Hip replacement surgery is a common orthopedic procedure performed to alleviate pain and restore mobility in a damaged joint. A partial hip replacement, formally known as a hemiarthroplasty, addresses damage localized to one specific part of the hip. This surgery involves replacing the damaged portion of the joint with an artificial implant to return the patient to a mobile and pain-free state.
Anatomy of the Partial Replacement
The hip is a ball-and-socket joint where the rounded head of the thigh bone, or femur, fits into the cup-shaped socket in the pelvis, called the acetabulum. A partial hip replacement focuses solely on the femoral component of this joint. The surgeon removes the damaged femoral head, the “ball” portion, and replaces it with a prosthetic component, typically made of metal or ceramic.
This new artificial ball is attached to a stem that is inserted down into the hollow channel of the femur. The natural acetabulum, the hip’s socket, is left completely intact. This differs significantly from a total hip replacement, where both the femoral head and the acetabulum are replaced with artificial components.
Medical Situations Requiring Partial Replacement
The decision to perform a partial hip replacement is tied to the cause and location of the joint damage. This procedure is primarily recommended for individuals who have sustained an acute traumatic injury, most often a displaced fracture of the femoral neck. This type of fracture, common in older adults following a fall, can compromise the blood supply to the femoral head, making repair difficult or impossible.
The partial replacement is preferred when the patient’s acetabulum is healthy and shows no signs of significant arthritis or wear. Surgeons often choose this option for elderly patients who have lower physical activity levels or pre-existing health conditions, as it is a shorter and less extensive operation than a total hip replacement. Total hip replacement is reserved for patients with chronic, degenerative conditions like severe osteoarthritis, where both the ball and the socket are damaged.
Overview of the Surgical Procedure
The procedure typically begins with the administration of anesthesia, which may be general or spinal. The surgeon then makes an incision to access the joint. The specific surgical approach—anterior (front), posterior (back), or lateral (side)—is chosen based on factors like the fracture pattern and the surgeon’s preference.
Once the hip joint is exposed, the surgeon carefully removes the fractured femoral head and neck. The inner portion of the femur is prepared to accept the prosthetic stem. This stem is inserted into the bone, and it may be secured using bone cement for immediate stability, or it may be uncemented, relying on bone growth for long-term fixation.
A metal or ceramic ball replaces the natural femoral head and is affixed to the top of the stem. This new prosthetic ball articulates directly with the patient’s natural, unreplaced acetabulum. The prosthetic component can be unipolar (a single fixed ball) or bipolar (a smaller inner ball rotates within a larger outer head). Finally, the surgeon closes the incision with sutures or staples.
Recovery and Long-Term Considerations
Recovery begins almost immediately, with physical therapy starting as soon as the day of or the day after surgery. Patients are encouraged to get out of bed and begin walking short distances with the assistance of a walker or crutches to promote blood flow and prevent complications. The typical hospital stay is relatively short, often just one to three days, as patients are discharged once they can safely perform basic activities and manage their pain.
Full recovery can take between three and six months. A structured rehabilitation program is followed after discharge, focusing on strengthening the hip muscles and regaining range of motion. Long-term considerations for a partial hip replacement center on the interaction between the artificial ball and the natural socket. Since the socket is left intact, the prosthetic component can cause wear and tear on the natural cartilage over time, potentially leading to pain and deterioration. This may eventually necessitate a second operation to convert the partial replacement into a total hip replacement, though this risk is generally lower in older, less active patients for whom the procedure is intended.