This cross-sectional study involved 132 patients with chronic nonspecific low back pain and was approved by the ethics committee of the xxxxxxxxxxxxxx (Protocol XXXXX). We contacted the participants using study flyers, newspaper advertisements, and a list of patients with low back pain at the Specialized Rehabilitation Center. All the participants were confirmed as having chronic nonspecific low back pain, as diagnosed by an orthopedist through a detailed evaluation and imaging (x-ray), to exclude associated diseases. After the evaluation by a physician, the participants were contacted the patients by phone and invited to participate in the study. Participants gave their informed consent before participation. A blind evaluator, a physiotherapist who was trained to evaluate kinesiophobia, pain intensity, functional disability, quality of pain and quality of life, assessed the participants.
The inclusion criteria were: nonspecific chronic low back pain for more than 3 months, an age between 18 and 65 years old, and a minimum pain intensity score of 3 on the Numerical Rating Scale (NRS) [15]. Subjects who had any history of malignancy or spinal fracture, had undergone any surgical procedure in the previous 6 months, had orthopedic or neurological diseases affecting ambulation, or did not understand written and spoken Portuguese were excluded from the study. All the instruments used to assess the outcome measures had previously been translated and adapted to Brazilian-Portuguese versions, and had adequate psychometrical properties [16,17,18,19,20].
Kinesiophobia was assessed using the Tampa Scale of Kinesiophobia, which it was developed to measure the fear of movement due to chronic low back pain. It is a self-report questionnaire of 17 items, and it was used to assess the kinesiophobia of the subjects. Each question has four response options (strongly disagree, disagree, agree, or strongly agree) with scores ranging from 1 to 4 points, respectively. The total score is calculated after inversion of the individual scores of items 4, 8, 12, and 16. The total score ranges between 17 and 68. Increased scores reflect an increased fear of movement [18]. Vlaeyen et al. defined a cut off score of 37 as a high degree of kinesiophobia [21].
Pain intensity was assessed using the numeric pain rating scale (NPRS). This is an 11-point numeric pain scale, ranging from 0 to 10, on which 0 indicates “no pain” and 10 the “worst possible pain” at the time of the assessment [22].
Quality of pain was assessed using the McGill Pain Questionnaire, a multidimensional assessment of pain. It consists of 77 descriptors of the quantity and quality of pain, grouped into four major domains: sensory, affective, evaluative, and miscellaneous. The domains have 20 sub-domains represented by words that qualify the feelings of pain of a subject, for which intensity values, on a scale of 1 to 5, are assigned. The questionnaire is used to describe the pain experienced by a subjects and the score is the sum of the aggregate values. Maximum scores for each domain are: sensory = 41, affective = 14, evaluative = 5, and miscellaneous = 17, with a total possible score of = 77. The index of the pain assessment of each domain is the sum of the scores of the sub-domains, and each option chosen in domain in questionnaire for represented the pain was the maximum score for each category [17].
Quality of life was assessed using the Short Form Health Survey Questionnaire SF36 to assess health related qualify of life. The Sf36 consists of 36 questions, grouped in eight domains: vitality (4 items), physical functioning (10 items), bodily pain (2 items), general health (5 items), physical role limitation (2 items), emotional role limitation (3 items), social functioning (2 items), and mental health (5 items). For each section, the score ranges from 0 to 100, and higher scores reflect better quality of life. In is study, the focus was on the physical and emotional role limitation domains [19].
For disability, the Roland Morris Disability Questionnaire was used to assess functional disability due to low back pain. This questionnaire consists of 24 questions that focus on regular activities in daily living. Each affirmative answer is awarded 1 point and the final score is determined as the total number of points. Total scores range from 0 to 24, with higher scores reflecting increased disability. Scores above 14 indicate severe impairment [16].
All analyses were conducted using SPSS version 22.0 (IBM Corporation, USA). One-way fixed effects analysis of variance (ANOVA) was used. A statistical power of 80% (1 β error probability) with an α error level probability of 0.05 was chosen to detect between-group differences in the primary outcome measures. A medium effect size of 0.35 was used. Thus, it was estimated the study needed a minimum number of 132 subjects.
In statistical analysis, mean ± standard deviation (SD) values were calculated for the quantitative variables and percentages were calculated for qualitative variables. Pearson correlation coefficients and a multiple linear regression model were used to analyze of the associations of the clinical variables (pain intensity, disability, quality of life and pain duration) with kinesiophobia. The following indices were used to rank the correlations: < 0.49 = low; 0.50–0.69 = good; > 0.7 = excellent [23]. Significance was accepted for values of p ≤ 0.05.
