Three Practical Methods for Estimating Preoperative Cardiorespiratory Fitness in Patients With Severe Hip or Knee...

Low preoperative cardiorespiratory fitness is associated with poorer functional and subjective recovery following hip or knee arthroplasty. The objective of this study was to evaluate the ability of simple, indirect assessment tools (the Duke Activity Status Index, daily step count, and timed up and go test) to estimate directly measured cardiorespiratory fitness and identify patients with low preoperative fitness (<15 mL/kg/min) among those with severe hip or knee osteoarthritis.

Ninety-one patients with severe hip or knee osteoarthritis who were scheduled for total joint arthroplasty were recruited. Within 1 week before surgery, participants performed symptom-limited maximal cardiopulmonary exercise testing, the Duke Activity Status Index questionnaire, accelerometry to determine daily step count, and the timed up and go test.

All three indirect tools provided strong estimates of peak oxygen consumption ( $\dot{V}$ O₂) (r² ≥ 0.61). The Duke Activity Status Index slightly underestimated peak $\dot{V}$ O₂ by 0.9 mL/kg/min. All three metrics performed strongly in their ability to accurately identify patients without a peak $\dot{V}$ O₂ < 15 mL/kg/min; however, their accuracy to positively predict peak $\dot{V}$ O₂ > 15 mL/kg/min was only fair.

These simple, practical, cost-effective tools have utility for estimating preoperative fitness to rule out low fitness. These tools could be used by perioperative clinicians for identifying patients who may not require preoperative cardiopulmonary exercise testing, thereby optimizing resource allocation.