LOOSENING OF MASSIVE PROXIMAL FEMORAL CEMENTED ENDOPROSTHESES - RADIOGRAPHIC EVIDENCE OF LOOSENING MECHANISM

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