Haemarthrosis of the Knee

Hemarthrosis is blood inside the knee or bleeding into the knee joint space. The swelling and fluid inside the knee joint is usually relieved with an aspiration. During the aspiration, the physician will insert the needle on the lateral side of the knee, just above the upper border of the patella. The needle enters below the patella into the suprapatellar bursa which is continuous with the joint cavity. This aspiration technique is different than how physicians perform injections. For a knee injection, the needle is inserted at the lower border of the patella on either side of the patellar tendon at the soft spot.

aspiration v inspirationThe color of the fluid aspirated—not bloody effusion—is probably due to synovial irritation caused by chronic processes such as gout, pseudogout, arthritis, rheumatoid arthritis, or degenerative meniscus. A degenerated meniscus may be associated with swelling and fluid collection; usually not bloody. The peripheral portion of the meniscus is vascular (about 3-5 mm). The blood supply of the meniscus originates from the medial and lateral genicular arteries. Although a degenerative meniscus effusion is not bloody, a traumatic tear of the meniscus may cause bleeding inside the knee joint.

arthrA bloody effusion could be trauma related or non-trauma related. For example, hemarthrosis can be caused by trauma or injury to the structures of the knee such as the ACL, PCL, or meniscus. Hemarthrosis can also occur due to tibial plateau fractures, chondral fractures, patellar dislocations, or a meniscal tear. Non-traumatic conditions that can cause hemarthrosis include: PVNS, sickle cell anemia, hemophilia, anticoagulation, or hemorrhage following total knee replacement.

Hemoarthrosis from trauma or injury indicates a significant knee injury such as ACL (75-80%) or a meniscal tear. If aspirations of the knee after trauma shows hemarthrosis, early evaluation of the injury may be necessary to define the extent of damage. The physician may get an MRI early.

meniscusAbsence of hemarthrosis does not mean a less severe ligament injury—the blood may escape without distending the capsule. A severe injury may cause minimal or severe joint effusion. More than 20cc of fluid may affect the quadriceps function and prevent full extension of the knee. A hematoma should be evacuated. The bloody aspirate should be examined for fat to rule out a fracture. The aspirate may vary in color depending on the severity of the injury and the duration of the symptoms. Fat is less dense than blood and fat floats on the surface, whereas blood is heavier and stays on the bottom.

mri.The presence of a fat/fluid level is diagnostic of a fracture even if a fracture is not seen on an x-ray (occult). Fat/fluid level is usually seen with tibial plateau, chondral, and patellar fractures. The cross table lateral view of the knee shows it well. When a fat/fluid level is seen, look for intra-articular fractures. Lipohemarthrosis is only seen on horizontal x-ray beams with the beam parallel to the floor. It occurs in 40% of all fractures inside the joint.

lipohemoarthrosis

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Monteggia Fracture Dislocation

Monteggia fracture is the fracture of the proximal third of the ulna with dislocation of the radial head. The fracture is more common in children and rare in adults. Treatment will depend on the age of the patient.The normal position of the radial head and shaft should line up with the capitellum in any position. Dislocation of the radial head may be missed.

normal position

Type I Monteggia fractures occur in the middle or proximal third of the ulna with anterior dislocation of the radial head and characteristic apex anterior angulation of the ulna. This is the most common type and occurs in about 60% of cases. In children, you will immobilize the fracture in flexion and supination. Flex the elbow more than 90 degrees to relax the biceps.

Only 15% of Monteggia fractures are Type II. This fracture occurs in the middle or proximal third of the ulna with posterior dislocation of the radial head and characteristic apex posterior angulation of the ulna. You will need to immobilize this fracture in extension.

type ii

20% of Monteggia fractures are type III. These fractures occur at the ulna just distal of the coronoid process with lateral dislocation of the radial head.

Type IV only occur 5% of the time and is classified as the fracture of the proximal or middle third of the ulna with anterior dislocation of the radial head, and a fracture of the proximal third of the radius below the bicipital tuberosity. This fracture will require surgery, even in children.

TypeIVWith Monteggia Fracture Dislocations, it is important to perform a neurovascular exam. Nerve injury, especially involving the posterior interosseous nerve, is not uncommon. Additionally, you will want to watch the patient for compartment syndrome.

Treatment in adults consists of ORIF of the ulna—when the ulna is properly aligned and fixed, the radial head will reduce by itself. Radial head instability may usually be caused by nonanatomic reduction of the ulna or by interposition of the annular ligament. Fracture of the ulna may need a bone graft for healing.

platingWhen treating pediatric patients, it is important to note that the radial head ossifies around age 4. For Type I-III fractures, you will perform a closed reduction of the ulna to restore the length of the ulna and reduce the radial head. Remember to immobilize in flexion and supination. Type IV fractures or cases where you are unable to reduce the radial head or the length of the ulna in pediatrics will require surgery. Fixation will be done with an IM rod or a plate.

When treating old cases, you will perform an osteotomy of the ulna and an open reduction of the radial head, followed by plating of the ulna.

Pudendal Nerve Palsy

Damage to the pudendal nerve can occur suddenly as a result of trauma to the pelvic region, prolonged bicycling, fractures, or from falls. The pudendal nerve re-enters the pelvis under the sacrotuberous ligament and gives three branches.

usepudendalThe first branch, the inferior rectal nerve, provides rectal tone and perianal sensation. The second branch, the Perineal Nerve, gives scrotal sensation. The third branch, the dorsal nerve of the penis, give branches to the corpus callosum.

The pudendal nerve arises from S2, S3, and S4. The pudendal nerve carries sensations to the external genitals, the lower rectum, and the perineum.

The symptoms of pudendal nerve palsy can start suddenly or develop over time. Symptoms include the loss of sensation or numbness, burning or stabbing pain, difficulty with bladder and bowel functions, and sexual dysfunction.

morenerves

Causes of pudendal nerve palsy include prolonged sitting exercises such as bicycling or following fracture table traction—the nerve is compressed between the ischium and the hard object.

Treatment options are typically conservative, as the condition is usually transient and will improve over time. Treatment includes:

  • Restbike
  • Physical therapy
  • Stretches and exercises
  • Anti-inflammatory medications
  • Injections/nerve blocks
  • Surgery (as a last resort)

 

Prevention options for bicyclists consists of changing the sitting position while riding the bicycle and changing the seat from a narrow seat to a wider seat.

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!