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Arthroplasty for isolated patellofemoral OA is rare but can offer long-term pain relief
Chief Medical Editor Douglas W. Jackson, MD, asks John H. Newman, FRCS, 4 questions about isolated patellofemoral knee arthroplasty.
Isolated patellofemoral osteoarthritis with disabling symptoms is an infrequent problem in most orthopedic practices. When it is present and the patient has severe persistent symptoms, the surgeon may offer a total knee replacement or an isolated replacement of the patellofemoral joint as a potential solution. I have turned to John H. Newman, FRCS, for this month’s interview and asked him to share his long standing interest in this area.
Douglas W. Jackson, MD
Chief Medical Editor
Douglas W. Jackson, MD: Isolated replacement for patellofemoral osteoarthritis of the knee remains controversial. What are your indications for surgical intervention?
John H. Newman, FRCS: Indications for isolated patellofemoral replacement are still not totally defined but broadly speaking it is for cases in which there is significant damage to the patellofemoral joint with good preservation of the tibiofemoral joint. Fortunately not all such patients develop severe symptoms but if they do and fail to respond to conservative treatment isolated patellofemoral replacement should be considered.
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The best cases are those who have suffered with patellofemoral instability probably in association with trochlear dysplasia and have developed patellofemoral arthritis at an early age while their tibiofemoral joint is still well preserved. Such cases benefit from the improved stability of a trochlear groove as well as replacement of the damaged joint. Other indications include patellofemoral arthritis in the absence of instability, pain and instability following patellectomy and degenerate changes after patella fracture.
The treatment is definitely not indicated for adolescent anterior knee pain, though some patients with demonstrable full-thickness cartilage loss on both surfaces of the joint but a near normal X-ray can benefit.
Jackson: It has been my impression that a higher percentage of surgeons in the United Kingdom have not replaced the patellofemoral joint in their partial (ignoring its presence) and in total knee replacements? How would you explain my perceived difference from North America in this approach to managing chronic patellofemoral changes?
Newman: There is no definitive answer to whether the patella should be resurfaced during total knee replacement. Certainly, in the United Kingdom many surgeons believe this is unnecessary and leads to increased complications, though the evidence is slim. Undoubtedly the majority of patients treated without patella replacement do well, but it is to be noted that the most common secondary operation in the United Kingdom following total knee replacement is secondary patella resurfacing.
It has also been observed that many patients with patellofemoral pathology experience no symptoms and thus when unicompartmental replacement is undertaken some surgeons believe that changes in the patellofemoral joint can be ignored. This approach has been championed by the Oxford school which has good evidence to support it. I personally would not ignore the patellofemoral joint if it appears to be symptomatic.
Jackson: How long would you expect the localized patellofemoral replacement to survive, assuming no disabling progression in the other compartments of the knee?
Newman: I believe that if an isolated patellofemoral replacement is performed well, with true attention to tracking of the patella and rotation of the trochlear component, then the implant should survive for 20 or more years. There is no evidence in the literature of trochlear loosening and few cases have failed because of polyethylene wear.
The major problems with isolated patellofemoral replacement have been persistent or recurrent maltracking which has been much diminished with the more modern broader prostheses; and progression of arthritis in the tibiofemoral compartment. The latter is unlikely for many years in the younger group with trochlear dysplasia but can occur in older patients; therefore careful assessment of the tibiofemoral joint is necessary.
Jackson: What are some critical points in the preoperative establishment of localized patellofemoral disease and assessing the life expectancy of the remaining knee cartilage in the knee?
Newman: In the majority of cases simple radiological assessment is satisfactory because the patellofemoral disease can usually be demonstrated. If there is any doubt about the state of the tibiofemoral joint, it can be inspected at surgery. If it is found to be unsatisfactory a total knee replacement (TKR) can be performed. In the elderly the tibiofemoral articular cartilage must be intact since TKR is an option, however in the middle-aged group it may be preferable to accept some minor damage rather than perform the much more destructive operation of TKR in a relatively young patient.
In a few cases it is difficult to demonstrate the articular cartilage damage in a patient who has compelling patellofemoral symptoms. In such situations an MRI scan or arthroscopy can be helpful because I am unhappy about undertaking an isolated patellofemoral replacement for symptoms in the absence of significant demonstrable pathology.
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Images: Newman JH |
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For more information:
- John H. Newman, FRCS, is a consulting orthopedic surgeon. He can be reached at 2 Clifton Park, Clifton Bristol BS8 3BS; 0117 9064213; e-mail: j.h.newman@2cp.co.uk. Orthopedics Today was unable to determine whether he has a direct financial interest in any products or companies mentioned in this article.