Commentary:    The diagnostic imaging of osteomyelitis (bone infection) can require the combination of diverse imaging techniques for an accurate diagnosis and clinical staging .(1)   Conventional radiography should always be the first imaging modality to start with, as it provides an overview of the anatomy and the pathologic conditions of the bone and soft tissues of the region of interest.  However, since the specificity of plain x-rays for detection is higher than its sensitivity, other, more reliable methods of imaging are necessary.(2 – 4)   Ultra-sonography is most useful in the diagnosis of fluid collections, periosteal involvement, and surrounding soft tissue abnormalities and may provide guidance for diagnostic or therapeutic aspiration, drainage and/or tissue biopsy. Computed tomography (CT) scans can be a useful method to detect early osseous erosion and to document the presence of sequestra, cloacae, foreign bodies, or gas formation; nevertheless, they are generally is less sensitive than other modalities for the detection of osteomyelitis.(3)   Magnetic resonance imaging (MRI) is the most sensitive and most specific imaging modality for the detection of infection in bone (Sens /Spec = 82%-100%/ 75%-95%), provides superb anatomic detail and gives more accurate information of the extent of the infectious process in bone and soft tissue.(3 -5)    Although nuclear medicine imaging (technetium-99 bone scans and Indium-111 white blood cell scans) is particularly sensitive in identifying multifocal osseous involvement, they are rather nonspecific.(6)   

Since no one study is able to definitively confirm the presence of absence of infection, cross-sectional imaging modalities such as CT and MR scanning are now considered the gold standard in diagnosing osteomyelitis, giving excellent anatomic delineation of the infected area and the surrounding soft tissue envelope.   In our protocols, all methods of used, selectively: (7) plain radiographs  to reveal internal hardware, axial alignment, fracture patterns and instability; nuclear scans  to correlate  cellular activity with radiographic change and assess for  poly-osseous disease;  CT scans to delineate sequestra, cloacae, bone volumes, and the extent of fracture healing (union vs non-union);  MRI and PET/CT scans to define the zone of injury/inflammation, disclose skip-lesions and highlight necrotic foci.   

Bibliography:  (1) Haas DW, McAndrew MP. Bacterial osteomyelitis in adults: evolving considerations in diagnosis and treatment. Am J Med, l996; 101:550-561.  (2)  Pineda C, Espinosa R, Pena A. Radiographic imaging in osteomyelitis: the role of plain radiography, computed tomography, ultrasonography, magnetic resonance imaging, and scintigraphy.   Semin Plast Surg, 2009 May; 23(2):80-9.  (3) Termaat MF, Raijmakers PG, Scholtein HJ et al. The accuracy of diagnostic imaging for the assessment of chronic osteomyelitis: a systemic review and meta-analysis. J Bone Joint Surg Am, 2005; 87:2464-2471.  (4) Mahnken AH, Bucker A, Adam G, Gunther RW. MRI of osteomyelitis: sensitivity and specificity of STIR sequences in comparison with contrast-enhanced T1 spin echo sequences. RöFo, 2000; 172” 1016-1019.  (5) Littenerg B, Mushlin AL. Technetium bone scanning in the diagnosis of osteomyelitis: a meta-analysis of test performance. J Gen Intern Med, l992; 7:158-163.  (6) Cierny III, G., Pennick, JJ, Mader, JT, A Clinical Staging System for Adult Osteomyelitis, J. Clinical Orthopaedics and Related Research, Number 414, pp 7-24, September 2003 .  (7)  Cierny G, DiPasquale D. Adult Osteomyelitis. Chapter 16 in Orthopaedic Knowledge Update : Musculoskeletal Infection. Amer. Acad. Orthop. Surg, Rosemont, IL, 2009. pp 135-155.

 6/22/2010:   The Hoka Hey Challenge (race) is on! 

Eric made it to the first check point in 25^th place.   He remains salty (the heat!) and unscathed, despite a 4-bike accident along the way.   They’re now in Mississippi, heading north —– hopefully out of that brutal heat.   GC

Article review:   Bhavan KP, Marschall J, Olsen MA, et al:  The Epidemiology of hematogenous vertebral osteomyelitis: a cohort study in a tertiary care hospital.  BMC Infectious Diseases, 2010: 10: 158doi: 10.1186/1471-2334-10-158  (Published 7-7-2010).

Dr. Cierny’s comments:  this article describes the epidemiology and early management of hematogenous vertebral osteomyelitis (anatomic types I and IV) in 70 patients over a 2-year period at Barnes Hospital in Missouri (a retrospective, cohort review).  A microbiological diagnosis was made in only two-thirds the cases.  S. aureus was the most common causative organism.

Results – The mean age was 59.7 years with 54% male. Predisposing factors included: B-hosts with diabetes (43%) or renal insufficiency (24%); in the 30 days prior to admission, an indwelling catheter (30%), bacteremia (19%) or skin/soft tissue infection (17%).  Back pain was the most common symptom (87%), followed by weakness (56%) and fever (46%); seven patients presented with paraplegia.  48% had a normal WBC but 95-98% had either an elevated ESR or CRP. 

The lumbar spine was the most common anatomic location (47%): thoracic (29%); cervical (24%).  Among the 46 (66%) patients with a microbiological diagnosis, the most common organisms were MSSA (33%) and MRSA (22%).  Among the 44 (63%) patients who had a diagnostic biopsy, open biopsy was more likely to result in pathogen recovery [14 (93%) of 15 with open biopsy vs. 14 (48%) of 29 with needle biopsy; p=0.003].   Surgery was required during the initial hospitalization in 23% of patients: decompression laminectomy 14%), laminectomy /fusion (7%) and corporectomy (1%).  Treatment outcomes were not included.  

Stone Step Alaska; the HOKA HEY finish

Well folks, it’s about a month to the start of the Hoka Hey challenge and our main man, Eric, is now back in Anchorage after spending last week driving the 1000 miles downrange from the finish line (pictured at left) ;  burying 6 gallon gas cans every 170 miles all along the way and marking them with a GPS coordinate kilometer marker and land mark notation….WHEW!!!  No surprise, he’s working in his Super Duty 351M w/ C6 trans Bronc………., a true thoroughbred, guaranteed to pass up everything on the road but the gas pump. According to Eric, it has “studs on mains,heads, roller cam , roller rockers, MSD ignition,400plus hp, Kevlar bands in trans. Shift kit custom ground camshaft …. you name it. “.

He’s seen grizzlies, porcupine caribou, Alaskan cowgirls, a whole lot of beauty and more to come ……. the Challenge is just a month away.    Hoka Hey, Eric !

……….. www.Vitals.com

 Dr. George Cierny is an orthopaedic surgeon .  He has 36 years as a doctor and is based out of REOrthopaedics located at 7910 Frost Street; Ste 120, San Diego, CA.   Dr. Cierny is affilitated with a 4-star hospital, has received a fellowship, and attended a 4-star medical school.  Dr. George Cierny has additional knowledge and expertise in areas of bone transplantation, bone marrow inflammation (osteomyelitis), fracture fixation, tibial fractures, musculoskeletal tumors, un-united fractures and Methods of Ilizarov.  He has 126 research publications.   His overall average patient rating is four out of four stars, with an overall rating of “Excellent”.  You may also find the doctor’s name written as Dr. George Cierny III, MD.

Meet Eric Wickre (the original, Alaskan Viking Cowboy), treated at our center December 2008 for Stage IA osteomyelitis of his left tibia, a con-sequence of an open fracture suffered in 1981.   His (and others’) entire medical case portfolio will be posted  at http://www.osteomyelitis.com/html/news.html#featured-case .  After successful treatment at our treatment center in  San Diego, Eric is now back to his rough-and-ready cowboy ways, having just been selected to be one of 1000 motorcyclists from around the globe to compete in The Hoka Hey Motorcycle Challenge —– also known as the “Iditarod of Harley Davidson, 2010”.

CLICK TO ENLARGE

The Challenge is a grueling, 7,000 mile race from Key West, FL to the Kenai Peninsula, Alaska where “winner takes all” …one half million dollarsin Alaskan gold!  It starts June 20th and ends in Homer, AK on July 4th.  The secret route will initially head 1,000 miles into Mississippi. There, riders will get a map for the next leg of the ride: traveling the back roads, highways and byways; enduring hail storms, heat waves and scorpions; sleeping along side their bikes every night for the entire journey.

Join us as we follow Eric’s epic journey through the Americas on  OSTEOMYELITIS  BLOG.                                           Good luck, Eric!!

George Cierny, MD; REOrthopaedics in San Diego

In acute pediatric osteomyelitis  and osteomyelitis of the spine (verbetral osteomyelitis; sacroiliitis) in all ages,  surgery is not always necessary to affect cure.  In other forms of acute osteomyelitis  (infection following open fracture; surgical site infections following trauma or reconstructive surgery) and nearly all forms of the chronic disease, treatment will have to combine various aspects of surgery (with antibiotics) to result in cure .
The treatment of a refractory (chronic) osteomyelitis is governed by its pathophysiolgy —– it is a ‘biofilm disease’.    Unlike the mobile (planktonic), environmentally sensitive microbes found in an acute infection, chronic wound pathogens are sessile and resilient, transformed into colony-forming units by environmental triggers (quorum-sensing) and the successful attachment to ‘unprotected’ surfaces within the wound (inert materials; non-viable tissues or organisms, etc.).    Thereafter, individual cells become colony-forming units that mature (2-4 weeks) to secrete and maintain a mucopolysaccharide “slime” that protects them from host defenses and the penetration of most antimicrobial agents .   To cure this biofilm infection, a LIVE, CLEAN WOUND is paramount: the biofilm-colony its attachment surfaces must be completely excised.

The type of surgery will depend on the duration of the infection (acute or chronic), the contents of the wound (extent of necrosis; substrate surfaces), the anatomic site, the health and well-being (impairment) of the host, and the experience of the healthcare team.

However, surgery, as a form of treatment, is not available to everyone. Patients who are very ill may not be able to endure the extensive surgery and recovery. In these cases, doctors may use antibiotics for long periods in an attempt to suppress (rather than cure) the infection.  Then, if the infection persists and, again, threatens the patient’s well-being, lesser morbid procedures, such as amputation of all or part of an infected limb, may be necessary.  

Surgical treatment options  – Drain the infected area: Opening up the area around the infected bone allows the surgeon to drain any pus or fluid that has accumulated in response to the infection.  This is usually applied in the acute setting to decrease strain on host defenses and amplify the effects of antibiotics.  Remove the attached, biofilm-colony:  In a procedure called debridement, the surgeon removes the diseased bone and tissue. In some cases, foreign objects, such as surgical plates or screws, used in previous surgeries, may also be removed. Restore the bone and soft-tissue envelope: Your surgeon may fill any empty space left by the debridement procedure with a piece of bone or other tissue, such as skin or muscle, from another part of your body. Sometimes temporary fillers containing antibiotics (antibiotic depots) are placed in the space until the infection is cured and the patient is healthy enough to undergo a definitive reconstruction. Bone grafts and tissue flaps help the body recruit new blood vessels into the site and form new bone.  Protect against instability: Immediately following debridement, the surgeon may use an external fixatation device (external fixator) to hold and protect the bone from further injury.  This method limits the amount of implanted, foreign material (metal) in the still-contaminated wound by attaching thin wires or pins (that pass through the limb) to a frame positioned around the limb (outside the skin).  The fixator can be the only method used throughout treatment or, after a course of local antibiotic therapy, replaced with internal methods of fixation such as metal plates, rods or screws.

PREVENTING HOSPITAL ACQUIRED INFECTIONS:   The translation of basic epidemiologic evidence into successful prevention has led to several successes in hospital-acquired infection prevention research over the past decade.  First is the use of alcohol-based hand rubs in clinical practice.

I.  Hand Hygiene:  Before the past decade, the major method of decontamination of the hands was the use of soap and water. The limitations of this procedure included the time it took to do, the number of sinks and the location of sinks in the hospital defined the optimal adherence to policy, and repeat use of detergents can be very irritating to the skin.

In 2002, the Centers for Disease Control and Prevention [CDC] through the Healthcare and Infection Control Practices Advisory Committee firmly established alcohol-based hand rubs at the center of hand hygiene practices, recommending them for routine decontamination of hands in all clinical situations except when the hands are visibly soiled.    Application of the rub takes seconds, the compounds are non-irritating and the dispensers are small, inexpensive and accessible wherever needed.  By 2008 84% of all US hospitals surveyed indicated that they had adopted alcohol-based hand rub and number of studies have shown dramatic increases in adherence to hand hygiene.  - Mody L, et al; Adoption of Alcohol-Based Handrub by United States Hospitals: a National Survey. Infect Control Hosp Epidemiol., 2008; 29:1177-1180.

II. Central Line catheter infections:  In the 2000s, there were 2 separate reports of large collaborative regional demonstration projects that focused on improved implementation of existing recommendations to prevent central line-associated blood stream infections (CLABSI) among patients in intensive care units (ICUs), first in southwestern Pennsylvania (2005) and then in Michigan (2006). Both studies demonstrated ~70% reductions in CLABSI rates across a wide variety of facility and ICU types, suggesting that the preventable fraction of these infections was perhaps much larger than we had originally thought.  The protocol was a 5-step process:  1) hand hygiene by the person inserting the device.  2) maximal barrier precautions.  3) chlorhexidine gluconate for antisepsis applied to the site of the insertion.  4) avoidance of femoral central line insertion.  5) removal of the central line as soon as possible /when no longer needed.

The results of these 2 studies have changed expectations of CLABSI prevention programs. The earlier single-center reports were viewed by many as somehow aberrant, the result of special circumstances and/or resources that could exist only in those particular, reporting facilities. These regional studies demonstrated that better implementation of existing recommendations can have a major impact across a wide spectrum of hospital settings —– dramatic success was possible, and not just under special circumstances.

III. DECOLONIZATION OF PATIENTS: Another innovative advance is the role of “source control” in preventing infection, particularly with the use of chlorhexidine bathing of patients. Based on data suggesting that colonization of a patient’s skin is an important source of spread for epidemiologic imported bacteria, it was hypothesized that daily bathing with a skin antiseptic (chlorhexidine gluconate) would decrease the burden of the patient’s skin contamination, indirectly decrease contamination in the environment, decrease transmission by healthcare worker, and play a role in decreased transmission of resistant pathogens and the incidence of both surgical site infections and CLABSI.  Today, data strongly suggest that daily chlorhexidine bathing can significantly reduce contamination of the patient’s skin, the environment, and healthcare workers’ hands, and an impact on methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococcus (VRE) acquisition has been documented.  - Barta R, Cooper BS, Whitely C, Patel AK, Wyncoll D, Edgeworth JD.  Efficacy and limitation of a chlorhexidine-based decolonization strategy in preventing transmission of methicillin-resistant Staphylococcus aureus in an intensive care unit. Clin Infect Dis. 2010;50:210-217.

Discussion: One area of controversy is the role of active surveillance, or what the value is of actively screening patients for MRSA.  . Most of the studies done in the past were typically small, single-institution studies, and often with quasi-experimental, pre- vs post- design. The results from those studies leave the conclusions open to interpretation and raise the issues of potential confounding or bias. With that said, even more rigorously done, recent studies have come to different conclusions.   Clearly, more work needs to be done.  - Harbarth S, Fankhauser C, Schrenzel J, et al. Universal screening for methicillin-resistant Staphylococcus aureus at hospital admission and nosocomial infection in surgical patients. JAMA. 2008;299:1149-1157. CONCLUSION: A universal, rapid MRSA admission screening strategy did not reduce nosocomial MRSA infection in a surgical department with endemic MRSA prevalence but relatively low rates of MRSA infection. – Robicsek A, Beaumont JL, Paule SM, et al. Universal surveillance for methicillin-resistant Staphylococcus aureus in 3 affiliated hospitals. Ann Intern Med. 2008;148:409-418.  CONCLUSION: The introduction of universal admission surveillance for MRSA was associated with a large reduction in MRSA disease during admission and 30 days after discharge.

IV. Catheter-Associated Urinary Tract Infections:  Wald and colleagues  looked at catheter-associated UTIs [urinary tract infections] — morbidity and mortality associated with the device.  There is good evidence that getting the catheter out by postoperative day 2 makes a real difference. – Wald HL, Ma A, Bratzler DW, Kramer AM. Indwelling urinary catheter use in the postoperative period: analysis of the national surgical infection prevention project data. Arch Surg. 2008;143:551-557.

IF YOU HAVE DIABETES, A JOINT REPLACEMENT OR ARTHRITIS…. YOU’RE AT INCREASED  RISK FOR A BONE INFECTION?  George Cierny, MD, and Doreen DiPasquale, MD; *BottomLine Health, 2010; Vol 24(3), pp9-11

* Bottom Line/Health interviewed George Cierny, MD, and Doreen DiPasquale, MD, physician-partners at REOrthopaedics in San Diego.  Dr. Cierny is an international lecturer in orthopedic surgery who has published more than 100 scien­tific papers and/or book chapters in the field of musculoskeletal pathology and infection. Dr.Di­Pasquale, an orthopedic-trauma surgeon, is former resi­dency program director at George Washington University in Washington, DC, and National Na­val Medical Center in Bethesda, Maryland.

—————- When most people think of bone problems, broken bones and osteoporosis (re­duced bone density and strength) come to mind. But our bones also can be the site of infections that can sometimes go unrecognized for months or even years. This is especially the case if the only symptoms of bone infection (a condition known as osteo­myelitis) are ones that are commonly mis­taken for common health problems, such as ordinary back pain or fa­tigue. What you need to know…

ARE YOU AT RISK? Older adults (age 70 and older), people with diabetes or arthritis and anyone with a weakened immune sys­tem (due to chronic disease, such as cancer, for example) are among those at greatest risk for osteo­myelitis.   Anyone who has an artificial joint (such as a total hip replacement or total knee replacement) or metal implants attached to a bone also is at increased risk for osteomyelitis and should discuss the use of anti­biotics before any type of surgery, including routine dental and oral surgery. Bacteria in the mouth can enter the bloodstream and cause a bone infection.

TYPES OF BONE INFECTIONS: Before the advent of joint-­replacement surgery, most bone in­fections were caused by injuries that expose the bone to bacteria in the en­vironment (such as those caused by a car accident) or a broken bone…or an infection elsewhere in the body, such as pneumonia or a urinary tract infection, that spreads to the bone through the bloodstream. Now: About half the cases of osteo­myelitis are complications of surgery in which large metal implants are used to stabilize or replace bones and joints (such as in the hip or knee).   

Osteomyelitis is divided into three main categories, depending on the origin of the infection… Blood-born osteomyelitis occurs when bacteria that originate else­where in the body migrate to and in­fect bone. People with osteoarthritis or rheumatoid arthritis are prone to blood-borne infections in their af­fected joints due to injury to cells in the lining of the joints that normally prevent bacteria from entering the bloodstream. Contiguous-focus osteomyelitis oc­curs when organisms— usually bacte­ria, but at times fungal species —infect bone tissue. These cases usually occur in people with diabetes, who will often de­velop pressure sores on the soles of their feet or ­buttocks due to poor cir­culation and impaired immunity.   Post-traumatic osteomyelitis: Trau­ma or surgery to a bone and/or sur­rounding tissue can open the area to bacteria and other microbes. The use of prosthetic joints, surgical screws, pins or plates also makes it easier for bacteria to enter and in­fect the bone.  Important: any of the three types of bone infections described above can lead to chronic osteomyelitis, an initially low-grade infection that can persist for months or even years with few or no symptoms. Eventu­ally it gets severe enough to liter­ally destroy bone. Left untreated, the affected bone may have to be amputated.

DIFFICULT TO DIAGNOSE – When osteomyelitis first develops (acute osteomyelitis), the symptoms —such as pain, swelling and tender­ness—are usually the same as those caused by other infections. If the initial infection is subtle (low-grade) or doesn’t resolve completely with treatment, it can result in chronic osteomyelitis. In this case, you may have no symptoms or symp-toms that are not specific.  For example, some one who has had surgery might blame discomfort on delayed recovery, not realizing what they have a bone infection.  A surprising finding: When we stud­ied the histories of more than 2,000 osteomyelitis patients, we found that most of those with chronic infections had relatively little pain from the in­fection itself. About 28% of those who required surgery for infection had normal white blood cell counts—suggesting that, over time, the body adjusts to lingering infections.  If a doctor suspects that you may have osteomyelitis because of chron­ic pain…swelling…possibly fever…fatigue…or other symptoms, he/she will usually order special laboratory tests that detect the formation of an­tibodies and/or cellular signaling compounds. If the results indicate the presence of infection, he/she may then order an X-ray, a magnetic reso­nance imaging (MRI) scan or a nuclear scan(bone scan). These and other imaging tests can readily detect damaged­ bone tissue and re­veal the presence of infection.

BEST TREATMENT OPTIONS   About 60% to 70% of people with acute osteomyelitis can be cured with antibiotics (or anti­fungal agents, if a fungal infection is present) if treat­ment begins early enough to prevent the infection from becoming chronic. In these cases, patients exhibit symp­toms…test positive for infection…and readily respond to drug treatments. Most patients can be cured with a four- to six-week course of antibiotics. Fungal infections are more resistant to treatment—antifungal drugs may be needed for several months.

For chronic osteomyelitis, surgical debridement (the removal of dam­aged tissue and bone using such in­struments as a scalpel, dental burrs and/or chisels) usually is necessary. Reasons: dam­aged bone can lose its blood supply, die and remain in the body without living cells or circu­lation. Such “dead bone” is invulnerable to the effects of antibiotics and provides safe haven to organisms attached to its surface.  To address this, the surgeon, after debridement, may insert a slow-release antibiotic depot (antibiotic beads) that release antibiotic for up to a month. This approach can increase drug concentrations up to 100 times more than oral antibiotic therapy and help to eliminate the sequestered microorganisms.   Using these and other innovations, the REOrthopaedics  center in Southern California now posts an overall success rate of 95%.    Nevertheless,  up to 6% of patients who are otherwise healthy may require a second or even a third operation to completely cure the infec­tion;  and, iIn patients suffering from diabetes or oth­er disorders affecting wound healing (compromised hosts) , the percentage may be as high as 25%.    To improve your chances of a full recovery from chronic osteomyeli­tis following treatment: eat well, maintain healthy blood sugar levels, stay active after treat­ment (to promote blood circulation, prevent blood clots and help main­tain an appetite) and don’t use to­bacco products.

_{Copyright © 2009 by Boardroom Inc., 281 Tresser Blvd., Stamford, Connecticut 06901-3229.                          www.BottomLineSecrets.com}

Article:

EARLIER DEBRIDEMENT AND ANTIBIOTIC ADMINISTRATION DECREASE INFECTION:   Maj. Brown KV, Walker JA, Cortz DS et al.  J. Surg. Ortho.p Advances, 2010;  Vol 19(1): 18-22.    Goals: ascertain the effects of 1) earlier debridement (debridement alone or in combination with locally delivered antibiotics) and 2) the use of local antibiotic-depots on bacterial load following contamination of open fractures.  A contaminated, critical sized, rat femur, defect model was used.  Results: early debridement and early administration of local antibiotics resulted in lower bacterial loads in bone.  There was a significant increase in the rate of infection between 2 and 6 hours and a further increase between 6 and 24 hours when treatment was limited to debridement (alone) as well as when debridement was combined with local antibiotics.  Treatment with local antibiotics resulted in a significant reduction in infection at 2 and 6 h hours compared to debridement, alone.          

Dr. Cierny’S  comments:  Surgical antibiotic prophylaxis refers to the administration of antibiotics to patients without clinical evidence of infection in the operative field.  The objectives of prophylaxis are to prevent naturally occurring organisms in one site from proliferation in a normally sterile site; to prevent organisms contaminating a normally sterile site from producing diseases; and to prevent infection by exogenous organism.  In order to achieve this goal, the surgeon must recognize the high-risk patient, operate in an effective and efficient manner, and keep abreast of local hospital flora and sensitivity patterns.  Antibiotic prophylaxis is indicated in the surgical patient when there is an unacceptable incidence of infection or when the incidence of infection is low but such an infection would be devastating or lethal.  Prophylaxis accounts for approximately 30% of the antibiotic administration on surgical services in the United States.  In most instances, these antibiotics are not justified and may lead to multiple problems, including the selection of resistant organisms.  However, when the theory and practice of surgical antibiotic prophylaxis are correctly applied, the patient benefits.

            The pathogenesis of a surgical wound infection lends itself to a rational approach to surgical antibiotic prophylaxis.  The first step is bacterial contamination of surgically manipulated tissue.  Bacterial contamination, a component of every surgical wound, arises from two sources: exogenous contamination from the operative theater; or endogenous contamination from the skin, respiratory, or urogenital tracts of the patient.  Whether or not the bacterial contamination produces infection depends on the number and the virulence of the organisms, the adequacy of the patient’s defenses, and the condition of the disrupted (injured) tissue.

The first response to surgical injury and subsequent bacterial contamination is local inflammation.  Small vessels leak plasma, and leukocytes emerge in response to local leukotactic substances, migrate into the contaminated area, and begin phagocytosis.  Inflammation continues, wound induration develops, local macrophages and vascular components proliferate, and the stage is set for wound maturation.  The early local inflammatory phase is virtually identical to what is called the “decisive period” as defined by Burke (see below).  If inflammation is not appropriate and phagocytosis is overwhelmed, the patient will develop an infection.  Necrosis, ischemia, hemorrhage, and the presence of debris and/or foreign bodies impair the local host-defense mechanisms and decrease the number of bacterial organisms required to cure infection. The overall integrity of the host is important because a compromised host is at increased risk for infection. 

If an appropriate antimicrobial agent is present in adequate concentrations, a wound infection in the contaminated tissue is less likely.  The antibiotics must be in the tissues during the early, “decisive period” to effectively present bacterial invasion and proliferation.  If given later, when the bacteria are well established, the antibiotics will have no prophylactic effect.  Similarly, if the compromised host can be protected with prophylactic antibiotics until the local defense mechanisms are capable of eradication local bacterial invasion, the subsequent stages of wound healing can proceed normally.

The concept of a “decisive period” was first recognized when Burke (1961) administered an anti-Staphylococcal antibiotic one to three hours after inoculation of S. aureus into the dermis of a guinea pig model …. early antibiotic administration would reduce the size of the lesion.  However, if the anti-Staphylococcal antibiotic was given three hours after dermal infection, the antibiotic was less effective in reducing the size of the lesion.  Clinical studies have subsequently demonstrated, conclusively,  that antibiotic administered one hour before the surgery significantly decreases the incidence of postoperative infection when compared to placebo.  However, if the antibiotic is begun one to four hours after the operation, there is no reduction in the postoperative infection rate.

The correlation between the frequency of infection and the density of microorganisms present in a homogenized sample taken from the wound closure site has been established. Since it is not immediately possible to determine the microbial density of every surgical wound, a system for categorizing a surgical wound based on the probability and degree of microbiologic contamination has been developed.  The accuracy with which this clinical classification predicts the incidence of wound infection for general and orthopaedic surgery is well established.

Clean surgical procedures account for 75% of all operations.  These procedures are performed under ideal and sterile operating room conditions.  The procedures are generally elective and no entry is made into the oropharyngeal cavity or the lumen of the respiratory, alimentary, or genitourinary tract.  Inflammation is not encountered and no break in surgical technique occurs.  The incidence of wound infection in clean procures is less than 5%.

Clean-contaminated surgical procedures involve entry into the oropharyngeal cavity or the lumen of the respiratory, alimentary, or genitourinary tract without significant contamination from these sites.  Clean wounds are included in this category when there is a major break in the surgical technique. Clean- contaminated surgical procures occur in approximately 15% of all surgical operations and wound infection is reported in approximately 10% of these cases.  Since the mucosa of the oropharyngeal , respiratory, alimentary and genitourinary tracts harbor diffuse and dense microbiologic flora, some contamination of the wound is e inevitable.  Antibiotic prophylaxis is indicated in these patients and should be appropriately tailored to the flora expected in the particular region of surgery.  Clean surgery on a compromised host ( ) or transoral fixation of lesions involving the first and second cervical vertebra are examples of clean-contaminated procedures.

Contaminated-dirty surgery includes surgery through traumatic wounds, operative procedures with a major break in sterile technique and operations into a site of active infection.  The infection rate is between 20% and 40% in surgery involving these patients.  Antibiotic “prophylaxis”, in these circumstances, is directed at the prevention of infection in the soft-tissue planes and wounds previously uncontaminated by bacteria.  As such, the antibiotic(s) used  may be modified by the preoperative Gram stain or culture results stemming from biopsies of exposed granulating surfaces and/or wounds, themselves.  Surgery of open fractures is an example of contaminated-dirty surgery.  The risk of subsequent infection increases with the amount of tissue devitalization, the extent of contamination and the systemic compromise of the host. 

Final comment:  There are few controlled trials to scientifically support a practice mandating emergency-debridement of all open fractures  (< 6hrs). However, it is in agreement that 1) all open fractures require immediate, systemic antibiotic coverage and 2) that additional coverage with a local antibiotic-depot (antibiotic beads ) will reduce the incidence even further when treating  severe open injuries (Seligson D, Henry SL) when used in conjunction with systemic coverage.   BEST PRACTICE:  all methods of treatment should impact outcomes within the  “decisive period”:  immediate antibiotic coverage; host resuscitation; the earliest possible debridement; avoidance of large surgical implants; adequate (and safe) methods of stabilization; soft-tissue coverage within 7 days of injury –  Primary_versus_Delayed_Soft_Tissue_Coverage_for.8 .