Table 2.
Logistic regression analysis exploring preoperative expectations as a predictor of one year outcome following knee arthroplasty
| Expected impact of pain on life one-year after arthroplasty 4 | Non-Return to Desired Activity 1 n=1012 |
Dissatisfaction with Surgical Outcome 2 n=875 |
Not Achieving OKS MIC 3 n=945 |
|||
|---|---|---|---|---|---|---|
| Crude OR (95% CI) |
Adjusted OR 5 (95% CI) |
Crude OR (95% CI) |
Adjusted OR 5 (95% CI) |
Crude OR (95% CI) |
Adjusted OR 5 (95% CI) |
|
| mild (vs. none) | 1.6 (1.2 to 2.3)** | 1.6 (1.1 to 2.2)** | 1.5 (0.8 to 2.8) | 1.4 (0.8 to 2.7) | 1.6 (1.0 to 2.7)* | 1.5 (1.0 to 2.5) |
| moderate-to-extreme (vs. none) | 2.6 (1.5 to 4.5)** | 2.3 (1.3 to 4.1)** | 4.3 (1.9 to 9.4)** | 4.0 (1.7 to 9.3)** | 3.1 (1.6 to 6.1)** | 3.1 (1.5 to 6.3)** |
*p<0.05; **p<0.01; statistically significant findings are highlighted in bold
An odds ratio > 1 implies that the expectation group is less likely to return to desired activities, be satisfied with surgery or achieve meaningful improvement on the OKS at 1 year post knee arthroplasty compared to those who expected pain to have no impact on life 1 year after knee arthroplasty (reference group);
Participants were asked preoperatively: ‘What activity does your knee stop or limit you from doing that you wish to return to after your operation?’ At 1 year post-operation they were asked: ‘Have you been able to return to the activity (or activities) that your knee stopped you from doing one year ago?’ (yes/no);
Participants responded to the following question at one year post-surgery (‘we would like to know your overall satisfaction with the outcome of your operation’) dissatisfied was defined as a response of ‘somewhat dissatisfied or very dissatisfied’ as opposed to ‘very satisfied or somewhat satisfied‘;
Baseline OKS was subtracted from 1-year OKS and a minimal important change cut-off of 7-points was applied;
Assessed using the following question: ‘Overall, how much do you expect that pain in your knee will interfere with your life one year after surgery?’ with responses on a 5-point Likert scale (Not at all, Mildly, Moderately, Severely, Extremely);
Adjusted for covariates: age at operation, education level, smoking, body mass index, co-morbidities, baseline EQ-5D, type of surgery (uni-compartmental knee arthroplasty vs. primary total knee arthroplasty);
OR: Odds Ratio; OKS: Oxford Knee Score; MIC: minimal important change