What Is Metacarpophalangeal Arthrocentesis?

Joint aspiration (arthrocentesis) helps diagnose inflammatory or non-inflammatory arthritis.

Joint aspiration (arthrocentesis) of the metacarpophalangeal joint is a diagnostic procedure involving the extraction and analysis of the synovial fluid of the joints. 

It is an important component in diagnosing arthritis and differentiating inflammatory arthritis from non-inflammatory arthritis. Arthrocentesis can also be performed therapeutically (for pain relief, drainage of fluid, or injection of medications).

Any joint in the body can be aspirated. Joint aspiration is a relatively quick and inexpensive procedure to perform. It can be done in a clinic or a hospital. It can be done by any physician, physician’s assistant or nurse who has the training and equipment. 

Metacarpophalangeal arthrocentesis may be indicated for any patient with inflamed metacarpophalangeal joints who do not have an established diagnosis. Inflamed joints cause redness, warmth, tenderness, swelling, and pain during movement. 

Some conditions that may require joint aspiration and analysis to establish diagnosis are:

• Monoarticular arthritis (inflammation of the joint)
• Septic arthritis (infection of the joint)
• Joint effusion (swelling due to fluid accumulation in the body)
• Intra-articular fracture (fractures which involve the joint space) 
• Crystal arthropathy (accumulation of calcium crystals in the joint and surrounding areas)

Joint aspiration may be performed as a treatment in certain conditions, such as:

• Repeated aspirations can be part of the management of septic joints to relieve discomfort and prevent joint damage.
• Aspiration can be considered in cases of hemarthrosis (blood in the joints) to prevent adhesions. 
• Aspiration can be performed along with injecting intra-articular medications such as corticosteroids or hyaluronic acid to improve efficacy. Steroid injections help reduce joint inflammation, reduce pain, and preserve joint structure and function. Hyaluronic acid lubricates the joint, decreases impact, delays joint aging, reduces pain, and stiffness. 

Metacarpophalangeal arthrocentesis should be done with caution in patients with bleeding disorders or those on anticoagulant drugs. Patients taking anticoagulant drugs may be advised to stop the medications a few days before the procedure and resume again after the procedure.

Sometimes, metacarpophalangeal arthrocentesis may be performed using radiological guidance, as it may be required to confirm the presence of fluid before aspirating. Radiological guidance can help in aspirating other deep and technically difficult joints like the hip joint or spine. 

Metacarpophalangeal arthrocentesis is a relatively quick procedure but may be performed under local anesthesia to avoid pain. 

• A needle of appropriate size and length is introduced into the joint and the synovial fluid is collected in syringes. 
• The fluid is then sent for analysis under the microscope. 
• Apart from microscopic analysis, the appearance of the aspirated synovial fluid can indicate certain features. 
• Normal fluid is clear or light yellow and viscous. Inflammatory fluid appears darker yellow to cloudy in appearance and loses its viscosity. 
• Purulent fluid (pus in the fluid) is brownish to whitish and opaque.

After the procedure, the patient would need to rest for a few minutes, soon after which they can resume normal activities. Patients may experience pain and bruising which resolves in a few days. Ice packs and pain killers can help reduce pain and bruising.

Metacarpophalangeal arthrocentesis is a relatively safe procedure and complications are rare. The common complications patients usually face are:

• Localized bleeding
• Pain and swelling
• Septic arthritis (infection of the joint)
• Reaction to local anesthesia

If other medications like steroids are simultaneously injected, though rare, it may cause localized shrinkage or hypopigmentation of the skin. Long-term use of steroid injections may cause systemic side effects like weight gain, swollen face, stretch marks, and easy bruising.