A hip replacement is a common orthopedic procedure designed to alleviate pain and restore mobility in individuals with damaged hip joints. Among the various types of hip replacement surgeries, a bipolar hip replacement is a specific approach that involves replacing only the femoral head, which is the “ball” portion of the hip joint. Unlike a total hip replacement that replaces both the ball and the socket, a bipolar hip replacement leaves the natural hip socket, known as the acetabulum, intact. This procedure is characterized by its unique prosthetic design, featuring two articulating surfaces that allow for smoother movement and aim to reduce wear on the surrounding joint.
Anatomy of a Bipolar Hip Replacement
A bipolar hip replacement prosthesis has two articulating surfaces, enabling movements within the implant. It consists of a femoral stem, inserted into the hollow of the thigh bone (femur), and a prosthetic femoral head that attaches to this stem. The “bipolar” nature comes from the femoral head component, which is a two-part system rather than a single solid unit.
This two-part system includes a smaller, inner prosthetic head that fits within a larger, outer metallic shell. The inner head articulates, or moves, within the outer shell, creating one point of motion. The outer shell then articulates with the patient’s natural acetabulum, providing a second point of motion. This dual-bearing mechanism helps distribute forces and reduce wear on the hip socket. The outer shells are available in various sizes to match the patient’s anatomy.
Indications for Bipolar Hip Replacement
A bipolar hip replacement is used for specific medical conditions and patient profiles, especially when preserving the natural hip socket is advantageous. One primary indication is a displaced femoral neck fracture, particularly in elderly patients. These fractures can disrupt the blood supply to the femoral head, leading to its damage or death, making replacement necessary. The procedure is preferred for older or less active individuals due to its less invasive nature and quicker recovery compared to a total hip replacement.
Another condition that may lead to a bipolar hip replacement is avascular necrosis (AVN) of the femoral head. AVN occurs when the blood supply to the bone is interrupted, causing the bone tissue to die and the femoral head to collapse. Bipolar hemiarthroplasty can replace the damaged femoral head while preserving a healthy acetabulum. It is a suitable option when damage is localized to the femoral head, unlike total hip replacement which is for more extensive joint damage.
The Surgical Process and Recovery
The surgical process involves replacing the damaged femoral head with a prosthetic device. Patients receive either spinal or general anesthesia. A surgeon makes an incision to access the hip joint. The damaged femoral head is then removed from the hip socket.
After removing the femoral head, the surgeon prepares the femur to accept the prosthetic stem. The prosthetic stem is then inserted into the femur, and the bipolar head component is attached. The new prosthetic ball is placed back into the natural hip socket. Stability and range of motion are tested before the incision is closed. The surgery lasts a few hours.
Recovery begins soon after surgery, with physical therapy often starting the next day. Hospital stays usually last a few days, during which patients begin to sit, stand, and walk with assistance. Pain management is provided, and patients may receive blood thinners to prevent clots. Patients are instructed on hip precautions, such as avoiding extreme bending or twisting, to prevent dislocation.
Rehabilitation progresses with physical therapy, which focuses on restoring movement and strength. Patients use walking aids like crutches or a walker for several weeks, gradually transitioning to a cane. Most individuals can resume light daily activities within 4 to 6 weeks, though full recovery and return to more strenuous activities can take several months. Swelling and bruising are common and can take time to subside.