Less Invasive Knee Replacement

Less Invasive Knee Replacement

Treatment and Rehabilitation

Less invasive total knee replacement surgery is a specific approach surgically at the time of the operation in order to undertake a total knee replacement. It is something that is commonly discussed on the internet and in the lay press, and it is certainly a hot topic of debate among orthopaedic surgeons.

The principle of Less invasive surgery is that it reduces the amount of soft tissue trauma to the knee and therefore allows quicker recovery with less pain and less bleeding. ‘Less invasive’ is a more appropriate term than ‘minimally invasive’ because the incision and the soft tissue approach have to be large enough to allow adequate access to the knee joint in order to place the components of the knee replacement into an anatomical position.

The reason that less invasive knee surgery and hip surgery is popular with the public, is because of the way it is marketed in that it allows the surgery to be done through a small incision. The length of the incision is of secondary benefit and is certainly not the prime reason to be doing this surgery. In fact, the original two-incision hip replacement surgery, which was very popular in the USA has now essentially become a defunct operation, due to the fact that the numbers of complications rose dramatically with this less invasive approach.

Because less invasive knee arthroplasty by definition will allow less visualisation of the knee joint at one time, it becomes a much more technically demanding operation with a significant learning curve.

Contra-indications

Less invasive knee replacement surgery is not a technique for every patient, and more importantly, it is not a technique that every surgeon should be employing. There are certain patients where it is very difficult to use a less invasive soft tissue approach, for example very muscular patients, grossly obese patients, patients with a short patella tendon and patients with other unique anatomical variants. However, the principles of less invasive surgery can be applied.

Principles

The principles of less invasive surgery are to reduce soft tissue trauma, by reducing the size and position of the incision in the soft tissues to minimise disruption of the quadriceps mechanism (link). This is aided by not everting (flipping the kneecap over) the patella during surgery, which in itself damages the soft tissues, and can cause dysfunction to the quadriceps mechanism.

Because the soft tissue window of exposure is reduced, it also means that the whole of the knee joint cannot be seen at the same time. This can pose problems and in order to undertake the operation, the principle of using a ‘mobile window’ is used. By appropriate adjustments of retractors, different parts of the knee joint are brought into view at the appropriate time during the surgical procedure, in order to undertake the operation.

On the courses where I teach other surgeons about less invasive knee surgery, I emphasise strongly to them, that the most important part of knee replacement surgery, is the technical aspect of putting the knee replacement in the right place. If they do attempt less invasive surgery or less invasive surgery if there are any concerns about the alignment or position of the prosthesis, I would advise them to immediately convert to a standard approach. The cosmetic element of less invasive knee arthroplasty, is from a surgical point of view, the least important. However, with less invasive techniques, the scar length for a knee replacement can be reduced significantly to almost half the length of a routine scar incision.

Less invasive surgery is a demanding technique and requires a significant learning curve. This is reflected by the high risk of complications with less invasive surgery, which includes malalignment of the prosthesis which will make the knee replacement fail at an earlier stage.

Advantages

The advantages of less invasive surgery are:

– To allow quicker rehabilitation of the knee due to the decreased soft tissue trauma.
– There is also less bleeding and less pain, which contributes to the quicker rehabilitation.
– It is said that a greater range of motion is achieved compared to a conventional approach.
– There is a quicker return to function.
– There is a shorter length of stay in the hospital which can be reduced down to about two to three days, compared to an average of seven to ten days with a standard knee replacement approach.
– By reducing the length of stay in a hospital, this has a secondary effect which I believe it to reduce the risk of hospital-acquired infections including MRSA as well as reducing the risks of DVT and pulmonary embolus due to early mobilisation.
– My patients undergo less invasive knee replacement surgery follow an accelerated rehabilitation programme which commences on the day of surgery. This includes an immediate range of motion exercises, quadriceps strengthening, hyper-extension stretching and early walking (preferably on the day of surgery).

Computer-aided surgery

The issues regarding alignment can be improved with computer aided surgery and customised/personailised Knee replacement surgery. Both of these techniques utilise cutting edge modern computerised and 3D animation/design technology in differing ways.

One of he most important factors in the success of a knee replacement is the alignment with which the prosthesis is placed. There is good evidence in the orthopaedic literature that malalignment of the prosthesis beyond as little as 3° can reduce the survivorship and long-term success of a knee replacement.

It was on this background that computer aided surgical and customised techniques have been developed, using high power computer technologies. With the customised / personalised techniques and systems, there is the added advantage that the implants placed in your knee can be personalised specifically to your own knee and anatomy using ground breaking 3D printing techniques.

The techniques involve the use of the uniqueness of your individual bones, which are read by a computer using infra-red beams to determine the alignment and position of the limb and the knee joint, to allow the components to be placed more accurately and more reliably, or by pre-scanning the knee and leg (in the case of customised / personalised knee replacements) to generate 3D models of your knee from which cutting blocks and implants specific to your particular anatomy are created and sent to the surgeon to use during your operation. Visit the personalised Total Knee Replacement page for more information.

The added advantage of these techniques is that they are ideally suited for less invasive knee replacement surgery. The whole of the knee does not have to be seen or exposed all at the same time during the surgery due to the benefits gained by the computerisation. The soft tissue trauma can be minimised further without compromising the alignment and end result of a knee replacement.