Analysis of acute extremity compartment syndrome using a genealogic population database.

INTRODUCTION: Acute extremity compartment syndrome ("CS") is an under-researched, highly morbid condition affecting trauma populations. The purpose of this study was to analyze incidence rates and risk factors for extremity compartment syndrome using a high-quality population database. Additionally, we evaluated heritable risk for CS using available genealogic data. We hypothesized that diagnosis of extremity compartment syndrome would demonstrate heritability. MATERIALS AND METHODS: Adult patients with fractures of the tibia, femur, and upper extremity were retrospectively identified by ICD-9, ICD-10, and CPT codes from 1996 to 2020 in a statewide hospital database. Exposed and unexposed cohorts were created based on a diagnosis of CS. Available demographic data were analyzed to determine risk factors for compartment syndrome using logistic regression. Mortality risk at the final follow-up was evaluated using Cox proportional hazard modeling. Patients with a diagnosis of CS were matched with those without a diagnosis for heritability analysis. RESULTS: Of 158,624 fractures, 931 patients were diagnosed with CS. Incidence of CS was 0.59% (tibia 0.83%, femur 0.31%, upper extremity 0.27%). Male sex (78.1% vs. 46.4%; p < 0.001; RR = 3.24), younger age at fracture (38.8 vs. 48.0 years; p < 0.001; RR = 0.74), Medicaid enrollment (13.2% vs. 9.3%; p < 0.001; RR = 1.58), and smoking (41.1% vs. 31.1%; p < 0.001; RR 1.67) were significant risk factors for CS. CS was associated with mortality (RR 1.61, p < 0.001) at mean follow-up 8.9 years in the CS cohort. No significant heritable risk was found for diagnosis of CS. CONCLUSIONS: Without isolating high-risk fractures, rates of CS are lower than previously reported in the literature. Male sex, younger age, smoking, and Medicaid enrollment were independent risk factors for CS. CS increased mortality risk at long-term follow-up. No heritable risk was found for CS. LEVEL OF EVIDENCE: III.

Evolution of hygrophytic plant species in the Anatolia-Caucasus region: insights from phylogenomic analyses of Cardamine perennials.

BACKGROUND AND AIMS: Southwestern Asia is a significant centre of biodiversity and a cradle of diversification for many plant groups, especially xerophytic elements. In contrast, little is known about the evolution and diversification of its hygrophytic flora. To fill this gap, we focus on Cardamine (Brassicaceae) species that grow in wetlands over a wide altitudinal range. We aimed to elucidate their evolution, assess the extent of presumed historical gene flow between species, and draw inferences about intraspecific structure. METHODS: We applied the phylogenomic Hyb-Seq approach, ecological niche analyses and multivariate morphometrics to a total of 85 Cardamine populations from the target region of Anatolia-Caucasus, usually treated as four to six species, and supplemented them with close relatives from Europe. KEY RESULTS: Five diploids are recognized in the focus area, three of which occur in regions adjacent to the Black and/or Caspian Sea (C. penzesii, C. tenera, C. lazica), one species widely distributed from the Caucasus to Lebanon and Iran (C. uliginosa), and one western Anatolian entity (provisionally C. cf. uliginosa). Phylogenomic data suggest recent speciation during the Pleistocene, likely driven by both geographic separation (allopatry) and ecological divergence. With the exception of a single hybrid (allotetraploid) speciation event proven for C. wiedemanniana, an endemic of southern Turkey, no significant traces of past or present interspecific gene flow were observed. Genetic variation within the studied species is spatially structured, suggesting reduced gene flow due to geographic and ecological barriers, but also glacial survival in different refugia. CONCLUSIONS: This study highlights the importance of the refugial regions of the Black and Caspian Seas for both harbouring and generating hygrophytic species diversity in Southwestern Asia. It also supports the significance of evolutionary links between Anatolia and the Balkan Peninsula. Reticulation and polyploidization played a minor evolutionary role here in contrast to the European relatives.

Human Dermal Allograft Superior Capsule Reconstruction With Graft Length Determined at Glenohumeral Abduction Angles of 20° and 40° Decreases Joint Translation and Subacromial Pressure Without Compromising Range of Motion: A Cadaveric Biomechanical Study.

PURPOSE: To compare the biomechanical effects of superior capsule reconstruction (SCR) graft fixation length determined at 20° and 40° of glenohumeral (GH) abduction. METHODS: Humeral translation, rotational range of motion (ROM), and subacromial contact pressure were quantified at 0°, 30°, and 60° of GH abduction in the scapular plane in 6 cadaveric shoulders for the following states: intact, massive rotator cuff tear, SCR with dermal allograft fixed at 20° of GH abduction (SCR 20), and SCR with dermal allograft fixed at 40° of GH abduction (SCR 40). Statistical analysis was conducted using a repeated-measures analysis of variance and a paired t test (P < .05). RESULTS: A massive cuff tear significantly increased total ROM compared with the intact state at 0° and 60° of abduction. SCR 20 or SCR 40 did not affect ROM. Compared with the intact state, the massive cuff tear model significantly increased superior translation by an average of 4.6 ± 0.5 mm in 9 of 12 positions (P ≤ .002). Both SCR 20 and SCR 40 reduced superior translation compared with the massive cuff tear model (P < .05); however, SCR 40 significantly decreased superior translation compared with SCR 20 at 0° of abduction (P ≤ .046). Peak subacromial pressure for the massive cuff tear model increased by an average of 486.8 ± 233.9 kPa relative to the intact state in 5 of 12 positions (P ≤ .037). SCR 20 reduced peak subacromial pressure in 2 of 12 positions (P ≤ .012), whereas SCR 40 achieved this in 6 of 12 positions (P ≤ .024). CONCLUSIONS: SCR with dermal allograft fixed at 20° or 40° of GH abduction decreases GH translation and subacromial pressure without decreasing ROM. CLINICAL RELEVANCE: With an increasing abduction angle for graft fixation, the medial-to-lateral graft length is decreased and the graft tension is effectively increased. Surgeons may increase shoulder stability without restricting ROM by fixing the graft at higher abduction angles. However, surgeons should remain cognizant of potential graft failure due to increased tension.

Biomechanical assessment of docking ulnar collateral ligament reconstruction after failed ulnar collateral ligament repair with suture augmentation.

BACKGROUND: Ulnar collateral ligament (UCL) repair with single-strand suture augmentation has been introduced as a viable surgical option for throwers with acute UCL tears. For the original single-strand suture augmentation construct, revision UCL reconstructions can be challenging owing to the bone loss at the site of anchor insertion in the center of the sublime tubercle. This biomechanical study assessed a small-diameter (1.5-mm) ulnar bone tunnel technique for double-strand suture-augmented UCL repair that may be more easily converted to salvage UCL reconstruction if necessary, as well as a salvage UCL reconstruction with a docking technique after a failed primary suture-augmented UCL repair. METHODS: In 7 fresh-frozen cadaveric upper extremities (mean age, 66.3 years), a custom shoulder testing system was used to simulate the late cocking phase of throwing. The elbow valgus opening angle was evaluated using a MicroScribe 3DLX device for sequentially increasing valgus torque (from 0.75 to 7.5 Nm in 0.75-Nm increments) at 90° of flexion. Valgus angular stiffness (in newton-meters per degree) was defined as the correlation of sequentially increasing valgus torque with the valgus opening angle through simple linear regression (slope of valgus torque - valgus opening angle curve). Four conditions were tested: intact elbow, distal UCL avulsion, primary UCL repair with double-strand suture augmentation using small-diameter bone tunnels, and subsequent docking UCL reconstruction in the same specimen. Load-to-failure tests were performed for primary UCL repair with double-strand suture augmentation and subsequent docking UCL reconstruction. RESULTS: With increasing elbow valgus torque, the valgus opening angle increased linearly in each condition (R2 ≥ 0.98, P < .001). Distal UCL avulsion resulted in significantly decreased angular stiffness compared with the intact UCL (P < .001). Both UCL repair with double-strand suture augmentation and subsequent UCL reconstruction showed significantly increased angular stiffness values compared with distal UCL avulsion (P < .001 and P < .001, respectively). On load-to-failure testing, there was no significant difference in stiffness, yield torque, and ultimate torque between the primary suture-augmented UCL repair and the subsequent UCL reconstruction (P = .11, P = .77, and P = .38, respectively). In all specimens undergoing the small-diameter ulnar bone tunnel technique for double-strand suture-augmented UCL repair, failure occurred by retear of the repaired ligament without causing an ulnar bone bridge fracture. CONCLUSION: Primary UCL repair with double-strand suture augmentation using small-diameter bone tunnels was able to restore valgus stability. When failure occurs, this technique retains enough cortical bone to permit subsequent docking UCL reconstruction.

Anterior Capsule Reconstruction Versus Pectoralis Major Transfer for Irreparable Subscapularis Tears Involving the Anterior Capsule: A Comparative Biomechanical Cadaveric Study.

PURPOSE: To compare the biomechanical effectiveness of human dermal allograft (HDA) anterior capsular reconstruction (ACR) and pectoralis major tendon transfer (PMTT) for treating irreparable subscapularis tears with capsular insufficiency in human cadaver shoulders. METHODS: Glenohumeral rotational range of motion and translation were measured in 6 cadaveric shoulders under the following 5 conditions: intact, deficient subscapularis/anterior capsule, ACR using HDA, HDA ACR with concomitant PMTT, and PMTT alone. RESULTS: The deficient subscapularis/anterior capsule condition significantly increased external and total rotational range of motion at 0° (P < .001, P < .001) and 30° (P = .005, P = .002) abduction as well as anterior-inferior translation (P ≤ .001 to .03). HDA ACR, both with and without PMTT, restored anterior-inferior stability to that of the intact condition; however, PMTT alone did not restore anterior-inferior translation or rotational range of motion. CONCLUSIONS: HDA ACR for treating irreparable subscapularis tears with capsular insufficiency restored anterior-inferior glenohumeral translation and rotational range of motion at time 0 in human cadaver shoulders. CLINICAL RELEVANCE: Anterior capsule reconstruction may be a viable option for treating massive irreparable subscapularis tears with capsular insufficiency.

A biomechanical cadaveric study of patellar tendon allograft as an alternative graft material for superior capsule reconstruction.

HYPOTHESIS: In a cadaveric irreparable rotator cuff tear model, patellar tendon allograft-superior capsule reconstruction (PT-SCR) will restore glenohumeral stability and reduce subacromial contact pressures without significant graft deformation during testing. METHODS: Eight cadaveric shoulders were tested in a custom shoulder testing system. Rotational range of motion (ROM), superior translation, and subacromial contact pressure were measured in the following experimental conditions: intact rotator cuff, irreparable supraspinatus tear (massive cuff tear [MCT]), and PT-SCR. RESULTS: MCT and PT-SCR resulted in significantly increased total ROM at all degrees of abduction compared with the intact state (P < .001). In both 0° and 30° of glenohumeral abduction, MCT showed a significant increase in superior translation compared with the intact state (P < .001). Application of the PT-SCR resulted in a decrease of superior translation compared with MCT (P < .001). At 0° abduction/60° external rotation and 0° abduction/90° external rotation, MCT showed significantly greater peak subacromial contact pressure compared with the intact state (P < .006). At both of these positions, PT-SCR was able to reduce peak pressure to lower than or no significant difference from the intact state. There was no statistically significant change in graft thickness, length, or width after testing. CONCLUSION: PT-SCR was able to reduce superior translation of the humeral head and peak subacromial contact pressure without restricting ROM. Furthermore, there was no significant graft deformation during testing. PT-SCR in this validated cadaveric model demonstrates favorable biomechanical properties and is a viable source of graft material for SCR.

Anterior Cable Reconstruction Using the Proximal Biceps Tendon for Large Rotator Cuff Defects Limits Superior Migration and Subacromial Contact Without Inhibiting Range of Motion: A Biomechanical Analysis.

PURPOSE: To assess an anterior cable reconstruction (ACR) using autologous proximal biceps tendon for large to massive rotator cuff tears. METHODS: Nine cadaveric shoulders (mean age, 58 years) were tested with a custom testing system. Range of motion, superior translation of the humeral head, and subacromial contact pressure were measured at 0°, 30°, 60°, and 90° of external rotation (ER) with 0°, 20°, and 40° of glenohumeral abduction. Five conditions were tested: intact, stage II tear (supraspinatus), stage II tear + ACR, stage III tear (supraspinatus + anterior half of infraspinatus), and stage III tear + ACR. ACR involved a biceps tendon tenotomy at the transverse humeral ligament, preserving its labral attachment. ACR included nonpenetrating suture-loop fixation using 2 side-to-side sutures and an anchor at the articular margin to restore anatomy and secure the tendon along the anterior edge of the cuff defect. ACR was performed in 20° glenohumeral abduction and 60° ER. RESULTS: ACR for both stage II and stage III showed significantly higher total range of motion compared with intact at all angles (P ≤ .001). ACR significantly decreased superior translation for stage II tears at 0°, 30°, and 60° ER for both 0° and 20° abduction (P ≤ .01) and for stage III tears at 0° and 30° ER for both 0° and 20° abduction (P ≤ .004). ACR for stage III tear significantly reduced peak subacromial contact pressure at 30° and 60° ER with 0° and 40° abduction and at 30° ER with 20° abduction (P ≤ .041). CONCLUSIONS: ACR using autologous biceps tendon biomechanically normalized superior migration and subacromial contact pressure, without limiting range of motion. CLINICAL RELEVANCE: ACR may improve rotator cuff tendon repair longevity by providing basic static ligamentous support to the dynamic tendon while helping to limit superior migration without restricting glenohumeral kinematics.

Mid-term outcomes of temporary medial distal femoral hemiepiphysiodesis with and without medial patellofemoral ligament repair for recurrent patellar instability in skeletally immature patients with genu valgum.

Genu valgum contributes to patellar instability, though outcomes following temporary hemiepiphysiodesis via eight plating are less understood. The purpose of this study was to evaluate the outcomes and need for additional procedures following temporary hemiepiphysiodesis for the treatment of pediatric genu valgum and patellar instability, as well as evaluating the utility of a concurrent medial patellofemoral ligament (MPFL) repair. Patients who underwent medial distal femoral epiphysiodesis for the treatment of genu valgum and recurrent patellar instability were identified. Inclusion criteria were minimum 1-year follow-up and lack of concurrent ligamentous reconstruction. Patients were contacted to complete a questionnaire which included the International Knee Documentation Committee (IKDC) form and questions pertaining to knee function and patient satisfaction. Thirty-one patients aged 12.0 ± 1.9 years underwent 47 guided growth procedures and were included in final analysis. Seventeen knees (36%) required subsequent surgery for patellar instability. All patients requiring subsequent surgery were female, compared with 70% of patients not requiring subsequent surgery ( P  = 0.017). The MPFL repair group underwent fewer subsequent procedures to address instability, though this difference was NS (17 vs. 46%, P  = 0.318). Mean IKDC score at 5.3 years follow-up among 18 survey respondents was 78.6. Medial distal femoral hemiepiphysiodesis may partially address recurrent patellar instability in skeletally immature patients with genu valgum. Concurrent MPFL repair may minimize the need for subsequent procedures to address recurrent instability. While correcting alignment may be helpful, patients should be aware of the potential need for further patellar instability surgery. Level of evidence: IV, case series.

Familial Analysis of Nonunion in a Genealogic Population Database Demonstrates No Evidence of Heritable Risk.

OBJECTIVE: To determine whether there is evidence of heritable risk for nonunion using a large, state-wide population database. DESIGN: Database. SETTING: Level 1 Trauma Center. POPULATION: All Utah residents from 1996 to 2021 who sustained a long bone fracture and their family members were included. OUTCOMES: The primary outcome was nonunion and the prevalence of nonunion among the patients' first-, second-, and third-degree relatives. The secondary objective was to identify demographic, injury, and socioeconomic risk factors associated with nonunion. RESULTS: In total, 150,263 fractures and 6577 nonunions (4.4%) were identified. This was highly refined to a 1:3 matched cohort of 4667 nonunions of 13,981 fractures for familial clustering analysis. Cox proportional hazards did not demonstrate excessive risk of nonunion among first- ( P = 0.863), second- ( P = 0.509), and third-degree relatives ( P = 0.252). Further analysis of the entire cohort demonstrated that male sex (relative risk [RR] = 1.15; P < 0.001), Medicaid enrollment (RR = 2.64; P < 0.001), open fracture (RR = 2.53; P < 0.001), age group 41-60 years (RR = 1.43; P < 0.001), and a history of obesity (RR = 1.20; P < 0.001) were independent risk factors for nonunion. CONCLUSIONS: Our results demonstrate no evidence of heritable risk for nonunion. Independent risk factors for nonunion were male sex, Medicaid enrollment, open fracture, middle age, and a history of obesity. Although it is important to identify modifiable and nonmodifiable risk factors, these results continue to support that the risk of nonunion is multifactorial, relating to injury characteristics, operative techniques, and patient-specific risk factors. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Tibial Plateau Fractures Complicated by Compartment Syndrome Are Associated With a 3 Times Higher Cost of Care.

OBJECTIVES: To determine the impact of acute compartment syndrome (ACS) and identify cost drivers of 1-year total treatment costs for operative tibial plateau fractures. DESIGN: Retrospective review. SETTING: Level 1 trauma center. PATIENTS: 337 patients with tibial plateau fractures, 24 of which were complicated by ACS. OUTCOMES: The primary outcome was total treatment cost over the first year for operatively treated tibial plateau fractures. The secondary objective was to use regression analysis to identify significant cost drivers. RESULTS: The diagnosis of ACS was associated with 2.85 times higher total treatment cost ( P < 0.001). ACS demonstrated increased total treatment cost when controlling for polytrauma ( P < 0.001) and postoperative infection ( P < 0.001). Regression analysis identified 5 variables significantly associated with total cost of care: body mass index, injury severity score, ACS, staged external fixation, and locking fixation ( P < 0.001; R 2 = 0.57). The diagnosis of ACS had the largest impact on total cost with a 3.5× greater impact on cost compared with the next highest variable, staged external fixation. CONCLUSIONS: Tibial plateau fractures complicated by ACS are associated with 2.85 times higher treatment costs over a 1-year period. There were 5 significant variables identified by regression analysis with ACS having the highest impact on total treatment. Together, these 5 factors account for 57% of treatment cost variability. LEVEL OF EVIDENCE: Economic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Return to Skiing After Tibial Plateau Fracture.

Background: Tibial plateau fractures in skiers are devastating injuries with increasing incidence. Few studies have evaluated patient-reported outcomes and return to skiing after operative fixation of a tibial plateau fracture. Purpose: To (1) identify demographic factors, fracture characteristics, and patient-reported outcome measures that are associated with return to skiing and (2) characterize changes in skiing performance after operative fixation of a tibial plateau fracture. Study Design: Case series; Level of evidence, 4. Methods: We reviewed all operative tibial plateau fractures performed between 2016 and 2021 at a single level-1 trauma center. Patients with a minimum of 10-month follow-up data were included. Patients who self-identified as skiers or were injured skiing were divided into those who returned to skiing and those who did not postoperatively. Patients were contacted to complete the Patient-Reported Outcomes Measurement Information System-Physical Function domain (PROMIS-PF), the Knee injury and Osteoarthritis Outcome Score-Activities of Living (KOOS-ADL), and a custom return-to-skiing questionnaire. Multivariate logistic regression was performed with sex, injury while skiing, PROMIS-PF, and KOOS-ADL as covariates to evaluate factors predictive of return to skiing. Results: A total of 90 skiers with a mean follow-up of 3.4 ± 1.5 years were included in the analysis. The rate of return to skiing was 45.6% (n = 41). The return cohort was significantly more likely to be men (66% vs 41%; P = .018) and injured while skiing (63% vs 39%; P = .020). In the return cohort, 51.2% returned to skiing 12 months postoperatively. The percentage of patients who self-reported skiing on expert terrain dropped by half from pre- to postinjury (61% vs 29.3%, respectively). Only 78% of return skiers had regained comfort with skiing at the final follow-up. Most patients (65%) felt the hardest aspect of returning to skiing was psychological. In the multivariate regression, the male sex and KOOS-ADL independently predicted return to skiing (P = .006 and P = .028, respectively). Conclusion: Fewer than half of skiers who underwent operative fixation of a tibial plateau fracture could return to skiing at a mean 3-year follow-up. The knee-specific KOOS-ADL outperformed the global PROMIS-PF in predicting a return to skiing.

What Happens on the Back Table? Viability and Osteogenic Potential of Reamed Autogenous Bone Graft as a Function of Time and Temperature-A Pilot Study.

OBJECTIVES: To provide guidelines for reamed autogenous bone graft (R-ABG) in nonunion surgery to best manage modifiable intraoperative factors, like storage temperature and time, for optimal graft viability. Our hypothesis was that R-ABG graft will show decreased cell viability as a function of increased time and storage temperature. METHODS: R-ABG samples were obtained using an RIA system from 10 patients undergoing harvest for the treatment of a nonunion. A 10 cm3 sample of cancellous bone graft was divided into 10 samples. A control sample was processed immediately and analyzed using fluorescence activated cell sorting to determine its cell viability. The remaining samples were stored at 0, 15, and 37°C and processed similarly after 60 and 120 minutes. A paired t test was used to compare the mean change in percent viability. RESULTS: The mean percent cell viability for the experimental conditions was not significantly different from the initial percent cell viability (P ≥ 0.08). There were no significant differences in the change in mean percentage of viable cells (P ≥ 0.07). After 60 and 120 minutes of storage, there were no significant differences in mean cell viability based on storage temperature (P ≥ 0.53 and P ≥ 0.68, respectively). A power analysis estimated that a sample size of 52 patients would be needed to detect a difference. CONCLUSIONS: The results of our pilot study indicate that storage conditions may have less effect on cell viability than previously hypothesized. Further research with more patients is needed to confirm these preliminary results. LEVEL OF EVIDENCE: Level II.

Aquatic microbial habitats within a neotropical rainforest: bromeliads and pH-associated trends in bacterial diversity and composition.

Tank-forming bromeliads, suspended in the rainforest canopy, possess foliage arranged in compact rosettes capable of long-term retention of rainwater. This large and unique aquatic habitat is inhabited by microorganisms involved in the important decomposition of impounded material. Moreover, these communities are likely influenced by environmental factors such as pH, oxygen, and light. Bacterial community composition and diversity was determined for the tanks of several bromeliad species (Aechmea and Werauhia) from northern Costa Rica, which span a range of parameters, including tank morphology and pH. These were compared with a nearby forest soil sample, an artificial tank (amber bottle), and a commercially available species (Aechmea). Bacterial community diversity, as measured by 16S rRNA analysis and tRFLP, showed a significant positive correlation with tank pH. A majority of 16S rRNA bacterial phylotypes found in association with acidic bromeliad tanks of pH < 5.1 were affiliated with the Alphaproteobacteria, Acidobacteria, Planctomycetes, and Bacteroidetes, and were similar to those found in acidic peat bogs, yet distinct from the underlying soil community. In contrast, bromeliads with tank pH > 5.3, including the commercial bromeliad with the highest pH (6.7), were dominated by Betaproteobacteria, Firmicutes, and Bacteroidetes. To empirically determine the effect of pH on bacterial community, the tank pH of a specimen of Aechmea was depressed, in the field, from 6.5 to 4.5, for 62 days. The resulting community changed predictably with decreased abundance of Betaproteobacteria and Firmicutes and a concomitant increase in Alphaproteobacteria and Acidobacteria. Collectively, these results suggest that bromeliad tanks provide important habitats for a diverse microbial community, distinct from the surrounding environment, which are influenced greatly by acid-base conditions. Additionally, total organic carbon (∼46%) and nitrogen (∼2%) of bromeliad-impounded sediment was elevated relative to soil and gene surveys confirmed the presence of both chitinases and nitrogenases, suggesting that bromeliad tanks may provide important habitats for microbes involved in the biological cycling of carbon and nitrogen in tropical forests.

Allele Sorting as a Novel Approach to Resolving the Origin of Allotetraploids Using Hyb-Seq Data: A Case Study of the Balkan Mountain Endemic Cardamine barbaraeoides.

Mountains of the Balkan Peninsula are significant biodiversity hotspots with great species richness and a large proportion of narrow endemics. Processes that have driven the evolution of the rich Balkan mountain flora, however, are still insufficiently explored and understood. Here we focus on a group of Cardamine (Brassicaceae) perennials growing in wet, mainly mountainous habitats. It comprises several Mediterranean endemics, including those restricted to the Balkan Peninsula. We used target enrichment with genome skimming (Hyb-Seq) to infer their phylogenetic relationships, and, along with genomic in situ hybridization (GISH), to resolve the origin of tetraploid Cardamine barbaraeoides endemic to the Southern Pindos Mts. (Greece). We also explored the challenges of phylogenomic analyses of polyploid species and developed a new approach of allele sorting into homeologs that allows identifying subgenomes inherited from different progenitors. We obtained a robust phylogenetic reconstruction for diploids based on 1,168 low-copy nuclear genes, which suggested both allopatric and ecological speciation events. In addition, cases of plastid-nuclear discordance, in agreement with divergent nuclear ribosomal DNA (nrDNA) copy variants in some species, indicated traces of interspecific gene flow. Our results also support biogeographic links between the Balkan and Anatolian-Caucasus regions and illustrate the contribution of the latter region to high Balkan biodiversity. An allopolyploid origin was inferred for C. barbaraeoides, which highlights the role of mountains in the Balkan Peninsula both as refugia and melting pots favoring species contacts and polyploid evolution in response to Pleistocene climate-induced range dynamics. Overall, our study demonstrates the importance of a thorough phylogenomic approach when studying the evolution of recently diverged species complexes affected by reticulation events at both diploid and polyploid levels. We emphasize the significance of retrieving allelic and homeologous variation from nuclear genes, as well as multiple nrDNA copy variants from genome skim data.

Hangman's Fracture.

STUDY DESIGN: Review article. OBJECTIVE: A review and update of the treatment of Hangman's fractures including the indications for both nonoperative and operative treatment of typical and atypical fractures. SUMMARY OF BACKGROUND DATA: Hangman's fractures are the second most common fracture pattern of the C2 vertebrae following odontoid fractures. Many of the stable extension type I and II fractures can be treated with external immobilization, whereas the predominant flexion type IIa and III fractures require surgical stabilization. METHODS: A review of the literature. RESULTS: The clinical and radiographic outcomes of the treatment of Hangman's fractures lend a good overall prognosis when the correct diagnosis is made. The nonoperative treatment of stable type I and II fractures with external immobilization leads to excellent long-term outcomes as does the operative treatment of the unstable type IIa and III fractures. CONCLUSIONS: Hangman's fractures can be classified as stable (type I and most II) or unstable (type IIa and III) and the optimal treatment depends upon this distinction. Stable injuries do well with rigid immobilization and rarely require operative intervention. In contrast, unstable injuries do poorly if treated nonoperatively but do well with surgical intervention. When treating atypical Hangman's variants, great vigilance and close clinical observation is paramount if nonoperative treatment is indicated given the potential for neurological compression in this fracture pattern. Properly identifying and treating these injuries represents an opportunity for the spine surgeon to optimize patient outcomes.

Complication Rates after Lateral Plate Fixation of Periprosthetic Distal Femur Fractures: A Multicenter Study.

OBJECTIVE: Periprosthetic fractures of the distal femur can be challenging injuries to treat; nonunion rates of up to 22% have been reported. The purpose of this study was to determine the rate of complications and nonunion in a multicenter series, and to identify patient or surgical factors that were associated with nonunion. DESIGN: Retrospective comparative study SETTING: Three Level 1 trauma centers PATIENTS: Fifty-five patients with a periprosthetic distal femur fracture proximal to a total knee arthroplasty. Minimum follow up for inclusion was six months or until union or failure. INTERVENTION: Surgical fixation using a precontoured lateral locking plate MAIN OUTCOME MEASUREMENT: Fracture union was the primary outcome. Patient demographic and injury variables (age, comorbidities, fracture classification and characteristics) and surgical technique factors (mode of plate fixation, plate material, working length, screw density, and proximal screw type) were identified and compared between patients who developed a nonunion and those who did not. Regression analysis was performed to identify independent risk factors for nonunion. RESULTS: The overall rate of nonunion was 18% and the total complication rate was 24%. After additional surgery, 49 of 55 patients went on to heal (89%). There were no statistical differences in patient demographic or injury variables between the union and nonunion groups, and none of the variables studied were independent risk factors for nonunion in the regression analysis. CONCLUSIONS: In this series of 55 patients with periprosthetic distal femur fractures treated with precontoured lateral locking plates, 18% developed nonunion and the overall complication rate was 24%. No patient or surgical variables were identified as risk factors. Future research should seek to identify patients at high risk for complication and nonunion who could benefit from alternative fixation strategies or distal femoral replacement.

Effect of Increased Scapular Internal Rotation on Glenohumeral External Rotation and Elbow Valgus Load in the Late Cocking Phase of Throwing Motion.

BACKGROUND: Scapular dyskinesis among throwers is thought to affect kinetic chain function and increase the load demands on the shoulder and/or elbow. However, the biomechanical relationship between scapular orientation and elbow valgus load, which is associated with ulnar collateral ligament (UCL) injury, has not been determined. PURPOSE: To evaluate the effect of increased scapular internal rotation (IR) and glenohumeral external rotation (GHER) on elbow valgus load in a static simulation of the late cocking phase of throwing. STUDY DESIGN: Controlled laboratory study. METHODS: Seven fresh-frozen male cadaveric upper extremities were used with a custom testing system to simulate the late cocking phase. First, the authors evaluated the effect of increasing scapular IR on maximum GHER and forearm angle (forearm axis relative to the ground). Each parameter was evaluated at 20° to 40° (5° increments) of scapular IR by applying 2.2-N·m external rotation torque to the humerus and 0.75-N·m valgus torque to the forearm. Next, to evaluate elbow valgus stability, the humerus was locked in maximal GHER at 40° of scapular IR, and sequentially increasing torque (0.75-7.5 N·m by 0.75-N·m increments) was applied to the forearm. Valgus angle and joint gap were evaluated at each torque. RESULTS: Increases in scapular IR ≥5° significantly decreased GHER ( P < .01). With increasing valgus torque, forearm angle also increased linearly ( R2 = 0.85, P < .001). To compensate for the GHER deficit at 40° of scapular IR, a linear regression model showed that 25.3 N·m of valgus torque would be necessary to reach the original forearm position. In the intact condition, applying elbow valgus torque ≥5.25 N·m significantly increased valgus angle and the joint gap ( P < .01). CONCLUSION: Increased scapular IR significantly decreased GHER. Compensation for the GHER deficit significantly increased the elbow valgus load required to reach the same forearm position. CLINICAL RELEVANCE: Increased scapular IR may increase the risk of elbow UCL injury among throwing athletes.