Total knee arthroplasty for primary knee osteoarthritis: changing pattern over the past 10 years.

OBJECTIVE: To review the epidemiology of total knee arthroplasty for primary osteoarthritis and the change of patient characteristics over the last decade.
DESIGN: Retrospective review.
SETTING: A tertiary referral centre for joint replacement surgery in a teaching hospital in Hong Kong. PATIENTS: All patients who underwent primary total knee arthroplasty for primary knee osteoarthritis from January 2000 to December 2009.
RESULTS: In all, 1157 total knee arthroplasties (589 left and 568 right) were performed on 588 females and 162 males. The annual number of total knee arthroplasties increased from 91 in 2000 to 181 in 2009. The annual number of patients increased from 58 (46 female, 12 male) in 2000 to 159 (117 female, 42 male) in 2009. When compared yearly results, there were no significant changes in the preoperative Knee Society Knee Score, Knee Society Functional Assessment, and passive range of motion of these patients. However, there was a significant decreasing trend with regard to lower limb mechanical axis mal-alignment, from 15.1° deviation from the neutral axis in 2000, to 14.8° deviation in 2004, and then 12.9° deviation in 2009 (mostly varus deformity). There was no difference between left knees and right knees, and between females and males. The mean age of the patients did not show significant change over the past decade, but the number and proportion of patients over 80 years old showed an increase from 4.8% (2000 to 2004) to 13.8% (2005 to 2009). On the other hand, the number and proportion of patients under the age of 60 years did not change.
CONCLUSIONS: There was an increasing trend towards total knee arthroplasties, both in terms of number of operations and patients. The number of younger patients having total knee arthroplasty did not increase over the last 10 years, whereas the number of those older than 80 years increased significantly over that period.