Total hip replacement is a surgery that is utilized to relieve pain from an arthritic hip joint. The hip joint is a basic ball and socket joint. The ball (femoral head) is lined with cartilage and the socket (acetabulum) is also lined with Cartilage. In a normal hip the smooth cartilage facilitates motion in the joint. When the cartilage becomes thin and the bone underlying the cartilage comes in contact with bone on the opposite side of the joint this causes pain. Many people call this bone on bone arthritis. This condition or status of the joint can be seen on x-rays. Not everyone who has x-ray evidence of arthritis has pain. Therefore in order to be considered for joint replacement you should have x-ray evidence of arthritis and pain that is associated with the arthritis that limits activity.

Arthritic Hip
picture courtesy of DePuy Orthopedics

What is a hip replacement?

Hip replacement is a surgical procedure that is performed to relieve pain in the hip joint that is causing the patient to have limited ability to perform normal activity. The acetabulum surface is replaced with a metal cup or shell that is usually made from titanium or titanium like metal. Once the metal cup is placed in the bone the inside of the metal cup is lined with either plastic, metal or a ceramic material to create a new smooth joint surface. The ball at the top of the femur is removed. A new ball is placed in the femur by attaching a ball to a metal stem that is placed inside the femur. The ball is either made out of metal, or ceramic. The new metal or ceramic ball will then provide a smooth surface to move against the replaced cup surface.

Arthritic Hip
picture courtesy of DePuy Orthopedics

When Am I ready for Hip Replacement?

Hip replacement is an elective surgery. No two patients are the same. Some patients may wait longer for hip replacement surgery then another patient. Some patients are willing to tolerate the discomfort or limitations for a longer period of time. Hip replacement surgery is primarily an operation to relieve pain and increase the patients function because the pain has been minimized or eliminated. While the operation will improve flexibility the operation is not primarily performed to change flexibility. The decision or need for hip replacement should be individualized based on the patient and their symptoms not solely on an x-ray. The decision to undergo hip replacement should be made after consultation with an orthopedic surgeon and an understanding of the risks and benefits of the surgery and the individual needs of the patient.

What Material Will Be Used to Reconstruct My Joint Surface?

There are several FDA approved options for what combinations of surfaces you can have in your hip joint. The long standing problem with joint replacement is that the joint will eventually wear out. Research in joint replacement has focused on finding surfaces that are less likely to wear out over time. In basic terms the smoother the surface and the harder the surface the greater the longevity of the joint.

various components
picture courtesy of Smith + Nephew Orthopedics

Metal Ball/Plastic Socket

This combination is the original joint replacement. One of the problems with this combination was that the plastic surface would degrade over time creating debris in the joint. The body would react to this debris and the reaction would cause loosening of the implants. In order to eliminate this as a problem, the plastic has undergone considerable technological advancement over the past 20 years. The plastic has been made much harder by changing the molecular structure of the plastic. Plastic wear rates are much less than what they were in the past. The plastic now is often referred to as highly cross linked polyethelene. The metal ball is often made from a smooth metal called cobalt chrome. This surface combination is likely best utilized in lower demand individuals with limited activities or of advanced age.

Ceramic Ball/Plastic Socket

This combination utilizes a ceramic ball on a highly cross linked polyethylene socket as described previously. The ceramic is a harder and smoother surface than a metal ball. The theory behind this is that the smoother harder surface of the ball will result in less wear of the plastic over time. This combination of material is probably best suited for individuals who are younger, active, and athletic. The younger more active patient will place higher demand on their hip for a longer period of time and needs a more durable surface for longevity of the hip replacement.

Ceramic on Poly
Ceramic Ball / Plastic Socket
picture courtesy of Smith + Nephew Orthopedics

Metal Ball/Metal Socket

This combination is referred to as a metal on metal hip. This combination provides a very hard and smooth surface and is felt to provide a long lasting hip replacement particularly in young active patients. There are several potential issues with this joint surface. The metal produces ions and the ions are absorbed in the blood stream and can be seen in the urine, blood and tissue of the body. While there is no known long term effect of this, there is also no long term data. There is also a condition called metalosis that can occur with metallic debris from the wearing of the joint surface. The metallic debris can cause bone destruction and loss. This situation seems to occur when the placement of the components are not in the best possible position. There has also been a recent manufacturer’s recall of specific metal on metal total hip implants. The FDA has also now required all manufacturers of Metal on Metal implants to report failure rates of this type of implant. This combination of surfaces is suggested for high demand young active individuals.

Metal On Metal
Metal Ball / Metal Socket
picture courtesy of DePuy Orthopedics

Ceramic Ball/Ceramic Socket

This combination is referred to as a ceramic on ceramic hip. This combination provides a very hard and smooth surface and is felt to provide a long lasting hip replacement particularly in young active patients. There are several potential issues with this joint surface. The hip may squeak, this seems to be the result when the implants are not in optimal position. There is also a special type of wear pattern that can develop called stripe wear that may lead to the need to revise the hip surgically. Because the ceramic surface is so hard it can also be very brittle and has been known to fracture with a high impact load.

Ceramic On Ceramic
Ceramic Ball / Ceramic Socket
picture courtesy of DePuy Orthopedics

What type of Joint Surface is Best for Me?

I believe that the hip replacement utilized should be individualized and custom selected based on the individuals activity level, age, medical conditions, bone quality and bone geometry. No two patients are the same and therefore the implant selected should best match the needs, demands and anatomy of the patient.

What Manufacturer Has the Best Implant?

All of the major medical device companies with a full line of joint replacement products produce high quality Hip Replacement Implants. The designs of the implants are similar with some minor nuances between manufacturers. Ultimately you want the implant placed in an optimal position in your body to restore mechanics, equalize leg lengths and prevent dislocation. The positioning of the components is likely more important than the type of Implant utilized.