Thermography--its current diagnostic status in musculoskeletal medicine

Quantification of edematous changes by diffusion magnetic resonance imaging in gastrocnemius muscles after spinal nerve ligation

Patients with complex regional pain syndrome (CRPS) exhibit diverse symptoms, such as neuropathic pain, allodynia, local edema and skin color changes in the affected lesion. Although nerve injury may cause CRPS, pathophysiological mechanisms underlying the syndrome are unclear, and local edema, a characteristic of CRPS, has not been evaluated quantitatively for technical reasons. Here, using a rat spinal nerve ligation-induced CRPS model, we show that edematous changes in gastrocnemius muscle can be detected quantitatively by diffusion magnetic resonance imaging (MRI). Using the line-scan diffusion spectrum on a 1.5 T clinical MR imager, we demonstrate significant elevation of the apparent diffusion coefficient (ADC) ratios in gastrocnemius muscle on the ligated versus the sham-operated rats by one day after surgery, those ratios gradually decreased over time. Meanwhile, T2 ratios in gastrocnemius muscle on the ligated rats increased gradually and significantly, peaking two weeks after surgery, and those ratios remained high and were consistent with edema. Expression of vascular endothelial growth factor (VEGF), a key regulator of blood vessel formation and function, was significantly lower in gastrocnemius muscle on the ligated versus non-ligated side, suggesting that nerve ligation promotes edematous changes and perturbs VEGF expression in target muscle.

Infrared thermography is useful for ruling out fractures in paediatric emergencies

Musculoskeletal injuries are a leading cause of paediatric injuries and emergency department visits in Western countries. Diagnosis usually involves radiography, but this exposes children without fractures to unnecessary ionising radiation. We explored whether infrared thermography could provide a viable alternative in trauma cases. We compared radiography and thermal images of 133 children who had been diagnosed with a trauma injury in the emergency unit of a Spanish hospital. As well as the thermal variables in the literature, we introduced a new quantifier variable, the size of the lesion. Decision tree models were built to assess the technique's accuracy in diagnosing whether a bone had been fractured or not. Infrared thermography had a sensitivity of 0.91, a specificity of 0.88 and a negative predictive value of 0.95. The new lesion size variable introduced appeared to be of main importance to the discriminatory power of the method.

CONCLUSION

The high negative predictive value of infrared thermography suggests that it is a promising method for ruling out fractures.

Infrared thermal imaging in the diagnosis of musculoskeletal injuries: a systematic review and meta-analysis

OBJECTIVE

Musculoskeletal injuries occur frequently. Diagnostic tests using ionizing radiation can lead to problems for patients, and infrared thermal imaging could be useful when diagnosing these injuries.

CONCLUSION

A systematic review was performed to determine the diagnostic accuracy of infrared thermal imaging in patients with musculoskeletal injuries. A meta-analysis of three studies evaluating stress fractures was performed and found a lack of support for the usefulness of infrared thermal imaging in musculoskeletal injuries diagnosis.

Biomedical applications of functional infrared imaging

This paper introduces the reader to the functional infrared imaging, that is the application to the biomedical field of high-technology infrared imaging devices combined to the modeling of the bio-heat processes involved in the body thermoregulation. Such an approach allows defining quantitative parameters for diagnosis and monitoring. Some recent biomedical applications of the technique are then shown and explained.

Malingering pain in the medicolegal context

Malingering--the willful, deliberate, and fraudulent feigning or exaggeration of illness--was originally described as a means of avoiding military service. In present-day clinical practice, malingering may occur in circumstances where the person wishes to avoid legal responsibility or in situations where compensation or some other benefit might be obtained. In law, the term malingering is used in relation to persons to whom military regulations apply; in other situations, malingering is regarded as fraud and may lead to charges of perjury or criminal fraud. Assertions that an individual is malingering are particularly common in clinical settings where the complaint is of a subjective nature and is not accompanied by objectively demonstrable organic abnormalities. This may occur in relation to complaints of pain in situations where the person is entitled to receive pain-contingent compensation or is suing for damages. In this article, we will review the literature on pain and malingering and discuss attempts that have been made to develop methods and guidelines for the detection of malingered pain. There are, however, no valid clinical methods of assessment of possible malingering of pain. In our view, the ultimate issue of the veracity of the plaintiff is for the Court to decide, and epithets such as "malingerer" have no place in reports prepared for legal purposes by health care professionals.

Impairments and activity limitations in subjects with chronic upper-limb complex regional pain syndrome type I

OBJECTIVE

To determine the degree of impairments and activity limitations and their interrelationship in complex regional pain syndrome type I (CRPS type I).

DESIGN

Cross-sectional study interrelating impairments and objectively measured activity limitations.

SETTING

Ambulatory and home environment.

PARTICIPANTS

Thirty nonacute upper-limb CRPS type I subjects.

INTERVENTIONS

Not applicable. Main outcome measures Sensory, motor, and autonomic impairments, as well as activity-limitation outcome measures. The latter were objectively measured with a novel upper-limb activity monitor (based on ambulatory accelerometry).

RESULTS

All subjects were impaired to some degree but with a large variability with respect to magnitude. Regarding activity limitations, the involved upper limb was clearly less active (lower intensity and percentage of activity) than the noninvolved side. Impaired active range of motion (adjusted R(2) range, 18%-39%) and grip strength (adjusted R(2) range, 12%-45%) were the most important factors explaining variance in activity limitations.

CONCLUSIONS

All subjects were still impaired nearly 3 years after the causative event. The involved upper limb was also clearly less active than the noninvolved side, especially when the subjects were sitting and when the dominant side was involved. The more impairments a subject had, especially motor impairments, the more activity limitations were present.

Infrared skin temperature measurement cannot be used to detect myofascial tender spots

OBJECTIVE

To determine the relationship between skin temperature and pressure tolerance in patients with myofascial pain.

DESIGN

Blinded, criterion standard.

SETTING

Community physiatry clinic.

PATIENTS

Sixteen consecutive female patients with myofascial pain or fibromyalgia with shoulder girdle symptoms above the T4 level for at least 3 months. No patient met the exclusion criteria of recent trauma to the area or therapy within 48 hours.

INTERVENTIONS

Skin temperature was measured by using a hand-held infrared thermometer over 36 points arranged in a grid on the upper and midtrapezius. Pressure threshold was then assessed at each point by using a pressure threshold meter. A second, blinded examiner then examined each patient to find any myofascial tender spots and noted within which square on the grid they occurred.

MAIN OUTCOME MEASURES

The correlation between temperature and pressure threshold and the temperature differences between tender and nontender areas.

RESULTS

A nonsignificant correlation of.023 (p =.57) was found between temperature and pressure threshold. The mean temperature of the tender spots was 32.1 degrees C. No significant difference existed between tender spot temperature and temperature of nontender points (32.1 degrees C, p =.653) or contralateral points (32 degrees C, p =.893).

CONCLUSIONS

Skin temperature, measured with a hand-held infrared thermometer, cannot be used to diagnose and follow treatment progress of myofascial tender spots, because skin temperature over tender spots does not correlate with pressure sensitivity.

Reliability and normal values for measuring the skin temperature of the hand with an infrared tympanic thermometer: a pilot study

Recording asymmetry in skin temperature between symmetric body areas is useful in monitoring diseases that alter skin temperature. This pilot study checked the reported high reliability of recording skin temperature of the hands with an infrared tympanic thermometer, provided insight into the relationship between dorsal and palmar temperature differences, and assessed the agreement between these data and normative data obtained from thermograms. Using an infrared tympanic thermometer, two independent assessors measured the temperature of 13 asymptomatic, right-handed subjects (mean age, 30 years; range, 21 to 44 years). Both test-retest and interobserver reliabilities were high. Skin temperature of the hand differed with the site where it was measured; differences between sites changed over time. The mean absolute differences in skin temperature between dorsal and palmar aspects of the hands were 0.30 degrees C and 0.25 degrees C, respectively. These data match normative values reported in the literature for infrared thermograms.

Objective and subjective assessments of temperature differences between the hands in reflex sympathetic dystrophy

OBJECTIVE

A difference in temperature between the affected and normal extremity is one of the signs or symptoms of reflex sympathetic dystrophy (RSD). These temperature differences are scored anamnestically, by palpation, or by measurements. We investigated the relationship between objective and subjective differences in skin temperature between the hands.

SUBJECTS AND DESIGN

Fifty-one patients with RSD of one upper extremity participated (mean age 55 years, range 18-80). In the first 16 we investigated the reliability of the visual analogue scale (VAS) for recording perceived differences in skin temperature. In the remaining 35 patients the relationship between the VAS and objective infrared radiometry of the hands was investigated.

SETTING

Outpatients clinics of two university hospitals.

RESULTS

The VAS was found to be reliable in terms of response stability. There was no significant correlation between the objective and subjective outcomes.

CONCLUSIONS

There is lack of correspondence between objective and subjective temperature measurements, which may be due to a normal discrepancy between objective and perceived temperature, and/or to alterations in perception due to RSD.

Impairment level sumscore in reflex sympathetic dystrophy of one upper extremity

OBJECTIVES

To construct a set of instruments to measure the level of impairment in reflex sympathetic dystrophy (RSD), to convert the scores for each instrument into one score and to derive a compounded impairment level sumscore (ISS), and to evaluate reliability, validity, and responsiveness of the ISS.

DATA SOURCES AND EXTRACTION

Literature search in Medline (1985 to 1995), non-Medline journals, and references from these reports for measurement parameters and suitable, reliable, responsive, and validated instruments.

DATA SYNTHESIS

Four measurement parameters (pain, active range of motion, temperature, and volume) and five measurement instruments were chosen to construct the ISS. All outcomes were converted into one score, resulting in an addable score.

RESULTS

Forty-five patients with RSD of one upper extremity were evaluated. As expected for this heterogeneous index, the internal consistency of the ISS was poor to moderate. The ISS seemed to have content and concurrent validity. The responsiveness of the ISS was adequate.

CONCLUSIONS

A multicomponent test was constructed to map alterations in the level of impairment in RSD patients. Each of the parameter scores could be translated into a uniform score. Adding the scores yielded the ISS.

Regional hypothermia in response to minor injury

Minor injuries are sometimes followed by a potentially disabling syndrome of hyperalgesia, hyperesthesia, allodynia, and sudomotor disturbance as well as, eventually, weakness, muscle atrophy, trophic skin changes, and bone and joint abnormalities. Vasomotor changes frequently present as hypothermia or hyperthermia. Most of the literature refers to this syndrome as reflex sympathetic dystrophy (RSD). To observe possible early RSD changes, we studied 1000 military recruits before and during basic training. Evaluations consisted of lower limb clinical examinations and pain assessment. Infrared images were taken of anterior, posterior, medial, lateral legs, and plantar surface of the feet. If the clinical examination suggested a possible stress fracture, a bone scan was performed. Recruits were studied before training and again each time musculoskeletal complaints arose. The controls were recruits tested before the onset of training who had no musculoskeletal complaints. Two-hundred seven soldiers were injured. Regional hypothermia was noted in 8.6% of all thermograms, with 75% on the left and 25% on the right. The most common injuries causing this phenomenon were ankle pain/sprain and minor foot stress fractures, especially the left metatarsals. Hypothermia occurred within 24 to 48 h, usually beginning in the periphery and ascending proximally, lasting a few days to 6 wk (end of study). None of the recruits developed the full syndrome of RSD during the study period. Whether the continued training, even though modified, helped to prevent this complication or the observed post-traumatic hypothermia has no relationship to RSD needs to be determined.

Whiplash in Australia: illness or injury?

OBJECTIVE

To provide a perspective on "whiplash" injury in Australia by examining conflicting evidence, which suggests on the one hand that the disorder is a culturally conditioned and legally sanctioned illness and on the other, that it is an occult injury which can cause chronic pain.

DATA SOURCES

The published English language literature derived from MEDLINE covering epidemiological, pathogenetic and psychological aspects of "whiplash" injury, post-traumatic stress disorder, abnormal illness behaviour and iatrogenicity; the Australian legal literature; the printed news media; the Transport Accident Commission of Victoria and the State Government Insurance Commission of South Australia.

DATA SYNTHESIS AND CONCLUSIONS

Comparative studies suggest that "whiplash" is an illness reinforced by legal and social sanction. Evidence from Victoria indicates that the reported incidence of "whiplash" can be reduced by minor legislative change. Occult injury to cervical intervertebral discs, vertebral end plates and cervical zygapophysial joints may be responsible for "whiplash" symptoms in some who are involved in motor vehicle accidents. This is likely to be confined to a small number of those involved in unexpected rear-end collisions.

Thermography--wither the niche?

OBJECTIVE

To review the current medical and legal status and future directions of thermography.

DATA SOURCES

Medical and legal journals published from 1956 onwards; report of the United States Office of Health Technology Assessment and personal communication with the author of that report; report of Australian Institute of Health and personal communication with the author; personal communication with members of the Therapeutics and Technology Assessment Subcommittee, American College of Neurology and with the Chairperson of the Commission of Technology Assessment and Efficacy Studies, American College of Radiology.

STUDY SELECTION

Reports and position statements of statutory bodies and specialist colleges in the United States and Australia; legal judgments in both these countries.

CONCLUSION

Acceptance of thermography is largely confined to those who use it and profit by its use.