From January 2015 to June 2017, eighty-one patients who underwent revision surgery due to PJI after hip and knee arthroplasty in our center were retrospectively collected. Four patients who failed to follow-up were excluded (bacterial culture results were positive and underwent two-stage revision). Ultimately, 77 PJI cases of the hip and knee were enrolled.
Age, sex, body mass index (BMI), preoperative complications, American Association of Anesthesiologists (ASA) physical status, laboratory tests (routine blood test, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)), preoperative and intraoperative synovial fluid white blood cell (SF-WBC) count and percentage of polymorphonuclear leukocytes (SF-PMN%), bacterial culture results and intraoperative frozen section results of periprosthetic tissue were collected. The incidence of PJI after total joint arthroplasty (type, sinus, pathogenic microorganism), surgical strategies (one-stage revision, two-stage revision and debridement, antibiotics, irrigation, and retention (DAIR)), antibiotic regimens and clinical results were also documented. A diagnosis for PJI were made according to the Musculoskeletal Infection Society (MSIS) criteria for PJI8,9.
All patients were classified by Tsukayama type10,11. According to the bacterial culture results of synovial fluid and pre- and intraoperative tissues, 24 cases were included in the CN PJI group, and 53 cases were included in the CP PJI group.
Surgical strategies and postoperative antibiotic regimens
Generally, for cases of Tsukayama type II or III without a sinus tract, DAIR was selected. For cases classified as Tsukayama type I or IV without a sinus tract and where multiresistance bacteria was isolated from the preoperative synovial fluid, as well as cases involving elderly populations and poor economic conditions combined with the wishes of the patients, one-stage revision surgery was chosen. For cases classified as Tsukayama type IV with poor soft tissue conditions and where multiresistance bacteria was isolated from preoperative synovial fluid as well as the existence of a sinus, two-stage revision was selected. And patient's willingness was also taken into consideration.
If the bacterial culture results were negative, the administration of vancomycin and third-generation cephalosporin or carbapenem antibiotics were combined intravenously. If the bacterial culture results were positive, proper sensitive antibiotics were selected. All patients received intravenous antibiotics for two to six weeks (mean time: 20 days for DAIR, 16 days for one-stage revision, and 31 days for two-stage revision). After that, the antibiotic regimens were switched to oral antibiotics. Rifampicin combined with sensitive antibiotics was selected for staphylococcal infections and only sensitive antibiotics for other positive cultures, quinolone antibiotics were selected for negative culture, and the course of antibiotics administered was six to ten weeks, with a total of 12 weeks. Antibiotics were administered intravenously for 7-14 days after the second stage of reimplantation. If the pathogenic microorganism culture was positive during reimplantation, antibiotics were orally taken for eight to ten weeks after two to four weeks of sensitive antibiotic administration according to drug-sensitive veins, with a total course of treatment of 12 weeks.
All patients underwent routine blood tests, liver and renal function tests, and ESR and CRP measurements. The patients were followed regularly (3 months, six months, one year after the operation, and once a year thereafter, with a minimum follow-up of 2 years). The ESR and CRP level were reexamined at each follow-up.
Successful treatment was evaluated according to the definition established by the international consensus in 2013 12: 1. infection eradication, characterized by good wound healing and no exudation, sinus or wound pain; 2. no infection-related surgical intervention after reimplantation; and 3. no infection-related death (caused by septicemia, necrotizing fasciitis, etc. ).
Antibiotic-related complications: 1. myelosuppression: a preoperative routine WBC count of > 4*109/L and a maximum value of WBCs during intravenous or oral antibiotics < 3 * 109/l; 2. liver function damage: before the operation, the liver function alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were all normal, and the peak value of ALT or AST during intravenous or oral antibiotics increased more than 1.5 times; 3. renal function damage: the creatinine level characteristic of renal function was within the normal range before the operation, and the creatinine value increased more than 1.5 times the initial value during intravenous or oral antibiotic administration.
The χ2 test and F-test were used to compare the differences in demographic characteristics and comorbidities between CN PJI and CP PJI. Continuous variables such as age, body mass index and ASA between groups were analyzed by independent sample t test if they obeyed a normal distribution; otherwise, the Mann-Whitney U test was performed. Kaplan-Meier survival analysis and log-rank tests were used to compare the success rates of CN PJI and CP PJI. The χ2 test and F-test were used to compare the incidence of antibiotic complications. Logistic regression was used to further analyze the correlation between sex, age, basic diseases, sinus tract, joint involvement, surgical strategies, culture results and clinical outcomes. All statistical analyses were conducted with IBM SPSS version 22.0, and all tests were conducted with bilateral tests. P<0.05 was considered statistically significant.
This study was approved by the Ethics Committee of the First Affiliated Hospital of Fujian Medical University.