The hip joint is a ball-and-socket joint where the ball is formed by the head of the femur or thigh bone and the socket is formed by a cavity in the pelvic bones called the acetabulum.
A partial hip replacement is a surgery to replace the head of the femur with an artificial implant. The procedure is also called hip hemiarthroplasty.
Unlike a total hip replacement, the socket of the joint is not replaced during a partial hip replacement.
The implant used to replace the head of the femur consists of a ceramic or metal ball fixed on a metal stem.
There are two types of partial hip replacements:
Unipolar and bipolar
In a unipolar hip replacement, the prosthetic ball articulates directly with the natural socket
In a bipolar hip replacement, the ball is inserted into a larger ball which articulates with the natural socket. Using a bipolar hip replacement may have certain advantages. Your surgeon will decide the best option for your situation.
Partial hip replacement may be performed immediately after an injury, often with little time for preparation. You will typically require a few days’ stays at the hospital. You will need help during your recovery either at home or at a rehabilitation facility.
Partial hip replacement is performed under general or regional anesthesia. During the procedure, a surgical cut is made over the side of the hip to expose the hip joint. The head of the femur is dislocated from the socket and is separated from the rest of the femur. The cut end of the femur is hollowed out to fit the metal stem which may be fixed in place by cement or may have a porous coating that allows the bone to grow into it. The unipolar or bipolar artificial head is fixed to the stem and inserted into the pelvic socket.
Your surgeon will evaluate hip movement to see if the joint is stable and moves freely. Once your surgeon is satisfied with the range of motion, the incision is then closed.
Following surgery, you will receive medications for pain control. You will be encouraged to walk and start physical therapy as soon as possible. Therapy will be continued at home or at a rehabilitation unit.
You will be advised to avoid certain positions and activities until your hip has completely healed.
Following recovery from a partial hip replacement, you will be able to perform most of your daily tasks however, certain activities such as running, climbing, heavy lifting, and sports such as tennis, which place a lot of stress on the hip joints, are best avoided. While exercising, low-impact activities are recommended.
Advantages and Disadvantages
A partial hip replacement may provide good joint stability but the movement of the implant within the socket can cause wearing of the cartilage lining leading to pain. Your doctor may recommend a bipolar head implant for better results.
Risks and Complications
As with any surgical procedure, a partial hip replacement may be associated with certain risks and complications such as:
- Blood clots
- Poor wound healing
- Changes in leg length
- Implant loosening
- Hip dislocation
- Nerve injury
A partial hip replacement preserves the anatomy of the hip joint and may be recommended for certain hip fractures. It is ideal for those who are not very active as it can restore basic movement and function however certain activities such as sports should be avoided.