In today's publication, we explore the relationship between infrared thermography and the intensity of low back pain. We analyze scientific evidence showing how thermal differences in the plantar surface can be linked to autonomic regulation and pain perception. Discover how this non-invasive tool can provide valuable insights for assessing and monitoring low back pain, helping to better understand its origin and potential treatment.

Introduction

Chronic low back pain (LBP) is one of the most common musculoskeletal conditions in the adult population, significantly affecting the quality of life and functionality of those who suffer from it. Although conventional imaging techniques, such as magnetic resonance imaging (MRI) or computed tomography (CT), allow for the evaluation of structural alterations, they do not always explain pain intensity or its individual variations.

In this context, infrared thermography (IRT) has emerged as a complementary tool for assessing autonomic nervous system dysfunctions and thermal patterns associated with various pathologies. By measuring skin temperature, thermography can identify alterations in circulation and sympathetic activity, offering a functional perspective on the problem.

A study by Zaproudina et al. (2006) explored the relationship between plantar surface temperature and LBP intensity, highlighting the potential of thermography as a physiological indicator of this condition. Their findings open new possibilities for a more objective evaluation of chronic low back pain and its impact on neuromuscular function.

Infrared Thermography and Low Back Pain

Infrared thermography is a non-invasive, radiation-free technique that allows for the detection of thermal alterations in the skin, reflecting changes in sympathetic nervous system regulation and possible vascular imbalances. In the context of low back pain, this technology provides an objective method for evaluating thermal anomalies associated with autonomic dysfunction and peripheral circulation.

The study by Zaproudina et al. (2006) investigated whether temperature changes in the plantar surface could be related to LBP intensity and vasomotor responses in patients with this condition. Since skin temperature is influenced by blood flow and autonomic nervous system activity, its measurement can provide relevant information on the pathophysiology of low back pain and its possible origin.

Study Methodology

The researchers analyzed 65 patients with unilateral chronic low back pain (LBP) and 20 subjects without a history of low back pain. Thermal images of the lower back and lower limbs, including the plantar surface, were taken to evaluate potential thermal differences between both sides of the body.

Participant Characteristics:

• LBP Group: 65 patients with unilateral chronic low back pain (29 men and 36 women, aged 30-51 years).
• Control Group: 20 individuals without LBP (7 men and 13 women, aged 30-49 years).

Clinical Assessments:

• Pain intensity: Measured using a visual analog scale (VAS, 0-100).
• Spinal mobility tests: Modified Schober test, straight leg raise (SLR), finger-to-floor distance, and lateral flexion.
• Functional disability: Oswestry Disability Index (ODI) questionnaire.

Thermographic Measurements:

• Infrared camera IRTIS Ltd. with a resolution of 0.05°C.
• Thermal images of the lower back and lower limbs (anterior, lateral, and posterior surfaces), as well as the plantar surface.
• A temperature difference greater than 0.38°C was considered abnormal.

The measurements were conducted under controlled conditions, ensuring that subjects were adequately acclimated before thermal imaging. This ensured that the detected thermal variations were attributable to the patients' clinical condition and not to external factors.

Key Study Findings

The findings indicated a significant relationship between plantar temperature and low back pain intensity. It was observed that patients with higher pain levels exhibited more pronounced thermal differences between both feet, suggesting a possible imbalance in autonomic regulation.

Plantar Surface Temperature Differences:

• LBP patients exhibited greater thermal asymmetry in the plantar surface compared to the control group.
• 50.8% of patients with low back pain had lower temperatures on the affected side, suggesting an exaggerated vasoconstrictive response.
• Patients with a colder affected side reported greater pain intensity (51.8 vs. 34.9, p < 0.001).

Effect of Referred Pain:

• Patients with referred leg pain showed more pronounced thermal differences compared to those with localized LBP. This suggests that the involvement of nerve structures may generate more intense autonomic responses, reflected in plantar temperature.

Association with Mobility and Disability:

• Thermal differences in the lumbar region correlated with lateral flexion and straight leg raise tests.
• The Oswestry Disability Index (ODI) correlated with thermal differences in the leg (p < 0.05), suggesting that thermal alteration is not only a marker of pain but also of functional limitation.

Thermal Alterations and Autonomic Dysfunction:

• A more pronounced vasoconstriction was observed in patients with higher pain levels, reflecting possible autonomic dysfunction. This indicates that, in addition to structural impairment, low back pain may involve mechanisms regulating blood flow and sympathetic response.

These findings suggest that plantar thermography could be a useful indicator for assessing the severity of low back pain and autonomic regulation alterations. Its use in clinical practice could help identify cases where pain is influenced by neurovascular factors rather than just structural damage.

Study Conclusions

The findings from Zaproudina et al. (2006) highlight the potential of plantar thermography in low back pain analysis, emphasizing:

• Plantar infrared thermography can serve as a useful physiological indicator in the evaluation of chronic low back pain (LBP) patients.
• Inter-lateral temperature differences in the plantar surface were significantly higher in LBP patients compared to reference subjects, suggesting its application in assessing autonomic dysfunctions.
• Persistent abnormal thermal profiles in the plantar surface could reflect altered sympathetic regulation mechanisms in these patients.
• Although thermography does not replace other structural imaging techniques (such as MRI or CT), it can be a valuable complementary tool in studying functional alterations in LBP..

Clinical Applications of Thermography in Low Back Pain

Monitoring plantar temperature using infrared thermography emerges as a tool for:

• Evaluation of autonomic dysfunction: Temperature differences may reflect alterations in sympathetic response and peripheral circulation, allowing for a more detailed analysis of the patient's neuromuscular status.
• Monitoring the progression of low back pain: As a non-invasive and reproducible technique, it enables the analysis of changes in the patient’s thermal response over time.
• Treatment assessment: It can be used to evaluate the effectiveness of therapeutic interventions, as normalization of temperature could reflect improvements in neuromuscular function and pain control.

Referencias

Zaproudina, N., Ming, Z., & Hänninen, O. O. (2006). Plantar infrared thermography measurements and low back pain intensity. Journal of Manipulative and Physiological Therapeutics, 29(3), 219-223.

Uematsu, S., Jankel, W. R., Edwin, D. H., Kim, W., Kozikowski, J., Rosenbaum, A., & Long, D. M. (1988). Quantification of thermal asymmetry: part 2: application in low-back pain and sciatica. Journal of neurosurgery, 69(4), 556-561.

Alfieri, F. M., Lima, A. R. S., & Battistella, L. R. (2019). Superficial temperature and pain tolerance in patients with chronic low back pain. Journal of bodywork and movement therapies, 23(3), 583-587.

Roy, R. A., Boucher, J. P., & Comtois, A. S. (2013). Comparison of paraspinal cutaneous temperature measurements between subjects with and without chronic low back pain. Journal of manipulative and physiological therapeutics, 36(1), 44-50.