Equipment
Equipment used for ankle arthrocentesis includes the following:
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Sterile gloves and drapes
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Gauze pads (5), 4 × 4 in.
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Skin preparatory solution
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Lidocaine 1%
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Syringe, 5 mL
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Needles, 18 gauge and 25 or 27 gauge
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Syringes, 20 mL, 30 mL, 60 mL
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Needle, 18 gauge or 20 gauge (a patient who is morbidly obese might require a 21-gauge spinal needle for arthrocentesis)
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Hemostat
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Specimen tubes
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Bandage
Patient Preparation
Anesthesia
Patients who are anxious, in severe pain, or unable to cooperate with the procedure might require procedural sedation and/or analgesia. For more information, see Procedural Sedation.
Local anesthesia is warranted. After skin preparation, draping, and identification of the needle insertion site, use a 25- or 27-gauge needle to inject 2-5 mL of local anesthetic (eg, lidocaine 1%) into the subcutaneous tissue. (See the image below.) For more information, see Local Anesthetic Agents, Infiltrative Administration.
Deep injections that might enter the joint space are not recommended, because they may alter the synovial fluid analysis results.
Positioning
The patient should be placed either sitting or supine on a stretcher, with the knee flexed at 90º and the leg either hanging from the side of the stretcher or bent with the heel resting against the stretcher.
Plantarflexion of the ankle against minimal ankle dorsiflexion by the patient helps define the anatomy.
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Right ankle.
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Anatomic landmarks for ankle arthrocentesis. EDL = extensor digitorum longus; EHL = extensor hallucis longus; TA = tibialis anterior.
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Identification of space between medial malleolus and medial border of tibialis anterior tendon.
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Infiltration of local anesthetic.
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Ankle joint aspiration between medial malleolus and medial border of tibialis anterior tendon.
Tables
|
Appearance |
WBC, cells/μL |
Polymorphonuclear (PMN) cells, % |
Glucose concentration, mg/dL |
Protein concentration, g/dL |
Normal |
Clear |
< 150 |
< 0.25 |
Serum glucose |
1.3-1.8 |
Noninflammatory |
Clear |
< 3000 |
< 0.25 |
Serum glucose |
2-3.5 |
Inflammatory |
Cloudy |
>3000 |
< 0.75 |
< 25 |
>4 |
Purulent |
Cloudy |
>50,000 |
>0.9 |
< 25 |
>4 |
Hemorrhagic |
Bloody |
>2000 |
~0.3 |
Serum glucose |
... |
