It is important to know about anterior hip replacement precautions. There aren’t that many! After 7 years and almost 1000 anterior total hips, I would conclude that this procedure is “better” than the old “gold standard” of posterior total hip replacement. While no long term results studies are available that do a double-blinded comparison of techniques, my own results show the success rates are higher with the anterior hip procedure. My patient’s satisfaction rate is greater with the anterior hip. Much of the reason is the vastly improved short term recovery time. This includes the beneficial feature of not having to constantly worry about the hip popping out (dislocation) which is a much more common occurrence in posterior total hip replacement. My own results also show a lower infection rate (there is better blood supply in front which decreases infection risk). There have been less problems with blood clots (much faster mobility, and less twisting of the veins at surgery on the HANA table). There is much less leg length inequality (because we see the hip on Xray before closing, which results in better position of the implants. Maybe most importantly to some is there is clearly less pain, and because of that, less narcotic medications give, which results in an overall better feeling after surgery. LESS PAIN is a good thing!!!
You may have had one hip done through a posterior approach years ago, which cuts through the gluteus maximus muscle and external rotator muscles as a routine part of the hip exposure. You probably remember how much you stressed and complained about having to follow rigorous precautions to prevent hip dislocation. You could not turn on your side in bed, and you could not bend over to pick up your keys if they dropped. The reason that this is necessary in the posterior approach is the soft tissues are damaged and lax, and the hip can more easily pop out until they heal. healing time is 3 or 4 months, so you will have to be careful for a long time. In the posterior approach, no traction table is used to dislocate the hip and leverage is used to pop the hip out, stretching veins and vessels. In distinction, the anterior approach leaves the soft tissues intact, which holds the hip in better.
If a ball and socket were held together by gravity and asymmetric muscle tension from intact anterior muscles passing over the joint, the tension might change in different positions. The soft tissue envelope would become lax in full flexion or full extension due to the shortening of some muscle tissues with those motions. The hip might “fall out” of the socket posteriorly, or it might get “levered out”, by a twisting motion. This is why you must not flex (lift) the thigh past 90 degrees to the body while twisting after a posterior hip. You must sleep on your back with a pillow between your legs to keep the legs apart. The pillow pushed the hips into abduction, which is a more stable position. Crossing the legs (adduction) is strictly prohibited for 3 months! Looking back, I’m amazed at how many people got through that difficult period. This recovery from posterior hip surgery demands a significant period of “no work” and “no travel”. Most patients would choose the anterior approach, given a choice, as this method has a much faster recovery with very little in the way of hip precautions.
The posterior anatomy to the left shows how the short external rotator muscles must be cut in order to open the posterior capsule of the hip and dislocate the hip joint. It takes longer for those muscles to heal back, and the opening that is left increases the risk of dislocation.
Precautions after the anterior hip are minimal. So minimal in facet, that I am sending some motivated patients home the SAME DAY as the surgery, without the worry or concern of hip dislocation. I also do not order physical therapy post op on the anterior hips. One of their functions was to remind the patient not to cross their legs or to bend too far forward. It is possible to pop out an anterior hip, but thankfully, it is very rare (about 1 in 200 cases, versus 12 in 200 posterior hip cases). When we use the special HANA traction table, we “pull” the hip out, without cutting any muscles. It then “snaps back” into position at the end of the case with all crossing musculature intact. Like rubber bands that were stretched, they then work to hold the hip in place through a full range of motions. Not only is there less pain, but patients can do just about anything they want from a daily function standpoint immediately. Every day I hear stories from my patients about how fast they did this or that activity. Many use the adjectives “amazing”, “miraculous” and “unbelievable” when describing their recovery. Particularly those that have had a posterior total hip in the past on the other side.
Since the table uses external rotation and extension along with traction to lever the hip out of place, I do tell patients to not purposely do a Yoga “bridge” type motion post-op until the anterior capsule tissue has had a chance to heal. The anterior capsule is the only soft tissue cut to get the implants in. The capsule is made up of strong ligaments that eventually re-grow (it takes about 4 months for the capsule to re-form) and heal the hip in even more solid. The ileofemoral ligament or hip capsule must be cut to get the metal implants into position! So we will tell you to avoid excessive external rotation of the foot (twisting the foot to the outside – like Charlie Chaplin does – along with avoiding hip hyperextension (like when you do a backwards dive off a diving board). It turns out that most activities of daily living have a component of hip flexion (knee up towards head), which is a safe position after anterior total hip because the posterior capsule and muscles are intact – the hip cannot fall out the back that way!
Thankfully, there appears to be minimal nerve pain fibers in the capsule and the bone which is cut. The operation occurs in an inter-nervous plane. No nerves = no pain! It turns out, most of the pain after posterior THR come from the cut muscles! So since we don’t cut any muscles with the anterior hip approach, there is much less pain! Remarkably, some patients have no pain at all. I do not prescribe routine physical therapy after the Anterior Hip.
It turns out we used to prescribe PT more to remind patients about dislocation precautions than we did to facilitate recovery. The anterior hip recovers very naturally, with walking, simple home exercises, and isometrics. We will show you these exercises to do at home before you leave the hospital. I like patients to go to the supermarket, Costco, Walmart, or Home Depot and push one of the big carts around the store. That is the best rehab program I have seen for anterior hips! The recovery is so fast it is truly amazing.
Now if only we can get the Total Knees to recover as fast as the Anterior Total Hips (we are making progress with our minimally invasive total knees) – that would be really great!
Stuart C. Kozinn MD
Medical Director of The Scottsdale Joint Center and the Scottsdale Healthcare Total Joint Center