Minimal incision total hip replacement
Increasingly, patients are showing interest in the concept of minimal incision total hip replacement. This is a routine hip replacement that is performed through a smaller-than-normal skin incision. There is no clear definition of the term 'minimal incision' although most would regard incisions of 10cm or less as minimal. A traditional total hip replacement might be performed through an incision of more than 20cm in length.
To undertake a minimal incision total hip replacement one of two surgical approaches is used. These are the single incision or the two-incision techniques.
The two-incision technique requires a small incision on the front of the hip and another on its outer aspect while the single incision technique involves a small incision on the outside of the hip alone. With the single incision technique some small muscles are divided at the time of the procedure but these are very small indeed and are reattached at the end of the operation. With the two-incision technique muscles are not divided but are separated.
The principle of both techniques is to minimise the degree of soft tissue damage at surgery and thereby improve the chance that a patient will mobilise rapidly after the procedure. Special instruments have been designed in order to make minimal incision total hip replacement possible and special training is available for surgeons who wish to perform this procedure.
However, one thing does not change with minimal incision total hip replacement, irrespective of whether a single or a two-incision technique is used. The components inserted are exactly the same as those that would be used for a standard hip replacement. The amount of bone that is removed is also the same, so although the skin incision(s) may be small the operation that takes place under the skin remains unchanged.
The true results of minimal incision total hip replacement are still unknown. The procedure is technically harder to perform than a routine total hip replacement and requires a little longer in the operating theatre. A number of complications have been described, including difficulty in satisfactorily positioning the socket component of the hip replacement, fractures of the femur and nerve damage. On the assumption that the artificial components have been properly seated at a minimal incision total hip replacement, it is reasonable to assume that a replacement performed through a small incision will last just as long as one which has been performed through a large incision. However, the evidence for this currently does not exist and is unlikely to do so for some years.
Part of the reason for introducing minimal incision hip replacement surgery was the assumption that it would allow a patient to mobilise more rapidly after their operation, reduce the length of hospital stay, reduce blood loss and reduce complications. There is some logic to these claims but in reality evidence is slowly gathering that the length of the incision is not the most critical factor. It may be of cosmetic importance but struggling to keep an incision small can sometimes create difficulties at surgery and increase rather than decrease the risk to a patient. It appears that the ability to mobilise rapidly after hip replacement is due to a combination of factors, not just the length of the incision. Other important factors include the type of anaesthetic administered, successful post-operative pain control and the rehabilitation regime used after surgery. This is the reasoning behind the so-called ‘fast-track’ system currently being developed at the Cambridge Hip and Knee Unit, a method of performing a total hip replacement that encompasses all of these factors, not just minimal incision. Nevertheless, it makes reasonable sense to keep an incision as small as possible provided that it does not compromise the ability of the surgeon to insert the artificial components satisfactorily.
Some patients are unsuitable for minimal incision total hip replacement, particularly those who are obese. Also, patients with very deformed hip joints as a result of their arthritis may be inappropriate for the procedure. Previous surgery to the hip joint can sometimes also make minimal incision hip replacement a difficult task.
It will be several years yet before the true effects of minimal incision total hip replacement can be established but those of us who are involved in its development are, you can be certain, looking at it very closely indeed