Osteomyelitis 2

7/28/2019 Osteomyelitis 2

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Identification of the infecting organism is essential. In the early stages of the disease, particularly if there is a spiking temperature, blood cultures can often yield the organism. If acute metaphysealtenderness is present, then the organism can frequently be obtained by inserting a needle into thesite of maximum tenderness. A serrated biopsy needle is useful if subperiosteal pus is not

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encountered. If a joint is involved, then the effusion should be aspirated before joint lavage.Processing the aspirates should include the following:

Immediate Gram stain.

Inoculation of culture broth for aerobic and anaerobic cultures.

White blood cell count. If thick, purulent material is encountered, then dilution in broth occasionallyenhances the growth of organisms by decreasing the concentration of leukocytes and humeral

antibacterial factors. This is done routinely in the microbiology laboratory with fluid aspirates.

Determination of the character of the hyaluronic precipitate, the presence of fibrin clots, and anydisparity between the glucose in the aspirate and blood glucose may prove helpful, but the Gramstain, culture, and cell count are most valuable (see Chap. 3).

Differential diagnosis. Care must be taken to differentiate soft-tissue infection, or cellulitis, from aninfection occurring in a bone or joint. This is a particularly important precaution when the infectionoverlies a joint because any aspiration of a reactive sterile effusion by passing a needle through thesoft-tissue infection may create a pyarthrosis. Tenderness and swelling from unrecognized trauma

over a bone, particularly with some periosteal reaction, can present a confusing picture, but theabsence of fever and systemic signs is helpful. Nonbacterial inflammatory arthritis, including viraland toxic synovitis and rheumatoid arthritis, must be included in a differential diagnosis, but untilproved otherwise, think first of septic arthritis. Spontaneous hemorrhages in patients withhemophilia and fractures in paraplegic patients, particularly patients with meningomyelocele, arespecial situations that can confuse the picture.

Bacterial considerations (1,4,12)

In acute hematogenous osteomyelitis, Staphylococcus aureus is the most common etiologic agent inall age groups. In recent years, an increasing number of isolated strains have been found to bemethicillin resistant. In infants younger than 1 month, a diversity of other bacteria must also beconsidered. Group B streptococci and gram-negative organisms such as Escherichia coli, Proteusspecies, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Salmonella species are all suspect. Ininfants with a complicated medical history, particularly those who have had prolonged indwellingvenous catheters, extensive surgery, or intensive prior antibiotic therapy, coagulase-negativestaphylococci and rarely anaerobic organisms such as Bacteroides fragilis and fungal agents such asCandida albicans (hard to diagnose) must also be considered.

In septic arthritis and osteomyelitis among infants younger than 1 month, S. aureus is thepredominant etiologic agent. After the neonatal period and up to 4 years of age, Haemophilusinfluenzae is also a major cause of septic arthritis. In later childhood, the etiologic agents are the


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In an acute infection in which the organism is not immediately identified, the choice of therapy isdetermined by the organisms most commonly expected in the various age groups, along with theother factors previously listed. General guidelines are presented in Table 3-2.

A local instillation or continuous irrigation with an antibiotic solution is almost never indicated.

Systemic antibiotics, properly administered, achieve adequate levels in viable tissues (1,4). In manyposttraumatic conditions, delivery of local antibiotics in methyl methacrylate beads is worthwhile(21). This treatment is indicated especially when a delayed bone graft or soft-tissue muscle flap isplanned. Some favorable reports have been published about an implantable pump with a reservoirfor antibiotic (generally amikacin).

Continue antibiotics until the infection has been eliminated. A normal or declining ESR or CRP is oneof the most helpful laboratory tests to indicate control of infection.

Adjunctive treatment. Most orthopaedists believe that the healing process is aided by immobilizing

the infected area. There is disagreement over casting or splinting. Undoubtedly, however, patientsare more comfortable when the infected area is immobilized. If damage to the bone is significant,cast immobilization may be important to prevent a pathologic fracture. If damage to articularcartilage is suspected, motion of the involved joint is recommended after a brief 1- to 2-day periodof immobilization.

Surgical intervention. Appropriate antibiotic treatment instituted within the first 48 hours of acuteosteomyelitis or septic arthritis is usually satisfactory. However, early diagnosis is rarely the case. If treatment is initiated over 48 hours after onset, it is important to determine whether medicaltreatment alone is adequate. Err on the side of more aggressive operative drainage. If the patient

has been on an appropriate antibiotic for more than 24 hours without significant resolution of painand temperature, then surgical intervention is indicated.

In a bone infection, metaphyseal or subperiosteal abscesses must be drained. If metaphyseal pointtenderness is present, and there is doubt whether this represents significant metaphyseal orsubperiosteal pus, then it is safer to err on the side of a small surgical exploration or aspiration witha biopsy needle. If pus is encountered, then open surgical drainage is indicated.

Joints

In joint infections, satisfactory evacuation of pus can be achieved by needle aspiration. When the

joint is easily visible and palpable, such as with the knee joint, repeated needle aspiration is usuallyadequate to keep the joint decompressed. Aspiration should be done with a 16- to 18-gauge needle.Irrigation of the joint to ensure removal of as much cellular debris as possible is helpful (12). The hip

joint presents special problems (12). The blood supply to the femoral head is intraarticular; hence,any increase in pressure can deprive the entire femoral head of its circulation. Because hip

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joint effusions are not readily palpable, it is difficult to be certain that repeated aspirationsdecompress the joint. For this reason, most authorities believe that immediate surgical drainage of aseptic hip is indicated, and some believe that the shoulder should be treated similarly. The possibleexception is in gonococcal arthritis (22). The hip joint can be drained anteriorly between muscleplanes or posteriorly with a muscle-splitting incision. The capsule and synovium are opened anddrains are inserted.

TABLE 3-1 Antimicrobial Agents Commonly Used Initially in Acute Bone and Joint Infections

Antibiotic Usual susceptible organisms Daily dosage (IV route) Comment

Cefazolin (cephalosporins) Penicillinase-producing Staphylococcus aureus; will also treatstre ptococci, pneumococci, nonpenicillinase -producing staphylococci, and Klebsiella pneumoniae07 d: 40 mg/kg divided doses q12h

Infant: 60 mg/kg divided doses q8h

Child: 80 mg/kg divided doses q6h

Adult: 36 g divided doses of 8h A drug of choice; IV route preferred, but may be given IM. Adjustadult dosage according to blood urea nitrogen or, preferably, the creatinine clearance

Nafcillina Same as cefazolin 07 d: 50 mg/kg divided doses q12ha

7 d6 wk: 75 mg/kg divided doses q8h

6 wk3 y: 80 mg /kg divided doses q6h


Adult: 212 g divided doses of 46 h A drug of choice

Methicillin Same as cefazolin and nafcillin No longer commonly used; too many problems Monitorpatients for proteinuria: drug has occasionally been implicated in adverse renal side effects

Clindamycin S. aureus, pneumococci, streptococci (not enterococci), and many Bacteroides fragilisstrains Pediatric: 1020 mg/kg PO or IV or IM in 34 doses

Adult: 600900 mg of 68 h Considered an excellent agent for B. fragilis infections

Penicillin G (aqueous) Streptococci (not enterococci), pneumococci, gonococci, and penicillin-susceptible staphylococci 07 d: 50,000 unit/kg divided dose q12h

greater than 7 d: 75,000100,000 unit/kg IV or IM divided doses q8h


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12 yadult: 1224 million units of 46 h Useful for open fractures contaminated withbarnyard waste and for treatment of clostridia infection

Ampicillin Same as penicillin G; also Haemophilus influenzae, some strains of Escherichia coli,Proteus, and Salmonella 07 d: 50 mg/kg divided doses q12h

7 d6 wk: 75 mg/kg divided doses q8h

Infant: 100 mg/kg divided doses q6h


12 yradult: 812 g H. influenzae now shows a 10%20% ampicillin resi stance in some areas.Empirin therapy must therefore be with ceftriaxone or cefuroxime

Ceftriaxone Select gram- negative organisms or mixed infections 012 yr: 50 mg/kg once daily

12 yradult: 2 g q24h Generally reserved for resistant or mixed infectio ns

Cefuroxime Select gram-negative organisms or mixed infections greater than 3 mo-12 yr: 75 mg/kgdivided doses q8h Generally reserved for resistant or mixed infections

Ceftazidime Select gram-negative organisms including Pseudomonas or mixed infections 12yradult: 1.5 g q8h

less than 12 yr not indicated

12 yradult: 1 g q812h Same as cefuroxime

Gentamicin Gram- negative infections less than 12 yr: 67.5 mg/kg in three equal doses Agent of choice for suspected gram-negative infections

Tobramyc in 12 yradult: 35 mg/kg in three equal doses (dose adjusted based on peak andtrough levels) can be given as a single daily dose May be given either IV or IM. Renal function mustbe carefully checked, and therapy beyond 10 days must be administered cautiously because of potential nephrotoxicity and ototoxicity. May be synergistic with carbenicillin against some strains of Pseudomonas aeruginosa; also usually synergistic with penicillin against enterococci. Reduce dosageto 3 mg/kg/d as soon as clinically indicated. Follow with peak and trough serum levels if available

aSome authorities recommend that nafcillin not be used in 0- to 7-day-old infants because of poorpharmacokinetics.

From Hansen ST Jr, Ray CG. Antibiotics in orthopaedics. In: Kagan BM, ed. Antimicrobial therapy, 3rded. Philadelphia, PA: WB Saunders, 1980, with permission.

TABLE 3-2 Tentative Selection of Therapy When Organisms Are Not Immediately Identified

Situation Organisms suspected Suggested antibiotic choice


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Newborn (1 mo) Staphylococcus aureus Nafcillin plus gentamicin or tobramycin

Osteomyelitis Streptococci

Gram-negative bacteria including Escherichia coli, Klebsiella pneumoniae, Proteus group,

Pseudomonas aeruginosa

Septic arthritis S. aureus

1 mo4 yr

Osteomyelitis S. aureus Second-generation cephalosporin to cover H. influenzae

Septic arthritis Haemophilus influenzae

S. aureus

Streptococci Second-generation cephalosporin to cover H. influenzae

4 yr12 yr

Osteomyelitis

Septic arthritis S. aureus First- or second-generation cephalosporin

12 yradult

Osteomyelitis S. aureus A cephalosporin (first- or second-generation agent) or nafcillin

Septic arthritis S. aureus A cephalosporin or nafcillin (ceftriaxone if gonococcus is stronglysuspected)

Special considerations

Chronic hemolytic disorders

Osteoarthritis S. aureus A cephalosporin (second-generation if salmonella is suspected) or nafcillinuntil sensitivity results are available

Septic arthritis Pneumococci

Salmonella groupa

Infections following puncture wounds of the foot Pseudomonas aeruginosa Ceftazidime actuallyachieves better drug levels than aminoglycosides (gentamicin or tobramycin)

Infections following trauma or surgery S. aureus

Streptococci

Gram-negative organisms A first- or second-generation cephalosporin (or nafcillin) plus gentamicin

or tobramycin


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aInfections caused by Salmonella should be documented first by culture and sensitivity testingbefore empirical treatment with agents such as ampicillin (or chloramphenicol) is initiated.

From Hansen ST Jr, Ray CG. Antibiotics in orthopaedics. In: Kagan BM, ed. Antimicrobial therapy, 3rded. Philadelphia, PA: WB Saunders, 1980, with permission.

At times, the fibrin entering the joint as a transudate forms clots and isolates segments of the jointfrom decompression. Hypertrophy of synovium and adhesions may also affect the ability of thesurgeon to decompress the joint adequately. Under these circumstances, it is advisable to debridethe joint arthroscopically or with an open procedure. Joints amenable to arthroscopic lavage are theknee, shoulder, and ankle.

Chronic osteomyelitis presents a different problem from acute infection. Acute infection in theearliest phase is primarily a medical disease, with surgical techniques used as an adjunct. In chronicinfection, the primary problem is surgical removal of all dead and poorly vascularized tissue. If thisremoval is properly done under appropriate antibiotic therapy, it is possible to eradicate most sitesof chronic osteomyelitis. The operation must be carefully planned because it often involvessignificant removal of bone and surrounding tissues. In the case of chronic joint infections, it maymean complete resection of the joint with the creation of a pseudarthrosis or an arthrodesis.Rotational muscle flaps or free-tissue transfer may be required to cover areas of viable but poorlycovered bone. Intravenous and oral antibiotics serve as valuable adjuncts. Patient quality of life canbe profoundly impacted by chronic osteomyelitis (23); treatment leading to resolution of theinfection does improve this impact.

Gas gangrene

Gas gangrene can be a fatal process. Prevention can be achieved by thorough debridement andremoval of all devitalized tissue, delayed wound closure when in doubt, and antibiotic treatment asrecommended previously.

Clostridium perfringens infections carry a 65% overall mortality rate, which increases to 75% ininfants and elderly patients. The diagnosis should be suspected when the patient is pale, weak,

perspiring, and more tachycardiac than the degree of fever warrants. The patient frequentlycomplains of severe pain. Mental confusion and gas in the tissues are late signs, as are thecharacteristic mousy odor, jaundice, oliguria, and shock.

Other gas-producing species in addition to C. perfringens (ten isolated toxins), include E. coli,Enterobacter aerogenes, anaerobic streptococci, B. fragilis, and K. pneumoniae. Antitoxin does notappear to help much because it is neutralized as rapidly as it reaches muscle. Treatment consists of debridement and high doses of antibiotics. Penicillin is usually the best for the C. perfringens group;it should be given in amounts of 20 to 50 million units/day. Clindamycin or metronidazole are goodalternative antibiotics in patients who are allergic to penicillin. Some clostridia are resistant to

clindamycin, making it necessary to check sensitivities carefully. Hyperbaric oxygen is only an adjunct


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to surgery. Its use allows the surgeon to save more tissue than might otherwise be possible, and itdoes lower the mortality rate slightly.

Although exceedingly uncommon, group A streptococcal myonecrosis can have a similar course andresults in death in a high percentage of cases. It must be treated with aggressive surgical

debridement or amputation in addition to appropriate antibiotic therapy. Toxic shock syndrome hasalso been noted in orthopaedic patients and is caused by unique staphylococcal strains with unusualphage types. Toxic shock syndrome is also a surgical condition, but it carries a more favorableprognosis. Necrotizing fasciitis can be caused by several bacterial types (most commonly group Astreptococcus) and often requires debridement combined with appropriate antibiotic therapy.Infectious disease consultation is indicated for each of these infectious conditions.

Osteomyelitis 2

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