Anterior Total Hip Replacement

Anterior Hip Replacement is a minimally invasive hip surgery to replace the hip joint without cutting through any major muscles surrounding the hip. The surgical procedure involves a small incision in front of the hip, anterior, as opposed to an incision on the side or back of the hip. It is referred to as more muscle sparing surgery because it utilizes a true inter-nervous plane in accessing the hip joint. Unlike the posterior or lateral approach the gluteus maximus or gluteus medius are kept intact.

In order to understand anterior hip replacement and its benefits over traditional hip surgery, it is important to understand the normal anatomy of the hip.

Normal Anatomy

The thigh bone, femur, and the pelvis, acetabulum, join to form the hip joint. The hip joint is a “ball and socket” joint. The “ball” is the head of the femur, or thigh bone, and the “socket” is the cup shaped acetabulum.

The joint surface is covered by a smooth articular surface that allows pain free movement in the joint.

The cartilage cushions the joint and allows the bones to move on each other with smooth movements. This cartilage does not show up on X-ray, therefore you can see a “joint space” between the femoral head and acetabular socket.

Pelvis

The pelvis is a large, flattened, irregularly shaped bone, constricted in the center and expanded above and below. It consists of three parts: the ilium, ischium, and pubis.

The socket, acetabulum, is situated on the outer surface of the bone and joins to the head of the femur to form the hip joint.

Femur

The femur is the longest bone in the skeleton. It joins to the pelvis, acetabulum, to form the hip joint.

The upper part is composed of the femoral head, femoral neck, and greater and lesser trochanters.

What is arthritis?

Arthritis is a general term covering numerous conditions where the joint surface (cartilage) wears out.

The joint surface is covered by a smooth articular surface that allows pain free movement in the joint. This surface can wear out for a number of reasons; often the definite cause is not known. 

When the articular cartilage wears out, the bone ends rub on one another and cause pain.

There are numerous conditions that can cause arthritis and often the exact cause is never known. In general, but not always, it affects people as they get older and is called Osteoarthritis.

Other causes include:

  • Childhood disorders such as a dislocated hip, Perthe’s disease, or slipped epiphysis
  • Growth abnormalities of the hip, such as a shallow socket, may lead to premature arthritis
  • Trauma (fracture)
  • Increased stress from overuse
  • Avascular necrosis (loss of blood supply)
  • Infection
  • Connective tissue disorders
  • Obesity- the additional weight puts extra force through your joints which can lead to arthritis over a period of time
  • Inflammation such as in Rheumatoid arthritis

In an arthritic hip:

  • The cartilage lining is thinner than normal or completely absent. The degree of cartilage damage and inflammation varies with the type and stage of arthritis.
  • The capsule of the arthritic hip is swollen
  • The joint space is narrowed and irregular in outline; this can be seen in an X-ray image.
  • Bone spurs or excessive bone can also build up around the edges of the joint.

The combinations of these factors make the arthritic hip stiff and limit activities due to pain or fatigue.

Diagnoses

Hip conditions should be evaluated by an Orthopaedic surgeon for proper diagnosis and treatment.

Your surgeon will perform the following:

  • Medical History

  • Physical Examination

Diagnostic Studies may include:

  • X-rays: a form of electromagnetic radiation that is used to take pictures of bones.

There is no blood test to diagnose osteoarthritis.

Surgical Introduction

Anterior Hip Replacement is a minimally invasive, muscle sparing surgery using an alternative approach to traditional hip replacement surgery. Traditionally, the surgeon makes the hip incision laterally, on the side of the hip, or posteriorly, at the back of the hip. Both approaches involve cutting major muscles to access the hip joint. With the anterior approach, the incision is made in front of the hip enabling the surgeon to access the hip joint without cutting any major muscles. A special operating table is used that facilitates various anatomical positions enabling the surgeon to replace the hip joint anteriorly.

Potential benefits of anterior hip replacement compared to the traditional hip replacement surgery, may include the following:

  • Smaller incision
  • Minimal soft tissue trauma
  • Reduced post op pain
  • Less blood loss
  • Shorter surgical time
  • Faster healing time
  • Less scarring
  • Earlier mobilization
  • Less post-operative restrictions
  • Reduced hip dislocations
  • Decreased hospital stay

Surgical Procedure

Anterior Hip Replacement is performed in a hospital operating room under general or regional anesthetic depending on you and your surgeon’s preference. You will be placed supine, on your back, on a special operating table that enables the surgeon to perform your hip replacement anteriorly. Fluoroscopic imaging is used during the surgery to ensure accuracy of component positioning and to minimize leg length inequality.

The surgeon makes one incision to the front of the hip. The surgeon then pushes the major muscles aside to access the hip joint to begin the replacement.

The femur (thigh bone) is separated from the acetabulum (hipbone socket). The acetabulum (socket) is prepared using a special instrument called a reamer. The acetabular component is then inserted into the socket. This is sometimes reinforced with screws or occasionally cemented.

A liner, which is made of plastic is then placed inside the acetabular component. The femur (thigh bone) is then prepared. The femoral head which is arthritic is cut off and the bone prepared using special instruments to exactly fit the new metal femoral component.

The femoral component is then inserted into the femur. This may be press fit relying on bone to grow into it or cemented depending on a number of factors such as bone quality and surgeon’s preference. The real femoral head component is then placed on the femoral stem. This can be made of metal or ceramic. The artificial components are fixed in place.

The surgeon withdraws the instruments and sutures the incision closed. The incision is then covered with a sterile dressing.

For Anterior Hip Replacement patients, however, hip precautions are not necessary. Because the major muscles are not cut, the risk of dislocation is theoretically lessened enabling the patient more freedom of movement after surgery. Some studies have found that the rehabilitation is faster for patients as well in the immediate postoperative period.

Common post-operative guidelines after Anterior Hip Replacement include the following:

  • You may bend your hip immediately after surgery and bear full weight when comfortable.
  • Your surgeon will prescribe pain medications to keep you comfortable at home.
  • Keep the incision clean and dry.
  • You will be given specific instructions regarding activity and rehabilitation. You will not have to follow standard hip precautions.
  • Physical therapy most often consists of only walking.
  • If you have increasing redness or swelling in the wound or temperatures over 101.4 degrees you should call your doctor.
  • If you are having any procedures such as dental work or any other surgery you should take antibiotics before and after to prevent infection in your new prosthesis. Consult your surgeon for details prior to undergoing these procedures.
  • Your hip replacement may go off in a metal detector at the airport.
  • Eating a healthy diet high in protein and not smoking will promote healing.
    • Infection: Infections can occur superficially at the incision site or in the joint space of the hip, a more serious infection.
    • Fractures: This is rare but can occur during or after surgery. This may prolong your recovery or require further surgery.
    • Nerve damage: Trauma to nerves may be temporary or permanent and can cause numbness, tingling, pain, and weakness.
    • Hemarthrosis: A condition caused by excess bleeding into the joint after the surgery is completed. This may require additional surgery to irrigate the joint and evacuate the blood.
    • Blood clots (Deep Venous Thrombosis or DVT): A DVT can form in the calf muscles and can travel to the lung, a life threatening condition called pulmonary embolism. If you get calf pain or shortness of breath at any stage, you should notify your surgeon.
    • Leg length inequality: It is very difficult to make the leg exactly the same length as the other one. The Anterior approach for Hip Replacement can improve this outcome however; there are some occasions when it is simply not possible to match the leg lengths. All leg length inequalities can be treated by a simple shoe raise on the shorter side.
    • Wound irritation: Your scar can be sensitive or have a surrounding area of numbness. This normally decreases over time and does not lead to any problems with your new joint.
    • Wear: All joints may eventually wear out. The more active you are the quicker this will occur. In general 80-90% of hip replacements survive 15 years.
    • Failure to relieve pain: This is rare but may occur especially if some pain is coming from other areas such as the spine.

Risk factors that can negatively affect adequate healing after hip replacement include:

  • Poor nutrition
  • Smoking
  • Obesity
  • Alcoholism
  • Chronic Illness
  • Steroid Use