Thumb CMC Joint Injection Dosing
For thumb carpometacarpal (CMC) joint injection, use 5-15 mg of triamcinolone acetonide (0.5-1.5 mL of 10 mg/mL concentration) alone, without lidocaine, as adding local anesthetic increases injection pain without clinical benefit. 1, 2
Triamcinolone Dosing
The FDA-approved dose range for intra-articular injection is 2.5-5 mg for smaller joints and 5-15 mg for larger joints, with the thumb CMC joint falling into the smaller-to-medium joint category. 1
For adults, doses up to 10 mg for smaller areas and up to 40 mg for larger areas have been sufficient, though the thumb CMC typically requires the lower end of this range. 1
Use triamcinolone acetonide 10 mg/mL concentration, injecting 0.5-1.5 mL (5-15 mg total) depending on joint size and severity of inflammation. 1
Critical Safety Considerations
Avoid high-concentration triamcinolone injections, as doses of 40 mg have been associated with flexor tendon rupture in hand injections. 3
The injection must be placed into the joint space itself, not into surrounding tendons or tendon sheaths, as intratendinous injection can cause tendon rupture. 3
Strict aseptic technique is mandatory, and the vial should be shaken before use to ensure uniform suspension. 1
Lidocaine: Not Recommended
Recent high-quality evidence demonstrates that adding lidocaine to corticosteroid injections for hand procedures actually increases injection pain rather than decreasing it. 2
A 2021 randomized, double-blind controlled trial showed that patients receiving triamcinolone plus lidocaine with epinephrine experienced significantly higher pain scores (VAS 3.5) compared to triamcinolone with saline placebo (VAS 2.0). 2
Using corticosteroid alone is not only less painful but also simpler, more efficient, and safer by avoiding potential complications from combining multiple local anesthetics. 2
If you choose to use lidocaine despite this evidence, the maximum safe dose is 7 mg/kg with epinephrine or 4.5 mg/kg without epinephrine, calculated using ideal body weight. 4, 5
When Lidocaine Might Be Considered
For patients with extreme needle phobia or anxiety, you could consider adding 0.5-1 mL of 1% lidocaine (10 mg/mL), though this increases injection pain acutely. 4
If using lidocaine, wait at least 4 hours before performing any other local anesthetic procedures to avoid cumulative toxicity. 4, 5
Injection Technique Specifics
Inject deeply into the joint space using proper intra-articular technique, ensuring the needle enters the joint cavity and not surrounding soft tissues. 1
If excessive synovial fluid is present, aspirate some (but not all) before injection to aid pain relief and prevent undue dilution of the steroid. 1
Inject without delay after drawing up the medication to prevent settling in the syringe. 1
Avoid injecting into tissues surrounding the joint, particularly in areas with minimal soft tissue coverage, as this may lead to subcutaneous fat atrophy. 1
Clinical Efficacy Considerations
Image guidance (ultrasound or fluoroscopy) does not significantly increase time between injections or meaningfully delay surgery, and costs approximately $203 more per injection. 6
The average duration of symptom relief from a single CMC injection is approximately 237-267 days, with recurrence rates around 20%. 6, 7
EULAR guidelines support intra-articular corticosteroid injection for painful flares of thumb base osteoarthritis, though the evidence is somewhat limited. 4
Monitoring and Follow-up
Monitor for early signs of local anesthetic toxicity if lidocaine is used, including circumoral numbness, facial tingling, metallic taste, and auditory changes. 4, 5
If symptoms recur, repeat injections can be given, but maintain appropriate intervals (typically 2-3 months minimum) to minimize cumulative steroid exposure and tendon weakening risk. 3, 7
Consider surgical referral if conservative treatment including 2-3 injections fails to provide adequate symptom control. 4