In my last blog post, I discussed minimally invasive surgery with regard to hip replacement. While new techniques, instruments and prostheses have been developed specifically for minimally invasive surgeries, there are many well-established approaches to hip replacement. Two which are receiving the most attention are the traditional posterior approach and the direct anterior approach. I would like to share my experience with both procedures.
The traditional posterior approach is the most commonly used in the United States and throughout the world (about 70 percent). The majority of teaching institutions in the United States continue to instruct as well as perform the traditional posterior as their primary approach. The mini posterior approach essentially is the same as the traditional posterior, however a smaller incision is made and less soft tissue is exposed. Very important with both the traditional posterior and the mini-posterior approaches, if the surgeon is not able to visualize critical structure adequately, or if a problem were to arise such as a fracture, then either approach can easily be adjusted.
Over the last six years, I have performed more than 2000 primary or first-time total hip replacements using the mini-posterior approach and I am aware of only one patient who dislocated his hip because he fell down stairs. His hip ball was put back in the socket and he has done beautifully since.
The mini-posterior approach involves separating the muscle fibers of the large buttock muscle located at the side and the back of the hip. Because the muscle fibers are separated, not cut, the nerve path is not disturbed and the muscle is not injured. Advantages of this procedure include:
- The mini-posterior is considered a more straightforward approach then the anterior, resulting in lesser complication rates.
- There is significantly less bleeding with the mini-posterior approach, notably reducing the necessity of a blood transfusion after the surgery.
- In my experience, there is a faster and more-consistent recovery with the mini-posterior.
- I have seen a number of patients who were reconstructed with the anterior approach who developed painful anterior scarring after the procedure. This then becomes a very difficult problem to solve.
- Because the mini-posterior is more straightforward, many surgeons think it provides an increased margin of safety for the patient, because the incision can easily be extended if exposure is poor, or if a fracture occurs.
- Because of the straightforward exposure of the femur, there is less risk of femoral fracture or poor implant positioning. Should one of these events occur during a mini-posterior procedure, they are easier to recognize and correct.
- Because visualizing the femur is easier, an experienced surgeon can choose the most appropriate femoral implant rather than just the one that is easiest to implant, taking into account the patient’s bone quality, activity level and age.
- There is less risk of neurological injury.
- No special surgical equipment is required when performing a mini posterior.
Direct Anterior Approach
The direct anterior approach involves dissecting between the natural intervals of the two main muscles located at the front of the hip and upper thigh. Because the patient is lying on his back, it facilitates using a fluoroscope or moving x-ray throughout the procedure. This does expose the patient to more radiation but can help with component positioning and sizing. There tends to be a lesser incidence of posterior instability with the anterior approach. On the other hand, there may be a slightly increased incidence of anterior instability. Along these same lines, there is a smaller incidence of sciatic nerve injury with the anterior approach but an increased incidence of femoral nerve injury. This is because the nerve is located in front of the hip. Also, because technically it is easier, many patients are being reconstructed with very short stems which are press fit into the bone during an anterior approach. These stems are a new design, and therefore do not have an established track record. Historically short press fit stems have not done well. The hope is that these new designs will, but time will tell.
Disadvantages of the anterior approach include:
- The nerve which supplies sensation to the front and side of the thigh is vulnerable.
- The intended interval between the front thigh muscles can be difficult to recognize and there has been an associated increase in injury to the femoral nerve or vessels.
- The physical build of some patients increases the difficulty. This is particularly true if the person is overweight, has very muscular thighs or is short.
- It also is more difficult for patients with some patterns of arthritis such as “protrusio,” which causes the worn out ball to migrate inward rather than upward into the socket.
- As noted above, because the femur is difficult to visualize, component positioning, sizing, and stability are more likely to be compromised. Also, the choice of femoral stem is more likely to be influenced by the approach and not the person’s anatomy and hip mechanics.
- More soft tissue trauma can result do to this increased difficulty in exposure and then gaining more exposure if necessary. Occasionally this even requires making a second, separate incision.
Although I am trained in both approaches and have trained surgeons in both approaches, I have stopped using the anterior approach because I saw my patients get well faster, bleed less, and have a more predictable result when I performed the surgery using a mini-posterior approach. I’ve come to the conclusion that perceived benefits do not outweigh the risks with the anterior approach, especially when I can achieve the same or more using the mini-posterior.
It is so important to stay focused on the outcome of your hip replacement surgery: excellent results both short- and long-term with minimal risk of injury or complication, and not lose sight of the real goal, which is to create a perfectly positioned reconstructed hip that is stable, balanced and has the best possible chance of lasting more than twenty years.
Ultimately, you and your surgeon should discuss all procedures and technologies available and then trust that your surgeon will choose the best course of treatment and surgical procedure for you.
I know the most important decision you will make is choosing the doctor who will perform your surgery. You should not proceed unless you know in your heart that you will be taken care of in a manner that has the best chance of giving you as perfect a result as possible.