This publication, which can be found here, comes from the research group of the University of Paraíba, in João Pessoa (Brazil), who have done an excellent job that we would love to comment on.
The tendon is the tissue that transfers the kinetic energy generated by the muscles to the bones, thus producing movement. It is an elastic fabric, which characterizes it for having very good load absorption capacities.
However, this also makes it susceptible to injury, by destruction, inflammation or degeneration, especially in the limbs. This is probably the reason why the most common tendinopathies are those of the rotator cuff, gluteus, Achilles, patellar and epicondylar region (Millar et al., 2021), as in the example in Figure 1:
Figure 1. Representation of the injury mechanism of labor epicondylitis (microrepetition of hitting with a hammer or backhand grip in tennis)
The appearance of pain in a tendinopathy is related to the anatomical and mechanical changes of the tendon. However, despite what it might seem, these changes cause the tenocytes and peripheral nerves to react and activate the higher centers through nociceptive pathways. In this way, the role of the Central Nervous System (CNS) is key, since the innervation of the affected region tends to be greater than that of the healthy area (Andersson et al. 2007; Jewson et al. 2015; Dean et al. 2017).
In fact, the intervention of the CNS is key in the activation of adrenergic receptors, which stimulate vasoconstriction or vasodilation, thus altering local blood flow and temperature (Liu et al. 2020). Despite this, there is some evidence that calls this claim into question (Oskarsson et al. 2007).
For several decades, localized hyperthermic asymmetry has been detected in 98% (Binder et al. 1983) and 94% of epicondylitis cases (Thomas et al. 1992), as can be seen in Figure 2. However, no significant asymmetries have been found in intra-articular tendon pathologies (Vecchio et al. 1992).
In Figure 2, we can see three examples from the literature where patients with epicondylitis are thermally analyzed. In (Binder et al. 1983), that we observed a thermogram of an elbow with epicondylitis, with the hottest point located at the insertion of the epicondylar musculature. The image extracted from (Thomas et al. 1992) shows us the entire side of the elbow always warmer in cases of epicondylitis. Lastly, the study by Meknas et al. (2008), analyze patients with epicondylitis and in the image, an example where an arrow points to the hyperthermic area at the insertion of the epicondylar musculature.
Figure 2. Images taken from (Binder et al. 1983) (A), (Thomas et al. 1992) (B) and Meknas et al. (2008) (C).
More recently, the latest systematic review in this regard already confirmed that the skin covering an inflamed tendon has a higher temperature (Chaudhry et al. 2016). On the other hand, the tendons of healthy people are thermally symmetrical (Tumilty et al. 2019), a fact that we have already explained in detail in this publication.
From our clinical experience, we have treated patients with epicondylitis and the results seem to indicate that the region with pain consistently tends to be hyperthermic, as we can see in figure 3:
Figure 3. Thermogram and avatar of a patient with epicondylitis. We can observe higher temperatures in the region with pain. Property of ThermoHuman.
These results are in line with those shown by authors such as Binder et al. (1983), Thomas et al. (1992) or Meknas et al. (2008). They affirm that epicondylitis offers a localized hyperthermic pattern, due to the increased blood supply in the area. Some authors even affirm that thermography is a valid tool to support the diagnosis in epicondylitis (Haake et al. 2002).
Results of the systematic review with meta-analysis
Similarly, the research group at the University of Paraíba, in João Pessoa (Brazil), led by Dr. José Jamacy Almeida Ferreira, includes 7 studies in its review (Dias de Lacerda et al. 2022).
Of which, Vecchio et al. (1992) and Park et al. (2007) investigated shoulder tendinopathies; Mangine et al. (1987) on patellar tendinopathy; and Sillero-Quintana et al. (2015) on tendinopathies in general. Binder et al. (1983), Thomas et al. (1992) and Meknas et al. (2008). , who were already commented in the previous section, investigated tendinopathy in the epicondylar region or epicondylitis.
In figure 4, we can see the sensitivity and specificity graphs of these studies, which give us an average result of sensitivity of 0.72 and specificity of 0.95.
Figure 4. Statistical results of the meta-analysis of Dias de Lacerda et al. (2022).
The results of the systematic review with meta-analysis by Dr. José Jamacy Almeida Ferreira demonstrated that infrared thermography shows appropriate specificity without heterogeneity between studies for the evaluation of lateral epicondylitis and shoulder tendinopathy. However, the sensitivity results have significant heterogeneity, which significantly reduces their precision.
In general, the tendon tends to have hyperthermic behavior when there is tissue damage, especially if it is in an acute phase of the process. Thermography helps us to assess the severity of the injury and guide treatment based on the thermal response of said tendon.
Andersson G, Danielson P, Alfredson H, Forsgren S. Nerve-related characteristics of ventral paratendinous tissue in chronic Achilles tendinosis. Knee Surg Sports Traumatol Arthrosc. 2007 Oct;15(10):1272-9.
Binder A, Parr G, Thomas PP, Hazleman B. A clinical and thermographic study of lateral epicondylitis. Br J Rheumatol. 1983 May;22(2):77-81.
Chaudhry S, Fernando R, Screen H, Waugh C, Tucker A, Morrissey D. The use of medical infrared thermography in the detection of tendinopathy: a systematic review, Physical Therapy Reviews. 2016 Sep, 21:2, 75-82,
Dean BJF, Dakin SG, Millar NL, Carr AJ. Review: Emerging concepts in the pathogenesis of tendinopathy. Surgeon. 2017 Dec;15(6):349-354.
Dias de Lacerda AP, Rodrigues de Andrade P, Kamonseki DH, Parizotto NA, Alves da Silva AS, Bernardo de Medeiros L, de Almeida Ferreira JJ. Accuracy of infrared thermography in detecting tendinopathy: A systematic review with meta-analysis. Phys Ther Sport. 2022 Oct 10;58:117-125.
Haake M, Willenberg T, Sauer F, Griss P. Einfluss der Extrakorporalen Stosswellentherapie auf die Gefässregulation. Infrarotthermographie bei Epicondylitis humeri radialis [Effect of extracorporeal shockwave therapy on vascular regulation. Infrared thermography in epicondylitis humeri radialis]. Swiss Surg. 2002;8(4):176-80.
Jewson JL, Lambert GW, Storr M, Gaida JE. The sympathetic nervous system and tendinopathy: a systematic review. Sports Med. 2015 May;45(5):727-43.
Liu L, Gisselman AS, Tumilty S. Thermal profiles over the Patella tendon in a cohort of non-injured collegiate athletes over the course of a cross-country season. Phys Ther Sport. 2020 Jul;44:47-52.
Mangine RE, Siqueland KA, Noyes FR. The use of thermography for the diagnosis and management of patellar tendinitis. J Orthop Sports Phys Ther. 1987;9(4):132-40.
Meknas K, Odden-Miland A, Mercer JB, Castillejo M, Johansen O. Radiofrequency microtenotomy: a promising method for treatment of recalcitrant lateral epicondylitis. Am J Sports Med. 2008 Oct;36(10):1960-5.
Millar NL, Silbernagel KG, Thorborg K, Kirwan PD, Galatz LM, Abrams GD, Murrell GAC, McInnes IB, Rodeo SA. Tendinopathy. Nat Rev Dis Primers. 2021 Jan 7;7(1):1.
Oskarsson E, Gustafsson BE, Pettersson K, Aulin KP. Decreased intramuscular blood flow in patients with lateral epicondylitis. Scand J Med Sci Sports. 2007 Jun;17(3):211-5.
Park JY, Hyun JK, Seo JB. The effectiveness of digital infrared thermographic imaging in patients with shoulder impingement syndrome. J Shoulder Elbow Surg. 2007 Sep-Oct;16(5):548-54.
Thomas D, Siahamis G, Marion M, Boyle C. Computerised infrared thermography and isotopic bone scanning in tennis elbow. Ann Rheum Dis. 1992 Jan;51(1):103-7.
Tumilty S, Adhia DB, Smoliga JM, Gisselman AS. Thermal profiles over the Achilles tendon in a cohort of non-injured collegiate athletes over the course of a cross country season. Phys Ther Sport. 2019 Mar;36:110-115.
Vecchio PC, Adebajo AO, Chard MD, Thomas PP, Hazleman BL. Thermography of frozen shoulder and rotator cuff tendinitis. Clin Rheumatol. 1992 Sep;11(3):382-4.
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ThermoHuman has had the support of the Funds of the European Union and the Community of Madrid through the Operational Programme on Youth Employment. Likewise, ThermoHuman within the framework of the Export Initiation Program of ICEX NEXT, had the support of ICEX and the co-financing of the European Regional Development Fund (ERDF).
Thermohuman has received funding from the Centre for the Development of Industrial Technology (CDTI), in participation with the European Regional Development Fund (ERDF), for the R+D activities involved in creating a new tool, based on thermography, for the prediction and prevention of rheumatoid arthritis. See project detail.
