Table 3.
Step 1. Baseline variables associated with working or not at follow-up in the surgical and nonsurgical groups
| Surgery and rehabilitation (n = 154) | |||
|---|---|---|---|
| N (yes/no) | % patients working categorized by yes/no | P value | |
| Physical variables | |||
| Daily consumption of narcotics | 34/120 | 56/60 | 0.67† |
| Prior surgery | 42/112 | 55/61 | 0.50† |
| Level | |||
| L4/L5 | 32/122 | 69/57 | 0.41† |
| L5/S1 | 81/73 | 58/60 | |
| L4/L5 and L5/S1 | 41/113 | 54/61 | |
| Comorbidity | 31/123 | 48/62 | 0.18† |
| ODI | 0.02* | ||
| Duration of back pain (months) | 0.97‡ | ||
| Body mass index | 0.25* | ||
| Sociodemographic variables | |||
| Socioeconomic status | |||
| Manual workera | 58/86 | 51/63 | 0.15† |
| Educational level (%) | |||
| Primary school (9 years) | 32/122 | 47/62 | 0.20† |
| High school (12 years) | 93/61 | 60/57 | |
| University/collegeb | 29/125 | 69/57 | |
| Workingc | 35/119 | 87/50 | <0.001† |
| Duration out of work | |||
| <6 months | 43/97 | 79/54 | 0.009† |
| 6 months–1 year | 38/102 | 61/62 | |
| >1 year | 59/81 | 49/70 | |
| Sex (female) | 80/74 | 59/60 | 0.93† |
| Current smoker (%) | 71/82 | 55/62 | 0.36† |
| Age | 0.53* | ||
| Psychological variables and pain | |||
| HSCL | 0.52* | ||
| FABQ–work | 0.001* | ||
| FABQ–physical | 0.88* | ||
| MCS (SF-36) | 0.25* | ||
| Back pain (VAS) | 0.50* | ||
| Pain drawing (below belt)d | 111/30 | 59/67 | 0.42† |
| Radiological variables | |||
| Modic I and II | |||
| Not present | 21/131 | 52/62 | 0.76† |
| Modic primary type I present | 48/104 | 65/56 | |
| Modic primary type II present | 55/97 | 56/60 | |
| Modic I and II present | 28/124 | 57/59 | |
| Modic CCe | 55/97 | 69/53 | 0.05† |
| Disc height reductionf | 104/48 | 61/54 | 0.46† |
| Nucleus pulposus grade 3/4 | 133/19 | 58/63 | 0.66† |
| Facet joint arthropathy grade 2/3 | 14/138 | 64/58 | 0.65† |
| Posterior HIZ | 63/89 | 54/62 | 0.33† |
Continuous and categorical variables
SF-36 scores range from 0 to 100, with higher scores corresponding to better health status
Waddell’s FABQ scale ranges from 0 to 24 (physical) and from 0 to 42 (work), with lower scores indicating less severe symptoms
HSCL-25 = Hopkins Symptom checklist; HSCL-25 reflects emotional distress, and scores range from 1 to 4, with lower scores indicating less severe symptoms
P value; Indicating if the baseline variable is associated with working or not at follow-up
FABQ Fear of Avoidance Belief Questionnaire
* Independent two-sided t test; †Pearson’s χ2; ‡Mann–Whitney U test; ¶Fischer’s exact test
aClassified according to socioeconomic status from Statistics Norway consisting of six groups: manual low, manual high, routine nonmanual low, routine nonmanual high, professional low or professional high. Because there were few patients in each group, unskilled and skilled workers were merged into the same group and nonmanual in one group. Consequently, two groups were analyzed, manual and nonmanual[14]
bBecause there were fewer than five subjects in the category of education at university level, they were merged with 13-15 years of education (college)
cWorking versus not working;Including part-time work as working
dUden et al. [19]
eMore than 50% of the craniocaudal diameter
fMore or less than 40% height reduction (more = yes)
The Oswestry Disability Index (ODI) ranges from 0 to 100, with lower scores indicating less severe symptoms
Back pain was calculated using a horizontal scale ranging from 0 (no pain) to 100 (worst pain imaginable) with word anchors at the beginning and end