Total Hip Replacement

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What is a hip replacement?

There are two main types of hip replacement surgery (also known as hip arthroplasty) – Total Hip Replacement (THR) and Partial Hip Replacement (hip hemiarthroplasty). Both types of surgery involve removing the worn-out or damaged areas of the hip and replacing them with a prosthetic implant.

The hip is a ball and socket joint, with the femoral head being the “ball” and the pelvic acetabulum acting as the “socket”. In both types of hip replacements, the femoral head is replaced with a prosthetic implant. The main difference is that in a total hip replacement (THR), the acetabulum is replaced by a second prosthetic implant that serves as the new socket; conversely, in a partial hip replacement, the acetabulum is not replaced.

A partial hip replacement is usually offered to older patients with lower activity levels who suffer an injury to the femoral head or neck, but who have a normal pelvic acetabulum. A total hip replacement (THR) is the gold standard for active patients who have hip fractures, arthritis, or other severe diseases involving the hip joint. Your surgeon will help you make the best choice, based on the degree of joint damage and your activity levels.

Who needs a hip replacement?

Patients with hip arthritis, hip fractures and avascular necrosis (disruption of blood supply to the hip) are common candidates for hip replacement surgery. If you have frequent hip pain, or less commonly lower back, thigh or knee pain, you may have arthritis of the hip. Arthritis is a condition caused by degeneration of the cartilage in your joint over many years of use and/or trauma and can vary in severity.

When mild, it may initially only cause occasional pain when exercising or climbing the stairs. As it worsens over time, it may become a debilitating condition that affects your ability to walk and participate in the daily activities that you enjoy, such as going out with family and friends, taking holidays, or even going to the store.

When you visit a doctor for treatment for hip arthritis, you may initially be recommended to start on physiotherapy, painkillers and/or hip injections to help with the pain and stiffness. As arthritis progresses, these conservative measures will often no longer be sufficient, and hip replacement surgery would be an effective way to relieve hip discomfort and restore function, so that you can once again lead an active healthy lifestyle and participate in the activities that you enjoy.

In this article, we’ll be sharing more on the different types of hip replacements available, as well as the benefits and risks of the Direct Anterior Approach (DAA) technique of hip replacement surgery.

What is the Direct Anterior Approach?

Broadly, there are several methods that hip replacement surgery can be performed – the posterior, lateral, and anterior approaches.  Each approach is respectively named after the location where the incision is made to gain access to the hip joint.  In Singapore, the posterior approach is the most common, however, the Direct Anterior Approach (DAA) has emerged as an important technique used by surgeons subspecialised in hip surgery.

What is the Difference Between the Direct Anterior Approach and the Posterior Approach?

The posterior approach is more commonly performed than the direct anterior approach, as this is the method that most orthopaedic surgeons are familiar with in Singapore.  The Direct Anterior Approach (DAA) is a far more technically challenging technique that requires specialised training to perform safely, and is routinely performed by only a relatively small number of surgeons locally.

The advantage of the Direct Anterior Approach is that it is a minimally invasive surgical (MIS) technique that typically does not involve cutting across the muscles around the hip joint.  As a result of this muscle-sparing technique, patients who undergo DAA hip replacement have less pain, faster recovery, more rapid restoration of walking ability and better early hip function when compared to the posterior approach.  In fact, many patients are able to walk on the same day after DAA hip replacement surgery!

In the posterior approach, several large muscles around the hip have to be cut for the surgeon to access the joint.  Although these muscles will be repaired after the hip prosthesis has been implanted, a longer time is required for healing and recovery after the posterior approach when compared to the muscle-sparing Direct Anterior Approach.  In addition, the prosthetic hip joint may have better stability when the operation is done via DAA, which could reduce complication rates and afford patients better outcomes.

How the Direct Anterior Approach Hip Replacement Surgery is Performed

Before the surgery, you will have a consultation with your surgeon to discuss the type of surgery and implant that would be most appropriate for your condition.  A hip X-ray (and sometimes an MRI scan) will be performed to enable the surgeon to assess the extent of damage in your hip joint, and to plan for the surgery (if required).

During the surgery, anaesthesia will be administered so that you can be asleep and not feel pain throughout the procedure.  In the Direct Anterior Approach (DAA), a short approximately 10cm incision will be made along the front of the upper thigh, and the hip muscles are gently spread apart (but not cut) to gain access to the hip joint.  Once the hip joint has been accessed through this muscle-sparing technique, the areas of damaged bone and cartilage will be carefully removed to make space for the hip implant to be fitted in place.  After the implant has been fitted, your surgeon will thoroughly assess the length, alignment, stability and movement of your new hip joint before completing the operation.

After the surgery, you will undergo physiotherapy and rehabilitation, and there is a good chance you will be able to walk with your physiotherapist on the same day.  Since the Direct Anterior Approach is minimally invasive (MIS), the expected recovery time is 4-6 weeks or less, with early hip function after DAA having been shown to be superior to the posterior approach.


Choosing the Direct Anterior Approach (DAA) comes with a host of benefits, such as:

  • Less pain and quicker recovery – DAA is a hip muscle-sparing approach that minimizes muscle and soft tissue injury, meaning you will experience less pain and be able to heal faster than with the posterior approach.
  • Rapid return to walking and activities – By minimizing muscle injury, hip function and strength is restored more quickly, and you will be able to more rapidly resume walking and return to your daily activities.
  • Shorter hospital stay – Enhanced recovery after surgery means a shorter hospital stay, which also leads to a lower chance of getting infections and other complications.
  • Better stability – Hip replacement done through the Direct Anterior Approach tends to have better stability and lower risk of dislocation, affording patients more confidence in their implants during daily use.
  • Fewer restrictions – For patients undergoing the posterior approach, there may be various restrictions such as not squatting or bending the hip too much for up to 3 months or longer. However, if you opt for the Direct Anterior Approach, these restrictions are typically not necessary and you will be able to benefit from the full use of your new hip joint!

As with any surgery, there are some risks as well, although these are generally uncommon:

  • Infection – Prosthetic joint infection is a rare but serious complication, and may require revision surgery to eradicate the infection and replace infected components of the hip prosthesis.
  • Injury to nearby nerves & blood vessels – This is a rare complication that exists for every surgical approach, and your surgeon will take comprehensive precautions to protect the neurovascular structures around the hip joint during surgery.
  • Hip joint dislocation – This is an uncommon but serious complication of hip replacement surgery; the Direct Anterior Approach (DAA) technique may allow better stability after surgery
  • Limb length discrepancy – The replaced hip may be a bit longer or shorter than the unreplaced side, but the vast majority of replaced hips are within 1cm of the unreplaced side, which has been shown to not affect walking and hip function. The DAA technique allows for a more accurate assessment of limb length during surgery than in the posterior approach.
  • Loosening of the implant – As the implant and its surrounding bone undergoes wear and tear from repeated use over many years, the implant may loosen and require revision surgery; however, approximately 90% of hip implants are still functioning well even after 15 years.
  • Fracture around the implant – Falls and other trauma can result in the bone breaking around the hip implant, which may require surgery to fix.
  • Blood clots – Deep vein thrombosis, a condition where blood clots form in veins, is a side effect of prolonged bed rest and immobilisation; but since the DAA technique of hip replacement provides for a quicker recovery time, you’ll be able to move about sooner and reduce your risk of blood clots.
Am I a candidate for this surgery?

Patients with hip arthritis, hip fractures and avascular necrosis (disruption of blood supply to the hip) are common candidates for hip replacement surgery, which can be performed through either the posterior approach or Direct Anterior Approach (DAA), depending on the surgeon’s expertise and patient factors.

Most patients are suitable for hip replacement through the Direct Anterior Approach. However, patients with significantly abnormal hip anatomy (such as after a previous failed hip surgery) or morbid obesity (body mass index higher than 35) may not be suitable for DAA hip replacement, and may be recommended the posterior approach instead.

Do consult with your doctor to find out if you are eligible for minimally invasive hip replacement surgery through the Direct Anterior Approach, so that you may benefit from significantly less pain and more rapid recovery after your hip replacement.