Study Design
An observational prospective cohort study, with assessments at the beginning of treatment and at discharge, was conducted at the day clinic in the Department of Physical Medicine and Rehabilitation at University Hospital, LMU Munich, Germany. The study was carried out in compliance with the Helsinki Declaration 2004. All participants provided signed informed consent prior to study participation. At the time of data collection, ethical approval was not mandatory for observational studies not affecting treatment and not requiring additional clinical tests (i.e. naturalistic design).
Participants
Patients were referred by their family physician or a specialist to an interdisciplinary assessment that was conducted by a specialist in Physical and Rehabilitation Medizine (PRM), a physiotherapist, and an occupational therapist. In addition, a psychologist on the treatment team assessed patients who were suspected of a mental health disorder.
At the end of the assessment, the treatment team either recommended participation in a three-week MBR programme or other treatment options. The treatment team recommended MBR according to predefined inclusion criteria, appraisal of results of standardised clinical tests and standardised patient questionnaires, and the global impression of the day clinic treatment team. The predefined inclusion criteria were CNP (pain lasting at least three months, with or without pain irradiation in the upper limbs), previous outpatient physical therapy that was not providing relevant improvements according to oral questioning of the patient, limitations of activities and participation, and sufficient skills of the German language to follow the instructions of the MBR. MBR was not recommended if patients had severe somatic or mental illness limiting the ability to participate in the MBR (e.g. major depression), acute neck trauma in the past three months, former whiplash injury with proven structural damage, new neurological deficits in the last three months, chronic neurological deficits that prevent participation in exercise interventions, unclear dizziness or vertigo, diffuse idiopathic skeletal hyperostosis (DISH), reduced mobility of shoulder abduction or flexion less than 90°, or an ongoing pension process.
After meeting with the treatment team, the physician explained the recommendation to each patient. In conversation, patients expressed their expectations and goals for treatment and their treatment preferences. Within the framework of participatory decision-making, the recommendation could change. More details about the assessment have been described elsewhere (12).
All consecutive patients who participated in the MBR, provided informed consent, and had analysable North American Spine Society questionnaire (NASS) pain + disability scales (16, 17) at baseline and discharge were included in the study.
Data Collection
At the beginning and the end of the MBR programme, patients completed a set of standardised patient questionnaires and were evaluated by standardised clinical tests according to a written protocol. The analyses in this study used the results of the NASS questionnaire (16, 17), the mental health scale from the Short Form 36 (SF-36) questionnaire, (18) the standardised comorbidity questionnaire (19), sociodemographic questions, and the results of a measure of cervical spine range of motion (ROM) with the cervical range of motion instrument (CROM) (20).
Study Intervention
Patients completed a three-week MBR programme, with a total of nine treatment days and 44 treatment hours. The treatment team consisted of a specialist in PRM, physiotherapists, occupational therapists, psychologists, medical massage therapists, and a swimming trainer. Most treatments were provided in groups, but all participants had two individual physiotherapy lessons occurring at the beginning and the end of the programme. In the initial individual physiotherapy lesson, patients were trained in deep neck muscle strengthening exercises using biofeedback (21). In the final individual lesson, patients were instructed in individual home exercises. Treatments were provided in groups, with up to five participants in practical lessons and up to 10 participants in educational lessons and pool therapy. The MBR included land-based group exercises, gym training, pool exercises, occupational training, psychological lessons (including learning relaxation strategies), instructions for self-help techniques, patient education by a PRM specialist, and interactive group discussions at the end of each week with the complete treatment team. The physician provided daily ward rounds in the group and individual appointments on demand. Details of the intervention have been described elsewhere (12).
Measures
North American Spine Society questionnaire (NASS) (16, 17)
The NASS is a condition-specific instrument with specific modules for neck pain and low back pain that measure pain, disability, and neurogenic symptoms. In the primary validated version of the neck-pain-specific version, 10 items constitute the pain + disability scale and eight items make up the neurogenic symptom scale. A subsequent validation study revealed a three-factor structure in which the pain + disability scale is separated into a pain scale (two items) and a disability scale (eight items) (22, 23). The scales range from 1 (best health) to 6 (worst health).
Short Form 36 (SF-36) Mental Health (18)
The mental health scale is one of eight scales from the generic health status measure SF-36. It consists of five items and ranges from 0 (worst health) to 100 (best health). A recent review showed associations between changes of the SF-36 mental health scale and the course of pain in different chronic pain conditions (24).
Cervical Range of Motion instrument (CROM) (20)
The CROM (Performance Attainment Associates, 3600 Labore Road, Suite 6, St. Paul, MN 55110 − 4144) measures cervical spine ROM in degrees in six directions of movement: flexion, extension, lateral flexion, rotation, as well as suboccipital flexion and extension. The total active cervical ROM was calculated as the sum of the ROM in all six directions.
Sociodemographic data and comorbidities
Sociodemographic data were collected through specific questions and comorbidities in the Self-Administered Comorbidity Questionnaire (SCQ) (19).
Analyses
Descriptive statistics, treatment effects
Descriptive statistics were calculated for baseline characteristics. Effect sizes (ES) for the primary outcome of NASS pain + disability and the secondary outcomes (NASS pain, NASS disability, SF-36 mental health, and total active cervical ROM) were determined by dividing the mean change between baseline and discharge by the standard deviation of the baseline score (25). ES over 0.30 are generally considered clinically meaningful unless instrument-specific studies have provided more reliable results for the minimal clinically important effects (26). Significance of changes were tested by t-tests for dependent samples of symmetrically or normally distributed data or by Wilcoxon signed-rank tests for not symmetrically distributed data.
Multivariate regression
The primary dependent variable in linear regression models was the change score of the NASS pain + disability scale (12). In further linear regression modelling, the separated NASS pain scale and NASS disability scale were dependent variables.
Independent variables were selected from the collected variables to cover the International Classification of Functioning, Disability and Health (ICF) components function (physical function and mental function), activity and participation, and personal factors (27). A further criterion for co-variate selection was the presence of associations with treatment outcomes in previous predictor studies of musculoskeletal health conditions (14, 15, 28). Furthermore, range of motion was added as a co-variate because improvement of range of motion was a treatment goal (12), and previous studies showed an association of cervical spine ROM to pain and disability (29). The total number of co-variates was limited to 10, as 10 cases per co-variate are needed for finite models and sufficiently valid estimates of the regression coefficient (30).
The independent variables were sex, age, living with a partner, education level, number of comorbidities, SF-36 mental health baseline, SF-36 mental health mean change, total active cervical ROM, and change of total active ROM. In addition, all models were adjusted for the baseline score of the corresponding NASS scale, of which the change in score was the dependent variable. In order to adjust for any confounding, all listed co-variates were kept in the models, irrespective of whether their correlation was statistically significant or not. Multivariate partial correlations were thus determined and adjusted for all other included potentially confounding co-variates (31). The overall explained variances (%) were calculated to quantify the fit of the regression models.
For missing values of single co-variates, the mean imputation method was used (i.e. missing values were replaced by the mean of the valid values within each independent variable). We assumed missing values were due to random processes. This assumption is supported by 97% completeness of the SF-36 mental health scale at baseline and 98% at follow-up, despite patients generally regarding questions about mental health as more sensitive compared to questions about physical health. The frequency of missing values in the other co-variates ranged from 0% (sex, age, baseline scores of the NASS scales) to a maximum of 14% (education).
Statistical analyses were calculated using SPPS 25.0 for Windows. ES were calculated with Microsoft Excel 2010.