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Physical Therapy in Sport 8 (2007) 153158

Case study

Thermal imaging of an ice burn over the patella following clinicallyrelevant cryotherapy application during a clinical research study

James Selfe, Natalie Hardaker , Jonathan Whitaker, Colin HayesDepartment of Allied Health Professions, University of Central Lancashire, BB114 Brook Building, Preston PR1 2HE, UK

Received 28 November 2006; received in revised form 6 March 2007; accepted 25 April 2007

Abstract

Objectives: The use of cryotherapy in soft tissue injury is still largely based on anecdotal rather than empirical evidence. Theobjective of this case report is to present thermal imaging data from a mild ice burn sustained during a clinical research project.Design: Case report.Case description: A 43-year-old male participant recruited to take part in an ongoing cryotherapy research project sustained a mildice burn, resulting in visible blanching of the skin over the affected area and a transient burning sensation. The burn occurredunexpectedly during a tightly controlled experimental procedure, employing protocol from current clinical practice. Threeparticipants had already successfully completed the study with no adverse reactions when the ice burn occurred.Outcome measures: Outcome measures were; patella skin-fold, modality temperature pre and post application, baseline thermalimage, and thermal imaging data over the knee at a rate of 1 image min 1 during a 25-min re-warming period.Results: The participant recorded a patella skin-fold of just 7 mm. Baseline skin surface temperature was 29.4 1 C. Skin surfacetemperature ( T sk ) decreased by 17.9 1 C following cold application. During the 25-min re-warming period T sk increased 11.8 1 C.Conclusions: Twenty minutes of cryotherapy application may be too long over an anatomically bony area. Clinicians shouldconsider thermal gradient as part of their clinical decision making process, which would be inuenced by increased ambienttemperature, pathology, and also lower modality temperature.r 2007 Elsevier Ltd. All rights reserved.

Keywords: Cryotherapy; Thermal imaging; Patella; Ice burn

1. Introduction

Despite its long history of recorded use in soft tissueinjury management, cryotherapy is still largely based onanecdotal rather than empirical evidence ( Bleakley,

McDonough, & MacAuley, 2006 ). Cryotherapy isessentially the lowering of tissue temperature to achievea therapeutic effect, and is considered a simple, well-established treatment modality for the immediate care of acute soft tissue injuries and the reduction of pain

(Bleakley et al., 2006 ; Kerr, Daley, Booth, & Stark,1999 ). Despite the development of clinical guidelines(Kerr et al., 1999 ) existing literature is largely incon-clusive. Fundamental treatment protocols remain am-biguous with no denitive optimum treatment time or

modality being promoted as the gold standard. Re-cently, the potential complication of ice burn inducedthrough cryotherapy has been highlighted ( Cuthill &Cuthill, 2006 ). This paper presents a case report of amild ice burn resulting in visible blanching of the skinand a time limited altered cutaneous sensation overthe affected area. The burn occurred unexpectedlyduring a tightly controlled experimental procedure,employing a protocol widely used in current clinicalpractice ( Kerr et al., 1999 ).

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1466-853X/$ - see front matter r 2007 Elsevier Ltd. All rights reserved.doi: 10.1016/j.ptsp.2007.04.001

Corresponding author. Tel.: +441772 895473;fax: +441772 894494.

E-mail addresses: jselfe1@uclan.ac.uk (J. Selfe) ,njhardaker@uclan.ac.uk (N. Hardaker) , jmwhittaker1@uclan.ac.uk(J. Whitaker) , CHayes1@uclan.ac.uk (C. Hayes) .

http://www.elsevier.com/locate/yptsphttp://localhost/var/www/apps/conversion/tmp/scratch_8/dx.doi.org/10.1016/j.ptsp.2007.04.001mailto:jselfe1@uclan.ac.ukmailto:njhardaker@uclan.ac.ukmailto:jmwhittaker1@uclan.ac.ukmailto:jmwhittaker1@uclan.ac.ukmailto:CHayes1@uclan.ac.ukmailto:CHayes1@uclan.ac.ukmailto:jmwhittaker1@uclan.ac.ukmailto:jmwhittaker1@uclan.ac.ukmailto:njhardaker@uclan.ac.ukmailto:jselfe1@uclan.ac.ukhttp://localhost/var/www/apps/conversion/tmp/scratch_8/dx.doi.org/10.1016/j.ptsp.2007.04.001http://www.elsevier.com/locate/yptsp

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Non-contact, digital, infrared thermal imaging (TI)cameras are a valid and reliable tool for measuring skinsurface temperature ( T sk ); nothing radiates to, ortouches the body ( Owens, Hart, Donofrio, Haralam-bous, & Mierzejewski, 2004 ; Pochczevsky, Abernathy, &Borten, 1986 ; Sherman, Woerman, & Karstetter, 1996).

Previous applications of non-contact TI cameras ( DeSilva, Kyle, Hazelman, Salisbury, Page Thomas, &Wraight, 1986 ; Devereaux, Parr, Lachmann, PageThomas, & Hazleman, 1986 ; Sherman et al., 1996)highlight their capacity to track dynamic changes in T sk .Although the skin is rarely the target tissue duringcryotherapy, due to the supercial nature of thecryotherapy application it is unavoidably the tissue thatis cooled rst. TI cameras are therefore considered anideal tool for monitoring recovery of T sk followingcryotherapy application. TI cameras are advantageousas they allow temperature measurement over an area,and data analysis facilitated by computer softwareallows extraction of relevant temperature data from aspecic region of interest (ROI) within the image.Data from a TI camera which would not normallybe available were recorded and are presented here asthey are considered to be of signicant interest toclinicians.

2. Background

The study is part of an ongoing programme of

research investigating the efciency of differentcryotherapy modalities applied to the knee. Targetrecruitment for this study was 23 healthy maleparticipants. Participants were required to attend fourtesting sessions, one for each of the four modalitiestested. Prior to each testing session participants wereasked to conrm their eligibility for the study to ensureno contraindications had arisen since initial consent orthe previous testing session. Exclusion criteria were:referred pain to lower limb from spinal, pelvic, or hip joints; pregnancy; increased temperature of the knee joint; inammation or injury to the knee joint;psychological problems; systemic disease; sensory de-cit; cold intolerance/hypersensitivity; and skin lesions.The participant screening process had been usedsuccessfully in two previous studies and no incidentsof adverse reactions were recorded in these previousinvestigations ( Karki, Karppi, Ekberg, & Selfe, 2004 ;Kennet, Hardaker, Hobbs, & Selfe, 2006 ). The studyconformed to the World Medical Association Declara-tion of Helsinki (1964) and was approved by theinstitutional ethics committee. When the ice burnoccurred, three healthy male participants had alreadysuccessfully completed the study with no adversereaction.

2.1. Cryotherapy application

Temperature data were collected using a digitalinfrared non-contact TI camera (Flir Systems, Ther-movision A40M, Danderyd, Sweden). A period of 1week was allowed between each testing session. Prior

to each session participants were requested toadhere to the following standardised TI data collectionprotocol: no alcohol consumption 24 h before thesession; no smoking or caffeine ingestion; and noparticipation in intense physical activity 2 h beforethe session ( Davidson & Bass, 1979 ; Owens et al.,2004 ; Pochczevsky et al., 1986 ). Participants removedshoes and socks from both feet and were seated, in astable and relaxed position with knee angle standardisedto 45 1 . Exposed lower limbs were given a 15-minacclimatisation period away from heat sunlight anddraughts to allow stabilisation to room tempera-ture. Four small thermally inert markers were placedon known anatomical landmarks in order to denethe ROI for later computer analyses. Locations of these markers were the base of the patella, the me-dial border of patella tendon margin at the tibiofe-moral joint line level, the lateral border of patellatendon margin at the tibiofemoral joint line level,and the tibial tubercle ( Selfe, Hardaker, Thewlis, &Karki, 2006 ).

Each cryotherapy modality was applied to the rightknee in all subjects with the left knee serving as thecontrol. Prior to testing, the lower limb was examined toensure absence of skin wounds, lesions, or rashes.

Thermal sensation testing was carried out over the localarea, in accordance with the PRICE guidelines ( Kerret al., 1999 ); touching the knee with a warm test tubeand a cold test tube and asking the participant todifferentiate the contrasting temperatures.

A baseline TI of both knees was taken prior tocryotherapy application. The cryotherapy modalitiestested were:

1. Three hundred grams of crushed ice in a plastic bag(CI).

2. Gelpack (GP) (BSN Medical Physiopack reusablepack, Vibraye, France).

3. Arctic Flow (AF) (DonJoy, Surrey, England).4. Ice Man (IM) (DonJoy, Surrey, England).

A thermal image of each modality was takenimmediately pre and post application to record thetemperature of the modality.

Application time for all modalities was 20 min; aclinically relevant application time ( Kerr et al., 1999 ).Thermal images of the knee were collected at a samplingrate of 1 imagemin 1 during a 25-min re-warmingperiod.

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3. Case report

A 43-year-old healthy male subject volunteered totake part in this study. The subject provided writteninformed consent to participate, as well as writtenconrmation of eligibility for this type of study. It is

noteworthy that the participant was well known to theresearch team having taken part in a number of previouscryotherapy studies without experiencing any adversereactions and was able to clearly differentiate warmfrom cold on thermal sensation testing. In accordancewith the protocol the GP was applied to the partici-pants right knee. On application the subject reportedthat the GP felt very cold, but he did not complain of pain. The participant was reminded that the GP couldbe removed at any time, and the experiment terminated,but he declined and was happy to continue. During theapplication the participant reported that the intensity of the cold sensation decreased and overall it felt morecomfortable. Upon removal of the GP it was clear thatthe participant had sustained an adverse reaction. Thiswas manifested by the appearance of a well denedblanched area of skin over the base of the patella(4cm 3 cm). This blanched area was surrounded by azone of erythema, covering the area of skin that hadbeen in contact with the GP. Although immediatelyobvious that an adverse reaction had occurred, theparticipant volunteered to continue with the collectionof TI data over the 25-min re-warming period. Thesedata are represented in Fig. 1 , with a comparison to asubject who responded normally, and thermal images

are presented in Fig. 2 . Following the experiment theparticipant returned to work (desk-based job). Duringthe course of the next 3 h, the previously blanched areahad become red and hot, and at this point a digitalphotograph was taken of the knee ( Fig. 3 ). The reactionthat had developed over the 3 h following the experi-ment then began to subside. Seven hours following theexperiment the sensation had returned to normal, whilethe redness although decreased, still remained. Theparticipant reported a deep aching sensation in the kneethat night in bed, however, the following day the skin

colour and sensation had returned to normal. Theresearch team remained in regular contact with theparticipant after this episode, and no further problemswere reported.

3.1. Ice burn data

Quantication of thermal images was facilitated inThermacam Researcher 2.8 (Flir systems, Danderyd,Sweden) computer software, and processed in MicrosoftExcel. The mean temperature of the ROI was calculatedfrom each image using the polygon tool within thecomputer software.

4. Discussion

The participant in this case report had no knownpathology, however, he did demonstrate a slightlyelevated baseline T sk (29.4 1 C) when compared to theother participants who showed no adverse reaction tothe cooling (29.0 1 C). Initially this would create a steepertemperature gradient between the T sk and the modality.This difference of 0.4 1 C may be of some relevance.Previous work in the clinical application of TI wouldindicate that this is approaching a clinically signicanttemperature difference (normally considered to be4 0.5 1 C (Davidson & Bass, 1979 , De Silva et al.,1986 ; Devereaux et al., 1986 ). As such, this elevated T sk may have contributed to the adverse reaction.

Immediately following removal of the GP, T sk

demonstrated a decrease of 91

C in the normallyresponding participant. This value was almost doubledin the participant in this case report, displaying a T sk decrease of 17.9 1 C. Yet, during the 25-min re-warmingperiod T sk in the normal participant increased by 4.8 1 C,in contrast the participant in this case report whodemonstrated T sk increase of 11.8 1 C, more than twicethat of the normal participant ( Fig. 1 ). Again thisincreased transfer of temperature may be attributable tothe steeper temperature gradient existing between T sk and ambient room temperature, allowing greater op-portunity for heat energy transfer. Analysis of thethermal images following the incident highlighted apreapplication temperature for the GP of 17 1 C. It ispertinent to recognise the steep temperature gradientcreated between the modality and T sk , due to thisextremely low preapplication temperature, thus creatinga difference of 43 1 C. A temperature gradient this steepmay be considered to be potentially dangerous; thisreport would tend to conrm this. However, anincreased rate of re-warming continued to the end of the re-warming period ( Fig. 1 ), possibly indicating thatthere is another source of heat to the local areacontributing to the increased re-warming. It is now wellaccepted within the literature that TI cameras provide

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-9

-4

1

6

11

0 0-15 25

Time (min)

T e m p e r a

t u r e c

h a n g e

( C )

Iceburn Normal

Fig. 1. Comparison of T sk rate of re-warming in normal participantsand the participant sustaining the ice burn.

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T sk which is largely inuenced by and can be considereda reection of local blood ow ( Davidson & Bass, 1979 ,De Silva et al., 1986 ; Devereaux et al., 1986 ). In thiscase, an increase in local blood ow may be due to thebodys homoeostatic response or part of an inamma-tory response as a result of the cold-induced tissuedamage. Increased blood ow to the area would beconsistent with the thermal hot spot observed on theskin surface area over the base of the patella on thethermal images in Fig. 2 . Further investigation isrequired to conrm this.

As previously stated, it is very rare to collect data suchas these which highlight rapid heating of the local areaas an adverse response to supercial cooling. Cuthill andCuthill (2006) in their report of a partial thickness iceburn following cryotheraphy listed four other similarreports in the literature Table 1 . We were able to ndadditional report in ( Fye and Denkler, 1993 ). It is

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Fig. 3. Digital image of the ice burn at 3 h following gel packapplication.

Fig. 2. Thermal images of ice burn and normal response to cooling by gel pack.

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important to note that these reports are associated withdamage to the skin and underlying soft tissues, whereasthere is an independent group of reports specic tocryotherapy associated nerve damage. These reports arenot included in this paper.

Application time is another important factor to considerin cryotherapy. Existing literature is inconclusive andcurrently fails to dene an optimum safe application time.As most of the adverse incidents from earlier reportsoccurred with application times of 30 min or more, theapplication time of 20 min in this case report is thereforeunlikely to be the primary cause of the ice burn, and isadvocated as a clinically relevant application time ( Kerret al., 1999 ). Current guidelines recommend 30 min as themaximum safe duration of cryotherapy ( Kerr et al., 1999 ),yet more than 92% of physiotherapists responding to asurvey around this topic ( Cuthill & Cuthill, 2006 ) reportedusing durations of 20min or less, based on clinicalexperience of patient tolerance.

As previously stated, in the current case reportapplication time is unlikely to be the primary cause of the ice burn. The composition of the anatomical area isthought to be a contributory factor. Karki et al. (2003)highlighted the insulating effect of adipose tissue whenreporting T sk over the knee, where females who had higherlevels of adipose tissue compared to males, consistentlyhad warmer knees. The participant in this case report hada patella skin-fold measurement of just 7 mm, in contrastto the other participants who demonstrated a range of 10 13 mm. This highlights another parameter for clinicians toconsider when applying cryotherapy.

The etiology of the adverse incident reported here istherefore likely to be multi-factorial. Clinically this is of great importance as it has to be remembered that thiscase was in a healthy volunteer participant who had nopathology and only a slightly elevated T sk .

Patients presenting with acute inammation arelikely to have increased T sk , consequently creating asteeper temperature gradient, between the skin andthe cryotherapy modality, magnifying the effects pre-sented in this case report. More than 50% of thephysiotherapists responding to a survey reportedincidence of cold-induced injury ( Cuthill & Cuthill,2006 ), perhaps highlighting that currently clinicians

have poor understanding of the effects of cryotherapyand its possible dangers, and safe protocols.

Previously, Merrick, Jutte, and Smith (2003) and Kennetet al. 2006 highlighted that GPs consistently produced thesteepest temperature gradients, but were least effective inachieving a clinically relevant cooling effect.

An elevated T sk may be present in a patient presentingwith an inammatory response consistent with an acute joint injury. Much of the existing cryotherapy research hasbeen carried out on normal healthy participants high-lighting that clinicians should have increased awareness of steeper temperature gradients and increased risk of iceburn in the patient presenting with an inammatoryresponse. A steeper temperature gradient results in adecreased temperature transfer time, thus suggestive of aneed to decrease cryotherapy application time.

5. Conclusion

In view of the incident reported in this paper, we haveceased experimental work using gel packs. This incidenthas highlighted parameters that we would advise cliniciansto consider in their clinical decision making process; thepre-application temperature of cryotherapy modalitiesrelative to T sk i.e. thermal gradient, adiposity, and alsocomposition of the anatomical area. It is also noteworthythat application of cryotherapy in particularly warmsurroundings may also inuence initial temperaturegradient. Thus, ambient temperature should be considered.As this can be difcult to control in the clinical/athletic

environment, the modality application should be alteredaccordingly. Current guidelines are based on existingcryotherapy literature, and may over-estimate applicationtime. Further investigation of this area is required.

Conict of interest

The authors conrm that there was no conict of interest involved with this work.

Ethical approaval

The study received ethical approval from the Facultyof Health research ethics committee, University of Central Lancashire (uclan), Preston, England, it alsoconformed to the World Medical Association Declara-tion of Helsinki (1964).

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Bleakley, C. M., McDonough, S. M., & MacAuley, D. C. (2006).Cryotherapy for acute ankle sprains: A randomised controlledstudy of two different icing protocols. British Journal of SportsMedicine , 40 , 706709.

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Table 1Previous reports of soft tissue ice burn or frostbite injury

Author Modality

Cipallaro (1992) Reusable cold compressFye and Denkler (1993) Ice pack (16h per day 4 2 months)Quist et al. (1996) Ice compressesO Toole and Rayatt (1999) Ice packGraham and Stevenson (2000) Frozen chips (40 min)Cuthill and Cuthill (2006) Reusable gel pack (30 min)

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