Osteosarcoma After Total Knee Arthroplasty: A Case Report.

CASE: A 79-year-old woman presented with a periprosthetic fracture 8 years after a total knee arthroplasty (TKA). Radiographs demonstrated tibial implant loosening with severe osteolysis. A high-grade osteosarcoma around the prosthesis was diagnosed, and a supracondylar femoral amputation was performed. After 2 years, no complications have occurred. CONCLUSIONS: A malignant tumor around a TKA is extremely rare. Surgeons should remain vigilant with patients who present with rapidly progressive or very aggressive implant loosening with osteolysis. Owing to its complexity and potentially devastating prognosis, treatment should be guided by a specialist multidisciplinary team. Complex limb salvage procedures or amputation is usually required.

Molecular Simulation of SO2 Separation and Storage Using a Cryptophane-Based Porous Liquid.

A theoretical molecular simulation study of the encapsulation of gaseous SO2 at different temperature conditions in a type II porous liquid is presented here. The system is composed of cage cryptophane-111 molecules that are dispersed in dichloromethane, and it is described using an atomistic modelling of molecular dynamics. Gaseous SO2 tended to almost fully occupy cryptophane-111 cavities throughout the simulation. Calculations were performed at 300 K and 283 K, and some insights into the different adsorption found in each case were obtained. Simulations with different system sizes were also studied. An experimental-like approach was also employed by inserting a SO2 bubble in the simulation box. Finally, an evaluation of the radial distribution function of cryptophane-111 and gaseous SO2 was also performed. From the results obtained, the feasibility of a renewable separation and storage method for SO2 using porous liquids is mentioned.

Molecular Simulation of CO2 and H2 Encapsulation in a Nanoscale Porous Liquid.

In this study we analyse from a theoretical perspective the encapsulation of both gaseous H2 and CO2 at different conditions of pressure and temperature in a Type II porous liquid, composed by nanometric scale cryptophane-111 molecules dispersed in dichloromethane, using atomistic molecular dynamics. Gaseous H2 tends to occupy cryptophane-111's cavities in the early stages of the simulation; however, a remarkably greater selectivity of CO2 adsorption can be seen in the course of the simulation. Calculations were performed at ambient conditions first, and then varying temperature and pressure, obtaining some insight about the different adsorption found in each case. An evaluation of the host molecule cavities accessible volume was also performed, based on the guest that occupies the pore. Finally, a discussion between the different intermolecular host-guest interactions is presented, justifying the different selectivity obtained in the molecular simulation calculations. From the results obtained, the feasibility of a renewable separation and storage method for CO2 using these nanometric scale porous liquids is pointed out.

Thromboembolic Events After Traumatic Vertebral Fractures: An Analysis of 190,192 Patients.

STUDY DESIGN: Retrospective cohort study OBJECTIVE.: To determine the rate of venous thromboembolism event (VTE) and risk factors for their occurrence in patients with vertebral fractures. SUMMARY OF BACKGROUND DATA: Deep vein thrombosis or pulmonary embolism (VTE) events are a significant source of potentially preventable morbidity and mortality in trauma patients. In patients with traumatic vertebral fractures, a common high-energy injury sometimes resulting in spinal cord injury, there is debate about what factors may be associated with such VTEs. METHODS: All patients with vertebral fractures in the American College of Surgeons National Trauma Data Bank Research Data Set (NTDB RDS) from years 2011 and 2012 were identified. Multivariate logistic regression was used to determine factors associated with the occurrence of VTE while considering patient factors, injury characteristics, and hospital course. RESULTS: A total of 190,192 vertebral fractures patients were identified. The overall rate of VTE was 2.5%. In multivariate analysis, longer inpatient length of stay was most associated with increased VTEs with an odds ratio (OR) of up to 96.60 (95% CI: 77.67 - 129.13) for length of stay longer than 28 days (compared to 0 - 3 days). Additional risk factors in order of decreasing odds ratios were older age (OR of up to 1.65 [95% CI: 1.45 - 1.87] for patients age 70 - 79 years [compared to age 18 - 29 years]), complete spinal cord injuries (OR: 1.49 [95% CI: 1.31 - 1.68]), cancer (OR: 1.37 [95% CI: 1.25 - 1.50]), and obesity (OR: 1.32 [95% CI: 1.18 - 1.48]). Multiple associated non-spinal injuries were also associated with increased rates of VTE. CONCLUSION: While the overall rate of VTE is relatively low after vertebral fractures, longer LOS and other defined factors to lesser extents were predisposing factors. By determining patients at greatest risk, protocols to prevent such adverse outcomes can be developed and optimized. LEVEL OF EVIDENCE: 3.

Incidence of and Risk Factors for Knee Collateral Ligament Injuries With Proximal Tibia Fractures: A Study of 32,441 Patients.

Proximal tibia fractures are associated with concurrent collateral ligament injuries. Failure to recognize these injuries may lead to chronic knee instability. The purpose of this study was to identify risk factors for concurrent collateral ligament injuries with proximal tibia fractures and their association with inpatient outcomes. A total of 32,441 patients with proximal tibia fractures were identified in the 2011-2012 National Trauma Data Bank. A total of 1445 (4.5%) had collateral ligament injuries, 794 (2.4%) had injuries to both collateral ligaments, 456 (1.4%) had a medial collateral ligament injury only, and 195 (0.6%) had a lateral collateral ligament injury only. On multivariate analysis, risk factors found to be associated with collateral ligament injuries included distal femur fracture (odds ratio, 2.1), pedestrian struck by motor vehicle (odds ratio, 2.0), obesity (odds ratio, 1.6), young age (odds ratio, 1.9 for 18 to 29 years vs 40 to 49 years), motorcycle accident (odds ratio, 1.5), and Injury Severity Score of 20 or higher (odds ratio, 1.4). In addition, patients with simultaneous injuries to both collateral ligaments had higher odds of inpatient adverse events (odds ratio, 1.51) and longer hospital stay (mean, 2.27 days longer). The risk factors reported by this study can be used to identify patients with proximal tibia fractures who may warrant more careful and thorough evaluation and imaging of their knee collateral ligaments. [Orthopedics. 2018; 41(2):e268-e276.].

Incidence of and Risk Factors for Inpatient Stroke After Hip Fractures in the Elderly.

Although uncommon, stroke can be a catastrophic inpatient complication for patients with hip fractures. The current study determines the incidence of inpatient stroke after hip fractures in elderly patients, identifies risk factors associated with such strokes, and determines the association of stroke with short-term inpatient outcomes. A retrospective review of all patients aged 65 years or older with isolated hip fractures in the 2011 and 2012 National Trauma Data Bank was conducted. A total of 37,584 patients met inclusion criteria. Of these patients, 162 (0.4%) experienced a stroke during their hospitalization for the hip fracture. In multivariate analysis, a history of prior stroke (odds ratio [OR], 13.24), coronary artery disease (OR, 2.05), systolic blood pressure 180 mm Hg or higher (OR, 1.66), and bleeding disorders (OR, 1.65) were associated with inpatient stroke. Inpatient stroke was associated with increased mortality (OR, 7.17) and inpatient serious adverse events (OR, 6.52). These findings highlight the need for vigilant care of high-risk patients, such as those with a history of prior stoke, and for an understanding that patients who experience an inpatient stroke after a hip fracture are at significantly increased risk of mortality and inpatient serious adverse events. [Orthopedics. 2018; 41(1):e27-e32.].

Risk factors and pharmacologic prophylaxis for venous thromboembolism in elective spine surgery.

BACKGROUND CONTEXT: Venous thromboembolism (VTE) is a known complication after spine surgery, but prophylaxis guidelines are ambiguous for patients undergoing elective spine surgery. PURPOSE: The objective of this study was to characterize the incidence and risk factors for VTE and the association of pharmacologic prophylaxis with VTE and bleeding complications after elective spine surgery. STUDY DESIGN/SETTING: This is a retrospective cohort study of patients undergoing elective spine surgery in the National Surgical Quality Improvement Program (NSQIP) database and a retrospective cohort analysis at an academic medical center. PATIENT SAMPLE: This study included 109,609 patients in the NSQIP database from 2005 to 2014 and 2,855 patients at the authors' institution from January 2013 to March 2016 who underwent elective spine surgery. OUTCOME MEASURES: The incidence and risk factors for VTE were assessed in both cohorts based on the NSQIP criteria. The incidence of bleeding complications requiring reoperation was assessed based on operative reports in the institutional cohort. MATERIALS AND METHODS: Associations of patient and procedure factors with VTE were characterized in the NSQIP population. In the single-institution cohort, in addition to NSQIP variables, a chart review was completed to determine the use of VTE prophylaxis, the history of prior VTE, and the incidence of hematoma requiring reoperation. The association of patient and procedure variables, including pharmacologic prophylaxis and history of prior VTE, with VTE and hematoma requiring reoperation were determined with multivariate regression. RESULTS: Among 109,609 elective spine surgery patients in NSQIP, independent risk factors for VTE were greater age, male gender, increasing body mass index, dependent functional status, lumbar spine surgery, longer operative time, perioperative blood transfusion, longer length of stay, and other postoperative complications. There were 2,855 patients included in the institutional cohort. Pharmacologic prophylaxis was performed in 56.3% of the institutional patients, of whom 97.1% received unfractionated heparin. When controlling for patient and procedural variables, pharmacologic prophylaxis did not significantly influence the rate of VTE, but was associated with a significant increase in hematoma requiring a return to the operating room (relative risk=7.37, p=.048). CONCLUSIONS: Pharmacologic prophylaxis, primarily with unfractionated heparin, after elective spine surgery was not associated with a significant reduction in VTE. However, there was a significant increase in postoperative hematoma requiring reoperation among patients undergoing prophylaxis. This raises questions about the routine use of unfractionated heparin for VTE prophylaxis and supports the need for further consideration of risks and benefits of chemoprophylaxis after elective spine surgery.

Of 20,376 Lumbar Discectomies, 2.6% of Patients Readmitted Within 30 Days: Surgical Site Infection, Pain, and Thromboembolic Events Are the Most Common Reasons for Readmission.

STUDY DESIGN: A retrospective cohort study of prospectively collected data. OBJECTIVE: As an initial effort to address readmissions after lumbar discectomy, reasons for hospital readmission are identified and discussed. SUMMARY OF BACKGROUND DATA: Lumbar discectomy is a commonly performed procedure. The Affordable Care Act codifies penalties for hospital readmissions. New quality-based reimbursements tied to readmissions call for a better understanding of the causes of readmission after procedures such as lumbar discectomy. METHODS: Lumbar discectomies performed in 2012 to 2014 were identified in the American College of Surgeons National Surgical Quality Improvement Program database. Patient demographics, surgical variables, and reasons for readmissions within 30 days were recorded. Pearson chi square was used to compare rates of demographics and surgical variables between readmitted and nonreadmitted patients. Multivariate regression was used to identify risk factors for readmission. RESULTS: Of 20,376 lumbar discectomies, 533 patients (2.62%) were readmitted within 30 days of surgery. The most common reasons for readmission were surgical site infections (n = 130, 0.64% of all discectomies, 24.4% of all readmissions), followed by pain issues (n = 89, 0.44%, 16.7%), and thromboembolic events (43, 0.21%, 8.1%). Overall time to readmission was 13.0 ±â€Š8.0 days (mean ±â€Šstandard deviation). Factors most associated with readmission after lumbar discectomy were higher American Society of Anesthesiologists class (relative risk = 1.49, P < 0.001) and prolonged operative time (relative risk = 1.41, P = 0.002). CONCLUSION: Surgical site infection, postoperative pain, and thromboembolic events were the most common reasons for readmission after lumbar discectomy. These findings identify potential areas for quality improvement initiatives. LEVEL OF EVIDENCE: 3.

Demographics, Mechanisms of Injury, and Concurrent Injuries Associated With Calcaneus Fractures: A Study of 14 516 Patients in the American College of Surgeons National Trauma Data Bank.

BACKGROUND: This study uses the American College of Surgeons National Trauma Data Bank (NTDB) to update the field on the demographics, injury mechanisms, and concurrent injuries among a national sample of patients admitted to the hospital department with calcaneus fractures. METHODS: Patients with calcaneus fractures in the NTDB during 2011-2012 were identified and assessed. RESULTS: A total of 14 516 patients with calcaneus fractures were included. The most common comorbidity was hypertension (18%), and more than 90% of fractures occurred via traffic accident (49%) or fall (43%). A total of 11 137 patients had concurrent injuries. Associated lower extremity fractures had the highest incidence and occurred in 61% of patients (of which the most common were other foot and ankle fractures). Concurrent spine fractures occurred in 23% of patients (of which the most common were lumbar spine fractures). Concurrent nonorthopaedic injuries included head injuries in 18% of patients and thoracic organ injuries in 15% of patients. CONCLUSION: This national sample indicates that associated injuries occur in more than three quarters calcaneus fracture patients. The most common associated fractures are in close proximity to the calcaneus. Although the well-defined association of calcaneus fractures with lumbar spine fractures was identified, the data presented highlight additional strong associations of calcaneus fractures with other orthopaedic and nonorthopaedic injuries. LEVELS OF EVIDENCE: Prognostic, Level III: Retrospective review of a prospectively collected cohort.

Primary and Revision Posterior Lumbar Fusion Have Similar Short-Term Complication Rates.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To compare short-term morbidity for primary and revision posterior lumbar fusions. SUMMARY OF BACKGROUND DATA: Revision lumbar fusions are unfortunately relatively common. Previous studies have described an increased risk of postoperative complications after revision lumbar fusion; however, these studies have been limited by small sample sizes, poor data quality, and/or narrow outcome measures. There is a need to validate these findings using a high-quality, national cohort of patients to have an accurate assessment of the relative risk of revision posterior lumbar fusions compared with primary lumbar fusion. METHODS: The prospectively-collected American College of Surgeons National Surgical Quality Improvement Program database was used to identify patients that underwent undergoing primary and revision posterior lumbar fusion from 2005 to 2013. The occurrence of individual and aggregated postoperative complications within 30 days, along with rates of blood transfusion and readmission, were compared between primary and revision procedures using bivariate and multivariate Poisson regression with robust error variance to control for patient and operative characteristics. Operative time and postoperative length of stay were compared between groups using bivariate and multivariate linear regression. RESULTS: Of the 14,873 posterior lumbar fusion procedures that met inclusion criteria, 1287 (8.7%) were revision cases. There were no differences in the rates of 30-day postoperative complications or readmission between primary and revision posterior lumbar fusion using multivariate analysis to control for patient and operative characteristics. Similarly, no significant differences were found for operative time or postoperative length of stay. There was an increased rate of blood transfusion for revision surgery compared with primary surgery (relative risk 1.4, P < 0.001). CONCLUSION: This study suggests that revision posterior lumbar fusion does not carry significantly increased risk of complications or readmission compared with a primary posterior lumbar fusion. Patients undergoing revision surgery were more likely to receive a blood transfusion. This information suggests that general health risk stratification for revision procedures can be similar to that considered for primary cases. LEVEL OF EVIDENCE: 3.

Analysis of Delays to Surgery for Cervical Spinal Cord Injuries.

STUDY DESIGN: A retrospective study of surgically treated patients with cervical spinal cord injury (SCI) from the National Trauma Data Bank Research Data Set. OBJECTIVE: To determine how time to surgery differs between SCI subtypes, where delays before surgery occur, and what factors are associated with delays. SUMMARY OF BACKGROUND DATA: Studies have shown that patients with cervical SCI undergoing surgery within 24 hours after injury have superior neurological outcomes to patients undergoing later surgery, with most evidence coming from the incomplete SCI subpopulation. METHODS: Surgically treated patients with cervical SCI from 2011 and 2012 were identified in National Trauma Data Bank Research Data Set and divided into subpopulations of complete, central, and other incomplete SCIs. Relationships between surgical timing and patient and injury characteristics were analyzed using multivariate regression. RESULTS: A total of 2636 patients with cervical SCI were identified: 803 with complete SCI, 950 with incomplete SCI, and 883 with central SCI. The average time to surgery was 51.1 hours for patients with complete SCI, 55.3 hours for patients with incomplete SCI, and 83.1 hours for patients with central SCI. Only 44% of patients with SCI underwent surgery within the first 24 hours after injury, including only 49% of patients with incomplete SCI.The vast majority of time between injury and surgery was after admission, rather than in the emergency department or in the field. Upper cervical SCIs and greater Charlson Comorbidity Index were associated with later surgery in all 3 SCI subpopulations. CONCLUSION: The majority of patients with SCI do not undergo surgery within the first 24 hours after injury, and the majority of delays occur after inpatient admission. Factors associated with these delays highlight areas of focus for expediting care in these patient populations. LEVEL OF EVIDENCE: 4.

Delayed surgery after acute traumatic central cord syndrome is associated with reduced mortality.

STUDY DESIGN: A retrospective study of surgically treated patients with acute traumatic central cord syndrome (ATCCS) from the National Trauma Data Bank Research Data Set. OBJECTIVE: To determine the association of time to surgery, pre-existing comorbidities, and injury severity on mortality and adverse events in surgically treated patients with ATCCS. SUMMARY OF BACKGROUND DATA: Although earlier surgery has been shown to be beneficial for other spinal cord injuries, the literature is mixed regarding the appropriate timing of surgery after ATCCS. Traditionally, this older population has been treated with delayed surgery because medical optimization is often indicated preoperatively. METHODS: Surgically treated patients with ATCCS in the National Trauma Data Bank Research Data Set from 2011 and 2012 were identified. Time to surgery, Charlson Comorbidity Index, and injury severity scores were tested for association with mortality, serious adverse events, and minor adverse events using multivariate logistic regression. RESULTS: A total of 1060 patients with ATCCS met inclusion criteria. After controlling for pre-existing comorbidity and injury severity, delayed surgery was associated with a decreased odds of inpatient mortality (odds ratio = 0.81, P = 0.04), or a 19% decrease in odds of mortality with each 24-hour increase in time until surgery. The association of time to surgery with serious adverse events was not statistically significant (P = 0.09), whereas time to surgery was associated with increased odds of minor adverse events (odds ratio = 1.06, P < 0.001). CONCLUSION: Although the potential neurological effect of surgical timing for patients with ATCCS remains controversial, the decreased mortality with delayed surgery suggests that waiting to optimize general health and potentially allow for some spinal cord recovery in these patients may be advantageous. LEVEL OF EVIDENCE: 3.

Freiberg's infraction: diagnosis and treatment.

Freiberg's infraction is a condition of cartilage degeneration of the lesser metatarsal heads. Adolescent females are the "textbook" patients but both males and females may present with this condition later in life. The second and third metatarsals are the most commonly affected, while involvement of the fourth and fifth is rare. The incidence is higher in females than in males. The pathophysiology is unknown, but studies suggest a combination of vascular compromise, genetic predisposition, and altered biomechanics. Diagnosis is made clinically and imaging is used to confirm. Early in the process, radiographs are normal however bone scans may demonstrate a photopenic center with a hyperactive collar and magnetic resonance imaging can reveal hypointensity of the metatarsal head. As Freiberg's infraction progresses, radiographs show a flattened and fragmented metatarsal head. Nonoperative treatment is based on decreasing foot pressure and unloading the affected metatarsal. Spontaneous healing with remodeling may occur in early stages of the disease. Operative options are dorsal closing wedge osteotomies, osteochondral transplant, and resection arthroplasty. Currently, we do not understand this disease sufficiently to prevent its occurrence. Outcomes of nonoperative and operative management are good to excellent and most patients are able to return to previous activity.