Dr. Murphy most commonly performs total hip arthroplasty using an exposure called the Superior Capsulotomy. This is a technique that he developed in 2002 and 2003. The aim of the technique is to maximally preserve the soft tissues surrounding the hip joint. It is considered a "minimally invasive hip replacement" technique, although all hip replacement surgery is invasive to a greater or lesser extent. This procedure can be performed in about 97% of the primary hip replacements that Dr. Murphy performs and he has used it more than 800 hip replacements thus far.
Current data demonstrate that this procedure – combined with computer assisted surgical navigation - is actually safer than conventional total hip arthroplasty and results in a dramatically accelerated recovery.
The philosophy behind and evolution of this technique is described in many sources below. The first link below is a link to a video animation of the surgery. This video is intended for orthopedic surgeons to view, but it gives you a good idea of the method.
Superior Capsulotomy Animation on youtube.
The clinical results of this technique, compared to a conventional technique, have been published in the peer-reviewed literature:
Please see below for more information about the philosophy
and evolution if this surgical technique and also the other
methods of performing "minimally invasive" total
hip arthroplasty. Links to additional publication are also
available below.
Note: You must have Adobe Reader 6 to save PDFs
to your personal computer and to print them.
Information about Less and Minimally Invasive Total Hip Arthroplasty Techniques:
Performing total hip arthroplasty while taking steps to minimize trauma to the surrounding tissues has great potential for facilitating recovery after hip replacement surgery.
As noted above, I currently use tissue preserving, minimally invasive techniques when performing total hip arthroplasty in more than 95% of patients. Nearly all surgeries are performed with computer-assisted surgical navigation. Patients inappropriate for this surgery are generally those with more dramatic deformities and /or those with previous hardware or multiple previous surgeries. Importantly, patient size typically does not preclude one from qualifying for this method of tissue preserving surgery.
"Minimally invasive total hip replacement" is a broad term that is used to describe a wide variety of surgical techniques.
Some techniques are traditional operations performed through smaller incisions while others are fundamentally new operative techniques.
Some techniques are relatively safe while others have a track record of causing significant problems for a large percentage of patients.
If appropriate techniques are used by an experienced surgeon, minimally invasive total hip arthroplasty can be safe and very beneficial. Conversely, patients can experience outcomes far worse than they would have had minimally invasive techniques not been applied. And so the potential benefits as well as the potential risks must be carefully assessed.
The surgeon performing the operation together with his or her direct experience is of great importance when considering minimally invasive hip replacement surgery.
Because "minimally invasive hip replacement" is subject to interpretation, it is important to review the anatomy of the hip joint and the different techniques of replacing the joint to better understand the issues.
The hip joint is surrounded by a hip joint capsule which is much like a thick skin that surrounds the femoral head and socket. Outside the hip joint capsule are small muscles in the back of the joint called the short external rotators. The back half of the hip joint capsule and the short external rotators are important structures that serve to prevent dislocation following total hip arthroplasty.
On the side are the gluteus medius and minimus muscles that together are called the abductors. If these muscles are weak either before or after surgery, the patient will limp.
On the front of the joint there are several powerful muscles including the iliopsoas muscle, the sartorius muscle, the tensor fascia femoris muscle, and the rectus femoris. These muscles allow the leg to be lifted forward in a lying, sitting, or standing position.
There are many ways a surgeon can access the joint to perform a total hip replacement which makes the hip a very interesting joint to work on, but a bit confusing to anyone who is not a surgeon.
Listed below is a brief description of common hip exposures together with their respective advantages and disadvantages.
We review each to provide a better understanding of why I developed and routinely use the superior capsulotomy technique for most primary and some revision total hip arthroplasties.
The Posterior Approach
The posterior approach is probably the most common surgical technique used for hip arthroplasty in the U.S. today. Basically, the back half of the hip joint capsule and short rotators are incised to provide access to the joint. This surgery is safe, reliable and in most cases can be completed very quickly and easily. The downside of this technique is a greater risk of dislocation – due to the fact that the back of the hip joint capsule and short rotators are incised. In fact, this technique has the highest incidence of hip dislocation.
Two methods are used try to compensate for this at problem. One is to instruct the patient to restrict hip joint motion after surgery by giving the “dislocation precautions”. The second is to attempt to repair the hip joint capsule and short external rotators to their original state. Importantly however, even if both of these methods are used, the patient cannot pursue unrestricted motion after surgery as the repair could disrupt. Since unrestricted motion is one of the important goals when trying to improve a patient’s post-op experience this method doesn’t really afford the opportunity to achieve that goal.
Many surgeons employ what is called a mini-posterior exposure – which is essentially the same technique performed through a smaller incision -but each of the limitations list above still apply.
The Direct Lateral Exposure
The Direct Lateral Exposure is another common technique for hip replacement surgery. From 1991 to 2002 it was also the exposure that I routinely used to perform hip replacement surgery and during that period, I felt it was the best exposure for most routine total hip replacement operations.
The technique involves spreading the gluteus medius muscle fibers and moving the front part of the gluteus medius, hip joint capsule and gluteus minimus muscle from the front of the femur. The implants are then inserted through this interval.
The advantage of this technique is that the back half of the hip joint capsule and the short external rotators are undisturbed and as a result, the hip is extremely difficult to dislocate. Specifically, the incidence of dislocation is less than 1 in 200, even when the patient is not advised to restrict hip joint motion in any way. Once the gluteus medius and gluteus minimus muscles heal, the hip joint is very close to its preoperative state, with all of the important muscles around the hip joint back where they were. I still feel that this is the best technique for total hip replacement in certain patients.
The disadvantage of this technique however, is that the patient must protect the muscles around the hip after surgery to ensure that proper healing takes place. The problem is that a lot of people don’t have very much pain a few weeks after surgery and prefer not to use their crutches. Bearing weight too early causes muscle contraction that can pull the muscle repair apart before it heals. This can lead to a limp and pain. The ideal hip operation would enable the patient to tolerate both unrestricted motion and unrestricted muscle contraction immediately after surgery. Needless to say, this is very rare.
The mini-direct lateral approach can be considered a minimally invasive technique too, but again, it is basically the same operation through a smaller incision. If you are really interested in how this surgery is performed, the Video Journal of Orthopedics, together with the Journal of Bone and Joint Surgery, produced a video that recorded me performing one of these operations. It is available on line at http://www.vjortho.com/cgi/content/abstract/4059.
The Anterior Exposure
Anterior exposures to the hip joint have been routinely used since the 1960's – before hip replacement was commonly performed in the United States. This technique was employed mainly for cup arthroplasty surgery - an earlier version of hip prosthesis surgery. Anterior exposures to the hip are used currently for joint preserving surgery such as periacetabular osteotomy for hip dysplasia or surgery to relieve femoro-acetabular impingement. Anterior exposures have also been used for total hip replacement and were popularized by Judet in Paris.
Minimally-invasive total hip replacement surgery using the anterior exposure is becoming increasingly popular in Europe and in some parts to the United States. Joel Matta, M.D. from Los Angeles and William Hozack, M.D. from Philadelphia have used this method very effectively for their patients.
The anterior exposure for total hip replacement is especially good for placement of the socket component but it has significant limitations for implantation of the femoral stem component into the femur. While it is a good surgical technique, it is not one I use very often.
The Two Incision Minimally Invasive Techniques
A number of two-incision surgical techniques exist but perhaps the best known technique was popularized out of Rush-Presbyterian Hospital in Chicago. The approach - which received a lot of media attention in 2002 and 2003, is used by very few surgeons in 2009. It involves placing the socket in through the front of the hip joint and putting the femoral stem in through a small incision in the back.
Since its introduction, my personal opinion has always been that this technique is not as reliable as it needs to be and is potentially very harmful. There is general agreement on this point of view now which is why the technique is used much less frequently now than it was 5 or 6 years ago. The basic problem is that, while it is easy to put the cup into the socket, the stem is placed into the femur in a blind fashion because it cannot be directly seen by the surgeon. The abductor muscles are perhaps the most important muscles around the hip joint and they are not directly visualized or protected during surgery. This means that they are susceptible to injury which can be a very dramatic problem for some patients who have had this surgery. One recent study showed that muscle injury from this particular minimally invasive technique was much greater and much more variable than for traditional techniques. Mardones et al, Muscle Damage After Total Hip Arthroplasty Done with the Two-Incision Minimally Invasive and the Mini-Posterior Techniques. A more recent prospective randomized study demonstrated that there were no advantages of this technique as compared to a miniposterior exposure in terms of length of stay or recovery.
The second major problem is that the fit between the femoral stem and the femur itself is a critical issue. If the stem is not firmly fitted, it can loosen right away. If the stem is too firmly fitted, the femur can break. Very skilled surgeons who have adopted this technique have reported breaking the femur in 20% of patients when they first starting using this method. If such an event occurs, the incision must be extended beyond what would have been necessary had the patient and surgeon elected a more traditional approach in the first place. In addition, if any of the soft-tissues that surround the opening in the femur get interposed between the femur and the femoral prosthesis when it is inserted, then the femoral bone may never have a chance to grow into the surface of the prosthesis.
The third problem with this technique is that it can’t be applied to the vast majority of patients in need of hip replacement surgery. Many patients, for size or other reasons, are not candidates for this type surgery.
While this technique gained popularity from 2001 to 2003, it has been progressively abandoned by surgeons who previously embraced it due in large part, to the limitations noted above.
The concept of Tissue Preserving Total Hip Arthroplasty
The popularity of and considerable patient focus on minimally invasive hip replacement techniques must be considered in terms of what is and is not important.
Hip replacement surgery in its traditional form is superbly reliable. If we are going to try to improve it, we have to protect patients from any significant increase in the likelihood of being worse off than they would have been had traditional techniques been employed. What is really important is to allow patients unrestricted motion after surgery (as patients can have with the direct lateral approach) and to allow unrestricted muscle strengthening after surgery (as patients can have with the posterior approach). It is also important to be able to see and protect the major muscles around the joint and to be sure that the components fit and are well seated, without breaking the bone. If this is accomplished, patients will recover rapidly and reliably.
Starting in the Fall of 2002, with increased focus on precise placement of l hip replacement components while minimizing the impact on the surrounding soft tissues, it became clear that the femoral stem could be inserted through a small incision in the superior hip joint capsule, behind the strong abductor muscles and in front of the posterior capsule and short rotators. This was done by preparing the femur for the stem before the femoral head was removed.
The advantages of doing this became progressively clear and they include the following:
The femur is more stable and stronger if the head is still in place which makes it less likely that the femur will crack during surgery.
Exposure is easier since instruments can be placed around the neck of the femur as it is still in place.
The hip never needs to be dislocated to complete the surgery. This means that the leg is never placed in a position unachievable in a normal hip.
This also means that the surrounding tissues don't need to be disturbed as much.
With the stem being placed through a small incision in the superior hip joint capsule, the cup was initially placed through the front - underneath the strong abductor muscles.
This method allowed insertion of the components while preserving all of the important structures around the hip joint – the posterior hip joint capsule and short rotators that protect against dislocation, and the abductor muscles that provide the strength for walking without a limp. This technique also proved beneficial in that it allows patients to more quickly and easily recover. After gaining more experience with this method in 2002 and early 2003, it also became clear that if the right surgical instruments were designed, that both the socket and the stem could be safely implanted through a single incision in the superior hip joint capsule - in between the short external rotators and abductors in nearly all patients. After we made those instruments, the second incision became unnecessary. The operations performed to date have nearly always been completed in concert with computer-assisted surgical navigation - although the surgery can also be completed without computer assistance. The surgical technique and clinical results of this method have been presented at many national and international meetings and have been published in several journals and textbooks, including peer-reviewed scientific journal (Clinical Orthopedics and Related Research).
This work was recognized by the International Society for Computer Assisted Orthopedic Surgery in 2005 with the award for Best Clinical Presentation at the Annual Meeting in Helsinki, Finland.
While there are many ways to access the hip joint to perform a total hip replacement, I feel that this method is the safest and most efficient way to preserve and protect all of the important structures around the hip joint and to facilitate both early recover and long term function.
The following links are all either manuscripts or abstracts
that we have been published on the topic of tissue-preserving
total hip replacement using a superior capsulotomy. They are generally listed from most recent to least recent. Please
note that publications posted are for educational purposes
only and should not be reproduced without permission of the
publisher.
Murphy
SB and Tannast M. Evolution of Total Hip Arthroplasty:
Computer Assisted, Minimally Invasive Techniques Combined
with Alumina Ceramic-Ceramic Bearings. In D'Antonio J and
Dietrich M eds. Bioceramics in Joint Arthroplasty. Darmstadt,
Germany: Steinkopff Verlag. pp119-129, 2005.
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