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Alaiti R.K.1,2, Gasparin J.T.2, de Sousa M.F.d.C.2, Pompeu J.E.2,3, Gracitelli M.E.4, Malavolta E.A.4, Neto A.A.4, Costa M.F.d.1,2
1University of São Paulo, Experimental Psychology, São Paulo, Brazil, 2University of São Paulo, Neuroscience and Behavior, São Paulo, Brazil, 3University of São Paulo, Physical Therapy and Occupational Therapy, São Paulo, Brazil, 4Orthopaedics Institute of the University of São Paulo, Shoulder and Elbow Group, São Paulo, Brazil
Background: New evidences suggests that pain perception is a probabilistic inferential process held by our brains, based on our previous history of exposure to certain contexts and stimulus, whose main goal involves the subsequent targeting of protective behavior. Thus, to obtain an adequate understanding of the painful phenomenon, we have to evaluate it in the context in which it occurs with instruments of measurement accurate and sensitive enough to access the pain perception continuous of this population.
Purpose: The purpose of the presente study was to analyse the relation between the functional pain measured by a ratio scale and measures related to functional disability and pain intensity derived from other scales developed for patients with shoulder pain.
Methods: 85 patients (61,65 ±8,77 years old) diagnosed with rotator cuff dysfunction (tendinopathy, partial or a full-thickness tear) from traumatic or degenerative etiology, right-handed, symptomatic, sedentary and with the beginning of the complaint in the shoulder region for at least 3 months were randomly selected between the patients in care in the Shoulder and Elbow Group of the IOTFMUSP. Their functional pain were assessed in a ratio level by the power function exponent (PFE) derived from the numerical magnitude estimations made for the pain percept at rest and during the 10 movements of The Psychophysical Scale for Functional Shoulder Pain Evaluation developed by our research group. Besides that, the questionnaires Constant-Murley, ASES and SPADI were used to access the funcional capacity and disability and the pain intensity was also measured by a 10 cm Visual Analog Scale with the left extremity labeled as "no pain" and the right as "worst pain possible".
Results: The correlation analyses showed a significant correlation between the PFE and the VAS (r=-0,29), ASES (r=0,30), SPADI pain (r=-0,23), SPADI disability (r=-0,33), SPADI (r=-0,32) and the Constant-Murley score (r=0,34).
Conclusion(s): The correlations identified between the PFE, the VAS and the functional capacity and disability scores suggests that individuals with low exponents, which suggest small variations of the pain magnitude percept during the movements, have more overall functional disability and pain intensity while individuals with higher exponents, which suggest that some movements are much more painful than others, have less overall functional disability and pain intensity.
Implications: One of the main advantages of using a ratio scale to evaluate perceptual phenomena involves the fact that these scales are highly informative. While we can not be sure about exactly what the VAS data are representing or based on what they have been produced and its not possible to infer how many times the pain perception of an individual was bigger or lesser in one function over another in interval scales as the SPADI, for example, the PFE provides us with a quantitative data about the influence that the modification of the demands of a particular function or a class of functions has on the pain perception of an individual in supra-threshold levels, allowing statements about the ratio of the differences between the obtained pain measures.
Funding acknowledgements: This paper was supported by the scholarship 130699/2016-0 from the CNPq and FAPESP #04049-4.
Topic: Pain & pain management
Ethics approval: This study was approved by the Ethics Committee of the Psychology Institute of the University of São Paulo, protocol 49635115.5.0000.5561.
All authors, affiliations and abstracts have been published as submitted.
