HIP ARTHRITIS

Osteoarthritis is the most common type of hip arthritis.Also

called wear-and-tear arthritis or degenerative joint disease,

osteoarthritis is characterized by progressivewearing

away of the cartilage of the joint. As the protective cartilage is

worn away by hip arthritis, bare bone is exposed within the joint.

Hip arthritis typically affects patients over 50 years of age. It is

more common in people who are overweight, and weight loss

tends to reduce the symptoms associated with hip arthritis. There

is also a genetic predisposition of this condition, meaning hip

arthritis tends to run in families. Other factors that can contribute

to developing hip arthritis include traumatic injuries to the hip and

fractures to the bone around the joint.

Assessing Symptoms

Hip arthritis symptoms tend to progress as the condition worsens. What is interesting about hip arthritis is that symptoms do not always progress steadily with time. Often patients report good months and bad months or symptom changes with weather changes. This is important to understand because comparing the symptoms of hip arthritis on one particular day may not accurately represent the overall progression of the condition.

The most common symptoms of hip arthritis are:

• Pain with activities

• Limited range of motion

• Stiffness of the hip

• Walking with a limp

• Groin pain

• Knee pain

• Thigh pain

Evaluation of a patient with hip arthritis should begin with a physical examination and x-rays. These can serve as a baseline to evaluate later examinations and determine progression of the condition. Sometimes injection into the hip joint using X-ray guidance will help make a better diagnosis, using novacaine and cortisone.

Anatomy

The hip joint is located where the thigh bone (femur) meets the pelvic bone. It is a “ball and socket” joint. The upper end of the femur is formed into a round ball (the “head” of the femur). A cavity in the pelvic bone forms the socket (acetabulum). The ball is normally held in the socket by very powerful ligaments that form a complete sleeve around the joint (the joint capsule). The capsule has a delicate lining (the synovium). The head of the femur is covered with a layer of smooth cartilage which is a fairly soft, white substance about 1/8 inch thick. The socket is also lined with cartilage (also about 1/8 inch thick). The cartilage cushions the joint, and allows the bones to move on each other with very little friction. An x-ray of the hip joint usually shows a “space” between the ball and the socket because the cartilage does not show up on x-rays. In the normal hip this “joint space” is approximately 1/4 inch wide and fairly even in outline.

Need For Replacement Surgery

OA of the hip can be caused by a hip injury earlier in life. Changes in the movement and alignment of the hip eventually lead to wear and tear on the joint surfaces. The alignment of the hip can be altered from a fracture in the bones around or inside the hip. If the fracture changes the alignment of the hip, this can lead to excessive wear and tear. Cartilage injuries, infection, or bleeding within the joint can also damage the joint surface of the hip.Not all cases of OA are related to alignment problems or a prior injury, however. Scientists believe genetics makes some people prone to developing OA in the hip.

Scientists also believe that problems in the subchondral bone may trigger changes in the articular cartilage. As mentioned, the subchondral bone is the layer of bone just beneath the articular cartilage. Normally, the articular cartilage protects the subchondral bone. But some medical conditions can make the subchondral bone too hard or too soft, changing how the cartilage normally cushions and absorbs shock in the joint.

Avascular necrosis (AVN) is another cause of degeneration of the hip joint. In this condition, the femoral head (the ball portion of the hip) loses a portion of its blood supply and actually dies. This leads to collapse of the femoral head and degeneration of the joint. AVN has been linked to alcoholism, fractures and dislocations of the hip, and long-term cortisone treatment for other diseases.

About Surgery (Hip Replacement Implants)

The surgeon begins by making an incision on the

side of the thigh to allow access to the hip joint.

Several different approaches can be used to make

the incision. The choice is usually based on the

surgeon’s training and preferences.Once the hip

joint is entered, the surgeon dislocates the femoral

head from the acetabulum. Then the femoral head

is removed by cutting through the femoral neck with

a power saw.

Attention is then turned toward the socket. The surgeon

uses a power drill and a special reamer (a cutting tool

used to enlarge or shape a hole) to remove cartilage

from inside the acetabulum. The surgeon shapes the

socket into the form of a half-sphere. This is done to make sure the metal shell of he acetabular component will fit perfectly inside. After shaping the acetabulum, the surgeon tests the new component to make sure it fits just right.

In the uncemented variety of artificial hip replacement, the metal shell is held in place by the tightness of the fit or by using screws to hold the shell in place. In the cemented variety, a special epoxy-type cement is used to anchor the acetabular component to the bone.

To begin replacing the femur, special rasps (filing tools) are used to shape the hollow femur to the exact shape of the metal stem of the femoral component. Once the size and shape are satisfactory, the stem is inserted into the femoral canal.

Again, in the uncemented variety of femoral component the stem is held in place by the tightness of the fit into the bone (similar to the friction that holds a nail driven into a hole that is slightly smaller than the diameter of the nail). In the cemented variety, the femoral canal is enlarged to a size slightly larger than the femoral stem, and the epoxy-type cement is used to bond the metal stem to the bone. Once the surgeon is satisfied that everything fits properly, the incision is closed with stitches. Several layers of stitches are used under the skin, and either stitches or metal staples are then used to close the skin. A bandage is applied to the incision, and you are returned to the recovery room. Most modern artificial hip joints should last 20 years or longer without wearing. But this can depend on how much stress you put on the joint, how much you weigh, and how well your new joint and bones mend.