Fig. 1

Preoperative radiogram images. Preoperative plain radiograms of the left knee joint showed an osteolytic lesion with scalloping (a). A postoperative plain radiogram showed that the cavity was filled with calcium phosphate cement (b). A plain radiogram after 5 years showed a K-L grade 3 joint space narrowing (c). A plain radiogram after 6 years showed the progressive joint space narrowing; the narrowing by the time of this radiogram was graded as K-L grade 4 (lateral tibiofemoral) and grade 2 (medial tibiofemoral) osteoarthritis (d). A CT imaging showed K-L grade 4 patellofemoral osteoarthritis