Psychometric properties of visual analog scale assessments for function, pain, and strength compared with disease-specific upper extremity outcome measures in rotator cuff repair

BACKGROUND: Patient-reported outcome measures (PROMs) are being increasingly used in orthopedic surgery; however, there is significant variability and burden associated with their administration. The visual analog scale (VAS) for function, strength, and pain may represent a simple and efficient way to measure outcomes, specifically after rotator cuff repair (RCR) surgery. PURPOSE: To define the efficiency and longitudinal psychometric properties of VAS instruments assessing function, strength, and pain after RCR. METHODS: Single-question VAS measures assessing function, strength, and pain as a percentage of normal were administered alongside legacy PROMs in patients undergoing RCR. VAS and PROMs were administered at preoperative, 6- and 12-month time points between June 2017 and April 2018. An electronic registry was used to examine time-to-completion data. PROM performance was assessed using Spearman correlation coefficients. Both absolute and relative floor and ceiling effects were examined. Effect size was measured at 6 and 12 months through the calculation of Cohen's d coefficient. Receiver-operating curves with area under the curve calculations were used to determine the ability of preoperative VAS scores in predicting minimally clinically important difference achievement on American Shoulder and Elbow Surgeons score (ASES). RESULTS: A total of 190 patients (55.6 ± 10.9 years, 66.9% male) met criteria. The 3 VAS PROMs required less time to complete than ASES (1.36 ± 1.12 vs. 5.17 ± 2.39) and Patient-Reported Outcome Measurement Information System (PROMIS) Upper Extremity v2.0 (UE) Computer Adaptive Test (1.72 ± 1.48). Compared with ASES, VAS function, strength, and pain demonstrated fair correlations preoperatively (r = 0.44-0.46) that improved to good at 6 months (r = 0.61-0.67) and further improved at 1 year (r = 0.62-0.78). The performance of VAS measures with other function PROMs was comparable with performance relative to ASES, with poor to very good correlations preoperatively (r = 0.21-0.62) that improved to good to excellent by 1 year (r = 0.62-0.94). A significant relative ceiling effect was demonstrated by PROMIS UE at 12 months (16.9%). Large effect sizes were demonstrated by the ASES, Single Assessment Numeric Evaluation, Constant, PROMIS UE, and VAS function and strength instruments (Cohen d ≥ 0.8). CONCLUSION: Single-question VAS assessments for function, strength, and pain are an efficient means for assessing outcome in RCR surgery and may be particularly useful in the postoperative setting. VAS instruments collectively trended toward floor effects preoperatively, suggesting that legacy instruments may more appropriately establish preoperative baselines. However, in the postoperative setting, VAS instruments demonstrate good-to-excellent correlation, minimized time-to-completion, and no appreciable floor or ceiling effects.