Unipolar versus Bipolar Hemiarthroplasty in Hip Replacement: What You Need to Know

Hip fractures are a serious concern, especially among older adults. When someone breaks their hip, surgery is often necessary to relieve pain and restore mobility. One common surgical option is hemiarthroplasty, a procedure that replaces only part of the hip joint. In this article, we’ll explain what hemiarthroplasty is, the differences between unipolar and bipolar implants, what happens during and after surgery, and what recovery looks like.

What Is Hemiarthroplasty and Why Is It Used?

Hemiarthroplasty is a form of hip replacement in which only the ball at the top of the thigh bone (femoral head) is replaced. The socket in the pelvis (acetabulum) remains intact. This surgery is typically recommended for older patients, often those aged 80 or above, who have fractured their hip. Compared to a total hip replacement —which replaces both the ball and socket—hemiarthroplasty is less invasive, usually involves a shorter surgery, and allows for a quicker recovery.

Thanks to advances in implant design and materials, hemiarthroplasty is a dependable option. It helps relieve pain and restore movement, making it a good solution for patients who may not be able to undergo more extensive surgery. Research has shown positive outcomes, with most patients experiencing preserved joint function and pain relief.

Unipolar and Bipolar Implants: What’s the Difference?

The key distinction between unipolar and bipolar implants lies in how they interact with the body’s own joint structures.

• Unipolar implants have a single moving part: the new artificial ball replaces the femoral head and moves directly against the natural socket.
• Bipolar implants contain two moving parts. The artificial ball fits into an outer shell, which then moves against the socket. This design provides extra movement within the implant itself.

Why does this matter? The added mobility of a bipolar implant may reduce wear on the natural socket, potentially resulting in less pain and smoother motion over time. Some research supports this idea, suggesting that bipolar implants may distribute pressure more evenly and help maintain healthier joint cartilage for longer.

However, large studies have not shown major differences in complication rates between the two types—specifically, when it comes to dislocation and stability. For most patients, the choice of implant depends on factors like their age, bone health, daily activity level, and the nature of the fracture.

Surgery and Possible Complications

Deciding between a unipolar and bipolar implant isn’t just about the mechanics. Surgeons weigh many factors, including a patient’s age, overall health, bone quality, and the type of fracture.

As with any surgery, hemiarthroplasty carries certain risks. One potential complication is dislocation—when the artificial joint slips out of place. Research has found that the overall dislocation rate for hemiarthroplasty is about 3.4%. The risk is slightly higher with certain surgical approaches or techniques, such as a posterior approach or with cemented implants. To help prevent a dislocation, patients often follow specific movement precautions after surgery.

Other possible complications include fractures around the implant, infection, or, in rare cases, fat embolism (when fat enters the bloodstream during surgery). In some situations—such as ongoing pain or loosening of the joint—it may be necessary to convert a hemiarthroplasty to a total hip replacement later on.

Awareness of these risks helps patients and caregivers know what to watch for during recovery and gives them greater peace of mind.

Recovery: What Happens Week by Week?

Recovery after hemiarthroplasty usually begins soon after surgery. Most patients are encouraged to start moving and walking—with help—within a day or two, usually with the support of a physiotherapist. Early movement lowers the risk of blood clots and speeds up healing.

By about four weeks, many people can handle basic activities like walking short distances and getting dressed. Some evidence suggests that bipolar implants might allow for a slightly easier recovery because of the implant’s added mobility, but every patient’s journey is unique. It’s also worth noting that, while rare, bipolar implants can sometimes require further treatment if a dislocation occurs.

At 12 weeks, most patients enjoy improved mobility and strength. However, full recovery may take longer, particularly for those who have other health challenges. The NHS and other sources recommend gradually increasing activity levels and weight-bearing as tolerated, always guided by a healthcare professional.

Clear advice on what recovery should look like—week by week—can make a huge difference. It gives patients confidence and motivation to stick with their rehabilitation plan , helping them get back to everyday life as safely and quickly as possible.

Final Thoughts

Both unipolar and bipolar hemiarthroplasty implants play important roles in helping older adults recover from hip fractures. Unipolar implants are generally simpler and less expensive, while bipolar implants may offer added movement that can benefit some patients. The best choice depends on individual needs, including age, bone quality, and lifestyle.

No matter which implant is chosen, recovery is a gradual process that demands patience, support, and a good rehabilitation strategy. As technology and surgical techniques continue to improve, so do the outcomes for patients.

Understanding the basics of unipolar and bipolar hemiarthroplasty can help patients and their families make informed decisions and approach recovery with greater clarity and optimism.