Procedures

Knee arthrocentesis refers to puncture of the knee joint and the aspiration of its synovial fluid. It is used for synovial fluid analysis to aid in diagnosis and also for therapeutic purposes.

Knee joint can be approached by multiple approaches [discussed below]

Indications of Knee Arthrocentesis

Diagnosis

• Acute monoarticular [that affects a single joint] arthritis
• Suspected infection (eg, septic arthritis)
• Inflammatory joint effusion
  • Gout
  • Pseudogout
  • Rheumatologic disorders
  • Reactive arthropathies

Therapeutic

• To relieve a large painful effusion.
• Instillation of medications
• Repeated arthrocentesis for septic arthritis in carefully selected patients as a means of decreasing bacterial load

Contraindications

• Cellulitis in the overlying skin
• Overlying skin lesions (eg, dermatitis or psoriasis)
• Known bacteremia
• Bleeding disorders
• Patient on anticoagulation medication

Procedure of Knee Aspiration or Knee Arthrocentesis

Different Approaches

Knee joint aspiration can be done via a parapatellar approach (usually preferred), a suprapatellar approach, or an infrapatellar approach.

Parapatellar Approach

The knee can be approached from the medial side or lateral side. The insertion site is just below the midpoint of either the medial or the lateral border of the patella. The needle is directed inferomedially. The needle is kept perpendicular to the long axis of the femur and points toward the intercondylar notch of the femur.

Suprapatellar Approach

This approach accesses the joint from the superior aspect. It can be done from the midpoint of either the superomedial or the superolateral border of the patella. The needle is directed toward the intercondylar notch of the femur.

Infrapatellar Approach

In this approach, the needle is inserted about  5 mm below the inferior border of the patella and just lateral to the edge of the patellar tendon.  Piercing of patellar tendon should be avoided with this approach.

Procedure

• Determine the site of needle insertion. This would depend on the approach chosen.
• Prepare the skin with a sterile solution and drape the part.
• Attach the 18- or 20-gauge needle to the 20-mL syringe. In larger effusions, 50-60 ml syringes may be used. Otherwise, an extra syringe should be kept handy, just in case.
• Stretch the skin between two fingers and insert the needle into the joint while keeping a gentle pull on the plunger. Placement of a towel under the popliteal region to flex the knee to 15-20° may facilitate entry by opening up the joint space.
• Readjust the direction of the needle if it strikes the bone.
• If the needle is in the joint, the fluid would start entering the syringe. Milking the region could help in case the flow is slow.
• Once aspiration is complete, the needle is removed and a bandage applied.

Complications of Knee Arthrocentesis

Dry Tap

This can be caused by

• improper needle placement
• A small amount of effusion
• Mechanical obstruction of the needle against cartilage or thickened synovium

Cartilage Injury

This is minimal with smaller bore needles.

Hemarthrosis

Most hemarthroses are small and self-limited. Correction of coagulopathy may be desired if that is the reason for hemarthrosis.

Infection

It is rare. If there appears a higher risk of infection, prophylactic antibiotics may be started.

Shoulder arthrocentesis is the procedure of aspirating joint fluid from shoulder joint and like other arthrocentesis can have a diagnostic or therapeutic purpose.

Shoulder joint or the glenohumeral joint can be approached anteriorly or by a posterior approach. The posterior approach allows the patient to be blinded from the procedure, and it mimics the approach used in arthroscopy of the joint.

Indications of Shoulder Arthrocentesis

Diagnosis

• Acute monoarticular [that affects a single joint] arthritis
• Suspected infection (eg, septic arthritis)
• Inflammatory joint effusion
  • Gout
  • Pseudogout
  • Rheumatologic disorders
  • Reactive arthropathies

Therapeutic

• To relieve a large painful effusion.
• Instillation of medications
• Repeated arthrocentesis for septic arthritis in carefully selected patients as a means of decreasing bacterial load

Contraindications

• Cellulitis in the overlying skin
• Overlying skin lesions (eg, dermatitis or psoriasis)
• Known bacteremia
• Bleeding disorders
• Patient on anticoagulation medication

Relevant Anatomy

The glenohumeral joint of the shoulder is formed by the humeral head and the glenoid fossa of the scapula.

Detailed anatomy of the shoulder joint

Procedure of Shoulder Arthrocentesis

• Shoulder joint can be approached posteriorly or anteriorly. The patient should be seated in a comfortable position.
  • For the anterior approach, the hand of the patient should rest lap so that the shoulder is internally rotated.
  • If the posterior approach is contemplated, rest the patient’s hand on the affected side on the contralateral shoulder.
• Palpate and mark the needle insertion site according to the approach chosen
• Anterior approach
  • Palpate the coracoid process and the humeral head.
  • With the arm in internal rotation [internal rotation is achieved by placing the hand in the lap of the patient.], the joint space can be felt as a groove lateral to the coracoid process.
  • Direct the needle slightly laterally and superiorly into the glenohumeral joint space.
• Posterior approach
  • The needle is inserted 1-2 cm inferior and medial to the posterior tip of the acromion [and directed anteriorly and medially toward the coracoid]

• Prepare the part according to the entry site chosen. Povidone iodine and alcohol solution can be used for part preparation. Part preparation is done to sterilize the skin surrounding the insertion site and allow it to dry
• Administer the local anesthesia using 1% or 2% lidocaine.
• The joint is aspirated using 18 gauge or thicker needle. Advance the needle while keeping a pull on the plunger of the syringe until synovial fluid is obtained. The amount if the fluid aspirated would depend on the size of the effusion or intended investigation.
• In case the shoulder is accessed for injection, after aspirating the fluid, stabilize the needle by holding the hub and remove the syringe part and exchange the syringe for a corticosteroid-filled syringe. After the other syringe is in place, the injection can be carried out.
• Remove the needle after the procedure and apply pressure on the site for few minutes. A small sealant bandage can be applied.
• Divide the fluid among the specimen tubes and send for the required investigation.

For increased accuracy of needle placement, ultrasound imaging may be used to locate the size of aspiration.

Complications

Complications are few and rare. These include the following.

• Hematoma
• Intravascular injection into the axillary vessels
• Infection is possible
• Injection of corticosteroids into a tendon or tendon insertion can cause tendon rupture
• Rise in blood glucose levels in patients with diabetes mellitus in case of corticosteroid instillation.

Wrist arthrocentesis is the procedure of aspirating fluid from wrist joint and is used for diagnosis and therapy of various pathologies of the wrist.

The wrist joint is anatomically complex and can be approached from any side but the dorsal approach is the preferred site for wrist arthrocentesis.

Relevant Anatomy of Wrist Joint

Indications of Wrist Arthrocentesis

Diagnostic

• Acute monoarticular [that affects a single joint] arthritis
• Suspected infection (eg, septic arthritis)
• Inflammatory joint effusion
  • Gout
  • Pseudogout
  • Rheumatologic disorders
  • Reactive arthropathies

Therapeutic

• To relieve a large painful effusion.
• Instillation of medications
• Repeated arthrocentesis for septic arthritis in carefully selected patients as a means of decreasing bacterial load

Contraindications

• Cellulitis in the overlying skin
• Overlying skin lesions (eg, dermatitis or psoriasis)
• Known bacteremia
• Bleeding disorders
• Patient on anticoagulation medication

Procedure of Wrist Arthrocentesis

• The patient should be in a comfortable supine position and the wrist should be palmarflexed. Placing a rolled towel or sandbag under the wrist would help.
• Identify and mark the landmarks and prepare the part with povidone-iodine solution or alcohol solution
• For local anesthesia, infiltrate the skin and subcutaneous tissues with 1% or 2% lidocaine. Topical ethyl chloride may be used.
• Insertion of the needle
  • Dorsally just distal to the radius and just ulnar to the anatomic snuff-box –  Avoid extensor carpi radialis brevis and extensor pollicis longus tendons. Direct the needle perpendicular to the skin. If the bone is hit, pull the needle back and redirect it slightly toward the thumb.
  • Radial entry – The hand and wrist are relaxed in a slightly flexed position. The joint space can be located by palpating the edge of the distal radius just medial to the thumb extensor tendon.
    Ulnar deviation widens the joint space.
• Another approach is from the ulnar side. Keeping the wrist in the same relaxed position, the joint space can be identified by palpating just distal to the distal ulna. The 22-gauge needle is directed in a volar and radial direction.
• Bedside ultrasonography may be useful as an adjunct for joint aspiration by helping to localize the optimal site for needle placement.
• A pop or give way is felt as the needle enters the joint.
• The fluid could be withdrawn now. The ease of withdrawal is determined by the needle size, the viscosity, amount of fluid and the presence of any fibrin clots.
• If the fluid cannot be withdrawn, rotating the needle, withdrawing it slightly, or even reinjecting a little of the fluid often helps unclog the needle and allows additional fluid to be withdrawn. The bore of the needle used may be varied depending on the viscosity of the fluid to be withdrawn.
• After the procedure is done and the sample is taken the needle is withdrawn. In therapeutic cases where injections are to be given, the only syringe is removed keeping the needle secure in the place and the desired medication injected.
• At the end of any injection procedure, the needle should be swiftly withdrawn, and light pressure should be put on the needle site in the skin.

Complications of Wrist Arthrocentesis

Infection is a small but significant risk. Sterile technique minimizes the risk. In cases where risk is gauged higher, the patient may be put on prophylactic antibiotics.

The estimated risk of septic arthritis following aspiration or corticosteroid injection is estimated to be between 1 in 2000.

Tendon rupture and nerve injuries are even rare and often result from misplaced needles.

Ankle arthrocentesis like other joint aspirations could be diagnostic or therapeutic. A good knowledge of ankle joint helps to perform the arthrocentesis more efficiently and safely.

Relevant Anatomy of Ankle Joint

The ankle joint is a hinged synovial joint formed by talar bone, tibia, and fibula. Plantar flexion and dorsiflexion are the main movements of the ankle joint.

[Detailed anatomy of ankle joint]

Indications of Ankle Arthrocentesis

Diagnostic

• Acute monoarticular [that affects a single joint] arthritis
• Suspected infection (eg, septic arthritis)
• Inflammatory joint effusion
  • Gout
  • Pseudogout
  • Rheumatologic disorders
  • Reactive arthropathies

Therapeutic

• To relieve a large painful effusion.
• Instillation of medications
• Repeated arthrocentesis for septic arthritis in carefully selected patients as a means of decreasing bacterial load

Contraindications

• Cellulitis in the overlying skin
• Overlying skin lesions (eg, dermatitis or psoriasis)
• Known bacteremia
• Bleeding disorders
• Patient on anticoagulation medication

Procedure of Ankle Arthrocentesis

• The patient is either in the sitting position or supine on a stretcher, with the knee flexed at 90º. The leg may hang from the side of the stretcher or bent with the heel resting against the stretcher.
• After skin preparation, draping, and identification of the needle insertion site, lidocaine 1% is used as local anesthetic into the subcutaneous tissue.  Be careful not to go too deep or otherwise the anesthetic agent could be instilled in the joint. Anxious and uncooperative patients may need sedation.
• Anterolateral approach
  • Preferred approach
  • Avoids potential injury to the dorsalis pedis and posterior tibial vessels or the deep peroneal nerve. These structures course through the medial aspect of the ankle and foot.
  • The needle is inserted at the joint line midway between the base of the lateral malleolus and the lateral border of the extensor digitorum longus, advancing the needle perpendicular to the fibular shaft.
• Anteromedial approach
  • Identify the ankle joint line, the medial malleolus, and the tendons of the extensor hallucis longus and the tibialis anterior. [To avoid injury to both the dorsalis pedis vessels and the deep peroneal nerves, remember these structures are immediately below and lateral to the extensor hallucis longus tendon.
  • Identify the space
    • Between the medial border of the extensor hallucis longus and the lateral border of the tibialis anterior or
    • Between the base of the medial malleolus and the medial border of the tibialis anterior.
  • Insert a needle at either insertion point in either of the spaces and advance the needle perpendicular to the tibial shaft.
• Repeated flexion/extension movement by the patient helps identification of the spaces in either approach.
• Inverting and plantar flexing helps to identify space in anteromedial approach
• Using a sterile technique, attach the 18- or 20-gauge needle to the 20-mL syringe, and pull the plunger to break resistance.
• Insert the needle into the joint space while gently aspirating until synovial fluid enters the syringe (usually 1-2 cm)
• If a bone is encountered, pull the needle back, verify the anatomic landmarks and readvance the needle in a corrected direction.
• If removal of more fluid is desired, a hemostat can be used to secure the needle in place while the syringe is replaced with a new one.
• Remove the needle and apply a bandage.
• Divide the aspirated synovial fluid into the different specimen containers for synovial fluid analysis

Complications of Ankle Arthrocentesis

Dry tap

Dry tap causes are

• Improper needle placement
• Small amount of effusion
• Mechanical obstruction of the needle against cartilage
• Thickened synovium

Cartilage Injury

Infection

Intravenous antibiotics should be given immediately following the procedure when the infective focus is suspected.

Elbow arthrocentesis refers to puncture of the elbow joint and the aspiration of its synovial fluid. It is used for synovial fluid analysis to aid in diagnosis and also for therapeutic purposes. Analysis of the removed fluid helps to reach at its etiology.

Anatomy of Elbow Joint

Elbow region is the connecting region between arm and forearm. Elbow joint is formed by the lower part of the humerus, radius bone and upper part of the ulna.

Indications of Elbow Arthrocentesis

Diagnosis

• Acute monoarticular [that affects a single joint] arthritis
• Suspected infection in an elbow (eg, septic arthritis)
• Inflammatory elbow joint effusion
  • Gout
  • Pseudogout
  • Rheumatologic disorders
  • Reactive arthropathies

Therapeutic

• To relieve a large painful effusion.
• Instillation of medications
• Repeated arthrocentesis for a septic elbow in carefully selected patients as a means of decreasing bacterial load

Contraindications

• Cellulitis in the overlying skin
• Overlying skin lesions (eg, dermatitis or psoriasis)
• Known bacteremia
• Bleeding disorders
• Patient on anticoagulation medication

Procedure of Elbow Arthrocentesis

• Place the patient sitting upright on a stretcher. Sedated patients should be in the supine or lateral position.
• Prepare the skin with povidone-iodine solution or chlorhexidine
• Using 1% lignocaine, make a small wheal with a small (25-gauge) needle in the dermis at the determined entry point for aspiration for local anesthesia. Alternatively, a topical vapor coolant, such as ethyl chloride, may be sprayed. Sedation may be used in uncooperative patients but rarely needed.
• With elbow bent to 90 degrees, pronate the patient’s forearm, and rest it with the palm down on a side table.
• Identify the following landmarks. The landmarks may be easier to find if the arm is first extended.
  • Olecranon process
  • Lateral epicondyle
  • Radial head
• Identify the depression  [bulge in the large effusion] in the triangle formed by these landmarks. This is the site for entry.
• In smaller effusions, ultrasonography may aid detection of even a small effusion.
• Identify the site of entry, and insert an 18-gauge needle into the depression. It could be done in two ways
  • Lateral Approach – The needle is perpendicular to both the skin and radial head from the lateral side. This is the lateral approach and the preferred one.
  • Posterolateral approach – Insert the needle perpendicular to the skin but parallel to the radial shaft.
• Advance the needle slowly while aspirating the syringe until synovial fluid is obtained.
• If the aspiration is unsuccessful, draw back, reidentify the landmarks, and correct the needle insertion position. If the bone is encountered, withdraw the needle slightly and redirect it.
• After the procedure is done, remove the needle and dress the puncture site.
•  Place the fluid in specimen tubes and send for analysis.

Complications of Elbow Aspiration

• Infection – Rare but occurs due to the introduction of bacteria from the skin.
• Hemarthrosis
• Allergic reaction to the anesthetic agent
• Reaccumulation of the joint fluid.

Read about Synovial Fluid Analysis

Synovial fluid analysis is often done to aid in the diagnosis of joint inflammation, pain, swelling, and/or fluid accumulation. It is withdrawn from the joint by a procedure called arthrocentesis.

What is Synovial Fluid?

The synovial fluid or joint fluid is present in all joints or diarthroses. The articular surfaces of the synovial joints are covered by articular cartilage and are separated from each other by a small cavity that contains the synovial fluid.

The synovial joint has a joint capsule which contains specialized secretory cells termed synoviocytes (types A and B). These produce the components of the synovial fluid and contribute to the local production of cytokines, small-molecule mediators of inflammation, and proteolytic enzymes.

Synovial fluid also provides the nutrients and lubrication for the joints.

Biochemically, the synovial fluid is an ultrafiltrate of plasma.

In normal physiological conditions, the biochemical composition of the synovial fluid is similar to that of plasma.

This composition changes in various diseases and results in gross, microscopic, biochemical and cytological changes in the fluid. These changes can be analyzed and information can be deduced from the values generated in the analysis.

Typical characteristics of synovial fluid

Physical characteristics

• Appearance –  clear
• Viscosity –  high
• Moderately viscous – drops of it from a syringe needle will form a “string” a few inches long.

Chemical Analysis

• A small amount of glucose and protein.
•  Glucose level is similar to that of the patient’s serum glucose level

Microscopic examination

• Few white blood cells (WBCs< 200/ µL) and red blood cells
• No microbes or crystals present
• Polymorphonuclear neutrophils (PMNs< 25% )

Pathologies Affecting Joints – Indications for Synovial Fluid Analysis

Diseases and conditions affecting joint(s) and the synovial fluid can be divided into four main categories:

Infections

These could be caused by bacteria, fungi, or viruses. Infection of the joint results in acute and chronic septic arthritis.

Bleeding

Bleeding disorders and/or joint injury can lead to blood in the synovial fluid

Inflammatory diseases

• Conditions that cause crystal formation and accumulation such as gout and pseudogout
• Conditions that cause joint inflammation, such as synovitis, or other immune responses. These may include autoimmune disorders such as rheumatoid arthritis and lupus.

Degenerative diseases

Osteoarthritis

Collection of Synovial Fluid

Synovial fluid is collected via arthrocentesis or joint aspiration. The collected volume depends on the size of the joint and the necessary tests. Normal joint contains few ml of joint fluid but this quantity increases in the presence of inflammation.

Depending on the test, different types of preservatives are required, as follows:

• Sterile heparinized tubes for microbiology testing
• Heparinized or EDTA tubes for cell count
• Without preservatives for most chemistry tests
• NaF for glucose testing

Powder preservatives or powdered gloves should not be used for sample collection as they can introduce particulates that could interfere with the synovial crystal analysis

Synovial Fluid Analysis – Abnormalities and Interpretation

Lab evaluation of synovial fluid involves the following three steps

• Physical examination like appearance, color, viscosity etc
• Chemical analysis like glucose, total protein level, uric acid etc
• Microscopic evaluation like cell count and differential count, crystal identification etc

Additionally,  microbiologic, serologic, and cytologic laboratory evaluations can be done.

Changes in the appearance of synovial fluid

Changes in the physical characteristics may provide clues to the disease present, such as:

• Decreased viscosity may be seen with inflammation. Viscosity decreases because of decreased production and polymerization of hyaluronic acid. A string 4-6 cm of synovial fluid between the tips of the fingers is normal.
• Cloudy synovial fluid may indicate the presence of microbes, white blood cells, or crystals.
• Reddish synovial fluid may indicate the presence of blood.
• Inflammatory diseases of nonimmunologic origin: Cloudy/turbid, dense yellow with crystals
• High number of crystals are present: Milky/cloudy

Changes in the biochemical composition of synovial fluid

In normal circumstances, the concentration of most of the analytes of synovial fluid is the same as that in serum.

For accurate interpretation of synovial fluid laboratory results, serum samples should be concomitantly evaluated.

Glucose is significantly decreased in inflammatory conditions. These include

• Immunologic disorders
• Lupus
• Scleroderma
• Crystal-induced arthropathies [gout and pseudogout]
• Rheumatoid arthritis
• Septic arthritis

Samples used for glucose evaluation should be collected in NaF [sodium fluoride] tubes to prevent rapid glycolysis and should be tested within 1 hour after collection. Otherwise, a falsely decreased glucose concentration is obtained.

Total protein concentration in synovial fluid is lower than in serum, usually one-third of that in serum. However, this concentration increases in inflammatory and hemorrhagic disorders.

Presence of increased uric acid indicates gout and confirmation is done by a high number of uric acid crystals in synovial fluid.

Cell counts in synovial fluid analysis

Increased WBC count [normal 200 cells/µL] indicates  infections/inflammation. Gram stain and culture can be used for differential diagnosis.

• Total cell counts— the number of WBCs and RBCs in the sample Increased WBCs are seen in infection and in conditions such as gout and rheumatoid arthritis.
• Increased number of neutrophils –  bacterial infections.
• > 2% eosinophils may suggest Lyme disease, parasitic arthritis, rheumatoid disease, or tubercular arthritis.

Microscopic evaluation of crystals in synovial fluid

• Monosodium urate
  • In gout
  • Crystals needle-shaped
  • Negative/yellow birefringence in the compensated polarized light.
• Calcium pyrophosphate (CPP) crystals
  • Pseudogout
  • Rhombic-shaped
• Positive/blue birefringence in the compensated polarized light.
• Cholesterol crystals
  • In hyperlipoproteinemia and rheumatoid arthritis
  • Rhombic and have negative/yellow birefringence in the compensated polarized light^.
• Corticosteroids crystals
  • Seen in patients treated with intra-articular injections of corticosteroids.
  • Flat, small, and have different shapes
  • Can have both positive/blue and negative/yellow birefringence
• Calcium phosphate crystals [apatite]
  • Degeneration and calcification of cartilage and osteoarthritis.
  • Coffin-lid shaped
  • No birefringence

• Calcium oxalate crystals
  • In renal diseases or dialysis.
  • Envelopes or pyramid shaped
  • Negative/yellow birefringence

 Further Lab Studies for Infection

When infection is suspected, the synovial fluid may be subjected to special investigations. These are

Gram stain

This involves staining the smear of the fluid on the slide with Gram’s stain and direct observation of bacteria or fungi under a microscope.

Normally, there should be no microbes present in synovial fluid.

Culture and Sensitivity

To determine the type of microbe and its susceptibility to different drugs.

AFB Staining and Culture

To investigate the presence of tuberculosis. Molecular tests like PCR are also methods for Mycobacteria tuberculosis detection.

Joint aspiration or arthrocentesis is the procedure by which joint fluid is withdrawn using a needle. The fluid withdrawn is used in diagnostic tests. Arthrocentesis could also be used for therapeutic purposes.

Analysis of the joint fluid can enable the physician to differentiate between various joint pathologies.

Joint aspiration is a quick, inexpensive procedure and can be performed in outpatient settings.

Some deep joints like hip joint or joints of the spine should be aspirated under ultrasonographic guidance for improved accuracy.

Indications for Joint Aspiration

For diagnosis

Joint aspiration should be considered for any patient with an inflamed joint [red, warm, tender, swollen, and painful] ] or joints who do not have an established diagnosis. In cases of prosthetic joint infections also, joint aspiration should be performed

For Treatment

Repeated aspirations can be used to relieve discomfort and prevent joint damage and is considered as part of the management of a septic joint.

Aspiration in cases of hemarthrosis can prevent adhesions.

Aspiration can be performed immediately prior to injecting intra-articular medications.

Contraindications for Joint Aspiration

Unless there is a strong suspicion of septic arthritis, a needle should not be passed through an area of infection (eg, overlying cellulitis)  to avoid seeding of infection.

Patients who are on anticoagulant therapy or have a bleeding condition like hemophilia or thrombocytopenia are at increased risk for hemarthrosis with arthrocentesis. Whenever possible, aspiration should be delayed until the coagulopathy is reversed.

Different Gauges of Needles to be Used

• 1.5-in. 21- to 18-gauge needle for large joints  like, knee, ankle or shoulder
• 1-in. 21-gauge needle for medium joints like wrist
• 1-in. 25-gauge needle for small joints  metacarpophalangeal or metatarsophalangeal
• Longer needles if needed for deep joints or very obese patients
• A larger needle size may be selected if a large effusion is noted or if purulent fluid or hemarthrosis is known or suspected

Procedure of Joint Aspiration

The joint landmarks are palpated, and the insertion point is marked with ink.

The area is prepared with povidone-iodine solution and allowed to dry.

The iodine can then be wiped away from the needle insertion site with an alcohol pad to prevent irritation.

Chlorhexidine can be used in patients allergic to iodine.

If desired, 1% lidocaine without epinephrine can be instilled into the skin and subcutaneous tissue. Some surgeons prefer using spray.

The position of the patient may be lying or sitting, depending on the joint and preferences of the surgeon.

The joint to be aspirated is positioned depending on the joint type.

Some Important Tips

• If no fluid or only a small amount of fluid is encountered
  • Move needle slightly further in the joint
  • Thicker fluid/clogged debris – use wider bore needle
• Syringe fills and there is more fluid is still in the joint
  • Change the syringe without removing the needle from the joint and without disturbing the needle’s position.

Arthrocentesis of Different Joints

Shoulder

The shoulder joint is usually aspirated in the sitting position. With the patient in a seated position, the arm is held comfortably at the patient’s side and externally rotated. The coracoid is palpated, and the needle is inserted approximately 1.5 in. laterally and 1.5 in. inferiorly.

Alternatively, the shoulder can be approached posteriorly by inserting the needle inferior to the acromion.

Wrist

The wrist is held in a straight line with the forearm. A dimple is palpated dorsally over the radiocarpal joint, which serves as the entry point for the needle. The needle is held perpendicular to the forearm and inserted dorsally.

Elbow

With the elbow in 90° flexion. The olecranon process, the lateral epicondyle, and the radial head are palpated. The needle is then inserted laterally into the triangle formed by these three structures.

Metacarpophalangeal joint

With the finger flexed, the needle is inserted dorsally and either medial or lateral to the extensor tendons.

Knee

The knee is slightly bent and the needle is held perpendicular to the leg. The needle is inserted medially beneath the patella at approximately the 2 to the 3-o’clock position.

A lateral approach is also used in some cases.

if required, the prepatellar pouch can be emptied by gently applying pressure and squeezing the soft tissues.

Ankle

The ankle is held at 90° or slightly plantarflexed. A space medial to the tibialis anterior tendon or space palpated between the lateral malleolus and extensor digiti minimi can be used to approach the joint.

Metatarsophalangeal joint

The toe is held slightly flexed. The needle is inserted dorsally and either medial or lateral to the extensor tendons.

Complications of Joint Aspiration

Dry Tap

• Improper needle placement
• Small amount of effusion
• Mechanical obstruction of the needle against cartilage or thickened synovium

Cartilage Damage

Can be avoided by understanding the joint anatomy and avoiding further advancement of the needle into the joint space once synovial effusion enters the syringe.

Hemarthroses

• Usually small and self-limited
• and can be managed with observation alone.

Infection

With aseptic technique, the risk is negligible. In case the infection has occurred, it needs to be treated with antibiotics. Prophylactic antibiotics can be given where there is an increased risk of infection.

Analysis of Joint Fluid

Similar to other body fluids, common laboratory evaluation of synovial fluid involves

• Physical examination
• Chemical analysis
• Microscopic evaluation
• Microbiologic and  serologic  evaluations
•  Cytology examination

Different types of preservatives may be required, as follows:

• Sterile heparinized tubes for microbiology testing
• Heparinized or EDTA tubes for cell count
• No preservatives for most chemistry tests
• Sodium fluoride NaF for glucose testing

Thromboprophylaxis stands for prophylactic measures to decrease the risk of venous thromboembolism by measures that promote venous outflow from the legs and drugs that reduce thrombosis.

Venous thromboembolism which encompasses pulmonary embolism and deep vein thrombosis is a major cause of morbidity and mortality in hospitalized patients.

Thromboprophylaxis is the most effective strategy to reduce morbidity and mortality from venous thromboembolism because thromboembolism is often asymptomatic and unrecognized initially.

Risk factors for venous thromboembolism in surgical patients

The risk of venous thromboembolism is determined by patient characteristics and the clinical setting. They include

• Medical illnesses
• Obesity
• Previous history of venous thromboembolism
• Age over 60 years
• Prolonged immobilization
• Lower limb paralysis
• Hormonal therapy like oral contraceptives or hormone replacement therapy
• Stroke
• Congestive heart failure
• Recent myocardial infarction.
• Biochemical abnormalities
  • Deficiencies of antithrombin, protein C or protein S
  • Activated protein C
  • Antiphospholipid antibody syndrome
  • Myeloproliferative disorders
    • Essential thrombocythemia
    • Polycythemia rubra vera
    • Paroxysmal nocturnal hemoglobinuria
  • Major surgeries
  • Orthopedic surgery of the lower limbs
    • Hip arthroplasty
    • Knee arthroplasty
    • Surgery for hip fractures
  • Cancer surgery for cancer
  • Neurosurgery
  • Acute spinal cord injury
  • Multiple trauma
  • Deep system venous disease.

Pathophysiology of venous thrombosis

Venous thrombi usually develop at sites of slow or disturbed blood flow and begin as small deposit of platelets, fibrin, and red cells in valve-cusp pockets or in the intramuscular sinuses of the veins of the lower limb.

As the thrombus grows, it occludes the lumen of the vein, producing venous stasis, and then extends both proximally and distally as a coagulation thrombus composed of red blood cells with interspersed fibrin.

Patients are predisposed to venous thrombosis when fulfilling the elements of Virchow’s triad

• Venous stasis
• Endothelial injury

Venous stasis occurs secondary to long periods of immobilization before or during surgery and limited, or impaired postoperative ambulation.

Endothelial injury can be caused by either direct trauma to the deep tissues or indirectly by hematoma formation and thermal injury (during surgery from cautery or during cement polymerization).

Principle of Thromboprophylaxis

The prophylactic are directed at one or more of these pathogenic factors

• Anticoagulants that counteract blood coagulation
• Drugs that suppress platelet function and the interaction of platelets with the damaged vessel wall
• Mechanical devices that prevent venous stasis.

Oral Anticoagulants

Warfarin Sodium

Oral anticoagulant prophylaxis using warfarin sodium is effective for the prevention of venous thromboembolism in patients undergoing elective hip surgery and in patients who sustain a fracture of the proximal femur.

It causes a reduction in the frequency of both venous thrombosis and pulmonary embolism.

The simplest way to use this medication is to administer 10 mg orally the night before surgery [some prefer to start on the first postoperative day]  followed each day by an appropriate dose to maintain an international normalizing ratio between 2 and 3. The use of warfarin sodium can be problematic, however, if there is a surgical delay. Furthermore, the risk of bleeding complications has limited the acceptance of oral anticoagulant prophylaxis.

Unfractionated Heparin or Heparin

Although it is effective in high risk general surgical patients, prophylaxis with low dose subcutaneous heparin is relatively ineffective for preventing venous thromboembolism in orthopedic patients. In patients undergoing surgery for a fractured hip, prophylaxis with low-dose heparin does not appear to reduce the frequency of large thrombi in the popliteal or femoral veins.

Low Molecular Weight  Heparin

Low- molecular- weight heparins (LMWHs ) represent a newer pharmacological agent for prophylaxis and treatment of venous thromboembolism. Heparin acts via binding to antithrombin III, a natural inhibitor of the clotting cascade, and heparin-antithrombin III complexes act to inhibit factors Xa and IIa (thrombin).

LMWH can either be given preoperatively or postoperatively.

If it is started preoperatively, needle placement should occur 10 to 12 hours after the last dose of LMWH, with subsequent dosing delayed at least 2 hours after needle placement.

With the postoperative regime, the epidural catheter should be left indwelling overnight and removed the following day. The first dose of LMWH can be administered 2 hours after catheter removal.

Fondaparinux

The interaction of heparin and LMWH with antithrombin is mediated by a unique pentasaccharide sequence found on one-third or one-fifth of the chains of UFH and LMWH.

Fondaparinux is a synthetic analog of this naturally-occurring pentasaccharide sequence which also acts as an anticoagulant by binding antithrombin.

Fondaparinux exhibits excellent bioavailability after subcutaneous injection and is given once daily. But treatment with fondaparinux is costly.

To avoid bleeding complications following approaches are used

Dextran

Dextran is a glucose polymer that was introduced as a volume expander and subsequently evaluated as an antithrombotic agent.

Two types of dextran polymer have been used clinically:

• Dextran 70
• Dextran 40

The antithrombotic properties of dextran have been attributed

• Decreased blood viscosity
• Decreased platelet reactivity with the damaged vessel wall
• Decreased platelet aggregation
• Increased susceptibility to fibrinolysis of the fibrin clots.

The major side effect of dextran is volume overload, which may result in cardiac failure, particularly in elderly patients with limited cardiac reserve.

Antiplatelet drugs

Acetylsalicylic acid or Aspirin

This inhibits platelets by permanently acetylating cyclooxygenase-1, the enzyme involved in the first step in the synthesis of thromboxane A₂, a potent platelet agonist.  Role of aspirin prophylaxis in patients undergoing hip fracture surgery remains controversial because of the inconsistent findings trials.

Thienopyridines

This group includes ticlopidine and clopidogrel, irreversibly inhibit platelet ADP receptors. Both agents must undergo hepatic transformation to generate metabolites that inhibit these receptors. Consequently, their onset of action is delayed unless loading doses are given.

Clopidogrel is replacing ticlopidine because of safety and convenience advantages. Unlike ticlopidine, clopidogrel is not frequently associated with neutropenia, thrombocytopenia and thrombotic thrombocytopenic purpura.

Physical Methods

• Elastic stockings
• Intermittent pneumatic compression of the
• Plantar venous plexus (foot pumps) for deep vein thromboprophylaxis

Thromboprophylaxis in various clinical settings

LMWH or warfarin should be given for at least 10 days. Patients with risk factors for venous thromboembolism or those who are not mobile should receive prophylaxis with LMWH or warfarin for 30 days.

Arthroplasty

The incidence of venographically-detected deep vein thrombosis is 51% in patients in patients of elective hip arthroplasty and 61% of knee arthroplasty.

LMWH or warfarin are drugs of choice. Low dose unfractionated heparin is not recommended.

Low molecular weight heparin or LMWH is started 12–24 hours after operation and is given once or twice daily thereafter. Warfarin is started the evening after the operation, and the dose is titrated to achieve an INR of 2–3.

Because LMWH produces rapid anticoagulation, the risk of bleeding is higher.

Elastic stockings or intermittent pneumatic compression does not reduce the incidence of proximal DVT in patients who undergo elective hip arthroplasty, although both modalities lower the rate of calf DVT.

Mechanical methods can be combined with low molecular weight heparin or warfarin but are not effective alone.

Fondaparinux also is effective in patients undergoing elective hip arthroplasty but is expensive

In knee arthroplasty too, LMWH and warfarin are the prophylactic agents of choice though both are less effective than elective hip replacement prophylaxis. This primarily reflects their relative inability to reduce the rate of distal DVT in knee surgery patients.

Surgery for hip fracture

Thromboprophylaxis in patients with hip fracture is difficult. Patients are elderly and have multiple medical problems that increase their risk of bleeding.

Surgery is often delayed and prolonged immobilization further predisposes these patients to venous thromboembolism.

At present, however, LMWH or warfarin is most often used for thromboprophylaxis in patients undergoing surgery for hip fracture.

Acute spinal cord injury

Patients with acute spinal cord injury have the highest rate of DVT among all hospital admissions

Spinal cord injury patients remain at risk for thrombosis for at least 3 months, particularly if the injury is complete.

LMWH is the best form of prophylaxis. Thromboprophylaxis should be continued into the rehabilitation phase. LMWH or warfarin can be used for extended prophylaxis.

Intermittent pneumatic compression or elastic stockings may be considered if anticoagulants are contraindicated early after injury.

References

• Geerts W, Heit JA, Clagett GP, Pineo GF, Colwell CW, Anderson FA Jr, et al. Prevention of venous thromboembolism. Chest 2001;119:132S-175S.
• Stratton MA, Anderson FA, Bussey HI, Caprini J, Comerota A, Haines ST, et al. Prevention of venous thromboembolism: adherence to the 1995 American College of Chest Physicians Consensus Guidelines for Surgical Patients. Arch Intern Med 2000;160:334-40. [
• Nurmohamed MT, Rosendaal FR, Buller HR, Dekker E, Hommes DW, Vandenbroucke JP, et al. Low-molecular-weight heparin versus standard heparin in general and orthopedic surgery: a meta-analysis. Lancet 1992;340:152-6.
• Amarigiri SV, Lees TA. Elastic compression stockings for prevention of deep vein thrombosis. Cochrane Database Syst Rev 2000;(3):CD001484.
• Hull R, Raskob G, Pineo G, Rosenbloom D, Evans W, Mallory T, et al. A comparison of subcutaneous low molecular weight heparin with warfarin sodium for prophylaxis against deep vein thrombosis after hip or knee implantation. N Engl J Med 1993;329:1370-6.