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Temperature Profile of Radiofrequency Probe Applicationin Wrist Arthroscopy: Monopolar Versus Bipolar

Michaela Huber, M.D., Christoph Eder, Michael Mueller, M.D., Richard Kujat, Ph.D.,Christina Roll, M.D., Ph.D., Michael Nerlich, M.D., Ph.D., Lukas Prantl, M.D., Ph.D.,

and Sebastian Gehmert, M.D.

Purpose: The purpose of this study was to investigate the changes in temperature during wrist arthroscopy comparingmonopolar and bipolar radiofrequency energy (RFE). Methods: A standard wrist arthroscopy was performed on 14 armsof 7 cadavers without irrigation or with continuous irrigation with 0.9% saline solution and gravity-assisted outflowthrough an 18-gauge needle. We treated 7 wrists with a bipolar device (VAPR II with 2.3-mm side effect electrodes; DePuyMitek, Westwood, MA) and 7 wrists with a monopolar device (OPES Ablator for small joints, 45�; Arthrex, Naples, FL).The temperature was recorded simultaneously from 7 predefined anatomic landmarks. Results: We observed an increasein the temperature corresponding to the time of energy application. The highest measured peak temperatures were 52�C(monopolar) and 49.5�C (bipolar) without irrigation. Continuous irrigation led to a significant reduction in the temper-ature at the site of the energy application. The mean temperature decreased by 7�C for the monopolar system and 5�C forthe bipolar system when irrigation was used. For both radiofrequency devices, we found a decrease in the temperatureproportional to the distance of the sensors to the radiofrequency probe. Conclusions: Monopolar and bipolar RFE can besafely used in wrist arthroscopy if a continuous irrigation system is applied and the energy impulse does not exceed 5 to10 seconds. However, it should be used with great care to avoid local heat damage especially at the cartilage. ClinicalRelevance: This basic science study was performed to gain data concerning the temperature in wrist arthroscopy and tobroaden the knowledge about the risks when using RFE. Furthermore, we sought to control side effects of RFE by findingthe best applied form of RFE regarding duration and pulsation (monopolar/bipolar).

ver the last decade, small tools for radiofrequency

Oenergy (RFE) application have been developed,and RFE application is now widely used for tissueresection, tissue shrinkage, and coagulation inwrist jointarthroscopy.1,2 However, variable results have been re-ported regarding the safety of RFE in arthroscopy.Kaplan and Uribe3 indicated the safe use of bipolarcurrents over a period of 3 seconds for arthroscopy. Incontrast, Lu et al.4 found significant effects on cellsurvival.

From the Department of Trauma, Plastic & Hand Surgery, Universityedical Center Regensburg, Regensburg, Germany.The authors report that they have no conflicts of interest in the authorship

nd publication of this article.Received March 20, 2012; accepted November 2, 2012.Address correspondence to Michaela Huber, M.D., Department ofrauma, Plastic & Hand Surgery, University Medical Center Regensburg, Franz-sef-Strauss-Allee 11, 93053 Regensburg, Germany. E-mail: michaela1.uber@klinik.uni-regensburg.de� 2013 by the Arthroscopy Association of North America0749-8063/12182/$36.00http://dx.doi.org/10.1016/j.arthro.2012.11.006

Arthroscopy: The Journal of Arthroscopic and Related

The focus now turns specifically to cartilage damageafter the use of monopolar versus bipolar RFE. Initial invitro data showed that apoptosis and necrosis rates ofchondrocytes were higher when a bipolar device wasused comparedwith amonopolar device. Further studiesby Edwards et al.5,6 showed that when used for thermalchondroplasty, a bipolar device introduces deeper carti-laginous defects than a monopolar device.It is well documented that chondrocyte death is

associated with temperatures of above 50�C because ofan influx of calcium.7,8 Forty percent of chondrocytedeath occurs at a temperature of 55�C, with almost100% death occurring at 65�C.9 This is importantbecause chondrocytes are not able to respond withremodeling. However, the threshold temperature atwhich chondrocytes can recover from thermal injury ismuch lower than the temperatures reached by RFE.10

Further determinants of chondrocyte effect and in-jury include time of applied RFE and surface of thetreated cartilage. Recently, it was shown that RFE for15 seconds resulted in a smoother surface, accompaniedby a reduced chondrocyte death rate from a monopolardevice compared with a bipolar device.11 However,

Surgery, Vol 29, No 4 (April), 2013: pp 645-652 645

646 M. HUBER ET AL.

Caffey et al.12 reported substantial thermal damage tohuman cartilage with no significant difference betweenthese 2 devices in vitro.Available data regarding RFE in arthroscopic surgery

have mostly been obtained from knee and shoulderarthroscopy.13-16 An increasing number of studies showthat RFE applied in arthroscopy induces thermal injuriesin adjacent tissues, reported as burns, tendon ruptures,and axillary nerve injury.17-21 One study observed a 6%complication rate in wrist arthroscopy using RFE, result-ing in tendon ruptures and full-thickness skin burns.22

Thus far, no laboratory control trial has been per-formed to determine the use of small-joint RFE probesfor wrist arthroscopy. The importance of a wrist-specifictrial is to account for the specialized wrist anatomy.Different structures such as cartilage, bone, nerves,tendons, and ligaments are often in close proximity, only2 to 5 mm away. In addition, because of a lack of wrist-specific thermo-irrigation fluid management instru-ments, tissue temperatures with radiofrequency (RF)probes in wrist arthroscopy are widely unknown.To date, only 1 cadaveric study has investigated the

impact of using RFE devices on the wrist joint.23 Morestudies are required to determine the effect of RFE ontissue in the wrist and to develop effective protocols tominimize complications.Our purpose was to investigate and provide informa-

tion about fluid irrigation and RFE device differences.We hypothesize that a mean temperature increase willoccur with the duration of the applied energy and thatthere is a significant difference between the bipolar andmonopolar devices.

MethodsThe study protocol was reviewed and approved by the

Institutional Review Board of the University MedicalCenter of Regensburg, Regensburg, Germany. Weobtained 14 arms from 7 cadavers; written consent wasobtained from patients before death. The arms werestored at �20�C without any further fixation and were

only thawed to room temperature before the experimentwas started.Temperature probes containing platinum-chip

sensors (Pt 1000, TYP PCA, and 1.1505.10M; JUMOGmbH & Co KG, Fulda, Germany) were used for allexperiments, measuring 2 temperatures per second,with an accuracy of � 0.1�C. Eight probes were used intotal (Fig 1A). Probe 1 was used as a reference to detectthe temperature of the irrigation fluid at roomtemperature of 20�C. Six temperature probes were thensurgically implanted, by use of a 2.5� magnifying lensunder direct visualization, to the following locations onthe wrist: Probe 2 was inserted intra-articularly into theradial recess. Probe 3 was inserted into the scapholu-nate ligament. Probe 4 was inserted into a hole of2 mm, drilled dorsally subchondral in the center of thelunate fossa. Probe 5 was placed intra-articularly at thedistal radioulnar joint (DRUJ). Probe 6 was placedextra-articularly into the tendon sheath of the 4/5compartment. Probe 7 was implanted adjacent to theulnar nerve at the same level as the ulnocarpal jointextra-articularly. All of these probes were positioned bya minute skin incision followed by blunt dissectionthrough the capsular. Probes were fixed with a No. 4-0Prolene suture (Ethicon, Somerville, NJ), and the wristjoint capsular was closed.Thereafter the arms were fixed in the commercially

available Acumed Arc Wrist Tower (Acumed, Hillsboro,OR), and finger-traps and maximum distraction wereapplied (Fig 1B). The final probe, probe 8, was intra-articularly fixed by arthroscopy central in the midcarpaljoint.A standard wrist arthroscopy was then performed by

use of the No. 3-4 portal for the overview and the 6Rportal for the RF probe. To apply bipolar currency,VAPR II 2.3-mm side effect electrodes (DePuy Mitek,Westwood, MA) were used. A monopolar OPES Abla-tor for small joints (45�; Arthrex, Naples, FL) was usedfor all monopolar applications.All wrists were initially flushed with 0.9% sodium

chloride until a temperature of 20�C was reached by all

Fig 1. (A) Experimental setup showingsensor locations: 2, radial recess (rr); 3,scapholunate ligament (sl); 4, lunate fossa(fl); 5, DRUJ; 6, tendon sheath of 4/5compartment (4/5); 7, ulnar nerve (un);and 8, midcarpal joint (mc). (B) Speci-men with application of finger-traps andmaximum distraction.

Fig 2. Mean temperatures at 2, 5, 10, 15, and 30 seconds: bipolar device without irrigation (A), bipolar device with irrigation (B),monopolar device without irrigation (C), and monopolar device with irrigation (D). (SL, scapholunate.)

TEMPERATURE OF RFE APPLICATION IN WRIST 647

probes. Irrigation was applied at a pressure of 50 mm Hgwith an inflow rate of 50 mL/min. Gravity-assistedoutflow was achieved by an 18-gauge needle in the 6Uportal. The temperature was monitored and recorded byan 8-channel custom-built simultaneous measuringdevice.The bipolarRF probewasusedwith apower of 60W for

ablation without tissue contact, whereas the monopolarRF probe setting was 20 W for cut mode with tissuecontact on the lunate cartilage. The RF probe was placedinto the joint space centrally above the lunate fossa.Five different ablation times (2, 5, 10, 15 and 30

seconds) were used, and changes in temperature werethen recorded for all probes simultaneously. The wristwasflushed after each applied RFE until the temperaturedropped back down to 20�C on all implanted sensors.This procedure was performed on 7 wrists for themonopolar probe, with or without irrigation fluid, aswell as for the bipolar probe.Afterward, every wrist was dissected and the distance

between the location of the RF probe and the tempera-ture sensors was measured in millimeters. Probes were

stable in their fixed placement after dissection ofthe wrist. The retrieved measurements were then sortedin ascending order as follows: RFE for lunate fossa, sca-pholunate ligament, DRUJ, radial recess, midcarpaljoint, tendon sheath of 4/5 compartment, and ulnarnerve.Histograms and descriptive statistics were calculated

to determine distributions and detect outliers. P < .05was considered statistically significant. All statisticalanalyses were performed with the statistical softwarePASW Statistics 17 for Windows (SPSS, Chicago, IL).Because the underlying data were not normallydistributed, nonparametric tests were applied (1-sidedSpearman r coefficient, Kendall s coefficient, and2-tailed Mann-Whitney U test).

ResultsThe temperature decreased proportional to the distance

of the RF probe for the monopolar device, as well as forthe bipolar device, in the order specified: RFE to lunatefossa, scapholunate ligament, DRUJ, radial recess, mid-carpal joint, tendon sheath of 4/5 compartment, and

Table 1. Bipolar Device Without Irrigation

Mean Temperature � SD (�C)

0 s 2 s 5 s 10 s 15 s 30 s

Irrigation fluid 20.03 � 0.98 20.02 � 0.98 20.20 � 0.77 20.07 � 0.86 19.94 � 0.98 19.99 � 0.93Radial recess 22.02 � 1.27 22.19 � 1.41 25.07 � 6.26 25.04 � 7.65 24.42 � 5.40 26.88 � 6.71Scapholunate ligament 21.64 � 1.26 21.66 � 1.27 21.84 � 1.78 22.40 � 3.10 22.09 � 2.06 23.60 � 3.77Lunate fossa 21.9 � 1.43 22.69 � 1.20 24.93 � 1.40 29.24 � 5.65 31.27 � 6.39 35.18 � 5.89DRUJ 21.21 � 1.23 21.56 � 1.43 21.26 � 1.15 21.99 � 1.86 22.98 � 3.80 22.96 � 2.81Tendon sheath of 4/5 compartment 20.61 � 1.33 20.70 � 1.21 20.65 � 1.37 20.82 � 1.15 20.83 � 0.93 21.50 � 0.64Ulnar nerve 20.47 � 1.43 20.49 � 1.41 20.60 � 1.48 20.44 � 1.48 20.62 � 1.35 21.18 � 1.76Midcarpal joint 21.59 � 0.99 21.71 � 0.99 21.78 � 1.00 21.82 � 0.83 22.29 � 1.61 22.78 � 2.26

648 M. HUBER ET AL.

ulnar nerve. A Kendall s-b correlation test showeda positive correlation for the bipolar system with irriga-tion (0.81, P ¼ .005) and without irrigation (0.71,P¼ .012). In addition, similar correlationswere found forthemonopolar devicewith irrigation (0.81, P¼ .005) andwithout irrigation (0.9, P ¼ .002).Increases in temperature over 25�Cwere only detected

in the radial recess and in the lunate fossa for the bipolardevice. For all other measurement points (scapholunateligament, DRUJ, tendon sheath of 4/5 compartment,ulnar nerve, and midcarpal joint), the temperatureeither did not increase over time or did not reacha temperature of 25�C. When the bipolar RFE applica-tion was used, the highest temperature was measuredafter 30 seconds in the lunate fossa (35.18�C � 5.89�Cwithout irrigation and 31.78�C � 6.6�C with irrigation)(Fig 2A and 2B, Tables 1 and 2).The monopolar device showed a different tempera-

ture profile with a better cooling effect when flushingduring current flow. After 30 seconds, the temperaturein the lunate fossa reached 34.15�C � 6.27�C withoutirrigation and 27.11�C � 5.72�C with irrigation (Fig 2Cand 2D, Tables 3 and 4).We recorded noteworthy peak temperatures of

49.34�C (without irrigation) and 44.44�C (with irriga-tion) in the lunate fossa when using the bipolar system.In contrast, we detected highest temperatures of 51.84�C(without irrigation) and 39.84�C (with irrigation) in thelunate fossa for the monopolar system (Fig 3).Despite these findings, the differences in peak

temperatures between the monopolar and bipolar RFEapplications were not statistically significant (P ¼ .86

Table 2. Bipolar Device With Irrigation

0 s 2 s

Irrigation fluid 19.93 � 1.00 20.36 � 1.31Radial recess 21.74 � 0.97 22.33 � 1.72Scapholunate ligament 21.41 � 1.20 21.86 � 1.62Lunate fossa 21.86 � 1.06 23.16 � 1.60DRUJ 22.36 � 0.79 22.31 � 0.78Tendon sheath of 4/5 compartment 21.54 � 0.70 21.44 � 0.89Ulnar nerve 21.03 � 0.88 21.05 � 1.08Midcarpal joint 22.10 � 0.81 22.26 � 0.78

without irrigation and P ¼ .61 with irrigation).A significant decrease in maximum temperature wasachieved by irrigation for the monopolar system (P ¼.031), as well as for the bipolar system (P¼ .018) (Fig 3).Significant differences in the temperature profile at

different measurement points were present when wecompared both RFE systems. Significantly higher temper-atures were detected in the radial recess for the bipolarsystem, as well as the monopolar device, in the settingwithout irrigation (P ¼ .028). Higher temperatures werealso observed in the scapholunate ligament, the tendonsheath of the 4/5 compartment, and the ulnar nerve(P ¼ .028) when monopolar RFE was used. No statisticaldifferenceswere calculated at the remainingmeasurementpoints (lunate fossa, DRUJ, and midcarpal joint).A slightly higher mean temperature profile was

detected in the lunate fossa for the bipolar application.However, cooling by irrigation appeared to be moreefficient when the monopolar device was used (Fig 4).In addition, we compared the mean temperature

profile of the pulsed application with the continuousapplication for the monopolar and bipolar settings. Asshown in Fig 5, both pulsed RF application andcontinuous RF application show very similar tempera-ture profiles over the duration of 30 seconds.

DiscussionIn this article we report results from our study of the

effect of RFE on tissue temperature during wristarthroscopy. Significant amounts of heat are generatedthrough high-frequency alternating currents betweenthe tips of the RFE probe in a bipolar system and the tip

Mean Temperature � SD (�C)

5 s 10 s 15 s 30 s

19.78 � 0.85 20.37 � 1.40 20.09 � 1.31 20.37 � 1.5122.62 � 2.13 24.96 � 5.98 27.07 � 7.68 28.51 � 6.3722.27 � 2.01 22.41 � 2.43 23.08 � 2.63 25.04 � 5.0425.78 � 3.77 25.77 � 3.81 30.87 � 8.78 31.78 � 6.6022.07 � 1.08 22.38 � 0.42 22.24 � 0.91 22.61 � 1.3921.52 � 0.72 21.45 � 0.79 21.88 � 0.57 22.25 � 0.7821.64 � 1.95 21.32 � 0.94 21.58 � 1.61 21.82 � 1.6722.11 � 0.96 22.07 � 0.92 22.26 � 0.89 22.87 � 1.19

Table 3. Monopolar Device Without Irrigation

Mean Temperature � SD (�C)

0 s 2 s 5 s 10 s 15 s 30 s

Irrigation fluid 21.05 � 0.99 21.06 � 0.96 20.86 � 1.03 20.76 � 1.25 20.72 � 1.21 20.70 � 1.15Radial recess 21.64 � 1.16 22.14 � 1.71 22.33 � 2.08 21.98 � 1.92 22.47 � 2.25 22.38 � 2.06Scapholunate ligament 21.85 � 0.86 22.61 � 1.14 22.98 � 1.51 24.54 � 3.20 25.31 � 5.28 27.01 � 4.77Lunate fossa 21.55 � 1.07 22.62 � 2.26 26.33 � 6.18 26.82 � 6.40 28.32 � 5.03 34.15 � 6.27DRUJ 21.50 � 0.97 21.93 � 1.66 22.29 � 1.49 22.45 � 1.38 22.58 � 1.38 23.93 � 3.80Tendon sheath of 4/5 compartment 21.40 � 1.51 21.42 � 1.45 21.52 � 1.40 21.52 � 1.50 21.72 � 1.30 22.03 � 1.20Ulnar nerve 21.53 � 1.19 21.57 � 1.20 21.77 � 1.13 21.51 � 1.33 21.89 � 1.19 21.91 � 1.07Midcarpal joint 21.65 � 0.89 21.97 � 1.29 21.96 � 1.37 22.18 � 1.32 22.29 � 1.28 22.35 � 1.35

TEMPERATURE OF RFE APPLICATION IN WRIST 649

and surrounding tissue to the conducting electrode ina monopolar system.9,14,24,25 The thermal effect isdescribed by Joule’s law: Q¼ I2� R� t (where Q is heat,I is current, R is electrical resistance, and t is time). Thisshows the importance of tissue resistance and the time ofapplication. Another factor affecting the thermal effecton tissue is the distance between the probe and theconduction current.14

Edwards et al. have been conducting different studiesproviding basic knowledge about RFE. In 2002 theirgroup raised concerns about using RFE for chondroplastyand recommended limited application for bipolar RFEapplication in thermal chondroplasty especially in regionswhere the chondral matrix is 3 mm or less.9 In addition,their statement was critical for monopolar devices.In our study the mean tissue temperature increased

with the duration of the RFE application, and therewas a significant difference between the bipolar andmonopolar RFE systems concerning the heat expan-sion, which could be explained by the different func-tions of bipolar and monopolar systems.Similar results concerning the difference in the

monopolar and bipolar systems had been achieved byformer studies, whereas Edwards et al.5 found a signif-icantly lower temperature for the monopolar systemcompared with the bipolar system. On the other hand,we had a higher peak temperature for the monopolarsystem than that for the bipolar system without irriga-tion, but it was not statistically significant.Previously, in a series of 47 patients undergoing wrist

arthroscopy, including RFE, Pell and Uhl22 reporteda 6% complication rate including tendon ruptures and

Table 4. Monopolar Device With Irrigation

0 s 2 s

Irrigation fluid 20.63 � 1.17 20.59 � 1.19Radial recess 21.26 � 0.80 21.61 � 1.15Scapholunate ligament 22.16 � 0.59 22.69 � 1.11Lunate fossa 21.72 � 0.56 22.23 � 1.35DRUJ 21.80 � 0.54 22.14 � 0.73Tendon sheath of 4/5 compartment 21.40 � 0.75 21.46 � 0.81Ulnar nerve 21.29 � 0.36 21.62 � 0.84Midcarpal joint 21.88 � 0.52 22.24 � 0.76

full-thickness skin burn. Other reports in the literatureon wrist arthroscopy showed additional complications.For example, in a case study of 20 patients with trian-gular fibrocartilage complex tears using RFE, the authorsreported a chondral lesion of the lunate in 1 case, whichwas only detected during repeat arthroscopy and hadnot been noted during the first arthroscopy.1 We placedseveral probes at anatomic structures to detect a risk ofhigh temperature when using RFE. The temperature atthe tendon sheath of the 4/5 compartment and at theulnar nerve did not exceed 25�C.Sotereanos et al.23 provided the first cadaveric study

dealing with RFE in wrist arthroscopy. They useda bipolar system and measured the temperature in theradiocarpal joint near the 1/2 portal and 6U portal andon the outflow. A significantly lower temperature wasachieved with the use of an outflow portal.The measured temperature depends on the distance of

the electrode to the tissue, so the temperature decreasedwith the distance from the RF probe to the temperatureprobe. Using a central application in the wrist and thebipolar system with no contact with the tissue, weobserved a maximum temperature beyond 50�C ata distance from the probe tip of around 3 to 5 mm. Witha continuous application of irrigation fluid, the temper-ature could be reduced but was still 40�C to 46�C at itspeak, high enough to damage the cartilage. We observedthat the irrigation fluid has a higher influence ontemperature when using the monopolar device ratherthan the bipolar device. This might be a result of thedifferent functions between monopolar and bipolarsystems, as explained earlier.

Mean Temperature � SD (�C)

5 s 10 s 15 s 30 s

20.68 � 1.14 20.76 � 1.21 20.89 � 1.27 20.90 � 1.2221.63 � 1.47 21.73 � 1.55 21.92 � 1.64 22.40 � 1.8822.78 � 0.96 23.15 � 0.84 25.00 � 2.77 26.09 � 2.2222.61 � 1.22 24.84 � 4.35 27.11 � 5.72 26.91 � 2.6022.32 � 1.06 22.47 � 1.03 22.64 � 1.58 22.96 � 1.6721.76 � 1.08 21.85 � 1.23 21.96 � 1.38 22.44 � 1.7621.67 � 0.91 21.69 � 0.92 21.75 � 0.99 21.78 � 1.0222.26 � 0.89 22.25 � 0.92 22.27 � 1.01 22.62 � 1.33

Fig 3. Peak temperatures after central RF application in radiocarpal joint. (SL, scapholunate; w/o, without.)

650 M. HUBER ET AL.

In contrast to the study of Zoric et al.,26 our studyshowed that we were not able to lower the temperatureto a safe level. This might be because no controlledoutflow system is available during wrist arthroscopy.Cartilage damage can occur with temperatures over45�C to 55�C to full-thickness apoptosis.27,28

In our study the baseline temperature was 20�Cinstead of the body temperature, similar to the study ofSotereanos et al.23 Assuming that the heat capacity ofthe tissue is constant in this small range of tempera-tures, the increase in temperature can be assumed to beindependent of the baseline temperature. We alsosuggest that blood flow can be disregarded, becausea tourniquet is generally used. Because the bodytemperature is 33�C to 35�C in the extremities, the peak

Fig 4. Comparison of mean temperatures at 2, 5, 10, 15, and30 seconds in lunate fossa. (w/o, without.)

temperature might be up to 10�C higher than what wasmeasured in our experiment.Manufacturers have produced various devices with

different settings, which cannot be compared with eachother. Given the complex structure of the wrist with itsclose proximity of tendons, nerves, ligaments, andcartilage, it is remarkable that there have been so fewstudies on the temperature changes in the wrist duringarthroscopic procedures with RFE.To date, available data from published studies have

not taken variables that are specific to the wrist intoaccount. These variables include the smaller volume ofthe wrist joint, the closeness of the different structures,and the thin cartilage layer of 0.7 to 1.2 mm.29 Ourstudy seeks to fill this gap and provide important dataon the impact of RFE on tissue temperature. There areseveral additional variables that may influence theresults, such as other irrigation fluids, irrigationtemperature, and controlled outflow. In this context thestudy from Lu et al.30 is very intriguing because theyobserved less chondrocyte death when using a temper-ature of 37�C for the irrigation fluid compared with22�C using a monopolar system.

LimitationsThere are many parameters that have to be evaluated

to use RFE in wrist arthroscopy safely. Further studiesare required to understand the correlation between thein vivo and vitro results regarding clinical application.One important future development might be a suffi-ciently reproducible irrigation management systemsimilar to the systems already used in arthroscopy ofother joints; the introduction of temperature feedbackunits for small joint setups would also be helpful. Thelimitation of this study is the small number of

Fig 5. Comparison of single-shot energy application at 2, 5, 10, 15, and 30 seconds versus continuous energy application overa period of 30 seconds.

TEMPERATURE OF RFE APPLICATION IN WRIST 651

specimens. We did not perform a power analysis beforethis study because of data from similar studies using 8 to10 cadavers for arthroscopic investigations of cadavers.23,26 The experimental setup cannot be compared withwrist arthroscopy on living humans because bodytemperature is between 36�C and 37�C. A tourniquet iscommonly used, which lowers the temperature of thelimb.31,32 In addition, arthroscopy is usually performedwith irrigation fluid at room temperature. However,irrigation fluid with temperatures different from 37�Cor limb cooling before surgery can alter results.30

ConclusionsMonopolar and bipolar RFE can be safely used in

wrist arthroscopy if a continuous irrigation system isapplied and the energy impulse does not exceed 5 to 10seconds. However, it should be used with great care toavoid local heat damage especially at the cartilage.

AcknowledgmentThe authors thank Dr Clarence Kerrison, Department

of Medicine, University of Otago, Dunedin, New Zea-land, for his valuable support and peer review of themanuscript.

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