Musculoskeletal Joint Interventions

Ultrasonography has been used to guide interventions for several decades. Interventional ultrasonography can be an office-based or bedside technique, or performed in a dedicated suite. Interventional ultrasonography in musculoskeletal medicine is used for diagnostic and therapeutic purposes.

Indications

Fluid aspiration
Biopsy guidance
Targeted injection of therapeutics

Fluid obtained is examined for

Presence of crystals
Cell count
Cell culture
Gram stain

Possible Diagnoses

Crystal-induced arthropathy
Inflammatory arthritis
Noninflammatory arthropathy
Septic arthritis
Tendinitis

In comparison with blind aspiration, the yield of sonographically guided aspirations is significantly higher, particularly in the small joints of the hands and feet. Guided-diagnostic aspirations are therefore more accurate, there is less delay in diagnosis and treatment, and referrals can frequently be avoided.

Analysis of synovial tissue following biopsy can provide valuable insights into

Pathophysiology
Disease status
Treatment effect and prognosis of inflammatory joint diseases

Ultrasound guidance can improve the yield of such biopsies because hypertrophied and hypervascularized synovial tissue can be accurately located. If ultrasound guidance is employed, even small joints will be accessible to biopsy.

Intralesional, Intraarticular, and Tendon Sheath Injections of Steroids and Other Therapeutic Agents

Daily practice in emergency medicine, primary care, orthopedics, physiatry, rheumatology, and interventional radiology
Ultrasound guidance has been reported to improve accuracy of injections as well as clinical outcomes.

Adverse Effects

They include

Tissue necrosis
Tendon rupture

Adverse effects can be avoided if

Steroids are placed correctly within joint cavities, bursae, and tendon sheaths.

Contraindications

Patient with bleeding disorders
Patient on anticoagulants therapy

Preprocedural Evaluation

Typical indications for diagnostic joint aspirations are

Redness
Joint swelling and pain
Remember, joint swelling can be mimicked by swelling of structures outside of the joint such as subcutaneous edema due to heart failure venostasis, lymph edema, and cellulitis.

These etiologies can be readily determined sonographically and an unnecessary joint aspiration can be avoided. Preprocedure sonographic examination can also determine

The joint capsule is distended by material other than synovial fluid.
Proliferative synovial tissue or tophaceous material can distend the joint capsule even if no or very little free synovial fluid is present.
In these scenarios, a “dry tap” would ensue unless saline is injected first (Fig. 18.1).

Fig. 18.1 Dorsal, long axis views centered over joint line of first metatarsophalangeal (MTP) joint in three different patients. All patients present similarly with pain and swelling of the first toe. (A) Shows distension of joint capsule by hyperechoic, crystalline material in a patient with chronic tophaceous gout. No significant amounts of anechoic fluid are seen. This preaspiration image indicates that a “dry tap” can be expected. (B) Shows distension of the joint capsule by synovial tissue in a patient with rheumatoid arthritis. No anechoic free fluid is seen, again indicating a “dry tap.” In (C), hypoechoic synovial proliferation is seen lining the more hyperechoic joint capsule in a patient with inflammatory arthritis. Anechoic free fluid is seen that can be aspirated.
If fluid is detected, the viscosity of this fluid can be estimated sonographically.
Thin, anechoic synovial fluid is readily displaceable with pressure of the probe. Particles of increased echogenicity float around freely in such fluid.
In contrast, fluid that is entrapped chronically in ganglia or bursae becomes gelatinous and is less readily displaceable. Contained particles of increased echogenicity or bubbles do not float freely.
Intraarticular or intrabursal material of higher viscosity is more difficult to aspirate and requires a larger bore needle.

Synovial tissue can be distinguished from synovial fluid by its often higher echogenicity and decreased compressibility. In inflammatory arthritis, Doppler signals may be detected in synovial tissue, but not in synovial fluid if the probe is kept steady.

Room Setup, Patient Positioning, and Equipment

Setup and Positioning

The patient’s joint is positioned between the operator and ultrasound machine’s screen. This allows syringe, joint, and screen to keep in one line of sight (Fig. 18.2).

Fig. 18.2 When arranging a patient and equipment for a guided injection, it is helpful to place the patient and ultrasound screen so that the examiner can see the injection site and ultrasound image without the need to turn the head. This way the injection site can be observed throughout the procedure.
Handling of syringe and following the path of the needle on the screen can be performed without the need for the operator to turn his or her head to the screen and look away from the injection site.
Injections of the hip, knee, ankle, and foot joints can be performed with the patient lying on the examination table.
Injections of the shoulder can be performed with the patient sitting. Rotating stools for both the patient and operator allow for easy positioning during sonographic shoulder evaluation and injection.
For injections of the elbow, wrist, and hand, the extremity can be placed on a table with the patient sitting on a chair.

Equipment

Use linear array transducers for joint injections
A linear high-frequency transducer (between 10 and 18 MHz) is useful to visualize the soft tissues between skin and joint capsule. The same transducer can be used for joint injections.
Particularly in obese patients, lower frequencies and curved array transducers may be required to visualize the deep-seated hip joint.
All necessary equipment must be prepared and positioned within easy reach if the procedure is performed without an assistant.
For a single-operator ultrasound-guided aspiration or injection, a foot switch for the ultrasound machine is helpful to freeze and save images and record video clips during the procedure.
If an assistant is present, he or she can operate the machine and provide the equipment during the procedure.

Preparation of Injection Equipment for Aspirations and Injections

Needles between 18- and 25-gauge are used for both aspirations and injections.

The required length of the needle needs to be determined by measuring the distance from skin to joint capsule during an ultrasonographic examination prior to the procedure.

For injections of shoulders, elbows, wrists, finger joints, knees, ankles and feet, standard needles up to 1.5-inch length are often appropriate.

Injections of hip joints usually require longer needles: spinal needles can be used.

For hip aspirations, 20-gauge needles can be used.
For hip injections without aspiration, a 22-gauge needle is sufficient.

In obese patients, spinal needles may also be required for guided injections of trochanteric bursa and shoulder joints.

27-gauge and 30-gauge needles can be used for injection of local anesthetic agents prior to the actual aspiration or injection.

If larger volumes of joint fluid are aspirated or if a medication is injected after an aspiration, the needle should stay in place in the joint and syringes should be changed using a straight or curved-end hemostat to hold the needle steady and twist off the syringe.

Parker-Pearson needles, grasping forceps, or fine-needle aspiration equipment can be used to obtain tissue samples (Fig. 18.3).

Fig. 18.3 Parker-Pearson needle inserted in target tissue. The opening is marked by an open arrow. Suction of an attached syringe draws tissue into the needle.

Preparation of Skin

Aseptic techniques are used as they are for blind injections.
Iodine and alcohol-based disinfectants are often used.
Ethyl chloride spray can decrease injection site discomfort.

Technique

Perform an ultrasound of the joint and assess for joint effusion and soft tissue thickness between skin and joint capsule.

Once the joint is visualized sonographically, the probe is kept over the joint and the needle is inserted at an angle of 45 degrees or less. The steeper the angle, the less the needle is visible sonographically. This is done in real-time.

The joint capsule is identified as a hyperechoic, fibrous structure and joint fluid appears anechoic to hypoechoic under ultrasound examination. The needle can be advanced into the joint from any approach and fluid can be successfully aspirated, or medication can be injected. The needle does not need to be buried in the joint space (Fig. 18.4).

Fig. 18.4 The difference between palpation guidance and ultrasound guidance of arthrocenteses is illustrated. (A) With palpation guidance, the shortest route between skin and joint space is usually taken for the pass of the needle. (B) Ultrasound guidance using free-hand technique. The joint space is identified sonographically, and the needle is inserted at an angle so that it can be visualized deep to the probe.
The approach can be individualized. An approach that allows passage of the needle from skin to joint with visualization of the length of the needle is typically used.

Shoulder

Positioning

The patient sits on a stool between the operator and screen.
Fluid in the glenohumeral joint is best visualized from a posterior horizontal or transverse view that visualizes the humeral head and glenoid as bony landmarks and the glenoid labrum and fibrous capsule with overlying infraspinatus tendon and fibrous landmarks.
- Fluid can be seen surrounding the fibrous glenoid labrum and distending the capsule.