For those patients in an appropriate age bracket with a moderate level of demand and isolated patellofemoral arthritis and a stable knee, with a reasonable range of motion, a partial patellofemoral replacement may be a consideration.
Patients with severe arthritis affecting the front part of the knee, known as the patellofemoral joint (PFJ), including the patella and / or trochlea, usually experience frontal discomfort, a grinding sensation and / or noise (crepitus) which is especially noticeable when arising from a seated position, negotiating stairs, or attempting to squat or kneel. If these patients have arthritis affecting other parts of the knee (tibiofemoral compartment) then it is likely that they will require consideration of a total knee replacement, but if they have only isolated arthritis of the PFJ and reasonable range of motion, they may be considered for a patellofemoral “partial knee replacement”. The most successful and commonly used implant in Australia for partial knee replacement of the patellofemoral joint is the AVON patellofemoral arthroplasty. It removes minimal bone and accurately reproduces the congruity of the native PFJ, helping to assist with the smooth tracking of the patella, whilst maintaining a high range of motion and also allows for ease of future conversion to a total knee replacement if necessary. The AVON PFJ partial knee replacement is performed through a minimally invasive surgery (MIS) technique with a small (8-9cm) incision, replacing the worn areas of cartilage only on the trochlea groove (on the front and uppermost part of the femur) and the patella with a small metallic oval shaped implant on the trochlea, and a plastic cap on the undersurface of the patella. The femoral and tibial condyles are left intact as are also the cruciate and collateral ligaments and the surrounding muscles including the quadriceps, and because of this there is significantly less blood loss, shorter hospital stay, lower infection rates and other complications such as deep vein thrombosis (DVT) and pulmonary embolism (PE) are also significantly lower.
Patients usually only require a two night stay in hospital following an AVON PFJ partial knee replacement as compared to a four to seven night stay following a TKR, and generally are able to mobilise without walking aids after one week. Most patients will use strong analgesia for two to four weeks and anti-inflammatories for two to three months and are usually able to resume most normal day to day activities within the first four to six weeks. Recreational activities (walking for fitness, cycling and swimming etc) can usually commence after six weeks, and more vigorous activities (golf, tennis, surfing) after two to three months. Whilst most UKR patients will be walking fairly freely after three or four weeks, and feel like they are able to drive a car, it is a legal recommendation for insurance purposes, that patients who have undergone knee replacement surgery do not drive a motorised vehicle (car, motorbike, truck etc) for a six week period. Returning to work duties is generally possible for clerical type jobs within 3 to 4 weeks, and sooner for some, depending upon the individual’s mobility, analgesia requirement and job demands. Most knee replacements are likely to last for 10-15 years, so depending upon the age and health of the patient at the time of their initial knee replacement procedure (regardless of whether it is a total or partial knee replacement), there is a high likelihood that they will outlast their first knee replacement. Most AVON PFJ knee replacements if performed using prescribed technique, are quite bone conserving, and when ready for revision, can simply be converted to a normal or primary TKR. Thus one of the additional benefits of having an AVON PFJ partial knee replacement as your first knee replacement, is that your next knee replacement will still only be a primary (normal) TKR which should then last for another 10-15 years, meaning that between these two implants, patients usually will have 20 -30 years before needing to be considered for a more complex revision (stemmed) TKR.