Identifying Common Pathogens in Periprosthetic Joint Infection and Testing Drug-resistance Rate for Different Antibiotics: A Prospective, Single Center Study in Beijing.

OBJECTIVE: The aim of this study is to identify the common microorganisms causing PJI as well as the drug-resistant spectrum for each microorganism, to help orthopaedic surgeons to choose appropriate antibiotics. METHOD: One hundred and sixty patients who suffered from failure of primary or revision total hip or knee arthroplasty for different reasons were prospectively recruited. These patients underwent revision or re-revision total hip or knee arthroplasty in our institution between August 2013 to August 2016. The details of patients' medical history and comprehensive physical examination, as well as demographic data were recorded precisely. Routine blood test results, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), high sensitive C-reactive protein (hs-CRP), interleukin-6 (IL-6) levels, and synovial leukocyte counts were collected. Additionally, aspiration was conducted during surgery to avoid pollution unless when PJI was strongly suspected, in which case, joint puncture and aspiration were conducted before surgery. Intraoperatively, the implant-surrounding tissue and the prosthesis were collected under aseptic conditions. Postoperatively, the prosthesis, implant-surrounding tissue and synovium were sent to the laboratory immediately. The sonicate extraction (the prosthesis was sent for ultrasound sonication first), implant surrounding tissue and synovium were sent for microbiologic culture, and the implant-surrounding tissue was also sent for pathological examination. The isolated bacteria strains and drug-resistance rates for each pathogen for different antibiotics were presented. RESULTS: There were 59 PJI cases in the infectious group and 101 cases in the non-infectious group (PJI is diagnosed according to the diagnosing criteria from the Workgroup of the Musculoskeletal Infection Society). Of 69 strains of pathogens isolated, Gram-positive bacterium is the most common pathogenic bacteria causing PJI (60, 86.96%). Staphylococcus epidermidis and Staphylococcus aureus played an important role as well, followed by Gram-negative bacteria (8, 11.59%) and fungus (1, 1.45%). Penicillin (78.57%), erythromycin (66.67%) and clindamycin (44.74%) showed high antibiotic resistance rate. In addition, the second-generation cephalosporin, usually as the prophylactic antibiotic, resistance rate was high (20%) as well. Fortunately, no vancomycin-resistant bacteria were discovered in the current study. CONCLUSION: This study provides some information on the most common pathogens in our institution and the selection of antibiotics in the perioperative period in northern China. Cefuroxime and clindamycin might not be appropriate for use as prophylactic antibiotics in revision total knee or hip arthroplasty. Vancomycin is ideal for empiric antibiotic use in suspected PJI cases because of the low drug-resistance rate.

Possible predictors for difficult removal of locking plates: A case-control study.

INTRODUCTION: Difficult removal of locking plates including less invasive stabilisation systems (LISSs) and locking compression plates (LCPs) sometimes occur. However, investigations of the mechanisms and correlated factors of complicated removal remain scant. This study aims to identify correlated factors for the difficult removal of locking plates and to propose suggestions for decision making regarding implant removal and the prevention of complicated removal. MATERIALS AND METHODS: In total, 308 consecutive patients who underwent LCP/LISS removal from Sep. 2004 to Nov. 2013 were assessed. Using the Mann-Whitney U test, we analysed the correlation between difficult removal and the duration between open reduction and internal fixation (ORIF) and implant removal as well as the correlation between difficult removal and the patients' age. Using Chi Square test, we assessed the correlations between complicated removal and the size, location, insertion technique and cortical purchase of the locking head screw (LHS). Correlated factors were separately determined in upper and lower extremities. Rates of difficult removal in different fracture locations were evaluated, and postoperative complications were documented. RESULTS: Of the total 308 patients, thirty-seven had intra-operative difficulties, and six patients experienced postoperative complications. Six out of fifteen patients with peri-elbow fractures and five out of seventeen patients with femur fractures suffered difficult removal, while four out of one hundred patients with malleolar fractures had intra-operative difficulties. Difficulties were experienced with 30 of 338 LCPs, 7 of 32 LISSs, 67 of 1533 small-diameter (≤ 3.5-mm) LHSs, and 12 of 442 large-diameter (≥ 4.5-mm) LHSs. Three LCPs and seventeen small-diameter LHSs were retained. A longer interval between ORIF and removal, younger age and bicortical screws correlated with difficult removal in the upper extremities, and a longer duration before removal, small-diameter LHS and minimally invasive insertion of LHS were predictors in the lower extremities. CONCLUSIONS: Complications occur with LCP/LISS removal, and it should not be a routine procedure. If removal is indicated, performing surgery as soon as radiographs show fracture healing is recommended. Different considerations should apply when making decisions and removing implants from patients with different fracture sites.

Development and validation of a risk prediction model for tracheostomy in acute traumatic cervical spinal cord injury patients.

PURPOSE: Tracheostomy may become indispensable for patients with acute traumatic cervical spinal cord injuries. However, the early prediction of a tracheostomy is often difficult. Previous prediction models using the pulmonary function test (PFT) have limitations because some severely injured patients could not provide acceptable PFT results. We aim to develop an alternative model for predicting tracheostomy using accessible data obtained from the bedside. METHOD: Clinical, neurological and radiological data from 345 consecutive patients with acute tetraplegia were retrospectively reviewed. We applied multiple logistic regression analysis (MLRA) and classification and regression tree (CART) analysis to develop the prediction model for tracheostomy. By train-test cross-validation, we used the sensitivity, specificity, area under the receiver operating characteristics curve (AUC) and correction rate to evaluate the performance of these models. RESULTS: According to the American Spinal Injury Association (ASIA) standards, an admission ASIA motor score (AAMS) ≤ 22, ASIA grade A and presence of respiratory complications were identified as independent predictors of tracheostomy by both models. The model derived by CART suggested that the highest signal change (HSC) in the spinal cord on magnetic resonance imaging (MRI) also affected a patient's requirement for a tracheostomy, while MLRA demonstrated that tracheostomy was also influenced by the presence of an ASIA grade B injury. The CART model had a sensitivity of 73.7%, specificity of 89.7%, AUC of 0.909 and overall correction rate of 87.3%. The sensitivity, specificity, AUC and correction rate of the MLRA model were 81.8, 86.4, 0.889 and 85.7%, respectively. CONCLUSIONS: We suggest using the CART model in clinical applications. Patients with AAMS ≤ 1 exhibit an increased likelihood of requiring a tracheostomy. For patients with an AAMS in the range of 2-22, surgeons should consider giving these patients a tracheostomy once respiratory complications occur. Surgeons should be cautious to give a tracheostomy to patients with an AAMS ≥ 23, if the patient experiences an incomplete spinal cord injury and the HSC in the spinal cord is at C3 level or lower based on MRI. For other patients, close observation is necessary; generally, patients with complete SCI might require a tracheostomy more frequently.