The joint between the underside of the knee cap (patella) and the end of the femur is covered with articular (hyaline) cartilage that can wear out over time. When this happens, the condition is referred to as patello-femoral osteoarthritis. Degeneration of this joint usually occurs concomitantly with that of the rest of the knee joint so it is unusual for patients to develop isolated patello-femoral arthritis. The most common reason for this presentation is previous fracture or trauma to the patella or trochlear groove (the shallow trough that the knee cap slides in). In most instances, patello-femoral arthritis is symptomatic with a creaking sensation in the knee and pain with moderate activity, especially walking downhill. Occasionally, the pain and mechanical symptoms can be disabling. For patients with severe pain and mechanical symptoms, patello-femoral arthroplasty may provide good long term pain relief.
Patient selection is critical to achieve a good outcome and the use of this surgery remains somewhat controversial within the field of orthopaedics. Dr. Solberg offers patello-femoral arthroplasty on patients over age 40 with severe osteoarthritis of the patello-femoral joint, a BMI (body mass index) of 30 or less and failure to achieve good pain relief with other treatments including arthroscopic debridement, visco polymer injection such as synvisc or supartz and oral medication. Below is a link to a recent publication addressing the selection criteria for patients who may be candidates for patello-femoral arthroplasty.
Patello-femoral Selection Criteria, JBJS, 2007
DIAGRAM SHOWING PATELLO-FEMORAL OSTEO-ARTHRITIS
The surgery takes roughly 1 hour and patients stay overnight for pain control. Spinal anesthetic is ideal if possible because it makes pain control after surgery is much easier. In addition, many patients receive an additional femoral nerve block after the surgery. This numbs the area over the front of the thigh and knee for about 18-24 hours after surgery. Patients begin physical therapy by standing the night of surgery and more vigorous therapy begins on the second hospital day. Most patients use a continuous passive motion machine (CPM) the day after surgery and continuing after discharge from the hospital. Patients put their full weight on the leg right after surgery, albeit with some help from the physical therapists. Most patients go home on the second day after surgery.
KNEE CPM MACHINE
Most knee implants are designed to last somewhere between 15-25 years. The factors that influence the rate of wear of the polyethylene liner (the plastic portion of the implant that wears out over time) include activity level (running and impact activities are discouraged as they increase wear), weight (obesity is one of the primary risk factors for total knee arthroplasty mechanical failure) and manufacturing characteristics of the polyethylene. We do not offer total or partial knee arthroplasty in patients with a BMI (Body Mass Index) of greater than 40 (this is the objective definition of morbidly obese). The reasoning is that the relative risk of complications including infection, wound problems, soft tissue balancing problems, patellar tracking problems and component malpositioning is 2-3 times higher in morbidly obese patients. We recommend patients seek help to get their BMI down to a safe level before proceeding with a total or partial knee replacement under less than ideal circumstances. The article below is helpful in understanding the scientific basis for this decision.
Obesity and Knee Replacement Surgery, JBJS-2004
After surgery all patients are started on a medication called low molecular weight heparin to prevent blood clots in the veins of the pelvis and leg. This is the single most common complication after surgery.
This post procedure instruction sheet should answer most of the questions you will have.