Total Hip Replacement (THR)

The hip is a ball and socket joint. The articular cartilage within the joint withstands huge forces over a lifetime. If the cartilage starts to wear out, the underlying bone of the ball comes into contact with bone in the socket – this leads to pain and stiffness.

Symptoms

Groin pain (may radiate to the knee)
Pain worse on activities such as climbing stairs, getting in and out of cars, walking, putting on shoes and socks
Night pain
Stiffness
Leg shortening

Normal hip x-ray showing a clear gap between the bone of the ball and socket (intact cartilage)

 

X-ray of advanced arthritis of the hip – note no joint space and bony contact

About THR

Total hip replacement replaces the damaged joint surfaces which relieves pain and improves mobility and function.

In terms of improving your quality of life, THR is ranked in the top 5 of all medical and surgical procedures to date.

                                                                                

Picture showing the parts of a THR and how it fits into the body                                                       Post operative x-ray

Bearing surfaces

There has been a lot written in the press recently about metal-on-metal THR’s. I do not perform this bearing surface combination.

My standard bearing coupling is metal (cobalt chrome) on plastic (highly cross linked polyethylene). This combination has the longest follow-up of all and has stood the test of time.

More recently I have started using Verilast TM – ceramic metal (oxinium) on plastic (highly cross linked polyethylene).

For young, active patients I use delta ceramic on ceramic. This material is stronger than metal and causes the least wear particle generation.

My standard head size (ball) is 32 or 36 mm. This has been shown to increase the range of motion and decrease dislocation rate compared to 28mm head.

The operation

The stem of a hip replacement can be cemented or uncemented, depending on your bone quality.

The procedure takes 60-90 minutes.

You are able to fully weight bear on your new hip straight away.

Hospital stay is usually about 3 days.

After 6 weeks you will be able to resume usual activities like driving and walking without a stick.

Complications

Complications are rare.

During the operation

Damage to nerves and blood vessels

The incision damages some skin nerves and you will have a patch of numbness over the outer part of the kneecap. Everyone who’s had a TKR has this. The main nerves and vessels to the foot are tucked away at the back of the knee. In some severely deformed knees, the nerve to foot can sometimes be stretched – again -  don’t leave it too long.

Fracture

If the bone quality is very poor, fractures can occur. This is extremely rare and will be dealt with during the operation.

After the operation (0 – 12 weeks)

Blood clots

Clots in the calf veins (DVT) can form after TKR. To prevent this we give you special stockings to wear and medication which thins the blood slightly to prevent clots from forming. The best way to prevent clots is by walking on your new knee as soon as possible. If a DVT forms, some of it can break off and travel in the bloodstream to the lungs. This is a pulmonary embolus (PE) and is very rarely fatal (less than 1 in 1000). The stockings should be worn for 6 weeks. The daily injection under the skin (as an inpatient) and tablets (as an outpatient) are to be taken for 5 weeks after the operation

Infection

The rate of wound infection is about 1 in 100 (1%). This can be treated with antibiotics. Deep infection of the joint is much less common (0.1%).

Stiffness

The first few weeks after a TKR are painful but its important to push on and persevere with your exercises.  Not doing so is a cause of long term stiffness and decreased range of movement.

Dislocation (acute)

When this occurs, the ball of the THR comes out of the socket. It happens in 1-3% of THR’s. This will be painful and you will not be able to walk. This usually requires a general anaesthetic to reduce the ball back into the socket. It can happen if you trip or fall after the operation of if you twist and bend the hip excessively. It is important to listen very carefully to the physios who will tell you the movements to avoid to prevent dislocation.

Heart attack / stroke

If you do not suffer with these conditions, it is extremely unlikely that this will occur. If you do, then you will need to see the anaesthetist at pre-assessment clinic. I may refer you to the cardiologist or stroke unit before the operation.

After the operation (12 weeks onwards)

Leg length discrepancy (LLD)

The bone taken away at the time of surgery is accurately replaced with metal and plastic (to the mm). If both knees are affected with arthritis, it is possible for the operated knee to feel longer. In general we can tolerate up to 1cm of LLD.

Loosening

After about 20yrs, the cement that is used to hold the implants in place can start to crumble causing the implants to loosen. This presents as pain and instability of the knee. Revision surgery is usually required in these cases.

Dislocation (chronic)

If this occurs years after your first operation, it usually means that either the socket or the stem has shifted position or that the plastic liner inside the socket has worn away. Either way it is likely that revision hip surgery will be required.