Anterior Approach for Muscle Sparing/Precision Implant Placement Technique

     What is it? It is a technique that is a step further and safer than minimal invasive hip surgery.

(1) It uses an entirely different surgical approach (anterior) to get to the hip joint so that no muscles are cut - unlike the minimal invasive technique.

(2) The cut, of course, is shorter than the 8 to 10 inches standard cut.

(3) The surgeon sees every step of the surgery in getting to the hip joint. Replacing the joint is fully seen on a TV screen which is used in conjunction with a standard operating table.

(4) The implant used is designed to find its own way into the femur. This further prevents any potential in placing the implant in the incorrect position.

This muscle sparing/precision implant placement technique is preferred by Dr. Menendez in total hip replacement.

How is it done? This technique uses a standard operating room table. No special table is needed for the surgery.

Why is this important? When a shorter incision is used and the surgeon needs to see inside the cut open hip, an alternate to the eyes is to see with x-rays. The reversed operating room tables allow the low–power x-ray to pass through. The area around the hip area is clear of metal. So, the low-power x-ray beams are not blocked by the metal parts of the operating room table.

The advantage is that at every critical step in preparing the bone, a low-power x-ray beam machine can be used to check out the hip area and let the surgeon see on a TV screen what exactly he is doing. This machine is used to check before, during and after every critical step of the surgery. It directs the surgeon as to where the cut is to be made. It tells the surgeon if the instruments are placed in the ideal way to make the cut. The x-ray is shown on a TV screen and the surgery is like playing a video game. Since this x-ray vision is done during surgery (real time), there is no need to wait until the surgery is over in the recovery room to find out if everything fits properly. The moment the artificial parts are put in, the surgeon knows if they are in the proper positions. If any changes need to be made, it can be done right away. So, this is the first part of the precision implant placement technique.

The hip joint is reached from the front of the body (Anterior Approach). The hip joint is a lot closer to the skin in the front than the back of the body. There are less soft tissue and muscles covering it. So, the cut in the skin needs to be only 2-1/2 inch long. The length of the cut this is almost the same as the minimal invasive technique.

Since this is a relatively short cut, it has to be made in the exact place.
If it is made in the wrong place, then the hip joint will be missed. So, the exact location of the cut to be made is fixed by a special instrument and checked on the TV screen.

After the skin is cut open, there are two muscles on top of the hip joint (Tensor Fascia Lata on the outside and Sartorius on the other side). They are not cut but pushed aside (retracted) with standard instruments. The second layer of muscle (Rectus Femoris) is also retracted to one side. In several short steps, the hip joint capsule is reached. The capsule is then cut open and the ball and socket hip joint is exposed. So, this is the ‘muscle sparing’ part of this technique. No muscles are cut in order to get to the hip joint.

The head of the leg bone (femur) is cut with a power saw and the ‘ball’ is removed. This gives room now for preparing the hip socket (acetabulum). This is done by a special instrument that looks like a chess grader but round. When the power of this

instrument is turned on, it spins and shapes the hip socket into a hemisphere. Every step mentioned is seen by the surgeon using low dose x-ray and shown on the TV screen. The artificial socket (acetabular) implant is then installed by ‘press fit’ into the socket.

One or more screws are then used to further secure the acetabular implant in bone. Now, the surgeon turns to work on the femur side. The reversed table allows the heel of the leg to be dropped to the floor and the leg is turned outwards. Then the inside the femur (femoral canal) is opened up with instruments. They are called broaches or rasps. A special instrument is used to lift up the femur. Starting with the smallest broach, bigger and bigger braches are used one after another. Again they are done under the guidance from the TV screen. This process takes away the weak ‘honeycomb like’ bone inside the femur. It is stopped when the broach sits tight in the femur. It is important to seat the implant in hard bone (cortical) because of the support needed. The corresponding femoral implant is then inserted (press fitted) into the femur.

Since the incision is smaller than usual, not only is the femoral implant inserted into the femur under direct x-ray vision, but a particular implant is also made of titanium alloy. Also, the shape (design) is based on the research of the shapes and sizes of numerous femurs. So, the implant was designed to match the majority of the patients. This is important because the human body does not have a straight line but have all sorts of curves. The implant is to fit the femur like a hand in glove. This implant has been used since 1996. This femoral hip implant ‘finds its own way’ into the canal and give a best fit. This is the second part of the precision technique.

In many instances, the other hip joint is good. So, it can be used as a comparison to the side that is replaced on the TV screen. This allows the surgeon to adjust the length of both legs. The suitable length ball component is then placed on the femoral implant. But the most important part in a total hip is the stability of the reconstructed hip joint. So, the surgeon checks the stability by moving the hip joint in various directions to see if the artificial hip joint can dislocate. Then the final decision is made as to how long the leg should be. A final picture of the replaced hip joint is then seen on the TV screen.

When the TV screen shows a satisfactory picture, the hip joint is ready to be close back up. The soft tissue over the artificial hip joint is stitched back together with sutures. The skin is closed metal staples. This closure part takes only a few minutes and the operation is complete.

The patient is transferred from the operating table to a bed and wheeled away to the recovery room.

So, by using a short anterior approach, the hip joint can be exposed under direct vision. The hip joint is reached without cutting any muscles. With the reversed table and a low-power x-ray beam, all the bone cuts can be seen before, during and after on the TV screen. This makes sure that all the steps are done properly. Then with a ‘home-seeking’ hip implant, a precision hip placement is made.