The study was a cluster-randomised controlled trial, conducted with a stepped-wedge cohort design (Additional file 1, Figure A) in six Norwegian municipalities between January 2015 and October 2017. The study involved general practitioners (GPs), physiotherapists (PTs) and patients with symptomatic hip and knee OA.
The study protocol, with an elaborate explanation of the study design and primary outcome (patient-reported quality of care), has been published previously (14). A separate paper reporting the primary outcome has is recently published (15), and a paper regarding uptake and implementation fidelity of the study intervention among health professionals and patients is published (16). The study is reported according to the CONSORT checklist (Additional file 2).
According to the stepped-wedge design the six municipalities (clusters) were randomly assigned to one of the six sequences for time of cross-over from control to intervention phase using a computer-generated list of random numbers provided by a statistician. Due to the nature of the intervention, it was not possible to blind the involved GPs, PTs or patients.
Patient-reported outcomes were collected at baseline at 3 and 6 month’s follow-up, using electronic questionnaires.
All GPs and all PTs working in private practice or in a Healthy Life Centre in the six municipalities were invited to participate in the study. Potential patients eligible for the study were identified by their GP or PT with the following inclusion criteria: age ≥45 years with symptomatic hip and/or knee OA, verified clinically or radiologically. Patients who did not understand the Norwegian language; had undergone joint replacement for all hip/knee OA joints; or had inflammatory rheumatic diseases, malignant illness or other major conditions that restricted their ability to adhere to the treatment recommendations were excluded.
The SAMBA model for integrated OA care (Additional file, Figure B) was developed by the research team and included a structured pathway for the patient through the health care system. The model should provide the patient with access to timely recommended care.
Interactive workshops for GPs and PTs were the main activity to ensure implementation of the SAMBA model in clinical practice. The workshops were arranged separately for each municipality, in close proximity to the time for crossover from control to intervention phase. During the workshops, the PTs received education in the delivery of the standardized patient-education programme and of the individually tailored exercise programme. The PTs received access to a database with recommended exercises and dose recommendations. The exercises were selected from the exercise programmes of the Swedish BOA and Danish GLA:D OA management programmes and previously published exercise programmes for hip and knee OA (14, 17, 18).
The group-based patient education programme lasted 3 hours and was based on a standardized template (Power-Point with optional manuscript). The patient education focused on providing the patient with knowledge of OA and recommend treatments, emphasizing the importance of exercise.
Following individual patient examinations, the PTs prescribed individually tailored exercise programmes with the main aim to improve muscular strength, in order to reduce OA symptoms. The PTs were instructed to closely monitor the individual patients’ performance and to regularly adjust exercise dose and degree of difficulty to facilitate progression. Dose recommendations were based on acknowledged, international guidelines from American College of Sports Medicine (ACSM), and included gradually increasing the dose towards 2-4 sets with 8-12 repetitions of 60 % - 70 % of 1 repetition maximum or more if tolerated (19). The PTs were instructed to increase the resistance when the patient could perform 2 extra repetitions in the last set (“The 2+ principle”).
The patients performed their individual exercise programmes in groups of 5-10 patients per PT. The exercise period lasted 8 -12 weeks, with two supervised weekly sessions. The patients were encouraged to add a third home-based session consisting of 30-60 min cardiorespiratory exercise like brisk walking, running or bicycling. Patients who did not wish to attend the group sessions had the option of performing their exercise individually, but were expected to consult their PT for regular adjustments of the programme.
During the control phase, the GPs and PTs provided usual care for their OA patients. Usual care could include physiotherapy, but not provided by a PT who had participated in the workshops.
Patient-reported pain, physical function and patient global assessment of disease activity during the last week were evaluated using 11-point Numeric Rating Scales (NRS) (0=best, 10=worst). The scores from these outcomes were used to calculate the proportion of OMERACT-OARSI responders (20) (in the two groups) at 3 and 6 months. A participant was classified as a responder if one of the following were fulfilled:
1) High improvement in pain or function
- ≥50 % improvement + absolute change of ≥2 in pain, OR
- ≥50 % improvement + absolute change of ≥2 in function
2) Improvement in at least two of the three following:
- ≥20 % improvement + absolute change ≥1 in pain
- ≥20 % improvement + absolute change ≥1 in function
- ≥20 % improvement + absolute change ≥1 in the patient global assessment of disease activity
Participants with missing data were regarded as non-responders for these analyses.
A participant was characterized as having completed the exercise programme if having exercised for ≥ 2 times per week for ≥ 8 weeks. The information on the number of completed exercise sessions was derived from participants’ exercise diaries and attendance lists from the PTs if exercise diaries were not returned or incomplete.
Sample size calculations were not conducted for secondary outcomes of the study. For the main outcome, it was calculated a need for a total of 388 participants (14).
Patients receiving joint replacement surgery between baseline and 6 months were excluded from current analyses as these patients no longer fulfilled the diagnostic inclusion criteria for the study. Secondly, such intervention may have a large impact on patient-reported outcomes such as pain and physical function.
Descriptive analyses were conducted for baseline, 3 and 6 months characteristics.
The difference in pain, function, disease activity and proportion of OMERACT-OARSI responders between the intervention and control group were investigated using two-level mixed regression models with random effects for cluster and individual participant and fixed effects for age, gender, BMI and time trends (month of inclusion). The linear models for pain, function and disease activity included an interaction term of follow-up time point and group. The difference in OMERACT-OARSI responders was investigated using a logistic model. The proportion of responders was investigated separately for 3 and 6 months and for these time-points combined.
In the intervention group, the difference in the proportion of responders between the participants completing the exercise programme (exercise for ≥ 2 times per week for ≥ 8 weeks) and the non-completers were compared using descriptive statistics.
To investigate potential associations between completing the exercise programme and baseline characteristics a two-level mixed logistic regression was fitted. The model included random effects for cluster and individual participant. The set of baseline characteristics (fixed effects) were selected based on experience and previous literature of variables suggested to have an impact on exercise adherence. The variables were age, gender, BMI, smoking (yes/no), education (<1 / ≥ 1year of university), employment (yes/no), cohabitation (yes/no), multisite OA (yes/no), pain last week (NRS 0-10) and self-efficacy (Arthritis Self-Efficacy Scale (ASES) mean score of Pain and Function subscales (10-100, “very uncertain” to “certain”))(21). The variables were first investigated independently for associations with the dependent variable. Variables with p <0.2 in crude associations were included in the adjusted model. The final model was additionally adjusted for time trends (month of inclusion), investigated for possible multicollinearity and the goodness of fit using Hosmer and Lemeshow test.
The significance level for the analyses was set at p <0.05.
Patient and public involvement
Two patient research partners were members of the trial steering group and involved in all stages of this trial including grant application, development of study material (patient information, consent procedures, questionnaires), intervention, interpretation and dissemination of the results.