The effect of pre-operative cardiorespiratory fitness on functional and subjective outcomes following total hip and knee arthroplasty: a single centre, observational study.

Abstract

Aim: The aim of this study was to assess the effect of pre-operative cardiorespiratory fitness (peak VO2) on physical and subjective recovery from total hip or knee arthroplasty. A secondary aim was to assess the relationship between daily step count or estimated peak VO2 via the Duke Activity Status Index (DASI) questionnaire, on post-operative recovery.

Methods: In this secondary analysis of a prior randomised controlled trial, 51 patients (69 [8] y; 25 female; peak VO2: 20.1 [7.8] mL/min/kg) scheduled for total hip (n=23) or knee (n=28) arthroplasty underwent pre-operative assessment (cardiopulmonary exercise testing, physical function tests [30-second sit to stand, timed up and go, knee range of motion]), accelerometry and subjective questionnaire (DASI). Post-operative assessments included length of hospital stay, the Surgical Recovery Scale (SRS) and repeated functional assessments.

Results: A low pre-operative peak VO2 (i.e., <15mL/min/kg) was associated with five fewer sit-to-stand reps (95% CI [confidence interval]: 3 to 7; p=0.002), 3,500 fewer daily steps (95% CI: 1,053 to 5,867; p=0.006) and poorer subjective surgical recovery at 7-days (-12 arbitrary units [AU], 95% CI: -3 to -22, p=0.014) and 6-weeks post-operative (-13 AU, 95% CI: -5 to -21; p=0.003). Estimated pre-operative peak VO2 using the DASI questionnaire was moderately correlated with post-operative daily step count (r=0.51, p <0.001); post-operative daily step count increased by 500 steps for every 1mL/min/kg increase in estimated peak VO2.

Conclusion: Pre-operative peak VO2 was associated with physical and subjective recovery following total hip or knee arthroplasty. Daily step count and estimated peak VO2 via the DASI questionnaire had similar moderate associations with post-operative functional outcomes as directly measured pre-operative peak VO2 and may be acceptable alternatives to predict recovery following hip or knee arthroplasty.