surgery Lec # 5

7/29/2019 surgery Lec # 5

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Bone and Joint Infections

Theres a well-known overlap between orthopedics and dentistry in the field of bone. What

affects the bones in the skeleton might as well affect the maxillofacial area and the mandible; an

infection in the tibia or femur could also affect the mandible, or a cystic arthritis in the knee jointcould occur in the temporomandibular joint.

The bone is composed of two layers; Cortex and Medulla. The cortex as the outer layer, and the

medulla as the inner layer containing the bone marrow.

The medical terms used to describe bone infections are Osteomyelitis and Osteitis. The word

Osteomyelitis is divided into two parts, Osteo: bone and Myelitis: Bone marrow. So

Osteomyelitis implies that the infection involves not only the cortex but also the bone marrow

spaces in the medulla, however if the infection is present only in the cortex of the bone it is

referred to as Osteitis.

Classifications of Osteomyelitis

Osteomyelitis is classified according to the:

I. Routes of Infection1)

Exogenous: A source of microorganism introduced from the external environmentdirectly to the bone, for example a stab wound.

2) Hematogeneous: Microorganisms disseminated through the blood stream from a site ofinfection in the body to settle in the bone. The source of infection will travel through the

blood to reach the proximal or the metaphyseal part of the bone. Examples of way the

infection could get through:

- In the infantile stage, Osteomyelitis might be transmitted through an infectedumbilical chord at birth.

- Through skin infection.- If an adult had history of Urinary Tract Infection.- Through arterial catheterization or administration of an IV line for antibiotics

or fluid intake.


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3) Contiguous spread: A direct spread from a nearby focal infection, most commonlyaffecting the superficial bones (Ex: Tibia and Ulna) where an infection could easily

extend from the infected overlying soft tissues.

II. Types of Microorganisms: they are organized according to age groups whereStaphylococcus Aureus is the most common.

1) Neonates ( 5 years (Osteomyelitis is commonly knownas being a pediatric disease).

Rare in adults unless they are immunocompromised. Boys > Girls. 1/3 of cases have reported history of trauma. 80% of Osteomyelitis cases are located in the metaphysis of the bone.


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Anatomy of the bone:

Epiphysis: Ends of the bone, either upper or lowerends.

Diaphysis: Site of entry of blood vessels.Growth platesMetaphysis: Unique anatomical structure and rich

in blood vessels. These blood vessels enter

through the diaphysis as large caliber (largediameter), they start to narrow down extending

through the bone reaching the metaphysis and

the growth plate (which is active in young age).

The vessels cannot penetrate the growth plate

and they will form a loop (harping loop or reverse

loop) at the metaphysis. So blood flow through

these vessels will slow down gradually, and this

slow blood flow is a good media for bacterial

growth. This is why Osteomyelitis most commonly

occurs at the metaphysis.

** So Osteomyelitis is more common in the

metaphysis area of the bone. But out of all bones in

the body, the Femur Bone (27% of cases), the Tibia,

or long bones in general are the most commonly

affected.


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Stages of Osteomyelitis:

1) Primary Focus Infection2) Stage of Inflammation: Where chemotaxis of macrophages and other inflammatory

mediators occurs.

3) Formation of sub-periosteal abscess: Abscess may migrate within the bone through theHaversian canals or could travel by a duct outside the bone creating what is called a sinus

discharging pus.

*All these changes in the inflammatory habits will increase the intra-osseous pressure, so

the pus will try to drain at any escape.

4) Sequestrum formation: after the drainage of pus, the bone will be left with empty spaces

called bony infarction (dead bone).

5) Resolution of infection: New bone formation, and this is very important for healing

because otherwise the infection will alternate into its chronic form.

Acute Osteomyelitis

Clinical Picture (Diagnosis):

Three sequels should be taken into consideration when a physician is trying to reach a

diagnosis to manage a certain case:

1) History:- In most of the cases, Osteomyelitis will be associated with preceding infections. For

example, if a 5 year old child presents pointing to pain in his/her femur and this pain was

persisting for that last 48 hours. The mother should be asked about any history of

previous infections (Ex. Respiratory tract infections, Tonsillitis, trauma, or even skin

lesions that occurred somewhere else in the body) to identify the source of infection

transmitted from the blood to the bone.

- The older the child gets, the easier it is to take history, but the challenge arises when aneonate for example is reported from the department of prematurity by pediatricians

suspecting an infection in a certain bone. The physician in this case will relypredominantly on his/her sense and intuition. Symptoms associated with neonates could

be:

Failure to thrive: the baby refuses to breastfeed and is not gaining weight. Drowsiness Baby is irritable most of the time


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Most of the cases occur around the knee, distal or proximal femur, or on the shaftof the femur.

2) Examination:Pain will be very localized rather than diffused; the area of tenderness will be at its

maximum in a single point, just like a bell ring. So this presentation is called The Ring

Bell Sign and its an indication for a focus of infection and will rule out many other

diseases (Ex. Tumors, Trauma, or any metabolic bone disease).

Affected limb will be reluctant to move.Fever: Patients usually present with intermediate fever rather than high grade fever,

the reason behind that is that the patients would have already started taking

medications Ex. Paracetamol or NSAIDs.

MalaiseLoss of appetiteSepticemia (only in severe/toxic cases)

3) Investigations: How to approach the case?a) Laboratory Investigations: They are to some extent invasive, Ex. needles to

withdraw blood.

- Complete blood count (CBC): Standard test for any work up especially forpatients with suspected Osteomyelitis. This test is not accurate and does not

give a direct indication to the disease. In infected patients, levels of WBCs

should be elevated however this occurs only in one third of the cases, this is

why more sensitive tests should be done; ESR and CRP which are called

Inflammatory Phase Reactants (both are elevated during inflammation).

- ESR: Erythrocyte Sedimentation rate. Used more in the follow up of patientsrather than diagnosis.

- CRP: C-reactive protein test, measures general level of inflammation in thebody. Elevated in 98% of infected patients, peaking on day 2 of

inflammation. More specific than ESR since it fluctuates easily with thebodys inflammatory changes; it rises on infection more quickly and will

respond to antibiotics faster. So it is the most diagnostic lab investigation.

- Blood Culture: 50% of cultures from CBC are positive.


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- Direct/Needle aspiration: Using a sterile needle (18gauge) or a spinal needleafter sterilization with a bit of anesthesia Ex. Lidocane, a sample is taken

from the suspected location of infection, or if there were any pus

production it could also be aspired. The aspiration is sent to blood culturing

(positive in 2/3 of cases).

b) Radiological Investigations: The imaging study for a child with Osteomyelitis. Plain X-ray:- Initial X-ray: Pathological changes in the body need time to manifest

themselves, so initial x-rays could appear to be negative/normal most of

the time, especially in the early few days (72 hours) where the only sign is

soft tissue elevation. So initially, x-rays are not to depend on but they are

done to rule out fracture.

- After 1-2 weeks: X-rays are most informative in that period of time. Theywill start to show rarefaction (reduced density) of bone and periosteal

reactions.

- More than two weeks: Changes will be more prominent and infection willspread over the entire bone (Epiphysis, Diaphysis and Metaphysis).

*Patients cannot wait for a couple of weeks with infection to have a clear diagnosis, so for

more precise methods of investigation, other non-invasive tests could be made:

Ultra-Sound: it will be further explained later. (Page 12 ^) Bone Scan: Its an injection with a nuclear labeled material (technetium-

99m) where it is up-taken in areas with higher metabolic rates.

Gallium scan: More sensitive (sensitivity>91%) than bone scan because inthis test the polymorphonucleus of the white blood cells themselves are

the marker for the investigation.

Other tests include: CT-scan and MRI. They are not frequently used if thediagnosis was established from the previous tests, however if the physician

is having problems with the differential diagnosis especially in cases of

tumors and Ewings sarcomas they could be done.


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Osteomyelitis in adults:

Osteomyelitis in adults is very rare but if it happened the most affected locations would be the

vertebrae, specially the thoracolumbar vertebrae.

Symptoms and signs of adults with Vertebral Osteomyelitis:

- Localized pain in the vertebrae.- Back ache- Fever- History of Urinary tract or Neurological infection or any procedure done in the near past

(1-2 weeks).

Risk factors:

- Immunocompromisation- Diabetes- Old age

*If the adult is healthy is it very unlikely to develop this sort of infection.

Differential Diagnosis:

Septic Arthritis: Septic Arthritis is the infection of the joint itself. In some cases, especiallyin young patients, the infection might attack the metaphysis as Osteomyelitis and then

easily spread into the joint causing secondary Septic Arthritis. This occurs particularly in

younger age groups because of two reasons:

1. The growth barrier did not yet make a border between the metaphysis and theepiphysis.

2. The metaphysis is still a part of the joint. Rheumatologic Disorders Sickle Cell Crisis Thalassemic Crisis Ewing's Sarcoma: It is a malignant tumor of the bone. The lamellated or "onion peel"

appearance of the bone seen on a radiograph with this disease is similar to what is seen

with Osteomyelitis.


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Management of Osteomyelitis:

Once the diagnosis of Osteomyelitis is confirmed, the patient must be hospitalized. Unlike any

other type of infection (ex: tonsillitis), bone infections are difficult to treat because the infection

is hidden within a barrier (bone), so a strong antibiotic at high concentration is needed to

penetrate through the bone and reach the site of infection in an adequate amount.

Unfortunately, oral antibiotics cannot achieve this penetration, and thus IV antibiotics are

needed in early stages. Other reasons for hospitalization are that the patient has high fever and

requires IV fluids for hydration and correction of the electrolyte imbalance. In addition, the

patient must be immobilized and analgesics might be needed for the pain.

The specific treatment of Osteomyelitis is the administration of antibiotics at an early stage as

they become less potent when administered at a late stage. One knows that it is impractical to

start a course of antibiotic before knowing for sure the exact type of microorganism causing theinfection (ex: Staph, Strep, Pseudomonas, or E.coli) and a clinician should normally wait for

laboratory results and blood cultures to decide what type of antibiotic is most suitable. However,

a patient with Osteomyelitis should not be left without treatment waiting for laboratory results

(which take 72 hours ~ 3 days) so empirical therapy must be used.

Empirical therapy means that an antibiotic is chosen by common sense according to the

microorganism that is most likely present. Examples of empirical antibiotics are: Gentamycin,

Cephotaxime, Ceforuxime, Clindamycin, Vancomycin. These empirical antibiotics should be given

in the first 72 hours until the laboratory results are out.

Once the specific microorganism causing the infection is known, the patient should be treated

with a more specific antibiotic. For example, if the infection is caused by Staph aurous, the

patient is treated by Penicillins (Amoxicillin and Ampicillin) or by Cephalosporins (Cephozulin). If

the cause of infection is a gram negative bacteria like Salmonella, the patient may be give

Ampicillin, etc.

IV antibiotics should be given for about 3 weeks followed by oral antibiotics, the patient starts

taking oral antibiotics once his/her symptoms alleviate (no pain, no fever, CRP level normal,

ESR


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Indications for Surgery:

1. Abscess formation: surgery is required in any case where soft tissue or subperiostealabscess is present (when pus is discharged). Antibiotics should not be used in the

presence of an abscess since it will exacerbate the situation because the abscess will

enclose itself to prevent the entry of the antibiotic. So as a general rule in medicine,

abscess formation requires incision and drainage.

2. When a Fine Needle Aspiration reveals a purulent fluid, suggesting the presence of pus.3. Failure of antimicrobial treatment in the first 3 days. In this case, the bone should be

drilled and the Sequestrum (the dead bone cavity depriving the bone from blood

supply) should be removed by a process called Sequestrectomy. Sequestrectomy

should be handled by an expert especially if the Sequestrum is near the growth plate.

Complications of Osteomyelitis:

- Focal infection (ex: in the head of the femur) might spread throughout the body, causingsepticemia.

- Progression into a Septic Arthritis.- If the infection spreads and involved a nearby growth plate, this will cause growth

disturbances.

- Pathological fractures, since Osteomyelitis weakens the bone.- Progression into chronic Osteomyelitis (very dangerous complication, should be avoided)

Sub-Acute Osteomyelitis

This type of Osteomyelitis is challenging because of its unclear presentations and because it

usually mimics other Oncological disorders such as Osteoid Osteoma.

Unlike Acute Osteomyelitis, a patient with Sub-Acute Osteomyelitis is presented with a longer

history of pain (1-2 months); the pain is usually mild, intermittent, irritating and the onset of pain

is not acute. Other constitutional symptoms like fever and toxemia are not present. Also, themicroorganism involved is less virulent and not powerful enough to cause the usual pathological

changes.

Initial radiographs may be abnormal, and laboratory data are not always conclusive as in acute

Osteomyelitis. For instance, WBC count may be normal, and CRP might as well be normal. So in a

case where a patient has a long history of pain in his distal tibia, but his/her test results show a


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normal WBC count and CRP level, then Sub-Acute Osteomyelitis should be suspected as well as

other malignancies. In this case, a biopsy is usually taken, and this biopsy is cultured. The culture

will usually show Staphylococcus or Gramve anaerobic Pseudomonas, but in more than half of

the cases the cause is polymicrobial. Polymicrobial infections can be treated by Gentamycin,

Tinam, Imipenem

What is most concerning about Sub-Acute Osteomyelitis is that it has a high recurrence rate of

about 40%.

Treatment of Sub-Acute Osteomyelitis:

After results of the tissue culture are obtained, IV antibiotics should be administered followed by

oral antibiotics for at least one month.

Chronic Osteomyelitis

Chronic Osteomyelitis is usually a progression of an untreated Acute Osteomyelitis, and here the

patient entered whats called an On-Off phenomenon. In On-Off phenomena, the patient will

experience times free of symptoms (4-5moths or even more), and other times where the

symptoms relapse (may last for 2-3 weeks).

The pain may be continues or intermitted, and pus may be discharged from a sinus, which opens

at times and closes at others.

Patients with higher risk of progression of acute Osteomyelitis into Chronic Osteomyelitis usually

suffer from:

Nutritional deficiencies Vascular Diseases Low immunity Diabetes Acute Osteomyelitis caused by a high virulent organism not responding to antimicrobial

agents.

As mentioned above, Chronic Osteomyelitis is most commonly a complication of an

unsuccessfully treated Osteomyelitis. However, it might be due to a post-traumatic injury

especially in war victims where a microorganism has entered the bone through a stab or a

contaminated injury. Chronic Osteomyelitis might also occur as a post-operative complication.


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Investigations:

- Lab test- Cultures (maybe pus culture)- Plain X-ray- Sinogram: Dye injected into the sinus to trace and follow the amount of bone involved,

sometimes the whole bone is found to be complicated.

Complications of Chronic Osteomyelitis:

- High recurrence rate- Pathological fractures- Metabolic bone disease- Carcinogenic transformation

Treatment of Chronic Osteomyelitis is unfortunately very depressing for the patient due to its

long period. The treatment includes: antibiotic administration, local antibiotic inside the bone

defect (ex: Gentamycin beads), and maintenance of bone stability to avoid pathological

fractures.

Septic Arthritis

Septic Arthritis is an infection in the joint, and the word 'Septic' implies that this type of Arthritis

is caused by a microbial agent, mainly bacterial (Staph aurous, Strept, Pnemococcus). It might

also be due to a viral infection, which tends to be transient and does not usually cause the

destructive changes inside the joint.

A good way to distinguish between Septic Arthritis and other forms of Arthritis (ex: Rheumatoid)

is that Septic Arthritis is monoarticular, meaning that it affects only one joint of the body, unless

if it's caused by Neisseria Gonorrhea were the infection will occur in multiple joints (ex: both

knee joints).

Septic Arthritis occurs most commonly in the hip joint, with more than 50% of cases seen in

pediatric age groups of less than 3 years of age. So, a common presentation of this disease in the

ER is a child (usually


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In most of the cases, Septic Arthritis is seen in association with Osteomyelitis. However, it is not

important to find out whether Osteomyelitis occurred first and caused a secondary Septic

Arthritis or vice versa

Pathogeneses:

Changes in the Synovium (synovial fluid) lining the joint capsule. Vascular Changes (because of inflammation) Attraction of WBC, macrophages, and inflammatory mediators (Interleukins) causing

further exaggeration of the condition.

Clinical picture of Acute Septic Arthritis:

Huge swelling around the infected joint Pain, Calor (hotness), redness Immobilization Fever Malaise

Lab investigations:

CBC CRP, ESR

Blood Culture (40-50% positive) Plain X-ray Bone Scan/ Gallium Scan Ultrasound

^Ultrasound is an easy, noninvasive, and informative test that is necessary for the

diagnosis of Septic Arthritis. It enables the clinician to examine hidden joints (for example

hip joint), and check for the presence of accumulated fluids within it. A needle aspiration

is performed on the accumulated fluid, in case of its presence, under the guidance of the

ultrasound. As a role, if WBC count in this fluid showed up to be greater than 50,000 withmore than 90% being polymorphonuclear, then a diagnosis of Septic Arthritis is confirmed

even if the blood cultures were negative.

In the absence of an ultrasound (limited facilities), an X-ray might be sufficiently

informative. The diagnostic mark in an X-ray is the teardrop sign, which is the space

between the acetabulum (concavity in the pelvis where the head of the femur meets,


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forming the hip joint) and the head of the femur compared to the other healthy hip joints.

If the space is widened, this is an indication of fluid accumulation in the joint pushing the

head of the femur laterally.

Differential Diagnosis:

1. Acute Osteomyelitis (same management and treatment)2. Transient Sinovitis of the hip: viral reactive Arthritis, patients usually have history

of Upper Respiratory Tract Infection, Hemarthrosis (bleeding into joint spaces)

etc

Treatment of Septic Arthritis:

1. A patient with Septic Arthritis requires admission to hospital.2. The infected joint should be splinted to ensure fixation and immobilization, because it'svery painful to the patient.3. Empirical antibiotics are given followed by definitive antibiotics.4. Surgical drainage: it is of high importance to drain all the pus accumulated inside the joint

to avoid lysis and destruction of the cartilage by inflammatory mediators.

Complications of Septic Arthritis:

- Secondary Osteoarthritis: Occurs when the patient is not treated from the joint infectionresulting in growth disturbances in that joint, leg shorter than the other, and the need for

an early artificial joint.- Cartilage damage- Slow dislocation of the joint- Arrest of bone growth

Done By: Lama Ashour & Raya Dawood

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surgery Lec # 5