Predictors of moderate-severe functional limitation after primary Total Knee Arthroplasty (TKA): 4701 TKAs at 2-years and 2935 TKAs at 5-years

Abstract

Objective: Investigate whether body mass index (BMI), comorbidity, gender and age predict patient-reported functional limitation 2- and 5-years after primary Total Knee Arthroplasty (TKA).

Methods: Overall moderate-severe activity limitation was defined as > or = 2 activities (walking, stairs, rising from chair) with moderate-severe limitation. Complete dependence on walking aids or inability to walk was assessed (reference, no dependence). Multivariable logistic regression models were adjusted additionally for income, diagnosis, distance from medical center, American Society of Anesthesiologists (ASA) score and implant type.

Results: Overall moderate-severe activity limitation was reported by 20.7% at 2-years and 27.1% at 5-years. Significantly predictors of overall moderate-severe activity limitation 2-years post-TKA (odds (95% confidence interval)) were: BMI 30-34.9, 1.5 (1.0, 2.0), 35-39.9, 1.8 (1.3, 2.7) and > or = 40, 3.0 (2.0, 4.5) vs BMI < or = 25; higher Deyo-Charlson index, 1.7 (1.4, 2.2) per 5-point increase; female gender, 2.0 (1.7, 2.5); age 71-80, 2.1 (1.5, 2.8) and age > 80, 4.1 (2.7, 6.1) vs age < or = 60. At 5-years post-TKA, significant predictors of overall moderate-severe activity limitation were: BMI 35-39.9, 2.1 (1.4, 3.3) and > or = 40, 3.9 (2.3, 6.5); higher Deyo-Charlson index, 1.4 (1.0, 1.8); female gender, 2.2 (1.7, 2.7); age 71-80, 2.4 (1.7, 3.5) and age > 80, 4.7 (2.8, 7.9). Complete dependence on walking aids was significantly higher at 2- and 5-years, respectively, in patients with: higher comorbidity, 2.3 (1.5, 3.3) and 2.1 (1.4, 3.2); female gender 2.4 (1.5, 3.9) and 1.7 (1.1, 2.6); age 71-80, 1.4 (0.8, 2.6) and 1.5 (0.8, 2.8); and age > 80, 3.2 (1.6, 6.7) and 5.1 (2.3, 11.0).

Conclusions: Modifiable (BMI, comorbidity) and non-modifiable predictors (age, gender) increased the risk of functional limitation and walking-aid dependence after primary TKA. Interventions targeting comorbidity and BMI pre-operatively may positively impact function post-TKA.

Figure 1. Multivariable-adjusted Odds ratio (95% confidence interval) for Moderate-Severe Limitations in Walking, Climbing Stairs, Rising from Chair and overall limitation at 2-years post-Primary TKA

Each figure shows the odds ratio of moderate-severe limitation in each activity (walking, stairs, chair) and for overall limitation for each category of variable as compared to the respective reference category. Each logistic regression analyses for walking, stairs, chair and overall limitation was adjusted for age, gender, BMI, comorbidity, income, distance from medical center, ASA class, operative diagnosis and the type of implant. The dotted line represents an odds ratio of 1. Point estimates of odds ratios are represented by the solid circles; the whiskers represent the upper and lower 95% confidence interval estimates. Variables are significantly associated with the outcome in instances where the 95% confidence interval for the odds ratio does not cross one. For example, 5-point increase in Charlson index, female gender, age 71–80 and >80 and BMI, 30–34.9, 35–39.9 and ≥40 were associated with significantly increased odds of overall moderate-severe activity limitation.

Figure 2. Multivariable-adjusted Odds ratio (95% confidence interval) for Moderate-Severe Limitations in Walking, Climbing Stairs, Rising from Chair and overall limitation at 5-years post-Primary TKA

Each figure shows the odds ratio of moderate-severe limitation in each activity (walking, stairs, chair) and for overall limitation. Each logistic regression analyses for walking, stairs and chair limitation was adjusted for age, gender, BMI, comorbidity, income, distance from medical center, ASA class, operative diagnosis and the type of implant.