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Direct Anterior Minimally Invasive Hip Replacement (AA THR)

The hip joint

The hip joint forms where the top of the thigh bone (femur) meets the socket of the pelvic bone (acetabulum). The top of the femur is shaped like a ball and fits snugly in the socket formed by the acetabulum. The hip bones are covered with a layer of slick cartilage, which cushions and protects the bones while allowing smooth movement. Ligaments connect the bones of the joint to hold them in place and add strength and elasticity for movement. Muscles and tendons play an important role in keeping the joint stable and mobile.

Traditional total hip replacement

Diagram of traditional total hip replacement

Total hip replacement, also called total hip arthroplasty, is the surgical replacement of the ball and socket of the hip joint with implants. There are three main components used in total hip replacement. The acetabular shell replaces the hip socket. The femoral stem and ball replace the top of femur.

These components may be made of any number of materials, including metal, ceramic and/ or polyethylene (medical-grade plastic).

In traditional hip replacement surgery, a surgeon makes an incision along the side of the leg to access the hip joint. The natural head (ball portion) of the femur (thigh bone) is removed during surgery. The remaining preparation of the femur and acetabulum (socket) involves reshaping to allow solid, accurate alignment of the hip components. The femoral stem is inserted inside the thigh bone, and the acetabular shell is inserted inside the socket of the pelvis.

The Direct Anterior Approach – muscle saving, tissue sparing

The Direct Anterior Approach to total hip replacement is an alternative to traditional hip replacement surgery that provides the potential for less pain, faster recovery and improved mobility. Unlike traditional hip replacement surgery, this technique allows the surgeon to work between the muscles and tissues without detaching them from either the pelvis or thighbones. The hip joint is approached between the tensor fascia lata and Sartorius/Rectus Femoris muscles.

The potential benefits of the Direct Anterior Approach are:

  • Possible accelerated recovery time because key muscles are not detached during the operation.
  • Fewer restrictions during recovery. Although each patient responds differently, this procedure allows patients to move more freely. They may bend their hip and bear their full weight immediately or soon after surgery.
  • Possible reduced scarring because the technique allows for one relatively small incision. Since the incision is on the front side of the leg, you may be spared from the pain of sitting on scar tissue.
  • Potential for stability of the implant sooner after surgery, resulting in part from the fact that the key muscles and tissues are not disturbed during the operation.
  • The Anterior Approach requires less tissue disruption, which may lead to faster rehabilitation.
Diagram of Direct Anterior Approach

Advanced surgical table & instrument

The Anterior Approach takes advantage of a technologically advanced surgical table and special Instruments. A high-tech operating table is often used to help improve access to the hip and achieve excellent alignment and positioning of the implant through the minimally invasive surgical site.

Diagram of advanced surgical table and instrument

Improved patient recovery

The Direct Anterior Approach procedure requires less tissue disruption. It is combined with an ERAS programme (Enhanced Recovery After Surgery) which leads to a faster rehabilitation after surgery. Traditional hip replacement surgery, in contrast, typically requires strict precautions for six to twelve weeks.

Restrictions/Precautions for the first 6-12 weeks


  • You may move your leg backwards but must not stretch the leg back further than the muscles will naturally take it.
  • No outwards rotation of the hip over 45 degrees
  • No sitting on your bottom with your legs crossed (Buddha Position)


  • Allowed to bend (flex) over 90 degrees
  • Normal sitting
  • Normal toilet height
  • Normal sleeping positions but with a pillow between knees in side lying

Treatment Guidelines


At pre assessment the operation will be explained to you and how the rehabilitation will be different to a traditional hip replacement along with the length of stay, this is considerably reduced with most patients only staying one night. You will be taught if appropriate how to use elbow crutches and if you wish may take those home to practice with. You will be asked to fill out a questionnaire called an Oxford scoring. This allows us to assess your improvement following your operation.


You will be admitted on the morning of the operation. After the operation you will return to the ward. Later that day if you have recovered well enough your physiotherapist or nurse will come and get you out of bed for the first time. We will start with sitting on the edge of the bed and if you manage that will have a go at standing and walking. The nursing staff will continue to encourage you to mobilise during the evening.

The next morning (day 1) you will be encouraged to sit out for breakfast and get washed and dressed. The physiotherapists will mobilise you on crutches and teach you some exercises and complete the stairs. It is also important that you lie flat on your back if you are able for 30 minutes twice a day to gently stretch tight hip muscles. Later that day you will be ready for discharge. Occasionally some patients need to stay until the next day. An outpatient physiotherapy appointment will be made before you go home.


You will normally continue to use your crutches until your first outpatient physiotherapy appointment. You may at this point be weaned to one crutch or a stick. If you are not ready for this you will be reassessed at your next appointment, everybody recovers at a different pace. Your exercises will also be progressed, the physiotherapist will begin working on strengthening your muscles as well as increasing the amount of movement you have in your hip. Physiotherapy will continue until you have fully recovered.