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The Artificial Hip Joint
The life span for total hip implants has increased to 20 years or more for 80% of total hip patients.The artificial joint, called a prosthesis, is made of metal and plastic. The two parts fit together to make a new hip with smooth surfaces that glide in a natural and comfortable motion.
Before surgery, an intravenous tube (IV) is placed in your arm or the back of your hand. This tube supplies your body with necessary medicines and fluids. Also, you may begin receiving anesthesia through this tube. There are other wires and tubes attached to or placed in your body. These help monitor your body’s functions, remove excess fluid, and help you breathe during surgery. Your hip area is scrubbed with a germ killing soap. When everything is ready, the surgeon makes an incision in the skin over your hip.
A metal socket with a strong plastic lining is put into your hipbone. Then the ball portion of your thighbone is replaced with a metal prosthesis that fits in the metal socket. This prosthesis is a long metal stem with a metal ball on the end. The stem is placed firmly inside the thighbone. After both pieces are in place, an x-ray is made of your new hip joint to make sure it is in the correct position. Your incision will be closed with stitches or staples. Then you will be taken to the recovery room.
Surgery lasts about 2 to 3 hours. You will be in the recovery room for another hour or two for a total of 3 to 5 hours for surgery and recovery. Someone will update your family as your surgery and recovery progress.
The Hip Replacement Operation
The Artificial Hip Joint (Prosthesis)
There are two major types of artificial hip joint: cemented and uncemented prosthesis. Both types are widely used. The type of prosthesis used for your surgery is usually decided upon by your surgeon based on your age, your lifestyle, and the surgeon’s past experience. Each prosthesis is made up of two parts: the acetabular component—or socket portion—which replaces the acetabulum, and the femoral component—or stem portion—which replaces the femoral head.
The femoral component (femoral stem) is made of a metal stem with a metal ball on the end. Some prosthesis have a ceramic ball attached to the metal stem. The acetabular component is a metal shell with a plastic inner socket liner that acts like a bearing. The type of plastic used is very tough and very slick – so slick and tough that you could ice skate on a sheet of the plastic without much damage to the plastic.
A cemented prosthesis (left image) is held in place by a type of epoxy cement that attaches the metal to the bone. An uncemented prosthesis (right image) has a fine mesh of holes on the surface area that touches the bone. The mesh allows the bone to grow into the mesh and “become part of” the bone.
Steps in the Hip Replacement Procedure
In recent years many patients have been treated with a minimally invasive total hip replacement. The primary difference between minimally invasive and conventional approaches is how the surgeon exposes and gains access to the hip joint. With the conventional approach, the incision is 10-16 inches long, whereas minimally invasive incisions are one or two small incisions about 4 inches long; one incision is for the acetabular component and one is for the femoral component. Also, the minimally invasive approach involves splitting and dividing muscles instead of cutting them. Minimally invasive joint replacement is less traumatic, promotes better healing and the joint regains stability more quickly. There is less blood loss and the patient can sometimes go home the same day. With the convention method, there are several different approaches used to make the incision, usually based on your surgeon’s training and preferences.
After the incision is made, the ligaments and muscles are separated to allow the surgeon access to the bones of the hip joint. It is this part of the surgery that makes the ligaments and muscles somewhat weak after surgery. Until they heal, which takes about a month to six weeks, you must follow special hip precautions to prevent dislocation of your new hip joint.
Preparing the Femoral Head
Removing the Femoral Head
Once the hip joint is entered, the femoral head is dislocated from the acetabulum. Then the femoral head is removed by cutting through the femoral neck with a power saw.
Preparing the Acetabulum
Reaming the Acetabulum (Left image.)
After the femoral head is removed, the cartilage is removed from the acetabulum using a power drill and a special reamer. The reamer forms the bone in a hemispherical shape to exactly fit the metal shell of the acetabular component by removing cartilage and soft tissue.
Inserting the Acetabular Component (Right image.)
A trial component, which is an exact duplicate of your hip prosthesis, is tested to ensure that the joint you receive will be the right size and fit for you—one with good stability and without obvious dislocation. Once the right size and shape is determined for the acetabulum, the acetabular component is inserted into place. In the uncemented variety of artificial hip replacement, the metal shell is simply held in place by the tightness of the fit or with screws to hold the metal shell in place. In the cemented variety, a special epoxy type cement is used to “glue” the acetabular component to the bone.
Preparing the Femoral Canal
Preparing the Femoral Canal (Left image)
To begin replacing the femoral head, special rasps are used to shape and hollow out femur to the exact shape of the metal stem of the femoral component by cleaning out loose and spongy bone. Once again, a trial component is used to make sure the correct size and shape. The surgeon will also test the movement of the hip joint.
Inserting the Femoral Stem (Right image)
Once the size and shape of the canal exactly fit the femoral component, 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 drilled into wooden board – with a slightly smaller diameter than the nail). In the cemented variety, the femoral canal is rasped to a size slightly larger than the femoral stem. Then the epoxy type cement is used to bond the metal stem to the bone.
Your surgeon will make every effort to maintain the leg length that you had before surgery, but there is no guarantee. Once you are up and walking around, you may find that your leg is now a fraction of an inch longer or shorter than it was before surgery.
New Joint is Completed
- Attaching the Femoral Head (Left image)
- The custom fitted metal ball that replaces the damaged femoral head is attached to the femoral stem. You can see how much smaller the implant’s head is compared to the normal femoral head.
- The Completed Hip Replacement (Right image)
- You now have a new weight bearing surface that replaces your diseased hip.
X-ray of New Joint is Made
Before your incision is closed, an x-ray (image) is made to make sure your new prosthesis is in the correct position. Then the hip muscles and tendons that were temporarily moved or cut to get into the hip joint are put back or repaired and the skin is closed with stitches or staples. A drain may be used to drain off fluids. Then you’re taken to the recovery room.
Waking up in the Recovery Room
While in the recovery room, you will gradually wake up—it takes 1-3 hours for anesthesia to wear off. You may feel groggy from the anesthesia. Other symptoms of anesthesia include blurred vision, dry mouth, nausea, sleepy, confusion. You may hear sounds from the equipment around you and your nurse telling you surgery is over. You will still have tubes (oxygen) and monitors attached. The monitors provide the recovery room nurses with data on how your body is recovering. Special pneumatic stockings (pulsatile type pumps) may be on your feet and legs. These pumps massage your legs. The nurses will also remind you of your deep breathing exercises to prevent lung problems.
You will be asked to “pedal” your feet up and down. The special stockings and the pedaling exercises help prevent blood clots and help blood circulation. It is important to tell your nurse if you feel numbness, tingling, or pain in your feet and legs. If you need pain medicine, don’t wait too long to ask for it. It is easier to prevent pain than to stop pain. The recovery room nurses will keep a close watch on your recovery and help keep you comfortable.
You may notice a regular bed pillow or a V-shaped foam pillow (abduction pillow) between your legs. The pillow keeps your hip in the best position for healing. How long you use the pillow depends on what your surgeon thinks is best for you. Once in your hospital room, you may notice your chair and toilet have raised seats and have hand rails or arms.
More Articles About Hip Replacement
The information presented here—in timeline order—can help you learn what to expect when having a hip replacement from planning through recovery.
- Total Hip Replacement: a guide for surgery and recovery
- Your Visit with the Orthopedic Surgeon
- Minimally Invasive Hip Replacement
- Making Arrangements for Hip Replacement Surgery
- Pre-surgery planning and timeline
- Getting Ready for Hip Replacement Surgery
- The Hip Replacement Operation
- Complications of Hip Replacement Surgery
- On the Road to Recovery After Hip Replacement
- Hip Precautions After Hip Replacement
If you have questions after going through this information or the information brings up questions for you write them down and contact your surgeon.
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