Loosening of massive proximal femoral cemented endoprostheses. Radiographic evidence of loosening mechanism.

A review of the radiographs of 24 patients with massive proximal femoral cemented tumor endoprostheses revealed a repetitive radiographic sequence that culminated in implant loosening. The initial step was osteolysis of the proximal femur at the bone-prosthesis junction (13 of 24 cases, 54%). The osteolysis then progressed into the adjacent periprosthetic bone-cement interface as a radiolucent line (5 of 24 cases, 21%), followed by extension along the stem, culminating in implant loosening (4 of 24 cases, 17%). Two prostheses (8%) have required revision for loosening. The proximal osteolysis was noted prior to the appearance of progressive periprosthetic radiolucent lines in 11 patients and simultaneously in 2 but never followed periprosthetic radiolucent lines (P < .05). These findings are consistent with loosening by debris-induced osteolysis. This loosening sequence, confirming previous observations of cemented component loosening, should encourage efforts to prevent or delay the onset of this sequence.