A clinical prediction rule for predicting a delay in quality of life recovery at 1 month after total knee arthroplasty: A decision tree model.

Background: There is no clinical prediction rule for predicting the prognosis of quality of life after total knee arthroplasty and for assessing its accuracy. The study aimed to develop and assess a clinical prediction rule to predict decline in quality of life at 1 month after total knee arthroplasty.

Methods: This study included 116 patients with total knee arthroplasty in Japan. Potential predictors such as sociodemographic factors, medical information, and motor functions were measured. Quality of life was measured using the Japanese Knee Osteoarthritis Measure at 1 day before surgery and 1 month after total knee arthroplasty. The classification and regression tree methodology was used for developing a clinical prediction rule.

Results: The Japanese Knee Osteoarthritis Measure score pre-total knee arthroplasty (≦34.0 or >34.0) was the best single discriminator. Among those with the Japanese Knee Osteoarthritis Measure score pre-total knee arthroplasty ≦34.0, the next best predictor was knee flexor muscle strength on the affected side (≦0.45 or >0.45 N m/kg). Among those with knee flexor muscle strength on the affected side >0.45, the next predictor was knee flexion range of motion on the affected side (≦132.5°or >132.5°). The area under the receiver operating characteristic curves of the model was 0.805 (95% confidence interval, 0.701-0.909).

Conclusions: In this study, 4 variables were selected as the significant predictor. However, the results of knee flexor muscle strength and knee flexion range of motion were paradoxical. This result suggests that it should be careful to perform surgery to the patients with good preoperative knee function. The clinical prediction rule was developed for predicting quality of life decline 1 month after total knee arthroplasty, and the accuracy was moderate. This clinical prediction rule can be used for screening of patients with total knee arthroplasty.