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Knee prosthesis

Complaints that may be associated with a worn-out knee ('knee osteoarthritis') include

- Pain

- Swelling

- Impairment of function, inability to stretch fully or bend deeply

- Night pain

- Starting pain

- Morning stiffness

- Limited walking distance

Conservative path

When diagnosing osteoarthritis of the knee, a conservative course can always be started first, i.e. non-operative treatments are tried for at least a few months. These include painkillers, physiotherapy, weight loss and adjustment of the load on the knee.

Operative route

If the conservative course does not sufficiently alleviate the symptoms, surgical replacement of the knee joint can be considered: placing a metal plateau on the tibia and a metal cap around the thighbone (femur), with a plastic sliding surface (polyethylene) between them, the total knee replacement.

But how many symptoms must someone have before you decide to have a knee replacement? Unfortunately, there is no simple answer to this question. The conditions often applied are:

  • Osteoarthritis on X-ray, grade 3 or 4 according to the Kellgren-Lawrence classification
  • Night pain
  • Pain that cannot be adequately suppressed with painkillers
  • Pain-free walking distance of up to 500 metres
  • Difficulty putting on socks and shoes
  • Not too many risk factors in the patient, such as Body Mass Index (BMI) over 35, smoking, COPD, heart failure, diabetes.

Of course, these conditions are not rigid and will be discussed during the consultation.

The half knee replacement (unicompartmental)

If only one side of the knee is worn out, a partial replacement of the knee can also be chosen. The condition for this, however, is that the cruciate ligaments must be intact and that the unaffected side of the knee remains good during a 'stress test'. In other words, the thickness of the cartilage must be sufficient during a stress test.

The knee replacement

The prosthesis we use is the uncemented Triathlon knee prosthesis with a polyethylene insert. This prosthesis is made by the company Stryker and has proven itself amply worldwide. The expected life span of this prosthesis is about 20-30 years. This titanium prosthesis is provided with a hydroxyapatite layer so that it will fuse with the own bone. The advantage of this Triathlon knee prosthesis is a relatively small prosthesis, which means that in case of a recovery operation there is enough bone left to place a new prosthesis with stems in the bone.

Only in cases of poor bone quality as a result of osteoporosis can a "cemented" knee prosthesis be chosen, in which case it is glued to the bone. 

The operation - preparation

Before the operation, the anaesthetist will carry out a pre-operation examination. You will first complete an extensive online questionnaire about your health and medication. You will then discuss whether you would like spinal anaesthesia (epidural) with sedation or general anaesthesia. The first option is chosen in more than 90% of cases because of the faster recovery in the first hours after surgery. If you are taking anticoagulants ('blood thinners'), the anaesthetist will discuss with you whether you should temporarily stop taking them around the time of the operation.

The operation - in the holding area

On the day of surgery, you will be admitted to the holding area, the preparation room before you go to the operating theatre. There, you will receive an infusion and antibiotic prophylaxis will be started to minimise the risk of a wound infection.

The operation - in the operating theatre

First, a checklist is done with the whole operation team (Time Out Procedure). You will be connected to the anaesthesia machine to monitor all your vital functions during the operation. You will then be given spinal anaesthesia or general anaesthesia. The anaesthetist will remain at the head end of the operation to monitor you. The skin is disinfected and the operation area is covered with sterile drapes. You will also receive Tranexamic Acid to reduce the amount of blood lost during surgery.

The operation - the approach

The knee joint is approached from the front: the skin cut is about 15 cm long. Once the skin is open, the capsule along the inside of the kneecap is opened and the kneecap can be folded away. The knee joint is then clearly visible and the prosthesis can be inserted.

The operation - placement of prostheses

Saw blocks are used to determine the cuts and to precisely remove the (worn out) cartilage. The lateral knee ligaments are used to align the knee. The correct alignment of the kneecap is also examined. Once all cuts have been made, a test prosthesis is inserted. If we are satisfied, the definitive prosthesis can be placed, with or without glue (bone cement). The skin is closed with soluble sutures or a ZIP line suture. The wound is covered with a shower plaster. The scar is about 15 cm long. At the end of the operation, another checklist is taken with the entire team (Sign Out Procedure).

The operation takes about 60 minutes and the average blood loss is 150cc. A control X-ray is always taken after the operation.

The operation - in the recovery room

After the operation, you will be taken to the recovery room and your vital signs will be monitored extra, such as blood pressure, breathing, pain and blood loss. If you are stable, you may return to the ward.

In the post-operative department

Once the spinal anaesthesia or general anaesthesia has worn off, you can immediately start to put 100% weight on your body under the supervision of the physiotherapist. First with a walker, later with 2 crutches. You will quickly learn how to walk to the bathroom and toilet on your own. The next day you will learn to climb stairs. Once the pain is under control and the wound is dry, you may go home.

At home

The shower plaster can be left in place for 10-14 days, only to be replaced if it leaks through. Physiotherapy will help you to increase the load. Inside the house you will soon be able to walk with 1 crutch, outside with 1 crutch only after 4 weeks. You may drive a car only after you are able to walk outside comfortably with one crutch, usually after 5-6 weeks. You may only resume sports such as golf, swimming, dancing, tennis and outdoor cycling after 6 weeks.

Possible complications after knee replacement

  • Pain around the kneecap 5%.
  • Temporary numbness around the scar, probability 1.0
  • Wound infection, chance 0.5 %
  • Trombose, kans <0,5%

Pain around the kneecap

Some patients continue to suffer from kneecap problems when squatting, sitting on the knee, climbing stairs or exerting themselves heavily. In most cases, these symptoms disappear within the first year. If not, in some cases a decision can still be made to place a kneecap prosthesis.

Temporary dull spot around the scar

Traction during the operation or swelling after the operation can slightly damage a cutaneous nerve. Patients then have a temporary numbness around the scar of about 5-10 cm. In most cases, sensation returns completely within 4-6 months. 

Wound infection

You are always given antibiotics around the operation, but sometimes you may be unlucky if the wound does not heal properly and continues to leak. If the leakage continues for more than 2 weeks, the operation wound must be flushed in the operating theatre. This is to prevent the bacteria from settling on the prosthesis and becoming difficult to remove. After the flushing operation (also called DAIR: Debridement, Antibiotics and Implant Retention), you will be given an antibiotic for a minimum of 6 weeks, first for 1-2 weeks via infusion, then as tablets. In more than 90% of patients, this is how the infection is controlled.

Thrombosis prophylaxis

To reduce the risk of thrombosis, patients are given Heparin injections for 4 weeks, to be injected once a day into the abdominal fat or upper leg. You will be taught how to do this during your hospital stay.