Minimally invasive techniques in total hip arthroplasty (minimal invasive hip replacement-MIS)

In recent decades there has been a growth in minimally invasive techniques (minimal invasive surgery-MIS) across a wide range of specialties, including abdominal surgery, thoracic surgery and neurosurgery. Orthopaedics has been no exception in this field, with minimally invasive techniques being used to perform operations on a variety of joints, such as the knee, the shoulder, the wrist, the ankle and the hip. In the hip in particular, arthroscopic techniques have been used to treat tears of the labrum, instability and infection, and to remove loose and foreign bodies. Hip arthroscopy has also been used to assess polyethylene wear in total hip arthroplasties, as well as an additional tool for inspecting the femoral canal during revision of total hip arthroplasty.
In recent years, advances in surgical techniques and in the manufacture of instruments have allowed surgeons to perform total hip arthroplasty through incisions far smaller than those used in the past. The term minimally invasive surgery (MIS) in total hip arthroplasty essentially refers to techniques in which the length of the surgical incisions and the manner of the surgical approach have been deliberately modified, in an attempt to reduce the tissue trauma associated with total hip arthroplasty, with most investigators reporting incisions of 10 centimetres or less. The minimum incision length that can be used, without stretching the skin, is usually determined by the diameter of the acetabular implant that is to be used. In order for the acetabular implant to be inserted without stretching the skin incision to any great degree, the length of the incision should be at least equal to half the diameter of the acetabular implant.
Many MIS-type total arthroplasty techniques have been described and they are usually divided into two broad categories, those using a mini surgical incision and those using a two-incision approach. The mini incisions are essentially modifications of the classic posterior, anterolateral and anterior approaches normally used for total hip arthroplasty, and are performed through surgical incisions seven to 10 centimetres long. The two-incision technique is a newer approach to total hip arthroplasty, in which planes between the muscle fibres are used to reach the joint and which minimise the division of muscles and tendons.
With any technique, the reduced length of the surgical incision and the reduced division of tissue mean that newer surgical instruments have to be used. The development of MIS hip arthroplasty is therefore accompanied by the development of special instruments designed to facilitate the exposure and the preparation of the bony structures.
However, even where such instruments are not available, the general trend in total hip arthroplasty today is to use the smallest possible skin incisions, together with approaches to the joint in which muscles or tendons are not divided but an attempt is made to reach the joint parallel to the muscle fibres, so that damage to the tissues is greatly reduced.
Minimally invasive surgical techniques in total hip arthroplasty have succeeded not so much in improving the cosmetic result after such an operation, but in offering the patient a strikingly better immediate postoperative period, such that from the first day patients are able to bear their body weight on the operated hip and to walk straight away. In addition, the progress of the patient with a total hip arthroplasty has been greatly accelerated during the first weeks, and activities that were traditionally forbidden until three months after such an operation are now incorporated into the rehabilitation programme of the first weeks after total hip arthroplasty.