Acquired triggering of the fingers and thumb in adults
BMJ 2017; 359 doi: https://doi.org/10.1136/bmj.j5285 (Published 30 November 2017) Cite this as: BMJ 2017;359:j5285
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David, M et al's 'clinical update' of trigger finger is a useful review (BMJ 2017;359:j5285). However, whilst a steroid injection is a useful starting point for patients with disturbing symptoms, I find it difficult to agree with the technique recommended. Early in a 30 yr hand surgical career I came to realise that injections into the highly innervated and sensitive palmar skin (certainly with a needle of the calibre recommended by the authors) cause entirely unnecessary pain.
The following technique has served me well and is virtually painless because the web skin between the fingers is relatively poorly innervated:
1) Mark the target spot on palmar skin at the affected A1 pully (about 1 cm distal to the distal palmar crease).
2) Pass a 25G (orange) 2.5 cm needle through the mid-point of the web skin next to the affected finger, parallel and 1 cm deep to the overlying palmar skin, towards the marked spot, until the needle is up to its hub.
3) The tip will now be perfectly positioned adjacent to the flexor sheath. There is NO need to move the tendon.
4) The steroid (best 1 ml triamcinalone 10 mg/ml) will work over a large area during the following 48 hours.
5) There is no benefit at all in the traditional addition of local anaesthetic mixtures to the steroid. How could this help when anaesthetics take some minutes to work whilst injection pain is normally immediate due to volume effects?
This method will virtually guarantee you a happy patient, full of admiration that the proposed injection did not hurt. Moreover, it also avoids the small infection risk associated with the open hub of the needle whilst it being used for what the authors describe colourfully as 'windscreen-wiping'. Finally, it is important to use a fine calibre needle (either 25G or 27G) in order to avoid the theoretical risk of digital nerve bevel injuries when approaching the tendon sheath from laterally.
Competing interests: No competing interests
It may be of interest to the authors that they could consider, prior to more drastic intervention, the daily administration of an oral intake of E-304 powder (2.4gm) and fish oil (5ml).
In practice this has been found to quickly reduce or eliminate the trigger effect in a number of cases and appears consistent with the effect of the same administration in cases of swollen joints and pain in RA. Daily intake can be an effective dampener of symptoms for years ( 6 years so far in an informal trial).
I would be pleased to discuss this if colleagues are interested.
Competing interests: No competing interests
Alternative techniques for trigger digit steroid injection
The mid-lateral approach was described by Carlson and Curtis in 1984 [1]. Jianmongkol et al compared the mid-lateral approach with the conventional direct palmar approach in a prospective randomised control study of 103 trigger injections using a 2ml mixture of steroid and 1% lidocaine [2]. They demonstrated a 17% reduction in pain (8 points on a 100-point visual-analogue scale), with no difference in the consumption of post-procedure paracetamol. However, this difference in pain was lost quickly at first follow-up a week later, and recurrence of triggering beyond 6 weeks was not assessed. Within their study population, the mid-lateral approach appeared equally safe and effective, but the authors were keen to highlight the hazard of straying volar to the mid-axial line due to the associated risk of encountering the neurovascular bundle resulting in pain or damage even with a 25-gauge needle.
A further alternative method is a direct anterior, retrograde approach performed at the level of the proximal phalanx (P1), and is preferred by many ultrasonographers [3]. A prospective randomised control trial of 40 trigger injections using a 2ml mixture of steroid and local anaesthesia, demonstrated that a P1-level approach was as safe and effective as the conventional palmar approach, but with a 56% reduction in immediate pain (4 points on a 10-point visual-analogue scale) [4]. There was a trend towards higher recurrence of symptoms as early as 3 months, but this failed to reach statistical significance.
As is frequently the case in medicine and surgery, it is probably best to do what works well in your hands. I have found surgical and GP trainees become comfortable with the conventional palmar approach quickly. Physicians who wish to try the mid-lateral approach should follow the clear instructions set out by Mahaffey P (BMJ 2017;359:j5285/rr-0), and I have provided below some additional tips:
• Be aware that this approach introduces two planes of uncertainty, and triangulation is important not only for correct needle-tip position, but also to avoid neurovascular injury and subsequent distress. The importance of correct deposition of steroid within the flexor sheath has been questioned by Kazuki et al, who showed high success rates in resolving pain and triggering following injection of a mixture of steroid and 1% lidocaine into the subcutaneous tissue overlying the A1-pulley territory [5].
• It seems logical that higher gauge needles will be less painful, but ensure your unit stocks needles of correct length. The 25-gauge (orange) needles are available in both 15mm and 25mm lengths. 27-gauge (grey) needles are very fine but bend easily. Though a little more painful a 23-gauge needle may be better for larger hands with tougher palmar skin and tissue.
• A narrower needle will increase the resistance to flow (based on the Haigen-Poiseulle equation [6]), and greater force may be required to depress the syringe plunger. A small (<5ml) syringe with a one-piece luer-lock fitting [7] (as opposed to a slip-tip fitting) may prevent the embarrassing situation where the syringe disengages from the needle during injection, resulting in its contents splashing over both patient and physician!
• The evidence base behind trigger digit steroid injections advocates use of a mixture of steroid with 1% lidocaine [8,9]. There are presently no studies directly comparing trigger digit injections using steroid alone versus steroid mixed with a local anaesthesia agent. While combining local anaesthesia will not impact on the immediate pain experienced during an injection, it will be of benefit in reducing pain soon afterwards.
References
1. Carlson C, Curtis R, Steroid injection for flexor tenosynovitis, J Hand Surg Am. 1984; 9(2):286-7
2. Jianmongkol S, Kosuwon W, Thammaroj T, Intra-Tendon Sheath Injection for Trigger Finger: The Randomized Controlled Trial, Hand Surgery. 2007; 12(2):79–82
3. Bodor M, Flossman T, Ultrasound-guided first annular pulley injection for trigger finger, J Ultrasound Med. 2009; 28(6):737-43
4. Pataradool K, Proximal Phalanx Injection for Trigger Finger: Randomized Controlled Trial, Hand Surgery. 2011; 16(3):313-7
5. Kazuki K, Egi T, Okada M, Takaoka K, Clinical Outcome of Extrasynovial Steroid Injection for Trigger Finger, Hand Surgery. 2006; 11(1-2):1–4
6. Gooch J, Hagen-Poiseuille Equation, Encyclopedic Dictionary of Polymers. 2011, Springer, New York (NY)
7. International Organization for Standardization, ISO 80369-7 Small-bore connectors for liquids and gases in healthcare applications - part 7: connectors for intravascular or hypodermic applications, 1st Edition, 2016. URL: https://www.iso.org/standard/58011.html (last accessed 15 December 2017)
8. Mol MF, Neuhaus V, Becker SJ, Jupiter JB, Mudgal C, Ring D, Resolution and recurrence rates of idiopathic trigger finger after corticosteroid injection, Hand (N Y). 2013 Jun;8(2):183-90
9. Schubert C, Hui-Chou HG, See AP, Deune EG, Corticosteroid injection therapy for trigger finger or thumb: a retrospective review of 577 digits, Hand (N Y). 2013;8(4):439-44
Competing interests: No competing interests