Reporting functional outcome after knee arthroplasty and regional anesthesia: a methodological primer

The introduction of ultrasound guidance for regional anesthesia has resulted in an explosion of interest in its use for postoperative analgesia, particularly for orthopedic surgery. Regional anesthesia demonstrates unequivocal superiority compared with systemic opioids with respect to analgesia, reduced opioid consumption, increased patient satisfaction, and earlier achievement of discharge criteria. Improved acute postoperative analgesia can facilitate effective rehabilitation. Investigators are in the early stages of reporting the effects of regional anesthesia on functional outcome. Recent studies reporting functional outcomes have been plagued with sample sizes of inadequate power to generate meaningful results. Furthermore, the functional outcome measures are used inappropriately in terms of clinically meaningful difference, assessment intervals, and/or duration of follow-up. This report aims to address these issues by discussing functional outcomes used in the physiotherapy or orthopedic literature and their appropriate utilization, so that future research into the effects of regional anesthesia can be methodologically sound. Outcomes discussed include those that are physical-performance-based (ie, range of motion, quadriceps strength, Timed Up and Go test, 6-Minute Walk Test, Stair Time, and Self-paced Walk Test) and those that are self-reported (ie,Western Ontario and McMaster Universities Osteoarthritis Index, Knee Osteoarthritis Severity Score, Lower Extremity Function Scale).