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Lluch E.1,2, Dueñas L.1, Aguilar-Rodríguez M.1, Torres-Cueco R.1, Navarro S.3,4, Struyf F.5, Meeus M.6,7
1University of Valencia, Department of Physical Therapy, Valencia, Spain, 2Faculty of Physical Education & Physiotherapy, Vrije Universiteit Brussel, Departments of Human Physiology and Rehabilitation Sciences, Brussel, Belgium, 3University of Málaga, Department of Physical Therapy, Málaga, Spain, 4Faculty of Medicine and Health Sciences, University of Antwerp, Department of Rehabilitation Sciences and Physiotherapy, Antwerp, Belgium, 5Faculty of Medicine and Health Sciences, University of Antwerp, Department of Rehabilitation Sciences and Physiotherapy, Antwerpen, Belgium, 6Faculty of Medicine and Health Sciences, University of Antwerp, Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health Sciences, Antwerpen, Belgium, 7Faculty of Medicine and Health Sciences, Ghent University, Department of Rehabilitation Sciences and Physiotherapy, Ghent, Belgium
Background: Frozen shoulder (FS) is a poorly understood condition resulting in substantial pain, large mobility deficits and considerable morbidity. Current physical therapy interventions for FS are mainly focused on the shoulder with demonstrated positive effects in terms of pain reduction and mobility improvement. However, there is no evidence for altering the disease progression thus raising the need for innovative research in the area of FS.
Continuously increasing nociceptive inputs, especially in the early stages of FS, could lead to long-lasting central sensitization (CS). However, the involvement of CS in FS has not been studied yet and remains speculative. In addition, the role of maladaptive psychosocial factors, which are important therapy mediators/barriers in other chronic pain conditions, is unknown. Similarly, the influence of metabolic factors in FS remains unclear.
Continuously increasing nociceptive inputs, especially in the early stages of FS, could lead to long-lasting central sensitization (CS). However, the involvement of CS in FS has not been studied yet and remains speculative. In addition, the role of maladaptive psychosocial factors, which are important therapy mediators/barriers in other chronic pain conditions, is unknown. Similarly, the influence of metabolic factors in FS remains unclear.
Purpose: This study assessed the correlations between CS measures and clinical symptoms (severity and duration of pain, disability), psychosocial factors and blood glucose concentrations in subjects with FS. In addition, the ability of baseline clinical symptoms, psychosocial factors and blood glucose concentrations to predict CS at 3 months follow-up was investigated.
Methods: Thirty-nine subjects with primary FS were included. All participants completed a Visual Analogue Scale and the following questionnaires: Shoulder Pain and Disability Index (SPADI), Pain Catastrophizing Scale (PCS), Pain Vigilance and Awareness Questionnaire (PVAQ) and Central Sensitization Inventory (CSI). Afterwards, all subjects performed Quantitative Sensory Testing to examine local and remote Pressure Pain Thresholds (PPTs), Temporal Summation (TS) and Conditioned Pain Modulation (CPM). Venous blood samples were collected to analyze the blood glucose concentration through glycohemoglobin test (AC1 test). All measurements were taken at baseline (T0) and 3 months follow-up (T3). Pearsons correlation coefficients were computed to reveal possible correlations between CS measures and clinical symptoms, psychosocial factors and blood glucose concentrations at T0. Multiple regression analysis was performed to assess the ability of baseline clinical symptoms, psychosocial factors and glucose concentrations to predict CS at T3.
Results: Significant correlations were observed between clinical symptoms with some measures of CS (CPM, TS, remote PPTs, CSI). Higher scores in PCS and PVAQ were significantly correlated with some CS correlates (remote PPTs, CPM and CSI). AC1 test scores were significantly correlated with CPM and CSI score.
Baseline VAS was able to predict 31% of variance of TS at T3. Moreover baseline symptoms duration, VAS and SPADI were able to predict 60.8% of variance of CPM at T3. The PVAQ score at baseline could predict 14% of variance of remote PPTs and 9.8% of variance of CPM at T3. Baseline PCS and PVAQ scores and blood glucose concentrations were able to predict 41% and 14.5% of variance of CSI scores at T3, respectively.
Conclusion(s): Clinical symptoms, psychosocial variables and blood glucose concentrations were associated with some CS variables and were able to predict variance of some CS correlates at 3 months in subjects with FS.
Implications: A greater duration and intensity of pain, presence of maladaptive psychosocial factors and excessive glucose concentration may alert clinicians to the presence of CS mechanisms in FS.
Funding acknowledgements: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Topic: Pain & pain management
Ethics approval: This study was approvedy the Human Research Ethics Committee of the University of Valencia, Spain
All authors, affiliations and abstracts have been published as submitted.
