Considering humans as habitat reveals evidence of successional disease ecology among human pathogens.

The realization that ecological principles play an important role in infectious disease dynamics has led to a renaissance in epidemiological theory. Ideas from ecological succession theory have begun to inform an understanding of the relationship between the individual microbiome and health but have not yet been applied to investigate broader, population-level epidemiological dynamics. We consider human hosts as habitat and apply ideas from succession to immune memory and multi-pathogen dynamics in populations. We demonstrate that ecologically meaningful life history characteristics of pathogens and parasites, rather than epidemiological features alone, are likely to play a meaningful role in determining the age at which people have the greatest probability of being infected. Our results indicate the potential importance of microbiome succession in determining disease incidence and highlight the need to explore how pathogen life history traits and host ecology influence successional dynamics. We conclude by exploring some of the implications that inclusion of successional theory might have for understanding the ecology of diseases and their hosts.

Flow similarity, stochastic branching, and quarter-power scaling in plants.

The origin of allometric scaling patterns that are multiples of one-fourth has long fascinated biologists. While not universal, quarter-power scaling relationships are common and have been described in all major clades. Several models have been advanced to explain the origin of such patterns, but questions regarding the discordance between model predictions and empirical data have limited their widespread acceptance. Notable among these is a fractal branching model that predicts power-law scaling of both metabolism and physical dimensions. While a power law is a useful first approximation to some data sets, nonlinear data compilations suggest the possibility of alternative mechanisms. Here, we show that quarter-power scaling can be derived using only the preservation of volume flow rate and velocity as model constraints. Applying our model to land plants, we show that incorporating biomechanical principles and allowing different parts of plant branching networks to be optimized to serve different functions predicts nonlinearity in allometric relationships and helps explain why interspecific scaling exponents covary along a fractal continuum. We also demonstrate that while branching may be a stochastic process, due to the conservation of volume, data may still be consistent with the expectations for a fractal network when one examines sub-trees within a tree. Data from numerous sources at the level of plant shoots, stems, and petioles show strong agreement with our model predictions. This theoretical framework provides an easily testable alternative to current general models of plant metabolic allometry.

Interobserver and Intraobserver Reliability in the Salter Classification of Avascular Necrosis of the Femoral Head in Developmental Dysplasia of the Hip.

BACKGROUND: Avascular necrosis (AVN) of the femoral head is a concerning complication that can result from treatments for developmental dysplasia of the hip (DDH). AVN can lead to degenerative osteoarthritis, persistent acetabular dysplasia, reduced function, and continuing hip pain. The incidence of AVN reported in the DDH literature is widely varied (0% to 73%). This variability may arise from lack of consensus on what constitutes true AVN in this patient population, and lack of clear criteria provided in studies reporting incidence rates. METHODS: A multicentre, prospective database of infants diagnosed with DDH between 2010 and 2014 from 0 to 18 months of age was analyzed for patients treated by closed reduction (CR). Twelve pediatric orthopaedic surgeons completed 2 rounds of AVN assessments. Deidentified anteroposterior radiographs at most recent follow-up were provided to surgeons along with patient age at radiographic assessment, length of follow-up, ands affected hip. Ten of 12 surgeons completed a third round of assessments where they were provided with 1 to 2 additional radiographs within the follow-up period. Radiographic criteria for total AVN described by Salter and colleagues were used. Surgeons rated the presence of AVN as "yes" or "no" and kappa values were calculated within and between rounds. RESULTS: A total of 69 hips in 60 patients were assessed for AVN a median of 22 months (range: 12 to 36) post-CR. Interobserver kappa values for rounds 1, 2, and 3 were 0.52 (range: 0.11 to 0.90), 0.61 (range: 0.21 to 0.90), and 0.53 (range: 0.10 to 0.79), respectively. Intraobserver agreement for AVN diagnosis was an average of 0.72 (range: 0.31 to 0.96). CONCLUSIONS: Despite using the most commonly referenced diagnostic criteria, radiographic diagnosis of AVN following CR in DDH patients demonstrated only moderate agreement across surgeons. The addition of sequential radiographs did not improve cross-observer reliability, and while substantial agreement was seen within observers, the range of intraobserver kappa values was large. LEVEL OF EVIDENCE: Level I-diagnostic study.

Ultrasound Characteristics of Clinically Dislocated But Reducible Hips With DDH.

BACKGROUND: Although ultrasound (US) is frequently used in diagnosis and management of infantile developmental dysplasia of the hip, precise ultrasonographic parameters of what constitutes a dislocation, subluxation etc remain poorly defined. The purpose of this study was (1) to describe the ultrasonographic characteristics of a large cohort of clinically dislocated but reducible hips and (2) to begin to develop ultrasonographic definitions for what constitutes a hip dislocation. METHODS: A retrospective review of prospectively collected data from an international multicenter study group on developmental dysplasia of the hip was conducted on all patients under 6 months of age with hip(s) that were dislocated at rest but reducible based on initial physical examination (ie, Ortolani positive). Femoral head coverage (FHC), alpha angle (α), and beta angle (ß) were measured on pretreatment US by the individual treating surgeon, and were recorded directly into the database. RESULTS: Based on 325 Ortolani positive hips, the median FHC on presentation was 10% with an interquartile range of 0% to 23%. A total of 126 of the 327 hips (39%) demonstrated 0% FHC. The 90th percentile was found to be at 33% FHC. Of 264 hips with sufficient α data, the median α was 43 degrees with an interquartile range from 37 to 49 degrees. The 90th percentile for α was at 54 degrees. A total of 164 hips had documented ß with a median of 66 degrees and an interquartile range of 57 to 79 degrees; the 90th percentile was at 94 degrees. CONCLUSIONS: Analysis of a large cohort of patients with dislocated but reducible hips reveals a median percent FHC of 10%, a median α of 43 degrees, and a median ß of 66 degrees on initial US. Using a threshold at the 90th percentile, a sensible ultrasonographic definition of a dislocated hip seems to be FHC≤33%, implying that FHC between 34% and 50% may be reasonably termed a subluxation. Although these findings are consistent with previous, smaller reports, further prospective research is necessary to validate these thresholds. LEVEL OF EVIDENCE: Level IV-diagnostic study.

Management of Irreducible Hip Dislocations in Infants With Developmental Dysplasia of the Hip Diagnosed Below 6 Months of Age.

BACKGROUND: Infants with dislocated irreducible (D/I) hips can be substantially harder to treat than infants with dislocated but reducible hips. The purpose of this study was to compare treatment methods and outcomes for infants with D/I hips in order to optimize management of this difficult patient cohort. METHODS: A multicenter prospective hip dysplasia study database was analyzed from 2010 to 2016. Infants aged below 6 months with clinically and radiologically confirmed D/I hips were included in the study. Teratological hips (syndromic/neuromuscular) were excluded. RESULTS: In total, 59 hips in 52 patients were included. All hips were clinically Ortolani negative and radiologically dislocated but irreducible on presentation and had at least 20 months of follow-up. Mean age at diagnosis was 1.9 months (range, 0.1 to 5.9 mo). There were 33 left hips, 12 right hips, and 14 bilateral hips (7 patients). In total, 48 of 59 hips were treated in Pavlik harness. The remainder were treated by alternative braces or primary closed or open reductions. Pavlik treatment was successful in 27 of 48 hips. Pavlik treatment was abandoned in 21 D/I hips, 3 due to femoral nerve palsy and the remainder due to failure to achieve reduction. There was no statistical correlation between Pavlik success and age at diagnosis (P=0.22), patient sex (P=0.61), or bilateral compared with unilateral D/I hips (P=0.07). Left hips were more likely to be successfully reduced in Pavlik harness than right hips (P=0.01). Five complications occurred: 3 patients developed femoral nerve palsy in Pavlik harness, while 2 patients developed avascular necrosis, both after failed Pavlik treatment and subsequent surgery. CONCLUSIONS: Pavlik harness treatment has been demonstrated to be a safe and sensible first-line treatment for infants with D/I hips. Left hips were more likely to be successfully reduced in Pavlik harness than right hips, but age, sex, and bilaterality were not correlated. The outcomes demonstrated from this multicentre prospective database inform management of this complex patient cohort. LEVEL OF EVIDENCE: Level II-prognostic study: less-quality prospective study.

Closed Reduction for Developmental Dysplasia of the Hip: Early-term Results From a Prospective, Multicenter Cohort.

BACKGROUND: Closed reduction (CR) is a common treatment for infantile developmental dysplasia of the hip. The purpose of this observational, prospective, multicenter study was to determine the early outcomes following CR. METHODS: Prospectively collected data from an international multicenter study group was analyzed for patients treated from 2010 to 2014. Baseline demographics, clinical exam, radiographic/ultrasonographic data, and history of previous orthotic treatment were assessed. At minimum 1-year follow-up, failure was defined as an IHDI grade 3 or 4 hip and/or need for open reduction. The incidence of avascular necrosis (AVN), residual dysplasia, and need for further surgery was assessed. RESULTS: A total of 78 patients undergoing CR for 87 hips were evaluated with a median age at initial reduction of 8 months (range, 1 to 20 mo). Of these, 8 hips (9%) were unable to be closed reduced initially. At most recent follow-up (median 22 mo; range, 12 to 36 mo), 72/79 initially successful CRs (91%) remained stable. The likelihood of failure was unaffected by initial clinical reducibility of the hip (P=0.434), age at initial CR (P=0.897), or previous treatment in brace (P=0.222). Excluding those hips that failed initial CR, 18/72 hips (25%) developed AVN, and the risk of osteonecrosis was unaffected by prereduction reducibility of the hip (P=0.586), age at CR (P=0.745), presence of an ossific nucleus (P=0.496), or previous treatment in brace (P=0.662). Mean acetabular index on most recent radiographs was 25 degrees (±6 degrees), and was also unaffected by any of the above variables. During the follow-up period, 8/72 successfully closed reduced hips (11%) underwent acetabular and/or femoral osteotomy for residual dysplasia. CONCLUSIONS: Following an initially successful CR, 9% of hips failed reduction and 25% developed radiographic AVN at early-term follow-up. History of femoral head reducibility, previous orthotic bracing, and age at CR did not correlate with success or chances of developing AVN. Further follow-up of this prospective, multicenter cohort will be necessary to establish definitive success and complication rates following CR for infantile developmental dysplasia of the hip. LEVEL OF EVIDENCE: Level II-prospective observational cohort.

Pavlik Harness Disease Revisited: Does Prolonged Treatment of a Dislocated Hip in a Harness Adversely Affect the α Angle?

BACKGROUND: Current dogma contends that prolonged treatment of a dislocated hip in Pavlik harness beyond 3 weeks will cause "Pavlik harness disease." To our knowledge, however, no previous studies have documented objective morphologic changes to the acetabulum from continued treatment of a persistently dislocated hip. METHODS: We retrospectively reviewed a consecutive series of infants with developmental dysplasia of the hip, below 6 months old, who failed Pavlik treatment from a single, tertiary-care pediatric hospital and a multicenter, international study group. Inclusion criteria were dislocated hips confirmed by ultrasound (both initially and at Pavlik termination) and a minimum of 2 ultrasounds during harness treatment at least 3 weeks apart. As a global measure of acetabular morphology, α angle (AA) was compared between initial and final ultrasound. The final means of obtaining successful hip reduction was recorded from the medical records. RESULTS: Forty-nine hips in 38 patients were identified. Median age at Pavlik initiation was 4 weeks (range, 0 to 18 wk); median time in harness was 6 weeks (range, 3 to 14 wk). Surprisingly, a mean of 4 degrees improvement in AA (95% CI, 2-6 degrees; P=0.001) was observed between first and final ultrasound. We found no difference in AA change between those in harness 3 to 5 weeks and those with prolonged wear >5 weeks (P=0.817). There was no significant association between change in AA and time in harness (P=0.545), age at Pavlik initiation (P=0.199), clinical reducibility of the hip (P=0.202), or initial percent femoral head coverage (P=0.956). Following harness failure, 22/49 hips (45%) were successfully treated with rigid abduction bracing, 16 (33%) by closed reduction/spica casting, and 10 (20%) by open reduction; 1 hip (2%) spontaneously reduced and required no further treatment. CONCLUSIONS: On the basis of the lengths of harness treatment in our series, most hips did not exhibit negative changes in the acetabular AA in response to prolonged treatment of a dislocated hip in harness. Furthermore, 80% of hips failing Pavlik treatment were successfully reduced through closed means, indicating that subsequent treatment was not compromised. LEVEL OF EVIDENCE: Level IV-retrospective case series.

Anatomy of the pedicled anterolateral thigh flap for phalloplasty in transitioning-males.

Incidence of transexualism and request for neophalloplasty is increasing yielding a current prevalence of trans-male in the USA of 1:2500. Surgeons have explored various techniques to improve desirable outcomes of neophallic construction, decrease the length of surgery, and minimize stigmatizing scars. The anterolateral thigh (ALT) flap is an alternative to the traditional radial forearm flap for patients who do not want a forearm scar. Surgical text descriptions were enhanced by the creation of new anatomic illustrations. Anatomy of the donor and recipient sites as well as the surgical technique leading to creation of the neophallus are demonstrated in detail with new relevant illustrations. The ALT flap is a skin, fat and fascia flap that is usually supplied by the descending branch of the lateral circumflex femoral vessels and the lateral femoral cutaneous nerve. However, variability in neurovascular supply does exist with important clinical implications. In the pedicled surgical procedure, neurovascular supply is left partly attached to the donor site ("pedicle") and simply transposed to the perineum, keeping the pedicle intact as a conduit to supply the tissue with blood and innervation. ALT flap offers clinical advantages of less obvious donor site concealable with clothing, decreased surgical time, preservation of erogenous sensation and vascular supply of the flap without microsurgical anastomosis of nerves and vessels, and good potential for urethroplasty. This surgery may be difficult in patients with thicker skin and more subcutaneous thigh fat. Clin. Anat, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Apparent Overinvestment in Leaf Venation Relaxes Leaf Morphological Constraints on Photosynthesis in Arid Habitats.

Leaf veins supply the mesophyll with water that evaporates when stomata are open to allow CO2 uptake for photosynthesis. Theoretical analyses suggest that water is optimally distributed in the mesophyll when the lateral distance between veins (dx) is equal to the distance from these veins to the epidermis (dy), expressed as dx:dy ≈ 1. Although this theory is supported by observations of many derived angiosperms, we hypothesize that plants in arid environments may reduce dx:dy below unity owing to climate-specific functional adaptations of increased leaf thickness and increased vein density. To test our hypothesis, we assembled leaf hydraulic, morphological, and photosynthetic traits of 68 species from the Eucalyptus and Corymbia genera (termed eucalypts) along an aridity gradient in southwestern Australia. We inferred the potential gas-exchange advantage of reducing dx beyond dy using a model that links leaf morphology and hydraulics to photosynthesis. Our observations reveal that eucalypts in arid environments have thick amphistomatous leaves with high vein densities, resulting in dx:dy ratios that range from 1.6 to 0.15 along the aridity gradient. Our model suggests that, as leaves become thicker, the effect of reducing dx beyond dy is to offset the reduction in leaf gas exchange that would result from maintaining dx:dy at unity. This apparent overinvestment in leaf venation may be explained from the selective pressure of aridity, under which traits associated with long leaf life span, high hydraulic and thermal capacitances, and high potential rates of leaf water transport confer a competitive advantage.

Optimal allocation of leaf epidermal area for gas exchange.

A long-standing research focus in phytology has been to understand how plants allocate leaf epidermal space to stomata in order to achieve an economic balance between the plant's carbon needs and water use. Here, we present a quantitative theoretical framework to predict allometric relationships between morphological stomatal traits in relation to leaf gas exchange and the required allocation of epidermal area to stomata. Our theoretical framework was derived from first principles of diffusion and geometry based on the hypothesis that selection for higher anatomical maximum stomatal conductance (gsmax ) involves a trade-off to minimize the fraction of the epidermis that is allocated to stomata. Predicted allometric relationships between stomatal traits were tested with a comprehensive compilation of published and unpublished data on 1057 species from all major clades. In support of our theoretical framework, stomatal traits of this phylogenetically diverse sample reflect spatially optimal allometry that minimizes investment in the allocation of epidermal area when plants evolve towards higher gsmax . Our results specifically highlight that the stomatal morphology of angiosperms evolved along spatially optimal allometric relationships. We propose that the resulting wide range of viable stomatal trait combinations equips angiosperms with developmental and evolutionary flexibility in leaf gas exchange unrivalled by gymnosperms and pteridophytes.

Evaluating general allometric models: interspecific and intraspecific data tell different stories due to interspecific variation in stem tissue density and leaf size.

The ability of general scaling models to capture the central tendency or dispersion in biological data has been questioned. In fact, the appropriate domain of such models has never been clearly articulated and they have been supported and challenged using both interspecific and/or intraspecific data. Here, we evaluate several simplifying assumptions and predictions of two prominent scaling models: West, Brown and Enquist's fractal model (WBE) and a null model of geometric similarity (GEOM). Using data for 53 herbaceous angiosperm species from the Songnen Grasslands of Northern China, we compared both the interspecific and intraspecific scaling relationships for plant geometry and biomass partitioning. Specifically, we considered biomass investment in shoots and leaves as well as related several traits not commonly collected in plant allometric analyses: shoot volume, leaf number, and mean leaf mass. At the interspecific level, we find substantial variation in regression slopes, and the simplifying assumptions of WBE and predictions of both the WBE and GEOM models do not hold. In contrast, we find substantial support for the WBE model at the intraspecific level, and to a lesser extent for GEOM. The differences between our results at interspecific and intraspecific levels are due to the fact that leaf size and stem tissue density vary considerably across species in contrast to the simplifying assumptions of WBE. These results highlight the domain within which simplifying model assumptions might be most appropriate, and suggest allometric models may be useful points of departure within some species, growth forms or taxonomic groups.

What Risk Factors and Characteristics Are Associated With Late-presenting Dislocations of the Hip in Infants?

BACKGROUND: Most infants with developmental dysplasia of the hip (DDH) are diagnosed within the first 3 months of life. However, late-presenting DDH (defined as a diagnosis after 3 months of age) does occur and often results in more complex treatment and increased long-term complications. Specific risk factors involved in late-presenting DDH are poorly understood, and clearly defining an associated set of factors will aid in screening, detection, and prevention of this condition. QUESTIONS/PURPOSES: Using a multicenter database of patients with DDH, we sought to determine whether there were differences in (1) risk factors or (2) the nature of the dislocation (laterality and joint laxity) when comparing patients with early versus late presentation. METHODS: A retrospective review of prospectively collected data from a multicenter database of patients with dislocated hips was conducted from 2010 to 2014. Baseline demographics for fetal presentation (cephalic/breech), birth presentation (vaginal/cesarean), birth weight, maternal age, maternal parity, gestational age, family history, and swaddling history of patients were compared among nine different sites for patients who were enrolled at age younger than 3 months and those enrolled between 3 and 18 months of age. A total of 392 patients were enrolled at baseline between 0 and 18 months of age with at least one dislocated hip. Of that group, 259 patients were younger than 3 months of age and 133 were 3 to 18 months of age. The proportion of patients with DDH who were enrolled and followed at the nine participating centers was 98%. RESULTS: A univariate/multivariate analysis was performed comparing key baseline demographics between early- and late-presenting patients. After controlling for relevant confounding variables, two variables were identified as risk factors for late-presenting DDH as compared with early-presenting: cephalic presentation at birth and swaddling history. Late-presenting patients were more likely to have had a cephalic presentation than early-presenting patients (88% [117 of 133] versus 65% [169 or 259]; odds ratio [OR], 5.366; 95% confidence interval [CI], 2.44-11.78; p < 0.001). Additionally, late-presenting patients were more likely to have had a history of swaddling (40% [53 of 133] versus 25% [64 of 259]; OR, 2.053; 95% CI, 1.22-3.45; p = 0.0016). No difference was seen for sex (p = 0.63), birth presentation (p = 0.088), birth weight (p = 0.90), maternal age (p = 0.39), maternal parity (p = 0.54), gestational age (p = 0.42), or family history (p = 0.11) between the two groups. Late presenters were more likely to present with an irreducible dislocation than early presenters (56% [82 of 147 hips] versus 19% [63 of 333 hips]; OR, 5.407; 95% CI, 3.532-8.275; p < 0.001) and were less likely to have a bilateral dislocation (11% [14 of 133] versus 28% [73 of 259]; OR, 0.300; 95% CI, 0.162-0.555; p = 0.002). CONCLUSIONS: Those presenting with DDH after 3 months of age have fewer of the traditional risk factors for DDH (such as breech birth), which may explain the reason for a missed diagnosis at a younger age. In addition, swaddling history was more common in late-presenting infants. A high index of suspicion for DDH should be maintained for all infants, not just those with traditional risk factors for DDH. Further investigation is required to determine if swaddling is a risk factor for the development of hip dislocations in older infants. More rigorous examination into traditional screening methods should also be performed to determine whether current screening is sufficient and whether late-presenting dislocations are present early and missed or whether they develop over time. LEVEL OF EVIDENCE: Level III, retrospective study.

What Is the Impact of Center Variability in a Multicenter International Prospective Observational Study on Developmental Dysplasia of the Hip?

BACKGROUND: Little information exists concerning the variability of presentation and differences in treatment methods for developmental dysplasia of the hip (DDH) in children < 18 months. The inherent advantages of prospective multicenter studies are well documented, but data from different centers may differ in terms of important variables such as patient demographics, diagnoses, and treatment or management decisions. The purpose of this study was to determine whether there is a difference in baseline data among the nine centers in five countries affiliated with the International Hip Dysplasia Institute to establish the need to consider the center as a key variable in multicenter studies. QUESTIONS/PURPOSES: (1) How do patient demographics differ across participating centers at presentation? (2) How do patient diagnoses (severity and laterality) differ across centers? (3) How do initial treatment approaches differ across participating centers? METHODS: A multicenter prospective hip dysplasia study database was analyzed from 2010 to April 2015. Patients younger than 6 months of age at diagnosis were included if at least one hip was completely dislocated, whereas patients between 6 and 18 months of age at diagnosis were included with any form of DDH. Participating centers (academic, urban, tertiary care hospitals) span five countries across three continents. Baseline data (patient demographics, diagnosis, swaddling history, baseline International Hip Dysplasia Institute classification, and initial treatment) were compared among all nine centers. A total of 496 patients were enrolled with site enrolment ranging from 10 to 117. The proportion of eligible patients who were enrolled and followed at the nine participating centers was 98%. Patient enrollment rates were similar across all sites, and data collection/completeness for relevant variables at initial presentation was comparable. RESULTS: In total, 83% of all patients were female (410 of 496), and the median age at presentation was 2.2 months (range, 0-18 months). Breech presentation occurred more often in younger (< 6 months) than in older (6-18 months at diagnosis) patients (30% [96 of 318] versus 9% [15 of 161]; odds ratio [OR], 4.2; 95% confidence interval [CI], 2.3-7.5; p < 0.001). The Australia site was underrepresented in breech presentation in comparison to the other centers (8% [five of 66] versus 23% [111 of 479]; OR, 0.3, 95% CI, 0.1-0.7; p = 0.034). The largest diagnostic category was < 6 months, dislocated reducible (51% [253 of 496 patients]); however, the Australia and Boston sites had more irreducible dislocations compared with the other sites (ORs, 2.1 and 1.9; 95% CIs, 1.2-3.6 and 1.1-3.4; p = 0.02 and 0.015, respectively). Bilaterality was seen less often in older compared with younger patients (8% [seven of 93] versus 26% [85 of 328]; p < 0.001). The most common diagnostic group was Grade 3 (by International Hip Dysplasia Institute classification), which included 58% (51 of 88) of all classified dislocated hips. Splintage was the primary initial treatment of choice at 80% (395 of 496), but was far more likely in younger compared with older patients (94% [309 of 328] versus 18% [17 of 93]; p < 0.001). CONCLUSIONS: With the lack of strong prognostic indicators for DDH identified to date, the center is an important variable to include as a potential predictor of treatment success or failure.

Estimates of leaf vein density are scale dependent.

Leaf vein density (LVD) has garnered considerable attention of late, with numerous studies linking it to the physiology, ecology, and evolution of land plants. Despite this increased attention, little consideration has been given to the effects of measurement methods on estimation of LVD. Here, we focus on the relationship between measurement methods and estimates of LVD. We examine the dependence of LVD on magnification, field of view (FOV), and image resolution. We first show that estimates of LVD increase with increasing image magnification and resolution. We then demonstrate that estimates of LVD are higher with higher variance at small FOV, approaching asymptotic values as the FOV increases. We demonstrate that these effects arise due to three primary factors: (1) the tradeoff between FOV and magnification; (2) geometric effects of lattices at small scales; and; (3) the hierarchical nature of leaf vein networks. Our results help to explain differences in previously published studies and highlight the importance of using consistent magnification and scale, when possible, when comparing LVD and other quantitative measures of venation structure across leaves.

Isometric partitioning of hydraulic conductance between leaves and stems: balancing safety and efficiency in different growth forms and habitats.

Recent advances in modelling the architecture and function of the plant hydraulic network have led to improvements in predicting and interpreting the consequences of functional trait variation on CO2 uptake and water loss. We build upon one such model to make novel predictions for scaling of the total specific hydraulic conductance of leaves and shoots (kL and kSH , respectively) and variation in the partitioning of hydraulic conductance. Consistent with theory, we observed isometric (slope = 1) scaling between kL and kSH across several independently collected datasets and a lower ratio of kL and kSH , termed the leaf-to-shoot conductance ratio (CLSCR ), in arid environments and in woody species. Isometric scaling of kL and kSH supports the concept that hydraulic design is coordinated across the plant. We propose that CLSCR is an important adaptive trait that represents the trade-off between efficiency and safety at the scale of the whole plant.

Reliability of a New Radiographic Classification for Developmental Dysplasia of the Hip.

BACKGROUND: Existing radiographic classification schemes (eg, Tönnis criteria) for DDH quantify the severity of disease based on the position of the ossific nucleus relative to Hilgenreiner's and Perkin's lines. By definition, this method requires the presence of an ossification centre, which can be delayed in appearance and eccentric in location within the femoral head. A new radiographic classification system has been developed by the International Hip Dysplasia Institute (IHDI), which uses the mid-point of the proximal femoral metaphysis as a reference landmark, and can therefore be applied to children of all ages. The purpose of this study was to compare the reliability of this new method with that of Tönnis, as the first step in establishing its validity and clinical utility. METHODS: Twenty standardized anteroposterior pelvic radiographs of children with untreated DDH were selected purposefully to capture the spectrum of age (range, 3 to 32 mo) at presentation and disease severity. Each of the hips was classified separately by the IHDI and Tönnis methods by 6 experienced pediatric orthopaedists from the United States, Canada, Mexico, United Kingdom, and by 2 orthopaedic senior residents. The inter-rater reliability was tested using the Intra Class Correlation coefficient (ICC) to measure concordance between raters. RESULTS: All 40 hips were classifiable by the IHDI method by all raters. Ten of the 40 hips could not be classified by the Tönnis method because of the absence of the ossific nucleus on one or both sides. The ICC (95% confidence interval) for the IHDI method for all raters was 0.90 (0.83-0.95) and 0.95 (0.91-0.98) for the right and left hips, respectively. The corresponding ICCs for the Tönnis method were 0.63 (0.46-0.80) and 0.60 (0.43-0.78), respectively. There was no significant difference between the ICCs of the 6 experts and 2 trainees. CONCLUSIONS: The IHDI method of classification has excellent inter-rater reliability, both among experts and novices, and is more widely applicable than the Tönnis method as it can be applied even when the ossification centre is absent. LEVEL OF EVIDENCE: Level II (diagnostic).

Costs and benefits of reticulate leaf venation.

BACKGROUND: Recent theoretical and empirical work has identified redundancy as one of the benefits of the reticulate form in the evolution of leaf vein networks. However, we know little about the costs of redundancy or how those costs depend on vein network geometry or topology. Here, we examined both costs and benefits to redundancy in 339 individual reticulate leaf networks comprising over 3.5 million vein segments. We compared levels of costs and benefits within reticulate networks to those within analogous networks without loops known as Maximum Spanning Trees (MSTs). RESULTS: We show that network robustness to varying degrees of simulated damage is positively correlated with structural indices of redundancy. We further show that leaf vein networks are topologically, geometrically and functionally more redundant than are MSTs. However, increased redundancy comes with minor costs in terms of increases in material allocation or decreases in conductance. We also show that full networks do not markedly decrease the distance to non-vein tissue in comparison to MSTs. CONCLUSIONS: These results suggest the evolutionary transition to the reticulate type of networks found in modern Angiosperm flora involved a relatively minor increase in material and conductance costs with significant benefits in terms of network redundancy.

Nighttime bracing versus observation for early adolescent idiopathic scoliosis.

BACKGROUND: Spinal bracing is widely utilized in patients with moderate severity adolescent idiopathic scoliosis with the goal of preventing curve progression and therefore preventing the need for surgical correction. Bracing is typically initiated in patients with a primary curve angle between 25 and 40 degrees, who are Risser sign 0 to 2 and <1-year postmenarchal. The purpose of this study is to determine whether nighttime bracing using a Charleston bending brace is effective in preventing progression of smaller curves (15 to 25 degrees) in skeletally immature, premenarchal female patients relative to current standard of care (observation for curves <25 degrees). METHODS: Premenarchal, Risser 0 female patients presenting to 2 pediatric orthopaedic specialty practices for evaluation of idiopathic scoliosis with Cobb angle measurements between 15 and 25 degrees were selected. They were randomized by location to receive nighttime bending brace treatment or observation. Patients in the observation group were converted to fulltime TLSO wear if they progressed to >25 degrees primary curve Cobb angle. Curve progression was monitored with minimum 2-year follow-up. RESULTS: Sixteen patients in the observation group and 21 patients in the bracing group completed 2-year follow-up. All patients in the observation group progressed to fulltime bracing threshold. In the nighttime bracing group, 29% of the patients did not progress to 25 degrees primary curve magnitude. Rate of progression to surgical magnitude was similar in the 2 groups. CONCLUSIONS: Risser 0 patients presenting with mild idiopathic scoliosis are at high risk for progression to >25 degrees primary curve magnitude. Treatment with the Charleston nighttime bending brace may reduce progression to full-time bracing threshold. No difference in progression to surgical intervention was shown between nighttime bracing and observation for small curves. LEVEL OF EVIDENCE: Level II--therapeutic study (prospective comparative study).

Mixed-species flock sizes and compositions influence flock members' success in three field experiments with novel feeders.

Mixed-species groups and aggregations are quite common and may provide substantial fitness-related benefits to group members. Individuals may benefit from the overall size of the mixed-species group or from the diversity of species present, or both. Here we exposed mixed-species flocks of songbirds (Carolina chickadees, Poecile carolinensis, tufted titmice, Baeolophus bicolor, and the satellite species attracted to these two species) to three different novel feeder experiments to assess the influence of mixed-species flock size and composition on ability to solve the feeder tasks. We also assessed the potential role of habitat density and traffic noise on birds' ability to solve these tasks. We found that likelihood of solving a novel feeder task was associated with mixed-species flock size and composition, though the specific social factor involved depended on the particular species and on the novel feeder. We did not find an influence of habitat density or background traffic noise on likelihood of solving novel feeder tasks. Overall, our results reveal the importance of variation in mixed-species group size and diversity on foraging success in these songbirds.

Biological scaling: does the exception prove the rule?

Reich et al. report that the whole-plant respiration rate, R, in seedlings scales linearly with plant mass, M, so that R=C(R)M(theta) when theta approximately 1, in which c(R) is the scaling normalization and theta is the scaling exponent. They also state that because nitrogen concentration (N) is correlated with c(R), variation in N is a better predictor of R than M would be. Reich et al. and Hedin incorrectly claim that these "universal" findings question the central tenet of metabolic scaling theory, which they interpret as predicting theta = (3/4), irrespective of the size of the plant. Here we show that these conclusions misrepresent metabolic scaling theory and that their results are actually consistent with this theory.