The aim of this study was to explore the pre-operative predictors of the function component of the WOMAC one year after total knee arthroplasty (TKA) using a hierarchical regression model. The pre-operative and one year post-operative results of 71 patients with knee osteoarthritis who underwent TKA were analysed. First the correlation between the post-operative function component of the WOMAC and a range of pre-operative measures were calculated to determine the independent variables for the hierarchical regression model. Independent pre-operative measures which showed a significant correlation with post-operative function were then entered in the model. Pre-operative measures were divided into three types according to International Classification of Health: (i) Personal characteristics, (ii) body structures and function and (iii) Psychosocial variables. The following pre-operative measures were correlated with post-operative function: Knee flexion (r=-0.254), extensor strength (r=-0.338), flexor strength (r=-0.257), mental health component of the SF36 (r=-0.304), Tampa scale (fear of movement), (r=0.261), the sense of helplessness due to pain (r=0.264) and Stanford arthritis Self-Efficacy Pain Scale (r=-0.343). This scale is a measure of the person's belief in their capability to cope with their arthritis pain. The higher the score the better the person's self-efficacy. Only independent pre-operative measures were entered in the models. In step 0, we controlled for age and Body Mass Index (BMI), in step 1 we entered knee flexion and extensor strength (model 1) and in step 2 Self-Efficacy was entered in the model (model2). In model1 extensor strength was a significant predictor of post-operative function (beta =-0.242, p=0.028). In the final model (model3) pre-operative extensor strength (beta =-0.242, p=0.07) and Self-Efficacy (beta -0.266, p=0.046) were the strongest predictors of post-operative function. We found that pre-operative muscle strength and psychosocial measures such as the perceived ability to cope with the effects of arthritis pain (Pain Self-Efficacy) were the most meaningful predictors of outcome one year after total knee arthroplasty.Conclusions
High flexion designs are intended to provide a greater range of knee flexion and possibly improve flexion in stiff knees. This study assessed the effects of two implant designs. A posterior stabilised high flexion mobile bearing (MB) design vs a cruciate retaining standard fixed bearing (FB) design. The aim of this study was to assess whether implant design has an effect on the functional outcome one year after total knee arthroplasty (TKA). Ninety patients with knee osteoarthritis on the waiting list for unilateral TKA were recruited and randomly allocated to either the MB or FB group. Patients were assessed between one and four weeks before, and one year after TKA. Primary outcome was knee flexion during high flexion activities of daily living such as stair ascending and descending and squatting as measured using gait analysis. Knee flexion in long sitting using a manual goniometer and the WOMAC were also recorded. Two sample t-tests were used to investigate statistical differences between the two groups pre- and postoperatively. Average age was 69 years. Thirty-three received the MB design and 39 the FB design. Age, gender balance and pre-operative flexion (112 and 113 degrees in the FB and MB groups respectively) were the same in both groups. There were no statistically significant differences in post-operative knee flexion during functional activities. Knee flexion in sitting and the stiffness and function components of the WOMAC were also similar between the two groups (p>0.05). However, post-operatively the WOMAC pain component was slightly higher in the MB group (4.2 vs 2.4 points, p<0.05).Methods
Results
