abolitionist John Brown.
Is Liberalism the Only Way Toward Democracy?
Authors: Ackerly Brooke A.
Published: July 2005

This article identifies a foundation for Confucian democratic political thought in Confucian thought. Each of the three aspects emphasized is controversial, but supported by views held within the historical debates and development of Confucian political thought and practice. This democratic interpretation of Confucian political thought leads to (1) an expectation that all people are capable of ren and therefore potentially virtuous contributors to political life; (2) an expectation that the institutions of political, social, and economic life function so as to develop the virtue of being a perfected human being; and (3) an expectation that there be public space for political criticism and for ongoing contestation over the duties and behaviors of individual leaders and citizens and over the functioning of the institutions that are to cultivate their behavior.
Decent Democratic Centralism
Authors: Angle Stephen C.
Published: July 2005

Are there any coherent and defensible alternatives to liberal democracy? The author examines the possibility that a reformed democratic centralism—the principle around which China’s current polity is officially organized—might be legitimate, according to both an inside and an outside perspective. The inside perspective builds on contemporary Chinese political theory; the outside perspective critically deploys Rawls’s notion of a “decent society” as its standard. Along the way, the author pays particular attention to the kinds and degree of pluralism a decent society can countenance, and to the specific institutions in China that might enable the realization of a genuine and/or decent democratic centralism. The author argues that by considering both inside and outside perspectives, and the degrees to which they inter-penetrate and critically inform one another, we can engage in a global philosophy that neither pre-judges alternative political traditions nor falls prey to false conceptual barriers.
Why Democracies Collapse: The Reasons for Democratic Failure and Success
Authors: Diskin Abraham , Diskin Hanna , Hazan Reuven Y.
Published: July 2005

Most studies of democratic stability are based within either the socioeconomic or the politico-institutional tradition, but usually not on both. This article combines the two approaches. In all, 11 variables associated with democratic stability are divided into four groups (institutional, societal, mediating, and extraneous) and examined in 30 cases of democratic collapse and 32 cases of stable democracies. Five variables prove to be the most influential on the fate of democracies. When a country scores negatively on four of these five variables it is almost doomed to collapse. Some of the variables prove to be correlated in an opposite way to that which has been suggested in the literature.
Sex-Based Differences in the Anthropometric Characteristics of the Anterior Cruciate Ligament and Its Relation to Intercondylar Notch Geometry
Authors: Chandrashekar Naveen , Slauterbeck James , Hashemi Javad
Published: July 2005

Background

A significantly higher rate of anterior cruciate ligament injuries occurs in women involved in sports activities compared to the corresponding male population. Reasons for this disparity are not well understood; however, sex-based differences in the geometry of the anterior cruciate ligament, its morphologic characteristics, and the intercondylar notch size have been cited as possible factors.

Hypotheses

(1) The anterior cruciate ligament in women has a shorter length, and smaller cross-sectional area and volume than that in men. (2) The female anterior cruciate ligament has a lower mass density. (3) Ligament size is proportional to notch width in both male and female populations.

Study Design

Descriptive laboratory study.

Methods

Using a 3-dimensional imaging system, the authors measured the geometric parameters, including length, area, and volume, of the anterior cruciate ligaments of 10 male and 10 female donors (all Caucasian). A digital image of the frontal plane of the knee flexed at 90° was used to measure notch size. After the ligament's removal from its attachment sites, its mass was measured using a digital balance. Geometric parameters, mass density, and notch size were compared based on sex. Correlation analyses between ligament size and body anthropometric characteristics, and between notch size and ligament size were performed.

Results

The anterior cruciate ligament in women was smaller in length, cross-sectional area, volume, and mass when compared to that in men. No significant difference in ligament mass density was found between the sexes. Also, no differences were found in notch geometry between male and female populations. A correlation between notch size and ligament size was found for men but not for women.

Conclusions

Because the densities of female and male anterior cruciate ligaments appear to be similar, the smaller ligament size in women may contribute to their having a higher rate of ligament injuries. Anterior cruciate ligament size increases in proportion to notch width in men but not in women.
Neuromuscular Control of the Knee during a Resisted Single-Limb Squat Exercise
Authors: Shields Richard K. , Madhavan Sangeetha , Gregg Emy , Leitch Jennifer , Petersen Ben , Salata Sara , Wallerich Stacey
Published: July 2005

Background

Closed kinetic chain exercises such as single-limb squats are preferred for knee rehabilitation. A complete understanding of the neuromuscular control of the knee during the single-limb squat is essential to increase the efficiency of rehabilitation programs.

Hypothesis

Performing a controlled single-limb squat with resistance to knee flexion and extension will increase the coactivation of the hamstring muscle group, thus reducing the quadriceps/hamstrings ratio.

Study Design

Descriptive laboratory study.

Methods

A total of 15 healthy human subjects (7 women, 8 men) performed controlled single-limb squats in a custom mechanical device that provided resistance to both flexion and extension. Subjects performed the task at 3 levels of resistance, set as a percentage of body weight. Surface electromyographic recordings from 7 muscles (gluteus medius, rectus femoris, vastus medialis oblique, vastus lateralis, biceps femoris, semitendinosus, and medial gastrocnemius) were collected during the task.

Results

Biceps femoris activity during knee flexion increased from approximately 12% maximum voluntary isometric contractions during low resistance (0% body weight) to approximately 27% maximum voluntary isometric contractions during high resistance (8% body weight). Although the quadriceps had greater activity than the hamstrings at all levels of resistance, the quadriceps/hamstrings ratio declined significantly with resistance (F2,27 = 29.05; P=. 012) from 3.0 at low resistance to 2.32 at the highest resistance.

Conclusions

Performing controlled resisted single-limb squats may help to simultaneously strengthen the quadriceps and facilitate coactivation of the hamstrings, thus reducing anterior tibial shear forces. The coactivation may also increase the dynamic control of the knee joint.

Clinical Relevance

The typical single-limb squat exercise performed in the clinic does not usually control for bidirectional resistance and knee joint excursion. As seen in this study, controlled single-limb squats at increased levels of resistance help to increase the coactivation of the hamstring muscles, which is essential to optimize neuromuscular control of the knee.
Arthroscopic Fixation of Osteochondritis Dissecans of the Knee
Authors: Makino Arturo , Muscolo D. Luis , Puigdevall Miguel , Costa-Paz Matias , Ayerza Miguel
Published: July 2005

Background

Optimal treatment of osteochondritis dissecans of the knee is still controversial.

Purpose

To review a group of patients with osteochondritis dissecans of the knee who were treated with arthroscopic compressive screw fixation and who were evaluated with magnetic resonance imaging studies and a second-look arthroscopic procedure at follow-up.

Study Design

Case series; level of evidence, 4.

Methods

A total of 14 patients (15 knees) with osteochondritis dissecans of the knee were treated with arthroscopic titanium Herbert screw fixation of the osteochondral fragment. A second-look arthroscopic procedure was performed to remove hardware and to evaluate fragment stability. At final follow-up, magnetic resonance imaging studies were used to evaluate potential healing of the subchondral bone. Outcomes were clinically evaluated at a mean follow-up of 50 months (range, 25-104 months) by the Lysholm score and by the International Knee Documentation Committee score.

Results

At second-look arthroscopy, 14 of 15 knees showed evidence of a stable fragment with an intact smooth surface. According to magnetic resonance imaging parameters, 14 knees showed evidence of a healing process of the osteochondral fragment. The average Lysholm score improved 18 points from a mean of 79 preoperatively to 97 postoperatively, and according to the International Knee Documentation Committee score, 13 of 15 knees showed a normal result.

Conclusion

This study suggests that magnetic resonance imaging parameters of a healed osteochondral fragment and patients with satisfactory functional results correspond with arthroscopic evidence of fragment stability. According to this study, arthroscopic fixation with compressive screws is an effective method of repair for osteochondritis dissecans of the knee.
Factors Correlated with Volleyball Spike Velocity
Authors: Forthomme Bénédicte , Croisier Jean-Louis , Ciccarone Guido , Crielaard Jean-Michel , Cloes Marc
Published: July 2005

Background

Spike effectiveness represents a determining element in volleyball. To compete at a high level, the player must, in particular, produce a spike characterized by a high ball velocity.

Hypothesis

Some muscular and physical features could influence ball velocity during the volleyball spike.

Study Design

Descriptive laboratory study.

Methods

A total of 19 male volleyball players from the 2 highest Belgian national divisions underwent an isokinetic assessment of the dominant shoulder and elbow. Ball velocity performance (radar gun) during a spike test, morphological feature, and jump capacity (ergo jump) of the player were measured. We tested the relationship between the isokinetic parameters or physical features and field performances represented by spike velocity. We also compared first-division and second-division player data.

Results

Spike velocity correlated significantly with strength performance of the dominant shoulder (internal rotators) and of the dominant elbow (flexors and extensors) in the concentric mode. Negative correlations were established with the concentric external rotator on internal rotator ratio at 400 deg/s and with the mixed ratio (external rotator at 60 deg/s in the eccentric mode on internal rotator at 240 deg/s in the concentric mode). Positive correlations appeared with both the volleyball players’ jump capacity and body mass index. First-division players differed from second-division players by higher ball velocity and increased jump capacity.

Conclusion

Some specific strength and physical characteristics correlated significantly with spike performance in high-level volleyball practice.

Clinical Relevance

Our results could provide useful information for training management and propose some reflections on injury prevention.
Analysis of Stored Osteochondral Allografts at the Time of Surgical Implantation
Authors: Allen R. Todd , Robertson Catherine M. , Pennock Andrew T. , Bugbee William D. , Harwood Frederick L. , Van W. Wong , Chen Albert C. , Sah Robert L. , Amiel David
Published: July 2005

Background

To date, the morphological, biochemical, and biomechanical characteristics of articular cartilage in osteochondral allografts that have been stored have not been fully described.

Hypothesis

Osteochondral allografts procured and stored commercially for a standard period as determined by tissue banking protocol will have compromised chondrocyte viability but preserved extracellular matrix quality.

Study Design

Controlled laboratory study.

Methods

Unused cartilage from 16 consecutive osteochondral allografts was sampled during surgery after tissue bank processing and storage. Ten grafts were examined for cell viability and viable cell density using confocal microscopy, proteoglycan synthesis via 35SO4 uptake, and glycosaminoglycan content and compared with fresh cadaveric articular cartilage. Biomechanical assessment was performed on the 6 remaining grafts by measuring the indentation stiffness of the cartilage.

Results

The mean storage time for the transplanted specimens was 20.3 ± 2.9 days. Chondrocyte viability, viable cell density, and 35SO4 uptake were significantly lower in allografts at implantation when compared to fresh, unstored controls, whereas matrix characteristics, specifically glycosaminoglycan content and biomechanical measures, were unchanged. In addition, chondrocyte viability in the stored allografts was preferentially decreased in the superficial zone of cartilage.

Conclusion

Human osteochondral allografts stored for a standard period (approximately 3 weeks) before implantation undergo decreases in cell viability, especially in the critically important superficial zone, as well as in cell density and metabolic activity, whereas matrix and biomechanical characteristics appear conserved. The exact clinical significance of these findings, however, is unknown, as there are no prospective studies examining clinical outcomes using grafts stored for extended periods.

Clinical Relevance

Surgeons who perform this procedure should understand the cartilage characteristics of the graft after 21 days of commercial storage in serum-free media.
Monopolar Radiofrequency Treatment of Partial-Thickness Cartilage Defects in the Sheep Knee Joint Leads to Extended Cartilage Injury
Authors: Kääb Max J. , Bail Herman J. , Rotter Andreas , Mainil-Varlet Pierre , apGwynn Iolo , Weiler Andreas
Published: July 2005

Background

The application of radiofrequency energy to smooth and stabilize the cartilage surface has become increasingly controversial. There is little knowledge on extended-term effects, such as cartilage viability.

Purpose

To analyze the effect of radiofrequency treatment on artificially created partial-thickness defects in the femoral cartilage of sheep knee joints 24 weeks after surgery.

Study Design

Controlled laboratory study.

Methods

Grade II cartilage surface defects on the medial and lateral femoral condyles were artificially created in sheep for in vivo analysis. The cartilage lesions were treated alternately on the lateral or the medial condyle using a monopolar radiofrequency probe. Radiofrequency treatment was performed in a freehand technique until surface smoothing without change of cartilage color was seen. At 24 weeks after surgery, cartilage samples were harvested and were processed for macroscopic and histological evaluation. To analyze the effect of radiofrequency at time zero, samples of sheep femoral condyle cartilage with and without artificially created clefts were treated in vitro with radiofrequency. Evaluation was performed by scanning electron and confocal microscopy.

Results

At 24 weeks after surgery, grade IV cartilage defects were detected in all radiofrequency-treated samples. The histological findings showed a central ulcer and dead chondrocytes in the radiofrequency-treated regions. The radiofrequency-treated cartilage revealed partial surface irregularities with partial-defect repair. After radiofrequency treatment in vitro, samples at time zero showed smoothing of the artificially created clefts, as seen by scanning electron microscopy. Confocal microscopy showed necrosis of chondrocytes over approximately one fourth of the upper cartilage thickness.

Conclusion

Even if chondrocyte death is seen only in approximately one fourth of the upper cartilage layers in the sheep femur after in vitro application, radiofrequency treatment can cause damage to cartilage 24 weeks after application.

Clinical Relevance

Caution is recommended in the application of monopolar radiofrequency energy by visual control to partialthickness cartilage defects. Irregular fronds of chondromalacia may be unattractive but represent viable articular cartilage. Using radiofrequency to obtain a more visually pleasing smooth surface may be counterproductive.
Effect of Patellar Tendon Shortening on Tracking of the Patella
Authors: Upadhyay Neil , Vollans Samuel R. , Seedhom Bahaa B. , Soames Roger W.
Published: July 2005

Background

Although 10% postoperative patellar tendon shortening after bone–patellar tendon–bone autograft reconstruction of the anterior cruciate ligament has been reported, there are no published studies assessing the effect of shortening on patellofemoral joint biomechanics under physiological loading conditions.

Purpose

To investigate the influence of patellar tendon shortening on patellofemoral joint biomechanics.

Study Design

Controlled laboratory study.

Methods

The authors evaluated the patellofemoral contact area, the location of contact, and the patellofemoral joint reaction force and contact stresses in 7 cadaveric knees before and after 10% patellar tendon shortening. Shortening was achieved using a specially designed device. Experimental conditions simulating those occurring during level walking were employed: physiological quadriceps loads and corresponding angles of tibial rotation were applied at 15 °, 30 °, and 60 ° flexion of the knee. Patellofemoral joint contact areas were measured before and after shortening using the silicone oil–carbon black powder suspension squeeze technique.

Results

After patellar tendon shortening, patellofemoral joint contact areas were displaced proximally on the patellar surface and distally on the femoral surface. Although the contact area increased by 18% at 15 ° of knee flexion (P=. 04), no significant change occurred at 30 ° or 60 ° of knee flexion (P>. 05). Patellofemoral contact stress remained unchanged after patellar tendon shortening (P>. 05) at each flexion angle.

Conclusion

Our results suggest that a 10% shortening of the patellar tendon does not alter patellar contact stresses during locomotion. It is not clear whether apparent changes in contact location in all positions and contact area at 15 ° would have clinical consequences.
Open Bankart Repair
Authors: Sachs Raymond A. , Williams Bradley , Stone Mary Lou , Paxton Liz , Kuney Mary
Published: July 2005

Background

The potential weakness of the open Bankart procedure is the takedown and repair of the subscapularis tendon. It is not known to what extent this part of the procedure affects the final result.

Hypothesis

The function of the subscapularis muscle after surgery will be related to the patient's perception of surgical success.

Study Design

Cohort study; Level of evidence, 2.

Methods

A total of 30 patients with traumatic anterior instability had an open Bankart repair by a single surgeon. These patients were observed for a mean of 4 years. At final follow-up, the patients filled out 3 self-assessment forms: the American Shoulder and Elbow Surgeons scale, the Western Ontario Shoulder Instability Index, and the Constant and Murley scale. An independent physician performed a complete physical examination. Strength testing of all muscle groups was performed and compared with the opposite normal side.

Results

Multiple factors were related to the patient's perception of the result. Only subscapularis function was found to have a statistically significant correlation. Of the patients, 23% had an incompetent subscapularis with a mean of 27% strength as compared with the opposite side. These patients had a positive lift-off test result and reported 57% good and excellent results; only 57% would have the surgery again. Of the patients, 77% had a normal functioning subscapularis with at least 80% strength as compared with the opposite side. These patients had a negative lift-off test result and had 91% good and excellent results; 100% would have the surgery again. The Western Ontario Shoulder Instability Index was the only scale that differentiated between a patient with subscapularis function and a patient without subscapularis function.

Conclusion

Postoperative subscapularis function was the most critical factor in determining the patient's perception of surgical success.

Clinical Relevance

It is likely that handling of the subscapularis tendon during surgery and protection of the subscapularis in the first weeks after surgery are critical to the success of the open Bankart repair.
The Effect of Lateral Cortex Disruption and Repair on the Stability of the Medial Opening Wedge High Tibial Osteotomy
Authors: Miller Bruce S. , Dorsey William O. P. , Bryant Cari R. , Austin John C.
Published: July 2005

Background

Medial opening wedge high tibial osteotomy is gaining popularity as a treatment option for medial compartment degenerative disease in the young, active patient. One of the potential technical pitfalls of this procedure is inadvertent disruption of the lateral tibial cortex during distraction at the osteotomy site.

Purpose

(1) To investigate the effect of lateral cortex disruption on stability during medial opening wedge high tibial osteotomy and (2) to evaluate 3 different methods of repair of the disrupted lateral cortex.

Study Design

Controlled laboratory study.

Methods

A total of 50 validated replicate tibias were evaluated in a medial opening wedge high tibial osteotomy model. Specimens were divided into 5 groups: (1) control, or intact lateral cortex (n = 10); (2) disrupted lateral cortex (n = 10); (3) lateral cortex repaired with 1 staple (n = 10); (4) lateral cortex repaired with 2 staples (n = 10); and (5) lateral cortex repaired with a periarticular plate and screws (n = 10). Specimens were placed in compression and torsion under physiologic loads, and stiffness and micromotion were calculated.

Results

Disruption of the lateral cortex resulted in a 58% reduction in axial stiffness and a 68% reduction in torsional stiffness compared to control specimens (P<. 05). Disruption of the lateral cortex also resulted in increased micromotion at the osteotomy site. All 3 methods of repair of the lateral cortex restored stiffness and micromotion values to those of the control group (P<. 05).

Conclusions

Instability at the osteotomy site may contribute to the high rate of delayed union or nonunion associated with medial opening wedge high tibial osteotomy. Repair of the lateral tibial cortex by each of these techniques restored stability to the osteotomy site in this replicate tibia model and might be effective in clinical use. However, more studies are needed to further explore the relationship between lateral cortex disruption and patient outcomes in the clinical setting before definitive conclusions can be drawn.
First-Time Inversion Ankle Ligament Trauma
Authors: Beynnon Bruce D. , Vacek Pamela M. , Murphy Darlene , Alosa Denise , Paller David
Published: July 2005

Background

Inversion ankle trauma is disabling, yet little is known regarding the incidence rate of first-time ankle sprains and how it is influenced by factors including sex, level of competition, and sport.

Hypothesis

The incidence rates of first-time ankle ligament sprains are influenced by sex, level of competition (high school vs college), and type of sports participation (basketball, soccer, lacrosse, and field hockey).

Study Design

Cohort study; Level of evidence, 2.

Methods

Between 1999 and 2003, high school and college athletes were evaluated before participation in their sports. Subjects were included in the study if they had not experienced a prior ankle or lower extremity injury and were then followed during participation in soccer, basketball, lacrosse, or field hockey to document their days of exposure to sport and injuries sustained. The relative risk associated with sex, level of competition, and sport was estimated by Cox regression.

Results

A total of 901 athletes had 50 680 person-days of exposure to sports, and 43 (4.8%) had an inversion injury that produced an ankle ligament sprain. Overall, the injury incidence rate was 0.85 sprains per 1000 person-days of exposure to sport. There were 0.68 and 0.97 ankle sprains per 1000 person-days of exposure to sport for the men and women, respectively. Although the risk of suffering an ankle sprain was higher for women than for men (relative risk, 1.51), the difference was not statistically significant (P=. 21) and was owing to the increased risk in female basketball athletes compared to male basketball athletes (relative risk, 4.11; P=. 045). Risk of injury was similar for the high school athletes in comparison to the college athletes (relative risk, 1.16). For the men, there was no difference in the risk of suffering an ankle sprain between the sports of basketball, soccer, and lacrosse, whereas for the women, the risk of suffering an ankle sprain was significantly greater during participation in basketball compared to lacrosse.

Conclusion

In this study of first-time ankle sprains, for most sports, the incidence rate of inversion injury is less than 1 per 1000 days of exposure to sport, a value lower than previously reported. Among female athletes, ankle injury is associated with type of sport. Risk is highest for female basketball athletes, who are at significantly greater risk than male basketball athletes and female lacrosse athletes. The risk of first-time ankle injury is similar for high school and college-level athletes.
Team Physicians in College Athletics
Authors: Steiner Mark E. , Quigley D. Bradford , Wang Frank , Balint Christopher R. , Boland Arthur L.
Published: July 2005

Background

There has been little documentation of what constitutes the clinical work of intercollegiate team physicians. Team physicians could be recruited based on the needs of athletes.

Hypothesis

A multidisciplinary team of physicians is necessary to treat college athletes. Most physician evaluations are for musculoskeletal injuries treated nonoperatively.

Study Design

Descriptive epidemiology study.

Methods

For a 2-year period, a database was created that recorded information on team physician encounters with intercollegiate athletes at a major university. Data on imaging studies, hospitalizations, and surgeries were also recorded. The diagnoses for physician encounters with all undergraduates through the university's health service were also recorded.

Results

More initial athlete evaluations were for musculoskeletal diagnoses (73%) than for general medical diagnoses (27%) (P<. 05). Four percent of musculoskeletal injuries required surgery. Most general medical evaluations were single visits for upper respiratory infections and dermatologic disorders, or multiple visits for concussions. Football accounted for 22% of all physician encounters, more than any other sport (P<. 05). Per capita, men and women sought care at an equal rate. In contrast, 10% of physician encounters with the general pool of undergraduates were for musculoskeletal diagnoses. Student athletes did not require a greater number of physician encounters than did the general undergraduate pool of students on a per capita basis.

Conclusion

Intercollegiate team physicians primarily treat musculoskeletal injuries that do not require surgery. General medical care is often single evaluations of common conditions and repeat evaluations for concussions.