Infection of Bones & Joints

Infection of Bone & Joints

infectionThis lecture is about musculoskeletal infections. A specific infection could have a specific infecting agent, a specific presentation, or a specific treatment. I am going to try to present the most common types of infections that probably has a specific thing about it. The majority of orthopedic surgical site infections (SSI) are caused by Staph Aureus.

Chronic Paronychia

chChronic Paronychia. This is a fungal infection (Candida albicans). It involves an infection of the nail fold. It is common in diabetics. It does not respond to antibiotics. It occurs in people who work with water such as bartenders or dishwashers. There is really no abscess, but the area around the nail is red, tender, and swollen. It can affect multiple fingers. It should be treated with topical antifungals such as miconazole. In severe resistant cases, marsupialization should be done.

Herpetic Whitlow

herpHerpetic Whitlow occurs from the herpes simplex virus. It is a self-limited disease. It is seen in dentists, respiratory therapists, or anesthesiologists, and it can also affect toddlers. It affects some vesicles on the finger, and it will have inflammation or redness at the base of the vesicle. There is clear fluid in the vesicle, and the gram stain will be negative. You should use the Tzanck test, and the treatment is Aciclovir. Surgery is not needed.

Osteomyelitis

Sickle Cell Disease can be associated with Salmonella Osteomyelitis.

nailPseudomonas Aeruginosa is commonly associated with foot punctures in children and IV drug abusers. Pseudomonas Aeruginosa infection is responsible for the majority of the osteomyelitis following nail puncture through shoes. Pseudomonas is the most characteristic cause of this infection. Treatment is incision and drainage (I&D). You must remove the foreign bodies inside and give the patient antibiotics.

With chronic osteomyelitis and draining sinus for years, rule out squamous cell carcinoma. Biopsy the sinus and do wide excision.

With a diabetic patient with draining sinus for several months, you don’t know if it is a Charcot joint or if it is an osteomyelitis (the look alike on x-ray), the MRI will not be helpful. These patients have plantar ulcer of the forefoot. You need to probe the ulcer, and if the probe goes down to the bone, it is probably osteomyelitis, and this will require debridement.

Fungal infections occur in sick, malnourished old people with chronic illness. They can also occur in people who are on IV antibiotics for a long time and may be getting parenteral nutrition (PN).

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Erysipelas

Erysipelas is caused by Group A Beta Hemolytic Streptococcus. It affects the superficial layers of the skin. It has geographic demarcation or distribution over the extremity or over the face. Treatment is antibiotics.

Necrotizing Fasciitis

Necrotizing Fasciitis is polymicrobial, but there is a Group A Streptococcus involved. It is a rapidly progressive infection which affects the fascia early, and then the toxins liquefy the tissues underneath. The edema and pain is more than what appears at the surface of the skin. It looks like cellulitis, but it is really not cellulitis. necrUnderneath the fascia can be a really terrible infection which can involve all the tissues, including the muscles, without even having a smoking gun mark on the skin surface. The blisters and the bullae are late. If you are in doubt about the presence of cellulitis or necrotizing fasciitis, do a biopsy by doing an incision down to the fascia and see if the fascia is involved (if the fascia is involved, then you have a problem). If the fascia and the muscles are involved, then you have necrotizing fasciitis. Hepatitis C is an associated risk factor for necrotizing fasciitis, and the prognosis of these patients are worse. Treatment for necrotizing fasciitis is emergency aggressive debridement. The mortality rate is high, up to 25%, and it depends on early diagnosis (mortality improves by early diagnosis and treatment). Necrotizing fasciitis is then treated with antibiotics.

Gas Gangrene

gasGas Gangrene occurs due to Clostridium perfringens (C. perfringens). It is an anaerobic gram-positive bacilli. It is almost like every bad infection is due to gram-positive bacteria. There will be linear streaks of gas in the tissues. Gas gangrene is treated by wide debridement and leaving the wound open. It is then treated with antibiotics. Penicillin G and clindamycin are usually given.

C. Diff

There is a difference between Clostridium perfringens (C. perfringens) and Clostridium difficile. Clostrodium difficile causes C. Diff (clostridium difficile colitis). Clostridium Difficile Colitis can be caused by antibiotics, especially clindamycin. It is characterized by unexplained post-operative fever, leukocytosis, or watery diarrhea. C. diff is treated by oral Metronidazole (flagyl).

Human, Dog, & Cat Bites

Human bites can cause Eikenella Corrodens. Treatment is Augmentin. If the wound goes to a joint, you have to clean and debride the joint in the operating room.

Bartonella Henselae can be seen in cat scratch disease. It is common in HIV patients. It can give what appears to be swollen lymph nodes. It may be confused with a tumor, but you do not need to biopsy the swollen lymph nodes. This is different from cat bite.

catdogCat bites are deeper and sharper, causing deep injuries. 50% of cat bites will need surgery. Dog bites are associated with an average of five organisms (such as Pateurella Multocida and Pasteurella Canis). Dog bites cause a lot of tissue damage. Dog bites occur with incredible force, like being hit by a truck. Tearing of the tissues is visible and obvious. If the dog bite does not need debridement, you can treat it by antibiotics alone (augmentin or sophixin).  The most common bacteria isolated from both dog and cat bites is pasturella multocida. The treatment is Augmentin.

Panton Valentine Leukocidin

Panton Valentine Leukocidin (PVL) is a cytotoxin that is usually present in the community acquired MRSA and not in the hospital MRSA. PVL has the ability to lyse the white blood cells and cause tissue necrosis and rapid abscess formation. PVL positive strains of community acquired MRSA are associated with a high incidence of DVT, septic emboli, sepsis, multisystem organ failure, complex infection, myositis, and chronic osteomyelitis.

Mycobacterium Marinum

Mycobacterium Marinum is an atypical microbacteria. It is an acid-fast bacilli. The bacteria is grown on a culture at 30C. It will require a long incubation period. It can happen in a freshwater or saltwater aquarium (Lowenstein-Jensen medium). It can also occur in people dealing with fish tanks or swimming pools. The apatient will have ulcers, nodules, and noncaseating granulomas. The hand and wrist are affected in 50% of cases. If diagnosed early, it can be treated with oral antibiotics. In the late stages of infection or in deep infection, surgery must be done. Surgery entails debridement in addition to oral antibiotics for approximately 3 months.

mycoSome of the bacteria are grown in a special culture. Kingella kingae will grow in a blood culture. The mycobacterium avium will grow in a middlebrook medium. The E. coli will grow in a Luria-Bertani medium. Neisseria Gonorrhoeae will grow in a Chocolate Agar medium if you get it from a sterile source like joint fluid. If the specimen comes from a contaminated source, such as the vaginal swab or the urethral swab, then the medium will be Thayer-Martin Agar medium.

Vibrio Vulnificus is found in shellfish in brackish water. It has gram-negative rods. It has septicemia and gastroenteritis. The wound infection will be hemorrhagic bullae, subcutaneous bleeding, and skin necrosis. It can be treated by debridement and broad spectrum antibiotics.

Lymes Disease

lymeLymes Disease is caused by Spirochete Borrelia Burgdorferi. It lives on white-tailed deer. The vector is a tick. Early on, you will get the “bullseye” (erythema migrans). In orthopedics, we get the chronic inflammatory arthritis, the knee will be swollen but not too painful. You can get Bell’s palsy. It can be treated with antibiotics. If the patient is less than eight years old, give them amoxicillin. If the patient is older than eight years old, give doxycycline (in little kids, doxycycline will create staining of the teeth). The period to give antibiotics is between 3-6 weeks.

Gonococcal Arthritis

Gonococcal arthritis occurs in young adults. It is most common septic arthritis in young, healthy, sexually active people. It can cause migratory septic joints. It is caused by intracellular gram-negative diplococci. The treatment is antibiotics (ceftriaxone) and not surgery.

Sporotrichosis

roseSporotrichosis, or rose gardener’s disease, is caused by a fungus called sporothrix. It occurs in people who grow roses. The injury occurs from thorns or splinters. You can get granulomas, nodules, ulcers, or lymphatic spread. H&E staining will show an asteroid body. It can be treated by debridement, amphotericin B, or potassium iodide.

Other Infections

Neonatal infection occurs with Group B Streptococcus. Newborn infections occur between 2-4 weeks. Hip and knee prosthetic joints will get infection with staphylococcus epidermidis or staphylococcus aureus. Shoulder prosthesis and rotator cuff repair will get infection by propionibacterium acnes. Juvenile rheumatoid arthritis may look like an infection, but it is not. Brodie’s abscess probably occurs from staphylococcus aureus infection.

You should always suspect infection. When you aspirate fluid from a joint, do cell count, culture, and try to identify crystals for gout or pseudogout.

Humeral Shaft Fractures

Humeral Shaft Fractures

Usually when a patient suffers from a humeral shaft fracture, the patient will complain of pain and weakness of the upper extremity. Radial nerve palsy can occur in association with the humeral shaft fracture. The clinician must examine the neurovascular status of the upper extremity. Look for wrist drop that results from radial nerve palsy, especially in fractures of the distal third of the humerus. huExamination of the neurovascular status should be done before and after reduction of the fracture. The physician usually orders AP and lateral x-ray views of the humerus. X-rays should include the shoulder and elbow. Any deformity should be recognized and corrected. Most humeral shaft fractures will heal without surgery (90% will heal with conservative treatment). Non-operative treatment is usually done with a coaptation splint which can then be replaced by a functional brace once the pain subsides and then the patient can move the shoulder with the brace in place. Acceptable alignment can be obtained with or without closed reduction of the fracture. Acceptable alignment is less than 20 degrees of anterior-posterior angulation. Less than 30 degrees of varus or valgus angulation and less than 3 cm of shortening is also acceptable. Surgery is done for humeral shaft fractures if there is vascular injury that requires repair. Surgery is also done for open fractures and if there is a brachial plexus injury. In multiple trauma patients, you can use a splint or a brace acutely early during the damage control period, however, later on these patients will need fixation of their humeral shaft fracture. Multiple trauma patients always benefit from fixation of their humeral shaft fracture. Open humeral shaft fractures with radial nerve palsy are usually treated surgically, be debriding of the wound, exploring the nerve, and fixing the humeral shaft fracture. coClosed humeral shaft fracture with radial nerve palsy is treated conservatively. Gunshot wounds, even cases where there is radial nerve palsy, are treated conservatively with a splint and a brace. Wait patiently, expecting recovery of the nerve. The coaptation splint should be snug, extending to the axilla and up to the shoulder. Weekly radiographs are needed for a period of3-4 weeks. The physician may check the Vitamin D-25 level. The fracture usually heals between 6-10 weeks. Observe for loss of reduction. Observe for excessive varus or extension deformity. Shoulder abduction sling may be needed to correct the varus deformity. Varus angulation is common, but it may not affect the functional outcome (may just have cosmetic effect only). If acceptable reduction cannot be obtained or maintained, surgery is usually recommended. Surgery is done in the form of an IM rod or a plate. platePlate fixation is better for healing, less complications, and better weight bearing. We propose that if acceptable reduction cannot be obtained or maintained, we should not rush for surgery. Our novel technique for management of these humeral shaft fractures is to wait. Keep the splint or the brace. Check to see if the patient is making bone. As we know, bone healing goes through several stages- hematoma, inflammation, soft callus, hard callus, remodeling. We intervene when the patient has an unacceptable deformity of the fracture, but the patient is making a lot of callus. Usually we intervene between 4-6 weeks when the callus is soft, malleable, and flexible. Then we correct the deformity by manipulating the mobile callus, and we use external fixation to maintain reduction of the deformity. The external fixator may utilize one pine proximally and one pin distally. Occasionally, we will use two pins proximally and two pins distally. We keep the external fixator in place for 4-6 weeks, and by that time the fracture usually heals in an acceptable position.

Tillaux Fractures

ankle anat

In adults, ligaments are weaker than bone. The anterior tibiofibular ligament in adults is torn first in the majority of ankle fractures. In children, the growth plate is weaker and can become avulsed. An avulsion injury is rarely seen in adults because the ligament gives out instead of avulsing the bone.

growth plaateTillaux fractures occur in adolescents, usually around 12-15 years of age. These fractures occur after the middle and medial parts of the epiphyseal plate closes and before the lateral part is closed. The lateral part of the growth plate remains open, which could allow for an avulsion fracture at the attachment of the anterior tibiofibular ligament. An external rotating force causes an avulsion of the distal tibial epiphyseal plate anterolaterally. Further lateral rotation displaces the fracture and may be associated with fracture of the lateral malleolus. external rotation

Treatment

If the fracture is displaced 2mm or more, the surgeon will want to perform a reduction and fixation. This fixation can be done from either lateral to medial or medial to lateral. Wagstaffe’s fracture is an avulsion of the anterior portion of the fibula by the anterior tibiofibular ligament. This type of fixationinjury is associated with supination external rotation type injuries (Lauge-Hangen) and typically occurs in adult patients.

 

 

Unbelievable Bacteria- Part II

Why do open fractures have increased risk for infection?

The presence of bacteria within an open wound increases the risk of colonization when hardware is used. Once the hardware is colonized, the bacteria grows rapidly. During the rapid growth phase, the bacteria secretes a polysaccharide sugar layer, called a “biofilm”, or slime layer that encases the bacteria. This biofilm provides protection to the bacteria against the body’s defenses and antibiotics.

biooo

Within the biofilm, there are channels that allow the bacteria to pass nutrients, messaging signals, and even DNA to each other. The bacteria pass on their DNA by:

passDNA

  1. Transformation
  2. Transduction
  3. Conjugation

Transformation is when a bacterial cell ruptures, releasing its DNA, which is then taken in by another bacteria. Transduction occurs when DNA is transferred from one bacterium to another by a virus. Phage DNA and proteins are made and bacterial chromosomes are broken up, completing the gene transfer. The phage release themselves from the host, carrying either bacterial or phage DNA. Conjugation occurs when two bacteria attach themselves together with a sex pilus and exchange their DNA.

How does the bacteria become resistant to antibiotics?

beta

The bacteria can alter the genes they express by as much as 50-60%. By doing this, the bacteria can produce enzymes such as beta-lactamases, which destroy certain antibiotics before they can reach their target site. They can also make Efflux pumps which expel antibacterial agents from the cell before it can reach its target site. Finally, by expressing different genes, the bacterial cell wall can be altered to no longer contain the binding site of the antibiotic agent. Because the antibiotics cannot break through the biofilm and access the bacteria, the bacterium in the biofilm can become up to a thousand times more resistant to the antibiotics by the different mechanisms previously discussed.

If there is biofilm on the hardware, what can the physician do?

xfix

The only proven treatment, is to remove the hardware and wash the wound. However, removal of the hardware is a problem if the fracture is not healed and the fixation is needed. The physician may decide to suppress the infection, leaving the hardware until the fracture has improved. Or, the physician may decide the remove the hardware and seek an alternative method for stabilizing the fracture, such as an external fixator, and then using a biological material to help heal the fracture.

These are the issues that make infection with hardware so complex!