Thermography and back pathology

08/02/2022 By: Alejandro del Estal, Víctor Escamilla & Ismael Fernández Home

In today’s post, we are talking about the relationship between infrared thermography and the most common back injuries and pathologies. We will see the scientific evidence on how thermography can help us better understand the clinical and subclinical pathology of the main reasons for the common back pain. From muscle contracture to the surgery room, including hernias, scoliosis and neurological pathology.

It is not the first time that we have seen spine pathology in depth: we have already seen clinical case studies of lumbar surgery and severe radiculopathy. However, in this publication we open the spectrum and we will try to address the most frequent spine pathologies (both clinical and subclinical), seen from the perspective of thermography and based on scientific evidence and cases collected with our experience.

Normal pattern, healthy back

Before presenting back pathology, we must understand what a healthy back is like, from the point of view of thermography. It is characterized by having a thermal regularity in the midline, along the entire column. In figure 1a, this thermal homogeneity can be seen with the naked eye in the back of a subject without pathology or pain. This is a known fact since the last century, where numerous studies show that in healthy subjects, the tendency to thermal symmetry in all regions of the body is clear. Specifically on the back region, the study by Uematsu et al. 1988, shows a comparative table of the different regions of the back in healthy subjects (with mean asymmetries inferior to 0.3º C) and in subjects with herniation phenomena (with mean asymmetries greater than 0.6º C).

Likewise, in figure 1b we can easily see how a subject with spinal pathology presents an abnormal pattern. This type of pattern depends largely on the specific pathology, as well as its severity.

**Figure 1.** a) healthy subject, regular midline; b) subject with pathology, interruption of the line, a blockade at the lumbar level can be seen.

Hyperthermic trends in back patterns

In this section, we mainly find subclinical pathology. The evidence defines it above all by the appearance of myofascial trigger points (MTrP). MTrPs, also known as muscle contractures with referred pain, are not considered a pathological entity per se, but they are directly related to the patient’s pain symptoms. In the scientific literature on MTrP and thermography, there is no consensus regarding its thermal behavior. We have low quality evidence on the relationship between the appearance of MTrPs and a reduction in skin temperature (Girasol et al. 2018). It seems that the most relevant studies in this regard, which combine imaging test technologies, such as ultrasound with thermographic findings, consider the MTrP as a slightly warmer region surrounded by cooler regions. In figure 2, we can see, from left to right, the ultrasound finding of the MTrP (a), followed by the thermographic image (b) and the histogram (c), which shows the heat peaks of the thermal image. The authors explain this phenomenon by a potential reduction in the blood flow of the region (Cojocaru et al. 2015).

**Figure 2.** Correlation between PGM detected by ultrasound (a) and by thermography (b). In the thermogram you can see two points of heat, corresponding to two PGM. In the histogram (c) we can see three heat peaks, the two lateral ones correspond to the PGM and the central one, to the heat line of the spine.

Hypothermic trends in back patterns

Today, the scientific literature relates in most cases the structural findings of imaging tests in patients with nerve pathology with hypothermic results studied with thermography. In this publication, we made a narrative review on the thermal behavior of radiculopathy and peripheral nerve compressions. The conclusion was that when there is a pathology that compresses a nerve root, the thermal result in the territory it innervates is in most cases lower temperature than the same region on the healthy side. A direct relationship has also been found between the decrease in the temperature of the territory innervated by an affected nerve and the limitation in both motor skills and sensitivity of that region. The pathologies that fall within this classification range from radiculopathy to spinal fusion, including spinal cord injury, disc herniation and sciatic compression. We will address this issue in subsequent posts. In figure 3 we can see at a glance the hypothermic profile in the region of nerve compression.

**Figure 3.** Back analyzed with thermography. Patient with a compression problem of several nerve roots at the left dorsal level.

Patterns with normothermic trends and back pain

Many patients come to consultation with low back pain, but without a direct relationship with a structural problem, that is, with an imaging test without diagnosis of injury or tissue damage. In these types of cases, when a thermographic analysis is performed, the thermal result is usually inconclusive, both from the scientific evidence (Alfieri et al. 2019; Roy et al. 2013) as from our clinical experience. The main reason is that the physiology of the region has not changed, so the temperature remains stable and without asymmetries. However, there has been a change in the sensitivity of the region, which explains the reason for consultation, the main cause being contextual factors, such as work stress or sleep disorders (Buruck et al. 2019). We will publish a more detailed explanation on the difference between structural and physiological assessment, from the point of view of thermography in the coming months. In figure 4, we can see a thermography of the lumbar region of a patient with low back pain (a) and the exact location of the pain (b), which demonstrates the discrepancy between the thermal finding and the symptomatology when there is no evidence of tissue damage.

**Figure 4.** Lumbar region of a patient with pain (a) and its exact location (b), with no apparent relationship to tissue damage or thermal findings.

Asymmetric patterns

Finally, there are some pathologies that directly or indirectly affect the spine and that cause some type of alteration in verticality. This type of patient usually presents pronounced thermal asymmetries, since it is characterized by relevant postural asymmetries. This group includes pathologies of a very diverse nature, such as amyotrophic lateral sclerosis, stroke or scoliosis. We highlight in figure 5, some cases where thermal asymmetries are relevant.

**Figure 5**. a) stroke patient, 13 years after stroke. It is very interesting to note that the entire affected side (left) has a lower temperature, since sensitivity and motor skills are decreased. b) scoliosis patient. A slight thermal asymmetry can be seen, related to the general loss of verticality.

Conclusion

Spine pathology and back pain are really heterogeneous and its identification and assessment by thermography can provide very valuable information about the nature, severity and adaptation of the patient. The idiosyncrasy is so diverse that we can find completely opposite behaviors, from very hypothermic pathologies (several negative degrees of asymmetry with respect to the healthy side) to others that present warmer affected regions, passing through normothermic patients. The interpretation of this information is essential for the clinician to obtain a quality assessment and to be able to make decisions that lead to the appropriate treatment for each patient.

REFERENCES:

Alfieri FM, Lima ARS, Battistella LR, Silva NCOVE. Superficial temperature and pain tolerance in patients with chronic low back pain. J Bodyw Mov Ther. 2019 Jul;23(3):583-587.

Buruck G, Tomaschek A, Wendsche J, Ochsmann E, Dörfel D. Psychosocial areas of worklife and chronic low back pain: a systematic review and meta-analysis. BMC Musculoskelet Disord. 2019 Oct 25;20(1):480.

Cojocaru MC, Cojocaru IM, Voiculescu VM, Cojan-Carlea NA, Dumitru VL, Berteanu M. Trigger points–ultrasound and thermal findings. J Med Life. 2015;8(3):315-318.

Girasol CE, Dibai-Filho AV, de Oliveira AK, de Jesus Guirro RR. Correlation Between Skin Temperature Over Myofascial Trigger Points in the Upper Trapezius Muscle and Range of Motion, Electromyographic Activity, and Pain in Chronic Neck Pain Patients. J Manipulative Physiol Ther. 2018 May;41(4):350-357.

Roy RA, Boucher JP, Comtois AS. Comparison of paraspinal cutaneous temperature measurements between subjects with and without chronic low back pain. J Manipulative Physiol Ther. 2013 Jan;36(1):44-50.

Uematsu S, Jankel WR, Edwin DH, Kim W, Kozikowski J, Rosenbaum A, Long DM. Quantification of thermal asymmetry. Part 2: Application in low-back pain and sciatica. J Neurosurg. 1988 Oct;69(4):556-61.

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