Changes in knee motion over the first 3 years with a mobile-bearing prosthesis.
The present work aims to evaluate the mobility of the polyethylene bearing in 25 patients implanted with a mobile-bearing PCL-retaining TKR (Interax ISA, Striker Howmedica) under in vivo, weight-bearing conditions over 3 years' follow-up. We compared the bearing motion in response to specific tests in two consecutive follow-ups with Roentgen Stereophotogrammetric Analysis (RSA). Results showed that polyethylene continued to displace on the tibial baseplate over time: longitudinal rotations and medio-lateral translations tended to increase at the second follow-up (mean increases 0.7+/-2.5 degrees and 0.34+/-1.08 mm, respectively), while sagittal translations did not show any relevant change. Longitudinal rotations and AP translations were preserved when present at both follow-ups. Nevertheless, no statistical evidence of repeatable pattern of motion was found, since bearings frequently reversed their pattern of motion between the two follow-ups. The unconstrained polyethylene mobility resulted in an unrepeatable, erratic pattern of bearing motion intra-patient and over time. The changes in knee motion were found not to affect the clinical results over the first 3 years of follow-up. As in a fixed-bearing design, mobile-bearing design was not able to reproduce normal knee kinematics.
Russo
Alessandro
A
Biomechanics Laboratory at Istituti Ortopedici Rizzoli, Via di Barbiano 1/10 40136, Bologna, Italy. a.russo@biomec.ior.it
Montagna
Luisa
L
Bragonzoni
Laura
L
Visani
Andrea
A
Marcacci
Maurilio
M
D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D019544:Equipment Failure Analysis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D010780:Photogrammetry; D020959:Polyethylene; D011474:Prosthesis Design; D016474:Weight-Bearing
D020959:Polyethylene