Axial Fracture Research Articles

Epidemiology of ballistic fractures in the United States: A 20-year analysis of the Firearm Injury Surveillance Study

IntroductionBallistic (i.e., gunshot-induced) fractures present unique treatment challenges and can be associated with high rates of complications and considerable morbidity. Large-scale epidemiologic data on these types of fractures are scarce. There is concern that gun-related violence may be on the rise, potentially increasing the burden of ballistic orthopaedic trauma, but there are few contemporary studies on the topic. The aim of this study, therefore, was to investigate the incidence and demographics of patients with ballistic fractures in the United States (US) over the last 20 years. Materials and MethodsThis descriptive epidemiology study retrospectively analyzed the Firearm Injury Surveillance Study to identify cases of ballistic fractures in the US from 2000 to 2019. Overall and annual numbers of fractures and fracture incidence rates (IRs), patient demographics, incident characteristics, and temporal trends were analyzed. Patients of all ages were included. Ballistic fractures were grouped by anatomic location for comparisons (non-spine axial, spine, upper extremity, lower extremity). ResultsAn estimated N = 240,555 patients (n = 8,322 unweighted cases) sustained ballistic fractures over the 20-year study period for an overall IR of 39.2 per 1,000,000 person-years at-risk (PYR). Overall, lower extremity fractures accounted for the largest percentage of cases (45.9%; IR=18.8 PYR), followed by upper extremity fractures (32.8%; IR=13.4 PYR), non-spine axial fractures (16.1%; IR=6.6 PYR), and spine fractures (5.2%; IR=2.1 PYR). Diaphyseal femur fractures were the most common ballistic fractures overall. Nearly three-fourths (71.2%) of all cases occurred in males in the second through fourth decades. The most common injury intent was assault (71.8%) and a majority of patients (71.2%) required hospital admission. Accounting for population growth yielded a significantly increasing incidence of all ballistic fractures over the study period from 15.7 PYR in 2000 to 96.8 PYR in 2019 (average annual percent change=10.3, p < 0.00001). ConclusionThese data suggest that the nationwide burden of ballistic fractures in the US has increased significantly in the last two decades. Ballistic fractures are associated with significant morbidity and societal cost, and increasing injury rates highlight the need for future research aimed at better understanding the ideal treatment of these types of fractures and their outcomes.

Mortality From Combined Fractures of the Atlas (C1) and Axis (C2) in Adults.

Study designA retrospective case report of all upper cervical spine fractures diagnosed by CT imaging between 01/01/2013 and 31/12/2015 in NHS Greater Glasgow and Clyde, Scotland.ObjectiveTo compare the mortality following combined fractures of the atlas and axis to that of isolated fractures of either vertebra.BackgroundThe mortality from axis fractures is well documented in the literature. However, a combined fracture of the atlas and axis is seldom reported, leading to relatively unknown outcomes and mortality.MethodsA total of 171 patients with atlas and/or axis fractures. Thirty-three presented with concurrent lower cervical spine fractures and were excluded from further analysis. Kaplan-Meier curves were used to compare survivorship between 108 patients with isolated and 30 with combined fractures. Similar analysis adjusted for comorbidities, including dementia and previous fragility fractures.ResultsPatients were followed up for 47.3±10.3 months (SD). Patients with isolated atlas fractures were significantly younger than those with an axis or combined fracture. Nearly half (8/17) of combined fracture mortalities occurred within the first 120 days. The mortality at 120 days was 26.7% in the combined fractures group and 18.5% in the isolated fracture group. There was no significant difference in the 120-day and overall mortality between these injury patterns. Furthermore, cognitive impairment and previous fragility fractures bore no significant impact on mortality. Nevertheless, mortality in the combined fracture group with previous fragility fractures did trend to shorter survivorship.ConclusionsPatients with combined fractures are older and with the ever-increasing elderly population, the incidence of these injuries is expected to rise. While our data show that the 120-day mortality is proportionally higher in the combined fractures group, no long-term statistically significant difference is demonstrated. This evidence contests the notion that combined fractures of the atlas and axis have higher mortality than isolated injuries of either cervical vertebra.

Hydrogen embrittlement of a tapered roller bearing due to lubricant breakdown

This paper presents the results of an examination of a single row tapered roller bearing from a 650 t Face shovel swing transmission gearbox that exhibited an unusual pattern of axial fracture.The bearing sustained multiple axial fractures around the inner ring (cone) many of which exhibited a fracture face with a two tone pattern, suggesting a two stage fracture, comprising a dark internal region of lubricant discolouration and a bright fresh fracture border. SEM examination indicated the discoloured region to have fractured following an intergranular path consistent with hydrogen embrittlement arising from lubricant breakdown, while the border region exhibited a cleavage fracture.

Quantitative assessment of conditions for axial fracture formation during helical rolling

A technique has been developed for the quantitative assessment of piercing (P) based on the use of the values of the relative elongation &delta; at a temperature of 1200 &deg;C and the deformation rate corresponding to the conditions of piercing 1 s-1 and correction factors taking into account the state of the original workpiece, the composition of the deformation zone and the combined effect of the factors of the deformation area &mdash; the angle flow &beta; and ovalization ratio &xi; definitely. Based on the experimental results processed in the EXCEL program, the presence of four characteristic zone combinations of &beta; and &xi; has been established, which have the most significant effect on the critical compression ucr. The statistically significant values of the corresponding coefficients K1 and K2 have been established. An experimental assessment of the correction factor K3, which determines the combined effect of the factors of the deformation zone, has been carried out. The adequacy of the developed technique was checked using real conditions of piercing on TPA-140 with an automatic mill of JSC &ldquo;PNTZ&rdquo;, the correct use of the applied structure of the deformation area. The established criterion is P = 50 %, below which axial destruction occurs during piercing.

Dynamic Mechanics and Crystal Structure Fracture Characteristics of Rock-like Materials in Coal Mines

Deep rock bears dynamic loads such as machinery, blasting and disturbance in the mining process. The dynamic fracture mechanism of deep rock is a necessary prerequisite for engineering design and analysis. To study the dynamic fracture mechanism of rock under high in situ stress, deep mudstone and sandstone were selected as research objects. The dynamic mechanical properties and energy dissipation of mudstone sandstone were assessed by using a 50 mm diameter separated Hopkinson test device. According to the similarity criterion, the similarity of strength was assumed as primary factor to prepare similar model materials. Then, dynamic mechanical tests of these similar materials were carried out under dynamic compression splitting and active confining pressure. The results show that materials similar to mudstone and sandstone mainly show axial fracture tensile failure and crushing failure. Both the average strain rate dynamic strength and peak strain of these similar materials increase with increasing impact pressure, and the dynamic strength of similar materials increases exponentially with increasing strain rate. This result is consistent with the regularity of original rock. The dynamic splitting of mudstone-like materials is dominated by the failure of intermediate cracks, and sandstone-like materials also show secondary cracks in addition to intermediate splitting cracks. The dynamic peak strength of mudstone-like materials increases with increasing active confining pressure, and the dynamic peak strength of sandstone-like materials increases nearly twofold under the action of active confining pressure.

A multicenter cohort analysis of fractures in histamine-2-receptor antagonist treated pediatric patients

Background Histamine 2 receptor antagonists (H2RA) are amongst the most entrenched antacid therapies available including over-the-counter. They have an excellent safety profile including no known teratogenic risk. Fracture risk is generally recognized with chronic proton pump inhibitor (PPI) therapy in adults and children although the related mechanism is poorly understood. The analogous risk in H2RAs, including in children, is unclear. We studied the fracture risk and characteristics among hospitalized pediatric patients exposed to H2RA compared to an untreated cohort. Methods The Pediatric Health Information System (PHIS) multicenter database was queried for hospital encounters of children aged 6 months − 15.5 years and between 7/2016 and 8/2017. Patients with comorbidities and medications including PPI that predispose for fractures were excluded from the cohort and a propensity-matched control was identified. The subjects and controls were followed for 2 years for hospitalization with fracture diagnoses. Results Our cohort included 3526 patients with exposure to H2RA and matched controls. Fractures were reported in 1% of patients (67) with no statistical difference between the groups. Upper, then lower extremity fractures were the most common in both groups. Axial skeleton fractures were the least frequently encountered fractures among both groups. Conclusion H2RA exposure is not associated with an increased risk of fracture in hospitalized children exposed to H2RA when compared with a matched untreated cohort, further studies are needed to determine if long-term exposure to H2RA may be associated with fracture risk in both those with and without comorbidities or on fracture predisposing medication.

The impact of variable density in-plane perforations on fracture propagation and complexity control in the horizontal well

To understand the fracture behavior for variable density in-plane perforations on a horizontal well, true triaxial hydraulic fracturing experiments were performed with acoustic emission monitoring. The experimental results indicate that the variable density in-plane perforations can not only create transverse fractures but also arrest fracture propagation toward undesirable zones. The in situ stress and treatment parameters play significant roles in the fracture morphology and breakdown pressure. Under a large horizontal principal stress difference, there is a high possibility for simple transverse fracture creation, which results in a lower breakdown pressure. Moreover, the decrease in fracturing fluid viscosity can increase the fracture complexity and increase in pump rate can increase breakdown pressure and induce the complex fracture geomtetry. The acoustic emission (AE) characteristics and cutting fracture morphology demonstrate that not all perforations can be successfully initiated during the fracturing process. Because of the stress interaction from side perforations, fracture initiation and propagation from the middle perforation are strongly suppressed. Although the middle fracture is not fully initiated and propagated, it is still beneficial for the side hydraulic fracture connection and propagation in one plane. Secondary and axial fractures can still be observed, primarily due to the stress interaction between neighboring perforations and misalignment of the perforation tunnel orientation with the principal stress direction. In addition, the creation of complex fractures tends to occur using a high pump rate, which relates to tense fluid distribution competition from each perforation tunnel. Fracture initiation may follow an order but mostly tends to initiate from side perforations. Because of the stress interaction, hydraulic fractures from the side perforation can sometimes deviate from the perforation tunnel direction, twist and kink, and finally, generate nonplanar fractures. A large horizontal principal stress difference is recommended and beneficial for simple, straight and planar fracture creation during hydraulic fracturing stimulation with variable density in-plane completion for the horizontal well.

Fracture toughness evaluation of 37CrNi3MoVE steel used for high-pressure air storage cylinder

The air storage cylinders, forming part of the impulse air system for submarine, are high-pressure steel cylinders dome-shaped at each end. To prevent the risk of cylinders rupture, the fracture toughness of cylinders is necessary to be tested. The three-point bending samples used in the fracture toughness experiment were taken from a cylinder made of 37CrNi3MoVE steel. With the consideration of the effect of the manufacturing process, both axial specimens and circumferential specimens were sampled, and the fracture toughness was compared. The effective data obtained from fracture toughness experiments were processed by different standards, such as ISO 12135 standard and ASTM E1820 standard. The fracture surface is analyzed from macroscopic and microscopic perspectives. From the test results of circumferential fracture toughness and axial fracture toughness, it can be clearly seen that under the influence of the processing technology, the circumferential fracture toughness of the cylinder of the high-pressure gas cylinder is smaller than the circumferential fracture toughness. Finally, comparing the fracture toughness values obtained by the ASTM E1820 standard with the fracture toughness values obtained by the ISO 12135 standard, it is found that the fracture toughness values obtained under the ASTM E1820 standard are all greater than the fracture toughness values obtained by the ISO 12135 standard.

Mechanism analysis and prediction of explosive formed projectile’s axial fracture

To explain the axial fracture phenomenon of Explosively Formed Projectile (EFP), the fracture mechanism of long rod EFP during the forming phase is analyzed by the stress wave theory. When the velocity gradient [Formula: see text] between the head and tail parts exceeds the critical value [Formula: see text], the EFP would fracture in the axial direction. Based on the Johnson–Cook constitutive model parameters and the special conditions in the forming phase of EFP, the critical velocity gradient [Formula: see text] can be determined by theoretical calculation and then validated by experimental results for both copper and tantalum EFPs. The experimental results for EFP’s fracture agree well with the prediction of the theoretical analysis. The theoretical analysis method can be applied as an important measure to determine the critical velocity gradient and predict the fracture of long rod EFP, providing reference for the application of new kinds of high density materials in the EFP research area.

Tensile Failure and Fracture Width of Partially Permeable Wellbores with Applications in Lost Circulation Material Design

SummaryEstimation of near-wellbore fracture widths remains central to designing the particle size distribution (PSD) and composition of lost circulation material (LCM) blends. Although elastic rock models are often used for this purpose, they fall short in capturing the substantial effect of pore fluid pressure on the fracture width. The problem is addressed in this paper by incorporating the poroelastic back stress in width estimation of axial fractures nearby an inclined wellbore. The poroelastic back stress is caused by a nonideal drilling fluid filter cake allowing for fluid pressure communication between the wellbore and pore space of the rock surrounding the wellbore. In this aspect, a proper definition of the filter-cake efficiency is made in terms of the wellbore pressure, far-field pore fluid pressure, and pore fluid pressure of the rock surrounding the wellbore. The value of this parameter is estimated from the standard drilling fluid filtration test results, as well as the formation rock permeability. The filter-cake efficiency is next used to develop the long-time, asymptotic analytical solution for the poroelastic stress of an inclined wellbore. By accounting for the obtained poroelastic back stress, an improved estimation of the wellbore tensile limit that depends on the filter-cake efficiency parameter is developed. For wellbore pressures beyond the wellbore tensile limit, the width of the near-wellbore fractures is estimated. The fracture width estimation is made through an analytical, dislocation-based fracture mechanics solution to the integral equation describing the nonlocal stress equilibrium along the fracture faces. The commonly practiced scheme for geometric design of LCM blends is enhanced by using the presented improvement in estimation of the near-wellbore fracture width. A case study is used to demonstrate the substantial effect of drilling fluid filtration properties and the resulting poroelastic back stress on the wellbore tensile limit, estimated fracture width, and consequently, composition of the recommended LCM blend.

Surgical Outcomes for C2 Tear Drop Fractures: Clinical Relevance to Hangman's Fracture and C2-3 Discoligamentous Injury.

ObjectiveTo analyze characteristics of surgically managed tear drop (TD) fractures of the C2 axis associated with other injuries such as hangman's fracture and C2‐3 discoligamentous injury as well as treatment outcomes.MethodsA total of 14 patients (eight men and six women) with TD fractures of the C2, who were surgically treated at four national trauma centers of tertiary university hospitals from January 2000 to December 2017, were included in this retrospective study. The mean age of the patients was 45.5 years (ranging from 19 to 74 years). The characteristics, surgical treatment methods (anterior fusion vs posterior fusion), and results of 14 TD fractures of the C2 were analyzed retrospectively. And the clinical relevance between C2 TD fracture and hangman's fracture and C2‐3 discoligamentous injury was investigated through the co‐occurrence between injuries. The mean follow‐up time after surgery was 22.6 months (ranging from 12 to 60 months).ResultsAmong 14 patients with TD fracture of the C2, four patients (28.6%) had anterior TD fracture and 10 patients (71.4%) had posterior TD fracture. All 10 posterior TD fracture patients had anterior C2‐3 displacement. While two of four anterior TD fracture patients had posterior C2‐3 displacement, the remaining two did not. All 14 patients of TD fracture had at least two or more other associated C2 injuries as well as C2‐3 discoligamentous injuries. About 92.9% (13/14) of the patients had typical or atypical hangman's fracture; 100% (10/10) of the posterior TD fracture patients had hangman's fracture, but 75% (3/4) of the anterior TD fracture had hangman's fracture. At admission, 13 patients were neurologically intact. However, the remaining patient had spinal cord injury with American Spinal Injury Association (ASIA) impairment scale B with C2‐3 bilateral facet dislocation. All four anterior TD fracture patients underwent posterior C2‐3 fusion. While four of 10 posterior TD fracture patients underwent C2‐3 anterior fusion, the remaining six underwent posterior fusion. At last follow‐up, 100% (14/14) of the patients achieved solid fusion, and visual analog scale for neck pain was significantly improved (5.9 vs 2.2, P < 0.001). One patient with ASIA impairment scale B had significantly improved to scale D. No major complications occurred.ConclusionOur study showed that surgically managed TD fractures of the C2 showed a high incidence of other associated spine injuries including hangman's fracture and C2‐3 discoligamentous injury. Therefore, special attention and careful radiologic evaluation are needed to investigate the presence of other associated spine injuries including hangman's fracture and C2‐3 discoligamentous injury, which are likely to require surgery.

Fracture resistance of endodontically treated teeth with cervical defects using different restorative treatments

Background/purposeThe restoration of endodontically treated teeth (ETT) with cervical defects has been a challenge for dentists. The purpose of this study was to evaluate the effect of restorative treatment on the fracture resistance of ETT with cervical defects. Materials and methodsOne hundred and twenty freshly extracted human intact straight-single-root maxillary premolars were randomly divided into 6 groups. Group 1 remained untreated. Cervical defects of 4 mm-depth and 3 mm-height were created in groups 2–6. Group 3–6: root canal treatment. Group 4: direct composite resin restoration. Group 5: 2-mm full-cusp-coverage composite resin restoration. Group 6: fiber-post-supported composite resin restoration. A static fracture test was used to determine the fracture resistance of teeth under axial (n = 10) and palatal (30°) (n = 10) loading. Fracture modes were categorized as restorable and unrestorable. ResultsCompared with intact teeth, the axial fracture resistance of teeth with cervical defects decreased by approximately 39%, and endodontic procedures resulted in 10% more reduction. When ETT with cervical defects were restored using direct composite resin filling, the axial fracture resistance recovered to 72% of that of intact teeth, but no significant change occurred under oblique loading. After full-cusp-coverage or fiber-post-supported restoration, fracture resistance showed complete recovery to the value of intact teeth (P > 0.05). Sixty percent of fractures were unrestorable for fiber-post-supported teeth, while in the full-cusp-coverage restoration group, 80–90% of fractures were restorable. ConclusionFull-cusp-coverage restoration or fiber-post-supported restoration could improve the fracture resistance of ETT with cervical defects, whereas unrestorable fractures easily occurred in fiber-post-supported restorations.

Mechanical behavior and failure mechanism of the 3D angle interlocking woven reinforced aluminum matrix composites under in-plane tensile loading

3D angle interlocking fabric reinforced aluminum composites were prepared by the vacuum assisted pressure infiltration method. The mechanical properties and damage behavior of the composites subjected to in-plane tensile loading were investigated using the micromechanical finite element simulation and experimental method. The results show that the tensile stress-strain curve from simulation is in agreement with the testing curves, where the calculation errors of the initial modulus, ultimate strength and fracture strain in warp (weft) direction are 3.96%(1.11%), 1.40%(6.86%) and −5.49%(3.73%), respectively. Under the warp directional tension condition, the interface on warp yarns and the adjoint matrix alloy damage successively. With the increase of tensile strain, these damage zones accumulate and interact with each other, leading to the failure of interface, matrix and weft yarns in sequence. The fracture of warp yarns in the terminate stage induces the ultimate failure of the composites. During the weft directional tensile process, the interface on warp yarns and the thin matrix alloy between yarns damage and fail firstly. The transverse fracture of warp yarns occurs in the middle stage of tensile deformation. The axial fracture of weft yarns, which sustain the loading stress at the end of deformation process, is the main failure mechanism of the composites under weft directional tensile condition. The tensile modulus and strength in weft direction are 81.8% and 56.5% times than those in warp direction, owing to the lower volume fraction of weft yarns in the 3D angle interlocking fabric.

Conservative treatment of ulnar styloid fractures following volar-plate fixation of distal radius fractures: incidence of nonunion evaluated by computed tomography

The first aim of this study was to investigate the incidence of ulnar styloid fractures (USFs) accompanied by distal radius fractures (DRFs), treated with volar locking plates. The fracture type of DRFs was evaluated by the classifications, based on computed tomography (CT) scan findings. The second aim was to investigate the bone union rate of USFs, depending on the fracture type of DRFs, by comparing union and nonunion groups in the USFs groups. Between May 2012 and December 2019, 239 consecutive patients with DRFs were treated. Of these patients, 177 DRFs met inclusion criteria. The fracture patterns of the DRFs, based on the classification, using CT scans, which included the AO classification, sagittal angulation, and axial fracture patterns of the articular surface of the distal radius in two-part intra-articular fractures were evaluated. The size of USFs, classified as a tip or base fracture was also investigated. The incidence of USFs was significantly higher for AO types A and C than for type B. Analysis of the sagittal angulation of DRFs showed that the incidence of USFs was higher for the extension type than for the flexion type. Axial CT classification of two-part fractures revealed that DRFs with a dorsal fracture line was more frequent than the volar type of DRFs. These results suggested that dorsal displacement of DRFs was associated with a higher incidence of USFs. Finally, the analysis of the bone union rate of USFs revealed that AO classification and sagittal angulation were not correlated with bone union in USFs. However, it was found that a fracture line on the radial side of the radius had a significantly low rate of bone union, compared to a fracture line on the dorsal side. The size of USFs was also not correlated with the bone union rate. The incidence and the bone union rate of USFs have different patterns. The incidence of USFs was higher in the dorsal displacement type of DRFs. However, the bone union rate of USFs was lower for a fracture line on the radial side. Therefore, USFs with DRFs that have a fracture line on the radial side is a candidate for fixation to prevent nonunion.

C1-C2 Wiring With Timed Self-Obsolescence for Complex C2 Body Fracture.

Fractures of C2 are typically managed nonoperatively with good rates of healing. Management decisions are complicated, however, when there are additional fractures in the axis possibly leading to increased instability. Additionally, the techniques used for treating these unstable axis fractures can have either significant complications or permanent loss of range of motion. Here, we present a novel technique for the reduction and stabilization of complex C2 body fracture. A 34-yr-old woman with a complex C2 body fracture, which included a right pars and left lateral mass fracture, presented after a water slide accident. It was felt that this fracture was both unstable and would not heal in an anatomically acceptable way so an open surgical reduction was needed. After consideration of more traditional fusion and osteosynthesis techniques, we chose to perform a C1-C2 internal stabilization with C1 sublaminar and C2 spinous process wiring. The patient was then instructed to wear a Miami J collar for 3 mo. The outcome was favorable with good approximation and healing with preserved range of motion.

Axial Fracture Initiation During Diagnostic Fracture Injection Tests and Its Impact on Interpretations

Axial Fracture Initiation During Diagnostic Fracture Injection Tests and Its Impact on Interpretations

Mortality related to and functional outcomes of upper cervical spine fractures in the elderly

BackgroundAlthough the mortality related to hip fracture and osteoporotic vertebral fracture have been reported, few studies have examined the mortality related to atlas and/or axis fractures. The aim of this study was to assess the association between mortality and atlas and/or axis fractures retrospectively and to elucidate the efficacy of surgical treatment. MethodsA total of 33 elderly patients who were treated for atlas and/or axis fractures at our institution between January 2012 and December 2018 were included in this study. These patients were divided into two groups: surgical treatment and conservative treatment. Fracture types, comorbidities, neurological status, treatment types, and walking ability at follow-up were reviewed. Mortality was assessed using medical records or via phone interviews. ResultsThe mean age at injury was 79.9 ± 8.0 years, and the mean follow-up period was 2.3 years. The overall mortality rates at 1 and 5 years were 21.4% and 48.4%, respectively. During the observation period, 12 (36%) patients died. Twenty-two patients were treated conservatively (14 were treated with a cervical collar, 8 were treated with a halo vest). Surgical procedures included occipital-cervical fixation, osteosynthesis of C2 fractures, C1–2 fixation, and C1–4 fixation using a posterior approach. Surgical treatment correlated with better survival rates. There was no significant difference between the two groups in terms of ambulatory ability and functional recovery. ConclusionUpper cervical spine fractures appear to have a worse prognosis compared to hip and osteoporotic vertebral fractures. This study indicates the efficacy of surgical treatment for upper cervical spine fractures in the elderly for improving survival prognosis.

30-day and 1-year mortality after skeletal fractures: a register study of 295,713 fractures at different locations

Background and purpose — Few studies have reported the mortality rate after skeletal fractures involving different locations, within the same population. We analyzed the 30-day and 1-year mortality rates following different fractures. Patients and methods — We included 295,713 fractures encountered in patients 16–108 years of age, registered in the Swedish Fracture Register (SFR) from 2012 to 2018. Mortality rates were obtained by linkage of the SFR to the Swedish Tax Agency population register. The standardized mortality ratios (SMR) at 30 days and 1 year were calculated for fractures in any location and for each of 27 fracture locations, using age- and sex-life tables from Statistics Sweden (www.scb.se). Results — The overall SMR at 30 days was 6.8 (95% CI 6.7–7.0) and at 1 year 2.2 (CI 2.2–2.2). The SMR was > 2 for 19/27 and 13/27 of the fracture locations at 30 days and 1 year, respectively. Humerus, femur, and tibial diaphysis fractures were all associated with high SMR, at both 30 days and 1 year. Interpretation — Patients sustaining a fracture had approximately a 7-fold increased mortality at 30 days and over 2-fold increased mortality at 1 year as compared with what would be expected in the general population. High mortality rates were seen for patients with axial skeletal and proximal extremity fractures, indicating frailty in these patient groups.

No more rattling: biomechanical evaluation of a hexapod ring fixator free of play.

Hexapod-ring-fixators have a characteristic rattling sound during load changes due to play in the hexapod struts. This play is perceived as unpleasant by patients and can lead to frame instability. Using slotted-ball-instead of universal-joints for the ring-strut connection could potentially resolve this problem. The purpose of the study was to clarify if the use of slotted-ball-joints reduces play and also fracture gap movement. A hexapod-fixator with slotted-ball-joints and aluminum struts (Ball-Al) was compared touniversal-joint-fixators with either aluminum (Uni Al) orsteel struts (Uni Steel). Six fixator frames each were loaded in tension, compression, torsion, bending and shear andmechanical performance was analyzed in terms of movement, stiffness and play. The slotted-ball-joint fixator wasthe only system without measurable axial play(<0.01mm) compared to Uni-Al (1.2±0.1)mm and Uni-Steel (0.6±0.2)mm (p≤0.001). In both shear directions the Uni-Al had the largest play (p≤0.014). The resulting axial fracture gap movements were similar for the two aluminum frames and up to 25% smaller for the steel frame, mainly due to the highest stiffness found for the Uni-Steel in allloading scenarios (p≤0.036). However, the Uni-Steel construct was also up to 29% (450g) heavier and had fewer usable mounting holes. In conclusion, the slotted-ball-joints of the Ball-Al fixator reduced play and minimized shear movement in the fracture while maintaining low weight of the construct. The heavier and stiffer Uni-Steel fixator compensates for existing play with a higher overall stiffness.

PEDIATRIC ORTHOPAEDIC TRAUMA AND ASSOCIATED INJURIES AT AN INNER-CITY LEVEL 1 TRAUMA CENTER

Background/Purpose:Pediatric orthopaedic trauma in inner city communities often present with unique and modifiable risk factors. The purpose of this study was to characterize and evaluate the pattern and nature of orthopaedic and associated injuries in pediatric patients involved in motor vehicle accidents (MVA), falls, sports related injuries and pedestrian struck either on foot or on bicycle at an inner-city level 1 trauma center.Methods:260 pediatric patients who presented to the emergency department after a fall, a sports related injury, MVA, pedestrian struck on foot (PSoF), or pedestrians struck on bicycle (PSoB) with orthopaedic injuries at our institution between 2013 and 2020 were retrospectively reviewed.Results:The mean age of our cohort was 9.1 years (SD ±4.60). 36.5% (95/260) were girls, 63.5% (165/260) were boys. There were a total of 260 patients with a total of 331 fractures. 96.3% (319/331) of the fractures were appendicular while 3.6% (12/331) were axial. 43.8% (114/260) of patients had lower extremity fractures and 49.2% (128/260) had upper extremity fractures. Of all mechanisms, MVAs were most commonly associated with axial fractures (p<0.01). Falls were associated most commonly with upper extremity fractures (p<0.01), lower patient age (p<0.01) and negatively correlated with lower extremity fractures (p<0.01). Sports related injuries were most commonly correlated with tibia fractures (p<0.01). Sports etiologies were subdivided into Basketball (29%), Football (27%), Soccer (11%), and other physical activities like Rollerblading (11%) and Skateboarding (9%). PSoF was associated with tibia fractures (p<0.05) and open fractures (p<0.01). PSoB was the most likely mechanism to lead to lower extremity fractures (p=0.01) and head trauma (p<0.01). 75% (6/8) of PSoB were not wearing a helmet at the time of injury.Conclusion:Not surprisingly, falls represent the most common mechanism of pediatric orthopaedic injury. Other mechanism of injuries included MVAs, pedestrian struck on foot or bicycle were associated with more significant trauma including vertebral fractures, open fractures, head trauma and compartment syndrome. Preventative measures including education on car seat and seat belt use, helmet use and bicycle safety in children may reduce the incidence of these serious injuries.Figure 1.– Mechanism of Injury on a patient basis. Asterisk signifies statistical significance.