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Total Hip Replacement Implant (Zimmer Orthopedics)

A total hip replacement replaces your arthritic hip joint and eliminates the damaged bearing surfaces that are causing you pain. The design of the implant offers you renewed stability and function. Hip replacement surgery has a very high success rate, and can offer an incredible quality of life improvement to some patients. Hip replacement can relieve pain, help your hip joint work better, and restore normal walking and other movements. Your doctor may recommend it if you have hip damage and pain that physical therapy, medicines and exercise don’t help.

Hip replacement surgery is performed over 300,000 times each year in the U.S. to repair severe hip damage. In a hip replacement, the surgeon removes degenerate cartilage and bone from the hip joint and replaces them with prosthetics. This surgery is used to accomplish long-term pain relief and increased mobility.

Hip replacement surgery has a very high success rate, and can offer an incredible quality of life improvement to some patients. Hip replacement can relieve pain, help your hip joint work better, and restore normal walking and other movements. Your doctor may recommend it if you have hip damage and pain that physical therapy, medicines and exercise don’t help.

In order to appropriately consider hip replacement, patients should be informed as to the mechanics of the hip joint and the options available for treatment.

The Parts of Your Hip Joint

The hip joint is a common ball joint comprised of just two bones, the head of the femur (thigh bone) and the socket (acetabulum). The femur has a head, a neck and the trochanters, large on the outer side and lesser on the inner side below which is the shaft. The bones themselves have a hard outer shell, the cortex, with a cavity inside. Surrounding the joint are other tissues including articular cartilage, different ligaments, synovial membrane and a fibrous capsule. More about the hip joint >>

Hip Replacement Processes

There are two parts to a hip replacement – acetabular preparation and femoral preparation.

In the acetabular preparation, special mushroom-shaped reamers are used to remove the diseased and damaged cartilage and bone. The area is power washed to remove all blood, fat and debris and thoroughly dried. Once the bone is dry, cement (if used) is put in and pressure applied to force the cement into the honeycomb of the bone.  Implants comprised of a metal shell and a liner are then inserted. Sometimes the shell is fixed in place with two or three screws through into the hip bone.

For the femoral preparation, the femoral head is removed and ream the shaft out with specially shaped rasps. The area is power washed to remove all blood, fat and debris and thoroughly dried. Once the bone is dry, cement (if used) is put in and pressure applied to force the cement into the honeycomb of the bone. Implants comprised of a metal stem and a ball for the head are inserted. More about hip replacement processes/approaches >>

Hip Replacement Implants

Your surgeon will select the design of the hip replacement and size of femoral ball to give you the range of motion and stability that you need to function. There are several different choices of hip implants to consider, each using varying materials and having different pros and cons:

• Metal Ball and Polyethylene Liners
• Ceramic Ball and Polyethylene Liner
• Metal Ball and Metal Liner
• Ceramic Ball and Ceramic Liner

Mechanism of a Hip Implant: During a total hip replacement procedure the socket is cleared of the worn cartilage and bone and a metal cup shaped shell put in its place. A plastic liner is inserted into this metal shell. A metal stem is inserted into your thighbone (femur). Attached to the neck of the stem is a hip ball (sizes vary from 28-58mm) which fits into the socket’s liner. Together, the ball and liner create the new joint. In terms of fixation, your surgeon has the choice of anchoring the hip implants securely to bone using either cement fixation or fixation by ‘bone ingrowth’. More about hip implants >>

Hip Resurfacing Option

For some patients, a total hip replacement may not be the best solution for their hip pain because it can mean the possibility of one or more revisions being needed later in life. Hip resurfacing, however, leaves more of the bone in place making revision easier.

Partial hip resurfacing, or hemi-resurfacing, is the most bone-conserving approach to hip surgery. During this procedure, only the femoral head (where the leg joins the hip) is reshaped and resurfaced. The hip socket (acetabulum) is left completely intact. The obvious benefit with partial resurfacing is that the patient keeps most of his or her own bone, which allows for easier revisions in the future (if one becomes necessary).

Should there come a time that revision to total hip replacement becomes necessary, less bone is excised during hip resurfacing which should make the procedure to change to a THR simpler. This procedure is, however, most commonly used to repair broken hips, as opposed to osteoarthritis. More about hip resurfacing >>

Robotics, Computer Assisted Surgery (CAS), and Minimally Invasive Surgery (MIS)

Increasingly, orthopedic surgeons are looking to computer-assisted robotic surgical techniques to enhance the hip replacement process – the theory being that computers can enhance the precision and accuracy of hip and knee replacement surgeries. Through computer-assisted surgery, it is possible for your surgeon to obtain a 3-D visualization of the joint which can make it possible to achieve a better alignment of the implant joint.

Minimally Invasive Surgery is when very small incisions are made to carry out the surgery. In hips, MIS is keyhole surgery but in knees what most surgeons actually practice is minimal incision surgery. This simply means that they use a shorter incision. Incisions merely have to be big enough the get the cutting guides and the implants in. More about robotics, CAS, and MIS >>