The patient’s unmet needs (PUNs)
A 48-year-old man attends complaining of a painful and stiff ring finger, which has been troubling him for a few weeks. He describes it as getting stuck in flexion, especially in the morning, with him having to forcibly straighten it out. There is no obvious abnormality on examination apart from mild tenderness at the base of the finger. ‘My friend says it’s trigger finger,’ he says. ‘He had an operation, but I’m not keen on that. Is there anything else we can do? And why have I got it, anyway? I’m worried it might start to affect my other fingers.’
The doctor’s educational needs (DENs)
What are the diagnostic features of trigger finger? What differential diagnoses should be considered?
The three diagnostic features are clicking, locking and pain.
Trigger fingers are more common in females and particularly postmenopausal women. The ring finger is the most common, then the middle, and then the little finger. The index finger is rarest. Triggering of the thumb is as common as the middle finger. There is another, much smaller, peak of incidence in childhood between the ages of two and three. The thumb is most involved in children and presents with an inability to straighten.
Generally, the symptoms are worse in the morning and the finger can get locked down into the palm (see image below) and the patient has to pull it straight with the other hand. The cause of the pain and clicking is the tendon lump entering and exiting the flexor tendon sheath.
Occasionally, it can present with just pain and swelling without the clicking; in my experience this presentation is more likely in patients with diabetes.
On examination there may be swelling of the digit, but almost invariably there is tenderness over the base of the flexor tendon sheath, on the palmar side just distal to the distal palmar crease.
Dupuytren’s contracture may be the most common condition in the differential diagnosis, but the distinguishing feature is the obvious bands in the palm, and it is a chronically developing contracture. Less common is a locked metacarpophalangeal joint (MCP), where there is an inability to fully extend the MCP only, due to an arthritic osteophyte. Here, the finger does not roll up into the palm.
What underlying problems might give rise to trigger finger and to what extent should these be pursued? Is there anything patients can do to stop it affecting other fingers?
The cause of trigger finger is not understood, but it is probably thickening of the tendon sheath caused by some form of inflammation, although pathologically ‘inflammation’ and inflammatory cells are not found. Hence the correct term is teno- (tendon) -vagina- (sheath) and- osis (affliction) – tenovaginosis rather than tenovaginitis.
There has been no good scientific proof that it can be caused by any specific form of injury and there is certainly no association with repetitive activities. There is, however, good evidence that trigger finger has no association with any form of activity or occupation.1
It is more common in people with:
• Diabetes – the most common cause of multiple trigger digits.
• Dupuytren’s disease.
• Inflammatory arthritis (rheumatoid).
• Carpal tunnel syndrome.
• Renal disease.
How far you should pursue these conditions is debatable. There is no evidence that correcting these abnormalities – treating the diabetes or amyloidosis – helps the triggering. However, I seek diabetes if I come across a patient with multiple trigger digits.
Are any non-invasive treatments, such as NSAIDs or splints, effective?
NSAIDs may help the pain but there is no direct evidence that they are beneficial in the condition. Splints can stop the locking of the finger, which may be particularly useful at night (strapping it to a tongue depressor at night may prevent locking in the morning) but, again, there is no science that they are beneficial in treating the condition.
How useful are cortisone injections? If a nodule is palpable, should the injection aim for this or should cortisone simply be injected into the tendon sheath?
Steroid injections are certainly both useful and beneficial. It should be put into the flexor tendon sheath.
There are two reasons to avoid the nodule:
• The nodule is actually the tendon and if you inject into the tendon it will be more likely to rupture.
• The level of the nodule in the sheath will be the tightest – there will be less space around the tendon to inject into the sheath.
The effectiveness of the injections varies in published studies, but in one study of 338 fingers, the success rate was 50% after the first injection, rising to 60% after two.2
In 2009, there was a Cochrane review that found only two trials, and the success rate was 37%.3
Most hand surgeons will give one injection, perhaps two, and then advise surgery, which will provide a permanent solution.
Patients with diabetes respond less well to injections.4
What is the prognosis? Which patients should be referred for surgery?
Some patients with trigger finger will improve without treatment. Most will respond to injections. One study showed that the most cost-effective treatment is two injections and then surgery, but the evidence is damning about the costs of the alternative treatments.5
Refer on for surgery if:
• The condition recurs after two injections.
• The response after one injection is shortlived.
• The patient would prefer to have a permanent solution or doesn’t like needles.
Mr Jeremy Field is a consultant orthopaedic and hand surgeon at Gloucestershire Hospitals NHS Foundation Trust