Total hip replacement is one of the most successful treatment interventions in current medical practice. In this operation, the ball and socket of the natural hip joint are replaced by a prosthetic joint.

 

The operation is most often needed for individuals who have Osteoarthritis of the hip. 

IArthritis of the hip  


The natural hip joint has a socket called the acetabulum, which is a part of the pelvic bone. The top end of the thigh bone, called the head of femur, is rounded and fits into the socket to form the hip joint. The articulating surface of the acetabulum and head of femur is lined with a very smooth covering called the articular cartilage.

 

In arthritis, the articular cartilage becomes thin and wears out. Various conditions can affect the integrity of the articular cartilage. Most commonly, it is osteoarthritis (also called as osteoarthrosis), and other conditions include rheumatoid arthritis, arthritis following injury to the hip, ankylosing spondylitis, arthritis secondary to malformation of the hip, gout, Paget’s disease, and rarely tumours and infections.

 

Hip replacement is carried out to relieve pain from the degenerate joint.

Image description

Primary or revision hip replacement 


The first time the natural hip joint is replaced, it is known as 'primary' hip replacement. If further operations are required to change one of both components, it is called 'revision' hip replacement.

 

In a primary hip replacement, the socket is prepared for insertion of an acetabular component, and the head of femur is removed and a femoral component inserted in its place. The two components are fixed into bone either with special bone cement, or by cementless fixation. In cementless fixation, the size and shape of the prosthesis accurately matches the prepared bone and the metal is coated with a special surface which encourages bone ingrowth into the metal, hence providing a firm fixation and long term stability.

Materials for hip joint - types of hip implants


Hip joint prostheses can be cemented or cementless. This is essentially the surgical technique used to fix the implants into the bone. In cemented implant, PMMA bone cement (Poly methyl meth acrylate) is used. In cementless fixation, the implant has a special coating on it, which allows the bone to bond directly with the implant. Both types have good survival and it is important to choose the right implant for the right patient as in some situations, once may work better than the other. 


The acetabular components in cemented sockets are made of ultra high molecular weight poly ethylene (UHMWPE). These are fixed to bone with Poly methyl meth acrylate (PMMA) bone cement.

 

Cementless sockets have a metal backing, like a hemispheric shell, which is fixed to bone. Within this shell, a (UHMWPE) plastic liner, or a metal liner, or a ceramic liner can be inserted. Cementless sockets allow multiple options for choice of liner. Similarly, the femoral component can be cemented into the thigh bone, or it can be cementless.

 

Cemented hip replacements have traditionally been used a lot in the past. Currently, cementless hip replacements are increasingly popular.

 

Metal on Metal Hip replacements


In metal-on-metal hip replacements, the socket and the ball is made of metal. This is not a good combination and a large percentage of these hip replacements have failed soon after implantation. This is an example of using untried and untested technology, with disastrous consequences. 


I have not used metal on metal hips in my patients. 


Image description
Image description

                     X ray showing arthritis of the right hip                                                            X ray after Right Total Hip Replacement

The operation  


Hip replacement surgery is done under general anaesthetic or epidural anaesthetic. Epidural anaesthetic is more commonly used, and it helps in postoperative pain relief as well.

 

The operation is done with patients lying on their side. The incision varies between 10cm to 15cm in length and the surgery takes 60 to 90 minutes. Usual hospital stay is between 2 and 5 days.

 

After surgery, mobilisation is started on the following day. Initially a Zimmer frame is used to help mobility and this quickly progresses to crutches and then sticks. By 4 to 6 weeks, most people are able to mobilise independantly without walking aids, and some may take up to 3 months to regain best mobility.

 

The physiotherapists will work closely after surgery to improve muscle strength and movements and with progression of exercises, the function in the replaced hip will improve. A list of exercises and precautions is provided, which enables individuals to achieve best possible outcome.

Care after surgery 


Following hip replacement, driving is not recommended for about 6 weeks. The insurance company should be informed about the hip replacement surgery.

 

Heavy work and lifting heavy objects is not recommended after hip replacement. Running and contact sport are also not recommended. Golf is possible, as is doubles tennis. Riding a bicycle is allowed after 2 to 3 months. Walking is not restricted after hip replacement.

 

Gardening is limited and many people may experience difficulty in kneeling down and / or sitting in a low seat. This is a permanent restriction.

 

If there was significant stiffness in the hip prior to surgery, it may be difficult to regain further movement after surgery. This means tying shoe laces and cutting toe nails may be difficult in these situations. There are specific methods which patients are taught postoperatively to manage activities of daily living, and these are part of routine rehabilitation.

 

These are broad guidelines and individual circumstances dictate rehabilitation for total hip replacement. 

Through meticulous technique and high standard of care, the outcome following hip surgery is better than ever before. 


I currently do over 200 hip and knee replacement operations annually. In my experience, Infection rate following hip replacement is zero, dislocation rate is less than 1 percent and the satisfaction rate after hip replacement surgery is 98%. The percentage of patients requiring redo operations is 1% at 4 years among all my patients with hip replacements. The high success rate and low revision risk compares extremely favourably to results in the National Joint Registry.  

These results are possible through meticulous technique, attention to detail and careful selection of implants.