Low reoperation rate after fixation of displaced femoral neck fractures with the femoral neck system (FNS).

PURPOSE: Operative fixation of femoral neck fractures (FNFs) remains challenging. Complications are not infrequent, especially in displaced patterns. Numerous fixation techniques have been previously described in the literature; however, there remains a paucity of data regarding outcomes of these injuries treated with the femoral neck system (FNS). METHODS: Patients with a displaced FNF (OTA/AO 31B) treated with the FNS at a single level 1 academic trauma center between 1/1/2019 and 1/1/2023 were identified. Radiographs were reviewed to assess fracture displacement, location, and characteristics. Patient records were further reviewed to assess for complications, reoperations, and osseous union. RESULTS: Forty-three patients (65% male) with 44 FNFs were identified with a mean age of 35.0 years (range, 13-61 years). Two patients developed a deep infection requiring surgical debridement, four patients underwent a total hip arthroplasty, and one patient underwent a valgus intertrochanteric osteotomy for nonunion. There were three cases of femoral head AVN. Mean follow-up was 482.5 days among all patients, and 36 fractures had at least 6 months of follow-up or reached bony union. CONCLUSIONS: Here, we present a series of patients treated with the FNS for internal fixation and report a 18% reoperation rate. This is lower than the average rate that has been previously reported in similar patient populations in the literature treated with alternative methods of internal fixation. Thus, the FNS appears to be a safe and effective option for treatment of these injuries.

Does local fat thickness correlate with post-operative infection in open reduction and internal fixation of acetabulum fractures?

PURPOSE: Obesity is an epidemic which increases risk of many surgical procedures. Previous studies in spine and hip arthroplasty have shown that fat thickness measured on preoperative imaging may be as or more reliable in assessment of risk of post-operative infection and/or wound complications than body mass index (BMI). We hypothesized that, similarly, increased local fat thickness at the surgical site is a predictor of wound complication in acetabulum fracture surgery. METHODS: Patients who underwent open reduction and internal fixation (ORIF) of an acetabulum fracture through a Kocher-Langenbeck (K-L) approach at a single institution from 2013 to 2020 were identified. Pre-operative CT scans were used to measure fat thickness from the skin to the greater trochanter in line with the surgical approach. Post-operative infections and wound complications were recorded and associated with fat thickness and BMI. RESULTS: 238 patients met inclusion criteria. 12 patients had either infection or a wound complication (5.0%). There was no significant association with BMI or preoperative fat thickness on post-operative infection or wound complication (p-value 0.73 and 0.86). CONCLUSIONS: There is no statistically significant association of post-operative infection or wound complications in patients with increased soft tissue thickness or increased BMI. ORIF of acetabulum fractures through a K-L approach can be performed safely in patients with large subcutaneous fat thickness and high BMI with low risk of infection or wound complications.

Assessment of sacral osseous fixation pathways for same-level dual transiliac-transsacral screw insertion.

INTRODUCTION: The purpose of this study is to (1) describe a pre-operative planning technique using non-reformatted CT images for insertion of multiple transiliac-transsacral (TI-TS) screws at a single sacral level, (2) define the parameters of a sacral osseous fixation pathway (OFP) that will allow for insertion of two TI-TS screws at a single level, and (3) identify the incidence of sacral OFPs large enough for dual-screw insertion in a representative patient population. METHODS: Retrospective review at a level-1 academic trauma center of a cohort of patients with unstable pelvic injuries treated with two TI-TS screws in the same sacral OFP, and a control cohort of patients without pelvic injuries who had CT scans for other reasons. RESULTS: Thirty-nine patients had two TI-TS screws at S1. Eleven patients, all with dysmorphic osteology, had two TI-TS screws at S2. The average pathway size in the sagittal plane at the level the screws were placed was 17.2 mm in S1 vs 14.4 mm in S2 (p = 0.02). Twenty-one patients (42%) had screws that were intraosseous and 29 (58%) had part of a screw that was juxtaforaminal. No screws were extraosseous. The average OFP size of intraosseous screws was 18.1 mm vs. 15.5 mm for juxtaforaminal screws (p = 0.02). Fourteen millimeters was used as a guide for the lower limit of the OFP for safe dual-screw fixation. Overall, 30% of S1 or S2 pathways were ≥ 14 mm in the control group, with 58% of control patients having at least one of the S1 or S2 pathways ≥ 14 mm. CONCLUSIONS: OFPs ≥ 7.5 mm in the axial plane and 14 mm in the sagittal plane on non-reformatted CT images are large enough for dual-screw fixation at a single sacral level. Overall, 30% of S1 and S2 pathways were ≥ 14 mm and 58% of control patients had an available OFP in at least one sacral level.

Oblique anterior pelvic external fixator for intraoperative reduction of rotationally unstable pelvic ring injuries.

Incomplete sacroiliac joint injuries are often associated with external rotation and extension deformities on the injured hemipelvis. To appropriately correct this deformity, an oblique reduction force from caudal to cranial and lateral to medial is helpful. These injuries are often associated with traumatic disruption of the pubic symphysis. However, in injuries without traumatic disruption to the pubic symphysis, a two-pin oblique anterior external fixator can be used to obtain and maintain reduction of the sacroiliac joint, while percutaneous fixation is subsequently placed. Through a small case series and three specific patient examples, we demonstrate that the oblique anterior external fixator frame is a simple and effective strategy with the reduction and stabilization process of these multiplanar hemipelvis deformities.

Percutaneous sacral screw fixation alone sufficient for mildly displaced U-type sacral fractures with preserved osseous fixation pathways.

PURPOSE: To describe U-type sacral fracture characteristics amenable to percutaneous sacral screw fixation. METHODS: U-type sacral fractures were identified from a trauma registry at a level 1 trauma center from 2014 to 2020. Patient demographics, injury mechanism, fracture characteristics, and fixation construct were retrospectively retrieved. Associations between fracture pattern and surgical fixation were identified. RESULTS: 82 U-type sacral fractures were reviewed. Six treated with lumbopelvic fixation (LPF) and 76 were treated with percutaneous sacral screws (PSS) alone. Patients receiving LBF had greater sacral fracture displacement in coronal, sagittal, and axial planes compared to patients receiving PSS alone (P < 0.05), negating osseous fixation pathways. All patients went onto sacral union and there were no implant failures or unplanned reoperations for either group. CONCLUSION: If osseous fixation pathways are present, U-type sacral fractures can be successfully treated with percutaneous sacral screws. LPF may be indicated in more displaced fractures with loss of spinopelvic alignment. Both techniques for U-type sacral fractures result in reliable fixation and healing without reoperations.

Superior gluteal artery injury risk from third sacral segment transsacral screw insertion.

OBJECTIVES: Iliosacral (IS) and transsacral (TS) screws are commonly used to stabilize pelvic ring injuries. The course of the superior gluteal artery (SGA) can be close to implant insertion paths. The third sacral segment (S3) has been described as a viable osseous fixation pathway (OFP) but the proximity of the SGA to the S3 screw path is unknown. METHODS: Fifty uninjured patients with contrasted pelvic computed tomograms (CTA) were identified with an S3 path large enough for a 7.0 mm TS screw. Starting sites for S1 IS or TS, S2 and S3 TS screws were located on the volume rendered lateral CTA image and transferred onto the surface rendered 3D CTA with the SGA clearly visible. The distance from screw start sites to the SGA was measured. A distance less than 3.5 mm was considered likely for injury. RESULTS: The average distances from screw start sites to the SGA were 23.0 ± 7.9 mm for S1 IS screws, 14.3 ± 6.4 mm for S2 TS screws and 25.9 ± 6.5 mm for S3 TS screws. No S1 IS screws, 5 S2 TS screws (10%), and no S3 TS screws were projected to cause injury to the SGA. CONCLUSIONS: The osseous start site and soft tissue path for an S3 TS screw is remote from the SGA. The S1 IS and S3 TS pathways are further away from the SGA while the S2 TS pathway is closer and may theoretically pose a higher injury risk in patients with an available S3 OFP.

Posterior pelvic ring bone density with implications for percutaneous screw fixation.

BACKGROUND: Although the second (S2) and third (S3) sacral segments have been established as potential osseous fixation pathways for screw fixation, the S2 body has been demonstrated to have inferior bone density when compared to the body of the first (S1) sacral segment. Caution regarding the use of iliosacral screws at this level has been advised as a result. As transiliac-transsacral screws traverse the lateral cortices of the posterior pelvis, they may be relying on bone with superior density for purchase, which could obviate this concern. The objective of this study was to compare the bone density of the posterior ilium and sacroiliac joint to that of the sacral body at the first (S1), second (S2), and third (S3) sacral levels. MATERIALS AND METHODS: A retrospective case series was performed, reviewing the CT scans of 100 patients without prior pelvic trauma. Each CT was confirmed to have available osseous fixation pathways at the first (S1), second (S2), and third (S3) sacral segments. The bone density of the posterior ilium/sacroiliac joint (PISJ) and sacral body (SB) was measured using the embedded standardized Hounsfield units (HU) tool at each sacral level. RESULTS: The average S2 PISJ bone density (320.1) was significantly higher than the S1 (286.5) and S3 (278.9) PISJ (p < 0.0001) and S1 and S3 PISJ was not statistically different. The S1 sacral body bone density (231.1) was significantly higher than the S2 (182.1) and S3 (126.8) bone density (p < 0.0001). The PISJ bone density is greater than the sacral body at every sacral level (p < 0.0001). CONCLUSION: The S2 PISJ bone density is significantly greater than S1. The S1, S2, and S3 PISJ bone density is greater than the sacral body at all sacral levels, and the S1 body has higher bone density than the S2 and S3 bodies. These differences in bone density may have implications for the stability of posterior pelvic ring fixation constructs with regard to screw purchase. LEVEL OF EVIDENCE: Level III-Case cohort series.

Dose-Area Product-to-Effective Dose Conversion Coefficients for Pelvic Radiography Using a Monte Carlo Program.

OBJECTIVE. The purpose of this study was to determine dose-area product-to-effective dose (DAP/E) conversion coefficients for a five-view pelvic radiograph series. DAP/E conversion coefficients may be used for radiation dose optimization when designing institutional protocols for pelvic trauma evaluation. MATERIALS AND METHODS. We conducted a retrospective record review of 25 patients at a level 1 trauma center who had sustained pelvic fractures and required a five-view pelvic radiograph series during workup. E values given in International Commission on Radiological Protection Publication 103 were simulated with a PC-based Monte Carlo program in conjunction with anthropomorphic phantoms adjusted on the basis of patient height and weight. Inputs included tube voltage (in kV), tube filtration (in millimeters of aluminum), anode angle, x-ray beam collimation, geometric distances, and angle of projection for each radiograph in the series. An incident polychromatic x-ray spectrum was generated and matched to the corresponding DAP values of each radiograph, and regression analysis was performed for the DAP/E conversion coefficients. RESULTS.E was strongly correlated with DAP independent from body mass index, with a mean global DAP/E conversion coefficient of 0.0125 mSv/dGy · cm2 for all radiographs (R2 = 0.95). Mean DAP/E conversion coefficients were 0.0133, 0.0110, 0.0143, 0.0113, and 0.0101 mSv/dGy · cm2 for anteroposterior, inlet, outlet, Judet left, and Judet right views, respectively (all R2 ≥ 0.94). CONCLUSION. DAP/E conversion coefficients are provided for a five-view pelvic radiograph series to allow reliable estimation of E. Measurement of cumulative E may affirm protocol design changes for the management of pelvic trauma.

Three keys to the radiation of angiosperms into freezing environments.

Early flowering plants are thought to have been woody species restricted to warm habitats. This lineage has since radiated into almost every climate, with manifold growth forms. As angiosperms spread and climate changed, they evolved mechanisms to cope with episodic freezing. To explore the evolution of traits underpinning the ability to persist in freezing conditions, we assembled a large species-level database of growth habit (woody or herbaceous; 49,064 species), as well as leaf phenology (evergreen or deciduous), diameter of hydraulic conduits (that is, xylem vessels and tracheids) and climate occupancies (exposure to freezing). To model the evolution of species' traits and climate occupancies, we combined these data with an unparalleled dated molecular phylogeny (32,223 species) for land plants. Here we show that woody clades successfully moved into freezing-prone environments by either possessing transport networks of small safe conduits and/or shutting down hydraulic function by dropping leaves during freezing. Herbaceous species largely avoided freezing periods by senescing cheaply constructed aboveground tissue. Growth habit has long been considered labile, but we find that growth habit was less labile than climate occupancy. Additionally, freezing environments were largely filled by lineages that had already become herbs or, when remaining woody, already had small conduits (that is, the trait evolved before the climate occupancy). By contrast, most deciduous woody lineages had an evolutionary shift to seasonally shedding their leaves only after exposure to freezing (that is, the climate occupancy evolved before the trait). For angiosperms to inhabit novel cold environments they had to gain new structural and functional trait solutions; our results suggest that many of these solutions were probably acquired before their foray into the cold.

Inference of Evolutionary Jumps in Large Phylogenies using Lévy Processes.

Although it is now widely accepted that the rate of phenotypic evolution may not necessarily be constant across large phylogenies, the frequency and phylogenetic position of periods of rapid evolution remain unclear. In his highly influential view of evolution, G. G. Simpson supposed that such evolutionary jumps occur when organisms transition into so-called new adaptive zones, for instance after dispersal into a new geographic area, after rapid climatic changes, or following the appearance of an evolutionary novelty. Only recently, large, accurate and well calibrated phylogenies have become available that allow testing this hypothesis directly, yet inferring evolutionary jumps remains computationally very challenging. Here, we develop a computationally highly efficient algorithm to accurately infer the rate and strength of evolutionary jumps as well as their phylogenetic location. Following previous work we model evolutionary jumps as a compound process, but introduce a novel approach to sample jump configurations that does not require matrix inversions and thus naturally scales to large trees. We then make use of this development to infer evolutionary jumps in Anolis lizards and Loriinii parrots where we find strong signal for such jumps at the basis of clades that transitioned into new adaptive zones, just as postulated by Simpson's hypothesis. [evolutionary jump; Lévy process; phenotypic evolution; punctuated equilibrium; quantitative traits.

Femoral Neck Fractures in Young Patients.

Femoral neck fractures in patients 55 years or younger, although relatively uncommon, may cause considerable surgeon stress because they may be thought to be surgical emergencies and are difficult to manage, resulting in serious complications. Orthopaedic surgeons should understand the optimal timing for, the reduction options and techniques for, the fixation options for, and the results of surgical management of femoral neck fractures in patients 55 years or younger. The optimal timing of the surgical management of femoral neck fractures in these patients is a subject of debate. Anatomic reduction, which correlates with patient outcomes, is the goal in the management of femoral neck fractures whether it is attained via open or closed means. Multiple surgical approaches, including the Watson-Jones, Smith-Petersen, and Hueter approaches, may be used for the open reduction of femoral neck fractures. Multiple options are available for fixation, with cannulated screws and the compression hip screw most used in the literature. These implants should provide torsional stability, minimal bone loss, and a length-stable construct. Currently, no ideal implant exists. The outcomes of young patients with a femoral neck fracture who undergo surgical treatment depend more on fracture type, fracture reduction, and stable fixation than early surgical management; however, surgical management should not be excessively delayed.

Heterotopic ossification around the knee after tibial nailing and ipsilateral antegrade and retrograde femoral nailing in the treatment of floating knee injuries.

PURPOSE: Floating knee injuries are relatively uncommon injuries. We report the prevalence, location, and severity of heterotopic ossification (HO) around the knee in patients treated with antegrade tibial intramedullary nailing and ipsilateral antegrade versus retrograde femoral intramedullary nailing as well as how the severity of HO around the knee affects knee range of motion (ROM). METHODS: From 2004 to 2014, 26 floating knee injuries were included. Radiographs were reviewed to determine presence, location, and severity of HO. Post-operative knee ROM was determined. RESULTS: A significantly higher prevalence of HO around the knee was detected in the retrograde group (90%) compared to the antegrade group (43%) (p = 0.028). There was a trend for more HO into the patellar tendon occurring in 29% of patients in the antegrade group and 74% in the retrograde group (p = 0.069). The severity of HO was higher for the retrograde group 1.6 ± 1.0 compared to the antegrade group 0.4 ± 0.5 (p = 0.004). There was poor correlation between HO severity and knee ROM. CONCLUSIONS: Treatment of floating knee injuries with a retrograde femoral nail was demonstrated to result in a greater likelihood of developing HO and a greater severity of HO around the knee than if treated with an antegrade femoral nail. However, this increased severity of HO is unlikely to affect ROM. LEVEL OF EVIDENCE: III.

Complex history of the amphibian-killing chytrid fungus revealed with genome resequencing data.

Understanding the evolutionary history of microbial pathogens is critical for mitigating the impacts of emerging infectious diseases on economically and ecologically important host species. We used a genome resequencing approach to resolve the evolutionary history of an important microbial pathogen, the chytrid Batrachochytrium dendrobatidis (Bd), which has been implicated in amphibian declines worldwide. We sequenced the genomes of 29 isolates of Bd from around the world, with an emphasis on North, Central, and South America because of the devastating effect that Bd has had on amphibian populations in the New World. We found a substantial amount of evolutionary complexity in Bd with deep phylogenetic diversity that predates observed global amphibian declines. By investigating the entire genome, we found that even the most recently evolved Bd clade (termed the global panzootic lineage) contained more genetic variation than previously reported. We also found dramatic differences among isolates and among genomic regions in chromosomal copy number and patterns of heterozygosity, suggesting complex and heterogeneous genome dynamics. Finally, we report evidence for selection acting on the Bd genome, supporting the hypothesis that protease genes are important in evolutionary transitions in this group. Bd is considered an emerging pathogen because of its recent effects on amphibians, but our data indicate that it has a complex evolutionary history that predates recent disease outbreaks. Therefore, it is important to consider the contemporary effects of Bd in a broader evolutionary context and identify specific mechanisms that may have led to shifts in virulence in this system.

geiger v2.0: an expanded suite of methods for fitting macroevolutionary models to phylogenetic trees.

SUMMARY: Phylogenetic comparative methods are essential for addressing evolutionary hypotheses with interspecific data. The scale and scope of such data have increased dramatically in the past few years. Many existing approaches are either computationally infeasible or inappropriate for data of this size. To address both of these problems, we present geiger v2.0, a complete overhaul of the popular R package geiger. We have reimplemented existing methods with more efficient algorithms and have developed several new approaches for accomodating heterogeneous models and data types. AVAILABILITY AND IMPLEMENTATION: This R package is available on the CRAN repository http://cran.r-project.org/web/packages/geiger/. All source code is also available on github http://github.com/mwpennell/geiger-v2. geiger v2.0 depends on the ape package. CONTACT: mwpennell@gmail.com SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Nested radiations and the pulse of angiosperm diversification: increased diversification rates often follow whole genome duplications.

Our growing understanding of the plant tree of life provides a novel opportunity to uncover the major drivers of angiosperm diversity. Using a time-calibrated phylogeny, we characterized hot and cold spots of lineage diversification across the angiosperm tree of life by modeling evolutionary diversification using stepwise AIC (MEDUSA). We also tested the whole-genome duplication (WGD) radiation lag-time model, which postulates that increases in diversification tend to lag behind established WGD events. Diversification rates have been incredibly heterogeneous throughout the evolutionary history of angiosperms and reveal a pattern of 'nested radiations' - increases in net diversification nested within other radiations. This pattern in turn generates a negative relationship between clade age and diversity across both families and orders. We suggest that stochastically changing diversification rates across the phylogeny explain these patterns. Finally, we demonstrate significant statistical support for the WGD radiation lag-time model. Across angiosperms, nested shifts in diversification led to an overall increasing rate of net diversification and declining relative extinction rates through time. These diversification shifts are only rarely perfectly associated with WGD events, but commonly follow them after a lag period.

Correlating preoperative imaging with intraoperative fluoroscopy in iliosacral screw placement.

BACKGROUND: Percutaneous iliosacral screw placement can successfully stabilize unstable posterior pelvic ring injuries. Intraoperative fluoroscopic imaging is a vital component needed in safely placing iliosacral screws. Obtaining and appropriately interpreting fluoroscopic views can be challenging in certain clinical scenarios. We report on a series of patients to demonstrate how preoperative computed tomography (CT) imaging can be used to anticipate the appropriate intraoperative inlet and outlet fluoroscopic views. MATERIALS AND METHODS: 24 patients were retrospectively identified with unstable pelvic ring injuries requiring operative fixation using percutaneous iliosacral screws. Utilizing the sagittal reconstructions of the preoperative CT scans, anticipated inlet and outlet angle measurements were calculated. The operative reports were reviewed to determine the angles used intraoperatively. Postoperative CT scans were reviewed for repeat measurements and to determine the location and safety of each screw. RESULTS: Preoperative CT scans showed an average inlet of 20.5° (7°-37°) and an average outlet of 42.8° (30°-59°). Intraoperative views showed an average inlet of 24.9° (12°-38°) and an average outlet of 42.4° (29°-52°). Postoperative CT scans showed an average inlet of 19.4° (8°-31°) and an average outlet of 43.2° (31°-56°). The average difference from preoperative to intraoperative was 4.4° (-21° to 5°) for the inlet and 0.45° (-9° to 7°) for the outlet. The average difference between the preoperative and postoperative CT was 2.04° (0°-6°) for the inlet and 2.54° (0°-7°) for the outlet. CONCLUSION: There is significant anatomic variation of the posterior pelvic ring. The preoperative CT sagittal reconstruction images allow for appropriate preoperative planning for anticipated intraoperative fluoroscopic inlet and outlet views within 5°. Having knowledge of the desired intraoperative views preoperatively prepares the surgeon, aids in efficiently obtaining correct intraoperative views, and ultimately assists in safe iliosacral screw placement.

A stable niche assumption-free test of ecological divergence.

Understanding the impact of geological events on diversification processes is central to evolutionary ecology. The recent amalgamation between ecological niche models (ENMs) and phylogenetic analyses has been used to estimate historical ranges of modern lineages by projecting current ecological niches of organisms onto paleoclimatic reconstructions. A critical assumption underlying this approach is that niches are stable over time. Using Notophthalmus viridescens (eastern newt), in which four ecologically diverged subspecies are recognized, we introduce an analytical framework free from the niche stability assumption to examine how refugial retreat and subsequent postglacial expansion have affected intraspecific ecological divergence. We found that the current subspecies designation was not congruent with the phylogenetic lineages. Thus, we examined ecological niche overlap between the refugial and modern populations, in both subspecies and lineage, by creating ENMs independently for modern and estimated last glacial maximum (LGM) newt populations, extracting bioclimate variables by randomly generated points, and conducting principal component analyses. Our analyses consistently showed that when tested as a hypothesis, rather than used as an assumption, the niches of N. viridescens lineages have been unstable since the LGM (both subspecies and lineages). There was greater ecological niche differentiation among the subspecies than the modern phylogenetic lineages, suggesting that the subspecies, rather than the phylogenetic lineages, is the unit of the current ecological divergence. The present study found little evidence that the LGM refugial retreat caused the currently observed ecological divergence and suggests that ecological divergence has occurred during postglacial expansion to the current distribution ranges.

Insertion sites of iliosacral screws on the posterior ilium: Implications for posterior pelvic fixation.

OBJECTIVES: Lateral compression type II pelvic ring injuries can be treated with fixation through open or percutaneous approaches depending on the injury pattern and available osseous fixation pathways. The start site of iliosacral screws to stabilize these injuries should be on the unstable posterior iliac fragment; however, our understanding of start sites for iliosacral screws has not been developed. The purpose of this study is to provide an analysis of iliosacral screw start sites on the posterior ilium to help guide treatment of pelvic ring injuries. METHODS: One-hundred and seventeen consecutive patients at an academic level I trauma center with pelvic ring injuries who underwent surgical treatment with iliosacral screws were included in the final analysis. The start sites of iliosacral screws with confirmed intraosseous placement on a postoperative computed tomography were mapped on the posterior ilium and analyzed according to the sacral segment and type of iliosacral screw. RESULTS: One-hundred and seventeen patients were included in the final analysis. Of the total of 272 iliosacral screw insertion sites analyzed, 145 (53%) were sacroiliac-style screws and 127 (47%) were transsacral screws. The insertion sites for sacroiliac-style screws and transsacral screws at different sacral segment levels can vary but have predictable regions on the posterior ilium relative to reliable osseous landmarks. CONCLUSIONS: Iliosacral screws start sites on the posterior ilium have reliable regions that can be used to plan posterior fixation of pelvic ring injuries.