Predicting poor physical performance after total knee arthroplasty

Abstract

The purpose of this study was to develop a preliminary decision algorithm predicting functional performance outcomes to aid in the decision of when to undergo total knee arthroplasty (TKA). One hundred and nineteen patients undergoing primary unilateral TKA were evaluated before and 6 months after TKA. A regression tree analysis using a recursive partitioning function was performed with the Timed Up and Go (TUG) time, Six-Minute Walk (6MW) distance, and Stair Climbing Test (SCT) time as measured 6 months after TKA as the primary outcomes. Preoperative measures of functional performance, joint performance, anthropometrics, demographics, and self-reported status were evaluated as predictors of the primary outcomes 6 months after surgery. Individuals taking ≥10.1 s on the TUG and aged 72 years or older before surgery had the poorest performance on the TUG 6 months after surgery. Individuals walking <314 meters on the 6MW before surgery had the poorest performance on the 6MW test 6 months after surgery. Individuals taking ≥17 s to complete the SCT and scoring <40 on the SF-36 mental component score before surgery had the poorest performance on the SCT 6 months after surgery. Poorer performance preoperatively on the 6MW, SCT, and TUG, was related to poorer performance in the same measure after TKA. Age and decreased mental health were secondary predictors of poorer performance at 6 months on the TUG and SCT, respectively. These measures may help further develop models predicting thresholds for poor outcomes after TKA.

Figure 1

At each node, the mean TUG time at 6 mos is listed as well as the number of patients at that split and the 95% confidence interval for the mean. Squares indicate terminal nodes. The cut point for each split is displayed on the vertical line stemming from the split.

Figure 2

At each node, the mean 6MW distance at 6 mos is listed as well as the number of patients at that split and the 95% confidence interval for the mean. Squares indicate terminal nodes. The cut point for each split is displayed on the vertical line stemming from the split. NMVC Non is normalized maximum voluntary contraction of quadriceps in non-surgical limb

Figure 3

At each node, the mean SCT time at 6 mos is listed as well as the number of patients at that split and the 95% confidence interval for the mean. Squares indicate terminal nodes. The cut point for each split is displayed on the vertical line stemming from the split.