Use of infrared thermography in patients with plantar fasciitis
To find out if we are facing plantar fasciitis, infrared thermography allows, in a fast and non-invasive way, to identify the physiological state of the connective tissues of the human body, support the diagnosis and quantify the evolution of this pathology.
Measurement of skin temperature using thermography helps support diagnosis by identifying different patterns when the body has lost thermal homeostasis. In other words, it allows us to evaluate hyperthermic or hypothermic patterns that generate asymmetries when the body is not keeping the balance it should (Sillero-Quintana et al. 2015).
The reasons why thermal asymmetries are generated depend on different factors that are intrinsic or extrinsic to the individual. When we face an intrinsic factor that modifies temperature asymmetrically, we can think that it is due to compensation or related to a pathology, such as an inflammatory process or neuralgia.
For this reason, evaluating the thermal asymmetries in different body regions susceptible to injury allows us to standardize normality and identify those thermal patterns that are related to different pathologies, such as plantar fasciitis.
What’s new in plantar fasciitis diagnosis research
The research group of Dr. Antonio Gómez Bernal wanted to analyze the thermal pattern of plantar fasciitis in their research. In order to do this, they selected patients who had been diagnosed with plantar fasciitis and related it to their thermal profile using thermography.
Due to its etiology, plantar fasciitis is a degenerative pathology of the fascia caused by a continuous application of forces, due to its high commitment to the biomechanics of the foot, which reach the point of structural failure of the tissue. This pathology is one of the most common in the foot (Thing et al. 2012).
In the first days of a plantar fasciitis, the inflammatory phase begins, followed by a fibroblastic phase where collagen synthesis and fascial neovascularization proliferate (Schepsis et al. 1991). The last phase, corresponding to tissue remodeling and regeneration, can last up to 12 months (Fernandez et al. 1983).
For all these reasons, the authors (Gómez-Bernal et al. 2021) hypothesize that thermography could be useful to identify significant differences between healthy feet and those diagnosed with plantar fasciitis.
To do this, they selected 16 patients diagnosed with acute unilateral plantar fasciopathy with less than one month of evolution and who did not have a body mass index greater than 30 (BMI <30). They analyzed the thermographic images with ThermoHuman software, which segments the insoles of the feet into 18 regions of interest, as shown in Figure 1.
Significant results in the identification of the thermographic profile of plantar fasciitis
The results they obtained show a statistically significant difference between the regions of the head of the first metatarsal, the external and internal arches of the foot, the internal and external regions of the heel of the injured foot compared to the healthy foot. In addition, the asymmetry becomes remarkable for the software with a difference greater than 0.3 ºC in the regions of the internal arch and the heel (Figure 1), where we found the maximum temperatures.
The authors point out that the most common areas of pain in patients with plantar fasciitis originate in the medial calcaneal tuberosity of the heel and continue in its aponeurosis, which seems to have a direct relationship with the results of thermography. In addition, this type of patient requires a major metabolic process for its repair (Lim et al. 2016).
Temperature differences in the other regions such as the area of the II-V toes, the head of the first metatarsal or the region of the fifth metatarsal can be a consequence of an antalgic gait by avoiding the tensioning of the plantar fascia (Lim et al. 2016).
The work of Gómez-Bernal et al. (2021) is the first one that identified a hyperthermic pattern in the regions affected by plantar fasciitis and emphasizes that temperature variations in the regions of the foot are related to pathological processes, as other studies in patients with diabetic foot also indicate (Astasio-Picado et al. 2020).
Conclusions
In conclusion, we can affirm that thermography allows the identification of patients with acute unilateral fasciitis, due to its hyperthermic pattern in the injured regions, which present a significant asymmetry compared to the healthy foot.
This is why the analysis with a specific software that allows measuring the temperatures of the body regions is decisive in establishing the differences and identifying the significant asymmetries, thus supporting the diagnosis of plantar fasciitis.
References
Astasio-Picado, Á., Martínez, E. E., & Gómez-Martín, B. (2020). Mapa térmico comparativo del pie entre pacientes con y sin diabetes mediante el uso de termografía infrarroja. Enfermería Clínica, 30(2), 119-123.
Fernandez, A., & Finley, J. M. (1983). Wound healing: helping a natural process. Postgraduate medicine, 74(4), 311-317.
Gómez-Bernal, A. G., Fernández-Cuevas, I., Santafé, J. J. A., Morcillo, A. P., & Arasanz, A. J. A. (2021). Uso de la termografía infrarroja para determinar el perfil térmico de la planta del pie en pacientes con fasciopatía plantar: estudio transversal. Revista española de podología, 32(2), 93-98.
Lim, A. T., How, C. H., & Tan, B. (2016). Management of plantar fasciitis in the outpatient setting. Singapore medical journal, 57(4), 168.
Schepsis, A. A., Leach, R. E., & Gorzyca, J. (1991). Plantar fasciitis. Etiology, treatment, surgical results, and review of the literature. Clinical Orthopaedics and Related Research, (266), 185-196.
Sillero-Quintana, M., Fernández-Jaén, T., Fernández-Cuevas, I., Gómez-Carmona, P. M.,
Arnaiz-Lastras, J., Pérez, M. D., & Guillén, P. (2015). Infrared thermography as a support tool for screening and early diagnosis in emergencies. Journal of Medical Imaging and Health Informatics, 5(6), 1223-1228.
Thing, J., Maruthappu, M., & Rogers, J. (2012). Diagnosis and management of plantar fasciitis in primary care. British Journal of General Practice, 62(601), 443-444.
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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). 
