Overview of Arthrocentesis
Arthrocentesis is a medical procedure where doctors collect fluid from the joints, called synovial fluid. They do this to either identify a disease or to help relieve pain or discomfort. The main reason for this procedure is to check this joint fluid for any signs of infection or inflammation.
The exact steps of this procedure can differ depending on which joint is being examined, but the overall method stays the same. This procedure is generally very safe and rarely results in complications when performed properly. There are only a few cases in which this procedure should not be performed.
Anatomy and Physiology of Arthrocentesis
The specific structure and important points of a joint can change depending on which joint we are talking about. So, if you want to understand the details of a particular joint – like the elbow, knee, or shoulder, you would need to look at specific articles related to those joints. These articles will give you information about the joint itself and the parts around it.
Why do People Need Arthrocentesis
Synovial fluid aspiration, also known as joint fluid analysis, is a procedure performed for several reasons:
It can be useful in detecting joint infections. This is critical because untreated joint infections can lead to permanent damage.
The procedure can also provide important information that helps diagnose inflammatory diseases such as arthropathy, which is a general term for any disease affecting the joints, and spondyloarthropathies, a group of inflammatory diseases that affect the joints of your spine and nearby joints.
Synovial fluid aspiration can be used to give medicines directly into the joint to treat acute or chronic arthritis. Arthritis is a condition that causes inflammation and stiffness in the joints.
In some cases, this procedure can provide relief from the symptoms of a swollen, painful joint or inflammatory conditions like rheumatoid arthritis, which is a chronic inflammatory disorder that can affect more than just your joints. It can drain excess fluid and reduce pain.
The procedure can be used to remove blood from a joint, known as a hemarthrosis, which can occur following an injury.
Finally, if someone has a deep cut or puncture wound near a joint, synovial fluid aspiration might be performed to see if the joint space is connected to the injury.
When a Person Should Avoid Arthrocentesis
There is one main reason why a doctor might not be able to perform an arthrocentesis, which is a procedure where fluid is removed from a joint, such as the knee, to be studied. This reason is if the patient has a skin infection around the joint area, called cellulitis, because it could potentially spread the bacteria into the joint space.
There are a few other reasons why a doctor might think twice before performing this procedure. If the patient has bacteremia, where bacteria is present in the blood, the procedure could potentially introduce bacteria into the joint space. Another debated reason is Coagulopathy, which is a condition that can cause spontaneous bleeding or make it more difficult to stop bleeding. Some doctors worry that the procedure might cause a condition called traumatic hemarthrosis – bleeding into joint spaces, but multiple studies have suggested that this is unlikely.
Equipment used for Arthrocentesis
Getting your skin ready
We need to clean your skin before we start (using solutions like chlorhexidine, betadine). This helps in making sure the skin is rid of bacteria that could lead to infection. During this process, the medical team will use sterile gloves, sterile drapes, and sterile gauze to keep everything free from germs.
Getting to your Blood or Body Fluid
Syringes are used to inject medicine and draw body fluid from your body. We typically use a small syringe (3 cc to 5 cc) for injecting local anesthetic, which is a medication that numbs a small area of your body. A larger syringe (10 cc to 20 cc) may be used to draw fluid from your body if necessary.
Needles
Similar to syringes, we use small needles (25 gauge to 27 gauge) to inject the local anesthetic. Meanwhile, bigger needles (18 gauge to 22 gauge) are used for fluid aspiration, which is a medical way of saying the removal of fluid.
Medications
As mentioned earlier, a local anesthetic is used to provide numbness to the area being treated. Other medicines may also be used if your doctor decides they’re necessary for your treatment.
Other
In some cases where a lot of fluid needs to be removed, a three-way stopcock is used. The removed fluid can be put in specimen collection tubes to be sent to a lab for further study. We also use a tool called a hemostat to hold the needle steady if we need to change syringes during the procedure.
Who is needed to perform Arthrocentesis?
This process can be done alone, but it might be more comforting and beneficial if a nurse or another medical team member is by the patient’s side. They can help reduce the patient’s worry, deal with unexpected issues with the medical equipment, and keep a record of how the process went.
Preparing for Arthrocentesis
It’s extremely important to prepare correctly for a procedure. This means double-checking that all necessary tools are available and within reach at the patient’s bedside. Patients should also be arranged in the most likely position to ensure a successful procedure, which depends on which joint needs to be treated. It’s also essential to make the patient as comfortable as possible during the procedure. This may involve providing pain relief and medication to help reduce anxiety if required.
How is Arthrocentesis performed
This article explains the general steps of arthrocentesis, a procedure where a doctor removes fluid from a joint in your body with a needle. This doesn’t cover the specifics of arthrocentesis on different joints like the elbow, knee or shoulder. You can find more detailed information in articles titled “Elbow Arthrocentesis,” “Knee Arthrocentesis,” and “Shoulder Arthrocentesis Technique.”
The procedure goes like this:
- The doctor first identifies the specific joint by feeling the surrounding bone structure.
An ultrasound can be useful in finding any accumulations of fluid. - A spot is chosen for needle insertion, considering the structure of the joint. The path of the needle avoids tendons (a flexible but non-elastic cord of strong fibrous collagen tissue attaching a muscle to a bone), major blood vessels, and large nerves.
- Next, the doctor cleans the area where the needle will go in and the surrounding skin with a special cleaning fluid. The skin is allowed to dry and then a sterile cloth is placed around the needle area.
Now, creating a small raised area with local anesthetic using a thin needle at the insertion point. The needle is then moved deeper to numb the path down to the joint. For very painful joints, an additional anesthetic can be used that numbs a larger area, called a regional nerve block. A larger needle, attached to a syringe, is then inserted into the joint along the numbed path. Small modifications can be made when draining large amounts of fluid from the joint – a control can be inserted between the needle and syringe which allows changing the syringe during the draining process. The needle is held tightly with a sterile tool while the syringe is removed.
The goal is to remove as much fluid or blood as possible. If the fluid doesn’t flow, it means that either all the fluid has been drained, the needle has moved, or the needle is blocked. To fix this, the needle can be moved slightly forward or backward, turned, or the suction intensity can be adjusted. The fluid that has been removed is then put into tubes and sent for laboratory analysis according to the patient’s condition. After the procedure, a bandage is put over the spot where the needle was inserted, and pressure is applied to stop any bleeding.
Possible Complications of Arthrocentesis
While getting a joint fluid test known as arthrocentesis, complications are very rare but can occasionally occur. Here are the potential issues:
1. Infection. If the procedure isn’t completely sterile, or if there’s already an infection on the skin, bacteria could get into the joint space. Doctors can reduce this risk by strictly keeping everything clean and sterile, and by not inserting the needle through infected skin or tissue under the skin.
2. Bleeding. Hemarthrosis, which is bleeding into the joint space, is rare after the procedure. It’s more common with patients who have a condition that causes them to bleed more easily. To avoid this, the doctor will insert the needle in a straight line, without moving it side-to-side, to avoid damaging blood vessels.
3. Allergic reaction. Some people might be allergic to the local anesthetic, the medicine used to numb the area. If you’re allergic to this type of medication, the doctor won’t use it for the procedure.
What Else Should I Know About Arthrocentesis?
Examining joint fluid (synovial fluid) is a key step in figuring out the reason behind joint swelling. This fluid can fall into one of four categories: non-inflammatory, inflammatory, bloody (hemorrhagic), or infectious (septic).
If the fluid is non-inflammatory, it might be because of a condition called osteoarthritis, which causes cartilage – the tissue that cushions the ends of your bones – to wear down over time.
Inflammatory fluid can be a sign of various conditions. Gout and other diseases caused by tiny crystal deposits in the joints, rheumatoid arthritis (an autoimmune disease that affects the joints), and other diseases that cause inflammation in the joints can all produce this type of fluid.
Bloody fluid can appear in patients with a bleeding disorder, either on its own or after an injury. It can also occur in any patient following a severe injury.
Finally, septic arthritis is a serious condition that can cause a lot of health problems and even death if not identified and treated quickly. This type of arthritis can be divided into two categories: non-gonococcal (not related to gonorrhea) and gonococcal (related to gonorrhea). The vast majority of septic arthritis cases (>80%) are caused by non-gonococcal bacteria, primarily staphylococci and streptococci. Risk factors for this type include using intravenous drugs, having heart valve infection (endocarditis), bone infection (osteomyelitis), abscesses, and skin wounds. Gonococcal arthritis is more frequent in young, sexually active patients and can include other symptoms like migrating arthritis (arthritis that moves from one joint to another), inflammation of the tendon sheath, and urinary complaints.
Just by looking at joint fluid, doctors can get clues about what’s causing the problem. Normal joint fluid is clear or straw-colored, while inflammatory fluid is less clear. Bloody fluid can show up spontaneously in patients with hemophilia, a bleeding disorder, or after an injury. The presence of fatty bloody fluid can hint at a hidden bone break.
Additional laboratory analyses include cell count, bacteria staining (gram stain), crystal analysis, and glucose and protein levels. Characteristics of each fluid type include:
– Normal: Clear or straw-colored, a low white blood cell count, a range of neutrophil (a type of white blood cell) count, and no bacteria found in the staining procedure.
– Inflammatory: Yellow color, a higher number of white blood cells, a range of neutrophil count, and no bacteria found in the staining procedure.
– Bloody: Cloudy appearance, a low white blood cell count, very few neutrophils, and no bacteria found in the staining procedure.
– Septic: Cloudy or opaque appearance, a very high white blood cell count, a high neutrophil count, and bacteria found in the staining procedure 30-80% of the time.
In the study of crystals in joint fluid, monosodium urate crystals seen in gout are needle-shaped and negatively refract light. Calcium pyrophosphate crystals seen in ‘fake gout’ are rhombus-shaped and positively refract light.
