Anterior Versus Posterior Total Hip Replacement; A Patient-Friendly Rabbit Hole

There is a lot of buzz about the anterior approach to the hip. Patients want the best possible outcome for their surgery. For some patients, the idea that the anterior approach is optimal has stuck. They seek out surgeons who perform the anterior approach to the hip specifically, and they often champion the anterior approach as the approach with the fastest recovery. Surgeons also want the best outcome for patients. Accordingly, surgeons have to weigh a number of factors when recommending a surgical approach in order to achieve both short-term and long-term success. In this blog, I would like to explore the anterior, posterior, and anterolateral approaches to the hip, as well as the benefits and drawbacks of the three approaches.

Let’s start with the basics. What is an approach to the hip? An approach is the pathway the surgeon takes from the skin through soft tissue (fat, connective tissue, muscle, and capsule) to enter the hip joint and expose the joint surfaces for replacement. Once the joint surfaces are exposed, the upper part of the thigh bone (femur) is removed. The cup of the “ball and socket” joint is widened/deepend to prepare the bone for resurfacing with a new socket. Next the thigh bone is entered and its canal is widened so that a metal stem can be potted in the thigh bone. Finally, a new ball is placed on the stem and the hip is put back together. While doing work, surgeons need a good view of the hip so that they can see what they are doing. Additionally, the end of the thigh bone has to be delivered through the incision untethered so that the stem can be inserted properly while minimizing the chance of harm to the femur. This is the crux of the matter. Muscle and/or joint capsule have to be detached from the femur bone so that it can be exposed and instrumented. Figure 1 shows relevant surgical anatomy.

Figure 1. (A) Total hip replacement. (B) Anterior muscles and joint capsule. (C) Posterior muscles and joint capsule.

Direct Anterior Approach:

The anterior approach to the hip is not new. It was described by two surgeons in 1881 and 1917. The anterior approach started to regain popularity in the United States around 2005. The anterior approach involves accessing the hip joint from the front of the body. The incision is made over a natural interval between muscles. For the most part, muscles are not split and muscles are not detached from bone when entering the hip joint. Joint capsule, rather than muscle, is detached from bone to untether the femur for the most part. About 75% of the capsule is released. Usually releasing the joint capsule is not quite enough, and 1 or 2 smaller muscles (short external rotators) are partially detached from the femur. These releases allow the surgeon to position the femur appropriately for stem placement.

Pros:

In general, major muscles and their attachments to bone are largely preserved with the anterior approach. This minimal disruption supports earlier recovery because less tissue has to heal. In the past the anterior approach was associated with a lower rate of dislocation (hip popping out of socket) than the posterior approach. However, the gap has narrowed with improvement in technology and use of larger heads. It is important to note that dislocation is uncommon (1% or less) with all approaches as long as the posterior capsule is repaired when performing a posterior approach.

Cons:

The anterior approach is more technically demanding than the posterior approach. Instrumenting the femur is also harder because the femur is tethered by the muscles that were not detached. There is a slightly higher risk of breaking the femur while placing a stem. There is also a slightly higher risk of breaching (spine lingo) or perforating (joints lingo) the wall of the femur with the stem with the anterior approach. Additionally, There is a risk of injuring a sensory nerve during the exposure.

The following site has excellent diagrams of the anterior approach to the hip. AO Foundation - Anterior Approach

Posterior Approach:

The posterior approach is one of the oldest and most commonly used techniques for total hip arthroplasty. It dates back to 1874 and was modified in 1957. In the posterior approach, surgeons access the hip joint through an incision along the back of the hip. The gluteus maximus is split and 3 small posterior muscles along with the posterior capsule are detached. Two of the small external rotator muscles and the capsule are typically reattached to the femur at the end of surgery. The posterior approach was the most commonly used approach until recently, including in 2007 when a prestigious medical journal deemed hip replacement to be the surgery of the century.

Pros:

The posterior approach is a well-established technique, and many surgeons will have had more experience performing the posterior approach than the anterior approach. The posterior approach also allows a clearer view of the hip because muscles are detached from femur and retracted. This same muscle detachment makes it easier to position the femur for stem placement.

Cons:

The posterior approach involves splitting and detaching some muscles. These structures are repaired at the end of surgery and it takes time for the tissue to heal. In general, our bodies heal injuries over 3 months. The posterior approach in previous studies was associated with a higher rate of hip dislocation. As noted above, this gap has largely been closed and in some instances the anterior approach can be associated with increased chance of hip dislocation.

The following site has excellent diagrams of the posterior approach to the hip. AO Foundation - Posterior Approach

3. Anterior Based Muscle Sparing Approach:

The anterior based muscle sparing approach is an alternate anterior approach. Similar to the direct anterior approach, the surgical exposure is performed between two muscles anteriorly. Muscles are not split, and there is minimal detachment of the external rotator muscles. The original approach was described in the 1930s. It was modified and popularized by a European surgeon, Rottinger, in 2005.

Pros:

The benefits of the ABMS approach are similar to the direct anterior approach in terms of preservation of muscle attachments, early recovery, and favorable dislocation rate. The ABMS approach potentially has additional benefits. The need for partially detaching short external rotator muscles is potentially lower. Also, the ABMS exposure is extensile and can be extended distally all the way to the knee if the need arises. The ABMS approach can also be converted to a lateral approach if more exposure is needed. A recent study found similar post-operative benefits when comparing the ABMS and direct anterior approaches.

Cons:

Compared to the posterior approach, the risk of femur fracture is still higher with the ABMS approach.

Similar to the direct anterior approach, there is a slightly higher risk of breaking the femur while placing a stem compared to the posterior approach. There is also a slightly higher risk of perforating the femur than the posterior approach.

The following site has excellent diagrams of the ABMS approach to the hip.

AO Foundation - ABMS Approach

Conclusion:

The choice of approach for total hip arthroplasty depends on various factors, including the surgeon's expertise and the patient's anatomy. Each approach has its unique advantages and potential drawbacks, and the decision should be made collaboratively between the patient and the surgical team.

Ultimately, the primary goal of total hip replacement is to improve the patient's quality of life long-term. Total hip replacement has been a successful surgery for decades. As the field of orthopedic surgery advances, we still continue to make improvements, and we try to improve surgical outcomes. Anterior approaches are associated with quicker recovery initially, but the long-term success of hip replacement is the same with all approaches. Finally, the first rule of medicine is to do no harm. Sometimes this rule precludes the use of an anterior approach.

I hope you have found this information helpful!

Best regards,

Dr. B

Orthopedic Surgeon

Bristol Health

𝗡𝗼 𝗰𝗼𝗻𝘁𝗲𝗻𝘁 𝗼𝗻 𝘁𝗵𝗶𝘀 𝗽𝗮𝗴𝗲 𝘀𝗵𝗼𝘂𝗹𝗱 𝗲𝘃𝗲𝗿 𝗯𝗲 𝘂𝘀𝗲𝗱 𝗮𝘀 𝗮 𝘀𝘂𝗯𝘀𝘁𝗶𝘁𝘂𝘁𝗲 𝗳𝗼𝗿 𝗱𝗶𝗿𝗲𝗰𝘁 𝗺𝗲𝗱𝗶𝗰𝗮𝗹 𝗮𝗱𝘃𝗶𝗰𝗲 𝗳𝗿𝗼𝗺 𝘆𝗼𝘂𝗿 𝗱𝗼𝗰𝘁𝗼𝗿 𝗼𝗿 𝗼𝘁𝗵𝗲𝗿 𝗾𝘂𝗮𝗹𝗶𝗳𝗶𝗲𝗱 𝗰𝗹𝗶𝗻𝗶𝗰𝗶𝗮𝗻.

FOOTNOTES

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4716569

2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3261250

3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5525517

4. Rodrigues et al. Techniques for Minimizing Instability in Direct Anterior Approach Total Hip Arthroplasty. <https://www.aaos.org/videos> Cited 8/20/23

5. Kahn et al. Anterior-Based Approaches to Total Hip Arthroplasty: Beyond the Learning Curve. J Arthroplasty. 2022 Jul;37(7S):S552-S555.