No difference in patellar position between mobile-bearing and fixed-bearing total knee arthroplasty for medial osteoarthritis: a prospective randomized study
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Total knee arthroplasty (TKA) is the treatment of choice for severe osteoarthritis of the knee. Many studies have been performed comparing mobile- and fixed-bearing designs; however, there are insufficient data regarding the patellar position in either system. This study aimed to compare the resultant patellar position with a mobile- versus a fixed-bearing TKA and the influence of both designs on clinical outcomes.
Materials and methods
In this prospective randomized study, between 2007 and 2009, 160 TKA patients were assessed; 79 received a mobile-bearing and 81 received a fixed-bearing implant, for medial compartment osteoarthritis. A posteriorly stabilized, HLS Noetos knee prosthesis (Tornier, Saint-Ismier, France) was used in all cases. The only difference between the groups was whether the tibial component incorporated a fixed or mobile bearing. The patella was resurfaced in all cases. The International Knee Society Score (KSS) and the patellar tilt and translation were compared post-operatively. Patellar translation and patellar tilt analyses were subdivided into two subgroups (< 5 mm vs > 5 mm and < 5° vs > 5°).
The KSS was not statistically different between the groups at a mean follow-up of 7.4 years (range 5–11 years). Patellar translation and patellar tilt were not statistically different between the groups. When considering the patellar translation subgroup analysis, a significantly increased risk of patellar translation, greater than 5 mm, was found in the mobile-bearing group compared to fixed-bearing group (OR = 2.3; p = 0.048) without generating any meaningful difference in clinical outcomes.
The theoretical advantages of mobile-bearing implants compared to fixed-bearing implants were not demonstrated in this randomized study, at mid-term follow-up. In daily practice, the choice between mobile-bearing and fixed-bearing designs should be based on the experience and clinical judgment of the surgeon.
Level of evidence
Prospective randomized study, level I.
KeywordsTotal knee arthroplasty Total knee replacement Mobile bearing Fixed bearing Patellar position
No funding was received for this study.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflict of interest for this study.
Ethical approval was obtained from the Institutional Review Board of Hospices Civils de Lyon and Lyon 1 university. (study ID numbers 2005.407/36).
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