Total knee replacement represents a considerable insult to the system when you consider -
- the patient requires an anaesthetic
- a skin incision (cut) is needed, with consequent bleeding
- the ends of the long bones will be cut off, with consequent bleeding
- the menisci will be removed and one or both cruciate ligaments may be sacrificed
- bone marrow will be exposed, and some could enter the blood stream
- bony spurs (osteophytes) may need removal along the edges, even after the main bone cuts are made
- tight soft tissues are likely to need to be released
- the metal and plastic knee implant needs to be the right size and chosen to allow optimal movement for the patient
- the cement that holds the metal components in place has to be pushed down into the raw bone ends and into the exposed marrow canal
- the patient may need blood transfusion or a fluid infusion
- there is the potential for the introduction of infection
- pain will be inevitable after surgery
At a 2014 meeting of knee surgeons and physiotherapists which I attended in Worcester in the UK, considerable attention was given to discussing the factors above, and what the surgeon and anaesthetist need to pay attention to at the time of the surgery itself. Dr Ranawat made a particular point that he feels that arthrifibrosis after knee replacement is a result of a combination of pain, improper soft tissue balancing, and local factors damaging the soft tissue and aggravating bleedng. By minimising the insult at this critical time there is a much reduced opportunity for complications, and patients will be able to proceed more confidently with their rehabilitation.
Inform and educate patients
Two of the guest speakers, Dr Chitranjan Ranawat and Dr Dennis Douglas, both leading knee surgeons from the USA agreed that it is vital that patients be informed and educated about the key issues and what to expect, and important to maintain contact.
Dr Ranawat went so far as to stress that the biggest cause of patient dissatisfaction after knee replacement is difficulty in communicating with the surgeon.
Use a pre-operative anti-bacterial regime
A routine of skin cleansing with antibacterial solutions may be instituted to ensure that the skin is not likely to be a source of early wound contamination.
There were differences of opinion amongst the various surgeons at this meeting as to how pain was to be managed before the actual surgery, but options included epidural anaesthesia, spinal anaesthesia, regional nerve blocks and infiltration of both the superficial and local tissues. These were in addition to a combination of pain-suppressing medications.
Adequately expose the surgical field
There is a conflict between the desire of the surgeon to leave the patient with the smallest scar possible, and the real need for adequate visualisation to enable the surgeon to do a good job. If an inexperienced surgeon does not adequately expose the affected areas, there is a danger that the bone cuts may not be perfect and the prosthesis may not be perfectly sized and positioned. Osteophytes may be inadequately visualised and removed, and the contracted soft tissues may not be adequately released. All of these can contribute to stiffness after surgery.
Pro-actively minimise bleeding
Before going through the steps these surgeons take to minimise bleeding, let me say a word about 'tourniquets'. Before major limb surgery, the surgical team classically lift the leg, squeeze the blood out of it with an elastic bandage applied from the toes to the thigh, and then inflate the cuff of the tourniquet with a pressure that is higher than the patient's blood pressure. This leaves the leg pale and unable to bleed and makes things really easy for the surgeon. BUT there is a risk that 'bleeders' will not be identified and sealed off by the surgeon, and they will then bleed once the tourniquet is down and the patient has been wheeled back to the ward, requiring the need for drains, which themselves may act as a portal for infection.
Tense and/or static blood in the wound is irritating and produces pain and inflammation. For all these reasons, very experienced surgeons like Drs Ranawat and Douglas advocate operating without the tourniquet being inflated (it is always applied in case of emergency bleeding), but inflating the tourniquet only during the cementing in of the prosthesis, because the uncured cement can cause catastrophic cardiovascular complications if it is released into the bloodstream.
Instead of relying on the tourniquet alone, they may use a variety of techniques to reduce the bleeding into the tissues, including -
By using an epidural anaesthetic instead of a general anaesthetic, the anaesthetist (anaesthesiologist) can 'titrate' the anaesthetic agent to produce both pain relief in the limb sufficient to allow the surgery and also to manipulate the blood pressure.
Hypotension (reduced blood pressure)
Further anaesthetic agents can be used to keep the blood pressure at a level low enough to be safe but to almost arrest bleeding into the wound. Before the wound is closed, the blood pressure can be increased and the surgeon can check for bleeders and seal them off.
Injecting the wound with local anaesthetic and adrenaline
By careful injection of the soft tissue around the wound edges, and the deeper tissues especially around the patella, the surgeon provides further pain relief. Mixing the local anaesthetic solution with a 'vasoconstrictor' that contracts the blood vessels (eg adrenaline) the bleeding is further minimised.
Focusing on good haemostasis (stopping 'bleeders')
By not using a tourniquet, the surgeon is able to identify bleeding vessels and cauterise (seal) them. Towards the end of the surgery, as the blood pressure is manipulated back towards normal, all bleeders should have been identified and the bleeding stopped.
Minimising the use of drains
Drains are uncomfortable, and may also act as an entry point for post-opertive infection, so any time with a drain inserted into the wound is kept to a minimum.
Minimise damage to the soft tissues
Stiffness after knee surgery is related to swelling, pain, irritation of the tissues from blood or infection. The less damage to the soft tissues the less the likelihood of swelling and adhesions. Tourniquet use will leave the tissues below the tourniquet without a blood flow for an hour or more, followed by a surge of blood flow - neither of which are good for the tissues. Careful surgical technique will also minimise damage to the soft tissues. The surgeon is careful in identifying blood vessels and nerves, and uses cutting guides to identify where to do the bone cuts.
Release tight posterior structures
Because the patient with arthritis may have been struggling with walking aids for some time, it is likely that their knee has been held in a bit of flexion, and the tissues at the back of the knee, such as the posterior capsule, may have contracted and become tight. These need to be released so that the patient can regain full extension after the surgery.
Remove osteophytes on the bone edges
After the bone cuts are made to fit the implant, there may still be bone spurs (osteophytes) lipping the cut edges. These would have developed as part of the arthritic process, but they may interfere with the soft tissues during knee movement and cause tissue irritation and pain. Careful removal of the osteophytes should obviate this.
Balance soft tissues and the 'gap'
Because the joint would likely have been at a bad angle for some time as the arthritis progressed to the point of needing a knee replacement, some of the tissues at the sides and the back of the knee may either be stretched or contracted. Once the osteophytes are removed and the implanted cemented into place and all excess cement material carefully removed, the surgeon will check the knee movement and also the gap between femur and tibia - there should be no tilt to one or other side.
To get this right the surgeon may need to stretch some tissues (for example 'pie crusting' - making small stabs into the tight lateral structures to gradually stretch them out) and some tissues may need to be tightened.
Re-surface the patella?
This point was a bit controversial at this meeting, with the USA surgeons advocating trimming off of the joint surface at the back of the patella and replacing it, too, with an implant of metal and plastic. The UK surgeons in general did not think that this was necessary.
Use Continuous passive motion (CPM)
Immediately after surgery, the use of the CPM (continuous passive motion) machine ensures that the knee is moved gently and regularly through a set range of motion, mobilising any residual blood and keeping the soft tissues supple.
Clearly, the process of mobilisation will continue into the rehabilitation period, but this paper does not go into that - we are just considering the steps that the surgeon can take to reduce the likelihood of the knee going on to become stiff after the surgery is over.
Dr Sheila Strover
Terminology of flexion and extension