Table 2 Outcome measures at baseline and 6 months after surgery of patients receiving standard medical care (SMC), Supportive Intervention (SUPPORT) or Expectation Manipulation Intervention (EXPECT) (observed means)

 Baseline

22.78 (18.36–27.19)

22.14 (17.04–27.23)

25.89 (20.81–30.97)

F(2, 102.542) = 4.762;

B, C

 Follow-up

20.79 (15.35–26.23)

15.23 (10.82–19.65)

12.19 (8.50–15.89)

P = 0.011

 Baseline

48.96 (45.71–52.20)

51.60 (48.56–54.63)

47.98 (43.66–52.31)

F(2, 94.803) = 4.627;

C

 Follow-up

50.58 (47.02–54.14)

52.40 (48.83–55.97)

56.74 (54.29–59.19)

P = 0.012

 Baseline

40.26 (36.80–43.73)

39.55 (35.82–43.29)

37.15 (34.04–40.26)

F(2, 103.928) = 3.186;

B, C

 Follow-up

40.28 (36.58–43.98)

45.21 (41.23–49.19)

44.77 (41.13–48.41)

P = 0.045

Patient subjective working ability in hours per week follow-up

15.97 (10.50–21.43)

17.14 (10.45–23.80)

25.40 (19.90–30.90)

F(2, 74) = 3.325; P = 0.041^a

AC^a, BC^a

 Baseline

2668.40 (1919.56–3417.24)

2635.54 (1547.50–3723.57)

2433.63 (1249.51–3617.75)

F(2, 72.915) = 4.776;

B, C

 Follow-up

2957.64 (2128.50–3786.78)

5388.21 (3618.71–7157.71)

4700.60 (3470.76–5930.45)

P = 0.011

 Baseline (pre-intervention)

2.48 (2.29–2.67)

2.68 (2.47–2.90)

2.67 (2.44–2.89)

F(2, 107.021) = 3.980;

B, C

 Follow-up (after 6 months)

2.50 (2.31–2.69)

2.34 (2.11–2.57)

2.29 (2.11–2.47)

P = 0.022

 Baseline (pre-intervention)

4.03 (3.07–4.98)

4.55 (3.42–5.67)

5.17 (3.47–6.86)

F(2,102.409) = 1.325;

 Follow-up (after 6 months)

3.24 (2.42–4.05)

2.52 (1.52–3.51)

3.61 (2.22–4.99)

P = 0.270

 Baseline (pre-intervention)

4.59 (3.60–5.58)

4.00 (2.89–5.11)

5.11 (3.75–6.47)

F(2, 99.211) = 2.604;

 Follow-up (after 6 months)

3.68 (2.62–4.75)

1.88 (1.20–2.57)

2.58 (1.60–3.56)

P = 0.079

 Baseline (pre-intervention)

12.05 (11.49–12.62)

12.61 (12.10–13.12)

12.37 (11.90–12.83)

F(2, 98.882) = 0.084; P = 0.919

 Post psychological intervention

11.94 (11.32–12.56)

12.29 (11.97–12.60)

12.09 (11.52–12.66)

 Baseline (pre-intervention)

15.28 (14.74–15.81)

15.24 (14.55–15.92)

14.03 (12.90–15.16)

F(2, 103.971) = 8.748; P < 0.001

C

 Post psychological intervention

15.16 (14.43–15.88)

14.91 (14.13–15.68)

16.06 (15.40–16.73)

 Follow-up

9 (26.47)

7 (23.33)

3 (9.38)

χ ² (2) = 3.380; P = 0.185

  ≥ 50

25 (80.6)

23 (88.5)

24 (100)

χ ² (2) = 5.138; P = 0.077

 49–30

6 (19.4)

3 (11.5)

0 (0)

  < 30

0 (0)

0 (0)

0 (0)

 Baseline (pre-intervention)

3.71 (2.14–5.27)

2.10 (1.34–2.86)

3.58 (1.91–5.25)

F = (6, 216.924) =2.523; P = 0.022

Follow-up: AC

 Post psychological intervention

3.06 (2.03–4.10)

1.83 (1.44–2.22)

3.44 (2.07–4.82)

 After surgery

24.75 (18.61–30.89)

19.56 (13.63–25.49)

19.90 (15.63–24.18)

 Follow-up (after 6 months)

4.83 (2.99–6.68)

3.66 (2.16–5.16)

2.39 (1.38–3.41)

 Baseline (pre-intervention)

5.48 (4.05–6.90)

5.56 (4.33–6.79)

5.78 (4.18–7.38)

F = (6, 206.632) = 4.186; P = 0.001

Post-surgery: AB, AC

 Post psychological intervention

4.76 (3.86–5.66)

5.13 (3.89–6.38)

5.52 (3.73–7.30)

 After surgery

13.71 (11.44–15.97)

10.31 (8.14–12.48)

11.02 (8.64–13.40)

 Follow-up (after 6 months)

5.08 (3.63–6.52)

4.83 (4.22–5.45)

6.07 (4.76–7.37)

 Baseline (pre-intervention)

2.01 (1.60–2.42)

1.48 (1.19–1.76)

1.61 (1.39–1.83)

F(6, 174.813) = 1.404; P = 0.216

 Post psychological intervention

2.20 (1.78–2.62)

1.54 (1.32–1.76)

1.72 (1.43–2.01)

 After surgery

3.63 (2.72–4.54)

2.17 (1.81–2.52)

3.12 (2.51–3.72)

 Follow-up (after 6 months)

2.66 (2.00–3.32)

1.72 (1.48–1.96)

2.09 (1.70–2.49)

 Baseline (pre-intervention)

2.49 (1.84–3.15)

2.23 (1.32–3.15)

2.96 (2.00–3.92)

F(6, 209.520) = 1.410; P = 0.212

 Post psychological intervention

2.22 (1.62–2.81)

2.19 (1.52–2.86)

3.42 (2.07–4.76)

 After surgery

123.93 (94.24–153.62)

101.71 (77.65–125.76)

96.14 (76.91–115.38)

 Follow-up (after 6 months)

4.23 (2.05–6.42)

4.17 (1.96–6.38)

2.33 (1.54–3.12)