What is the Hip?
Many patients think that their hip joint is on their side, but that’s not actually true. The femur has a bony bump on the outside called the greater trochanter, which is what you can feel on the outside of your hip, but it’s not actually part of the joint.
The ball and socket of your hip joint is actually located beneath your groin. This is why hip pain is commonly felt in the groin or buttocks, or even down your thigh and into your knee joint.
How Does the Hip Work?
Your hip is a simple ball and socket joint. The socket of the joint is called the acetabulum. The top of your thigh bone, or femur, has a ball on top of it that fits perfectly inside the socket.
Both surfaces of the ball and socket are covered in a smooth substance called articular cartilage. You may have seen cartilage stuck to the end of a bone such as a chicken wing. It’s exactly the same substance that’s in your joints.
This smooth articular cartilage allows your hip to glide around and move without pain. A normal hip joint lets you move your leg in pretty much any direction; forwards, backwards and also from side to side, which are essential movements for everyday activities; doing the shopping, riding a bike, getting into and out of a car, and even putting on shoes and socks all require your hip joint to move freely.
What Happens During a Hip Replacement?
Put simply, it involves giving you a new ball and a new socket.
The first thing we do is remove the old ball of the hip joint. This requires a surgeon to make a cut through the bone with a small saw. We remove the ball, and also a few millimetres of what we call the neck of the hip joint.
We then place a prosthesis down, inside the hollow thigh bone, and it fits firmly in place. This prosthesis is made of metal, and the outside is very rough and grippy, so it attaches securely inside the bone. Your bone also grows into this rough surface and heals the prosthesis securely in place. In some patients we may choose to use a special bone cement to achieve this.
On top of this prosthesis we place a round, smooth ball. This becomes the new ball of your hip joint. This particular ball is made of a material called ceramic, but they may also be made of shiny metal.
The socket, or acetabulum, of your hip joint is located within your pelvis. We place a new, prosthetic socket into the arthritic acetabulum of your pelvis. This is made of metal, and it heals into your own bone in just the same way as the thigh bone prosthesis does.
The inside of the socket has a very smooth lining, made of medical-grade plastic, but it can also be made of ceramic. Technically this plastic is called ‘high molecular weight polyethyelene’ but you can think of it as acting just like the Teflon in your non-stick frypan. This acts like artificial cartilage, and the round, smooth ball of the femoral prosthesis matches the shape of this perfectly. The ball can now glide around smoothly inside the socket, with minimal friction.
So unlike before, when your arthritic hip was bone grinding on bone, there are now two new surfaces gliding over each other. This is what takes away your pain and improves the range of motion of your hip joint.
When we look at an x-ray after hip replacement, you can see the new socket, the new ball, and the prosthesis inside the thigh bone. Of course, what we can’t see is all the muscles, tendons and ligaments around the hip joint, because they are invisible on an x-ray.
Because we are actually replacing the bone and cartilage that has worn away from arthritis, a hip replacement is also able to lengthen your shortened leg, and put it back to the same length it was before arthritis shortened it.
Hip Replacement Surgery Procedures
Some of my patients are confused about how their hip joint should be replaced. There is a lot of information available about hip replacement surgery, with varying opinions about what is best.
There are 3 main surgical techniques that a surgeon can use to replace your hip joint. You can think of each of these 3 approaches as being a different door to your hip joint. Each door leads to the same place, just through a different path.
The Posterior Approach
As the name suggests, this approach replaces your hip through your bottom muscles. A surgeon separates the largest muscle in your body, called the gluteus maximus, that is just under the skin of your buttocks. The surgeon then detaches some tendons around the bone of your hip, to expose and replace the joint. At the end of the operation these tendons are repaired back to bone with suture. The gluteus maximus muscle is also repaired back together with sutures.
Personally, I use the posterior approach in only a small number of specific patients. However, many surgeons do use this approach for all their patients, and the outcomes are very good.
The Lateral Approach
The lateral approach involves detaching part of a tendon, called the gluteus medius tendon, from the thigh bone. Gluteus medius is one of the most important muscles and tendons around your hip joint. Once the hip is replaced, the gluteus medius tendon is repaired back to the bone with suture material.
The direct anterior approach, which is the technique I prefer to use for the vast majority of my patients, takes place through the front of your hip joint. The size of your incision depends a little bit on the size of a patient, but in general it is quite small, about 6-10cm in length.
Rather than splitting muscles or cutting tendons, we move in between the muscles on the front of the hip, to gain access and replace the joint. At the end of the procedure no muscles or tendons require repairing with suture, because they have not been cut during the operation.
The principle of the anterior approach is to allow patients to mobilise more quickly, with less pain and weakness early after the operation.
Which Hip Surgery Procedure Should I Use?
Each surgeon has a particular preference, and skill set, for the type of procedure they use to replace a hip joint. This is influenced by where in the world they completed their training, what surgical techniques they’ve been exposed to, and also the evidence around what works best for patients. Every hip replacement technique has pros and cons, so talk to your surgeon about why they prefer the particular technique they use.
I’m passionate about the anterior approach for my patients, because it avoids cutting muscles and tendons. Temporary weakness is created when a muscle or tendon is cut, until they heal and recover. In some patients there can be residual weakness, even after full healing has occurred.
However, it’s very important for me to highlight that no matter what technique a surgeon uses, a hip replacement is an excellent operation with very high levels of patient satisfaction and function. In fact, a number of studies have shown that no other operation improves a patient’s quality of life as much as a hip replacement. It’s been an incredibly successful procedure for many years.
Rehabilitation After Your Hip Replacement Surgery
Rehabilitation begins from the day of your surgery. You are allowed to stand up and walk on your new hip as soon as your pain control and strength allows you to. Most patients will aim to sit out of bed and stand on their new hip the same day as surgery. A physiotherapist will work with you every day in hospital to get you up and moving, and also to provide a basic game plan for your rehabilitation in the weeks after you leave hospital.
Most patients will spend 3-5 nights in hospital after a hip replacement. After this, the safest place for patients to recover is in their own home. However, if you have specific health needs, or just require a little bit more support, you have the option of an extended period of rehabilitation within a hospital.
The use of a cane, or a walking frame for more elderly patients, will typically be required for the first few days after surgery. Most patients are then able to discharge from hospital using a walking stick or less, however, occasionally a walking frame may be required.
After anterior hip replacement surgery, most patients are in less pain overall when they leave hospital than they were prior to surgery. There will be some pain and swelling from the operation, but the severe groin pain goes away very rapidly. Patients will notice more freedom of movement in their hip quite quickly.
Recovery Timeline After Hip Replacement Surgery
Many patients describe a ‘woody’ or bruised feeling in their thigh for the first 2-4 weeks after surgery. It can feel tight, swollen and a little bit like having a ‘corky’ from a bad knock playing sport. This is very normal. Even though no muscles have been cut, you’ve still had a significant operation which involved removing the ball of your hip. There will be some on-going bleeding and swelling within your hip for several days. When you stand up, gravity allows this swelling to drain into your thigh and it feels swollen. Your body will absorb this over the next few weeks.
You will also require regular, simple medication, such as Panadol and anti-inflammatories for a minimum of 2 weeks, and possibly longer. If you still have pain despite these simple medications, you will have a supply of stronger pain medication to take if and when required. We call this ‘break through’ pain relief. If your pain ‘breaks through’ your regular pain medication, you have a safety net of stronger medication ready to go.
The best thing you can do for the first 6 weeks after surgery is be sensible, and gently increase your activity levels as you feel comfortable. It takes 6 weeks for the prostheses to heal into your bones, so there is no running, jumping or high-risk activities during this time. However, the movement restrictions that may apply for the first 6-8 weeks with other hip replacement techniques are not needed after anterior hip replacement surgery.
2-4 Week Post-Surgery
Patients in light or office-based occupational roles may be able to return to work. With your physiotherapist’s monitoring, good strength, controlled pain and no restriction of movement, driving a car may be viable.
6-8 Weeks Post-Surgery
The majority of patients are walking normally and not using a walking stick. Patients in manual labour roles may be able to return to work, depending on occupation. It is unusual for patients to be taking any pain medication at this time.
3 Months Post-Surgery
The majority of patients will be over 80% recovered, and back into all usual activities.
Up to 12 Months Post-Surgery
The final 20% of your recovery occurs slowly but gradually, and most of the ‘little niggles’ slowly fade away.
Running is not recommended after having a hip replacement, as this will make the new hip wear out more quickly. But you can walk, swim, hike, ride a bike, go to the gym and pretty much build back into most of the activities you enjoy. For example, playing golf and a social hit of tennis is possible for most patients.
How Long Will My Hip Replacement Last?
The basic rule of thumb is that a hip replacement will last most patients 20 years or more. To put this into context, if you looked at every patient in Australia who had a hip replacement 18 years ago, over 90% have not required replacing.
If and when your hip does wear out, it can be replaced with a new one, but that surgery is more complex, and the functional results may not be as good as the original procedure.
Risks of Hip Replacement Surgery
Like all operations, there are some risks that every patient needs to be aware of and understand. Serious complications are rare, but some minor complications are common.
These complications are common among patients:
- Mild, ongoing bleeding and oozing inside the hip.
- Numbness of the thigh for up to 6 months.
The following complications are rare, but possible.
- Injury to a major blood vessel.
- Damage to a major nerve.
- Joint infection.
- Ongoing numbness of the thigh.
- Blood clot in the calf.
- Lengthened or shortened legs.
Do I Need Hip Replacement Surgery?
You do not need to be a certain age to have a hip replacement, however, it is worth keeping in mind that hip replacements don’t last as long in younger patients as they do in more elderly patients simply because younger people tend to be more active. You also do not have to get a hip replacement simply because an x-ray or MRI scan shows you have arthritis. Many patients have arthritis, but their symptoms are mild.
The decision about when is the right time for a hip replacement is a complex and personal one. However, I would strongly encourage you to make a decision based largely on your level of pain and loss of function. Or put simply, how badly is your hip affecting your quality of life?
There is no rush to have a hip replacement. Getting a broad range of opinions from health care professionals is also helpful; your General Practitioner and physiotherapist are people you know and trust, and they know you and your health history. In my experience, most patients have told me that they eventually reached a point where they just knew it was the right time for them to have a hip replacement.
What to Do Before Your Hip Replacement Consultation
Before your consultation appointment, jot down any remaining questions you have so that you can discuss them with your surgeon. The more you know and understand about hip replacement before you even see a surgeon, the more you will take out of your consultation with them. I’m sure everyone can all relate to walking out of a doctor’s office and thinking, “I knew there was something else I wanted to ask, and now I’ve just remembered it”. If you write down the key questions you want answers to before you see your surgeon, this won’t happen.