Surgical Site Infection After Surgery to Repair Femoral Neck Fracture: A French Multicenter Retrospective Study
Objective. Femoral neck fracture is the most frequent orthopedic emergency among elderly persons. Despite a high prevalence of methicillin‐resistant Staphylococcus aureus (MRSA) carriage in this population, no multicenter study of antibiotic prophylaxis practices and the rate and microbiological characteristics of surgical site infection (SSI) has been performed in France.
Design. Retrospective, multicenter cohort study.
Setting. Twenty‐two university and community hospitals in France.
Patients. Each center provided data on 25 consecutive patients who underwent surgery for femoral neck fracture during the first quarter of 2005. Demographic, clinical, and follow‐up characteristics were recorded, and most patients had a follow‐up office visit or were involved in a telephone survey 1 year after surgery.
Results. These 22 centers provided data on 541 patients, 396 (73%) of whom were followed up 1 year after surgery. Of 504 (93%) patients for whom antibiotic prophylaxis was recorded, 433 (86%) received a cephalosporin. Twenty‐two patients had an SSI, for a rate of 5.6% (95% confidence interval, 3.7‐8.0). SSI was reported for 15 (6.9%) of patients who had a prosthesis placed and for 7 (3.9%) who underwent osteosynthesis (
). SSI was diagnosed a median of 30 days after surgery (interquartile range, 21‐41 days); 7 (32%) of these SSIs were superficial infections, and 15 (68%) were deep or organ‐space infections. MRSA caused 7 SSIs (32%), Pseudomonas aeruginosa caused 5 (23%), other staphylococci caused 4 (18%), and other bacteria caused 2 (9%); the etiologic pathogen was unknown in 4 cases (18%). Reoperation was performed for 14 patients with deep or organ‐space SSI, including 6 of 7 patients with MRSA SSI. The mortality rate 1 year after surgery was 20% overall but 50% among patients with SSI. In univariate analysis, only the National Nosocomial Infections Surveillance System risk index score was significantly associated with SSI (
).
Conclusions. SSI after surgery for femoral neck fracture is severe, and MRSA is the most frequently encountered etiologic pathogen. A large, multicenter prospective trial is necessary to determine whether the use of antibiotic prophylaxis effective against MRSA would decrease the SSI rate in this population.
Received February 20, 2007; accepted May 9, 2007; electronically published August 29, 2007.
Femoral neck fracture is the most common reason worldwide for the admission of elderly people to an acute orthopedic ward, with 1.3 million cases in 1990 and as many as 7‐21 million cases in 2050.1 The mortality rate associated with a femoral neck fracture is approximately 30% during the first year after surgical repair2; most deaths are due to comorbidities and postoperative complications.3 Among patients with postoperative complications, surgical site infection (SSI) can play an important role,4‐6 and antibiotic prophylaxis is strongly recommended.7
Because of the high prevalence of methicillin‐resistant Staphylococcus aureus (MRSA) carriage among elderly persons, particularly those admitted from nursing homes or long‐term care facilities in Europe or the United States,8,9 the use of cephalosporin, the recommended antibiotic prophylaxis against MRSA infection, has been challenged for this population.10 Nasal carriage of S. aureus has been demonstrated to be a major risk factor for SSI,11 and MRSA carriage was independently associated with increased mortality and increased hospital charges for patients with S. aureus SSI.12 Because the patient's MRSA carriage status is often unknown in emergency surgery, the antibiotic chosen for prophylaxis should depend on the level of MRSA colonization in the population concerned. On this topic, single‐center studies have provided conflicting results,9,13 reflecting variability from one country to another and probably also between 2 hospitals in the same country.
To our knowledge, no multicenter study has evaluated the frequency of MRSA SSI among patients undergoing any type of surgery for femoral neck fracture in settings where MRSA is highly endemic. However, 2 English multicenter studies involving patients who underwent primary hip hemiarthroplasty, the most common procedure (performed in nearly 50% of cases) for repairing femoral neck fracture, have recently been published. One, a 4‐year survey (study period, 1997‐2001) that involved 102 centers, showed an SSI rate of 5%, with MRSA infection representing 20% of the cases14; the other study, which analyzed data collected between April 2004 and December 2005 from 82 centers, showed an SSI rate of 4%, with MRSA causing nearly a third of the cases.15 In both studies, surveillance was conducted only during inpatient stays (mean duration, 15 days), with no follow‐up after discharge. However, a recent study from The Netherlands reported that nearly 30% of deep SSIs associated with repair of femoral neck fractures occurred after discharge,16 which may explain the limited number of deep infections (30%) reported in the English multicenter studies.14,15
Obviously, for all types of surgery, the real burden of SSI is represented by deep and organ‐space infections, and a 1‐year follow‐up examination is recommended to determine the associated mortality rates, morbidity rates, and costs. Therefore, we conducted a retrospective multicenter study of patients who had routine surgery performed to repair a femoral neck fracture, in which we assessed SSI rates, described antibiotic prophylaxis practices, and recorded microbiological characteristics. The medical records of enrolled patients were reviewed, and telephone surveys were conducted for patients who did not have a 1‐year follow‐up visit recorded in their medical file.
Methods
The study took place in the spring of 2006. We retrospectively studied a cohort of patients with a femoral neck fracture who were admitted to 1 of 22 French healthcare centers during the first quarter of 2005. The medical information unit at each center selected patients older than 50 years who had one the following International Classification of Diseases, Ninth Revision diagnosis codes: S720, S721, or S722. To obtain a narrow confidence interval for the rate of SSI, we estimated that more than 500 patients had to be included in the analysis. Therefore, each participating hospital was requested to include 25 consecutive patients who underwent surgery for a femoral neck fracture during the first months of 2005.
The following data were collected from the medical records of each patient and recorded on a standardized form: demographic characteristics (age, admission from home or transfer from another health care facility or nursing home, American Society of Anesthesiologists physical status classification, presence of a chronic wound, and allergy to penicillin), surgery characteristics (type of procedure [ie, hemiarthroplasty or osteosynthesis], time from admission to surgery, duration of procedure, and National Nosocomial Infections Surveillance System [NNIS] risk index score), antibiotic prophylaxis characteristics (agent, doses and/or dosage, duration before surgery, and duration after surgery), occurrence of SSI during hospitalization or after discharge, and outcome. SSI was diagnosed in accordance with Centers for Disease Control and Prevention definitions,7 and microbiological data were also recorded. If no follow‐up visit 1 year after the procedure was recorded in the medical file, a telephone‐based survey involving a standardized questionnaire was systematically performed 1 year after surgery by a staff member from the infection control team of each hospital. Information on rehospitalization status and SSI status was collected from the patient, their relatives, or primary physician or care givers if the patient was at a long‐term care facility or nursing home. If an SSI was suspected, investigations were performed in the designed healthcare institution to confirm or rule out this hypothesis, and microbiological data were collected, whenever possible.
In addition, to determine the incidence of MRSA positivity in each participating center during 2004, we collected the French national indicator available in each hospital, expressed as the number of patients with at least 1 clinical sample positive for MRSA per 1,000 patient‐days.
Data were analyzed using Epi Info software, version 6.03 (Centers for Disease Control and Prevention), and SPSS statistical software, version 12.0 (SPSS). Categorical variables were expressed as numeric values (percentages) and compared using the χ2 test or Fisher exact test, as appropriate. Continuous variables were expressed as median values (interquartile ranges [IQRs]) and were compared using the Student t test. All tests were 2 tailed. A P value of less than .05 was considered significant.
Results
Twenty‐two hospitals (14 affiliated with a university and 8 from the community) participated in the study (Table 1). The median number of acute care beds per hospital was 745 (range, 239‐1,677 beds), and the median number of cases of femoral neck fracture per center in 2004 was 158 (range, 70‐481 cases). The overall median incidence density of MRSA positivity was 0.78 cases per 1,000 patient‐days (range, 0.33‐1.5 cases).
The study included 541 patients, with 18‐27 patients enrolled per hospital. Demographic, clinical, and follow‐up characteristics of patients are summarized in Table 2. A total of 424 patients (78%) had a follow‐up visit with a surgeon 20‐50 days after surgery. One year after surgery, 434 patients (80%) were alive. Fifty‐five patients (10%) had a 1‐year follow‐up visit, and 341 patients (63%) were contacted by telephone. Of the patients followed up by telephone, interviews were conducted with the patient in 112 cases (33%), with their relatives in 117 (34%), with care givers in 58 (17%), and with others in 10 (3%); the interviewee was unknown in 44 cases (13%).
Surgical antibiotic prophylaxis was recorded for 504 patients (93%). Characteristics of the prophylaxis regimens are detailed in Table 3. Most patients (433 [86%]) received a first‐generation or second‐generation cephalosporin, which was stopped in 303 (70%) less than 24 hours after surgery and in 407 (94%) within 48 hours after surgery, as recommended by the American17 and French18 guidelines for cephalosporin prophylaxis in orthopedic surgery.
Twenty‐two of the 396 patients who were followed up had an SSI, for a rate of 5.6% (95% confidence interval [CI], 3.7‐8.0). SSIs occurred a median time of 30 days after surgery (IQR, 21‐41 days; 90th percentile, 90 days). An SSI was detected in 6.9% of patients who had a prosthesis placed (95% CI, 4.2‐10.5) and 3.9% of patients with osteosynthesis (95% CI, 2.00‐7.2) (
). The clinical and microbiological characteristics of infected patients are summarized in Table 4. Seven SSIs (32%) were due to MRSA. All infected patients received prophylaxis with a first‐generation or second‐generation cephalosporin. No MRSA SSI was observed among 49 patients (10%) who received antibiotics effective against MRSA (ie, vancomycin or gentamicin). Of the 4 SSIs without a known etiologic agent, 3 were superficial SSIs from which wound samples were not obtained, and 1 SSI yielded no bacteria on culture.
The mortality rate was significantly higher among patients with an SSI, compared with patients without an SSI (50% vs 18%; 
). In univariate analysis, only the NNIS risk index score was significantly associated with SSI: 17% of patients with a risk index score of 2 had an SSI, compared with 3% of patients with a risk index score of 0 and 4% with a risk index score of 1 (
).
Discussion
This study indicates that SSI is a frequent and severe complication of surgery for femoral neck fracture, with MRSA involved in one‐third of the SSIs. The mortality rate and prolonged duration of hospitalization were similar to findings reported in other studies.4,5,14 The SSI rate observed in this study (5.6%) is within the range of previously reported rates after surgery for femoral neck fracture (2%‐7%).11,13‐16,19,20 However, comparison of rates between studies is difficult because of variations in the type of surgery, duration of surveillance (range, 15 days to 1 year), and definition of SSI.
Lack of antibiotic prophylaxis is unlikely to explain most of the SSIs in our study, at least quantitatively. Data on antibiotic prophylaxis were available for 93% of patients. In addition, antibiotic therapy was started in more than 75% patients within 1 hour before the first incision and was discontinued in 70% within 24 hours after surgery. These findings are substantially better than those from the national American cohort for orthopedic surgery21 and those from a Canadian survey specifically dedicated to hip fractures.22
However, considering that MRSA caused 32% of the SSIs, there seems to be room to improve the use of antibiotic prophylaxis qualitatively. A recent meta‐analysis showed that although the overall efficacy of vancomycin was equivalent to that of β‐lactams for preventing SSI after cardiac surgery, vancomycin was more effective than β‐lactams for preventing SSIs caused by MRSA.23 Of note, the prevalence of MRSA carriage among the patients included in the meta‐analysis was unknown. Conversely, in a Spanish study in which a high percentage of SSIs were caused by MRSA,19 replacement of β‐lactam prophylaxis with teicoplanin prophylaxis was followed by a significant reduction in the overall SSI rate (from 5% to 2%) and the MRSA SSI rate (from 3% to 0.2%). In our study, the median incidence density of MRSA isolated from clinical samples (0.78 cases per 1,000 patient‐days) was higher than that in the French national 2004 database (0.62 cases per 1,000 patient‐days), which included 527 care facilities representing one‐third of all French hospital beds.24 This confirms the high level of MRSA colonization among patients at the participating hospitals in our study. Interestingly, no MRSA SSI was observed among patients who received an antibiotic prophylaxis regimen effective against MRSA (ie, vancomycin or gentamicin). Despite differences in the type of SSIs reported in the English multicenter studies14,15 and our study, the similar rates of MRSA SSI probably reflect similarly high levels of MRSA colonization among patients in the participating centers, emphasizing the necessity of appropriate antibiotic prophylaxis for patients undergoing femoral neck fracture surgery.
Our study has several limitations. First, because the study was retrospective, the rate of superficial SSI, which is not always recorded in patient medical records, may have been underestimated. On the other hand, all deep infections requiring subsequent intervention were probably detected, by means of either medical record review or during the follow‐up telephone survey. Second, 27% of the patients were not followed up at 1 year, either by a visit with a surgeon or by the telephone survey, which may also have underestimated the true SSI and mortality rates.
In conclusion, this study shows that MRSA is involved in one third of SSIs after surgical repair of femoral neck fractures in a country where the prevalence of MRSA carriage is high. A possible explanation of this finding is that the antibiotic prophylaxis regimen currently recommended for French patients undergoing this procedure is inappropriate. A large, multicenter prospective trial is necessary to determine whether the use of antibiotic prophylaxis effective against MRSA would decrease the SSI rate in this population.
Study Group Members
Members of the Groupe de Recherche sur l’Antibioprophylaxie en Chirurgie are as follows: A. Allaire and J. M. Carcopino (Centre Hospitalier Le Raincy‐Montfermeil), P. Y. Allouch and P. Beaufils (Centre Hospitalier de Versailles), F. Barbut and A. Sautet (Centre Hospitalier Universitaire Saint‐Antoine, Paris), P. Baune and L. Watin‐Augouard (Centre Hospitalier Foch, Suresnes), F. Espinasse and A. Lortat‐Jacob (Centre Hospitalier Universitaire Ambroise Paré, Boulogne), E. Girou and P. Hernigou (Centre Hospitalier Universitaire Henri Mondor, Creteil), F. Lemann and C. Di Montagliari (Centre Hospitalier de Pontoise), J. C. Lucet and C. Jeanrot (Centre Hospitalier Universitaire Bichat Claude‐Bernard, Paris), L. Marty and M. Blanchard (Centre Hospitalier de Lagny‐Marne la vallée), L. Marty and B. Pourjamabs (Centre Hospitalier de Bry‐sur‐Marne), L. May‐Michelangeli and P. Cottias (Centre Hospitalier d’Argenteuil), J. Merrer and F. Pauthier (Centre Hospitalier de Poissy/St. Germain), D. Vanjak and L. Rillardon (Centre Hospitalier Universitaire Beaujon, Paris), M. Cazaban and G. Asencio (Centre Hospitalier Universitaire de Nîmes), P. Berthelot and M. H. Fessy (Centre Hospitalier Universitaire de St. Etienne), R. Girard and B. Moyen (Centre Hospitalier Universitaire de Lyon), V. Merle and F. Mouilhade (Centre Hospitalier Universitaire de Rouen), P. Thibon and M. Pegoix (Centre Hospitalier Universitaire de Caen), D. Lepelletier and F. Gouin (Centre Hospitalier Universitaire de Nantes), L. S. Aho‐Glele and E. Baulot (Centre Hospitalier Universitaire de Dijon), O. Bajolet and M. Amzallag (Centre Hospitalier Universitaire de Reims), and J. M. Guerin and L. Sedel (Centre Hospitalier Universitaire Lariboisière, Paris).
Acknowledgments
Potential conflicts of interest. All authors report no conflicts of interest relevant to this article.
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Presented in part: 26th Réunion Interdisciplinaire de Chimiothérapie Anti‐infectieuse; Paris, France; December 7‐8, 2006 (Abstract 106/26).