Data collection and clinical setting
We included all patients with LBP admitted to a medical unit at the Winterthur Cantonal Hospital during a 12-month period (February 1st, 2019 until January 31st, 2020). Winterthur Cantonal Hospital is a public acute care hospital with over 28000 inpatient visits a year. In 2019, medical units had 8216 inpatients .
We identified patients with LBP admitted to medical units on the screening list. All patients received paper-pencil questionnaires for assessing health-related personal data at the initial physiotherapy consultation. We asked patients to complete the questionnaire and to sign the informed consent document concerning the use of health-related personal data for research purposes. Patients returned the completed questionnaires to the physiotherapist.
We used two patient samples in this study (see Figure 1). To analyse the effect of the weekday of admission on LoS (Part 1), we extracted data from the hospital electronic medical records by using patient identification numbers. To record diagnoses related to specific causes of LBP (‘red flags’ pathologies), we investigated medical records as well. As specific causes of LBP we coded cancer, infection, trauma or inflammatory disease such as spondylarthritis . To analyse the influence of the weekday of admission and patient-reported distress on LoS (Part 2), we only used data of patients having signed the consent document. We did not include patients hospitalized more than one month. In these cases, we assumed that significant complications occurred for reasons that cannot be explained by the initial LBP problem. The further use of routine health-related person data for this study was approved by the Kantonale Ethikkomission Zürich (KEK ZH: 2020-01465). All analyses were performed in accordance with guidelines and regulations from this regional ethics committee.
Low back pain management at general medicine units
Patients with LBP admitted to medical units at Winterthur Cantonal Hospital receive care according to the clinical LBP pathway aiming to facilitate a patient-centred interdisciplinary approach (medicine, physiotherapy and nursing). The pathway requires that a specialised physiotherapist assesses all patients. Physiotherapy is scheduled on the second day of hospitalisation. Immediately after the first physiotherapy session, a consultation between the physiotherapist and the physician in charge should take place. This formal meeting focuses on the diagnosis, further inpatient procedure, and discharge management.
The general aim of the interdisciplinary approach is to achieve a mutual understanding of the pain problem and to set common goals together with the patient. This interdisciplinary procedure cannot be provided during the weekend. For admissions on Friday afternoon, Saturday and Sunday, the physiotherapy assessment and the interdisciplinary meeting are postponed to Monday. On weekends, specialised physiotherapy assessments are not provided.
The physiotherapy assessment (60 minutes) is focused on hearing the full patient story regarding the cognitive and emotional experience of the pain problem. Physiotherapists aim to explore patients’ beliefs, emotions, and stress responses associated with their current pain problem as well as their strategies for coping with pain and stress. Furthermore, the assessment addresses fear-related movements or avoidance behaviour. This functional analysis aims to identify maladaptive movements or postures including extensive protective muscle activation or dysfunctional pain behaviour. In a collaborative process with the patient, physiotherapists explore patients’ ability to relax trunk muscles and to normalise pain provocative postural and movement behaviours. Physiotherapists and physicians screen for specific causes of LBP (‘red flags’ pathologies).
Physicians are responsible for inpatient management, clinical diagnosis, diagnostic imaging, pharmacological treatment or interventional measures (e.g. surgical procedures). Attending physicians and nurses see patients daily during medical rounds focussing on diagnosis, therapeutic procedures, and discharge management. Physiotherapists do not routinely take part in these rounds. However, information from the physiotherapy assessment is incorporated into the communication between the patient and health care professionals.
Health-related personal data
We used the numeric rating scale (NRS, scale: 0-10) to measure average pain intensity over the last week. By means of the German version of the Roland Morris Disability Questionnaire (scale: 0-24), we measured back-specific function . To evaluate patient-reported psychological distress, we used the distress scale of the German Four-Dimensional Symptom Questionnaire (4DSQ). The 4DSQ proved to be a valid self-report questionnaire to measure distress, depression, anxiety and somatisation in patients treated in primary care . The German version of the 4DSQ has previously been validated in a sample of multimorbid elderly people . The questionnaire addresses the presence of symptoms during the last two weeks. Psychological distress was conceptualized as direct manifestation of the effort people must exert to maintain their psychosocial homeostasis and social functioning when confronted with taxing life stress [18, 20]. In the four-dimensional model of the 4DSQ, distress is conceptualized as the most basic, most general or “normal” expression of psychological problems . Higher scores on 4DSQ scales represent higher symptom severity.
To compare overall mean LoS in patients with and without LBP, we performed an independent t-test. For the analysis in Part 1, we used a linear model for LoS (dependent variable) with weekday of admission as predictor. If there was evidence against model assumptions after residual analysis, we conducted a Box-Cox power transformation. Based on the ANOVA, we used planned contrast to test the hypothesized difference in mean effects of the weekday of admission dichotomy (Friday/Saturday versus Sunday-Thursday) on LoS. For Part 2, a linear model was fitted for LoS (dependent variable) with continuous patient-reported distress (4DSQ distress scale), categorical weekday of admission (Friday/Saturday vs. Sunday-Thursday), and their interactions as covariates. From the fitted model coefficients, we constructed the planned contrast of interest, the difference in mean distress trend (slope) for Friday/Saturday versus mean distress trend for Sunday-Thursday. This contrast represents the modification of distress effect on LoS by day dichotomy (Friday/Saturday versus Sunday-Thursday). The level of statistical significance was set at 0.05. We performed all analyses by using R statistical software .