The Short Form-12 (SF-12) was developed as a shorter version of the SF-36, yet there has been limited validation of its reliability at measuring postoperative changes. The purpose of this study was to determine if the SF-12 could safely substitute for the SF-36 in measuring postoperative change in lumbar spine surgery patients and if the condition specific (Oswestry Disability Index [ODI]) or pain (visual analog scale [VAS]) instruments, provided additional utility.
A total of 972 patients from a single center who underwent lumbar spine surgery for a predominant symptom of radiating leg pain with (n = 237) or without (n = 735) fusion and prospectively completed both SF-36 and ODI instruments before and after surgery were included. The SF-12 score was calculated from the appropriate subset of SF-36 responses. The absolute sensitivity and the intraclass correlation coefficient were calculated. Reliability of each instrument to measure preoperative to postoperative change was calculated as the standardized response mean.
The SF-12 and SF-36 demonstrated a strong correlation with each other ([0.97, P < .001] and [0.93, P < .001], respectively) preoperatively and postoperatively. The SF-12 and SF-36 scores were moderately to strongly inversely correlated with the ODI. The ODI showed greater reliability at measuring change than the SF-12 for both fusion (0.94 versus 0.72) and nonfusion (0.81 versus 0.33) lumbar surgery patients.
The SF-12 was as effective as the SF-36 to measure general health status in lumbar spine surgery patients, and both were moderate to strong predictors of ODI preoperatively and postoperatively, but lack the reliability to detect change seen with the ODI or VAS after surgical intervention.
Level of evidence:
These data suggest that the SF-12 is a valid substitute for the SF-36 to measure postoperative outcomes changes, but that the ODI should continue to be used to measure condition specific changes in function.
Oswestry Disability Index; SF-12; SF-36; health status; lumbar spine surgery; patient reported outcomes; quality of life; visual analog scale.