Micromotion between the half bearings in the interax prosthesis: a roentgen stereophotogrammetric analysis.
We assessed the migration and movement between the half-bearings of the Interax prosthesis in 18 patients using roentgen stereophotogrammetric analysis (RSA). This study showed movements of the tibial component even in successful knee arthroplasty: 17 prostheses migrated only initially and remained stable after 1 year, whereas 1 prosthesis migrated consistently throughout 3-year follow-up. RSA revealed no or minimal displacement between the half-bearings until the 4-year follow-up, confirming that their fixation to the baseplate was adequate. In the case of loosening, a rotation about the longitudinal axis of 1.3 degrees and a medial-lateral translation of 0.5 mm was observed between the half-bearings. Cold flow was revealed by RSA in the posterior region of the medial half-bearing.
Marcacci
M
M
Biomechanics Laboratory, Rizzoli Orthopedic Institute, Bologna, Italy.
Soavi
R
R
Loreti
I
I
Bragonzoni
L
L
Iacono
F
F
Visani
A
A
D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D005548:Foreign-Body Migration / Q000000981:diagnostic imaging*; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery; D010780:Photogrammetry; D011474:Prosthesis Design; D011859:Radiography; D016059:Range of Motion, Articular; D012399:Rotation