Chapter 78. Methylene Blue Joint Injection

Trauma can breach the integrity of the joint capsule and result in infection, long-term arthritis, and other serious and potentially permanent morbidity. Synovial joint fluid provides nutrition to the articular cartilage. Loss of synovial fluid without prompt joint capsule closure can lead to cartilage wasting. Additionally, any breach of the joint capsule, especially through dirty skin, can introduce environmental contaminants and risk septic inoculation of the joint. The injection of joints with methylene blue dye is a simple, rapid, and definitive way to assess joint capsule integrity in cases of periarticular trauma where the clinical examination is inconclusive.

Synovial joints, such as those of the fingers, wrist, shoulder, and knee, consist of a fibrous capsule that overlies a thin, delicate synovial membrane (Figure 78-1). The synovial membrane is a highly vascular structure and the site of synovial fluid production. The synovial fluid provides nutritional support to the relatively avascular articular cartilage. Joint capsules contain varying volumes of fluid, and can be greatly expanded under conditions of inflammation or injection.

Methylene blue is a relatively safe and stable deep blue dye used in both chemistry and medicine. It has most frequently been used to treat methemoglobinemia and for marking skin and lymphatic tracts for oncologic surgery. It is readily oxidized, which has been the proposed basis for its vasoconstrictive effects.1 Methylene blue can cause local necrosis without an immune sensitization when injected at full strength directly into tissues.2

The literature regarding the safety of methylene blue, even during direct intradermal injection, is supportive of its use. When used for lymph node mapping (i.e., direct intradermal and intraparenchymal injection), there is consistent evidence of local inflammatory reactions ranging from local wheal and flare (0.5% of patients) to focal erythema with induration (5% of patients).3,4 Superficial tissue toxicity occurred in only 1.25% of patients.4 These reactions were proportional to the concentration of methylene blue dye (ranging from a dilution of 1:1 to 1:7) and the superficiality of the injection.4 Emergency Physicians (EPs) need to be aware of the potential complications arising from its use just as with any drug or dye introduced parenterally or intradermally. The tissue toxic effects are believed to be much less for intra-articular injections than direct intradermal injection.

The primary indication for injecting a joint with methylene blue dye is to assess the integrity of the articular joint capsule (Figure 78-2). This includes any of the following injuries in close proximity to a joint: skin laceration, a visible joint capsule through a wound, an open fracture, extravasation of serous or serosanguineous fluid from a wound, or a traumatic loading of the joint with evidence of a deformity or an acute effusion. The finger, wrist, elbow, shoulder, toe, ankle, knee, and hip (with varying success) joints can all be injected with methylene blue.

There are few contraindications to injecting methylene blue dye into a joint. It should be avoided in patients with a known allergy to methylene blue. Patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency can develop acute reactions as they do not generate sufficient NADPH to efficiently reduce methylene blue to leukomethylene blue. These individuals are prone to methylene blue-induced hemolysis, oxidative hemolysis, and hemolytic anemia. Methylene blue can itself initiate methemoglobin formation. It should not be injected intraspinally or intrathecally.

There are a few relative contraindications to the injection of methylene blue. It should be used cautiously in a patient with a known coagulopathy, especially a factor deficiency, to prevent intra-articular hemorrhage. Consider reversing the coagulopathy before the injection. Methylene blue should not be used if there is a lack of procedural knowledge or skill by the EP. Not all synovial joints can be injected due to structural instability.

Joint Injection is not contraindicated, but often unnecessary, when definitive operative treatment of the joint is indicated. This includes a visibly open joint capsule, a fracture with obvious joint involvement, intra-articular air on radiographs, and an intra-articular foreign body. In many injuries, the articular capsule will be breached but not externally open to the environment if there is no wound tracking to the skin surface. These injuries may present with an acute joint effusion or radiographic evidence of a periarticular fracture with or without intra-articular air. Despite capsular rupture, methylene blue is not helpful in such cases.

• Sterile drapes
• Sterile gloves
• Sterile gown
• Face mask
• Eye protection
• Povidone iodine or chlorhexidine solution
• Sterile gauze
• Sterile dressing or tape
• Sterile saline
• Sterile basin
• Local anesthetic solution (lidocaine 1% or 2%, etc.)
• 25 g or 27 g needles for infiltrating local anesthetic
• 18 g or 21 g needles for joint injection
• 5 mL syringes for local anesthetic injection
• 10 mL syringes for fingers or toe injection
• 30 mL syringes for wrist or elbow injection
• 60 mL syringes for hip, knee, or shoulder injection
• 1% methylene blue dye

A complete history and physical examination should be performed prior to the injection of methylene blue dye. The affected joint should be thoroughly assessed. Inspect the skin overlying the joint for breaks, infection, old scars, prior incisions, superficial lesions, or any wounds. Palpate the joint to identify any warmth, tenderness, or effusion. Evaluate the joint for any crepitation, deformity, ligamentous instability, or limitations in motion.

As with any nonemergent procedure, consent should be obtained from the patient or their representative. Ideally, the consent should be documented in the medical record and signed by the patient. The patient should be consented for both the arthrocentesis procedure (joint injection) as well as for the use of methylene blue.

Position the patient based on the specific joint to be injected and the approach to be used. Expose the joint and surrounding areas. Identify the anatomic landmarks required for proper needle placement. The landmarks may be difficult to identify on a swollen and tender joint. Compare the “affected” joint to the “normal” joint on the opposite side of the body. Identify the joint and a landmark on the normal joint and transfer this to the affected joint. Clean any dirt and debris from the skin. Scrub the needle insertion site with povidone iodine or chlorhexidine solution and allow it to dry. Apply sterile drapes or a clear sterile dressing to maintain sterility of the injection site (Figure 78-3). The rate of infection resulting from intra-articular injections is very low if sterile technique is used.5

A comfortable, relaxed patient will facilitate arthrocentesis, as tense muscles distort the anatomy of the joint and make anatomic palpation more difficult. Oral analgesics for the precipitating injury along with adequate local anesthesia for the procedure are often sufficient. The articular cartilage has no intrinsic pain fibers, but the synovial membrane, joint capsule, and skin are richly innervated. Adequate time should be taken for the infiltration of local anesthetic solution. The subcutaneous injection of local anesthetic solution is often most practical for larger joints such as the knee, shoulder, and hip. A regional block is often easier for small and more distal joints such as the finger and ankle.

Apply anesthesia to the skin and subcutaneous tissue using 1% lidocaine, topical vapor spray, or ice. The administration of some form of local anesthesia is recommended but not required. The most common local anesthetic used is a short-acting injectable anesthetic solution of 1% lidocaine. There is disagreement if the additional needle stick to administer the anesthesia causes as much discomfort as performing the procedure without any anesthesia. This decision is specific to each EP and patient.

Alternative methods of anesthesia include ice and topical vapor coolants. A sterile drape may be placed over the prepped skin and a bag of ice water placed over the drape. Remove the ice water bag and drape after 5 minutes and perform the procedure. Ethinyl chloride topical vapor coolant may be used as an anesthetic. Spray the solution onto the area of skin in which the needle will be inserted. Apply the spray from 6 in. above the skin. Spray until the skin turns white and frosty. This usually takes 5 to 10 seconds. Immediately perform the procedure, as the anesthesia lasts only 30 to 60 seconds.

Because of the aforementioned effects of methylene blue dye, it is common, though not universal, to dilute the dye in normal saline before the injection. Draw up one to two drops of 1% methylene blue dye into an appropriately sized syringe. Fill the remainder of the syringe with sterile saline to dilute the dye. Apply an appropriately sized needle for the joint to be injected onto the syringe.

The Basic Technique

The use of musculoskeletal ultrasound is useful to assist in arthrocentesis and has been shown to have many benefits including greater fluid aspiration and greater novice physician confidence. It does not result in more pain for the patient and takes minimal additional time to perform at the bedside. The reader is referred to an ultrasound technique text for full instruction, but a few important points are included here. Bone will appear hyperechoic and easily differentiated from muscle and subcutaneous tissue. Tendons will appear fibrillar in nature, like a bundle of drinking straws. Joint fluid will appear hypoechoic and dark. The “seagull sign” is a shape that can be seen on most joint images and represents the joint space between the articular surfaces of two opposing bones. It is a V-shaped hypoechoic area surrounded by hyperechoic bone. Once the landmarks are identified, the needle can be inserted with or without ultrasound guidance.

Apply the needle to the syringe and break the resistance. This avoids any sudden and painful movements of the needle within the joint cavity. Stretch the skin over the site where the needle will be inserted. Penetrate the skin briskly with the needle and enter the joint cavity. Gently aspirate synovial fluid to confirm proper needle position within the joint cavity. If bone is encountered, slightly withdraw the needle and re-advance it in a different direction. Grasp the hub of the needle with your finger or a hemostat. Remove the syringe while leaving the needle in place. Attach the syringe filled with the diluted methylene blue onto the needle.

Inject the methylene blue slowly into the joint cavity. There should be no resistance to flow if the needle is within the joint capsule. The injection should not be painful if the needle is within the synovial capsule. Observe the skin wound for extravasation of blue dye while it is being injected into the joint cavity. Remove the needle when the procedure has been completed. Apply a bandage to the skin.

Different joints will accommodate various amounts of injected volume. The knee may allow for 30 mL or more, whereas the finger may accommodate only 1 mL. It is only necessary to inject a minimal amount of dye before extravasation is seen. If the joint capsule is ruptured, a greater amount of fluid can be injected, as it will escape through the breach. In intact joints, the capsule will expand, increasing pressure and resistance to continued injection. There is often visibly swelling of the skin around the injected joint if there is no breach.

Complete a procedure note in the medical record. A sample procedure note is described below:

After informed consent, the skin overlying the_________joint was cleaned and prepped with povidone iodine solution. The skin was anesthetized with (_____mL of_____% lidocaine, ethyl chloride vapor coolant, ice for_____minutes). Using sterile technique, an_____gauge needle was inserted on the (supero-/infero-,medial/lateral/inferior/superior) surface of the joint. It was directed (supero-/infero-,medially/laterally/inferiorly/superiorly). _____mL of fluid was obtained. It was (thin, thick, yellow, clear, straw-colored, bloody, purulent, with debris, without debris). No complications were noted.

The joint was injected with_____mL of sterile saline containing less than 0.2 mL of 1% methylene blue dye. No complications were noted.

Specific Sites

Methylene blue joint injection can be reasonably accomplished at any joint. The concern for joint capsule rupture without concomitant obvious need for operative exploration and fixation is rare in joints other than the knee and fingers. The knee is relatively easy to inject while the fingers are more difficult. Arthrocentesis with methylene blue injection in the knee and finger is discussed below. The principles and techniques described below can be used on any synovial joint for which there is concern of a capsule breach and for which the EP feels competent to perform arthrocentesis. Please refer to Chapter 77 for the complete details of joint arthrocentesis.

Patellofemorotibial Joint (Knee) Arthrocentesis, Parapatellar Approach

Landmarks

The knee joint can be injected in a variety of locations and with the knee extended or flexed. Palpate the borders of the patella (superior, lateral, and inferior) and the patellar tendon (Figures 78-4A & B). Identify the midpoint of the lateral or medial border of the patella (Figure 78-4B). Either of these landmarks may be used as the site for needle insertion.

Patient Positioning

Place the patient supine on a stretcher with the affected knee fully extended.

Needle Insertion and Direction

Insert an 18 gauge needle just below the midpoint of the lateral or medial border of the patella (Figure 78-4C). Direct the needle perpendicular to the long axis of the leg and aimed toward the intercondylar notch of the femur. Advance the needle to a depth of 1 to 2 cm. Inject the methylene blue dye.

Ultrasound Probe Placement

Start with probe placement longitudinally lateral or medial to the patella for a first view of the possible fluid collection. Then change the probe to a horizontal orientation, and rotate the probe like the hand of a clock around the patella 360° to discover the area with the largest anechoic fluid collection.

Remarks

The easiest site for arthrocentesis is the medial parapatellar region. There are no disadvantages to using the medial parapatellar site. The lateral and medial parapatellar approaches are used with high relative success, most likely due to the large joint space and minimal accessory structures. Studies have demonstrated decreased success of the medial midpatellar approach (56%), relative to the lateral midpatellar (76%-93%) or the infrapatellar (71%-85% lateral and 73%-75% medial) approaches.6,7

Metacarpophalangeal Joint Arthrocentesis

The relatively thin dermal and subcuticular layers over the phalanges often make one wonder about deep soft tissue avulsions or lacerations and the potential involvement of the joint capsule. Injection with methylene blue dye is an ideal method to assess joint capsule integrity. The success rate of arthrocentesis is much lower in the phalangeal joints than larger joints. The overlying ligaments and tendons are more prominent and the synovial capsule is smaller. A failure rate of 15% for finger arthrocentesis was found among skilled surgeons, and as high as 32% among first year residents.8 Successful arthrocentesis was highest in the proximal interphalangeal joint compared to the distal interphalangeal joint or carpometacarpal joint of the thumb.

Landmarks

Identify the metacarpophalangeal (MCP) joint and the extensor digitorum tendon (Figures 78-5A & B). The MCP joint can be located just proximal to the prominence at the base of the proximal phalanx of the finger. Identify the extensor tendon by having the patient extend the finger against resistance.

Patient Positioning

Place the patient sitting upright or supine on a stretcher. Pronate the hand and abduct the fingers. Grasp the finger and apply distal traction.

Needle Insertion and Direction

Insert a 22 gauge needle into the dorsal joint space just medial or lateral to the extensor tendon (Figure 78-5C). Direct the tip of the needle toward the center of the joint. Advance the needle to a depth of 0.3 to 0.5 cm. Inject the methylene blue dye.

Remarks

The application of distal traction often causes a depression to appear on both sides of the extensor tendon. These depressions can be used as landmarks for the site of needle insertion into the joint cavity.

Joint Injection

A maximum volume of 1 mL may be instilled into this joint.

The lack of methylene blue extravasation reassures the EP of an intact joint capsule. Extravasation of dye through the injury site is indicative of a ruptured joint capsule. These require exploration, high volume irrigation, and adjunctive medical treatment such as antibiotics. Although some wounds can be closed primarily in the Emergency Department after consultation with an Orthopedic or Hand Surgeon, open joints require management in the operating room.

A minimal amount of methylene blue dye needs to be injected before visible extravasation will occur. Upon injection, if no extravasation occurs, attempt to aspirate fluid. This may be difficult in small joints. Aspiration of blue fluid provides additional confirmation of intracapsular needle placement.

Given the not insignificant rate of ectopic needle placements (i.e., extrasynovial, intraligamentous, or intratendinous), a high index of clinical suspicion should be maintained for a joint capsule rupture, even in the face of a negative study. Clinical intuition and judgment should guide all decisions.

Arthrocentesis with methylene blue dye is a relatively benign procedure. The postprocedural care consists of monitoring for external bleeding and swelling. Musculoskeletal and neurovascular checks should be performed at the area and distal to the joint. Apply a bandage to the injection site. Pain should be minimal and analgesia can be achieved with oral nonnarcotic analgesics alone. In the setting of a significant traumatic injury, the patient may already be receiving opioid analgesics.

Complications are rare and include hemarthrosis, nerve injury, tendon injury, cartilage damage, and infection. External bleeding and nerve damage should be immediately apparent. A hemarthrosis may be insidious and appear with progressive swelling, pain with joint motion, and often without joint warmth. Tendon and cartilage damage may not be apparent for some time and present with joint stiffness or arthritis. Septic arthritis is the most concerning complication, evidenced by swelling, erythema, warmth, pain with range of motion, and systemic symptoms. Cellulitis may also complicate the procedure, appearing some time later with local warmth, erythema, and induration over the site. Please refer to Chapter 77 for a more complete discussion regarding the complications of arthrocentesis.

Synovial joint injection with methylene blue dye provides the EP with a simple, rapid, and definitive method of assessing joint capsule integrity in cases of periarticular trauma. This procedure can determine between repairing a wound and sending a patient home or admitting a patient to the hospital for joint exploration and closure. Joint injection with methylene blue is technically simple with a low rate of complications.