Navigating the Enigma of Pediatric Musculoskeletal Infections: A Race Against Time

Musculoskeletal infection (MSKI) in children is a critical condition in pediatric orthopedics due to the potential for serious adverse outcomes, including multiorgan dysfunction syndrome, which can lead to death. The diagnosis and treatment of MSKI continue to evolve with advancements in infectious organisms, diagnostic technologies, and pharmacologic treatments. It is imperative for pediatric orthopedic surgeons and medical teams to remain up to date with the latest MSKI practices.

Sequestration and Involucrum: Understanding Bone Necrosis and Revascularization in Pediatric Orthopedics

Sequestration, a condition where a section of bone becomes necrotic due to a loss of vascularity or thrombosis, can be a challenging complication of osteomyelitis. This review explores the pathophysiology of sequestration, highlighting the role of the periosteum in forming involucrum and creeping substitution which facilitate revascularization and bone formation. The authors also discuss the induced membrane technique, a two-stage surgical procedure for cases of failed healing of sequestration. Future directions include the potential use of prophylactic anticoagulation and novel drugs targeting immunocoagulopathy, as well as the development of advanced imaging techniques and single-stage surgical procedures.

Tranexamic acid in trauma: After 3 hours from injury, when is it safe and effective to use again?

Tranexamic acid (TXA) has proven mortality benefit if used early after traumatic injury, likely related to a combination of bleeding reduction and other non-bleeding effects. If TXA is given more than 3 h after traumatic injury, there is a significant and paradoxical increased risk of death due to bleeding. TXA has level 1 evidence for use as a bleeding reduction agent in isolated orthopedic operations, but in polytrauma patients undergoing orthopedic operations, it is not clear if and when TXA is safe or effective once outside the 3-h window of proven trauma efficacy.

CRP Predicts the Need to Escalate Care After Initial Debridement for Musculoskeletal Infection

BACKGROUND

Musculoskeletal infections (MSKIs) are a major cause of morbidity in the pediatric population and account for nearly 1 in every 10 consultations with a pediatric orthopaedic provider at a tertiary care center. To prevent or deescalate the risk of adverse medical and musculoskeletal outcomes, timely medical intervention in the form of antibiotics and potential surgical debridement is required. While there have been numerous studies indicating the value of laboratory testing during the initial workup of a child with MSKI, few studies to date have examined the utility of longitudinal assessment of laboratory measures in the acute setting to monitor the efficacy of antibiotic therapy and/or surgical intervention. The purpose of this investigation was to retrospectively determine whether measuring changes in the inflammatory response could indicate the need for escalated care. Specifically, this study examined the hypothesis that serial measurements of C-reactive protein (CRP), immediately preoperatively and 2 days after surgical debridement, could predict the need for medical (change in antibiotics) or surgical (additional debridement) escalation.

METHODS

Retrospective review of pediatric patients undergoing operative debridement for the treatment of MSKI between September 2009 and December 2015 from whom laboratory data (CRP) was obtained preoperatively and at postoperative day (POD) 2. Patient demographics, the need for escalated care, and patient outcomes were evaluated.

RESULTS

Across 135 pediatric patients, preoperative CRP values >90 mg/L and a positive change in CRP at POD2 effectively predicted the need for escalation of care after initial surgical debridement (Area under the Receiver Operator Curve: 0.883). For each 10-unit increase in preoperative CRP or postoperative change in CRP, there was a 21% or 22% increased risk of needing escalated care, respectively. Stratification by preoperative CRP >90 mg/L and change in CRP postoperatively likewise correlated with increased rates of disseminated disease, percent tissue culture positivity, length of stay, and rate of adverse outcomes.

CONCLUSIONS

This study demonstrates the utility of serial CRP to assess the need for escalated care in patients being treated for MSKI. As serial CRP measurements become standard of practice in the acute setting, future prospective studies are needed to optimize the timing of CRP reassessment during inpatient hospitalization to prognosticate patient outcomes, weighing both improvements of patient care and clinical burden.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Clinical Outcomes and Associated Pathologies Following Pediatric Traumatic Hip Dislocations: A Systematic Review of the Literature

INTRODUCTION

Pediatric traumatic hip dislocations are a rare condition that can have devastating short and/or long-term outcomes and associated pathologies (APs), including associated injuries (AIs) and long-term adverse events (LTAEs), with negative long-term sequelae. Currently, there are little data that exist on the rate of APs, with the most notable being avascular necrosis (AVN), for pediatric traumatic hip dislocations. The purpose of this systematic review is to evaluate the outcome relative frequency of dislocation direction, reduction type, and rate of APs for traumatic hip dislocations in the pediatric population.

METHODS

A systematic review on the topic of traumatic hip dislocations in the pediatric population was performed using PubMed, ScienceDirect, Web of Science, CINAHL, and MEDLINE databases from database inception to March 30, 2023. Inclusion criteria was full-text English articles, addressed traumatic hip dislocations, and pediatric patients (<18 y old).

RESULTS

A total of 24 articles (n=575 patients) met final inclusion criteria from a total of 219 articles retrieved from the initial search. For the average age of the included patients with reported age (n=433 patients), the frequency weighted mean was 9.50 years±1.75 years with a frequency weighted mean follow-up time of 74.05 months ±45.97 months (n=399 patients). The most common dislocation direction was posterior (86.4%), the most common treatment type was closed reduction (84.5%), AVN was the most common type of LTAEs (15.5% of APs), and labral/capsular injuries and acetabular fractures were the most common type of AIs (14.0% and 9.4% of APs, respectively). There were a combined total of 414 APs (72%) out of 575 total patients.

CONCLUSION

Pediatric traumatic hip dislocations are associated with a high rate of AIs and LTAEs (72%, 414 APs out of 575 patients). AVN, labral/capsular injuries, and acetabular fractures are the most common APs after pediatric traumatic hip dislocations. Pediatric hip dislocations are usually posterior and commonly managed through closed reduction.

LEVEL OF EVIDENCE

III, Systematic Review.

Growth factor free, peptide-functionalized gelatin hydrogel promotes arteriogenesis and attenuates tissue damage in a murine model of critical limb ischemia

Critical limb ischemia (CLI) occurs when blood flow is restricted through the arteries, resulting in ulcers, necrosis, and chronic wounds in the downstream extremities. The development of collateral arterioles (i.e. arteriogenesis), either by remodeling of pre-existing vascular networks or de novo growth of new vessels, can prevent or reverse ischemic damage, but it remains challenging to stimulate collateral arteriole development in a therapeutic context. Here, we show that a gelatin-based hydrogel, devoid of growth factors or encapsulated cells, promotes arteriogenesis and attenuates tissue damage in a murine CLI model. The gelatin hydrogel is functionalized with a peptide derived from the extracellular epitope of Type 1 cadherins. Mechanistically, these "GelCad" hydrogels promote arteriogenesis by recruiting smooth muscle cells to vessel structures in both ex vivo and in vivo assays. In a murine femoral artery ligation model of CLI, delivery of in situ crosslinking GelCad hydrogels was sufficient to restore limb perfusion and maintain tissue health for 14 days, whereas mice treated with gelatin hydrogels had extensive necrosis and autoamputated within 7 days. A small cohort of mice receiving the GelCad hydrogels were aged out to 5 months and exhibited no decline in tissue quality, indicating durability of the collateral arteriole networks. Overall, given the simplicity and off-the-shelf format of the GelCad hydrogel platform, we suggest it could have utility for CLI treatment and potentially other indications that would benefit from arteriole development.

Maintaining the balance: the critical role of plasmin activity in orthopedic surgery injury response

The musculoskeletal system plays vital roles in the body, facilitating movement, protecting vital structures, and regulating hematopoiesis and mineral metabolism. Injuries to this system are common and can cause chronic pain, loss of range of motion, and disability. The acute phase response (APR) is a complex process necessary for surviving and repairing injured musculoskeletal tissue. To conceptualize the APR, it is useful to divide it into 2 distinct phases, survival and repair. During the survival-APR, a "damage matrix" primarily composed of fibrin, via thrombin activity, is produced to contain the zone of injury. Once containment is achieved, the APR transitions to the repair phase, where reparative inflammatory cells use plasmin to systematically remove the damage matrix and replace it with new permanent matrices produced by differentiated mesenchymal stem cells. The timing of thrombin and plasmin activation during their respective APR phases is crucial for appropriate regulation of the damage matrix. This review focuses on evidence indicating that inappropriate exuberant activation of plasmin during the survival-APR can result in an overactive APR, leading to an "immunocoagulopathy" that may cause "immunothrombosis" and death. Conversely, preclinical data suggest that too little plasmin activity during the repair-APR may contribute to failed tissue repair, such as a fracture nonunion, and chronic inflammatory degenerative diseases like osteoporosis. Future clinical studies are required to affirm these findings. Therefore, the temporal-spatial functions of plasmin in response to musculoskeletal injury and its pharmacologic manipulation are intriguing new targets for improving orthopedic care.

Head and Neck Necrotizing Fasciitis: Abbreviated SOFA Score Associated With Death and Infection Spread

Objective

Describe features unique to head and neck (H&N) necrotizing fasciitis (NF) compared to other anatomic regions and specify a prognostic score associated with death and descending necrotizing mediastinitis (DNM).

Study Design

Retrospective cohort.

Setting

Tertiary care, level 1 trauma center.

Methods

A single-institution database identified 399 confirmed cases of NF between 2006 and 2021, 33 of which involved the H&N. Patients with confirmed H&N NF were sorted into cohorts based on clinical outcomes, with the "poor" outcomes group defined by death and/or DNM.

Results

Thirty-three patients with H&N NF were included. Compared to NF of other regions, patients with H&N NF had a significantly lower mortality rate (6.06% vs 20.8%, p = .041) and significantly lower rates of obesity (27.3% vs 63.7%, p < .001) and hypertension (42.4% vs 60.9%, p = .038). Within the H&N group, there were 2 deaths (6.06%) and 8 cases of DNM (24.2%). Diabetes was associated with poor outcomes (p = .047), as was an abbreviated sequential organ failure assessment score for necrotizing fasciitis (nfSOFA) of 2 or greater (p = .015).

Conclusion

H&N NF is unique among other forms of NF, with a lower mortality rate and lower rates of obesity and hypertension in affected patients. Within the H&N cohort, worse outcomes were associated with diabetes as well as a nfSOFA score of 2 or greater. Timely surgical debridement alongside broad-spectrum antibiotics remains the mainstay of treatment for NF; however, this simple prognostic score may play a role during the early stages of care for patients with H&N NF.

Age and CRP Associated With Improved Tissue Pathogen Identification in Children With Blood Culture Negative Osteomyelitis: Results From the CORTICES Multicenter Database

BACKGROUND

Acute hematogenous osteomyelitis (AHO) is a relatively common condition in children, and identifying the offending pathogen with blood or tissue cultures aids in diagnosis and medical management while reducing treatment failure. Recent 2021 AHO clinical practice guidelines from the Pediatric Infectious Disease Society recommend obtaining routine tissue cultures, particularly in cases with negative blood cultures. The purpose of this study was to identify variables associated with positive tissue cultures when blood cultures are negative.

METHODS

Children with AHO from 18 pediatric medical centers throughout the United States through the Children's ORthopaedic Trauma and Infection Consortium for Evidence-based Study were evaluated for predictors of positive tissue cultures when blood cultures were negative. Cutoffs of predictors were determined with associated sensitivity and specificity.

RESULTS

One thousand three children with AHO were included, and in 688/1003 (68.6%) patients, both blood cultures and tissue cultures were obtained. In patients with negative blood cultures (n=385), tissue was positive in 267/385 (69.4%). In multivariate analysis, age (P<0.001) and C-reactive protein (CRP) (P=0.004) were independent predictors. With age >3.1 years and CRP >4.1 mg/dL as factors, the sensitivity of obtaining a positive tissue culture when blood cultures were negative was 87.3% (80.9-92.2%) compared with 7.1% (4.4-10.9%) if neither of these factors was present. There was a lower ratio of methicillin-resistant Staphylococcus aureus in blood culture-negative patients who had a positive tissue culture 48/188 (25.5%), compared with patients who had both positive blood and tissue cultures 108/220 (49.1%).

CONCLUSION

AHO patients with CRP ≤ 4.1 mg/dL and age under 3.1 years are unlikely to have clinical value from tissue biopsy that exceeds the morbidity associated with this intervention. In patients with CRP > 4.1 mg/dL and age over 3.1 years, obtaining a tissue specimen may add value; however, it is important to note that effective empiric antibiotic coverage may limit the utility of positive tissue cultures in AHO.

LEVEL OF EVIDENCE

Level III-Retrospective comparative study.

Growth factor-free, peptide-functionalized gelatin hydrogel promotes arteriogenesis and attenuates tissue damage in a murine model of critical limb ischemia

Critical limb ischemia (CLI) occurs when blood flow is restricted through the arteries, resulting in ulcers, necrosis, and chronic wounds in the downstream extremities. The development of collateral arterioles (i.e. arteriogenesis), either by remodeling of pre-existing vascular networks or de novo growth of new vessels, can prevent or reverse ischemic damage, but it remains challenging to stimulate collateral arteriole development in a therapeutic context. Here, we show that a gelatin-based hydrogel, devoid of growth factors or encapsulated cells, promotes arteriogenesis and attenuates tissue damage in a murine CLI model. The gelatin hydrogel is functionalized with a peptide derived from the extracellular epitope of Type 1 cadherins. Mechanistically, these "GelCad" hydrogels promote arteriogenesis by recruiting smooth muscle cells to vessel structures in both ex vivo and in vivo assays. In a murine femoral artery ligation model of CLI, delivery of in situ crosslinking GelCad hydrogels was sufficient to restore limb perfusion and maintain tissue health for 14 days, whereas mice treated with gelatin hydrogels had extensive necrosis and autoamputated within 7 days. A small cohort of mice receiving the GelCad hydrogels were aged out to 5 months and exhibited no decline in tissue quality, indicating durability of the collateral arteriole networks. Overall, given the simplicity and off-the-shelf format of the GelCad hydrogel platform, we suggest it could have utility for CLI treatment and potentially other indications that would benefit from arteriole development.

Advancing Tissue Factor-targeted Therapy for Osteosarcoma via Understanding its Role in the Tumor Microenvironment

Coagulation activation is associated with cancer progression and morbidity. Recently, mechanisms through which coagulation proteases drive the tumor microenvironment (TME) have been elucidated. This study aims to develop a new strategy dependent on the coagulation system for treating osteosarcoma (OS). We focused on tissue factor (TF), the main initiator of the extrinsic coagulant pathway, as a target for OS treatment. It was found that cell surface-TF, TF-positive extracellular vesicles, and TF-positive circulating tumor cells could drive progression, metastasis, and TME in carcinomas, including OS. Thus, targeting tumor-associated coagulation by focusing on TF, the principle catalyst of the extrinsic pathway, TF is a promising strategy treatment for OS.

Measures of Admission Immunocoagulopathy as an Indicator for In-Hospital Mortality in Patients with Necrotizing Fasciitis: A Retrospective Study

Necrotizing fasciitis is a rapidly progressive infection with a high mortality rate. Pathogens evade the host containment and bactericidal mechanisms by hijacking the coagulation and inflammation signaling pathways, leading to their rapid dissemination, thrombosis, organ dysfunction, and death. This study examines the hypothesis that measures of immunocoagulopathy upon admission could aid in the identification of patients with necrotizing fasciitis at high risk for in-hospital mortality.

Methods

Demographic data, infection characteristics, and laboratory values from 389 confirmed necrotizing fasciitis cases from a single institution were analyzed. A multivariable logistic regression model was built on admission immunocoagulopathy measures (absolute neutrophil, absolute lymphocyte, and platelet counts) and patient age to predict in-hospital mortality.

Results

The overall in-hospital mortality rate was 19.8% for the 389 cases and 14.6% for the 261 cases with complete measures of immunocoagulopathy on admission. A multivariable logistic regression model indicated that platelet count was the most important predictor of mortality, followed by age and absolute neutrophil count. Greater age, higher neutrophil count, and lower platelet count led to significantly higher risk of mortality. The model discriminated well between survivors and non-survivors, with an overfitting-corrected C-index of 0.806.

Conclusions

This study determined that measures of immunocoagulopathy and patient age at admission effectively prognosticated the in-hospital mortality risk of patients with necrotizing fasciitis. Given the accessibility of neutrophil-to-lymphocyte ratio and platelet count measurements determined from a simple complete blood-cell count with differential, future prospective studies examining the utility of these measures are warranted.

Level of Evidence

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Point-of-care diagnosis and monitoring of fibrinolysis resistance in the critically ill: results from a feasibility study

BACKGROUND

Fibrinolysisis is essential for vascular blood flow maintenance and is triggered by endothelial and platelet release of tissue plasminogen activator (t-PA). In certain critical conditions, e.g. sepsis, acute respiratory failure (ARF) and trauma, the fibrinolytic response is reduced and may lead to widespread thrombosis and multi-organ failure. The mechanisms underpinning fibrinolysis resistance include reduced t-PA expression and/or release, reduced t-PA and/or plasmin effect due to elevated inhibitor levels, increased consumption and/or clearance. This study in critically ill patients with fibrinolysis resistance aimed to evaluate the ability of t-PA and plasminogen supplementation to restore fibrinolysis with assessment using point-of-care ClotPro viscoelastic testing (VET).

METHODS

In prospective, observational studies, whole-blood ClotPro VET evaluation was carried out in 105 critically ill patients. In 32 of 58 patients identified as fibrinolysis-resistant (clot lysis time > 300 s on the TPA-test: tissue factor activated coagulation with t-PA accelerated fibrinolysis), consecutive experimental whole-blood VET was carried out with repeat TPA-tests spiked with additional t-PA and/or plasminogen and the effect on lysis time determined. In an interventional study in a patient with ARF and fibrinolysis resistance, the impact of a 24 h intravenous low-dose alteplase infusion on coagulation and fibrinolysis was prospectively monitored using standard ClotPro VET.

RESULTS

Distinct response groups emerged in the ex vivo experimental VET, with increased fibrinolysis observed following supplementation with (i) t-PA only or (ii) plasminogen and t-PA. A baseline TPA-test lysis time of > 1000 s was associated with the latter group. In the interventional study, a gradual reduction (25%) in serial TPA-test lysis times was observed during the 24 h low-dose alteplase infusion.

CONCLUSIONS

ClotPro viscoelastic testing, the associated TPA-test and the novel experimental assays may be utilised to (i) investigate the potential mechanisms of fibrinolysis resistance, (ii) guide corrective treatment and (iii) monitor in real-time the treatment effect. Such a precision medicine and personalised treatment approach to the management of fibrinolysis resistance has the potential to increase treatment benefit, while minimising adverse events in critically ill patients.

TRIAL REGISTRATION

VETtiPAT-ARF, a clinical trial evaluating ClotPro-guided t-PA (alteplase) administration in fibrinolysis-resistant patients with ARF, is ongoing (ClinicalTrials.gov NCT05540834 ; retrospectively registered September 15th 2022).

Early identification of life-threatening soft-tissue infection using dynamic fluorescence imaging: first-in-kind clinical study of first-pass kinetics

Necrotizing soft-tissue infections (NSTIs) are aggressive and deadly. Immediate surgical debridement is standard-of-care, but patients often present with non-specific symptoms, thereby delaying treatment. Because NSTIs cause microvascular thrombosis, we hypothesized that perfusion imaging using indocyanine green (ICG) would show diminished fluorescence signal in NSTI-affected tissues, particularly compared to non-necrotizing, superficial infections. Through a first-in-kind clinical study, we performed first-pass ICG fluorescence perfusion imaging of patients with suspected NSTIs. Early results support our hypothesis that ICG signal voids occur in NSTI-affected tissues and that dynamic contrast-enhanced fluorescence parameters reveal tissue kinetics that may be related to disease progression and extent.

Impact of the COVID-19 Pandemic on Pediatric Elbow Fractures: Marked Change in Management and Resource Utilization, Without a Change in Incidence

BACKGROUND

Elbow fractures are the most common pediatric fractures requiring operative treatment. Although recent reports have suggested that the COVID-19 pandemic has markedly reduced the incidence of pediatric fractures, no study has specifically evaluated the impact on pediatric elbow fractures. This study aimed to evaluate changes in the incidence, severity, and resource utilization for managing pediatric elbow fractures during the COVID-19 pandemic, compared with prepandemic years.

METHODS

A prepandemic (2007 to 2017) cohort and a COVID-19 pandemic period (March 2020 to March 2021) cohort of pediatric elbow injuries from a single tertiary hospital were retrospectively examined and compared. Exclusion criteria included outside treatment or lack of diagnosis by an orthopedist. Presentation information, injury patterns, transport, and treatment requirements were collected.

RESULTS

Although the incidence of pediatric elbow fractures and rate of neurovascular injury were comparable, seasonal patterns were not sustained and the rate of fracture displacement was found to be significantly elevated in the COVID-19 period compared with nonpandemic years. Likewise, marked changes to where patients first presented (emergency department vs. Clinic), how the patients were transported, and the distance traveled for care were observed. Specifically, patients were more likely to present to the clinic, were more likely to self-transport instead of using emergency medical service transportation, and traveled a greater distance for care, on average. Aligning with these changes, the resources utilized for the treatment of pediatric elbow fracture markedly changed during the COVID-19 period. This study found that there was an increase in the overall number of surgeries performed, the total operative time required to treat elbow fractures, and the number of patients requiring admission during the COVID-19 period.

CONCLUSIONS

These data provide a contrasting viewpoint to prior reports, illustrating that the incidence of elbow fractures remained consistent during the COVID-19 period, whereas the operative volume and need for hospital admission increased compared with years prior. Furthermore, this study demonstrated how the COVID-19 pandemic altered the interface between pediatric patients with elbow fractures and our institution regarding the location of presentation and transportation.

LEVEL OF EVIDENCE

Level III-retrospective cohort study.

Nonaccidental Trauma in Pediatric Elbow Fractures: When You Should Be Worried

BACKGROUND

Nonaccidental trauma (NAT) is a rising source of morbidity and mortality in the pediatric population. Fractures are often the first cause for presentation to health care providers in the case of NAT but can be misidentified as accidental. Given that elbow fractures are the most common accidental injuries among pediatric patients, they are not traditionally associated with NAT. This study aims to determine the prevalence of NAT among elbow fractures and identify common features in nonaccidental elbow fractures.

METHODS

Current Procedural Terminology (CPT) codes were used to retrospectively identify all pediatric (0 to 17) elbow fractures at a single, tertiary children's hospital between 2007 and 2017. Among these, all fractures for which an institutional child abuse evaluation team was consulted were identified. The medical record was then used to determine which of these fractures were due to NAT. Standard injury radiographs of all victims of NAT as well as all patients under 1 year of age were blinded and radiographically evaluated for fracture type by a pediatric orthopaedic surgeon.

RESULTS

The prevalence of nonaccidental elbow fractures across the 10-year study period was 0.4% (N=18). However, the prevalence of nonaccidental elbow fractures in those patients below 1 year of age was markedly higher at 30.3% (10/33). Among all elbow fractures in patients below 1 year of age, supracondylar humerus fractures were the most common fracture type (19/33, 57.6%), yet transphyseal fractures (6/33, 18.1%) were most commonly the result of NAT (5/6, 83.3%). In children over 1 year of age, fracture type was not an indicator of NAT.

CONCLUSIONS

The vast majority of pediatric elbow fractures (99.6%) are accidental. However, certain factors, namely age below 1 year and transphyseal fractures increase the likelihood that these fractures may be a result of NAT.

LEVEL OF EVIDENCE

Level IV: retrospective case series.

Variable Response to Antifibrinolytics Correlates with Blood-loss and Transfusion in Posterior Spinal Fusion

PURPOSE

Posterior spinal fusion (PSF) activates the fibrinolytic protease plasmin, which is implicated in blood loss and transfusion. While antifibrinolytic drugs have improved blood loss and reduced transfusion, variable blood loss has been observed in similar PSF procedures treated with the same dose of antifibrinolytics. However, both the cause of this and the appropriate measures to determine antifibrinolytic efficacy during high-blood-loss spine surgery are unknown, making clinical trials to optimize antifibrinolytic dosing in PSF difficult. We hypothesized that patients undergoing PSF respond differently to antifibrinolytic dosing, resulting in variable blood loss, and that specific diagnostic markers of plasmin activity will accurately measure the efficacy of antifibrinolytics in PSF.

METHODS

A prospective study of 17 patients undergoing elective PSF with the same dosing regimen of TXA was conducted. Surgery-induced plasmin activity was exhaustively analyzed in perioperative blood samples and correlated to measures of inflammation, bleeding, and transfusion.

RESULTS

While markers of in vivo plasmin activation (PAP and D-dimer) suggested significant breakthrough plasmin activation and fibrinolysis (P < 0.01), in vitro plasmin assays, including TEG, did not detect plasmin activation. In vivo measures of breakthrough plasmin activation correlated with blood loss (R2 = 0.400, 0.264; P < 0.01), transfusions (R2 = 0.388; P < 0.01), and complement activation (R2 = 0.346, P < 0.05).

CONCLUSIONS

Despite all patients receiving a high dose of TXA, its efficacy among patients was variable, indicated by notable intra-operative plasmin activity. Markers of in vivo plasmin activation best correlated with clinical outcomes. These findings suggest that the efficacy of antifibrinolytic therapy to inhibit plasmin in PSF surgery should be determined by markers of in vivo plasmin activation in future studies.

LEVEL OF EVIDENCE

Level II-diagnostic.

Sustained local ionic homeostatic imbalance caused by calcification modulates inflammation to trigger heterotopic ossification

Heterotopic ossification (HO) is a condition triggered by an injury leading to the formation of mature lamellar bone in extraskeletal soft tissues. Despite being a frequent complication of orthopedic and trauma surgery, brain and spinal injury, the etiology of HO is poorly understood. The aim of this study is to evaluate the hypothesis that a sustained local ionic homeostatic imbalance (SLIHI) created by mineral formation during tissue calcification modulates inflammation to trigger HO. This evaluation also considers the role SLIHI could play for the design of cell-free, drug-free osteoinductive bone graft substitutes. The evaluation contains five main sections. The first section defines relevant concepts in the context of HO and provides a summary of proposed causes of HO. The second section starts with a detailed analysis of the occurrence and involvement of calcification in HO. It is followed by an explanation of the causes of calcification and its consequences. This allows to speculate on the potential chemical modulators of inflammation and triggers of HO. The end of this second section is devoted to in vitro mineralization tests used to predict the ectopic potential of materials. The third section reviews the biological cascade of events occurring during pathological and material-induced HO, and attempts to propose a quantitative timeline of HO formation. The fourth section looks at potential ways to control HO formation, either acting on SLIHI or on inflammation. Chemical, physical, and drug-based approaches are considered. Finally, the evaluation finishes with a critical assessment of the definition of osteoinduction. STATEMENT OF SIGNIFICANCE: The ability to regenerate bone in a spatially controlled and reproducible manner is an essential prerequisite for the treatment of large bone defects. As such, understanding the mechanism leading to heterotopic ossification (HO), a condition triggered by an injury leading to the formation of mature lamellar bone in extraskeletal soft tissues, would be very useful. Unfortunately, the mechanism(s) behind HO is(are) poorly understood. The present study reviews the literature on HO and based on it, proposes that HO can be caused by a combination of inflammation and calcification. This mechanism helps to better understand current strategies to prevent and treat HO. It also shows new opportunities to improve the treatment of bone defects in orthopedic and dental procedures.

Effect of Intramedullary Nailing Patterns on Interfragmentary Strain in a Mouse Femur Fracture: A Parametric Finite Element Analysis

Delayed long bone fracture healing and nonunion continue to be a significant socioeconomic burden. While mechanical stimulation is known to be an important determinant of the bone repair process, understanding how the magnitude, mode, and commencement of interfragmentary strain (IFS) affect fracture healing can guide new therapeutic strategies to prevent delayed healing or nonunion. Mouse models provide a means to investigate the molecular and cellular aspects of fracture repair, yet there is only one commercially available, clinically-relevant, locking intramedullary nail (IMN) currently available for studying long bone fractures in rodents. Having access to alternative IMNs would allow a variety of mechanical environments at the fracture site to be evaluated, and the purpose of this proof-of-concept finite element analysis study is to identify which IMN design parameters have the largest impact on IFS in a murine transverse femoral osteotomy model. Using the dimensions of the clinically relevant IMN as a guide, the nail material, distance between interlocking screws, and clearance between the nail and endosteal surface were varied between simulations. Of these parameters, changing the nail material from stainless steel (SS) to polyetheretherketone (PEEK) had the largest impact on IFS. Reducing the distance between the proximal and distal interlocking screws substantially affected IFS only when nail modulus was low. Therefore, IMNs with low modulus (e.g., PEEK) can be used alongside commercially available SS nails to investigate the effect of initial IFS or stability on fracture healing with respect to different biological conditions of repair in rodents.

Practice Variation in the Surgical Management of Children With Acute Hematogenous Osteomyelitis

INTRODUCTION

The surgical indications to manage children with acute hematogenous osteomyelitis (AHO) remain poorly defined. The purpose of this study was to identify if practice pattern variation exists in the surgical management of pediatric AHO among tertiary pediatric medical centers across the United States. A secondary purpose was to evaluate variables that may impact the rate of surgical intervention among these institutions.

METHODS

Children with AHO were retrospectively analyzed between January 1, 2010, and December 31, 2016, from 18 pediatric medical centers throughout the United States. The rates of surgery were identified. Admission vitals, labs, weight-bearing status, length of stay, and readmission rates were compared between those who did and did not undergo surgery. Multivariate regression and classification and regression tree analyses were performed to identify the variables that were associated with surgical intervention.

RESULTS

Of the 1003 children identified with AHO in this retrospective, multicenter database, 619/1003 (62%) were treated surgically. Multivariate analysis revealed institution, inability to ambulate, presence of multifocal infection, elevated admission C-reactive protein, increased admission platelet count, and location of the osteomyelitis were significant predictors of surgery (P<0.01). Patients who underwent surgery were more than twice as likely to have a recurrence or readmission and stayed a median of 2 days longer than those who did not have surgery. In the classification and regression tree analysis, 2 distinct patterns of surgical intervention were identified based on institution, with 12 institutions operating in most cases (72%), regardless of clinical factors. A second cohort of 6 institutions operated less routinely, with 47% receiving surgery overall. At these 6 institutions, patients without multifocal infection only received surgery 26% of the time, which increased to 74% with multifocal infection and admission erythrocyte sedimentation rate >37.5 mm/h.

CONCLUSIONS

This study is the first to objectively identify significant differences in the rates of surgical management of pediatric AHO across the United States. Variation in the surgical management of AHO appears to be driven primarily based on institutional practice. Twelve institutions operated on 72% of patients, regardless of the severity of disease, indicating that the institution custom or dogma may drive the surgical indications. Six institutions relied more on clinical judgment with significant variability in rates of surgical intervention (26% vs. 74%), depending on the severity of the disease. Surgical intervention is associated with increased recurrence, readmission, and hospital length of stay. As a result of these findings, it is essential to prospectively study the appropriate surgical indications and measure the outcomes in children with pediatric AHO.

LEVEL OF EVIDENCE

Level III.

Determining the pharmacologic window of bisphosphonates that mitigates severe injury-induced osteoporosis and muscle calcification, while preserving fracture repair

Following severe injury, biomineralization is disrupted and limited therapeutic options exist to correct these pathologic changes. This study utilized a clinically relevant murine model of polytrauma including a severe injury with concomitant musculoskeletal injuries to identify when bisphosphonate administration can prevent the paradoxical decrease of biomineralization in bone and increased biomineralization in soft tissues, yet not interfere with musculoskeletal repair.

INTRODUCTION

Systemic and intrinsic mechanisms in bone and soft tissues help promote biomineralization to the skeleton, while preventing it in soft tissues. However, severe injury can disrupt this homeostatic biomineralization tropism, leading to adverse patient outcomes due to a paradoxical decrease of biomineralization in bone and increased biomineralization in soft tissues. There remains a need for therapeutics that restore the natural tropism of biomineralization in severely injured patients. Bisphosphonates can elicit potent effects on biomineralization, though with variable impact on musculoskeletal repair. Thus, a critical clinical question remains as to the optimal time to initiate bisphosphonate therapy in patients following a polytrauma, in which bone and muscle are injured in combination with a severe injury, such as a burn.

METHODS

To test the hypothesis that the dichotomous effects of bisphosphonates are dependent upon the time of administration relative to the ongoing biomineralization in reparative bone and soft tissues, this study utilized murine models of isolated injury or polytrauma with a severe injury, in conjunction with sensitive, longitudinal measure of musculoskeletal repair.

RESULTS

This study demonstrated that if administered at the time of injury, bisphosphonates prevented severe injury-induced bone loss and soft tissue calcification, but did not interfere with bone repair or remodeling. However, if administered between 7 and 21 days post-injury, bisphosphonates temporally and spatially localized to sites of active biomineralization, leading to impaired fracture callus remodeling and permanence of soft tissue calcification.

CONCLUSION

There is a specific pharmacologic window following polytrauma that bisphosphonates can prevent the consequences of dysregulated biomineralization, yet not impair musculoskeletal regeneration.

Bruise Location in Supracondylar Humerus Fractures Predicts Specific Neurovascular Injuries

PURPOSE

The presence of soft tissue injury in pediatric supracondylar humerus fractures (SCHFs) has been shown to be an independent predictor of any neurovascular injury. Potentially expanding this concept, the specific neurovascular structure injured around the elbow is thought to be dependent upon the direction and magnitude of fracture displacement and subsequent soft tissue injury. Therefore, it was hypothesized that the bruise location following SCHF is indicative of the anatomic location of maximal soft tissue injury and therefore is a specific prognosticator of which neurovascular structure may be injured.

METHODS

Retrospective chart review of all SCHFs treated at a tertiary pediatric hospital from 2007 to 2017 collected information on bruise location, neurovascular injury patterns, and outcomes. Bruise location was classified as anterior, anterolateral, anteromedial, or posterior. Injury radiographs were reviewed by a blinded pediatric orthopaedic surgeon to neurovascular structure injured.

RESULTS

Of 2845 SCHFs identified, 267 (9.4%) had concomitant neurovascular injury-of which 128 (47.9%) met inclusion criteria. Among the vascular injuries, all bruising was anteromedial (28/45, 62.2%, P<0.05) or anterior (17/45, 37.8%, P>0.05). Fractures with anteromedial bruising correlated with median nerve injury (24/27, 88.9%, P<0.05), whereas fractures with anterolateral bruising correlated with radial nerve injuries (24/25, 96.0%, P<0.05). Bruising or radiographic evaluation correctly identified 60.2% and 64.1% of neurovascular injuries, respectively, whereas the combination identified 82.0% of neurovascular injuries correctly. Bruise location identified 23 neurovascular injuries not predicted by radiographic evaluation alone.

CONCLUSION

Bruise location is an important physical examination finding that can be used as an adjunct to improve the diagnostic accuracy of neurovascular injury in SCHFs in conjunction with neurovascular physical examination and radiographic evaluation. SCHFs with anterior or anteromedial bruising should raise concern for vascular injury. In addition, anteromedial bruising is predictive of a median nerve injury and anterolateral bruising is predictive of radial nerve injury. This adjunct diagnostic is particularly helpful in a noncooperative child or if performed by a clinician with limited experience in diagnosing neurovascular injuries or interpreting pediatric elbow radiographs.

LEVEL OF EVIDENCE

Level IV, case series.

Quantitative Analysis of Growth Factors From Cancellous Bone Graft Collected With a Reamer-Irrigator-Aspirator System From Native Long Bones Versus Previously Reamed Long Bones

OBJECTIVE

Collection of bone graft with the Reamer-Irrigator-Aspirator (RIA) system has become common practice across the field of orthopaedic surgery. While RIA bone graft is typically obtained from native long bones, grafting material can likewise be harvested from long bones that have previously undergone the placement and removal of an intramedullary nail, a process termed re-reamed RIA (RRR). The purpose of this study was to evaluate the total protein and growth factor concentrations present in native-RIA (NR) compared with RRR samples.

METHODS

NR and RRR bone grafts were collected intraoperatively with the RIA system and processed to evaluate both the aqueous and the hard tissue components. Total protein concentration and specific growth factors were analyzed using standard bicinchoninic acid and multiplex assays, respectively. Analyte levels were then normalized to the total amount of protein detected.

RESULTS

Total protein levels were comparable between NR and RRR samples for both the aqueous filtrate and the hard tissue samples. When normalized, while levels of bone morphogenic protein-2 and vascular endothelial growth factor were comparable in the hard tissue component, the aqueous filtrate from the RRR sample was found to have elevated levels of growth factors, with bone morphogenic protein-2 reaching statistical significance.

CONCLUSIONS

This study demonstrates that ample protein is found within both NR and RRR samples, with comparable or elevated levels of osteogenic growth factors found within RRR samples. Future, larger, prospective studies will be required to evaluate the osteogenic potential and clinical efficacy of NR and RRR cancellous bone grafts to validate their equivalency.

A Mini-Open Approach to Medial Pinning in Pediatric Supracondylar Humeral Fractures May Be Safer Than Previously Thought

BACKGROUND

Displaced pediatric supracondylar humeral fractures (SCHFs) are stabilized after reduction by smooth pins. Although some SCHFs are biomechanically stable after lateral-only entry pinning (lateral pinning), an additional medial entry pin (cross-pinning) confers superior stabilization in some SCHFs. There is a recognized risk of iatrogenic ulnar nerve injury with medial entry pinning. The best existing evidence has estimated an iatrogenic ulnar nerve injury rate of approximately 3.4% in cross-pinning. In similar studies, the rate of iatrogenic nerve injury (all nerves) in lateral pinning is estimated at 1.9%. This study aimed to use a large, single-center, single-technique (mini-open) retrospective case series to determine the rate of iatrogenic ulnar nerve injury in cross-pinning.

METHODS

Patients undergoing percutaneous cross-pinning via the mini-open technique for SCHFs from 2007 to 2017 were retrospectively reviewed. Injury characteristics, operative variables, fixation technique, and complications, such as iatrogenic nerve injury, were recorded. Patients who underwent operative treatment at another hospital, had no postoperative follow-up, or died due to polytrauma were excluded.

RESULTS

In this study, 698 patients undergoing cross-pinning during the study period were identified. Patients treated with cross-pinning had severe fractures, including a total of 198 preoperative neurovascular injuries (28.4%), 32 patients (4.6%) with skin tenting, and 19 patients (2.7%) with open fractures. Iatrogenic nerve injury was reported in 3 cases (0.43%), all of which affected the ulnar nerve. In 2 of 3 cases of iatrogenic nerve injury, the ulnar nerve symptoms resolved at a mean follow-up of 15 weeks.

CONCLUSIONS

The mini-open approach for medial pin insertion is safer than previous estimates. Here, in the largest single-center study of cross-pinning for SCHFs, the iatrogenic ulnar nerve injury rate of 0.43% was nearly 10 times lower than estimated rates from recent meta-analyses. Considering all nerves, the iatrogenic injury rate for this cross-pinning cohort was also lower than the estimated iatrogenic nerve injury rate for lateral pinning.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The Deleterious Effects of Impaired Fibrinolysis on Skeletal Development Are Dependent on Fibrin(ogen), but Independent of Interlukin-6

Chronic diseases in growing children, such as autoimmune disorders, obesity, and cancer, are hallmarked by musculoskeletal growth disturbances and osteoporosis. Many of the skeletal changes in these children are thought to be secondary to chronic inflammation. Recent studies have likewise suggested that changes in coagulation and fibrinolysis may contribute to musculoskeletal growth disturbances. In prior work, we demonstrated that mice deficient in plasminogen, the principal protease of degrading and clearing fibrin matrices, suffer from inflammation-driven systemic osteoporosis and that elimination of fibrinogen resulted in normalization of IL-6 levels and complete rescue of the skeletal phenotype. Given the intimate link between coagulation, fibrinolysis, and inflammation, here we determined if persistent fibrin deposition, elevated IL-6, or both contribute to early skeletal aging and physeal disruption in chronic inflammatory conditions. Skeletal growth as well as bone quality, physeal development, and vascularity were analyzed in C57BL6/J mice with plasminogen deficiency with and without deficiencies of either fibrinogen or IL-6. Elimination of fibrinogen, but not IL-6, rescued the skeletal phenotype and growth disturbances in this model of chronic disease. Furthermore, the skeletal phenotypes directly correlated with both systemic and local vascular changes in the skeletal environment. In conclusion, these results suggest that fibrinolysis through plasmin is essential for skeletal growth and maintenance, and is multifactorial by limiting inflammation and preserving vasculature.

Plasmin drives burn-induced systemic inflammatory response syndrome

Severe injuries, such as burns, provoke a systemic inflammatory response syndrome (SIRS) that imposes pathology on all organs. Simultaneously, severe injury also elicits activation of the fibrinolytic protease plasmin. While the principal adverse outcome of plasmin activation in severe injury is compromised hemostasis, plasmin also possesses proinflammatory properties. We hypothesized that, following a severe injury, early activation of plasmin drives SIRS. Plasmin activation was measured and related to injury severity, SIRS, coagulopathy, and outcomes prospectively in burn patients who are not at risk of hemorrhage. Patients exhibited early, significant activation of plasmin that correlated with burn severity, cytokines, coagulopathy, and death. Burn with a concomitant, remote muscle injury was employed in mice to determine the role of plasmin in the cytokine storm and inflammatory cascades in injured tissue distant from the burn injury. Genetic and pharmacologic inhibition of plasmin reduced the burn-induced cytokine storm and inflammatory signaling in injured tissue. These findings demonstrate (a) that severe injury-induced plasmin activation is a key pathologic component of the SIRS-driven cytokine storm and SIRS-activated inflammatory cascades in tissues distant from the inciting injury and (b) that targeted inhibition of plasmin activation may be effective for limiting both hemorrhage and tissue-damaging inflammation following injury.

Genetic heterogeneity of heritable ectopic mineralization disorders in a large international cohort

PURPOSE

Heritable ectopic mineralization disorders comprise a group of conditions with a broad range of clinical manifestations in nonskeletal connective tissues. We report the genetic findings from a large international cohort of 478 patients afflicted with ectopic mineralization.

METHODS

Sequence variations were identified using a next-generation sequencing panel consisting of 29 genes reported in association with ectopic mineralization. The pathogenicity of select splicing and missense variants was analyzed in experimental systems in vitro and in vivo.

RESULTS

A total of 872 variants of unknown significance as well as likely pathogenic and pathogenic variants were disclosed in 25 genes. A total of 159 distinct variants were identified in 425 patients in ABCC6, the gene responsible for pseudoxanthoma elasticum, a heritable multisystem ectopic mineralization disorder. The interpretation of variant pathogenicity relying on bioinformatic predictions did not provide a consensus. Our in vitro and in vivo functional assessment of 14 ABCC6 variants highlighted this dilemma and provided unambiguous interpretations to their pathogenicity.

CONCLUSION

The results expand the ABCC6 variant repertoire, shed new light on the genetic heterogeneity of heritable ectopic mineralization disorders, and provide evidence that functional characterization in appropriate experimental systems is necessary to determine the pathogenicity of genetic variants.

Factors That Drive Annual Variation in Pediatric Elbow Fracture Occurrence, Severity, and Resource Utilization

BACKGROUND

Elbow fractures are the most common pediatric fractures requiring operative treatment. To date, few studies have examined what annual factors drive pediatric elbow fracture incidence and no studies have examined which annual factors drive elbow fracture severity or resource utilization. The goal of this study was to not only document the annual patterns of pediatric elbow fracture incidence and severity but also the impact of these patterns on resource utilization in the emergency department, emergency medical service transportation, and the operating room (OR).

METHODS

Retrospective cohort study of 4414 pediatric elbow fractures from a single tertiary hospital (2007 to 2017). Exclusion criteria included outside treatment or lack of diagnosis by an orthopaedist. Presentation information, injury patterns, transport, and treatment requirements were collected. Pearson correlations were used to analyze factors influencing fracture incidence, severity, and resource utilization.

RESULTS

Pediatric elbow fracture incidence positively correlated with monthly daylight hours, but significantly fewer elbow fractures occurred during summer vacation from school compared with surrounding in school months. While fewer overall fractures occurred during summer break, the fractures sustained were greater in severity, conferring higher rates of displacement, higher risk of neurovascular injury, and greater needs for emergency transportation and operative treatment. Yearly, elbow fractures required 320.6 OR hours (7.7% of all pediatric orthopaedic OR time and 12.3% of all pediatric orthopaedic operative procedures), 203.4 hospital admissions, and a total of 4753.7 miles traveled by emergency medical service transportation to manage. All-cause emergency department visits were negatively correlated with daylight hours, inversing the pattern seen in elbow fractures.

CONCLUSION

Increased daylight, while school was in session, was a major driver of the incidence of pediatric elbow fractures. While summer vacation conferred fewer fractures, these were of higher severity. As such, increased daylight correlated strongly with monthly resource utilization, including the need for emergency transportation and operative treatment. This study provides objective data by which providers and administrators can more accurately allocate resources.

LEVEL OF EVIDENCE

Level III-Retrospective comparative study.

Effects of nanocrystalline hydroxyapatite concentration and skeletal site on bone and cartilage formation in rats

Most fractures heal by a combination of endochondral and intramembranous ossification dependent upon strain and vascularity at the fracture site. Many biomaterials-based bone regeneration strategies rely on the use of calcium phosphates such as nano-crystalline hydroxyapatite (nHA) to create bone-like scaffolds. In this study, nHA was dispersed in reactive polymers to form composite scaffolds that were evaluated both in vitro and in vivo. Matrix assays, immunofluorescent staining, and Western blots demonstrated that nHA influenced mineralization and subsequent osteogenesis in a dose-dependent manner in vitro. Furthermore, nHA dispersed in polymeric composites promoted osteogenesis by a similar mechanism as particulated nHA. Scaffolds were implanted into a 2-mm defect in the femoral diaphysis or metaphysis of Sprague-Dawley rats to evaluate new bone formation at 4 and 8 weeks. Two formulations were tested: a poly(thioketal urethane) scaffold without nHA (PTKUR) and a PTKUR scaffold augmented with 22 wt% nHA (22nHA). The scaffolds supported new bone formation in both anatomic sites. In the metaphysis, augmentation of scaffolds with nHA promoted an intramembranous healing response. Within the diaphysis, nHA inhibited endochondral ossification. Immunohistochemistry was performed on cryo-sections of the bone/scaffold interface in which CD146, CD31, Endomucin, CD68, and Myeloperoxidase were evaluated. No significant differences in the infiltrating cell populations were observed. These findings suggest that nHA dispersed in polymeric composites induces osteogenic differentiation of adherent endogenous cells, which has skeletal site-specific effects on fracture healing. STATEMENT OF SIGNIFICANCE: Understanding the mechanism by which synthetic scaffolds promote new bone formation in preclinical models is crucial for bone regeneration applications in the clinic where complex fracture cases are seen. In this study, we found that dispersion of nHA in polymeric scaffolds promoted in vitro osteogenesis in a dose-dependent manner through activation of the PiT1 receptor and subsequent downstream Erk1/2 signaling. While augmentation of polymeric scaffolds with nHA enhanced intramembranous ossification in metaphyseal defects, it inhibited endochondral ossification in diaphyseal defects. Thus, our findings provide new insights into designing synthetic bone grafts that complement the skeletal site-specific fracture healing response.

Internal Rotation Stress Test Reduces Cross-Pinning and Improves Outcomes in Displaced Pediatric Supracondylar Humeral Fractures

Stabilization of the medial column is vital in preventing the loss of fixation and malunion in displaced pediatric supracondylar humeral fractures (SCHFs). The preferred percutaneous pin configuration for medial column fixation remains controversial between medial pinning (cross-pinning) and additional lateral-based pinning. The intraoperative internal rotation stress test (IRST) has been proposed to reliably determine the optimal fixation strategy for each unique fracture. This study evaluated the impact of implementing the IRST on both the choice of pin configuration and institution-wide complications in pediatric patients treated operatively for SCHFs.

Methods

Pediatric patients undergoing percutaneous pinning for SCHFs between 2007 and 2017 at a single center were retrospectively reviewed. The IRST was made a universal institutional practice in 2013. Patients were divided into 2 groups for analysis: (1) patients who underwent treatment before the IRST was implemented in 2013 (the pre-IRST group), and (2) patients who were treated after the IRST was implemented in 2013 (the IRST group). Subgroup analysis was completed for patients in the IRST group who were treated with cross-pinning or 3 lateral-based pins.

Results

In this study, 820 patients in the pre-IRST group and 636 patients in the IRST group were included. After the IRST implementation, the rate of loss of fixation fell from 1.2% to 0% (p = 0.003), and the reoperation rate fell from 3.3% to 0.2% (p < 0.001). No cases resulted in a loss of fixation after the adoption of the IRST. The number of patients treated with cross-pinning decreased significantly from 53.2% to 31.6% (p < 0.001) after the IRST implementation, yet cross-pinning continued to be used for more severe fractures. Complication rates within the IRST group were not significantly different (p > 0.05) between cross-pinning and 3 lateral-based pins.

Conclusions

In the largest cohort reported on to date, to our knowledge, institutional implementation of the IRST resulted in a significant reduction in the use of cross-pinning. Although the usage of cross-pinning decreased, cross-pinning was still used frequently in the most severe fractures. The IRST use also resulted in significantly fewer complications such as loss of fixation after institution-wide implementation of the IRST for treating pediatric SCHFs.

Level of Evidence

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Intramedullary Ulnar Fixation for the Treatment of Monteggia Fracture

Background

Although many pediatric Monteggia fractures can be treated nonoperatively, the presence of any residual radiocapitellar subluxation following ulnar reduction mandates a more aggressive approach to restore and maintain ulnar length. In younger children, restoration and maintenance of ulna length may be achieved through intramedullary fixation of the ulnar shaft.

Description

A Steinmann pin or flexible intramedullary nail is introduced percutaneously through the olecranon apophysis and advanced within the medullary canal to the ulnar fracture site. If necessary, the ulnar length and alignment are then restored by either a closed reduction or open reduction. The pin or nail is advanced across the fracture site into the distal fracture fragment and then advanced to a point just proximal to the distal ulnar physis. Once restoration of normal radiocapitellar alignment is verified fluoroscopically, the pin is bent and cut outside of the skin and a cast or splint is applied.

Alternatives

Closed reduction and cast immobilization is a well-accepted form of treatment for a Monteggia fracture. If ulnar length and alignment along with an anatomic reduction of the radiocapitellar joint can be achieved in this fashion, surgery can be avoided, but close radiographic follow-up is recommended to assess for loss of alignment with subsequent radial-head subluxation. Open reduction and internal fixation with use of a plate-and-screw construct can achieve similar results to intramedullary fixation and should be considered for length-unstable fractures and those in which an appropriately sized intramedullary implant fails to maintain adequate ulnar alignment. If plastic deformation of the ulna is present with residual radiocapitellar subluxation following reduction of the ulnar diaphysis, consideration should be given to elongating the ulna through the fracture site with use of plate fixation in order to allow reduction of the radial head.

Rationale

Intramedullary fixation provides several benefits over open reduction and plate fixation for these injuries. In general, treatment can be rendered with a shorter anesthetic time, less scarring, and without the concern for symptomatic retained hardware associated with plating along the subcutaneous boarder of the ulna shaft.

Expected Outcomes

Compared with nonoperative treatment, intramedullary fixation of length-stable Monteggia fractures has lower rates of recurrent radial-head subluxation and loss of ulnar alignment requiring subsequent operative treatment¹. If healing is achieved without residual radiocapitellar instability, good elbow function can be expected.

Important Tips

The entry point for the intramedullary implant should be slightly radial to the tip of the olecranon apophysis to compensate for the anatomic varus bow of the proximal aspect of the ulna.Intramedullary fixation is ideal for length-stable ulnar fractures. If a comminuted or long oblique fracture is present, an intramedullary device may not maintain ulnar length, leading to residual or recurrent radiocapitellar instability. For length-unstable fractures, therefore, a plate-and-screw construct should be considered.No more than 3 attempts should be made to pass the intramedullary implant into the distal ulnar segment by closed means in order to limit the risk of iatrogenic compartment syndrome.If anatomic alignment of the radiocapitellar joint is not achieved following an apparent anatomic reduction of the ulna, assess for plastic deformation of the ulna and consider open elongation of the ulna through the fracture site with use of plate fixation.Following fixation and radial-head reduction, immobilize the forearm in the position of maximal radiocapitellar stability (typically in supination).

Albumin and the fibrinogen-to-albumin ratio: Biomarkers for the acute phase response following total knee arthroplasty

PURPOSE

Complications following total knee arthroplasty (TKA) lead to patient morbidity and cost. While acute phase reactants, such as c-reactive protein (CRP) and fibrinogen, have been used to predict complications following TKA, the extent and duration of changes in albumin levels following TKA are unknown. It is hypothesized that like CRP and fibrinogen, albumin, and the fibrinogen/albumin ratio (FAR) represent useful measures of the acute phase response (APR) following TKA. The purpose of this study was to describe the longitudinal course of albumin and FAR in healthy patients following TKA, relative to established biomarkers, and examine if the variance in albumin or FAR correlates with patient comorbidities.

METHODS

This retrospective cohort study of patients undergoing TKA at a tertiary medical center. CRP, fibrinogen, and albumin values were collected pre- and post-operatively. An age-adjusted Charlson comorbidity index (CCI) was utilized as a measure of patient comorbidity status.

RESULTS

The median preoperative albumin value was 4.3 g/dL, which dropped to 3.6 g/dL on postoperative day 1 following TKA. The albumin value returned to 93% of the baseline by postoperative week 2. The course of albumin inversely mirrored the course of CRP (r = -0.41). Median preoperative FAR was 0.087 g/L, which rose to 0.130 g/L by postoperative week 2 and returned to baseline by postoperative week 6. While preoperative FAR strongly correlated with postoperative week 2 values (r = 0.74), there was a weak positive correlation between age-adjusted CCI and pre-operative FAR (r = 0.24) in patients undergoing primary TKA.

CONCLUSION

Albumin levels follow a predictable postoperative decline that inversely correlates with CRP in healthy patients following TKA. Given the low cost and abundance of laboratories offering albumin levels, direct albumin levels and/or albumin ratios such as FAR may be underutilized biomarkers for monitoring the APR following TKA.

Severe injury-induced osteoporosis and skeletal muscle mineralization: Are these related complications?

Severely injured patients are beleaguered by complications during convalescence, such as dysregulated biomineralization. Paradoxically, severely injured patients experience the loss of bone (osteoporosis), resulting in diminished skeletal integrity and increased risk of fragility fractures; yet they also accrue mineralization in soft tissues, resulting in complications such as heterotopic ossification (HO). The pathophysiology leading to dysregulated biomineralization in severely injured patients is not well defined. It has been postulated that these pathologies are linked, such that mineralization is "transferred" from the bone to soft tissue compartments. The goal of this study was to determine if severe injury-induced osteoporosis and soft tissue calcification are temporally coincident following injury. Using a murine model of combined burn and skeletal muscle injury to model severe injury, it was determined that mice developed significant progressive bone loss, detectable as early as 3 days post injury, and marked soft tissue mineralization by 7 days after injury. The observed temporal concordance between the development of severe injury-induced osteoporosis and soft tissue mineralization indicates the plausibility that these complications share a common pathophysiology, though further experiments are required.

Sterility of Miniature C-arm Fluoroscopy in Hand and Upper Extremity Surgery

Previous studies have demonstrated that sterile equipment is frequently contaminated intraoperatively, yet the incidence of miniature c-arm (MCA) contamination in hand and upper extremity surgery is unclear. To examine this incidence, a prospective study of MCA sterility in hand and upper extremity cases was performed in a hospital main operating room (MOR) (n = 13) or an ambulatory surgery center operating room (AOR) (n = 16) at a single tertiary care center. Case length, MCA usage parameters, and sterility of the MCA through the case were examined. We found that MOR surgical times trended toward significance (p = 0.055) and that MOR MCAs had significantly more contamination prior to draping than AOR MCAs (p < 0.001). In MORs and AORs, 46.2 and 37.5% of MCAs respectively were contaminated intraoperatively. In MORs and AORs, 85.7 and 80% of noncontaminated cases, respectively, used the above hand-table technique, while 50 and 83.3% of contaminated MOR and AOR cases, respectively, used a below hand-table technique. Similar CPT codes were noted in both settings. Thus, a high-rate of MCA intraoperative contamination occurs in both settings. MCA placement below the hand-table may impact intraoperative contamination, even to distant MCA areas. Regular sterilization of equipment and awareness of these possible risk factors could lower bacterial burden.

Plasminogen activation in the musculoskeletal acute phase response: Injury, repair, and disease

The musculoskeletal system is critical for movement and the protection of organs. In addition to abrupt injuries, daily physical demands inflict minor injuries, necessitating a coordinated process of repair referred to as the acute-phase response (APR). Dysfunctional APRs caused by severe injuries or underlying chronic diseases are implicated in pathologic musculoskeletal repair, resulting in decreased mobility and chronic pain. The molecular mechanisms behind these phenomena are not well understood, hindering the development of clinical solutions. Recent studies indicate that, in addition to regulating intravascular clotting, the coagulation and fibrinolytic systems are also entrenched in tissue repair. Although plasmin and fibrin are considered antithetical to one another in the context of hemostasis, in a proper APR, they complement one another within a coordinated spatiotemporal framework. Once a wound is contained by fibrin, activation of plasmin promotes the removal of fibrin and stimulates angiogenesis, tissue remodeling, and tissue regeneration. Insufficient fibrin deposition or excessive plasmin-mediated fibrinolysis in early convalescence prevents injury containment, causing bleeding. Alternatively, excess fibrin deposition and/or inefficient plasmin activity later in convalescence impairs musculoskeletal repair, resulting in tissue fibrosis and osteoporosis, while inappropriate fibrin or plasmin activity in a synovial joint can cause arthritis. Together, these pathologic conditions lead to chronic pain, poor mobility, and diminished quality of life. In this review, we discuss both fibrin-dependent and -independent roles of plasminogen activation in the musculoskeletal APR, how dysregulation of these mechanisms promote musculoskeletal degeneration, and the possibility of therapeutically manipulating plasmin or fibrin to treat musculoskeletal disease.

Nanocrystalline hydroxyapatite-poly(thioketal urethane) nanocomposites stimulate a combined intramembranous and endochondral ossification response in rabbits

Resorbable bone cements are replaced by bone osteoclastic resorption and osteoblastic new bone formation near the periphery. However, the ideal bone cement would be replaced by new bone through processes similar to fracture repair, which occurs through a variable combination of endochondral and intramembranous ossification. In this study, nanocrystalline hydroxyapatite (nHA)-poly(thioketal urethane) (PTKUR) cements were implanted in femoral defects in New Zealand White rabbits to evaluate ossification at 4, 12, and 18 months. Four formulations were tested: an injectable, flowable cement and three moldable putties with varying ratios of calcium phosphate to sucrose granules. New bone formation and resorption of the cement by osteoclasts occurred near the periphery. Stevenel's Blue and Safranin O staining revealed infiltration of chondrocytes into the cements and ossification of the cartilaginous intermediate. These findings suggest that nHA-PTKUR cements support combined intramembranous and endochondral ossification, resulting in enhanced osseointegration of the cement that could potentially improve patient outcomes.

Trauma-Induced Nanohydroxyapatite Deposition in Skeletal Muscle is Sufficient to Drive Heterotopic Ossification

Heterotopic ossification (HO), or the pathologic formation of bone within soft tissues, is a significant complication following severe injuries as it impairs joint motion and function leading to loss of the ability to perform activities of daily living and pain. While soft tissue injury is a prerequisite of developing HO, the exact molecular pathology leading to trauma-induced HO remains unknown. Through prior investigations aimed at identifying the causative factors of HO, it has been suggested that additional predisposing factors that favor ossification within the injured soft tissues environment are required. Considering that chondrocytes and osteoblasts initiate physiologic bone formation by depositing nanohydroxyapatite crystal into their extracellular environment, we investigated the hypothesis that deposition of nanohydroxyapatite within damaged skeletal muscle is likewise sufficient to predispose skeletal muscle to HO. Using a murine model genetically predisposed to nanohydroxyapatite deposition (ABCC6-deficient mice), we observed that following a focal muscle injury, nanohydroxyapatite was robustly deposited in a gene-dependent manner, yet resolved via macrophage-mediated regression over 28 days post injury. However, if macrophage-mediated regression was inhibited, we observed persistent nanohydroxyapatite that was sufficient to drive the formation of HO in 4/5 mice examined. Together, these results revealed a new paradigm by suggesting the persistent nanohydroxyapatite, referred to clinically as dystrophic calcification, and HO may be stages of a pathologic continuum, and not discrete events. As such, if confirmed clinically, these findings support the use of early therapeutic interventions aimed at preventing nanohydroxyapatite as a strategy to evade HO formation.

A Clinical Prediction Algorithm to Stratify Pediatric Musculoskeletal Infection by Severity

OBJECTIVE

There are currently no algorithms for early stratification of pediatric musculoskeletal infection (MSKI) severity that are applicable to all types of tissue involvement. In this study, the authors sought to develop a clinical prediction algorithm that accurately stratifies infection severity based on clinical and laboratory data at presentation to the emergency department.

METHODS

An IRB-approved retrospective review was conducted to identify patients aged 0 to 18 who presented to the pediatric emergency department at a tertiary care children's hospital with concern for acute MSKI over a 5-year period (2008 to 2013). Qualifying records were reviewed to obtain clinical and laboratory data and to classify in-hospital outcomes using a 3-tiered severity stratification system. Ordinal regression was used to estimate risk for each outcome. Candidate predictors included age, temperature, respiratory rate, heart rate, C-reactive protein (CRP), and peripheral white blood cell count. We fit fully specified (all predictors) and reduced models (retaining predictors with a P-value ≤0.2). Discriminatory power of the models was assessed using the concordance (c)-index.

RESULTS

Of the 273 identified children, 191 (70%) met inclusion criteria. Median age was 5.8 years. Outcomes included 47 (25%) children with inflammation only, 41 (21%) with local infection, and 103 (54%) with disseminated infection. Both the full and reduced models accurately demonstrated excellent performance (full model c-index 0.83; 95% confidence interval, 0.79-0.88; reduced model 0.83; 95% confidence interval, 0.78-0.87). Model fit was also similar, indicating preference for the reduced model. Variables in this model included CRP, pulse, temperature, and an interaction term for pulse and temperature. The odds of a more severe outcome increased by 30% for every 10 U increase in CRP.

CONCLUSIONS

Clinical and laboratory data obtained in the emergency department may be used to accurately differentiate pediatric MSKI severity. The predictive algorithm in this study stratifies pediatric MSKI severity at presentation irrespective of tissue involvement and anatomic diagnosis. Prospective studies are needed to validate model performance and clinical utility.

LEVEL OF EVIDENCE

Level II-prognostic study.

The multifaceted role of fibrinogen in tissue injury and inflammation

The canonical role of the hemostatic and fibrinolytic systems is to maintain vascular integrity. Perturbations in either system can prompt primary pathological end points of hemorrhage or thrombosis with vessel occlusion. However, fibrin(ogen) and proteases controlling its deposition and clearance, including (pro)thrombin and plasmin(ogen), have powerful roles in driving acute and reparative inflammatory pathways that affect the spectrum of tissue injury, remodeling, and repair. Indeed, fibrin(ogen) deposits are a near-universal feature of tissue injury, regardless of the nature of the inciting event, including injuries driven by mechanical insult, infection, or immunological derangements. Fibrin can modify multiple aspects of inflammatory cell function by engaging leukocytes through a variety of cellular receptors and mechanisms. Studies on the role of coagulation system activation and fibrin(ogen) deposition in models of inflammatory disease and tissue injury have revealed points of commonality, as well as context-dependent contributions of coagulation and fibrinolytic factors. However, there remains a critical need to define the precise temporal and spatial mechanisms by which fibrinogen-directed inflammatory events may dictate the severity of tissue injury and coordinate the remodeling and repair events essential to restore normal organ function. Current research trends suggest that future studies will give way to the identification of novel hemostatic factor-targeted therapies for a range of tissue injuries and disease.

Are We Spending Wisely? Impact of POSNA Grants on Scholarly Productivity and Future Funding Success

BACKGROUND

The Pediatric Orthopaedic Society of North America (POSNA) funds grants to improve pediatric musculoskeletal care and maximize new knowledge through publications, presentations, and further funding. We assessed the productivity of POSNA grants by number and rate of grant-specific publications, citations, and extramural funding; determined whether project type or completion status was associated with extramural funding; and compared the success of POSNA-funded versus all other podium presentations by publication rate and POSNA awards.

METHODS

We reviewed final reports for all 85 POSNA grants from 2003 to 2014. To determine grant productivity, we assessed the publication, presentation, and extramural funding rates, and the percentage of grants that achieved at least 1 scholarly output (publication or presentation). Citation counts were determined within 3 years after publication.

RESULTS

Overall, each grant achieved ~1.53 publications and 15.4 citations. Thirty-three percent secured extramural funding. However, 25% of grants could not be tracked to a scholarly product. Projects that reached completion and were of the basic science type (compared with clinical) were more likely to receive extramural funding. Compared with all other podiums, a greater proportion of POSNA-funded presentations led to a publication (64% vs. 48%, respectively; P=0.02) and were more likely to receive a POSNA award. Approximately 52% of funded projects were not presented at POSNA meetings.

CONCLUSIONS

Although most POSNA-funded projects led to scholarly output, 25% of them produced no publications or podium presentations. POSNA-funded projects were more likely to lead to a publication and to have a higher chance of winning a POSNA award compared with all other projects. The POSNA grant process is effective at identifying impactful research, but continued process improvement, such as a prospectively maintained database of grant recipient productivity and improved tracking of grant submission histories, are both in development as the first steps to improve accountability of grant recipients in translating their projects to scholarly products.

Developmental Dysplasia of the Hip From Birth to Arthroplasty: Clear Indications and New Controversies

Developmental dysplasia of the hip is the all-encompassing term used to describe the wide spectrum of disorders of the development of the hip that manifest in various forms and at different ages. Developmental dysplasia of the hip often evolves over time because the structures of the hip are normal during embryogenesis but gradually become abnormal. Such variability in pathology is associated with a similarly wide range in management options and recommendations aimed at preventing hip joint arthrosis. These options may be instituted at any time between birth and adulthood as techniques aimed at preserving the native hip or replacing the arthritic hip. Many of these management options are clearly indicated and considered standard practice. However, with the evolution of the understanding of hip biomechanics, better knowledge of the long-term outcomes of hip joint-preserving surgeries, and ever-improving technology influencing hip arthroplasty come new controversies, especially whether to preserve or replace the mature hip.

C-Reactive Protein Predicts Risk of Venous Thromboembolism in Pediatric Musculoskeletal Infection

BACKGROUND

The rate of venous thromboembolism in children with musculoskeletal infections (MSKIs) is markedly elevated compared with hospitalized children in general. Predictive biomarkers to identify high-risk patients are needed to prevent the significant morbidity and rare mortality associated with thrombotic complications. We hypothesize that overactivation of the acute phase response is associated with the development of pathologic thrombi and we aim to determine whether elevations in C-reactive protein (CRP) are associated with increased rates of thrombosis in pediatric patients with MSKI.

METHODS

A retrospective cohort study measuring CRP in pediatric MSKI patients with or without thrombotic complications.

RESULTS

The magnitude and duration of elevation in CRP values correlated with the severity of infection and the development of pathologic thrombosis. In multivariable logistic regression, every 20 mg/L increase in peak CRP was associated with a 29% increased risk of thrombosis (P<0.001). Peak and total CRP were strong predictors of thrombosis with area under the receiver-operator curves of 0.90 and 0.92, respectively.

CONCLUSIONS

Future prospective studies are warranted to further define the discriminatory power of CRP in predicting infection-provoked thrombosis. Pharmacologic prophylaxis and increased surveillance should be strongly considered in patients with MSKI, particularly those with disseminated disease and marked elevation of CRP.

LEVEL OF EVIDENCE

Level III.

Do Corticosteroids Attenuate the Peri-Operative Acute Phase Response After Total Knee Arthroplasty?

BACKGROUND

Following tissue injury, the acute phase response (APR) functions to survive and then repair injured tissue. An exuberant APR, which can be evoked by total knee arthroplasty (TKA), results in a hyper-inflammatory state, leading to pain, nausea, venous thromboembolism, or potentially life-threatening complications. Here, we observed the effects of peri-operative dexamethasone on the APR following TKA by trending C-reactive protein (CRP, mg/L) and fibrinogen (mg/dL). We hypothesize that the anti-inflammatory effects of dexamethasone can attenuate the APR after TKA and will be associated with decreased post-operative pain and nausea.

METHODS

A retrospective case-control study was performed on 188 unilateral TKA procedures. The patients were divided into a group receiving dexamethasone (10 mg intra-operatively and on post-operative day [POD] 1) and a group receiving no corticosteroids. Post-operative CRP, fibrinogen, morphine equivalents, and anti-emetic doses were recorded.

RESULTS

Compared to the non-steroid group, patients receiving dexamethasone yielded a significantly decreased CRP on POD0 (5.5 vs 8.3), POD1 (11.8 vs 22.0), and POD2 (85.5 vs 148.9). A significant decrease in fibrinogen in patients receiving dexamethasone was seen on POD2 (460.0 vs 530.2). There was an increase in fibrinogen within the dexamethasone cohort at the 2-week visit (535.4 vs 488.9). Post-operative morphine equivalents administered were significantly decreased in patients receiving dexamethasone, but no difference in anti-emetic use was appreciated.

CONCLUSION

These data support the hypothesis that the APR following TKA can be attenuated pharmacologically by corticosteroids. Further studies are needed to determine whether the attenuation of the APR with the use of corticosteroids prevents complications following TKA.

Bone Fracture Acute Phase Response-A Unifying Theory of Fracture Repair: Clinical and Scientific Implications

Bone fractures create five problems that must be resolved: bleeding, risk of infection, hypoxia, disproportionate strain, and inability to bear weight. There have been enormous advancements in our understanding of the molecular mechanisms that resolve these problems after fractures, and in best clinical practices of repairing fractures. We put forth a modern, comprehensive model of fracture repair that synthesizes the literature on the biology and biomechanics of fracture repair to address the primary problems of fractures. This updated model is a framework for both fracture management and future studies aimed at understanding and treating this complex process. This model is based upon the fracture acute phase response (APR), which encompasses the molecular mechanisms that respond to injury. The APR is divided into sequential stages of "survival" and "repair." Early in convalescence, during "survival," bleeding and infection are resolved by collaborative efforts of the hemostatic and inflammatory pathways. Later, in "repair," avascular and biomechanically insufficient bone is replaced by a variable combination of intramembranous and endochondral ossification. Progression to repair cannot occur until survival has been ensured. A disproportionate APR-either insufficient or exuberant-leads to complications of survival (hemorrhage, thrombosis, systemic inflammatory response syndrome, infection, death) and/or repair (delayed- or non-union). The type of ossification utilized for fracture repair is dependent on the relative amounts of strain and vascularity in the fracture microenvironment, but any failure along this process can disrupt or delay fracture healing and result in a similar non-union. Therefore, incomplete understanding of the principles herein can result in mismanagement of fracture care or application of hardware that interferes with fracture repair. This unifying model of fracture repair not only informs clinicians how their interventions fit within the framework of normal biological healing but also instructs investigators about the critical variables and outputs to assess during a study of fracture repair.

Platelet-Derived TGF-β Induces Tissue Factor Expression via the Smad3 Pathway in Osteosarcoma Cells

Over the last three decades, the prognosis of osteosarcoma has remained unchanged; the prognosis for patients with lung metastasis is still poor, and the development of new treatments is urgently required. We previously showed that aggressive osteosarcoma cells express more tissue factor (TF) and demonstrate enhanced extrinsic pathway capacity. Furthermore, tumor growth can be suppressed with the anticoagulant low molecular weight heparin. However, the molecular mechanisms underlying TF regulation are still unclear. Here, we report that transforming growth factor-β (TGF-β) upregulates TF, which can occur via activated platelets. TF was found to be expressed on osteosarcoma cell surfaces, which mediated the production of Xa and thrombin. TF induction by TGF-β was observed in several osteosarcoma cells, and especially in MG 63 cells. Both TF expression by TGF-β and extrinsic pathway activity through TF were rapidly increased. This reaction was inhibited by a TGF-β type I receptor inhibitor and TGF-β neutralizing antibody. Although TGF-β was found to phosphorylate both Smad2 and Smad3, their roles were markedly disparate. Surprisingly, Smad2 knockdown resulted in no inhibitory effect, whereas Smad3 knockdown completely suppressed TGF-β-induced TF expression. Next, data suggested that platelets were the source of TGF-β. We confirmed that thrombin-activated platelets and osteosarcoma cells could release TGF-β, and that platelet-derived TGF-β could induce TF expression. These processes were also inhibited by a TGF-β type I receptor inhibitor and Smad3 knockdown. Moreover, CD42b, TF, TGF-β, Smad2/3, and p-Smad2/3 were also detected in a biopsy sample from an osteosarcoma patient. Collectively, these finding suggested that the interaction between osteosarcoma cells and platelets, via thrombin and TGF-β, results in a continuous cycle, and that anti-platelet or anti-TGF-β therapy could be a promising tool for disease treatment. © 2018 American Society for Bone and Mineral Research.

Dilutional coagulopathy in pediatric scoliosis surgery: A single center report

BACKGROUND

Children undergoing posterior spinal fusion experience high blood loss often necessitating transfusion. An appropriately activated coagulation system provides hemostasis during surgery, but pathologic dysregulation can cause progressive bleeding and increased transfusions. Despite receiving antifibrinolytics for clot stabilization, many patients still require transfusions.

AIMS

We sought to examine the association of dilutional coagulopathy with blood loss and blood transfusion in posterior spinal fusion for pediatric scoliosis patients.

METHODS

A retrospective, single institution study of children undergoing posterior spinal fusion >6 levels with a standardized, prospective anesthetic protocol utilizing antifibrinolytics. Blood loss was evaluated using a hematocrit-based calculation. To evaluate transfusions, a normalized Blood Product Transfusion calculation was developed. Factors associated with blood loss and blood transfusions were determined by univariate analysis and multivariate regression modeling with multicollinearity and mediation analysis.

RESULTS

Patients received 73.7 mL/kg (standard deviation ±30.8) of fluid poor in coagulation factors. Estimated blood loss was 42.6 mL/kg (standard deviation ±18.0). There was a significant association between estimated blood loss and total fluids delivered (Spearman's rho = 0.51, 95% confidence interval 0.33-0.65, P < 0.001). Factors significantly associated with normalized Blood Product Transfusion in this cohort included age, weight, scoliosis type, levels fused, total osteotomies, pelvic fixation, total fluid, maximum prothrombin time, and minimum fibrinogen. Regression modeling showed the best combination of variables for modeling normalized Blood Product Transfusion included patient weight, number of levels fused, total fluid administered, and maximum prothrombin time.

CONCLUSION

Blood product transfusion remains a frustrating problem in pediatric scoliosis. Identifying and controlling dilutional coagulopathy in these patients may reduce blood loss and the need for blood transfusion.

Intra-articular Monteggia Fracture: A Case Study of Using the Center of Rotational Angulation to Improve a Functional Outcome

INTRODUCTION

Elbow fractures are the most common pediatric fracture to require operative fixation and can be associated with significant morbidities such as vascular injury, neurologic injury, and loss of function. Specifically, the chronic Monteggia fracture-dislocation causes devastating losses in range of motion. Presenting as a proximal to midshaft ulna fracture and radiocapitellar joint disruption, the acute injury can be successfully managed with closed reduction, serial casting, and close follow-up. The chronic complications of this injury, however, usually occur from an unrecognized radial head dislocation. Here, we present the first known case of a chronic Monteggia fracture-dislocation in the setting of an intra-articular ulnar fracture. Using the center of rotational angulation (CORA) from injury mechanism and radiographs, an intra-articular osteotomy was performed to correct ulnar length and improve this child's range of motion.

CASE REPORT

A 3-year-old Hispanic male was first seen in the emergency department for elbow pain following a fall from a sofa. He was incorrectly diagnosed with an isolated intra-articular ulna fracture. 5 weeks after the initially missed Monteggia fracture-dislocation, he presented to clinic with 90° flexion, 40° extension, and a 20° pronation/supination arc. An opening-wedge osteotomy was performed at the intra-articular CORA to restore ulnar length and allow for reduction of the radial head. The magnitude of the ulnar opening-wedge osteotomy was trialed until the radiocapitellar joint maintained reduction throughout pronosupination.

CONCLUSION

7 months after the surgery, the patient displayed functional improvements with 115° flexion, 15° extension, and a 75° pronation/supination arc. On physical examination, he had no neuropathic symptoms, with intact median, radial, and ulnar nerves. Using the CORA from the perceived injury mechanism and radiographs, an intra-articular osteotomy was performed to correct ulnar length, reduce the radial head, and thereby improve this child's range of motion.

Novel preclinical murine model of trauma-induced elbow stiffness

BACKGROUND

Peri-articular injury may result in functional deficits and pain. In particular, post-traumatic elbow stiffness is a debilitating condition, precluding patients from performing activities of daily living. As such, clinicians and basic scientists alike, aim to develop novel therapeutic interventions to prevent and treat elbow stiffness; thereby reducing patient morbidity. Yet, there is a paucity of pre-clinical models of peri-articular stiffness, especially of the upper extremity, necessary to develop and test the efficacy of therapeutics. We set out to develop a pre-clinical murine model of elbow stiffness, resulting from soft tissue injury, with features characteristic of pathology observed in these patients.

METHODS

A soft tissue peri-elbow injury was inflicted in mice using cardiotoxin. Pathologic tissue repair was induced by creating an investigator-imposed deficiency of plasminogen, a protease essential for musculoskeletal tissue repair. Functional testing was conducted through analysis of grip strength and gait. Radiography, microcomputed tomography, and histological analyses were employed to quantify development of heterotopic ossification.

RESULTS

Animals with peri-elbow soft tissues injury in conjunction with an investigator-imposed plasminogen deficiency, developed a significant loss of elbow function measured by grip strength (2.387 ± 0.136 N vs 1.921 ± 0.157 N, ****, p < 0.0001) and gait analysis (35.05 ± 2.775 mm vs 29.87 ± 2.075 mm, ***, p < 0.0002). Additionally, plasminogen deficient animals developed capsule thickening, delayed skeletal muscle repair, fibrosis, chronic inflammation, and heterotopic ossification; all features characteristic of pathology observed in patients with trauma-induced elbow stiffness.

CONCLUSION

A soft tissue injury to the peri-elbow soft tissue with a concomitant deficiency in plasminogen, instigates elbow stiffness and pathologic features similar to those observed in humans. This pre-clinical model is valuable for translational studies designed to investigate the contributions of pathologic features to elbow stiffness or as a high-throughput model for testing therapeutic strategies designed to prevent and treat trauma-induced elbow stiffness.

Pediatric Musculoskeletal Infection: Hijacking the Acute-Phase Response

Tissue injury activates the acute-phase response mediated by the liver, which promotes coagulation, immunity, and tissue regeneration. To survive and disseminate, musculoskeletal pathogens express virulence factors that modulate and hijack this response. As the acute-phase reactants required by these pathogens are most abundant in damaged tissue, these infections are predisposed to occur in tissues following traumatic or surgical injury. Staphylococcus aureus expresses the virulence factors coagulase and von Willebrand binding protein to stimulate coagulation and to form a fibrin abscess that protects it from host immune-cell phagocytosis. After the staphylococcal abscess community reaches quorum, which is the colony density that enables cell-to-cell communication and coordinated gene expression, subsequent expression of staphylokinase stimulates activation of fibrinolysis, which ruptures the abscess wall and results in bacterial dissemination. Unlike Staphylococcus aureus, Streptococcus pyogenes expresses streptokinase and other virulence factors to activate fibrinolysis and to rapidly disseminate throughout the body, causing diseases such as necrotizing fasciitis. Understanding the virulence strategies of musculoskeletal pathogens will help to guide clinical diagnosis and decision-making through monitoring of acute-phase markers such as C-reactive protein, erythrocyte sedimentation rate, and fibrinogen.