Acetabular osteolysis is problem affecting long-term survival of total hip prosthesis.
CASE REPORT: a 71 year old man was operated in December 2005 with a total uncemented hip arthroplasty. Immediate evolution was favourable but at 4 months postoperatively he came with the complaints of left back pain irradiating in the left thigh. X-rays revealed the presence of a lytic lesion around the acetabulum with secondary dispalcement of the acetabular cup. Further investigations ruled out infection and confirmed the presence of multiple myeloma. The wear and shear particles of polyethylene or metal are the leading cause of reactive osteolysis in total hip arthroplasty, nevertheless multiple myeloma or metastatic lesions should be included in the differentail diagnosis.