by Donald T. Reilly, MD
Donald T. Reilly, MD, is associate professor of orthopaedic surgery, Harvard Medical School, and practices at Beth Israel Hospital, Boston.
While the treatment of knee osteoarthritis with total knee replacement is often the best option, there are many patients for whom its indications are not quite clear. The patient proposed, a 55-year old active man, with symptomatic knee osteoarthritis poses just such a problem. For the purpose of discussion, let us assume that the usual medical treatment and activity modification have been exhausted with the continuation of limiting symptoms. Let us also assume that there is no medical contraindication to a surgical procedure for this patient and that he has a normal life expectancy approaching 20 years.
Since this opinion concerns total knee replacement, let us further assume that arthroscopy has either been done for his mechanical symptoms or significant varus alignment makes him a poor arthroscopy candidate. While arthroscopy remains an option, outcome quality diminishes as deformity and extent of involvement progresses.
The usual surgical options for this individual are either osteotomy or arthroplasty. Few patients are ideal candidates for any procedure and therefore, patient expectations play a key role in the orthopaedist's decision-making process. It is important to ascertain activities that are prevented by the patient's symptoms and for what reasons the patient is deciding to undergo a surgical procedure. If the patient desires to perform heavy physical activity (jogging, tennis, etc.), undergoing an arthroplasty would not be advisable since those activities should not be done afterward. A patient who desires a "normal" knee needs enlightenment on the limitations of orthopaedic intervention in the correction of his problem.
Osteotomy is usually done for the more active, heavier, younger patients (chronologic age is not always indicative of activity) and requires essentially unicompartmental degenerative changes with a correctable deformity. Patients usually can expect a significant decrease in their pain (80 percent) and chondrocalcinosis, inflammatory arthritides and multicompartmental involvement usually diminish the quality of the outcome. Unless a malunion is present without degenerative changes, osteotomy is not usually considered a definitive procedure but more a delaying procedure. It usually decreases pain and delays the need for arthroplasty approximately seven years on the average in most studies.
Osteotomy is a technically demanding procedure, since over-correction of the deformity must be carefully analyzed and accurately carried out. That certain patients' symptoms worsen more rapidly because they are "high adductor loaders," and that these adductor loaders without gait analysis on a force plate are difficult to clinically detect, makes the results of osteotomy variable. The complication rates after osteotomy are higher than those of total knee replacement.
Arthroplasty of the knee has become the definitive procedure for elderly and sedentary patients with improvements in technology and refinements in the surgical technique. Excellent results in this group of patients in the 90 percent range have lead to the increasing use of arthroplasty in other less-qualified patient groups. Infection remains a small but significant problem in the short-term, but wear and loosening of a mechanical system in a biologic environment remains the long-term complication. Arthroplasty will often eliminate a patient's pain and restore function to the point that the patient will use the knee "normally." With arthroplasty comes the responsibility of determining what should, rather than can, be done. Total knee replacement remains the standard arthroplasty with some advocates for unicompartmental replacement. Since very few patients present with knee osteoarthritis amenable to unicompartmental replacement (lesser deformities, intact anterior cruciate ligament and absence of chondrocalcinosis), a surgeon's lack of experience in this complex arthroplasty makes complications more likely. Most studies show shorter longevity for unicompartmental replacement compared to total knee replacement and favor an older patient as the ideal candidate.
Expectation is key
For our specific patient in question, the choice between osteotomy and arthroplasty will hinge overwhelmingly on the patient's activity expectation. If he will modify his activities to sedentary level and severe symptoms persist, the choice will swing toward arthroplasty since it is more reliable in delivering fewer complications and improved pain relief. If the patient would like to attempt to continue vigorous sport activity, the choice would be shaded toward osteotomy. Lack of patellofemoral osteoarthritis, mild lateral compartment involvement, absence of ligamentous instability, good range of motion without large fixed flexion contracture and a deformity limited to a single anatomic site makes for the ideal osteotomy candidate. Obesity has traditionally favored the choice of osteotomy but midterm follow up studies have not shown it to be a dramatic problem with total knee replacement. Long-term studies are needed to elucidate the role of obesity in total knee replacement complications.
Whether osteotomy or total knee replacement is chosen, neither will probably be the last procedure this patient has. Neither will reliably last his almost 20-year average life expectancy. If he is to have total knee replacement after an osteotomy, this procedure requires special attention to ligamentous balancing and surgical exposure (preventing tubercle insertion avulsion) to have good outcomes. If total knee replacement is chosen, long-term follow up should be done approximately every two years or if symptoms occur. Early detection and possible correction of osteolysis and/or loosening from wear before severe reconstructive problems occur is advisable.