KNEE REPLACEMENT SURGERY
I must stress that this surgery, as for any joint replacement, is elective surgery and is dependent on the level of pain and disability experienced by you the patient. I do not treat X-rays (with the odd exception) I treat people. How bad the X-ray looks does not correlate with how much pain one is going to feel. The Xrays or MRI or CT scans are only images used to confirm a diagnosis, in this case mostly Osteoarthritis. There are many causes for knee pain that can result in the need for a knee replacement, but they all boil down to destruction of the cartilage of the knee joint which leads to pain that requires eventual replacement with an artificial knee.
A knee replacement is an artificial joint made out of metal and polyethylene plastic. As such it will never be as good as the knee you were born with and you should not believe everything the implant marketing companies tell or promise you regarding their products. Evidence based medicine has consistently failed to show any superiority of one implant over the other. The important aspect of the surgery is how well the implant is put in with respect to the alignment and the sizing. This can be assisted by either preoperative computer guided templating or intraoperative computer navigation. Both these techniques come at extra cost and although I offer them to my patients, I do not do so as a routine simply because again evidence based medicine has failed to show that they improve outcomes yet.
Intuitively these new techniques should improve outcomes, and it may be the case that we just don’t have enough long term data.
What is done at surgery?
- Once asleep with anaesthesia, a tourniquet is applied to the thigh and sealed off before skin cleansing and draping.
- First the skin is cut in front in the midline ( approx. 15cm centered on the kneecap)
- The tendon connecting the quadriceps to the shin bone is split on one side of the knee cap and the knee cap retracted to the side.
- The damaged joint surfaces of the end of the thigh bone and shin bone that make up the knee are exposed.
- All the while, care is taken to protect the side (collateral) ligaments and the nerves and blood vessels behind the knee.
- All bony overgrowths (osteophytes) are removed
- All scar tissue and contractures are released to free up the knee.
- Using various guides, computer assisted or otherwise, the ends of the bones are cut, shaped and sized.
- The bone surfaces are cleaned, any cysts are bone grafted and generally prepared for bone cementing ( a type of grout ) and metal implant fixation.
- The metal components are impacted onto the bone for a solid fit.
- The polyethelene insert is snapped into place and the knee is closed up in layers using various stitch materials.
- Dressings are applied and the tourniquet released.
Often both knees may be involved to the same degree, but evidence has shown that the risks of performing bilateral knee replacements at the same time are very high and I do not do this with rare exceptions. The second knee can be done 6 to 12 weeks after the first.
Possible complications after a knee replacement occur in 1 to 2 percent of patients and this figure is increased if the patient is overweight, diabetic, has scarring or deformity around the knee, a stiff knee, poor circulation or poor immune status.
- Stiffness with poor range of motion
- Deep vein thrombosis and risk of Pulmonary Embolism
- Nerve and Blood vessel injury
- Wound breakdown
- Implant loosening
- Persistent pain
Many of these complications may require reoperation.
- Pain relief in > 95% of cases
- 10 year survival in over 65 year olds of > 95%
- Good range of movement i.e full extension and > 100degrees flexion in > 95% of cases
What can you do with a knee replacement?
- Go for long walks
- Gentle dancing
- Doubles tennis
Obviously the more you hammer your knee the less it will survive as the artificial surfaces will wear away and the implant will loosen.
When are you ready for a knee replacement?
- When you have persistent pain and rest especially if you are unable to sleep.
- Difficulty walking on flat ground for longer than 15 to 20 minutes without needing to stop, or being unable to walk without an aid like a walking stick or crutch.
- Unable to manage stairs without using the banister.
- Unable to get out of a chair without pushing yourself up using the armrests.
- Severe deformity.
Conclusion: A knee replacement is an excellent operation if done for the right reasons. The results will always be best if one maintains flexibility by regular stretching and cardiovascular (heart and circulatory) fitness by watching what you eat and doing regular low impact exercise.