An investigation of the relationship between thermal imaging and digital thermometer testing at the knee

Abstract

U n c o r r e c t e d A u t h o r P r o o f BACKGROUND:A number of research papers and theoretical clinical models summarising how temperature of the skin over the knee may be altered according to different pathological processes have been published. Thermal imaging (TI) is generally regarded as the 'Gold' or 'reference' standard for measuring skin temperature, however this technology is not widely accessible to most musculoskeletal physiotherapists working in clinical environments. This is largely due to the time required for analysis of the thermal images and the high cost of the equipment. A digital thermometer (DT) is portable with a convenient display of results which could offer an inexpensive substitute. PURPOSE:The aim of this study was to determine the interchangeability between thermal imaging and a digital thermometer, using Bland-Altman limits of agreement, to determine skin temperature differences between right and left knees. 16METHODS: Seventy-one healthy participants in the age group of 8 to 40 participated in the study. Data were collected in two phases. The first phase was as part of a public engagement event at the Lancashire Science Festival where school children were invited to learn about science. The second phase of data collection took place as part of a PhD study where staff and students at the university were recruited via electronic advert and posters displayed around the campus. All subjects were free from lower back or lower limb problems and had not had any previous lower limb surgery. RESULTS:Matched paired t tests showed no significant difference between temperature difference between right and left using DT and TI (t = 1.41, df = 69, P = 0.08). The DT and TI were interchangeable to measure knee skin temperature difference with a limit of agreement of -0.64 and 0.75; this limit of agreement is acceptable based on previous literature where skin temperature differences between affected and non-affected knees are equal to or greater than 1 • C. CONCLUSION: This study concludes that an inexpensive handheld digital thermometer shows acceptable agreement with a thermal imaging camera. Clinically a handheld digital thermometer has the potential to play an important role in the localized assessment of skin temperature in physiotherapy and can offer an inexpensive substitute to thermal imaging; due to the massive difference in cost it is worth considering the adoption of digital thermometry in routine musculoskeletal physiotherapy practice.

Hot and cold knees: exploring differences in patella skin temperature in patients with patellofemoral pain

“…The healthy volunteer study (normative dataset) recruited 71 participants without back or lower limb problems and without a history of knee surgery. This healthy volunteer study was a validation study of the digital thermometer used in all three PFP studies against thermal imaging measurements, and its methods are reported in detail in Erande et al [28].…”

“…Of the three studies undertaken in newly diagnosed PFP patients, two were undertaken in the United Kingdom (UK): London [28] and the UK wide TIPPs (Targeted Interventions for Patellofemoral Pain study) [15], and one in Turkey [29]. All three studies used the same participant eligibility criteria used in previous studies [30,31].…”

“…All relevant institutional, health department and governmental approvals were in place prior to data collection at each site. Information on approvals can be found in Erande et al [28] for the thermometer validation study and Selfe et al [15] for the TIPPs study. Ethical approval for the London study was obtained from the Regional ethics committee (REC 14/10/1388) and local university ethics committee (STEMH 274).…”

“…A limitation of these observations for clinical practice is the high cost of infra-red thermal imaging cameras which inhibits there use in routine clinical environments. However, a low-cost method of assessment of Tsk at the knee using a hand-held digital thermometer has recently been validated against a thermal imaging camera [28].…”