When performing Total Knee Replacement it is important to have the implants well aligned. This enables the weight bearing axis to fall evenly through the implant, and thus ensure its longevity.
In much the same way as poor wheel alignment in your car causes uneven tyre wear, if your knee replacement is poorly aligned it can result in early failure and an uncomfortable or unstable knee.
Computer Navigation allows the surgeon to use a computer and associated graphical representation on a monitor to more closely and reproducibly align the components well. The surgeon can also record this data so that proof of alignment is seen.
Computer navigation is especially useful in cases where past surgery or injury has distorted anatomy, making conventional techniques difficult or impossible.
Patello-femoral Osteoarthritis: What are the options?
Isolated osteoarthritis of the Patello-Femoral Joint (PFJ) is a common source of pain and disability for a wide range of patients. It can affect patients in their teens all the way through adulthood. In most cases, the osteoarthritis develops as a consequence of patello-femoral maltracking, dysplasia or imbalance, and has often been associated with anterior knee pain or instability for most of the patient’s adult life. There is often a strong family history, and it is not uncommon to treat 3 generations of the same family with different stages of the condition.
Symptoms can vary widely, with radiological signs often correlating poorly with symptoms. Patients will usually complain of anterior knee pain, particularly when loading the PFJ. Such activities include stair and hill climbing, often with symptoms worse on descent. Transfer pain, when getting into or out of a chair is common. Characteristically, walking or even running on flat surfaces does not result in much pain. As symptoms become severe falls are not uncommon, particularly in the elderly, due to very inefficient and painful patella-femoral function.
There are a wide variety of signs including knee effusion, patella-femoral crepitus, synovitis, patellar instability.
- Weight reduction: The PFJ takes 3-5 times body weight loads, whilst the tibiofemoral joint is subject to 1-2 times body weight.
- Avoidance of provocative environments. Although difficult, avoidance of stairs, inclines etc can help when recovering from acute exacerbations.
- Optimise quadriceps function
- Assist with patello-femoral maltracking with taping
- Ensure hamstring and other muscle groups are supple
As in most orthopaedic conditions, surgery is usually only performed after a failure of non-operative measures. Surgery is always combined with a comprehensive physical therapy regime.
- Arthroscopy and lateral release: There is a very limited role to arthroscopy alone. If there is debris or a loose body, arthroscopy alone may be indicated. Combining a lateral release with arthroscopy has been performed, however, extensive lateral release defunctions the Vastus lateralis and can unbalance the quadriceps mechanism further.
- Tibial Tuberosity Transfer: This operation aims to unload the PFJ by lengthening the quadriceps lever arm, which reduces joint reaction force through the PFJ. This operation often reduces pain and restores extensor mechanism function. In this surgery the tibial tuberosity is moved anteriorly and medially to improve tracking and unload the PFJ. Screws are used to stabilise the fragment until bone union occurs, usually by 6 weeks post-operative. Rehabilitation usually takes 6 months to plateau.
- Isolated Patellofemoral Joint Replacement: A small number of patients are suitable for Isolated PFJ replacement. Those suitable have end stage OA, often with joint erosion, with pristine tibiofemoral articulation. The benefit of such an operation is that normal tibio-femoral kinematics are preserved, whilst the painful PFJ is rebalanced. Longer term results of this operation vary, depending upon patient selection, surgical technique and implant choice. Reflecting these complexities, the revision rate at 5 years is approximately 15% according to the AOA National Joint Replacement Registry. Other published studies report better results.
- Total Knee Replacement (TKR): As with all end stage arthritis of the knee, TKR is a viable procedure for end stage PFJ OA. Often patients have coped with isolated PFJ pain until other elements of the knee degeneration occurs. The knee decompensates and then pain gets worse. This is a common scenario, and in the older patient is usually well managed with TKR.
Should I have Bilateral Simultaneous Knee Replacement?
Many patients suffer from bilateral knee osteoarthritis and want to consider having the surgery in one go, rather than as two separate procedures. As with most things there are pros and cons to this question.
The patient who may be considered suitable for bilateral simultaneous surgery is that person who has severe pain and or dysfuntion affecting both knees equally. Usually if one knee is very sore and the other is not too bad, then one knee at a time is recommended. Often after the first knee replacement is performed, the other knee settles a little, giving sometimes years before surgery needs to be considered on the other side.
On the other hand occasionally the pain and disability associated with both knees is severe and bilateral surgery is considered.
The benefit of bilateral simultaneous surgery is that the two knee operations are compressed into one procedure, which shortens the combined rehabilitation phase and costs of two separate procedures. This is particularly helpful if two periods of rehabilitation cause work or sick leave issues. Some authors note that the potential complication rate after simultaneous bilateral surgery is lower than staged bilateral surgery.
The disadvantages of bilateral simultaneous knee replacement surgery include a longer operating time, higher blood loss, higher likelihood of blood transfusion and a higher risk of cardiovascular complications.
In general I will consider patients for bilateral simultaneous knee replacement if they fulfil the following criteria.
- Aged <80
- No systemic cardiovascular disease
- No Diabetes
- No Kidney disease
- Severe bilateral disabling knee pain
Each individual patient will have their own circumstances and health to consider. Usually a thorough preoperative medical review will determine suitability for the procedure. You should discuss with your surgeon your suitability if you have severe bilateral knee osteoarthritis and are considering knee replacement.
Pre Op severe Osteoarthritis
Post Op Bilateral Staged Knee Replacements
When can I drive after knee replacement?
I am often asked by patients when they can return to normal activities such as driving. There are two main considerations here: comfort and safety.
The patient must be comfortable enough to not require strong painkillers which could cause drowsiness. They must be able to get in and out of the car with good comfort and bend the knee well enough so that they can use the controls. Sometimes this can be achieved within 4 weeks, but often may take longer.
The safety factor is harder to quantify and can vary widely between patients. Some research has been done to suggest that reaction times for braking are sufficiently returned by 4 weeks. A more traditional approach has been to delay the return to driving, particularly for the right knee, until 6 weeks post operation.
Finally, the decision to return to driving should be discussed with your surgeon, as individual patient’s circumstances, age and general health vary widely.
Hip Replacement Technology – Bearings
At the heart of every hip replacement is the bearing, or ball and socket joint. Originally the bearing choice was very simple. You could only have a metal femoral head (or ball) on polyethylene cup (or socket) bearing. This was the bearing that English orthopaedic surgeon, Sir John Charnley settled upon when he popularised total hip replacement in the 1960’s. Over the following two decades it became clear that despite the great benefits of hip replacement, there were problems related to wear of the implant, particularly in younger or higher demand patients. This wear would often lead to debris within the prosthetic joint. As wear debris accumulated, the body produced inflammatory cells in an effort to neutralise the effects of the wear particles. This inflammatory response then lead to prosthetic loosening, which could cause pain and loss of function for the patient.
Recognising the problems associated with wear, the orthopaedic industry has developed newer bearing materials in the hope of delivering longer life implants. I have summarised the current options for most patients below.
- Metal Head on Highly cross linked polyethylene (HXLPE). This combination of bearing surface is now highly durable and offers predictable long term function out to at least 15 years. The wear debris generated is much less than the original technology and is an excellent choice for most patients requiring hip replacement.
- Ceramic head on HXLPE. This option combines the very smooth and hard properties of a ceramic head on the proven HXLPE. Wear rates are better than metal on polyethylene, particularly if there is other debris in the hip joint. Because the ceramic is so hard, it is difficult to scratch, making this combination very wear resistant. Past concerns regarding cracking or fracture of the ceramic head have largely disappeared due to advances in manufacturing technology. This option is suitable for patients with moderate to high demands and an expected lifespan of 20+ years.
- Ceramic head on ceramic liner. This combination has the lowest of all wear rates. The wear debris generated is so low that it is hard to record, even in hip simulator studies. It is, however, more susceptible to poor alignment and has the disadvantage of potentially causing ‘squeaks’, or noise due to loss of lubrication. Even if the implant does wear, the products of that wear do not appear to cause the inflammatory response that happened with the polyethylene bearings. This bearing combination is most suited to younger patients with life expectancy over 30 years.
- Metal head on metal socket. Recently, there has been a lot of publicity around ‘faulty hip replacements’. Many of these replacements were metal on metal hips. As a result of the problems associated with this type of bearing it is rarely used in Australia. Most companies have withdrawn this technology from sale. Most of the problems occurred as a result of fine metallic particles causing an inflammatory response, often causing pain, loosening and bone damage. This bearing combination is not recommended.
Fig 1. Charnley Total Hip Replacement
Fig 2. Metal on Highly Cross Linked Polyethylene (HXLPE)
Fig 3. Ceramic on ceramic bearing
Anterior Cruciate Ligament Rupture: Who should have surgery?
Anterior cruciate ligament (ACL) rupture is a common injury among athletes. It usually occurs after a rotational injury whilst pivoting off the affected leg. The injury usually causes acute pain and swelling which often settles within a few weeks. There is, however, residual instability in the knee, particularly with movements such as pivoting or sidestepping.
Rupture of the ACL should be managed with reconstruction if it is likely that the patient will return to pivoting or sidestepping activities in their chosen sporting activities. It is recommended to stabilise the knee before a return to such activities as football, soccer, dance, gymnastics etc to reduce the risk of injury to other structures in the knee such as the meniscus or joint cartilage. It is particularly important in younger athletes to have a stable knee.
For older patients, the choice to have a reconstruction is often dependent upon their daily physical requirements, as well as their planned return to sports or pivoting activities. Many patients will want to continue such activities a skiing, tennis, soccer and running. Many of these patients will elect to proceed to reconstruction.