Table 7: Adjusted* mean change in outcome from immediately preoperatively to 6, 12 and 24 months postoperatively for the 2 wait time groups
Time point; outcome measureWait time; mean change in score (SE)†Mean difference in change (95% CI)
Shorter ( 12 mo)Longer (> 12 mo)
6 mo
SF-36 PC summary score12.3 (1.6)10.1 (1.7)2.2 (-1.6 to 6.0)
SF-36 MC summary score11.1 (1.8)6.6 (1.8)4.5 (0.3 to 8.7)
ODI score-26.8 (2.7)-18.2 (2.7)-8.5 (-14.7 to -2.4)
ZCQ score-1.6 (0.2)-1.3 (0.2)-0.3 (-0.6 to 0.05)
Back pain score-5.0 (0.6)-4.7 (0.6)-0.4 (-1.6 to 0.8)
Leg pain score-6.2 (0.6)-4.9 (0.6)-1.4 (-2.6 to -0.1)
12 mo
SF-36 PC summary score12.5 (1.6)12.0 (1.8)0.6 (-3.3 to 4.5)
SF-36 MC summary score11.1 (1.8)5.6 (1.9)5.7 (1.4 to 9.9)
ODI score-30.2 (2.5)-20.8 (2.5)-9.3 (-15.1 to -3.6)
ZCQ score-1.6 (0.2)-1.5 (0.2)-0.2 (-0.5 to 0.2)
Back pain score-4.9 (0.6)-4.3 (0.7)-0.5 (-1.9 to 0.7)
Leg pain score-6.8 (0.6)-5.2 (0.7)-1.6 (-3.0 to -0.3)
24 mo
SF-36 PC summary score10.6 (1.7)11.2 (1.9)-0.7 (-4.8 to 3.3)
SF-36 MC summary score9.6 (1.8)5.9 (1.9)3.7 (-0.6 to 8.0)
ODI score-27.1 (2.4)-22.2 (2.6)-4.9 (-10.6 to 0.9)
ZCQ score-1.4 (0.2)-1.2 (0.2)-0.2 (-0.6 to 0.1)
Back pain score-5.1 (0.7)-4.5 (0.7)-0.6 (-1.9 to 0.8)
Leg pain score-6.1 (0.6)-4.9 (0.6)-1.1 (-2.3 to 0.1)

Note: CI = confidence interval, MC = mental component, ODI = Oswestry Disability Index, PC = physical component, SE = standard error, SF-36 = 36-Item Short-Form Health Survey, ZCQ = symptom severity scale of the Zurich Claudication Questionnaire.

*Adjusted for baseline score, age, surgeon, duration of symptoms and surgery type.

†For SF-36 PC summary score and MC summary score, a positive change indicates improvement. For ODI score, ZCQ score, back pain score and leg pain score, a negative change indicates improvement.