Unicondylar knee replacement and patellofemoral joint devices are designed to treat only one compartment of the knee. Both devices allow for conservation of healthy tissue and bone, but the devices are designed to treat only the specific compartment and not to work together.
Unicondylar knee arthroplasty of the medial compartment conserves bone and ligaments, which have been reported to result in a more normal gait, better quadriceps function, and better knee flexion than those treated with TKR. However, success of this treatment is highly dependent on the accurate assessment of possible arthritic involvement of the patellofemoral compartment. Undetected pathology and disease progression to the patellofemoral compartment has been correlated with late failure of the unicondylar knee arthroplasty.
In contrast, patients with involvement of only the patellofemoral compartment can be treated with a patellofemoral joint device, but again, proper patient selection is crucial because disease progression to medial or lateral tibiofemoral compartments resulting in recurrent joint pain is not uncommon.
The Total Knee Replacement, replaces the ends of the femur (thigh bone) and tibia (shin bone) with plastic inserted between them and usually the patella (knee cap)
If only a single compartment of the knee is worn out, then it may be possible to replace only the worn out component. This is usually done via a minimally invasive approach and the recovery time is much quicker. A 7 to 10cm skin incision is used and the kneecap is not reflected. The worn out surface is prepared. The femoral or tibial component is usually glued or press-fitted in place. The patient can be mobilised four to six hourly post-operatively and can go home after one to three days depending on the amount of pain experienced.
Other causes include : -
- Trauma (fracture)
- Increased stress e.g., overuse, overweight, etc.
- Connective tissue disorders
- Inactive lifestyle- e.g., Obesity, as additional weight puts extra force through your joints which can
- lead to arthritis over a period of time.
- Inflammation e.g., Rheumatoid arthritis
- The diagnosis of osteoarthritis is made on history, physical examination & X-rays
- There is no blood test to diagnose Osteoarthritis (wear & tear arthritis)
- Smaller operation
- Smaller incision
- Not as much bone removed
- Shorter hospital stay
- Shorter recovery period
- Blood transfusion rarely required
- Better movement in the knee
- Feels more like a normal knee
- Less need for physiotherapy
- Able to be more active than after a total knee replacement
Who is suitable and who is not?
- Ideally should be over 50 years of age.
- When pain and restricted mobility interferes with your lifestyle.
- One compartment involved clinically and confirmed on X-ray.
Who is not suitable?
- Patients with arthritis affecting more than one compartment
- Patients with severe angular deformity
- Patients with inflammatory arthritis eg. rheumatoid arthritis
- Patients with an unstable knee
- Patients who have had a previous osteotomy
- Patients who are involved in heavy work or contact sports
- Your surgeon will send you for routine blood tests and any other
- investigations required prior to your surgery
- You will asked to undertake a general medical check-up with a physician
- You should have any other medical, surgical or dental problems attended to prior to your surgery.
- Make arrangements around the house prior to surgery
- Cease aspirin or anti-inflammatory medications 10 days prior to surgery
- as they can cause bleeding.
- Cease any naturopathic or herbal medications 10 days before surgery
- Stop smoking as long as possible prior to surgery.
Day of your surgery
- You will be admitted to hospital usually on the day of your surgery.
- Further tests may be required on admission.
- You will meet the nurses and answer some questions for the hospital records.
- You will meet your anaesthetist, who will ask you a few questions.
- You will be given hospital clothes to change into and have a shower prior to surgery.
- The operation site will be shaved and cleaned.
- Approximately 30 mins prior to surgery, you will be transferred to the operating theatre.
Each knee is individual and knee replacements take this into account by having different sizes for you knee. If there is more than the usual amount of bone loss sometimes extra pieces of metal or bone are added.
Surgery is performed under sterile conditions in the operating theatre under spinal or general anaesthesia. You will be on you back and a tourniquet applied to your upper thigh to reduce blood loss. Surgery takes about two hours .
The Patient is positioned on the operating table and the leg prepped and draped.
A tourniquet is applied to the upper thigh and the leg is prepared for the surgery with a sterilising solution.
Risks and complications
As with any major surgery, there are potential risks involved. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages.
It is important that you are informed of these risks before the surgery takes place.
Complications can be medical (general) or local complications specific to the Knee.
Medical complications include those of the anaesthetic and your general well being. Almost any medical condition can occur so this list is not complete.
Complications include :
o Allergic reactions to medications
o Blood loss requiring transfusion with its low risk of disease transmission
o Heart attacks, strokes, kidney failure, pneumonia, bladder infections.
o Complications from nerve blocks such as infection or nerve damage.
o Serious medical problems can lead to ongoing health concerns, prolonged
hospitalization or rarely death.
Infection : - Infection can occur with any operation. In the hip this can be superficial or deep. Infection rates are approximately 1%, if it occurs it can be treated with antibiotics but may require further surgery. Very rarely your hip may need to be removed to eradicate infection.
Blood clots (Deep Venous Thrombosis : - These can form in the calf muscles and can travel to the lung (Pulmonary embolism). These can occasionally be serious and even life threatening. If you get calf pain or shortness of breath at any stage, you should notify your surgeon.
Fractures or breaks in the bone : - can occur during surgery or afterwards if you fall. To fix these, you may require surgery.
Stiffness in the knee : - Ideally your knee should bend beyond 100 degrees but on occasion the knee may not bend as well as expected. Sometimes manipulations are required, this means going to theatre and under anaesthetic the knee is bent for you.
Wear : - the plastic liner eventually wears out over time, usually 10 to 15 years and may need to be changed.
Wound irritation or breakdown : - The operation will always cut some skin nerves, so you will inevitably have some numbness around the wound. This does not affect the function of your joint. You can also get some aching around the scar. Vitamin E cream and massaging can help reduce this. Occasionally, you can get reactions to the sutures or a wound breakdown which may require antibiotics or rarely further surgery.
Cosmetic Appearance : - The knee may look different than it was because it is put into the correct alignment to allow proper function.
Leg length inequality : - This is also due to the fact that a corrected knee is more straight and is unavoidable. Dislocation An extremely rare condition where the ends of the knee joint loose contact with each other or the plastic insert can lose contact with the tibia (shinbone) or the femur (thigh bone).
Patella problems : - Patella (knee cap) can dislocate that is, it moves out of place and it can break or loosen.
Ligament injuries : - There are a number of ligaments surrounding the knee. These ligaments can be torn during surgery or break or stretch out any time afterwards. Surgery may be required to correct this problem.
Damage to nerves and Blood vessels : - Rarely these can be damaged at the time of surgery. If recognized they are repaired but a second operation may be required. Nerve damage can cause a loss of feeling or movement below the knee and can be permanent.
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