Subtalar joint injection (technique)

Last revised by Henry Knipe on 14 Jun 2022

Subtalar joint injections are most often performed for osteoarthritis and the posterior subtalar joint is targeted.  Ultrasound, fluoroscopy and CT guidance can be used.

  • anaphylaxis to contrast/injectates
  • active local/systemic infection 
  • bleeding diathesis
  • recent injection with steroid in same/other body parts
  • unable to remain still for the procedure
  • young age

The general principle of a (posterior) subtalar joint injection is to:

  • cannulate the joint
  • confirm an intra-articular position with imaging
  • administer intra-articular injectate, usually a corticosteroid and a small amount of longer-acting local anesthetic, e.g. ropivacaine

Relevant imaging should be reviewed, and the details of the patient confirmed.  The patient should have an opportunity to discuss the risks and benefits and consent obtained.

Risks include 

  • infection
  • bleeding
  • allergy 
  • focal fat necrosis/skin discolouration at the injection site
  • failure of the procedure to relieve pain
  • skin marker
  • ultrasound machine and sterile probe cover (ultrasound)
  • a metal rod (fluoroscopy)
  • CT biopsy grid (CT)
  • skin cleaning product
  • sterile drape
  • sterile field and tray for sharps
  • syringe selection i.e. 10mL, 5mL and 3mL
  • larger bore drawing up needle
  • needle to administer local anesthetic i.e. 30-gauge needle
  • needle to cannulate pudendal canal i.e. 25-gauge needle
  • sterile gauze
  • adhesive dressing

Luer lock syringes are best used as severely arthritic posterior subtalar joints can be difficult to inject. 

A suggested syringe and injectate selection for fluoroscopic or CT-guided subtalar joint injection -

  • 10 mL syringe: 5 mL of local anesthetic i.e. 1% lidocaine
  • 5mL syringe: iodinated contrast
  • 3 mL syringe: 40mg triamcinolone acetonide (40 mg/1 mL) and 1 mL 0.5% ropivacaine

A suggested syringe and injectate selection for ultrasound-guided (posterior) subtalar joint injection -

  • 10 mL syringe: 5 mL of local anesthetic i.e. 1% lidocaine
  • 3 mL syringe: 40mg triamcinolone acetonide (40 mg/1 mL) and 1 mL 0.5% ropivacaine

Pre-procedure planning should calculate the distance required to reach the pudendal canal, as larger patients will require longer needles. 

  • Posterior subtalar joint:  25-gauge 40mm needle
  • check for allergies and if on blood thinners
  • consent
  • position patient by lying on their side, with the targeted side facing up
  • place CT biopsy grid 
  • perform planning CT, and identify posterior subtalar joint and access whilst avoiding the peroneal tendons
  • mark skin at the entry site
  • clean skin and draw up appropriate medications
  • give local anesthesia along the proposed needle path
  • under CT guidance, pass the needle into the posterior subtalar joint 
  • inject a small amount of iodinated contrast to confirm the needle tip position
  • administer steroid containing injectate 
  • removed the needle and apply dressing/ band-aid as required
  • pain diary to be given
  • check for allergies and if on blood thinners
  • consent
  • position patient by lying on their side, with the targeted side facing up
  • optimize positioning and c-arm, getting the best view of the posterior subtalar joint 1
  • using the metal rod mark skin at the entry site 
  • clean skin and draw up appropriate medications
  • give local anesthesia along the proposed needle path
  • under fluoroscopic guidance, pass the needle into the posterior subtalar joint 
  • inject a small amount of iodinated contrast to confirm needle tip position and save an image
  • administer steroid containing injectate 
  • removed the needle and apply dressing/ band-aid as required
  • pain diary to be given

Steroid flare is a relatively common side effect that will settle after 1-2 days.  The most serious complication is an infection causing septic arthritis. Steroid-containing injections should be postponed if there are signs and/or symptoms of local and/or systemic infection.  Possible fat necrosis causing skin dimpling and skin discolouration can occur due to steroids leaking into the surrounding soft tissues, and the patient should have consented to this 2.

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