Abstract
We report two patients who developed osteonecrosis in the contralateral compartment after initial unicompartmental knee arthroplasty (UKA). The first patient was a 77-year-old woman with lateral compartment osteoarthritis of the left knee. She underwent lateral UKA and then 4 years and 2 months later, severe knee pain suddenly occurred due to osteonecrosis of the medial femoral condyle accompanied by collapse of the articular surface. We performed UKA in the medial compartment, and the symptom disappeared. The second patient was a 79-year-old man with medial compartment osteoarthritis of the left knee. He was treated with UKA, and after discharge he continued to use lateral wedge arch support on the basis of his own judgment. One month later, however, lateral knee pain occurred and progressed rapidly. Because severe collapse of the lateral femoral condyle was observed, we performed additional UKA in the lateral compartment.
The symptom disappeared without any decrease in the range of motion. We think that osteonecrosis in the contralatelal compartment may occur as a complication after UKA because of the postoperative increase in loading due to changes in leg alignment. Our results suggest that additional UKA is a useful therapeutic option for this complication as it is not surgically invasive and yields excellent postoperative knee function.
