KNEE REPLACEMENT SURGERY is performed as an average of 90,000 times per year in the U.K.

 

I perform approximately 100-150 knee replacements per year, which is above the national average per surgeon.

 

Knee replacement surgery involves replacing the arthritic knee joint surface with an artificial bearing. This is also known as a prosthetic joint.

 

The round ends of the femur or thigh bone at the knee, known as the femoral condyles, are machined and an artificial conforming spherical metal prosthetic bearing is then fixed into its surface. 

 

The tibia or shin bone at the knee joint is also machined and resurfaced with a metal tray with a keel that is fixed into the bone.

 

Finally, a plastic piece is attached to the tibial metal tray that conforms with the spherical metal prosthetic bearing of the femur. This recreates a new artificial knee joint.

 

The new knee joint implants are held in place into the bone by a special surgical cement used to glue them in position. This is very similar to that used in dental surgery to fix metal fillings in place.

 

There are numerous knee replacements produced by a variety of manufacturers. There are more than 25 brands that have more than 1,000 cases registered in the National Joint Registry in the UK. To complicate matters, there are two big knee implant design philosophies and many different evolving ideas about the techniques to machine and position the implants inside the knee joint.

 

I only use prosthetic components with a proven track record. The knee prostheses I use in most cases are of the Medial Pivot Knee design, either the MicroPort Evolution Medial Pivot knee implant or the MatOrtho SAIPH knee implant. I have both, visited the design centres for these prostheses and I learnt the specific surgical techniques for their insertion.

 

I have also trained in performing Robotic Assisted Surgery. The ROSA Robot helps with the accuracy in the technique of machining and positioning the implants. For these cases, I use a design closest to the medial pivot designs, the Zimmer-Biomet Persona MC knee implant. 

 

Procedure for Knee Replacement Surgery

 

Once it is decided you need a knee replacement, prior to the actual surgery there are a number of things that take place to ensure that the operation proceeds as smoothly as possible and that you are well prepared following discharge from hospital back home with your knee replacement.

 

Pre-operative assessment

 

Prior to the surgery you will attend a preoperative assessment clinic. This is to ensure you are fit enough to undergo the surgery. You will be asked questions regarding your general health and current medications that you take by a specialist nurse and/or anaesthetist. 

 

Following this your blood pressure will be checked and your heart and chest will be examined.  

 

A blood sample will be taken as well as a urine specimen. A special examination of the heart known as an ECG will also be performed. Additionally a chest X-ray may be performed.

 

You might also be seen by a physiotherapist and an occupational therapist. This is an ideal opportunity to ask questions about any concerns that you may have about getting around at home following your discharge home. Such concerns commonly include asking about rearranging your furniture to enable you to get about your house more easily after the surgery, removing any rugs/mats that could pose a risk to you slipping/falling, discussing the existence and nature of stairs and moving everyday items so that they are within easy reach. 

 

The occupational therapist may arrange for specialist equipment to be available to help you at home following discharge. This may include installation of such items as stair rails or shower chairs and the provision of assistant devices such as a long handled shoe horns or long handled grabbing tools. 

 

Day of surgery

 

You might be provided with a carbohydrate drink to take the evening before and six hours before your planned surgery. Otherwise, please drink two pints of water with cordial the evening before and two pints of water as soon as you get up in the morning of your surgery. 

 

You are usually admitted on the day of your operation.  The anaesthetist and I will see you prior to your operation and answer any last minute questions/concerns you may have. Prior to going to the operating theatre you will receive Gabapentin and Oxycontin (pain relieving medication).

 

The anaesthetic I prefer to use for your surgery is that of spinal regional anaesthesia. This has been shown to reduce the amount of blood loss during surgery and possibly reduce the complications from blood clots following your surgery. It also avoids the insertion of a tube into your throat which is required with a general anaesthetic. This can give you a sore throat for a few days following surgery. Nausea, drowsiness and headaches which are common problems with general anaesthesia are also avoided. It also maintains your cognitive function better and this is important with advancing age.

 

The spinal anaesthesia involves injecting a small amount of anaesthetic into the fluid surrounding the spinal cord in the lower back. This induces a short acting loss of sensation (numbness) in your lower limbs which allows the operation to take place pain free. The feeling returns to your legs after a few hours, after the operation has been completed.

This process is undertaken in the anaesthetic room and then you are then moved to the operating room next door. Sedative medication is also administered at this time if needed.

 

The anaesthetic will be discussed preoperatively with your anaesthetist. If there are any contraindications to undergoing a spinal anaesthetic then you will be offered a general anaesthetic.

 

Antibiotics to reduce the risk of infection and a drug to reduce post-operative bleeding (Tranexamic acid) are given prior to surgery starting.

 

The surgery itself is undertaken in a specially designed operating theatre to reduce the risk of infection. This is known as a laminar air flow theatre.

 

You will be placed on your back on the operating table and your leg will be held with specially designed supports. The skin over your knee is then shaved if necessary and disinfected prior to surgery, again to reduce the risk of infection.

 

At the end of the operation local anaesthetic is injected into the tissues around the knee joint, to reduce post-operative pain.

 

A non-complex knee replacement is usually performed in 1-1 ½ hours. You will spend some time in the theatre recovery room prior to being transferred back to the ward. The whole process of leaving and returning to your ward usually is about three hours.

 

Post-operative care

 

Usually the same day of your operation you will start your rehabilitation by getting up out of bed and walking with the help of the physiotherapist. 

 

Following the knee replacement you are able to put all of your weight through your new knee. Initially you may need the use of a special walking frame (a zimmer frame) but should quickly progress to using walking sticks.

 

Blood tests will be taken following your surgery and you will have an X-ray taken of your new knee replacement.

 

Blood thinning tablets will be given whilst you are in hospital to reduce the risk of you developing a blood clot in your veins. When you are discharged you will continue taking those tablets daily up to 14 days following your surgery to continue minimising your risk of developing a blood clot. You may also be provided with some special stockings to wear which are also designed to reduce this risk. 

 

Analgesic medication is provided to reduce the postoperative discomfort and ensure you are able to undertake the required physical therapy to ensure a rapid return to normal mobility.

 

The majority of my patients are discharged within two days of their surgery. It is usual to be discharged when you can safely walk with two walking crutches including going up and down a flight of stairs. 

 

What can I expect after my Knee Replacement?

Once at home following discharge from hospital you should keep your wound dry until your stitches/skin clips have been removed. These will usually be removed about fourteen days following your surgery. You must do your knee movement exercises daily. 

 

If any redness develops around your scar, or it continues to leak fluid, you should either consult your GP or your surgeon for advice.

 

Following your knee replacement, you should expect a slow and steady return to your lifestyle and activities but without the pain and aching that you experienced prior to the knee replacement. The pain in the knee wound should be bearable but it will increase during your exercises and you will feel wounded and at times even sorry for yourself. It is all normal. The first four weeks are the most difficult because you must do the knee exercises. For some, knee replacements are a very painful experience to rehabilitate from and can take a good part of the whole year to forget that their knee had surgery. Specific concerns commonly include the following:

 

When can I sleep on my side/stomach?

I usually advise you to sleep on your most comfortable position as long as achieving and remaining in that position it does not hurt or pull unduly in your surgical wound. Slow movements without forcing your body are the key. 

 

When can I get in a car and when can I drive?

Following your knee replacement you can sit in a car when you are discharged from hospital. I recommend however that you avoid travelling in cars for at least three weeks following your surgery to diminish the risk of deep vein thrombosis.  I also advocate avoiding driving until three weeks after your surgery. You need to ensure that you can perform an emergency stop and hold your foot on the brake (and clutch) for at least 10 seconds. It is also important to ensure that the wound has sealed and healed prior to attempting to drive.

 

When can I resume sporting activities, dancing or gardening?

This depends upon the sporting activity in question. Swimming can be resumed once the wound is healed, as can activities such as walking, golf and dancing.

 

Gardening activities can be resumed once the wound has healed. You should avoid kneeling until the wound has healed, but after that, there are no restrictions. 

 

Activities that involve impact stresses on the joint such as jumping, jogging and contact sports should be avoided in general following your knee replacement.

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What are the risks?

Knee replacement surgery is a major operation. Complications, albeit rare, can occur. You should be aware of these risks prior to consenting for your operation. The statistics quoted are national figures.

 

General complications related to surgery

Deep vein thrombosis (about 3%): This is a blood clot in the deep veins of the legs, and/or thighs.  Rarely, part of this blood clot can dislodge and travel to and become lodged in the lungs causing a pulmonary embolism (less than 1%). This will cause breathlessness and chest pain. This is a serious and potentially fatal condition in 0.004% of cases.

The theatre team and I try and reduce this risk by using special equipment during your operation to regularly and intermittently gently squeeze the calf muscles of your other leg. This is known as a flowtron gaiter. Post operatively you will receive blood thinning medication and be given TED stockings to wear.

 

Urinary retention:  Occasionally you will have problems urinating after surgery. This may necessitate insertion of a temporary urinary catheter, which is usually removed when you are up and fully mobile. 

 

Nausea, loss of appetite and constipation: These are common after surgery. They usually resolve after two or three days. Stool softeners may be prescribed if you develop constipation.

 

Cardiorespiratory complications: such as a heart attack, stroke or chest infection (less than 1%). Prior to your surgery your fitness to undertake the knee surgery will be assessed to try and reduce these risks.

 

Complications due to knee surgery

Deep Infection (1%): Following your operation occasionally the wound can leak some fluid. This usually settles after a few days. A superficial infection can occur which usually responds to oral antibiotics. Infection however can sometimes occur deep in the knee joint itself around your new knee prosthesis. This may occur at any time after your operation and sometimes many months or years after your operation. If this deep infection does not respond to antibiotics there is a risk that you will need to undergo a further operation to replace this infected knee as your body will tend to reject the prosthesis.

 

Knee Stiffness: (1%). It is important that knee physiotherapy exercises are performed post-operatively specially in the first six weeks to avoid this disabling complication. 

 

Nerve injury and vessel injury:  This is very rare (less than 0.1% or 1 in 1000). It may result in foot weakness (foot drop) necessitating the use of a special splint or loss of blood supply to the foot requiring vascular by-pass surgery. Rarely (0.05%) an amputation could occur. 

Numbness in a patch of skin lateral to the wound is expected and it will persist. That is why at times perform a laterally curved incision for knee replacements. 

 

Ankle swelling: This is very common and usually takes several months to resolve. 

 

Thank you.                              

                                                   MR KOLDO AZURZA, LMS FEBOT FRCSTr&Orth