AMIS Minimally Invasive
Minimally Invasive Hip Replacement
There has been an increase in interest in performing hip replacement surgery by less invasive means, and by smaller incisions. Minimally invasive hip replacement surgery has been being performed in Europe for many years now and the number of these procedures that are being performed in Australia now is rapidly increasing. There has been increased publicity in Australia through our various media forms and many patients are now requesting this form of hip replacement surgery due to the many advantages this surgery provides over traditional hip replacement surgery.
Whilst there is no study that has shown the significant long term difference in results between minimally invasive approaches and standard approaches, I believe that there are several advantages with the anterior mini incision.
History of AMIS
I first became exposed to the anterior minimally invasive approach (AMIS) when I worked with Prof Emile LeTournel in Paris in 1986. I was quite impressed with the results of hip replacements done via this method, but it did require the use of a special operating table which was not available in Australia until recently.
The AMIS Approach
Medacta, a European orthopaedic company, has been working with European surgeons to develop a special operating table to allow the use of the anterior minimal incision. Although there are several other so called minimal approaches, the anterior approach is the only one that does not involve cutting any tendons or muscles. The technique does involve a different approach to what most surgeons are accustomed to. I have attended a learning centre in France to familiarise myself with the technique. Although there is only a small number of orthopaedic surgeons performing this procedure in Australia, it is gaining wide popularity in France, Germany and Switzerland.
Advantages of AMIS
- No muscle or tendons are cut
- Better cosmesis as the scar is very small
- Potential shortened length of stay in hospital
- No need for special precautions postoperatively
- Very low dislocation rate
Type of Prosthesis for AMIS
The acetabular and femoral components are made of titanium which has been shown to have excellent long term results. The surfaces are coated with hydroxyappatite which further stimulates early bone growth into the prosthesis. Neither prosthesis requires bone cement. There is a choice of articulation, either being cobalt chrome on high cross linked polyethylene or ceramic on ceramic. Both have their advantages and disadvantages and choice of bearing can be discussed at the time of the consultation. Generally, ceramic on ceramic is used for younger, more active patients.
Indications for AMIS
The vast majority of patients with osteoarthritis of the hip are suitable for this technique. It is not indicated in patients who are markedly obese, or those patients have had previous hip surgery, or in patients who have complex anatomical problems, such as congenital dislocation of the hip.