Central and Peripheral Sensitization, Pain Mediators in Thumb Pain Among Physiotherapists

The work-related thumb pain is a common problem among physiotherapists which deal with this experience at least once in their life. Several studies analyzed the distribution of mechanical forces, kinematics, and kinesiology of the thumb in this clinical condition. However, there is no data, available in the literature, on how this pain processed is sustained and if plastic changes in the central or peripheral nervous system are involved. The research aims are to investigate the relationship between the thumb pain and pain related central and peripheral nervous sensitization phenomena among physiotherapists (exposed to work) and physiotherapy students (not exposed). The relevance of each of the pain chronification mediators, reported in the literature (anxiety, depression catastrophization, self-efficacy, kinesiophobia) will be also defined. Data on pain intensity, muscle strength, and endurance in the hand will be collected and the relation between peripheral sensitization phenomena in the hand, and central sensitization will be assessed. Also, the relevance of pain mediators and the health perceived status will be assess adopting validated questionnaires and the minimal Generic ICF core set.

Introduction: Physiotherapists' work-related thumb pain is a problem recognized by the World Health Organization to be the major work-related musculoskeletal problems (WMSDs) for this profession. About 70.8% of physiotherapists experience thumb pain at least once in their life. In those who practice manual therapy, thumb pain can determine the use of compensatory strategies or the impossibility to practice wanted manipulation. It has been estimated that 1 in 6 physiotherapists end their careers because of WMSDs. The data available in the literature on biomechanics for this phenomenon do not allow to define a proper causa relation lacking to describe the impact of pain mechanisms involved, the impact of mediators of chronicity in pain, and health status.

The purpose of the present research is to investigate the relation between thumb pain and phenomena of central or peripheral plasticity among physiotherapists (exposed) and compare this data to physiotherapy students (not exposed). In particular, we aim to identify the relevance of each chronic pain mediator described in the literature (anxiety, depression, self-efficacy, kinesiophobia) in this health condition.

Methods: A case-control study will be performed. 44 physiotherapists with thumb pain and 44 physiotherapy students will be evaluated. Muscle strength and endurance of the hand will be assessed. Assessment of peripheral sensitization phenomena will be performed with validated clinical tests. It will also be assessed the health status through the minimal ICF core set, the intensity of pain, and through validated questionnaires the central sensitization, anxiety, depression, catastrophization, kinesiophobia, and self-efficacy. The sample size of 44 subjects per group (10% dropout) was estimated a priori, with a clinically relevant effect size of d= .80 and with an estimated power (1- beta )= .95 and α= 0.05.

Expected results: The results of this study can improve the knowledge of the pain mechanisms involved and the complexity of this work-related disabling condition following a multifactorial biopsychosocial model. Results could also improve the prevention of thumb pain in physiotherapists with a relevant impact on this work-related disease.

Eligibility Criteria:
Inclusion Criteria:

* Subjects giving their written consent to be enrolled in the study.
* Subjects aged more than 18 years old.
* Registration to the professional register or to the degree course in Physiotherapy
* History of at least 1 episode of work-related thumb pain in the last 3 months for physiotherapists

Exclusion Criteria:

* Recent or current pain/pathology of the upper limbs and neck;
* Pregnancy;
* Neurological disorders that increase or decrease the tone of upper limb and neck muscles;
* Rheumatic diseases
* Recent hand surgery