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!

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Galeazzi Fracture

Galeazzi Fractures are a type of fracture of the radial shaft which is associated with dislocation of the distal radio-ulnar joint (DRUJ). This particular fracture is name after Ricardo Galeazzi who was an Italian surgeon in Milan. This injury is uncommon and only accounts for about 7% of all forearm fractures in adults.

 

A radius fracture may be short, oblique, or transverse and involves a fractures at the junction of the middle third and distal third of the radius with associated injury to the distal-ulnar joint. The closer the fracture is to the DRUJ, the more likely that it will be unstable. Dislocation of the DRUJ is usually dorsal. It may be associated with either a ligamentous injury or fracture of the styloid process of the ulna.

styloid fx

A fracture is usually located above the proximal border of the pronator quadratus muscle. The distal fragment usually moves towards the ulna. Galeazzi fractures are best treated with open reduction and internal fixation of the radius and assessment of the distal radio-ulnar joint.

unstable

Surgery is necessary. Nonsurgical treatment in adults usually results in recurrent dislocations of the distal ulna and a bad outcome. Surgery is done by a volar plate fixation. Followed by assessment of the Distal Radio Ulnar Joint (DRUJ), if stable, the forearm will be splinted in supination for six weeks. If the joint is unstable, reduce and pin the distal radio-ulnar joint in supination for about four weeks. If the joint is not reducible, open and explore the joint. Check for entrapment of the ECU.

reduction

 

 

Avascular Necrosis of the Shoulder

Avascular necrosis is death of a segment of bone. AVN may affect the proximal humerus due to interruption of the blood supply. The ascending branch of the anterior humeral circumflex artery runs in the lateral bicipital groove and then becomes the arcuate artery. The other artery that is important to the blood supply is the posterior humeral circumflex artery.

avascccc

There are several risk factors for AVN including: Alcohol, Systemic Lupus Erythematosus, infection, trauma, and steroid use. 5-25% of AVN cases are due to steroid usage. Steroids increase the serum lipids in the blood which may precipitate fat embolism into the humeral head blood vessels.

posttrauma

proximal humeral pain

Progressive collapse of the humeral head occurs due to bone death, reabsorption, remodeling, micro fractures and final collapse with joint changes and arthritis. Symptoms include: shoulder pain, weakness, crepitus, and a decreased range of motion. Symptoms are gradual and insidious with delay in the diagnosis and treatment. The patient usually has a history of risk factors.

osteomri

In regards to imagining, x-rays will show the best in the neutral rotation AP view. AVN located on the superior middle part of the humeral head just deep to the articular cartilage. If the crescent sign is seen, this is an indicator of collapse. An MRI is going to be the best imaging study. A patient with AVN of the humerus should have a hip radiograph. If the x-ray is negative and the patient has hip pain, you should obtain an MRI of the hip. It is recommended that a patient with osteonecrosis at the site of the shoulder should undergo an MRI of the hip to rule out asymptomatic osteonecrosis of the hip. You may also need to do an x-ray of the knee. AVN may involve three or more anatomic sites (multifocal osteonecrosis).

Treatment typically consists of:

  • Physical Therapy
  • NSAIDS
  • Core decompression for Stage I and Stage II
  • Resurfacing for Stage III
  • Hemiarthroplasty for Stage III and Stage IV
  • Total shoulder surgery for Stage V
    • Advanced disease
    • The results of total shoulder are inferior to patients with osteoarthritis

 

Tarsal Coalition

Tarsal coalition is a congenital anomaly in which the tarsal bones fuse together, leading to a rigid flat foot, foot pain, and multiple ankle sprains. There are two types of tarsal coalition. The first is known as a Talocalcaneal Coalition, which is a coalition between the talus and the calcaneus. The second is referred to as a calcaneonavicular coalition which is a coalition between the calcaneus and the navicular. When talocalcaneal coalition occurs, it usually happens around 12-15 years of age. The calcaneonavicular coalition presents at an earlier age. About 50% of coalitions are bilateral, and around 20% have multiple coalitions in the same foot. Coalition may be fibrous, cartilaginous, or bony and occurs due to failure of segmentation. It could be associated with fibular hemimelia or Apert’s syndrome.

tarsal anatomy

Symptoms typically consist of patient’s complaining of a painful foot, a history of repeated ankle sprains, and a flat foot deformity. Tarsal coalition may result in a peroneal spastic flat foot. During the physical examination, the physician may find hindfoot valgus. On toe standing, the arch does not reconstitute and heel cord contracture may also be evident during the exam. Furthermore, there may be restriction in the subtalar joint’s range of motion. It is important to check both feet as the condition may be bilateral.

hindfoot

The best imaging study is a CT scan. It can determine the size and location of the coalition. And MRI is also useful in detecting a fibrous or cartilaginous coalition. AP, Lateral, and Oblique view x-rays should be ordered. On a lateral view x-ray, the Calcaneonavicular Coalition can be identified by the “anteater nose sign” and the elongation of the anterior calcaneal process.

ant

A lateral view of a Talocalcaneal Coalition may show talar beaking which is a traction spur that occurs due to the limited motion of the subtalar joint. Additionally, the C sign may be seen which is a radiological sign outlining the talar dome and the sustentaculum. A 45° oblique view is the best for showing calcaneonavicular coalitions.

45oblique

Nonoperative treatment usually consists of anti-inflammatory drugs, modified activities, or the use of a brace or cast. Surgical treatment for the calcaneonavicular coalition usually consists of resection with an interposition of the extensor digitorum brevis muscle or a fat graft no matter the size of the coalition. Similarly, Talocalcaneal coalitions that involve less than 50% of the subtalar joint are also resected. A triple arthrodesis procedure is performed for large coalitions, failed resections, or advanced conditions.