Predictors of outcome after TKA- ‘The Unhappy Knee’

Wanshou Guo MD.
Approximately 20% of TKA recipients up to five years following TKA are unhappy or dissatisfied with their outcome. The cause or causes of an unhappy knee are not well defined. Through secondary analysis of prospectively collected data from an existing cohort from a prospective observational study of over 1000 public and private TKA recipients from 18 public and private high volume arthroplasty hospitals across Australia, with the primary diagnosis of osteoarthritis. Pre-surgery data includes patient medical history, Oxford Scores and EQ5D scores; surgical and acute-care data including: prosthesis type, surgical and anaesthetic approaches, use of continuous passive motion, cryotherapy, tranexamic acid, surgical drains, blood transfusion; type of rehabilitation, and post-discharge complications. Global

perceptions of improvement and repeat of the Oxford and EQ5D scores are obtained up to 365 days post-surgery. Data is available on 1017 patients (56% female), with a mean age 68yrs, and BMI 32. 68pts (7%) were dissatisfied with the outcome of their surgery, and 141pts (14%) believed TKA did not substantially improve their knee problems (success) at one year after surgery. Insurance (p <0.001), and ASA status (p=0.02) were important predictors of patient satisfaction and success at one year after surgery. The development of complications after TKA significantly affects patient rated satisfaction and success (p<0.001).Patients who had bilateral TKA (8%, p=0.01), surgery performed under spinal anaesthetic (p=0.03) had less complications, whereas older patients (p=0.04), obesity (p=0.03), a background of cardiovascular disease (p=0.05), or obstructive sleep apnoea (p=0.03) were at higher risk of developing complications. Improvement in OKS one year after TKA was less in compensation related surgery (p=0.004), better in non-obese patients (p=0.004), and patients who had surgery in private hospitals (p=0.01). Conclusion: The factors instrumental in the development of an “unhappy knee” after TKA, vary between individuals and may be multifactorial within the one individual. Compensation and ASA status, the development of significant post-operative complication are strong predictors for dissatisfaction and lower rates of perceived success one year after TKA.