Medium-term follow-up of 149 mobile-bearing total knee arthroplasties and evaluation of prognostic factors influencing outcomes.

Objective: To evaluate the medium-term outcomes of a posterior-stabilized mobile-bearing total knee arthroplasty (PS-MB-TKA) and the role of different prognostic factors.
Methods: Patients indicated for a primary cemented PS-MB-TKA between 2002 and 2010 were included and prospectively evaluated using the Knee Society Scoring System (KSS) and the Hospital for Special Surgery (HSS) knee scores. The Knee Society Roentgenographic Evaluation form was used for the radiological evaluation. Different variables were collected and divided into patient- and surgery-related. Logistic regression was used to analyze the correlation between these variables and implants outcomes and survivorship.
Results: In total, 149 cases were included (67.8% female, average age 70.4 years, SD ±9.4). The patella was resurfaced in 12.1% of the cases. All the implants were cemented. The average follow-up was 87.3 months (SD ±21.2). Postoperatively, there was a statistically significant improvement in all the scores. The cumulative survival was 96.2% (SD ±0.02%). At the regression analysis, female gender was associated to worse satisfaction KSS (OR = 0.26), functional KSS (OR = 0.22), and HSS (OR = 0.37) scores. Patellar resurfacing and subsequent contralateral procedures were associated to better functional KSS score (OR = 4.13, OR = 2.21), as well as varus preoperative alignment (OR = 2.12). On contrary, valgus preoperative alignment was associated to worse objective KSS score (OR = 0.23). No variables were correlated to failure or presence of radiolucent lines.
Conclusion: Good medium-term outcomes were obtained using PS-MB-TKA, with a cumulative survivorship of 96.5%. Female gender and valgus preoperative alignment were associated to worse objective and subjective outcomes. Conversely, patellar replacement, subsequent contralateral TKA, and varus preoperative alignment were associated to better functional outcomes.