Direct Anterior Approach (Minimally Invasive) Total Hip Replacement

Overview

Traditional hip replacement surgery involves making an incision on the side of the hip (lateral approach) or the back of the hip (posterior approach). Both techniques involve detachment of muscles and tendons from the hip in order to replace the joint. Detachment of these muscles may result in increased pain after surgery, and often prolongs the time to fully recover by months or even years. Failure of these muscles to heal after surgery may increase the risk of hip dislocation (the ball and socket separating), which is the leading cause of hip replacement failure. Hip precautions after surgery (no bending greater than 90 degrees, no crossing legs, no excessive rotation) are generally required for this reason.

Direct anterior hip replacement is a minimally invasive surgical technique. This approach involves a 3 to 4 inch incision on the front of the hip that allows the joint to be replaced by moving muscles aside along their natural tissue planes, without detaching any tendons. This approach often results in quicker recovery, less pain, and more normal function after hip replacement. Because the tendons aren’t detached from the hip during direct anterior hip replacement, hip precautions are typically not necessary. This allows patients to return to normal daily activities shortly after surgery with a reduced risk of dislocation.

If you have any questions about direct anterior hip replacement, feel free to schedule an appointment at 206.368.6360.

Video: Direct Anterior Approach to Total Hip Replacement
-Video is for educational purposes only. Dr. Fernando has no financial ties to Stryker.

Review of the Condition

Characteristics of hip arthritis

Arthritis of the hip is a condition in which the cartilage of the hip joint thins or wears away with time. The hip joint is made up of a ball (femoral head) and socket (acetabulum)

The cartilage is a protective surface which functions as a "cushion" or padding, allowing the bones of the hip joint to move smoothly and normally against each other without friction. When the cartilage wears away, the bone is forced to rub against the bone in order to move, which can be an extremely painful condition. This increase in friction may also cause stiffness around the joint, swelling, inflammation, and even instability and falls.

Hip arthritis presents with pain in the groin approximately 90% of the time. In 10% of patients, pain may may isolated to the side of the hip or the buttock.

Arthritis of the hip is unfortunately a progressive problem, although this rate of progression is variable and difficult to predict.

Types

Hip arthritis may occur because of many reasons, although the end result (thinning or failure of the cartilage) is the common final pathway.

The most common form of arthritis is degenerative arthritis (or osteoarthritis) which is secondary to a combination of genetics, possible "wear and tear", and age.

Rheumatoid arthritis is an example of an inflammatory arthritis, wherein the lining of the joint (synovium) becomes inflamed and thickened, resulting in direct damage to the cartilage.

Avasular necrosis of the hip is a condition which results in the bone underneath the cartilage losing its blood supply and collapsing (resulting in the overlying cartilage becoming damaged). The most common causes of avasular necrosis of the hip are chronic steroid use (e.g., prednisone), alcohol abuse, and trauma.

Other causes of hip arthritis include hip dysplasia, post-traumatic arthritis, hip impingement, and rarely, infection.

The direct anterior approach is generally an option for any type of arthritis, although in patients with abnormal anatomy (e.g., hip dyplasia, post-traumatic arthritis) is may not be suitable. The direct anterior approach may also not be suitable in very obese patients, particularly in patients where the stomach rests over the top of the thigh (where the incision is made).

Similar conditions

Hip impingement (and labral tears) may also result in pain in the hip area. Hip impingement typically affects young men in their 20’s, often in patients who are active in sports. This is typically secondary to abnormal femur anatomy (CAM lesion). Hip impingement may also affect women in their 40’s. This is typically due to abnormal anatomy of the pelvis (Pincer lesion). The mismatch between the size of the ball and socket results in tears of the labrum, and typically small areas of cartilage damage. Pain from hip impingement typically only occurs with extremes of motion. Pain at rest is typically consistent with more advanced arthritis, or pain from another source.

Pain which is isolated to the buttock is often more suggestive of nerve irritation (e.g., sciatica) or lower back pain. Pain on the outside of the hip is often suggestive of hip bursitis. Rotation or movement of the hip should not exacerbate these symptoms.

Incidence and risk factors

Total hip replacement is one of the most common operation performed in the United States, with over 300,000 procedures performed yearly. This number is expected to likely double in the next 20 years, partly due to patients living longer, having higher expectation as to quality of life and function than previous generations, and having better access to health care.

The direct anterior approach is performed by a relatively small minority of surgeons performing hip replacement. This is largely due to the fact that this approach has only gained popularity in the last 10 years, primarily due to more active patients wanting a less invasive technique allowing for a quicker recover. As such, many surgeons were not trained in this advanced technique. It is generally considered more technically difficult than the other approaches, so specialized trained is often necessary.

Diagnosis

The diagnosis of hip arthritis is typically made in combination with a history of pain localized to the hip area (usually slowly progressive in nature), a physical examination which reproduces pain with motion of the hip, and x-ray finding showing narrowing of the joint space between the ball and socket.

Because cartilage is a soft tissue (like tendons and ligaments), it does appears on a xray. However, if cartilage is functioning normally, the space between the ball (femoral head) and socket (acetabulum), which do appear on xray, should be thick (roughly 5-8 mm) and symmetrical throughout. Once this space is obliterated, we call this severe, or "bone-on-bone arthritis". This is often accompanied by bone spurs and/or cysts within the bone. Patients with severe arthritis are typically the best candidates for total hip replacement.

Medications

Medications may be helpful in managing degenerative arthritis, although no medications currently exists that can reverse the process of osteoarthritis. For degenerative arthritis, anti-inflammatory medications (NSAIDS) may be helpful for the management of symptoms. Although glucosmaine and chondroitin sulfate have been marketed as effective for the treatment of arthritis, studies which have looked at these medications have not demonstrated a difference in comparison to placebo. Injections within the hip of steroid (cortisone) or lubricants (hyaluronic acid) have not been studied to the same extent as they have in knee arthritis, and are generally discouraged. Injections in the hip joint typically involve xray or ultrasound guidance, are fairly invasive, and have limited benefit.

In the case of rheumatoid arthritis, specific drugs may treat the inflammation that destroys the cartilage, and potentially halt progression. Some of these medications are administered by injection and others by mouth. Some individuals take anti-arthritic medications for their entire lives. These medications can be quite helpful, but there may be side effects. These medications should be taken under the close supervision of a rheumatologist or other physician experienced in their use.

Exercises

Gentle exercises for the hip, as long as they do not exacerbate pain, may be beneficial to maintain flexibility and range of motion. Formal physical therapy for muscle strengthening, gait training, local massage, etc. have not been shown to be beneficial for the treatment of osteoarthritis in comparison to "sham" therapy or placebo, and may be very expensive.

Physical therapy after direct anterior total hip replacement is individualized based on a patients recovery. Because no muscles or tendons are cut, there are no specific muscles which "need" to be rehabilitated because of the trauma of surgery. Some patients who continue to feel stiff or weak after the first 6 weeks of surgery may benefit from either home exercises or formal physical therapy.

Possible benefits of Direct Anterior Approach (Minimally Invasive) Total Hip Replacement

Total hip arthroplasty is one of the most effective operations available in the field of orthopedic surgery. Surgery first involves removing the arthritic ball and socket using specialized instruments. A metal stem is placed within the femur and a metal socket is placed within the pelvis. A ceramic or metal ball is then placed on the stem and a dense plastic bearing is placed within the socket. The metal components are roughened and coated with a biological material which allows a patient’s own bone to grow into the metal, which allows the metal to become rigidly fixed. The artificial ball and plastic bearing are extremely smooth, which allows the hip to function and move similar to a normal hip.

Regardless of the surgical approach, hip replacement has a success rate approaching 95% in terms of "success" (defined as an improvement of pain, function, and quality of life).

The major advantages of direct anterior hip replacement in comparison to traditional approaches include a more rapid recovery, less pain in the immediate post-operative period, more normal gait mechanics, and a more stable artificial hip without the need for hip precautions.

Regardless of surgical approach, the most important factor in terms of technical success involve placing the hip replacement components in a optimal position.

Considering surgery

Types of surgery recommended

The most effective and reliable surgical treatment of severe arthritis remains total hip replacement.

The other surgical option for severe arthritis is hip resurfacing, which may also be very effective and has the advantage of being more bone conserving (i.e. less bone is removed during surgery). Hip resurfacing has fallen largely out of favour recently in the United States because the bearing surfaces used are "metal-on"metal". Although this may be an effective bearing surface, some adverse effects have been seen in certain designs that are very sensitive to component malposition.

Total hip replacement is not recommended for patients with mild arthritis.

Direct anterior total hip replacement is an option for most patients with severe arthritis of the hip. Patients may not be suitable candidates for the direct anterior approach if they have abnormal anatomy (i.e. dysplasia, post-traumatic arthritis) or in cases of morbid obesity (i.e. body mass index greater than 35).

Who should consider Direct Anterior Approach (Minimally Invasive) Total Hip Replacement?

Joint replacement should be considered when:

1. Arthritis is affecting a patient’s quality of life
2. Arthritis is affecting a patient’s ability to function normally (i.e. putting on shoes/socks, getting out of a chair, etc)
3. Arthritis is moderate to severe on xrays
4. Patients are healthy enough to safely undergo an elective procedure
5. The benefits of the surgery outweighs the risks of the surgery

For most patients who have hip arthritis, pain is also a significant limitation. Pain is a fairly subjective measure however, and some patients who have a high pain tolerance may be able to live with pain for many years. For most patient, quality of life is the most important factor in making a decision towards surgery.

What happens without surgery?

The natural history of denegeratie arthritis is that symptoms tend to progressively worsen over time. Arthritis may have a "waxing and waning"pattern, with good days and bad, but over the course of time, symptoms have a tendency to become persistent. Typically the progression is slow, generally over several months or years, but this is generally very difficult to predict.

Arthritis is not a life threatening condition however. There is, generally speaking, never a "need" to have surgery for arthritis (like many forms of cancer for example. Arthritis which prevents a patient from being active physically (i.e. daily exercise) may have effects on a patients cardiovascular health, weight, etc. which are difficult to predict or quantify.

Surgical options

Traditional hip replacement surgery involves making an incision on the side of the hip (lateral approach) or the back of the hip (posterior approach). Both techniques involve detachment of muscles and tendons from the hip in order to replace the joint. Detachment of these muscles may result in increased pain after surgery, and often prolongs the time to fully recover by months or even years. Failure of these muscles to heal after surgery may increase the risk of hip dislocation (the ball and socket separating), which is the leading cause of hip replacement failure. Hip precautions after surgery (no bending greater than 90 degrees, no crossing legs, no excessive rotation) are generally required for this reason.

Direct anterior hip replacement is a minimally invasive surgical technique. This approach involves a 3 to 4 inch incision on the front of the hip that allows the joint to be replaced by moving muscles aside along their natural tissue planes, without detaching any tendons. This approach often results in quicker recovery, less pain, and more normal function after hip replacement. Because the tendons aren't detached from the hip during direct anterior hip replacement, hip precautions are typically not necessary. This allows patients to return to normal daily activities shortly after surgery with a reduced risk of dislocation.

Effectiveness

The likelihood of success after total hip arthroplasty has been reported as 90-95%. Success is generally defined as a significant improvement in pain, in increased ability to function normally, and an improvement of quality of life. The ‘best" hip a patient will ever have is the one they were born with, but once that hip is worn out, artificial hip replacement is the best current alternative. The longevity of a hip replacement has been reported as approximately 90% at 20 year follow-up.

Direct anterior total hip replacement aims to improve on traditional hip replacement but minimizing muscle and tendon trauma. This has been reported to results in more rapid recovery, less early post-surgical pain, more normal gait mechanics, and a more stable artificial hip. This effect may last up to 2 years, but after this time point the differences are harder to distinguish.

Urgency

Total hip replacement, generally speaking, is a 100% elective surgery. There is almost never an "urgency" for surgery from a technical perspective, although patient’s often feel an urgency from a quality of life or pain perspective. In very rare occasions, the severity of arthritis may be so bad that bone begins to be lost, which may effect the technical reliability of an operation. In these circumstance, surgery may be recommended with more urgency.

Because surgery is elective, patients should be instructed to be as healthy as possible prior to surgery in order to decrease the likelihood of complications. This includes:

1. Cessation of smoking for at least 6 weeks
2. Weight loss for achieve a body mass index of at least <40
3. Good diabetic control (HBA1c < 7.0)

Risks

The risks of total hip arthroplasty include but are not limited to the following: infection, injury to nerves or blood vessels, fracture, stiffness or instability of the joint, loosening or wear of the artificial parts, and leg length discrepancy.

Medical risks include but are not limited to: risk of anaesthesia, heart attack, stroke, blood clots in the legs or lungs, and blood transfusions.

An experienced total joint surgeon will use specialized techniques to minimize these risks, but unfortunately they can never be eliminated.

The major risk the direct anterior total hip replacement minimizes in comparison to tradition approaches is the risk of instability or dislocation (ball and socket separating). This is because the major stabilizers of the hip joint are the muscles and tendons on the back of the hip (posterior structures) and the side of the hip (abductors), neither or which are violated with a direct anterior approach. Because of this, traditional hip precautions (e.g. no bending, no crossing legs, etc) are generally not necessary after direct anterior total hip replacement.

Managing risk

Many of the risk of total hip arthroplasty can be managed effectively if they are promptly identified.

Infections, though rare, are extremely serious complications that must be managed early and aggressively. Any deep infection involving a total hip replacement must be managed with surgery. This may as simple as washing out the infection and replacing the ball and plastic liner, or may be as complicated as removing all of the components and placing a temporary hip replacement made of antibiotics.

Total hip dislocations typically involve a "reduction" of the dislocation joint in the emergency department, but also may require surgery to correct depending on the underlying problem.

Fractures, though undesirable, rarely affect the outcome of an operation if identified and treated at the time of surgery. Nerve and blood vessels injuries are extremely rare (1 in 2000 roughly), but can be devastating complications.

Loosening of components is a possibly of any mechanical device. Surveillance of implant through x-rays (typically every 2 years) may help minimize this risk.

Preparing for surgery

Timing

Total hip replacement is a "quality of life" operation, not a life saving operation. Hip replacement surgery can therefore be delayed to any time which suits a patients personal timeline for recovery. In rare cases where there is significant progressive bone loss (i.e., inflammatory arthritis, dysplasia of the hip) surgery may be encouraged in a semi-urgent manner.

For patients who are employed, the timing of surgery is often more important that someone who may be retired. Direct anterior total hip replacement may allow you to do desk work immediately, although many patients require 2 weeks before they feel comfortable enough to do this full time. More intensive work or return to sports require anywhere between 6 weeks and 3 months before possible.

Costs

The surgeon's office should provide a reasonable estimate of:

• the surgeon's fee,
• the hospital fee, and
• the degree to which these should be covered by the patient's insurance.

Surgical team

Direct anterior total hip arthroplasty is a technically demanding operation, generally considered more so than the traditional approaches. The benefits may be significant, (particularly for active patients), but should never come as a compromise to the expedience, reliability, and precision of the operation.

Direct anterior hip replacement should be performed by a surgeon experienced in this approach, either through fellowship training or through cadaveric exercise. You should ask your surgeon about their experience, volume, and training with this approach.

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