Poor bone quality or hip structure as risk factors affecting survival of total-hip arthroplasty

Background The principal long-term complication after total hip arthroplast y (THA) has been aseptic fixation failure. Many hip prostheses and operativ e techniques have been developed to improve outcomes, but few measures have been taken to cope with poor bone quality or hip structure. We assessed ri sk factors for aseptic fixation failure after THA. Methods We assessed, by multivariate analysis, survival of 405 primary Char nley THAs to identify risk factors for aseptic fixation failures. We also i nvestigated risk factors for development of rapid polyethylene wear (penetr ation depth of the femoral head into the socket polyethylene greater than o r equal to 2 mm/year). Findings In the entire series of 405 THAs, with use of radiographic fixatio n failure or revision for a loose socket as the endpoint, development of ra pid polyethylene wear and the preoperative diagnosis of atrophic osteoarthr osis (defined by scarce osteophyte formation) were identified as risk facto rs for socket loosening (p less than or equal to 0.02). A medullary canal w ith an unfavourable geometry (a stovepipe canal, Noble's canal-flare index <3.0) was the only risk factor for femoral fixation failure (p less than or equal to 6.7 x 10(3)). The only variable related to development of rapid p olyethylene wear was the type of steel used in the femoral prosthesis-Ortro n 90 prostheses significantly lowered the rate of development of rapid wear from 12.7% to 0.4%. In the 248 THAs in which these femoral prostheses were used, socket survival was affected only by the preoperative diagnosis of a trophic osteoarthrosis (for radiographic fixation failure and revision, p=4 .0 x 10(-5) and p=0.042, respectively). Interpretation in THA, the critical risk factors are poor bone quality, whi ch manifests as atrophic osteoarthrosis, for socket survival and poor bone structure for femoral-prosthesis survival. To ensure longer durability of T HAs, these factors should be assessed further and efforts, especially biolo gical initiatives, should be made to resolve them.