The major peripheral joints can be aspirated safely in the emergency department. Aspiration of the hip and other joints of the axial skeleton usually requires the aid of specialists (orthopedic surgeons or rheumatologists) and the use of ancillary techniques (fluoroscopy and radionuclide scans); therefore, it is not discussed here.
Indications for arthrocentesis are as follows:
- Need to obtain synovial fluid for diagnosis.
- Drainage of hemarthrosis when conservative management is unsuccessful.
- Instillation of local analgesic and anti-inflammatory agents into a joint.
Contraindications to arthrocentesis are as follows:
- Soft tissue infection overlying proposed site of aspiration.
- Uncooperative patient (relative contraindication).
- Severe bleeding diathesis or anticoagulant therapy.
One person can perform arthrocentesis unaided if the patient is cooperative, although an assistant is helpful for handling samples and holding young children.
Positioning of the Patient
See Procedure for Specific Joints, below.
Procedure for Specific Joints
The joint space of the knee may be entered either medially or laterally (Figure 7–26). In either case, the leg should be fully extended, with the patient supine. Pressure on the opposite side of the joint will make the synovium bulge more prominently and assist in directing the needle.
Aspiration of the knee joint. (Reproduced, with permission, from Way LW, ed. Current Surgical Diagnosis and Treatment, 11th ed. New York, NY: McGraw-Hill; 2003.)
From the lateral aspect, the entrance site is at the intersection of lines (extended from the upper and lateral margins of the patella). A 22-gauge, 4-cm (1½-inch) needle held parallel to the bed is directed medially and just deep to the patella and into the suprapatellar space. From the medial aspect, the needle is introduced anteromedially in the space between the patella and the medial condyle. The needle (held parallel to the bed) is advanced upward (toward the undersurface of the patella) and laterally, beneath the patella and into the joint space.
The shoulder joint can be aspirated from either an anterior or a posterior approach. The latter has the advantage of being out of the patient's line of vision.
For the posterior approach, the patient should sit in a chair and face backward (chest against the back of the chair). To open up the joint space and facilitate entry of the needle, the patient should put the arm of the site to be aspirated up against the chest and touch the opposite shoulder. This will adduct and internally rotate the arm. The head of the humerus is palpable posterolaterally. Use a 20- or 22-gauge, 4-cm (1½-inch) needle, and keep it parallel to the floor. Direct it about 30° medially into the joint space from a point just under the posteroinferior border of the acromion (Figure 7–27).
Posterior approach to shoulder joint aspiration.
For the anterior approach, the patient should sit in a chair, facing forward, with the arm comfortably supported in the lap. Using a 20- or 22-gauge, 4-cm (1½ inch) needle, enter the joint space at a spot medial to the head of the humerus and just below the palpable tip of the coracoid process (Figure 7–28). Direct the needle slightly laterally and superiorly into the scapulohumeral joint space.
Anterior approach to shoulder joint aspiration.
Be certain to differentiate olecranon bursitis that does not involve the elbow joint from bulging synovium. Have the patient sit with the forearm supported from the elbow to the hand on a table, with the elbow joint in about 10–30° of flexion. With significant effusion, the bulging synovium should be evident laterally. Introduce the needle (usually a 20- or 22-gauge, 4-cm [1½-inch] needle) just below the lateral epicondyle and proximal to the olecranon process of the ulna (Figure 7–29). Advance the needle medially and slightly proximally into the joint space.
Aspiration of the elbow joint.
Arthrocentesis of the ankle is more difficult than that of the other joints discussed here. The most common approach is anteromedial. Have the patient lie supine, with the knee extended and the foot slightly plantarflexed. Identify the extensor hallucis longus tendon by having the patient extend the great toe. Just anterior (1 cm [⅜ inch]) and inferior (1 cm [⅜ inch]) to the medial malleolus and lateral to the extensor tendon is a small depression. Introduce the needle in this depression and direct it toward the tibiotalar articulation (Figure 7–30). If swelling and pain are most severe on the side of the ankle, use a similar approach but from the anterolateral aspect of the joint. When subtalar disease is suspected (eg, pain on pronation and supination of the foot), the needle is introduced more distally, at the talonavicular articulation. Although fluid is seldom obtained at the talonavicular joint, injection of anti-inflammatory agents may be readily accomplished.
Determination of the needle entry site for ankle joint aspiration. A small depression can be palpated about 1 cm (½ inch) anterior and inferior to the medial malleolus and lateral to the extensor hallucis longus.
A bulging, inflamed joint space at the wrist can be entered dorsally at prominent areas of swelling; such areas are invariably found on the radial or ulnar aspects. Use a 20-or 22-gauge, 4-cm (1½-inch) needle.
For the radial (lateral) entry, position the hand with the palmar surface down and flex it over a rolled towel at the wrist. Aspirate the joint at the midpoint of the distal articulation of the radius, just medial to the extensor tendon of the thumb. The needle should be perpendicular to the skin during aspiration. The ulnar, or medial, approach is made in the middle of the palpable depression between the lateral aspect of the tip of the ulna and carpus. Position the hand as for a radial approach. Direct the needle ventrally toward the palmar surface and proximally into the joint space.
To administer corticosteroids into the carpal tunnel (to treat compression of the median nerve), place the needle between flexor creases of the wrist just lateral to the palmaris longus tendon (or medial to the flexor carpi radialis) and advance it distally until resistance to injection is minimal. (See Chapter 29 for details.)
Small Joints of the Hands and Feet
Systemic arthritides frequently involve the proximal and distal interphalangeal joints and the first metatarsophalangeal joint. Enter the joint in the midline just lateral to the extensor tendon on the dorsolateral aspect and gently work a 25- or 27-gauge needle into the joint space. A 2-mL syringe suffices for aspiration and is easier to handle than larger ones. Maintain a slight vacuum in the syringe so that any trauma to digital vessels will be recognized immediately (blood will appear in the syringe). Traction on the distal portion of the phalanx helps open the joint space, allowing easier access for the needle.
If minimal fluid is available, priorities must be established for processing the sample. If pyogenic arthritis is a diagnostic possibility, an appropriate approach would be to place one drop of fluid on a microscope slide for Gram stain, another into a hemacytometer for cell count, and the remainder of the sample for culture. If 10–20 mL or more of synovial fluid is obtained, complete synovianalysis can be performed, as outlined below; partial analysis is possible on even as little as 1 mL of fluid.
Determine the total volume of fluid removed.
Assess color and clarity of fluid (normally a crystal-clear yellowish fluid through which print can be easily read).
Note viscosity by allowing a drop to fall from the needle. Normal joint fluid has high viscosity and easily forms a cord several inches long.
Perform the mucin clot test (Ropes test) by adding 1 mL of synovial fluid to diluted acetic acid (about 5%). Normally, the mucin in the fluid congeals within minutes, forming a gel (commonly called a clot) that remains firm for hours. In the case of infection or chronic inflammation, unstable gel forms, which is easily broken up by gentle agitation. Examine the gel again at 1 hour for friability; normal mucin gel should be unchanged after 1 hour.
The choice of studies is guided by clinical circumstances. Gram stain and culture, cell count, and examination for crystal formation should always be performed when fluid from an acutely inflamed joint is being evaluated.
Cell Count and Differential
Place 2–10 mL of synovial fluid in a purple-topped (EDTA anticoagulant) or green-topped (heparin anticoagulant) tube for laboratory examination. If fluid is scanty, use 1–2 drops counterstained with methylene blue and perform a cell count in the emergency department with a hemacytometer. Normal synovial fluid contains fewer than 200 white cells per microliter, of which less than 25% are polymorphonuclear neutrophils.
All joint fluid should be stained with Gram stain and examined by microscopy. Special stains for fungi and acid-fast bacilli should also be performed when chronic monarticular arthritis is being evaluated. These tests are specific but not sensitive for detection of fungal or mycobacterial arthritis.
Placeadropofsynovial fluid on a clean glass microscope slide under a cover-slip. Examine the specimen immediately; if this is impossible, slow the evaporation of joint fluid by sealing the edges of the coverslip with nail polish or petrolatum. Crystals can be detected using light microscopy and tentatively identified on the basis of morphologic characteristics seen at ×400 magnification. Urate crystals are needle-shaped; calcium pyrophosphate crystals are more rhomboid-shaped; and cholesterol crystals are flat, with notched corners. Polarized light microscopy demonstrates the negative birefringence of urate crystals and the positive birefringence of calcium pyrophosphate. The presence of crystals both free in fluid and within leukocytes is pathognomonic of crystal-induced arthropathy. If the laboratory is doing the examination, collect 1–2 mL of fluid in a purple-topped (EDTA anticoagulant) or green-topped (heparin anticoagulant) tube.
Sterile, capped specimen tubes should be filled with 1–10 mL of fluid for bacterial cultures and, if indicated, mycobacterial and fungal cultures. In suspected gonococcal disease, chocolate agar should be inoculated with some of the fluid (in the emergency department if possible). When a potentially infected prosthetic joint is being evaluated, a jar of anaerobic transport media should also be inoculated.
The glucose level of the synovial fluid can be used to determine the possibility a patient's symptoms are related to a septic joint. Place 0.5–1 mL of synovial fluid in a gray-topped (fluoride anticoagulant) tube. The sample must be compared with a simultaneously drawn blood sample. Blood glucose that is more than 40 mg/dL higher than synovial fluid glucose suggests infection.
Place 0.5–1 mL of synovial joint fluid in a red-topped (no anticoagulant) tube. Determine the total serum protein of a simultaneously drawn blood sample. Normal joint protein is about one-third that of serum.
Less commonly indicated studies include cytology studies in possible pigmented villonodular synovitis or metastatic disease (5–10 mL in a lightly heparinized specimen tube); pH determinations (1–2 mL in a sealed heparinized syringe); complement levels; and tests for rheumatoid factor, antinuclear antibody, immunoglobulins, and various enzymes.
The presence of fat globules (often with blood) suggests intra-articular fracture.
Incision and Drainage of Superficial Abscess
A superficial abscess is incised in order to drain it.
There are no contraindications to incision and drainage of a superficial abscess.
One person can usually incise and drain a superficial abscess unaided, although an assistant may be helpful to restrain an uncooperative patient.
Equipment and Supplies Required
Many incision and drainage kits are commercially available. The following items are required:
- Materials for skin cleansing.
- Protective gown, mask, eye protection, and gloves.
- No. 11 surgical blade, mounted.
- Curved Kelly and mosquito clamps.
- Packing material, such as gauze strip packing.
- Sterile gauze sponges, 10 × 10 cm2 (4 × 4 inch2), and tape.
- Ethyl chloride skin-freezing solution (optional).
- Lidocaine, 1%, with 25-gauge needle and 5-mL syringe.
- Culture tube and slides.
- Sterile saline for irrigation.
- Irrigating syringe and basin.
- Needle, 18 gauge, with 5-mL syringe.
- Plastic-coated absorbent pad.
Positioning of the Patient
The patient should be lying on a firm surface in a comfortable position, with the area to be drained in full view and firmly supported.
Anesthesia is the main difficulty in incision and drainage. Superficial abscesses suitable for drainage at the bedside are painful, and the patient should be assured that pain will decrease after the pressure is relieved and the pus is drained. Incising the skin and draining the pus are painful, however, and little relief can be obtained short of general or block anesthesia, both of which require an anesthesiologist and an operating room. Spraying the area with ethyl chloride to freeze the skin will prevent some but not all pain. Infiltrating the thick layer of skin over the pointing abscess with lidocaine is impossible, and injecting lidocaine into the abscess cavity is ineffective and may create more pain from increased pressure. Narcotic analgesics (eg, morphine, 2–10 mg intramuscularly or subcutaneously) may take the edge off the pain and relieve some of the patient's anxiety, but they will not provide total relief.
If an abscess is too large to be adequately drained at the bedside or if it appears that the patient may experience too much pain to be able to cooperate effectively, incision and drainage in the operating room is always an alternative.
Simple Abscess Not Involving a Vital Structure
Assemble the necessary equipment and arrange it on a table or bedside stand.
Position the patient. Place the plastic-coated absorbent pad under the body part with the abscess to be drained.
Don sterile gloves and put on a gown, mask, and eye protection. Cleanse the skin over the area being drained. Drape the area, and have extra absorbent materials ready to catch any pus not absorbed by the drape.
If there is any doubt whether an abscess is actually present, take the 18-gauge needle and the 5-mL syringe and aspirate the suspected abscess at the point of maximum fluctuance. If no pus is found, reassess the clinical situation, and proceed with incision and draining if it is deemed appropriate.
If ethyl chloride or lidocaine is being used, it should be given at this time.
Using the No. 11 blade, open the abscess at the point of maximum fluctuance and allow the pus to drain under its own pressure. Using a quick, decisive motion minimizes the patient's discomfort. Collect the first portion of pus for Gram stain and culture and sensitivity testing.
After the pressure has been relieved, insert the Kelly or mosquito clamp and find the longest axis of the abscess. Point the curve of the clamp up at the farthest point from the central incision and determine the shortest possible length to be incised so that the abscess is completely drained. Incise the skin to that point, using swift upward motion of the No. 11 blade. If it is necessary to make a long incision to completely drain the abscess, infiltrate the skin in the most lateral aspect with lidocaine. Repeat the procedure in the opposite direction. Allow any further pus to drain. Note: It is important to obtain an opening in the abscess wide enough to allow complete drainage of all pus. If the abscess is not opened completely, complete drainage cannot occur, and resolution of the abscess will be delayed.
Using the clamp, break up any loculated pus in the cavity.
Irrigate the abscess with saline until all pus is removed.
Pack the abscess cavity with iodoform or plain gauze packing. Fill the cavity tightly enough to cause hemostasis but not so tightly that it causes pain.
Dress the area with the sterile 10 × 10 cm2 (4 × 4 inch2) sponge and tape. On the extremities or in areas where there is movement, consider dressing the site with an expanded bandage around the extremity.
Begin antimicrobial therapy, if indicated (eg, for facial abscesses, cellulitis). Remember to cover for community-acquired methicillin-resistant Staphylococcus aureus and consider trimethoprim/sulfamethoxazole unless a sulfa allergy exists.
Schedule a follow-up appointment in 1–2 days.
Incision and Drainage of Abscesses over Special Areas
Face, Head, and Neck Abscesses
The clinical situation in these anatomic areas must be carefully considered before incision and drainage is performed, because the large scar left by complete incision and drainage may be cosmetically unacceptable and because of the possibility of injuring vital structures beneath the skin. In small superficial abscesses on the face, drainage can be accomplished by making a small incision at the lower part of the abscess, removing all pus, and leaving a gauze wick in the incision to keep the wound from closing. Frequent irrigation will be needed during follow-up to keep the cavity clean and promote healing. Any abscess that is large or that might involve vital structures should be drained in the operating room by personnel experienced in this procedure.
Make sure that the abscess does not involve the joint space. (Consult an orthopedic surgeon if there is any doubt.) If the abscess is superficial and does not involve the joint space, proceed with incision and drainage. Remember that splinting of the joint is necessary for adequate healing.
Abscesses Around the Anus
Differentiate pilonidal abscesses from perianal abscesses caused by anal fistulas. Perianal abscesses require surgical consultation and possibly drainage in the operating room.
Abscesses of the Hands, Wrists, Ankles, and Feet
The compact arrangement of many vital structures in the hand, wrist, ankle, and foot makes drainage of abscesses in these areas difficult to perform in the emergency department. It is recommended that any abscess around these structures be drained in the operating room by experienced personnel. Surgical consultation is advisable in all cases of abscesses in these areas.