Bone-ingrowth hip prostheses in asymptomatic patients: radiographic features.

The radiographic changes of 85 bone-ingrowth femoral prostheses in 77 asymptomatic patients were reviewed. The average postoperative follow-up time was 21.8 months. In decreasing order of frequency, the alterations included (a) remodeling of the proximal medial edge of the cut femoral neck (stress shielding) (98%), (b) linear lucency with a thin sclerotic margin at the prosthesis-bone interface (that may increase in width or length with time) (79%), (c) endosteal sclerosis at the prosthesis tip (36%), (d) heterotopic bone (24%), (e) cortical thickening at the tip of the prosthesis (12%), (f) prosthetic subsidence (7%), (g) intraoperative fracture (7%), and (h) periosteal reaction (4%). In this study, radiographic evidence of these findings was not associated with clinical failure. This is in distinction to the findings in cemented prostheses, in which many of these phenomena (especially the development of increasing width of the lucent line adjacent to the cement or prosthesis) have been associated with failure. Long-term investigations of porous-coated prostheses are necessary. Currently, however, an awareness of the radiographic alterations that occur with asymptomatic bone-ingrowth prostheses can prevent their misinterpretation as abnormal.