This innovative procedure employs various techniques that are applied with extra care and diligence to achieve some good early outcomes such as the ability to walk with minimal assistance on day one or two.
The incision is a small one made as shown. The muscle structures are never cut as such but a pathway is made through the natural planes between muscle bodies until the joint capsule is reached. At this point, the capsule is opened by use of electrocautery (a method of controlling bleeding by use of a small electric current) and held back by retractors (instruments that hold back the tissues). When the top of the femur is visualized along with the joint, special instruments are used to open up the canal in the femur to take the trial stem that is left in the bone for future guidance.
Next the surgeon will address the head of the femur that has to be excised. This is accomplished by cutting the neck of the femur using the trial stem (left in the bone earlier) as a guide to cut exactly where it is needed.
When this is done, the lower femur is lifted aside and two strong screws are inserted into the femoral head and used to gently lift the head out of the socket and out of the wound.
In this way, the hip is prepared without the traditional method of dislocating the hip by manipulating the leg until the head is separated from the socket (acetabulum).
Now the socket (acetabulum) is prepared. To do this an “alignment” tool is positioned carefully in the socket so the arm is over the thigh. Here a very small incision is made to enable another instrument to be passed through the cannula (tube), through the incision and into the leg until it is visible in the wound. The direction of this is controlled by the alignment guide.
At this point the guide is removed leaving only a cannula (tube) that will guide subsequent instruments called reamers into the correct position to prepare the socket. The shaft of the reamer goes through the cannula into the hip socket where it engages with the grater-reamer that has been placed in readiness.
This method not only avoids causing trauma to the skin and other tissues whilst carrying out the reaming but also keeps the instruments out of the surgeons’ line of sight so his vision is not obstructed. The grater-reamer is then used with a power tool to scrape out the uneven and diseased bone and cartilage in readiness for the shell of the cup to be implanted.
The trial shell with the plastic liner, the ball and the neck of the implants are added to the trial in the femoral shaft and brought together so the surgeon can check function and stability of the new joint.
When the surgeon is satisfied, he will insert the proper implant shell into the socket and use a long drill through the cannula to insert a screw into one of the holes in the cup shell for extra stability. Now the rest of the trial components are replaced with the actual implants and the hip is carefully put back into place. Once this is accomplished, the wound is closed and the operation is complete.
It is now the patient receives the benefit of this careful surgery, with gently handled instruments and tissues. When rehabilitation with the physiotherapists begins, they usually find there is minimal post-op pain and very little of the ‘log’ like feeling in their leg.
This procedure is called “Percutaneously Assisted Total Hip”. The term “Percutaneous” refers to the placement of the cannula which is passed just below the skin and fat of the thigh (but not through the muscle) to the hip socket and through which the rods and grater-reamers are used.