Study Design. Retrospective analysis. Objective. The objective of this study was to describe the microbiology of surgical site infection (SSI) in spine surgery and relationship with surgical management characteristics. Summary of Background Data. SSI is an important complication of spine surgery that results in significant morbidity. A comprehensive and contemporary understanding of the microbiology of postoperative spine infections is valuable to direct empiric antimicrobial treatment and prophylaxis and other infection prevention strategies. Methods. All cases of spinal surgery associated with SSI between July 2005 and November 2010 were identified by the hospital infection control surveillance program using Centers for Disease Control National Health Safety Network criteria. Surgical characteristics and microbiologic data for each case were gathered by direct medical record review. Results. Of 7529 operative spine cases performed between July 2005 and November 2010, 239 cases of SSI were identified. The most commonly isolated pathogen was Staphylococcus aureus (45.2%), followed by Staphylococcus epidermidis (31.4%). Methicillin-resistant organisms accounted for 34.3% of all SSIs and were more common in revision than in primary surgical procedures (47.4% vs. 28.0%, P = 0.003). Gram-negative organisms were identified in 30.5% of the cases. Spine surgical procedures involving the sacrum were significantly associated with gram-negative organisms (P < 0.001) and polymicrobial infections (P = 0.020). Infections due to gram-negative organisms (P = 0.002) and Enterococcus spp. (P = 0.038) were less common in surgical procedures involving the cervical spine. Cefazolin-resistant gram-negative organisms accounted for 61.6% of all gram-negative infections and 18.8% of all SSIs. Conclusion. Although gram-positive organisms predominated, gram-negative organisms accounted for a sizeable portion of SSI, particularly among lower lumbar and sacral spine surgical procedures. Nearly half of infections in revision surgery were due to a methicillin-resistant organism. These findings may help guide choice of empiric antibiotics while awaiting culture data and antimicrobial prophylaxis strategies in specific spine surgical procedures.

Negative culture result is frequently encountered in periprosthetic joint infection, but its clinical feature has not been well studied. In this study, clinical characteristics and treatment outcome were compared in two patient groups: (1) 40 periprosthetic joint infections with negative culture results (culture-negative group) and (2) 135 patients with positive culture results (culture-positive group). In comparison of two groups, the culture-negative group showed significantly higher incidence of prior antibiotic use (p = 0.005), higher incidence of prior resection surgery (p < 0.001) and lower ESR (p = 0.02) than the culture-positive group. The success rate of infection control was higher in the culture-negative group (p = 0.006), which suggests that culture negativity may not necessarily be a negative prognostic factor for periprosthetic joint infection.

This study evaluates the long-term survival of spinal implants after surgical site infection (SSI) and the risk factors associated with treatment failure. A Kaplan-Meier survival analysis was carried out on 43 patients who had undergone a posterior spinal fusion with instrumentation between January 2006 and December 2008, and who consecutively developed an acute deep surgical site infection. All were appropriately treated by surgical debridement with a tailored antibiotic program based on culture results for a minimum of eight weeks. A ‘terminal event’ or failure of treatment was defined as implant removal or death related to the SSI. The mean follow-up was 26 months (1.03 to 50.9). A total of ten patients (23.3%) had a terminal event. The rate of survival after the first debridement was 90.7% (95% confidence interval (CI) 82.95 to 98.24) at six months, 85.4% (95% CI 74.64 to 96.18) at one year, and 73.2% (95% CI 58.70 to 87.78) at two, three and four years. Four of nine patients required re-instrumentation after implant removal, and two of the four had a recurrent infection at the surgical site. There was one recurrence after implant removal without re-instrumentation. Multivariate analysis revealed a significant risk of treatment failure in patients who developed sepsis (hazard ratio (HR) 12.5 (95% confidence interval (CI) 2.6 to 59.9); p < 0.001) or who had > three fused segments (HR 4.5 (95% CI 1.25 to 24.05); p = 0.03). Implant survival is seriously compromised even after properly treated surgical site infection, but progressively decreases over the first 24 months. Cite this article: Bone Joint J 2013;95-B:1121–6.

Background: An intraoperative culture sample obtained during revision elbow arthroplasty that is unexpectedly positive poses a dilemma for the surgeon. The purpose of our study was to determine the prevalence of positive cultures during revision elbow arthroplasty when infection is not suspected preoperatively, and the long-term implications of these positive cultures. Methods: Two hundred and thirteen consecutive revision elbow arthroplasties were performed at our institution between 2000 and 2007. Of these, sixteen patients had unexpected positive intraoperative cultures. Results: The majority of cultures grew either Staphylococcus epidermidis or Propionibacterium acnes. Twelve patients had more than two years of follow-up. One of the twelve patients was treated as for an infection because of unexplained early implant loosening and the isolation of Staphylococcus epidermidis. Ten of the twelve elbows were treated as “contaminants” and did not receive long-term antibiotic treatment. Nine of these ten remained infection-free at the time of the final follow-up, while the remaining one developed an infection with a different organism. Conclusions: In our series, there was a 7.5% chance of encountering an unexpected positive result on intraoperative culture at the time of revision elbow arthroplasty. The majority of patients were successfully treated without antibiotics with a low rate of failure. A minority were considered as infections, typically presenting with unexplained early loosening and isolation of an organism on solid culture medium.

BACKGROUND: Up to 2% of THAs are complicated by infection, leading to dissatisfied patients with poor function and major social and economic consequences. The challenges are control of infection, restoration of full function, and prevention of recurrence. Irrigation and débridement with or without exchange of modular components remains an attractive alternative to two-stage reimplantation in acutely infected THAs but with variable results from previous studies. QUESTIONS/PURPOSES: We therefore determined the rate at which aggressive early débridement with exchange of modular components controlled acutely infected cemented THAs. METHODS: We retrospectively studied all 26 patients presenting with acutely infected cemented THAs (16 primaries, 10 revisions) occurring within 6 weeks of the index operation or of hematogenous spread from a confirmed source of infection elsewhere between 1999 and 2006. Microbiology confirmed bacterial colonization in all patients, with 18 early postoperative infections and eight acute hematogenous infections. Patients underwent aggressive débridement with open complete synovectomy, exchange of all mobile parts, débridement of all aspects of the joint, irrigation with antiseptic solutions, and pulsatile lavage. Minimum followup was 5 years (mean, 6.6 years; range, 5-11 years). RESULTS: Eight patients had multiple washouts with control of infection in four at latest followup. Five patients underwent two-stage revisions and one patient was placed on long-term antibiotic suppression. Twenty patients returned to their expected functional level with no radiographic evidence of prosthetic failure. At minimum 5-year followup, we had a 77% infection control rate. CONCLUSIONS: Our data confirm current literature and suggest there may be a role for aggressive early débridement in controlling acute postoperative and hematogenous infections after cemented THA. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Study design: Retrospective review of a prospectively collected database. Objective: Our objective was to assess the rates of postoperative wound infection associated with spine surgery. Summary of background data: Although wound infection after spine surgery remains a common source of morbidity, estimates of its rates of occurrence remain relatively limited. The Scoliosis Research Society prospectively collects morbidity and mortality data from its members, including the occurrence of wound infection. Methods: The Scoliosis Research Society morbidity and mortality database was queried for all reported spine surgery cases from 2004 to 2007. Cases were stratified based on factors including diagnosis, adult (≥ 21 years) versus pediatric (<21 years), primary versus revision, use of implants, and whether a minimally invasive approach was used. Superficial, deep, and total infection rates were calculated. RESULTS.: In total, 108,419 cases were identified, with an overall total infection rate of 2.1% (superficial = 0.8%, deep = 1.3%). Based on primary diagnosis, total postoperative wound infection rate for adults ranged from 1.4% for degenerative disease to 4.2% for kyphosis. Postoperative wound infection rates for pediatric patients ranged from 0.9% for degenerative disease to 5.4% for kyphosis. Rate of infection was further stratified based on subtype of degenerative disease, type of scoliosis, and type of kyphosis for both adult and pediatric patients. Factors associated with increased rate of infection included revision surgery (P < 0.001), performance of spinal fusion (P < 0.001), and use of implants (P < 0.001). Compared with a traditional open approach, use of a minimally invasive approach was associated with a lower rate of infection for lumbar discectomy (0.4% vs. 1.1%; P < 0.001) and for transforaminal lumbar interbody fusion (1.3% vs. 2.9%; P = 0.005). Conclusion: Our data suggest that postsurgical infection, even among skilled spine surgeons, is an inherent potential complication. These data provide general benchmarks of infection rates as a basis for ongoing efforts to improve safety of care.

Background Clinical characteristics and control of the infection of patients with culture-negative (CN) prosthetic joint infection (PJI) have not been well assessed. Prior use of antimicrobial therapy has been speculated but not proven as a risk factor for CNPJI. Questions/purposes We therefore determined whether prior use of antimicrobial therapy, prior PJI, and postoperative wound healing complications were associated with CN PJI. Methods We performed a retrospective case-control study of 135 patients with CN PJI treated between January 1, 1985, and December 31, 2000 matched with 135 patients with culture-positive (CP) PJIs (control patients) during the study period. The time to failure of therapy compared between cases and control patients using a Kaplan-Meier analysis. Results The use of prior antimicrobial therapy and postoperative wound drainage after index arthroplasty were associated with increased odds of PJI being culture-negative (odds ratio, 4.7; 95% CI, 2.8-8.1 and odds ratio, 3.5; 95% CI, 1.5-8.1, respectively). The percent (± SE) cumulative incidence free of treatment failure at 2 years followup was similar for CN and CP PJI: 75% (± 4%) and 79% (± 4%), respectively. Conclusions Prior antimicrobial therapy and postoperative wound drainage were associated with an increased risk of negative cultures among patients with PJI. Physicians should critically evaluate the need for antimicrobial therapy before establishing a microbiologic diagnosis of PJI in patients with suspected PJI.

Background: This prospective investigation was designed to determine if the postoperative infection rate in instrumented lumbar spinal fusion is affected by postoperative antibiotic use. Methods: Two hundred sixty-nine patients were randomized into either a preoperative only protocol or preoperative with an extended postoperative antibiotic protocol. The preoperative only protocol received a single dose of cefazolin IV. The extended postoperative antibiotic protocol received the same preoperative dose plus postoperative cefazolin IV every 8 hours for 3 days followed by oral cephalexin every 6 hours for 7 days. Because of untoward drug reaction or deviation from the antibiotic protocol, 36 of the 269 patients were eliminated from the study. Therefore, 233 patients completed the entire study. Results: There was no significant difference in infection rates between the 2 antibiotic protocols. The postoperative infection rates were 4.3% for the preoperative only protocol and 1.7% for the preoperative with extended antibiotic protocol. The overall postoperative infection rate was 3%. However, 5 variables of blood transfusion, electrophysiologic monitoring, increased height, increased weight, and increased body mass index appeared to demonstrate a trend toward increase in infection rate. Increased tobacco use trended toward a lower infection rate. Conclusion: Statistical significance was not proven in this prospective study comparing single-dose preoperative antibiotic protocol vs preoperative with an extended postoperative antibiotic protocol. A larger study of 1400 patients would possibly provide more statistically significant information.

Background. Culture-negative (CN) prosthetic joint infection (PJI) has not been well studied. We performed a retrospective cohort study to define the demographic characteristics and determine the outcome of patients with CN PJI. Methods. All cases of CN total hip arthroplasty and total knee arthroplasty infections (using a strict case definition) treated at our institution from January 1990 through December 1999 were analyzed. Kaplan-Meier survival methods were used to determine the cumulative probability of success. Results. Of 897 episodes of PJI during the study period, 60 (7%) occurred in patients for whom this was the initial episode of CN PJI. The median age of the cohort was 69 years (range, 36–87 years). Patients had received a prior course of antimicrobial therapy in 32 (53%) of 60 episodes. Of the 60 episodes, 34 (57%), 12 (20%), and 8 (13%) were treated with 2-stage exchange, debridement and retention, and permanent resection arthroplasty, respectively. The median duration of parenteral antimicrobial therapy was 28 days (range, 0–88 days). Forty-nine (82%) of 60 episodes were treated with a cephalosporin. The 5-year estimate of survival free of treatment failure was 94% (95% confidence interval, 85%–100%) for patients treated with 2-stage exchange and 71% (95% confidence interval, 44%–100%) for patients treated with debridement and retention. Conclusions. CN PJI occurs infrequently at our institution. Prior use of antimicrobial therapy is common among patients with CN PJI. CN PJI treated at our institution is associated with a rate of favorable outcome that is comparable to that associated with PJI due to known bacterial pathogens.

Background. Spinal implant infections provide unique diagnostic and therapeutic challenges. Methods. We conducted a retrospective cohort study to evaluate risk factors for treatment failure in patients with early- and late- onset spinal implant infections at the Mayo Clinic (Rochester, MN) during 1994–2002. Results. We identified 30 patients with early-onset spinal implant infection and 51 patients with late-onset spinal implant infection. Twenty-eight of 30 patients with early-onset infection were treated with debridement, implant retention, and antimicrobial therapy. The estimated 2-year cumulative probability of survival free of treatment failure for patients with early-onset infection was 71% (95% confidence interval [CI], 51%–85%). Thirty-two of 51 patients with late-onset infection were treated with implant removal. Their estimated 2-year cumulative probability of survival free of treatment failure was 84% (95% CI, 66%–93%). For patients with early-onset infections, receiving oral antimicrobial suppression therapy was associated with increased cumulative probability of survival (hazard ratio, 0.2; 95% CI, 0.1–0.7). For patients with late-onset infections, implant removal was associated with increased cumulative probability of survival (hazard ratio, 0.3; 95% CI, 0.1–0.7). Conclusions. Early-onset spinal implant infections are successfully treated with debridement, implant retention, and parenteral followed by oral suppressive antimicrobial therapy. Implant removal is associated with successful outcomes in late-onset infections.

Intra-operative incidental contamination of surgical wounds is not rare. Povidone-iodine solution can be used to disinfect surgical wounds. Although povidone-iodine is a good broad-spectrum disinfecting agent, it has occasionally been reported to have a negative effect on wound healing and bone union. Therefore, its safety in a spinal surgery is unclear. A prospective, single-blinded, randomized study was accordingly conducted to evaluate the safety of povidone-iodine solution in spinal surgeries. Ascertained herein was the effect of wound irrigation with diluted povidone-iodine solution on wound healing, infection rate, fusion status and clinical outcome of spinal surgeries. Materials and methods: From January 2002 to August 2003, 244 consecutive cases undergoing primary instrumented lumbosacral posterolateral fusion due to degenerative spinal disorder with segmental instability had been collected and randomly divided into two groups: the study group (120 cases, 212 fusion levels) and the control group (124 cases, 223 fusion levels). Excluded were those patients with a prior spinal surgery, spinal trauma, malignant tumor, infectious spondylitis, rheumatoid arthritis, ankylosing spondylitis, metabolic bone disease, skeletal immaturity or with an immunosuppressive treatment. In the former group, wounds were irrigated with 0.35% povidone-iodine solution followed by normal saline solution just before the bone-grafting and instrumentation procedure. However, only with normal saline solution in the latter. All the operations were done by the same surgeon with a standard technique. All the patients were treated in the same postoperative fashion as well. Later on, wound healing, infection rate, spinal bone fusion and clinical outcome were evaluated in both groups. Results: A significant improvement of back and leg pain scores, modified Japanese Orthopedic Association function scores (JOA) and ambulatory capacity have been observed in both groups. One hundred and seven patients in the study group and one hundred and nine in the control group achieved solid union. There was no infection in the study group but six deep infections in the control group. Wound dehiscence was noted in one group 1 and two group 2 patients. A subsequent statistical analysis revealed higher infection rate in the control group (P<0.05), but no significant difference in fusion rate, wound healing, improvement of pain score, function score and ambulatory capacity between the two groups. Conclusion: Diluted povidone-iodine solution can be used safely in spinal surgeries, and it will not influence wound healing, bone union and clinical outcome.

Eight patients with shoulder sepsis were treated with staged exchange arthroplasty using antibiotic-impregnated polymethyl methacrylate spacers shaped and fitted to the patient's anatomy after extensive joint débridement. Intravenous antibiotic therapy followed for a minimum of 3 months. At the end of 6 months, the patients were evaluated for any clinical or laboratory signs of infection; none were encountered. Exchange prosthetic reconstructions were performed using standard implants fixed with antibiotic-impregnated polymethyl methacrylate cement. Three patients underwent a revision to total shoulder arthroplasty, whereas 5 underwent hemiarthroplasty of the humerus with local capsular flap covering of the glenoid. All patients experienced substantial pain relief and improvement in function despite limited total overhead motion, showing this technique to be a satisfactory salvage procedure for managing sepsis of the glenohumeral joint primarily and after total shoulder arthroplasty.