Part One: Tapping the Wrist
The wrist is not commonly aspirated in the emergency department, but emergent arthrocentesis may be indicated for extreme or concerning cases, and tapping the wrist to determine the underlying pathology or relieve pain may be of great value. The synovial fluid from the joint space can be analyzed for crystals, infection, and blood. This information may help determine the overall plan and aid in decision-making and consultation. The ultimate treatment plan may include admission, intravenous antibiotics, multiple aspirations, and even surgical washout.
A swollen, painful wrist that is hot to the touch is concerning for septic arthritis. Use ultrasound to confirm the proper aspiration site and the angle for the needle during arthrocentesis. This patient had multiple bandages on his fingertips from blood glucose testing, providing an entry for infection and increasing the chance of developing a septic joint.
Joint aspirations carry minimal risk when done properly. They may even have lower morbidity and mortality than those who undergo surgical debridement. (J Bone Joint Surg Am. 2015;97:558; http://bit.ly/2SVs7Dc.) The wrist is complex, and our video highlights the anatomy using ultrasound (US). We suggest a static approach to determine if there is a collection of fluid or an abscess, and then consider US-guided needle aspiration of the joint.
A plain film radiograph should be done, especially if there is a history of trauma. A fracture or foreign body should be ruled out before aspiration is considered. Ask the patient about drug use or possible injection into the forearm, hand, or other joint space. Any history of IV drug use is relevant. It's also important to ask the patient if he has a known history of gout or pseudogout, prior septic joint, surgeries, recent tattoos, prosthetics, or recent steroid injections into the region.
A high-frequency linear probe is used for wrist aspiration. Discover your landmarks using a static approach before donning sterile gloves and setting up. Photo by Martha Roberts.
Diagnostic reasoning for aspiration includes but is not limited to suspicion for septic arthritis, gout, hemarthrosis or effusion, inflammatory or noninflammatory arthritis, and complex (abscess) or simple cellulitis. Other indications include the potential for biopsy or therapeutic fluid drainage for pain relief. Rare underlying diagnoses include amyloidosis, fibromyalgia, and hyperparathyroidism. Consider acute on chronic renal failure or new renal failure. Examine all other joints and look at the pattern of the swelling, warmth, rash, and proximal joint spaces especially. Petechial rash or multiple joint involvement may suggest a more global issue.
Septic Joint Infections
Septic joint infection of the wrist is rare and nefarious. It should not be missed. Typical normal synovial fluid should be clear or straw-colored without any crystals, with a total white blood cell count under 200/mL. Osteoarthritis may have WBC counts in the 1000s, and rheumatoid or other inflammatory arthritis will have 20,000/mL or more WBCs.
Septic arthritis counts will typically be higher than 50,000 WBCs/mL. Regardless of these results, the literature has proven repeatedly that laboratory and synovial diagnostic testing may not provide complete certainty of diagnosis. (J Emerg Med. 2007;32:23.) The erythrocyte sedimentation rate and C‐reactive protein may be useful over time, but they are not necessarily helpful in an acute presentation. (Acad Emerg Med. 2011;18:781; http://bit.ly/37Pudsw.) The presence of crystals almost always means gout or pseudogout, but crystals do not always definitely rule out septic arthritis. Lab and synovial fluid testing are still recommended because it can help identify patients at risk. (Orthopedics. 2017;40:e526.)
A growing body of literature has suggested that daily and repeated arthrocentesis and administering intravenous antibiotics are reasonable choices for septic joints. This approach has shown to be of greater value in some cases, with fewer complications than previously accepted and more aggressive approaches utilizing surgery and open washout. (Ann Plast Surg. 2017;78:659.) Surgery does not come without risks, so a prudent clinician should consider admission, systemic antibiotics, and consultation when concerned for a septic joint. Patients with diabetes, WBC counts of higher than 85,000, and Staphylococcus aureus or MRSA infection are at higher risk for failure from a single aspiration and a single surgical debridement. (J Bone Joint Surg Am. 2015;97:558; http://bit.ly/2SVs7Dc.) They may require longer stays in the hospital and intravenous antibiotics at home.
X-rays showing soft tissue swelling in a 64-year-old man with diabetes. The final diagnosis was septic arthritis.
Microcrystals found in the synovial fluid include monosodium urate, calcium pyrophosphate dihydrate, calcium hydroxyapatite, and calcium oxalate. Gout produces uric acid crystals, but pseudogout will have no uric acid but be positive for calcium pyrophosphate.
Finding crystals in synovial fluid usually indicates gout or pseudogout but does not definitively discount other diagnoses. The presence of crystals cannot exclude septic arthritis with total certainty. A seven-year retrospective study examining 265 joint aspirations that contained crystals found 183 (69%) had gout crystals, 81 (30.6%) contained pseudogout crystals, and 0.4 percent had both. (J Emerg Med. 2007;32:23.) Four (1.5%) of the aspirations had positive cultures for septic arthritis, but those also contained a mean WBC count of 113,000, significantly higher than the rest of the samples. Look at the WBC count (and full patient presentation) carefully if you suspect a septic joint, even if the sample contains crystals.
Injecting steroids into a septic joint is contraindicated. In fact, steroid injections in any joint (regardless of clinical setting) may not have any long-term benefit and may cause harm. Giving steroid injections in the ED is controversial, and can create conflict with consultants. One can always prescribe oral steroids to circumvent the need for intra-articular steroids. Future blogs will discuss steroid indications and technique.
Before and After Aspiration
- Arthrocentesis uses a sterile technique. We will talk about this in Part II.
- Avoid areas of superficial skin infection, moles, psoriasis, etc., during anesthetic injection or aspiration.
- Aspirations can be done on patients taking warfarin with therapeutic INRs without reversal, but check the INR before the procedure. (Mayo Clin Proc. 2017;92:1223.)
- Inject patients with hemophilia with factor VIII after aspiration.
- Aspiration of a joint with a prosthesis is considered high-risk and should be done by a consultant.
- A water bath can be used instead of lubrication if the patient cannot tolerate the pressure of the US probe during the procedure.
- When in doubt, admit.
This patient had a bright red, warm, erythematous rash over the carpal bones and a mole on the forearm. Use ultrasound to find the bundle of extensor tendons on the volar surface between the ulnar and radial bones, and plan aspiration at this site. Avoid superficial veins and arteries by identifying them first with ultrasound. Photo by Martha Roberts.
Special thanks to James Carothers, DO, an emergency physician at Berkshire Medical Center in Pittsfield, MA, and Walter Schlech, MD, the director of ultrasound there.