Clearance of Staphylococcus aureus from In Vivo Models of Chronic Infection by Immunization Requires Both Planktonic and Biofilm Antigens.

Staphylococcus aureus is a causative agent of chronic biofilm-associated infections that are recalcitrant to resolution by the immune system or antibiotics. To combat these infections, an antistaphylococcal, biofilm-specific quadrivalent vaccine against an osteomyelitis model in rabbits has previously been developed and shown to be effective at eliminating biofilm-embedded bacterial populations. However, the addition of antibiotics was required to eradicate remaining planktonic populations. In this study, a planktonic upregulated antigen was combined with the quadrivalent vaccine to remove the need for antibiotic therapy. Immunization with this pentavalent vaccine followed by intraperitoneal challenge of BALB/c mice with S. aureus resulted in 16.7% and 91.7% mortality in pentavalent vaccine and control groups, respectively (P < 0.001). Complete bacterial elimination was found in 66.7% of the pentavalent cohort, while only 8.3% of the control animals cleared the infection (P < 0.05). Further protective efficacy was observed in immunized rabbits following intramedullary challenge with S. aureus, where 62.5% of the pentavalent cohort completely cleared the infection, versus none of the control animals (P < 0.05). Passive immunization of BALB/c mice with serum IgG against the vaccine antigens prior to intraperitoneal challenge with S. aureus prevented mortality in 100% of mice and eliminated bacteria in 33.3% of the challenged mice. These results demonstrate that targeting both the planktonic and biofilm stages with the pentavalent vaccine or the IgG elicited by immunization can effectively protect against S. aureus infection.

A patient-centered composite endpoint weighting technique for orthopaedic trauma research.

BACKGROUND: This study aimed to address the current limitations of the use of composite endpoints in orthopaedic trauma research by quantifying the relative importance of clinical outcomes common to orthopaedic trauma patients and use those values to develop a patient-centered composite endpoint weighting technique. METHODS: A Best-Worst Scaling choice experiment was administered to 396 adult surgically-treated fracture patients. Respondents were presented with ten choice sets, each consisting of three out of ten plausible clinical outcomes. Hierarchical Bayesian modeling was used to determine the utilities associated with the outcomes. RESULTS: Death was the outcome of greatest importance (mean utility = - 8.91), followed by above knee amputation (- 7.66), below knee amputation (- 6.97), severe pain (- 5.90), deep surgical site infection (SSI) (- 5.69), bone healing complications (- 5.20), and moderate pain (- 4.59). Mild pain (- 3.30) and superficial SSI (- 3.29), on the other hand, were the outcomes of least importance to respondents. CONCLUSION: This study revealed that patients' relative importance towards clinical outcomes followed a logical gradient, with distinct and quantifiable preferences for each possible component outcome. These findings were incorporated into a novel composite endpoint weighting technique.

Poor Agreement Between Next-Generation DNA Sequencing and Bacterial Cultures in Orthopaedic Trauma Procedures.

BACKGROUND: Next-generation DNA sequencing (NGS) detects bacteria-specific DNA corresponding to the 16S ribosomal RNA gene and can identify bacterial presence with greater accuracy than traditional culture methods. The clinical relevance of these findings is unknown. The purpose of the present study was to compare the results from bacterial culture and NGS in order to characterize the potential use of NGS in orthopaedic trauma patients. METHODS: A prospective cohort study was performed at a single academic, level-I trauma center. Three patient groups were enrolled: (1) patients undergoing surgical treatment of acute closed fractures (presumed to have no bacteria), (2) patients undergoing implant removal at the site of a healed fracture without infection, and (3) patients undergoing a first procedure for the treatment of a fracture nonunion who might or might not have subclinical infection. Surgical site tissue was sent for culture and NGS. The proportions of culture and NGS positivity were compared among the groups. The agreement between culture and NGS results was assessed with use of the Cohen kappa statistic. RESULTS: Bacterial cultures were positive in 9 of 111 surgical sites (110 patients), whereas NGS was positive in 27 of 111 surgical sites (110 patients). Significantly more cases were positive on NGS as compared with culture (24% vs. 8.1%; p = 0.001), primarily in the acute closed fracture group. No difference was found in terms of the percent positivity of NGS when comparing the acute closed fracture, implant removal, and nonunion groups. With respect to bacterial identification, culture and NGS agreed in 73% of cases (κ = 0.051; 95% confidence interval, -0.12 to 0.22) indicating only slight agreement compared with expected chance agreement of 50%. CONCLUSIONS: NGS identified bacterial presence more frequently than culture, but with only slight agreement between culture and NGS. It is possible that the increased frequency of bacterial detection with molecular methods is reflective of biofilm presence on metal or colonization with nonpathogenic bacteria, as culture methods have selection pressure posed by restrictive, artificial growth conditions and there are low metabolic activity and replication rates of bacteria in biofilms. Our data suggest that NGS should not currently substitute for or complement conventional culture in orthopaedic trauma cases with low suspicion of infection. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Intraoperative Tobramycin Powder Prevents Enterobacter cloacae Surgical Site Infections in a Rabbit Model of Internal Fixation.

OBJECTIVES: To evaluate the efficacy of intraoperative tobramycin powder in preventing surgical site infection (SSI) and implant colonization with Enterobacter cloacae in a rabbit fixation model. Gram-negative rods, particularly Enterobacter species, comprise an increasing percentage of SSI at our institution. METHODS: Eighteen New Zealand White rabbits underwent surgical fixation of the left tibia with implantation of a plate and screws. The surgical site and implant were inoculated with 1 × 107 CFUs E. cloacae. The selected E. cloacae isolate was resistant to tobramycin and capable of forming biofilms. Nine rabbits received 125 mg tobramycin powder directly into the surgical site, overlying the implant. The control group was untreated. Fourteen days postinfection, the tibiae and implants were explanted. Radiographs were taken with and without the implants in place. One tibia from each group was examined after hematoxylin and eosin staining. The remaining tibiae and implants were morselized or sonicated, respectively, and plated on agar to determine infection burden. Data were analyzed with Fisher exact tests and Mann-Whitney U tests. RESULTS: No bone infection or implant colonization occurred in the tobramycin-treated group. In the control group, 7 of 8 rabbits developed bone infections (P = 0.001), and 4 of 8 implants were colonized (P = 0.07). No gross disruption of the normal bone architecture was observed in either group. CONCLUSIONS: Intraoperative tobramycin powder applied at the time of contamination prevented bone infection with E. cloacae in this rabbit fixation model. The results are encouraging because the E. cloacae isolate was tobramycin-resistant, demonstrating the utility of intraoperative powdered antibiotics.

Association Between Femoral "Spike" Size After Intramedullary Nailing and Subsequent Knee Motion Surgery.

OBJECTIVES: To determine the association between displaced femoral shaft bone fragments ("spikes") seen on radiographs after intramedullary nail insertion and the need for future motion surgery. DESIGN: Retrospective case-control study. SETTING: Academic trauma center. PATIENTS: We included patients with femoral shaft fractures treated with intramedullary nail insertion. Case patients (n = 22) had developed knee stiffness treated with motion surgery. The control group was a randomly selected sample (1:3 ratio). MAIN OUTCOME MEASURES: Motion surgery to address knee stiffness. We defined a "spike distance ratio" and "spike area ratio" from initial postoperative anteroposterior and lateral radiographs. Multivariable logistic regression determined the effect of spike distance and area ratios on the likelihood of need for motion surgery, controlling for polytraumatic injuries and bilateral fractures. RESULTS: The case group had a median femoral spike distance ratio of 1.9 [interquartile range (IQR), 1.6-2.5] compared with 1.5 (IQR, 1.2-1.8) in the control group. An increased femoral spike distance ratio was associated with increased odds of motion surgery (P < 0.01). A femoral spike distance >2 times the femoral radius had 32 times the odds (95% confidence interval, 2-752) of motion surgery compared with patients with distance ratios <1.25. Median femoral spike area ratios were similar between the case (0.2; IQR, 0.1-0.5) and control (0.2; IQR, 0.0-0.5) groups and were not associated with increased odds of motion surgery (P = 0.34). CONCLUSIONS: A larger spike distance ratio is associated with increased odds of subsequent motion surgery. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Surgeons Cannot Predict Pilon Fracture Outcomes Based on Initial Radiographs.

This study sought to determine (1) whether surgeons can accurately predict functional outcomes of operative fixation of pilon fractures based on injury and initial postoperative radiographs, (2) whether the surgeon's level of experience is associated with the ability to successfully predict outcome, and (3) the association between patients' demographic and clinical characteristics and surgeons' prediction scores. A blinded, randomized provider survey was conducted at a level I trauma center. Seven fellowship-trained orthopedic traumatologists and 4 orthopedic trauma fellows who were blinded to outcome reviewed data regarding 95 pilon fractures in random order. Injury ankle radiographs, initial postoperative fixation radiographs, and brief patient histories were assessed. Midterm follow-up functional outcome scores obtained a mean 4.9 years after surgery were available for all patients. Main outcome measures were Pearson correlation coefficient-assessed functional outcomes and surgeon-predicted outcomes. A mixed-effect model determined the association between patients' characteristics and surgeons' prediction scores. Minimal positive correlation was observed between functional outcomes and prediction scores. No difference was noted between the attending and fellow groups in prediction ability. When surgeons' prediction confidence level was greater than 1 SD above the mean confidence level, correlation between functional outcome and prediction improved, although poor correlation was still observed. AO/OTA type 43C fractures, high-energy mechanisms, and older patient age were characteristics associated with lower prediction scores. Surgeons had poor ability to predict functional outcomes of patients with pilon fractures based on injury and initial postoperative radiographs, and level of experience was not associated with ability to predict outcome. [Orthopedics. 2020; 43(1): e43-e46.].

The Feasibility of a Randomized Controlled Trial for Open Tibial Fractures at a Regional Hospital in Uganda.

BACKGROUND: The inclusion of low and middle-income country (LMIC) hospitals in multicenter orthopaedic trials expands the pool of eligible patients and improves the external validity of the evidence. Furthermore, promoting studies in LMIC hospitals defines the optimal treatments for low-resource settings, the conditions under which the majority of musculoskeletal injuries are treated. The objective of this study was to determine the feasibility of a randomized controlled trial comparing external fixation with intramedullary (IM) nailing in patients with an isolated open tibial fracture who presented to a regional hospital in Uganda. METHODS: From July 2016 to July 2017, skeletally mature patients who presented to a Ugandan regional hospital with an isolated Gustilo-Anderson type-II or IIIA open fracture of the tibial shaft were eligible for inclusion. The primary feasibility outcomes were the enrollment rate, the recruitment rate, and the 3 and 12-month follow-up rates. The secondary outcomes included a comparison of 3 and 12-month follow-up rates between the treatment arms and a qualitative assessment of barriers to enrollment, timely treatment, and missed follow-up. RESULTS: During the 12-month enrollment period, 37.5% (30 of 80) of eligible patients were successfully enrolled and operatively treated on the basis of their random allocation, with an enrollment rate of 2.5 patients per month. Of the 30 enrolled patients, 53% completed their 3-month follow-up appointment, and 40% completed their 1-year follow-up appointment. Rates of 1-year follow-up were significantly higher for patients receiving IM nails than for those receiving external fixation (absolute difference, 52%; 95% confidence interval [CI], 21 to 83, p < 0.01). The main reasons that patients declined to participate in the trial were preferences for treatment by traditional bonesetters and prehospital delays that were related to a disorganized referral system. Barriers to follow-up included prohibitive transportation costs and community pressure to turn to traditional forms of treatment. CONCLUSIONS: A regional hospital in Uganda can successfully enroll, randomize, and operatively treat multiple patients with an open tibial fracture each month. Patient follow-up presents substantial concerns over trial feasibility in this setting. Cultural pressure to utilize traditional treatments remains a particularly common barrier to study-participant enrollment and retention.

Intraoperative Vancomycin Powder Reduces Staphylococcus aureus Surgical Site Infections and Biofilm Formation on Fixation Implants in a Rabbit Model.

OBJECTIVES: To evaluate the effectiveness of intraoperative vancomycin powder in prevention of surgical site infection and biofilm formation on implants in a contaminated animal fixation model. METHODS: We created a rabbit surgical model including fixation implants at a tibial surgical site seeded with methicillin-resistant Staphylococcus aureus. Our study cohort included 18 rabbits. Nine received vancomycin powder at the surgical site, and the other 9 did not. Serum vancomycin levels were measured at scheduled time points over 24 hours. Bone infection and implant biofilm formation were determined based on the number of colony-forming units present 2 weeks after surgery. Radiography, histology, and electron microscopy aided in evaluation. RESULTS: No bone infection or implant colonization occurred in the vancomycin powder group. Six bone infections and 6 implant biofilm formations (67%; 95% confidence interval, 45%-88%) occurred in the group that did not receive vancomycin powder (P = 0.009). Serum vancomycin levels were detectable at minimal levels at 1 and 6 hours only. Pathological changes occurred in the specimens that were positive for infection. CONCLUSIONS: Intraoperative vancomycin powder application at the time of fixation decreases risk for bone infection and biofilm formation on implants in a rabbit model, with minimal increase in serum vancomycin levels. The results are encouraging and support the rationale for a clinical trial investigating the use of local vancomycin powder to reduce the rate of surgical site infections. CLINICAL RELEVANCE: Infection is a common complication of surgery, especially with implants. Simple methods to prevent or decrease the occurrence of infection would benefit the patient and the health care system.

Risk Factors for Knee Stiffness Surgery After Tibial Plateau Fracture Fixation.

OBJECTIVE: To determine the risk factors for knee stiffness surgery after tibial plateau fixation. DESIGN: Retrospective observational cohort study. SETTING: Academic Level I trauma center. PATIENTS/PARTICIPANTS: A study group of 110 patients who underwent knee stiffness surgery (manipulation while under anesthesia, arthroscopic lysis of adhesion, or quadricepsplasty) at a time remote from open reduction and internal fixation of tibial plateau fractures and a control group of 319 patients with tibial plateau fractures treated with open reduction and internal fixation who did not undergo knee stiffness surgery and who had either a minimum of 1 year of follow-up or clearly documented range of motion ≥110 degrees with a minimum of 90 days of follow-up. INTERVENTION: Each case was assessed from the time of index admission through study event, end of minimum follow-up, or achievement of ≥110 degrees range of motion. MAIN OUTCOME MEASUREMENTS: Knee stiffness surgery. RESULTS: Total number of weeks in an external fixator (odds ratio, 1.5 per week; 95% confidence interval, 1.3-1.7; P < 0.001) and the presence of bilateral tibial plateau fractures (odds ratio, 3.3; 95% confidence interval, 1.2-9.1; P = 0.02) were significant predictors of knee stiffness intervention. CONCLUSION: Clinicians should be aware that the time spent in external fixation and the presence of bilateral tibial plateau injuries are strong risk factors for requiring subsequent surgery to treat knee stiffness. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Post-discharge adherence with venous thromboembolism prophylaxis after orthopedic trauma: Results from a randomized controlled trial of aspirin versus low molecular weight heparin.

BACKGROUND: Orthopedic trauma patients are often treated with venous thromboembolism (VTE) chemoprophylaxis with aspirin or low molecular weight heparin (LMWH) after discharge from their index admission, but adherence patterns are not known. We hypothesized that overall adherence would be moderate and greater with aspirin compared to LMWH. METHODS: We conducted a randomized controlled trial of adult trauma patients with an operative extremity fracture or any pelvic/acetabular fracture requiring VTE prophylaxis. Patients were randomized to receive either LMWH 30 mg BID or aspirin 81 mg BID. Patients prescribed outpatient prophylaxis were contacted between 10 and 21 days after discharge to assess adherence measured by the validated Morisky Medication Adherence Scale (MMAS-8). Adherence scores were compared between the two treatment arms with similar results for intention-to-treat and as-treated analyses. As-treated multivariable logistic regression was performed to determine factors associated with low-medium adherence scores. RESULTS: One hundred fifty patients (64 on LMWH, 86 on aspirin) on chemoprophylaxis at time of follow-up completed the questionnaire. As-treated analysis showed that adherence was high overall (mean MMAS 7.2 out of 8, SD 1.5) and similar for the two regimens (LMWH: 7.4 vs. aspirin: 7.0, p = 0.13). However, patients on LMWH were more likely to feel hassled by their regimen (23% vs. 9%, p = 0.02). In a multivariable model, low-medium adherence was associated with taking LMWH as the prophylaxis medication (aOR 2.34, CI 1.06-5.18, p = 0.04), having to self-administer the prophylaxis (aOR 4.44, CI 1.45-13.61, p < 0.01), being of male sex (aOR 2.46, CI 1.10-5.49, p = 0.03), and of younger age (aOR 0.72 per additional 10 years of age, CI 0.57-0.91, p < 0.01). CONCLUSIONS: Overall post-discharge adherence with VTE prophylaxis was high. Several factors, including prophylaxis by LMWH, were associated with decreased adherence. These factors should be considered when managing patients and designing efficacy trials. LEVEL OF EVIDENCE: Therapeutic, level II.