The Oxford Partial Knee replacement is an excellent alternative to traditional Total Knee Replacement (TKR) in a select group of patients with arthritis primarily affecting one side of the knee joint. It has been used for more than 30 years and many high-level scientific studies have supported its use in these patients. It has the possibility to provide faster rehabilitation, improved function and equivalent pain relief as a TKR. It has the additional benefit of preserving bone stock for any future operations that might be required.
See news article - Benefits of Partial Knee Replacement.
The time to consider undergoing knee replacement surgery is when the pain in your knee is so severe that it is having a significant impact on your day to day activities. It is important that you have tried all reasonable non-surgical treatments, as some patients with severe arthritis on their x-rays can still cope quite well without surgery. It is not until your pain is fairly constant and severe that the potential benefits of surgery outweigh the risks and make it worthwhile going through the recovery period.
In the case of partial knee replacement there are some specific indications:
- Arthritis must be essentially isolated to one side of the knee joint.
- The arthritis must not be of the rheumatoid or inflammatory type.
- The knee must have an intact Anterior Cruciate Ligament (ACL).
You will be given a full briefing of how to prepare for your Oxford partial Knee Replacement well in advance of the day of surgery. In very general terms you will need to...
- Let our team know what other medication you are taking and follow our guidelines on taking these medications in the days/weeks before surgery.
- This is particularly pertinent to blood thinning medications such as aspirin, warfarin, clopidogrel and Xarelto.
- Let our team know if you develop symptoms of any illness (including a cold or fever) or if you believe you may be pregnant.
- If you smoke, stop smoking ideally several days or weeks ahead of the procedure, but at the very least not smoke after midnight the night before surgery.
- Maintain your strength and mobility as best as possible, some patients attend physiotherapy prior to the surgery in preparation.
- You will be seen in the hospital pre admission clinic and by the anaesthetist prior to surgery. They will give further details on the process and what to expect. Blood tests and an ECG test of the heart will be performed.
- Not eat or drink anything for a minimum of 8 hours prior to admission.
- Bring all available and relevant imaging with you to hospital.
The Oxford Partial knee replacement works by resurfacing one “compartment” of the knee (usually on the inner or “medial” side of the joint) with metal components fixed to the “knuckle” of the thigh bone (femur) and the top of the leg bone (tibia). Between these is placed a polyethylene spacer known as a “meniscal bearing” to replace the cartilage of the joint.
The operation typically takes 1 hour to complete. You will be given a general anaesthetic, (supplemented with a nerve block or local anaesthetic infiltration). A tourniquet is used to prevent bleeding and the leg placed in a special stirrup device to allow access. An incision of around 10cm is made just to the side of the patellar tendon and knee cap. The joint is prepared using a set of instruments specifically designed for use in this minimally invasive technique that allows the correct alignment, sizing and fitting of the metal components. These are press fitted to the bones to provide initial fixation. Each is coated on the back side with a coating called hydroxyapatite that encourages bone to grow onto and bond directly to the metal. The bonding process takes around 8 weeks to mature.
After fixing the metal parts, a “meniscal bearing” of the appropriate thickness is chosen to fit between the metals components. This bearing is not fixed to the metal, it is designed to glide with the normal motion of the knee, reducing wear and allowing more natural movement within the intact ligaments.
The incisions are closed with dissolving stitches and tissue glue. Dressings and bandages are applied.
After the procedure you will stay in hospital for about three to four days, depending on your progress in therapy. You will be encouraged to get out of bed and walk around a little from day one and your therapist will guide you through some light exercises.
You will use crutches or other gait aids for mobility and safety, these will usually be required for three to four weeks.
At the point at which you are able to walk, sit in a chair (and get out of one) you will generally be able to return home. Some patients may take longer to reach this point than others.
You will be given a full set of rehabilitation instructions and exercises to follow when you leave hospital. The dressings on your knee are to stay intact until review. If they leak or fall off, they should be changed with something similar from the chemist.
Many patients engage a physiotherapist to help regaining movement and mobility at this stage
You may drive once you can walk easily without gait aids. If it is the left leg and you have an automatic car this may be earlier.
Your first follow-up appointment will be scheduled for about 10 days after the surgery, the incision is checked and further instructions given. By about 4 weeks post op or less, you should be able to walk unaided. You will be seen again at 6 weeks with a check xray, and if all is well, then there is no need for further follow up until 1 year after the surgery.
All surgery carries with it some form of risk. Common risks that apply to all surgery, including partial knee replacement, are...
- Formation of a blood clot (“DVT” or deep vein thrombosis) Pieces of clot in the leg can break off and lodge in the lungs causing a pulmonary embolism. This can be very serious, and in rare cases even cause death.
- Infection - see notes on prosthetic joint infection.
- Nerve damage. It is common to have a small numb patch next to the incision.
- Difficulty getting the wound(s) to heal.
- Abnormal pain reactions or nerve hypersensitisation known as complex regional pain syndrome (CRPS).
Risks that are related specifically to an Oxford partial knee replacement include...
- Fracture of the bones during surgery.
- Problems with initial or secondary fixation of the metal components.
- Incomplete relief of pain – up to 10% of replaced knees have unexplained pain afterwards.
- Under sizing of the meniscal bearing, resulting in an unstable knee, residual deformity, clicking joint or complete dislocation of the bearing out from between the other components.
- Oversizing of the bearing resulting in pain or arthritis on the other side of the knee.
- Progression of arthritis in other areas of the knee.
- Stiffness or impaired range of movement.
- A stress reaction or even fracture of the tibia below the prosthesis- this may necessitate a prolonged period on crutches or even further surgery.
- Difficulty kneeling- less common than with TKR.
- Eventual wear or loosening of the prosthesis.