Surgery has been the mainstay of CTS treatment since the 1950s and has received the lions share of scientific attention with endless publications devoted to minor variations of surgical technique. The principle is very simple - the tunnel is constricting the nerve so make the tunnel bigger. In practice the simplest way to achieve this is by cutting the transverse carpal ligament, effectively converting the carpal ‘tunnel’ into a carpal ‘trench’ - albeit one still covered over by skin and subcutaneous tissue. More complex procedures in which the ligament is lengthened rather than merely cut do not seem to be any more or less effective and have not been widely adopted and there are now generally two broad approaches to how to do it which may be termed ‘from the outside’ and ‘from the inside’.
The first is the obvious and traditional approach - make an incision over the carpal tunnel area, identify the ligament and, being careful to protect the nerve, its branches and other vital structures in the area, cut it. The incision is a small one at the heel of the hand - an operative photograph appears on a separate page so that people do not come across graphic illustrations of surgery without warning.
The second approach is the province of ‘keyhole surgery’ - essentially an instrument of some kind is inserted into the carpal tunnel and the cut to the transverse carpal ligament is made from the inside out. (Purists might argue that in both methods the cut is actually made from end to end of the tunnel not from either inside or outside but this does not invalidate the overall concept)
There are many small variations on both techniques which are not worth listing here. This is not a manual for surgery. The bottom line is that the long term results of the two approaches are indistinguishable, the only measurable difference between them being that recovery is slightly faster after keyhole surgery, by a matter of a few days. Unless you are very concerned about time taken to return to work it is more important that you find a good surgeon who is happy with the method that he or she uses than it is to choose a particular surgical method. The issue of return to work after surgery is addressed below.
Problems with surgery - It cannot be denied that surgery for carpal tunnel syndrome technically constitutes a deliberate injury to the ‘natural’ structure of the wrist. After all we presumably have a transverse carpal ligament because it serves some biological function and one might wonder what the effect of cutting it might be in a normal wrist. In fact the transverse carpal ligament seems to perform two tasks.
Firstly it holds down the flexor tendons at the wrist and forms a pulley for them to act around when they flex the fingers. Without it, when the wrist is flexed and a power grip is used the tendons can be seen to be more prominent than usual at the wrist - a phenomenon known as ‘bowstringing’. The change to the mechanical action of the flexor tendons seems to result in slight loss of grip strength and when this is measured objectively hands after carpal tunnel surgery are, on average, about 2% weaker. Note that carpal tunnel syndrome itself does not usually have a profound impact on grip strength as this movement is performed mainly by the forearm muscles which are not affected by CTS. People do drop things a lot when suffering from CTS but this is probably not directly a result of weakness of grip.
Secondly the transverse carpal ligament helps to hold the wrist bones in a particular physical configuration. The bony structure of the wrist (the carpus) includes 8 small bones which lie between the ends of the long forearm bones (the radius and ulna) and the small bones of the hand (the metacarpals). It is this complex bony structure that gives the wrist its remarkable flexibility but it also means that there are a very large number of joints between the various bones which actually comprise the structure which we rather simplistically think of as the ‘wrist joint’. The carpal bones are arranged roughly in two rows of four each with each row taking up an ‘arch’ shape which is convex towards the back of the hand and concave towards the palm. The carpal tunnel nestles inside this arch and the transverse carpal ligament spans the gap between the two sides. When it is cut the arch tends to ‘open out’ and the spatial relationship between all these small bones changes slightly, placing unaccustomed stresses on the ligaments which hold them all together.
These changes are an unavoidable consequence of correctly performed carpal tunnel decompression and thus cannot be considered ‘complications’ of surgery which can be avoided by good technique. Mostly they do not cause post-operative symptoms which are worse than the original problem of having the nerve trapped but some patients are troubled by persistent weakness and wrist pain after surgery.
Two other difficulties are peculiar to carpal tunnel surgery and are in some ways inter-related. The heel of the hand gets a lot of everyday ‘wear and tear’ in normal daily activities and is not an ideal place to have a surgical scar which may become tender or hypertrophied with excessive scar tissue. The traditional open operation thus leaves a scar in an unfortunate place and this is one reason for the development of ‘keyhole’ approaches which avoid this. Another consequence however is that surgeons are under some pressure to keep the incision as short as possible and as a result their view of the transverse carpal ligament at surgery may not be as good as they would wish. It is therefore not too surprising that in some cases they do not manage to cut all of the ligament but leave a portion of it still compressing the median nerve - usually at the forearm end of the tunnel rather than the hand end.
In addition to this, carpal tunnel surgery is an operation like any other and is vulnerable to the same kinds of surgical risk which affect any other operations. Surgeons unfortunately do sometimes cut, stretch or compress structures which they should not and some patients will get wound infections or vascular complications which can make more of a mess of the hand than the original CTS. A few unfortunate patients are afflicted by a poorly understood condition called complex regional pain syndrome (old name reflex sympathetic dystrophy) which can follow any injury to a limb. A full discussion of this difficult condition is outside the scope of this site but a good starting point for information about it is the NHS choices website.
The bottom line is that not all patients are satisfied with the outcome of their carpal tunnel operation and in my own area about 8% of all operated patients consider their hand to be worse after surgery than it was beforehand. (people who have seen me may remember that I usually quote a figure of 5% failure for surgery - this is because some failures are predictable, at least in a statistical sense and I am modifying the figures to the particular circumstances of the patients that I personally am recommending surgery for - see below for much more on surgical prognosis). Although this is considered a successful operation by general surgical standards, and most patients are undoubtedly very satisfied with the results it is also true that a few of the worst affected patients have their lives ruined by the consequences of carpal tunnel surgery and it is not a procedure to be undertaken lightly.
In the many published series of carpal tunnel operations there is considerable variation in the reported surgical success rate and it appears that some surgeons are able, presumably through a combination of good patient selection and surgical expertise, to achieve better results than others (Bland 2007). I have spent many years exploring the factors which might influence surgical outcomes for CTS and what I have discovered so far is covered in the section on surgical prognosis.
For patients in employment a frequent question is “ how long will I be off work?” Although the topic has been quite extensively documented it turns out to be a difficult question to answer. Much of the existing literature on surgical treatment for CTS comparing different variations of surgery, for example traditional open surgery vs one of the endoscopic methods, uses the time to return to work after surgery as one measure of outcome, and it has been fairly convincingly shown that return to work times are a couple of days shorter for endoscopic than for open surgery. What this finding tends to conceal is the fact that other factors are much more important than the type of surgery in determining the length of time off work. It should be obvious, when you think about it, that the type of work involved is going to be a major determinant of time off, and indeed this proves to be so.
(Cowan 2012) looked at other factors influencing return to work times and found that desk based workers returned to modified work an average of 6.7 days after surgery and to normal work after an average of 9.5 days, though there was considerable variability. On the other hand, those subjects with non-desk based jobs required average times of 17.7 and 29.5 days to return to modified and normal work respectively.
A further interesting observation from this paper is that the pre-operative expectations and needs of the patient tend to be borne out in practice. People who expected to be off for longer tended to be right and people who expressed a pre-operative desire to get back to work quickly tended to do so. All of the patients in this study had essentially the same operation and the same pre-operative counselling and post-operative care. None of them were involved in compensation claims for work-related CTS, a factor which has been consistently found to correlate with longer periods off work.
Revision date - 6th April 2012