On the correlation between micromotion and histology of the bone-cement interface. Report of three cases of knee arthroplasty followed by roentgen stereophotogrammetric analysis.

The bone-cement interface from the tibial components in three clinically successful unicompartmental Marmor arthroplasties was studied histologically. The migratory behavior of the prostheses had been followed by roentgen stereophotogrammetic analysis (RSA) since their insertion 5-7 years prior to retrieval for reasons other than mechanical loosening. The prostheses migrated during the first 3 years, after which no further migration occurred. Clinical and RSA data thus suggest stable fixation. All interfaces were made up entirely of soft tissue. In the sagittal portion, between the prosthesis and the tibial eminence there was mostly fibrous tissue, while the region underneath the prostheses consisted largely of highly differentiated fibrocartilage. This histologic picture is compatible with a migratory pattern, as measured by RSA, of stable fixation after an initial remodelling period, which the authors believe has the potential of good long-term results.